/**
 * @file tree_data.c
 * @author Radek Krejci <rkrejci@cesnet.cz>
 * @brief Data tree functions
 *
 * Copyright (c) 2015 - 2020 CESNET, z.s.p.o.
 *
 * This source code is licensed under BSD 3-Clause License (the "License").
 * You may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://opensource.org/licenses/BSD-3-Clause
 */

#define _GNU_SOURCE

#include "tree_data.h"

#include <assert.h>
#include <ctype.h>
#include <inttypes.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "common.h"
#include "compat.h"
#include "context.h"
#include "dict.h"
#include "diff.h"
#include "hash_table.h"
#include "in.h"
#include "in_internal.h"
#include "log.h"
#include "parser_data.h"
#include "parser_internal.h"
#include "path.h"
#include "plugins.h"
#include "plugins_exts/metadata.h"
#include "plugins_internal.h"
#include "plugins_types.h"
#include "set.h"
#include "tree.h"
#include "tree_data_internal.h"
#include "tree_edit.h"
#include "tree_schema.h"
#include "tree_schema_internal.h"
#include "validation.h"
#include "xml.h"
#include "xpath.h"

static LYD_FORMAT
lyd_parse_get_format(const struct ly_in *in, LYD_FORMAT format)
{
    if (!format && (in->type == LY_IN_FILEPATH)) {
        /* unknown format - try to detect it from filename's suffix */
        const char *path = in->method.fpath.filepath;
        size_t len = strlen(path);

        /* ignore trailing whitespaces */
        for ( ; len > 0 && isspace(path[len - 1]); len--) {}

        if ((len >= LY_XML_SUFFIX_LEN + 1) &&
                !strncmp(&path[len - LY_XML_SUFFIX_LEN], LY_XML_SUFFIX, LY_XML_SUFFIX_LEN)) {
            format = LYD_XML;
        } else if ((len >= LY_JSON_SUFFIX_LEN + 1) &&
                !strncmp(&path[len - LY_JSON_SUFFIX_LEN], LY_JSON_SUFFIX, LY_JSON_SUFFIX_LEN)) {
            format = LYD_JSON;
        } else if ((len >= LY_LYB_SUFFIX_LEN + 1) &&
                !strncmp(&path[len - LY_LYB_SUFFIX_LEN], LY_LYB_SUFFIX, LY_LYB_SUFFIX_LEN)) {
            format = LYD_LYB;
        } /* else still unknown */
    }

    return format;
}

/**
 * @brief Parse YANG data into a data tree.
 *
 * @param[in] ctx libyang context.
 * @param[in] ext Optional extenion instance to parse data following the schema tree specified in the extension instance
 * @param[in] parent Parent to connect the parsed nodes to, if any.
 * @param[in,out] first_p Pointer to the first top-level parsed node, used only if @p parent is NULL.
 * @param[in] in Input handle to read the input from.
 * @param[in] format Expected format of the data in @p in.
 * @param[in] parse_opts Options for parser.
 * @param[in] val_opts Options for validation.
 * @param[out] op Optional pointer to the parsed operation, if any.
 * @return LY_ERR value.
 */
static LY_ERR
lyd_parse(const struct ly_ctx *ctx, const struct lysc_ext_instance *ext, struct lyd_node *parent, struct lyd_node **first_p,
        struct ly_in *in, LYD_FORMAT format, uint32_t parse_opts, uint32_t val_opts, struct lyd_node **op)
{
    LY_ERR rc = LY_SUCCESS;
    struct lyd_ctx *lydctx = NULL;
    struct ly_set parsed = {0};
    struct lyd_node *first;
    uint32_t i;
    ly_bool subtree_sibling = 0;

    assert(ctx && (parent || first_p));

    format = lyd_parse_get_format(in, format);
    if (first_p) {
        *first_p = NULL;
    }

    /* remember input position */
    in->func_start = in->current;

    /* parse the data */
    switch (format) {
    case LYD_XML:
        rc = lyd_parse_xml(ctx, ext, parent, first_p, in, parse_opts, val_opts, LYD_TYPE_DATA_YANG, NULL, &parsed,
                &subtree_sibling, &lydctx);
        break;
    case LYD_JSON:
        rc = lyd_parse_json(ctx, ext, parent, first_p, in, parse_opts, val_opts, LYD_TYPE_DATA_YANG, &parsed,
                &subtree_sibling, &lydctx);
        break;
    case LYD_LYB:
        rc = lyd_parse_lyb(ctx, ext, parent, first_p, in, parse_opts, val_opts, LYD_TYPE_DATA_YANG, &parsed,
                &subtree_sibling, &lydctx);
        break;
    case LYD_UNKNOWN:
        LOGARG(ctx, format);
        rc = LY_EINVAL;
        break;
    }
    LY_CHECK_GOTO(rc, cleanup);

    if (parent) {
        /* get first top-level sibling */
        for (first = parent; first->parent; first = lyd_parent(first)) {}
        first = lyd_first_sibling(first);
        first_p = &first;
    }

    if (!(parse_opts & LYD_PARSE_ONLY)) {
        /* validate data */
        rc = lyd_validate(first_p, NULL, ctx, val_opts, 0, &lydctx->node_when, &lydctx->node_types, &lydctx->meta_types,
                &lydctx->ext_val, NULL);
        LY_CHECK_GOTO(rc, cleanup);
    }

    /* set the operation node */
    if (op) {
        *op = lydctx->op_node;
    }

cleanup:
    if (lydctx) {
        lydctx->free(lydctx);
    }
    if (rc) {
        if (parent) {
            /* free all the parsed subtrees */
            for (i = 0; i < parsed.count; ++i) {
                lyd_free_tree(parsed.dnodes[i]);
            }
        } else {
            /* free everything */
            lyd_free_all(*first_p);
            *first_p = NULL;
        }
    } else if (subtree_sibling) {
        rc = LY_ENOT;
    }
    ly_set_erase(&parsed, NULL);
    return rc;
}

LIBYANG_API_DEF LY_ERR
lyd_parse_ext_data(const struct lysc_ext_instance *ext, struct lyd_node *parent, struct ly_in *in, LYD_FORMAT format,
        uint32_t parse_options, uint32_t validate_options, struct lyd_node **tree)
{
    const struct ly_ctx *ctx = ext ? ext->module->ctx : NULL;

    LY_CHECK_ARG_RET(ctx, ext, in, parent || tree, LY_EINVAL);
    LY_CHECK_ARG_RET(ctx, !(parse_options & ~LYD_PARSE_OPTS_MASK), LY_EINVAL);
    LY_CHECK_ARG_RET(ctx, !(validate_options & ~LYD_VALIDATE_OPTS_MASK), LY_EINVAL);

    return lyd_parse(ctx, ext, parent, tree, in, format, parse_options, validate_options, NULL);
}

LIBYANG_API_DEF LY_ERR
lyd_parse_data(const struct ly_ctx *ctx, struct lyd_node *parent, struct ly_in *in, LYD_FORMAT format,
        uint32_t parse_options, uint32_t validate_options, struct lyd_node **tree)
{
    LY_CHECK_ARG_RET(ctx, ctx, in, parent || tree, LY_EINVAL);
    LY_CHECK_ARG_RET(ctx, !(parse_options & ~LYD_PARSE_OPTS_MASK), LY_EINVAL);
    LY_CHECK_ARG_RET(ctx, !(validate_options & ~LYD_VALIDATE_OPTS_MASK), LY_EINVAL);

    return lyd_parse(ctx, NULL, parent, tree, in, format, parse_options, validate_options, NULL);
}

LIBYANG_API_DEF LY_ERR
lyd_parse_data_mem(const struct ly_ctx *ctx, const char *data, LYD_FORMAT format, uint32_t parse_options,
        uint32_t validate_options, struct lyd_node **tree)
{
    LY_ERR ret;
    struct ly_in *in;

    LY_CHECK_RET(ly_in_new_memory(data, &in));
    ret = lyd_parse_data(ctx, NULL, in, format, parse_options, validate_options, tree);

    ly_in_free(in, 0);
    return ret;
}

LIBYANG_API_DEF LY_ERR
lyd_parse_data_fd(const struct ly_ctx *ctx, int fd, LYD_FORMAT format, uint32_t parse_options, uint32_t validate_options,
        struct lyd_node **tree)
{
    LY_ERR ret;
    struct ly_in *in;

    LY_CHECK_RET(ly_in_new_fd(fd, &in));
    ret = lyd_parse_data(ctx, NULL, in, format, parse_options, validate_options, tree);

    ly_in_free(in, 0);
    return ret;
}

LIBYANG_API_DEF LY_ERR
lyd_parse_data_path(const struct ly_ctx *ctx, const char *path, LYD_FORMAT format, uint32_t parse_options,
        uint32_t validate_options, struct lyd_node **tree)
{
    LY_ERR ret;
    struct ly_in *in;

    LY_CHECK_RET(ly_in_new_filepath(path, 0, &in));
    ret = lyd_parse_data(ctx, NULL, in, format, parse_options, validate_options, tree);

    ly_in_free(in, 0);
    return ret;
}

/**
 * @brief Parse YANG data into an operation data tree, in case the extension instance is specified, keep the searching
 * for schema nodes locked inside the extension instance.
 *
 * At least one of @p parent, @p tree, or @p op must always be set.
 *
 * Specific @p data_type values have different parameter meaning as follows:
 * - ::LYD_TYPE_RPC_NETCONF:
 *   - @p parent - must be NULL, the whole RPC is expected;
 *   - @p format - must be ::LYD_XML, NETCONF supports only this format;
 *   - @p tree - must be provided, all the NETCONF-specific XML envelopes will be returned here as
 *               a separate opaque data tree, even if the function fails, this may be returned;
 *   - @p op - must be provided, the RPC/action data tree itself will be returned here, pointing to the operation;
 *
 * - ::LYD_TYPE_NOTIF_NETCONF:
 *   - @p parent - must be NULL, the whole notification is expected;
 *   - @p format - must be ::LYD_XML, NETCONF supports only this format;
 *   - @p tree - must be provided, all the NETCONF-specific XML envelopes will be returned here as
 *               a separate opaque data tree, even if the function fails, this may be returned;
 *   - @p op - must be provided, the notification data tree itself will be returned here, pointing to the operation;
 *
 * - ::LYD_TYPE_REPLY_NETCONF:
 *   - @p parent - must be set, pointing to the invoked RPC operation (RPC or action) node;
 *   - @p format - must be ::LYD_XML, NETCONF supports only this format;
 *   - @p tree - must be provided, all the NETCONF-specific XML envelopes will be returned here as
 *               a separate opaque data tree, even if the function fails, this may be returned;
 *   - @p op - must be NULL, the reply is appended to the RPC;
 *   Note that there are 3 kinds of NETCONF replies - ok, error, and data. Only data reply appends any nodes to the RPC.
 *
 * @param[in] ctx libyang context.
 * @param[in] ext Extension instance providing the specific schema tree to match with the data being parsed.
 * @param[in] parent Optional parent to connect the parsed nodes to.
 * @param[in] in Input handle to read the input from.
 * @param[in] format Expected format of the data in @p in.
 * @param[in] data_type Expected operation to parse (@ref datatype).
 * @param[out] tree Optional full parsed data tree. If @p parent is set, set to NULL.
 * @param[out] op Optional parsed operation node.
 * @return LY_ERR value.
 * @return LY_ENOT if @p data_type is a NETCONF message and the root XML element is not the expected one.
 */
static LY_ERR
lyd_parse_op_(const struct ly_ctx *ctx, const struct lysc_ext_instance *ext, struct lyd_node *parent,
        struct ly_in *in, LYD_FORMAT format, enum lyd_type data_type, struct lyd_node **tree, struct lyd_node **op)
{
    LY_ERR rc = LY_SUCCESS;
    struct lyd_ctx *lydctx = NULL;
    struct ly_set parsed = {0};
    struct lyd_node *first = NULL, *envp = NULL;
    uint32_t i, parse_opts, val_opts;

    if (!ctx) {
        ctx = LYD_CTX(parent);
    }
    if (tree) {
        *tree = NULL;
    }
    if (op) {
        *op = NULL;
    }

    format = lyd_parse_get_format(in, format);

    /* remember input position */
    in->func_start = in->current;

    /* check params based on the data type */
    if ((data_type == LYD_TYPE_RPC_NETCONF) || (data_type == LYD_TYPE_NOTIF_NETCONF)) {
        LY_CHECK_ARG_RET(ctx, format == LYD_XML, !parent, tree, op, LY_EINVAL);
    } else if (data_type == LYD_TYPE_REPLY_NETCONF) {
        LY_CHECK_ARG_RET(ctx, format == LYD_XML, parent, parent->schema->nodetype & (LYS_RPC | LYS_ACTION), tree, !op,
                LY_EINVAL);
    }
    parse_opts = LYD_PARSE_ONLY | LYD_PARSE_STRICT;
    val_opts = 0;

    /* parse the data */
    switch (format) {
    case LYD_XML:
        rc = lyd_parse_xml(ctx, ext, parent, &first, in, parse_opts, val_opts, data_type, &envp, &parsed, NULL, &lydctx);
        if (rc && envp) {
            /* special situation when the envelopes were parsed successfully */
            if (tree) {
                *tree = envp;
            } else {
                lyd_free_all(envp);
            }
            goto cleanup;
        }
        break;
    case LYD_JSON:
        rc = lyd_parse_json(ctx, ext, parent, &first, in, parse_opts, val_opts, data_type, &parsed, NULL, &lydctx);
        break;
    case LYD_LYB:
        rc = lyd_parse_lyb(ctx, ext, parent, &first, in, parse_opts, val_opts, data_type, &parsed, NULL, &lydctx);
        break;
    case LYD_UNKNOWN:
        LOGARG(ctx, format);
        rc = LY_EINVAL;
        break;
    }
    LY_CHECK_GOTO(rc, cleanup);

    /* set out params correctly */
    if (tree) {
        if (envp) {
            /* special out param meaning */
            *tree = envp;
        } else {
            *tree = parent ? NULL : first;
        }
    }
    if (op) {
        *op = lydctx->op_node;
    }

cleanup:
    if (lydctx) {
        lydctx->free(lydctx);
    }
    if (rc) {
        /* free all the parsed nodes */
        if (parsed.count) {
            i = parsed.count;
            do {
                --i;
                lyd_free_tree(parsed.dnodes[i]);
            } while (i);
        }
        if (tree && ((format != LYD_XML) || !envp)) {
            *tree = NULL;
        }
        if (op) {
            *op = NULL;
        }
    }
    ly_set_erase(&parsed, NULL);
    return rc;
}

LIBYANG_API_DEF LY_ERR
lyd_parse_op(const struct ly_ctx *ctx, struct lyd_node *parent, struct ly_in *in, LYD_FORMAT format,
        enum lyd_type data_type, struct lyd_node **tree, struct lyd_node **op)
{
    LY_CHECK_ARG_RET(ctx, ctx || parent, in, data_type, parent || tree || op, LY_EINVAL);

    return lyd_parse_op_(ctx, NULL, parent, in, format, data_type, tree, op);
}

LIBYANG_API_DEF LY_ERR
lyd_parse_ext_op(const struct lysc_ext_instance *ext, struct lyd_node *parent, struct ly_in *in, LYD_FORMAT format,
        enum lyd_type data_type, struct lyd_node **tree, struct lyd_node **op)
{
    const struct ly_ctx *ctx = ext ? ext->module->ctx : NULL;

    LY_CHECK_ARG_RET(ctx, ext, in, data_type, parent || tree || op, LY_EINVAL);

    return lyd_parse_op_(ctx, ext, parent, in, format, data_type, tree, op);
}

struct lyd_node *
lyd_insert_get_next_anchor(const struct lyd_node *first_sibling, const struct lyd_node *new_node)
{
    const struct lysc_node *schema, *sparent;
    struct lyd_node *match = NULL;
    ly_bool found;
    uint32_t getnext_opts;

    assert(new_node);

    if (!first_sibling || !new_node->schema || (LYD_CTX(first_sibling) != LYD_CTX(new_node))) {
        /* insert at the end, no next anchor */
        return NULL;
    }

    getnext_opts = 0;
    if (new_node->schema->flags & LYS_IS_OUTPUT) {
        getnext_opts = LYS_GETNEXT_OUTPUT;
    }

    if (first_sibling->parent && first_sibling->parent->schema && first_sibling->parent->children_ht) {
        /* find the anchor using hashes */
        sparent = first_sibling->parent->schema;
        schema = lys_getnext(new_node->schema, sparent, NULL, getnext_opts);
        while (schema) {
            /* keep trying to find the first existing instance of the closest following schema sibling,
             * otherwise return NULL - inserting at the end */
            if (!lyd_find_sibling_schema(first_sibling, schema, &match)) {
                break;
            }

            schema = lys_getnext(schema, sparent, NULL, getnext_opts);
        }
    } else {
        /* find the anchor without hashes */
        match = (struct lyd_node *)first_sibling;
        sparent = lysc_data_parent(new_node->schema);
        if (!sparent) {
            /* we are in top-level, skip all the data from preceding modules */
            LY_LIST_FOR(match, match) {
                if (!match->schema || (strcmp(lyd_owner_module(match)->name, lyd_owner_module(new_node)->name) >= 0)) {
                    break;
                }
            }
        }

        /* get the first schema sibling */
        schema = lys_getnext(NULL, sparent, new_node->schema->module->compiled, getnext_opts);

        found = 0;
        LY_LIST_FOR(match, match) {
            if (!match->schema || (lyd_owner_module(match) != lyd_owner_module(new_node))) {
                /* we have found an opaque node, which must be at the end, so use it OR
                 * modules do not match, so we must have traversed all the data from new_node module (if any),
                 * we have found the first node of the next module, that is what we want */
                break;
            }

            /* skip schema nodes until we find the instantiated one */
            while (!found) {
                if (new_node->schema == schema) {
                    /* we have found the schema of the new node, continue search to find the first
                     * data node with a different schema (after our schema) */
                    found = 1;
                    break;
                }
                if (match->schema == schema) {
                    /* current node (match) is a data node still before the new node, continue search in data */
                    break;
                }
                schema = lys_getnext(schema, sparent, new_node->schema->module->compiled, getnext_opts);
                assert(schema);
            }

            if (found && (match->schema != new_node->schema)) {
                /* find the next node after we have found our node schema data instance */
                break;
            }
        }
    }

    return match;
}

void
lyd_insert_after_node(struct lyd_node *sibling, struct lyd_node *node)
{
    struct lyd_node_inner *par;

    assert(!node->next && (node->prev == node));

    node->next = sibling->next;
    node->prev = sibling;
    sibling->next = node;
    if (node->next) {
        /* sibling had a succeeding node */
        node->next->prev = node;
    } else {
        /* sibling was last, find first sibling and change its prev */
        if (sibling->parent) {
            sibling = sibling->parent->child;
        } else {
            for ( ; sibling->prev->next != node; sibling = sibling->prev) {}
        }
        sibling->prev = node;
    }
    node->parent = sibling->parent;

    for (par = node->parent; par; par = par->parent) {
        if ((par->flags & LYD_DEFAULT) && !(node->flags & LYD_DEFAULT)) {
            /* remove default flags from NP containers */
            par->flags &= ~LYD_DEFAULT;
        }
    }
}

void
lyd_insert_before_node(struct lyd_node *sibling, struct lyd_node *node)
{
    struct lyd_node_inner *par;

    assert(!node->next && (node->prev == node));

    node->next = sibling;
    /* covers situation of sibling being first */
    node->prev = sibling->prev;
    sibling->prev = node;
    if (node->prev->next) {
        /* sibling had a preceding node */
        node->prev->next = node;
    } else if (sibling->parent) {
        /* sibling was first and we must also change parent child pointer */
        sibling->parent->child = node;
    }
    node->parent = sibling->parent;

    for (par = node->parent; par; par = par->parent) {
        if ((par->flags & LYD_DEFAULT) && !(node->flags & LYD_DEFAULT)) {
            /* remove default flags from NP containers */
            par->flags &= ~LYD_DEFAULT;
        }
    }
}

/**
 * @brief Insert node as the first and only child of a parent.
 *
 * Handles inserting into NP containers and key-less lists.
 *
 * @param[in] parent Parent to insert into.
 * @param[in] node Node to insert.
 */
static void
lyd_insert_only_child(struct lyd_node *parent, struct lyd_node *node)
{
    struct lyd_node_inner *par;

    assert(parent && !lyd_child(parent) && !node->next && (node->prev == node));
    assert(!parent->schema || (parent->schema->nodetype & LYD_NODE_INNER));

    par = (struct lyd_node_inner *)parent;

    par->child = node;
    node->parent = par;

    for ( ; par; par = par->parent) {
        if ((par->flags & LYD_DEFAULT) && !(node->flags & LYD_DEFAULT)) {
            /* remove default flags from NP containers */
            par->flags &= ~LYD_DEFAULT;
        }
    }
}

/**
 * @brief Learn whether a list instance has all the keys.
 *
 * @param[in] list List instance to check.
 * @return non-zero if all the keys were found,
 * @return 0 otherwise.
 */
static int
lyd_insert_has_keys(const struct lyd_node *list)
{
    const struct lyd_node *key;
    const struct lysc_node *skey = NULL;

    assert(list->schema->nodetype == LYS_LIST);
    key = lyd_child(list);
    while ((skey = lys_getnext(skey, list->schema, NULL, 0)) && (skey->flags & LYS_KEY)) {
        if (!key || (key->schema != skey)) {
            /* key missing */
            return 0;
        }

        key = key->next;
    }

    /* all keys found */
    return 1;
}

void
lyd_insert_node(struct lyd_node *parent, struct lyd_node **first_sibling_p, struct lyd_node *node, ly_bool last)
{
    struct lyd_node *anchor, *first_sibling;

    /* inserting list without its keys is not supported */
    assert((parent || first_sibling_p) && node && (node->hash || !node->schema));
    assert(!parent || !parent->schema ||
            (parent->schema->nodetype & (LYS_CONTAINER | LYS_LIST | LYS_RPC | LYS_ACTION | LYS_NOTIF)));

    if (!parent && first_sibling_p && (*first_sibling_p) && (*first_sibling_p)->parent) {
        parent = lyd_parent(*first_sibling_p);
    }

    /* get first sibling */
    first_sibling = parent ? lyd_child(parent) : *first_sibling_p;

    if (last || (first_sibling && (first_sibling->flags & LYD_EXT))) {
        /* no next anchor */
        anchor = NULL;
    } else {
        /* find the anchor, our next node, so we can insert before it */
        anchor = lyd_insert_get_next_anchor(first_sibling, node);
    }

    if (anchor) {
        /* insert before the anchor */
        lyd_insert_before_node(anchor, node);
        if (!parent && (*first_sibling_p == anchor)) {
            /* move first sibling */
            *first_sibling_p = node;
        }
    } else if (first_sibling) {
        /* insert as the last node */
        lyd_insert_after_node(first_sibling->prev, node);
    } else if (parent) {
        /* insert as the only child */
        lyd_insert_only_child(parent, node);
    } else {
        /* insert as the only sibling */
        *first_sibling_p = node;
    }

    /* insert into parent HT */
    lyd_insert_hash(node);

    /* finish hashes for our parent, if needed and possible */
    if (node->schema && (node->schema->flags & LYS_KEY) && parent && lyd_insert_has_keys(parent)) {
        lyd_hash(parent);

        /* now we can insert even the list into its parent HT */
        lyd_insert_hash(parent);
    }
}

/**
 * @brief Check schema place of a node to be inserted.
 *
 * @param[in] parent Schema node of the parent data node.
 * @param[in] sibling Schema node of a sibling data node.
 * @param[in] schema Schema node if the data node to be inserted.
 * @return LY_SUCCESS on success.
 * @return LY_EINVAL if the place is invalid.
 */
static LY_ERR
lyd_insert_check_schema(const struct lysc_node *parent, const struct lysc_node *sibling, const struct lysc_node *schema)
{
    const struct lysc_node *par2;

    assert(!parent || !(parent->nodetype & (LYS_CASE | LYS_CHOICE)));
    assert(!sibling || !(sibling->nodetype & (LYS_CASE | LYS_CHOICE)));
    assert(!schema || !(schema->nodetype & (LYS_CASE | LYS_CHOICE)));

    if (!schema || (!parent && !sibling)) {
        /* opaque nodes can be inserted wherever */
        return LY_SUCCESS;
    }

    if (!parent) {
        parent = lysc_data_parent(sibling);
    }

    /* find schema parent */
    par2 = lysc_data_parent(schema);

    if (parent) {
        /* inner node */
        if (par2 != parent) {
            LOGERR(schema->module->ctx, LY_EINVAL, "Cannot insert, parent of \"%s\" is not \"%s\".", schema->name,
                    parent->name);
            return LY_EINVAL;
        }
    } else {
        /* top-level node */
        if (par2) {
            LOGERR(schema->module->ctx, LY_EINVAL, "Cannot insert, node \"%s\" is not top-level.", schema->name);
            return LY_EINVAL;
        }
    }

    return LY_SUCCESS;
}

LIBYANG_API_DEF LY_ERR
lyd_insert_child(struct lyd_node *parent, struct lyd_node *node)
{
    struct lyd_node *iter;

    LY_CHECK_ARG_RET(NULL, parent, node, !parent->schema || (parent->schema->nodetype & LYD_NODE_INNER), LY_EINVAL);
    LY_CHECK_CTX_EQUAL_RET(LYD_CTX(parent), LYD_CTX(node), LY_EINVAL);

    LY_CHECK_RET(lyd_insert_check_schema(parent->schema, NULL, node->schema));

    if (node->schema && (node->schema->flags & LYS_KEY)) {
        LOGERR(LYD_CTX(parent), LY_EINVAL, "Cannot insert key \"%s\".", node->schema->name);
        return LY_EINVAL;
    }

    if (node->parent || node->prev->next) {
        lyd_unlink_tree(node);
    }

    while (node) {
        iter = node->next;
        lyd_unlink_tree(node);
        lyd_insert_node(parent, NULL, node, 0);
        node = iter;
    }
    return LY_SUCCESS;
}

LIBYANG_API_DEF LY_ERR
lyd_insert_ext(struct lyd_node *parent, struct lyd_node *first)
{
    struct lyd_node *iter;

    LY_CHECK_ARG_RET(NULL, parent, first, !first->parent, !first->prev->next,
            !parent->schema || (parent->schema->nodetype & LYD_NODE_INNER), LY_EINVAL);

    if (first->schema && (first->schema->flags & LYS_KEY)) {
        LOGERR(LYD_CTX(parent), LY_EINVAL, "Cannot insert key \"%s\".", first->schema->name);
        return LY_EINVAL;
    }

    while (first) {
        iter = first->next;
        lyd_unlink_tree(first);
        lyd_insert_node(parent, NULL, first, 1);
        first = iter;
    }
    return LY_SUCCESS;
}

LIBYANG_API_DEF LY_ERR
lyd_insert_sibling(struct lyd_node *sibling, struct lyd_node *node, struct lyd_node **first)
{
    struct lyd_node *iter;

    LY_CHECK_ARG_RET(NULL, node, LY_EINVAL);
    LY_CHECK_CTX_EQUAL_RET(sibling ? LYD_CTX(sibling) : NULL, LYD_CTX(node), LY_EINVAL);

    if (sibling) {
        LY_CHECK_RET(lyd_insert_check_schema(NULL, sibling->schema, node->schema));
    }

    if (sibling == node) {
        /* we need to keep the connection to siblings so we can insert into them */
        sibling = sibling->prev;
    }

    if (node->parent || node->prev->next) {
        lyd_unlink_tree(node);
    }

    while (node) {
        if (lysc_is_key(node->schema)) {
            LOGERR(LYD_CTX(node), LY_EINVAL, "Cannot insert key \"%s\".", node->schema->name);
            return LY_EINVAL;
        }

        iter = node->next;
        lyd_unlink_tree(node);
        lyd_insert_node(NULL, &sibling, node, 0);
        node = iter;
    }

    if (first) {
        /* find the first sibling */
        *first = sibling;
        while ((*first)->prev->next) {
            *first = (*first)->prev;
        }
    }

    return LY_SUCCESS;
}

LIBYANG_API_DEF LY_ERR
lyd_insert_before(struct lyd_node *sibling, struct lyd_node *node)
{
    LY_CHECK_ARG_RET(NULL, sibling, node, sibling != node, LY_EINVAL);
    LY_CHECK_CTX_EQUAL_RET(LYD_CTX(sibling), LYD_CTX(node), LY_EINVAL);

    LY_CHECK_RET(lyd_insert_check_schema(NULL, sibling->schema, node->schema));

    if (node->schema && (!(node->schema->nodetype & (LYS_LIST | LYS_LEAFLIST)) || !(node->schema->flags & LYS_ORDBY_USER))) {
        LOGERR(LYD_CTX(sibling), LY_EINVAL, "Can be used only for user-ordered nodes.");
        return LY_EINVAL;
    }
    if (node->schema && sibling->schema && (node->schema != sibling->schema)) {
        LOGERR(LYD_CTX(sibling), LY_EINVAL, "Cannot insert before a different schema node instance.");
        return LY_EINVAL;
    }

    lyd_unlink_tree(node);
    lyd_insert_before_node(sibling, node);
    lyd_insert_hash(node);

    return LY_SUCCESS;
}

LIBYANG_API_DEF LY_ERR
lyd_insert_after(struct lyd_node *sibling, struct lyd_node *node)
{
    LY_CHECK_ARG_RET(NULL, sibling, node, sibling != node, LY_EINVAL);
    LY_CHECK_CTX_EQUAL_RET(LYD_CTX(sibling), LYD_CTX(node), LY_EINVAL);

    LY_CHECK_RET(lyd_insert_check_schema(NULL, sibling->schema, node->schema));

    if (node->schema && (!(node->schema->nodetype & (LYS_LIST | LYS_LEAFLIST)) || !(node->schema->flags & LYS_ORDBY_USER))) {
        LOGERR(LYD_CTX(sibling), LY_EINVAL, "Can be used only for user-ordered nodes.");
        return LY_EINVAL;
    }
    if (node->schema && sibling->schema && (node->schema != sibling->schema)) {
        LOGERR(LYD_CTX(sibling), LY_EINVAL, "Cannot insert after a different schema node instance.");
        return LY_EINVAL;
    }

    lyd_unlink_tree(node);
    lyd_insert_after_node(sibling, node);
    lyd_insert_hash(node);

    return LY_SUCCESS;
}

LIBYANG_API_DEF void
lyd_unlink_siblings(struct lyd_node *node)
{
    struct lyd_node *next, *elem, *first = NULL;

    LY_LIST_FOR_SAFE(node, next, elem) {
        lyd_unlink_tree(elem);
        lyd_insert_node(NULL, &first, elem, 1);
    }
}

LIBYANG_API_DEF void
lyd_unlink_tree(struct lyd_node *node)
{
    struct lyd_node *iter;

    if (!node) {
        return;
    }

    /* update hashes while still linked into the tree */
    lyd_unlink_hash(node);

    /* unlink from siblings */
    if (node->prev->next) {
        node->prev->next = node->next;
    }
    if (node->next) {
        node->next->prev = node->prev;
    } else {
        /* unlinking the last node */
        if (node->parent) {
            iter = node->parent->child;
        } else {
            iter = node->prev;
            while (iter->prev != node) {
                iter = iter->prev;
            }
        }
        /* update the "last" pointer from the first node */
        iter->prev = node->prev;
    }

    /* unlink from parent */
    if (node->parent) {
        if (node->parent->child == node) {
            /* the node is the first child */
            node->parent->child = node->next;
        }

        /* check for NP container whether its last non-default node is not being unlinked */
        if (node->parent->schema && (node->parent->schema->nodetype == LYS_CONTAINER) &&
                !(node->parent->flags & LYD_DEFAULT) && !(node->parent->schema->flags & LYS_PRESENCE)) {
            LY_LIST_FOR(node->parent->child, iter) {
                if ((iter != node) && !(iter->flags & LYD_DEFAULT)) {
                    break;
                }
            }
            if (!iter) {
                node->parent->flags |= LYD_DEFAULT;
            }
        }

        node->parent = NULL;
    }

    node->next = NULL;
    node->prev = node;
}

void
lyd_insert_meta(struct lyd_node *parent, struct lyd_meta *meta, ly_bool clear_dflt)
{
    struct lyd_meta *last, *iter;

    assert(parent);

    if (!meta) {
        return;
    }

    for (iter = meta; iter; iter = iter->next) {
        iter->parent = parent;
    }

    /* insert as the last attribute */
    if (parent->meta) {
        for (last = parent->meta; last->next; last = last->next) {}
        last->next = meta;
    } else {
        parent->meta = meta;
    }

    /* remove default flags from NP containers */
    while (clear_dflt && parent && (parent->schema->nodetype == LYS_CONTAINER) && (parent->flags & LYD_DEFAULT)) {
        parent->flags &= ~LYD_DEFAULT;
        parent = lyd_parent(parent);
    }
}

LY_ERR
lyd_create_meta(struct lyd_node *parent, struct lyd_meta **meta, const struct lys_module *mod, const char *name,
        size_t name_len, const char *value, size_t value_len, ly_bool *dynamic, LY_VALUE_FORMAT format,
        void *prefix_data, uint32_t hints, const struct lysc_node *ctx_node, ly_bool clear_dflt, ly_bool *incomplete)
{
    LY_ERR ret = LY_SUCCESS;
    struct lysc_ext_instance *ant = NULL;
    const struct lysc_type **ant_type;
    struct lyd_meta *mt, *last;
    LY_ARRAY_COUNT_TYPE u;

    assert((parent || meta) && mod);

    LOG_LOCSET(ctx_node, parent, NULL, NULL);

    LY_ARRAY_FOR(mod->compiled->exts, u) {
        if ((mod->compiled->exts[u].def->plugin == lyplg_find(LYPLG_EXTENSION, LYEXT_PLUGIN_INTERNAL_ANNOTATION)) &&
                !ly_strncmp(mod->compiled->exts[u].argument, name, name_len)) {
            /* we have the annotation definition */
            ant = &mod->compiled->exts[u];
            break;
        }
    }
    if (!ant) {
        /* attribute is not defined as a metadata annotation (RFC 7952) */
        LOGVAL(mod->ctx, LYVE_REFERENCE, "Annotation definition for attribute \"%s:%.*s\" not found.",
                mod->name, (int)name_len, name);
        ret = LY_EINVAL;
        goto cleanup;
    }

    mt = calloc(1, sizeof *mt);
    LY_CHECK_ERR_GOTO(!mt, LOGMEM(mod->ctx); ret = LY_EMEM, cleanup);
    mt->parent = parent;
    mt->annotation = ant;
    ant_type = ant->substmts[ANNOTATION_SUBSTMT_TYPE].storage;
    ret = lyd_value_store(mod->ctx, &mt->value, *ant_type, value, value_len, dynamic, format, prefix_data, hints,
            ctx_node, incomplete);
    LY_CHECK_ERR_GOTO(ret, free(mt), cleanup);
    ret = lydict_insert(mod->ctx, name, name_len, &mt->name);
    LY_CHECK_ERR_GOTO(ret, free(mt), cleanup);

    /* insert as the last attribute */
    if (parent) {
        lyd_insert_meta(parent, mt, clear_dflt);
    } else if (*meta) {
        for (last = *meta; last->next; last = last->next) {}
        last->next = mt;
    }

    if (meta) {
        *meta = mt;
    }

cleanup:
    LOG_LOCBACK(ctx_node ? 1 : 0, parent ? 1 : 0, 0, 0);
    return ret;
}

void
lyd_insert_attr(struct lyd_node *parent, struct lyd_attr *attr)
{
    struct lyd_attr *last, *iter;
    struct lyd_node_opaq *opaq;

    assert(parent && !parent->schema);

    if (!attr) {
        return;
    }

    opaq = (struct lyd_node_opaq *)parent;
    for (iter = attr; iter; iter = iter->next) {
        iter->parent = opaq;
    }

    /* insert as the last attribute */
    if (opaq->attr) {
        for (last = opaq->attr; last->next; last = last->next) {}
        last->next = attr;
    } else {
        opaq->attr = attr;
    }
}

LY_ERR
lyd_create_attr(struct lyd_node *parent, struct lyd_attr **attr, const struct ly_ctx *ctx, const char *name, size_t name_len,
        const char *prefix, size_t prefix_len, const char *module_key, size_t module_key_len, const char *value,
        size_t value_len, ly_bool *dynamic, LY_VALUE_FORMAT format, void *val_prefix_data, uint32_t hints)
{
    LY_ERR ret = LY_SUCCESS;
    struct lyd_attr *at, *last;

    assert(ctx && (parent || attr) && (!parent || !parent->schema));
    assert(name && name_len && format);

    if (!value_len && (!dynamic || !*dynamic)) {
        value = "";
    }

    at = calloc(1, sizeof *at);
    LY_CHECK_ERR_RET(!at, LOGMEM(ctx); ly_free_prefix_data(format, val_prefix_data), LY_EMEM);

    LY_CHECK_GOTO(ret = lydict_insert(ctx, name, name_len, &at->name.name), finish);
    if (prefix_len) {
        LY_CHECK_GOTO(ret = lydict_insert(ctx, prefix, prefix_len, &at->name.prefix), finish);
    }
    if (module_key_len) {
        LY_CHECK_GOTO(ret = lydict_insert(ctx, module_key, module_key_len, &at->name.module_ns), finish);
    }

    if (dynamic && *dynamic) {
        ret = lydict_insert_zc(ctx, (char *)value, &at->value);
        LY_CHECK_GOTO(ret, finish);
        *dynamic = 0;
    } else {
        LY_CHECK_GOTO(ret = lydict_insert(ctx, value, value_len, &at->value), finish);
    }
    at->format = format;
    at->val_prefix_data = val_prefix_data;
    at->hints = hints;

    /* insert as the last attribute */
    if (parent) {
        lyd_insert_attr(parent, at);
    } else if (*attr) {
        for (last = *attr; last->next; last = last->next) {}
        last->next = at;
    }

finish:
    if (ret) {
        lyd_free_attr_single(ctx, at);
    } else if (attr) {
        *attr = at;
    }
    return LY_SUCCESS;
}

LIBYANG_API_DEF const struct lyd_node_term *
lyd_target(const struct ly_path *path, const struct lyd_node *tree)
{
    struct lyd_node *target;

    if (ly_path_eval(path, tree, &target)) {
        return NULL;
    }

    return (struct lyd_node_term *)target;
}

/**
 * @brief Check the equality of the two schemas from different contexts.
 *
 * @param schema1 of first node.
 * @param schema2 of second node.
 * @return 1 if the schemas are equal otherwise 0.
 */
static ly_bool
lyd_compare_schema_equal(const struct lysc_node *schema1, const struct lysc_node *schema2)
{
    if (!schema1 && !schema2) {
        return 1;
    } else if (!schema1 || !schema2) {
        return 0;
    }

    assert(schema1->module->ctx != schema2->module->ctx);

    if (schema1->nodetype != schema2->nodetype) {
        return 0;
    }

    if (strcmp(schema1->name, schema2->name)) {
        return 0;
    }

    if (strcmp(schema1->module->name, schema2->module->name)) {
        return 0;
    }

    if (schema1->module->revision || schema2->module->revision) {
        if (!schema1->module->revision || !schema2->module->revision) {
            return 0;
        }
        if (strcmp(schema1->module->revision, schema2->module->revision)) {
            return 0;
        }
    }

    return 1;
}

/**
 * @brief Check the equality of the schemas for all parent nodes.
 *
 * Both nodes must be from different contexts.
 *
 * @param node1 Data of first node.
 * @param node2 Data of second node.
 * @return 1 if the all related parental schemas are equal otherwise 0.
 */
static ly_bool
lyd_compare_schema_parents_equal(const struct lyd_node *node1, const struct lyd_node *node2)
{
    const struct lysc_node *parent1, *parent2;

    assert(node1 && node2);

    for (parent1 = node1->schema->parent, parent2 = node2->schema->parent;
            parent1 && parent2;
            parent1 = parent1->parent, parent2 = parent2->parent) {
        if (!lyd_compare_schema_equal(parent1, parent2)) {
            return 0;
        }
    }

    if (parent1 || parent2) {
        return 0;
    }

    return 1;
}

/**
 * @brief Internal implementation of @ref lyd_compare_single.
 * @copydoc lyd_compare_single
 * @param[in] parental_schemas_checked Flag used for optimization.
 * When this function is called for the first time, the flag must be set to 0.
 * The @ref lyd_compare_schema_parents_equal should be called only once during
 * recursive calls, and this is accomplished by setting to 1 in the lyd_compare_single_ body.
 */
static LY_ERR
lyd_compare_single_(const struct lyd_node *node1, const struct lyd_node *node2,
        uint32_t options, ly_bool parental_schemas_checked)
{
    const struct lyd_node *iter1, *iter2;
    struct lyd_node_term *term1, *term2;
    struct lyd_node_any *any1, *any2;
    struct lyd_node_opaq *opaq1, *opaq2;
    size_t len1, len2;

    if (!node1 || !node2) {
        if (node1 == node2) {
            return LY_SUCCESS;
        } else {
            return LY_ENOT;
        }
    }

    if (LYD_CTX(node1) == LYD_CTX(node2)) {
        /* same contexts */
        if (node1->schema != node2->schema) {
            return LY_ENOT;
        }
    } else {
        /* different contexts */
        if (!lyd_compare_schema_equal(node1->schema, node2->schema)) {
            return LY_ENOT;
        }
        if (!parental_schemas_checked) {
            if (!lyd_compare_schema_parents_equal(node1, node2)) {
                return LY_ENOT;
            }
            parental_schemas_checked = 1;
        }
    }

    if (node1->hash != node2->hash) {
        return LY_ENOT;
    }
    /* equal hashes do not mean equal nodes, they can be just in collision so the nodes must be checked explicitly */

    if (!node1->schema) {
        opaq1 = (struct lyd_node_opaq *)node1;
        opaq2 = (struct lyd_node_opaq *)node2;
        if ((strcmp(opaq1->name.name, opaq2->name.name)) || (opaq1->format != opaq2->format) ||
                (strcmp(opaq1->name.module_ns, opaq2->name.module_ns))) {
            return LY_ENOT;
        }
        switch (opaq1->format) {
        case LY_VALUE_XML:
            if (lyxml_value_compare(LYD_CTX(node1), opaq1->value, opaq1->val_prefix_data, LYD_CTX(node2), opaq2->value,
                    opaq2->val_prefix_data)) {
                return LY_ENOT;
            }
            break;
        case LY_VALUE_JSON:
            /* prefixes in JSON are unique, so it is not necessary to canonize the values */
            if (strcmp(opaq1->value, opaq2->value)) {
                return LY_ENOT;
            }
            break;
        default:
            /* not allowed */
            LOGINT(LYD_CTX(node1));
            return LY_EINT;
        }
        if (options & LYD_COMPARE_FULL_RECURSION) {
            iter1 = opaq1->child;
            iter2 = opaq2->child;
            goto all_children_compare;
        }
        return LY_SUCCESS;
    } else {
        switch (node1->schema->nodetype) {
        case LYS_LEAF:
        case LYS_LEAFLIST:
            if (options & LYD_COMPARE_DEFAULTS) {
                if ((node1->flags & LYD_DEFAULT) != (node2->flags & LYD_DEFAULT)) {
                    return LY_ENOT;
                }
            }

            term1 = (struct lyd_node_term *)node1;
            term2 = (struct lyd_node_term *)node2;

            /* same contexts */
            if (LYD_CTX(node1) == LYD_CTX(node2)) {
                return term1->value.realtype->plugin->compare(&term1->value, &term2->value);
            }

            /* different contexts */
            if (strcmp(lyd_get_value(node1), lyd_get_value(node2))) {
                return LY_ENOT;
            }
            return LY_SUCCESS;
        case LYS_CONTAINER:
        case LYS_RPC:
        case LYS_ACTION:
        case LYS_NOTIF:
            if (options & LYD_COMPARE_DEFAULTS) {
                if ((node1->flags & LYD_DEFAULT) != (node2->flags & LYD_DEFAULT)) {
                    return LY_ENOT;
                }
            }
            if (options & LYD_COMPARE_FULL_RECURSION) {
                iter1 = lyd_child(node1);
                iter2 = lyd_child(node2);
                goto all_children_compare;
            }
            return LY_SUCCESS;
        case LYS_LIST:
            iter1 = lyd_child(node1);
            iter2 = lyd_child(node2);

            if (!(node1->schema->flags & LYS_KEYLESS) && !(options & LYD_COMPARE_FULL_RECURSION)) {
                /* lists with keys, their equivalence is based on their keys */
                for (const struct lysc_node *key = lysc_node_child(node1->schema);
                        key && (key->flags & LYS_KEY);
                        key = key->next) {
                    if (lyd_compare_single_(iter1, iter2, options, parental_schemas_checked)) {
                        return LY_ENOT;
                    }
                    iter1 = iter1->next;
                    iter2 = iter2->next;
                }
            } else {
                /* lists without keys, their equivalence is based on equivalence of all the children (both direct and indirect) */

all_children_compare:
                if (!iter1 && !iter2) {
                    /* no children, nothing to compare */
                    return LY_SUCCESS;
                }

                for ( ; iter1 && iter2; iter1 = iter1->next, iter2 = iter2->next) {
                    if (lyd_compare_single_(iter1, iter2, options | LYD_COMPARE_FULL_RECURSION, parental_schemas_checked)) {
                        return LY_ENOT;
                    }
                }
                if (iter1 || iter2) {
                    return LY_ENOT;
                }
            }
            return LY_SUCCESS;
        case LYS_ANYXML:
        case LYS_ANYDATA:
            any1 = (struct lyd_node_any *)node1;
            any2 = (struct lyd_node_any *)node2;

            if (any1->value_type != any2->value_type) {
                return LY_ENOT;
            }
            switch (any1->value_type) {
            case LYD_ANYDATA_DATATREE:
                iter1 = any1->value.tree;
                iter2 = any2->value.tree;
                goto all_children_compare;
            case LYD_ANYDATA_STRING:
            case LYD_ANYDATA_XML:
            case LYD_ANYDATA_JSON:
                len1 = strlen(any1->value.str);
                len2 = strlen(any2->value.str);
                if ((len1 != len2) || strcmp(any1->value.str, any2->value.str)) {
                    return LY_ENOT;
                }
                return LY_SUCCESS;
            case LYD_ANYDATA_LYB:
                len1 = lyd_lyb_data_length(any1->value.mem);
                len2 = lyd_lyb_data_length(any2->value.mem);
                if ((len1 != len2) || memcmp(any1->value.mem, any2->value.mem, len1)) {
                    return LY_ENOT;
                }
                return LY_SUCCESS;
            }
        }
    }

    LOGINT(LYD_CTX(node1));
    return LY_EINT;
}

LIBYANG_API_DEF LY_ERR
lyd_compare_single(const struct lyd_node *node1, const struct lyd_node *node2, uint32_t options)
{
    return lyd_compare_single_(node1, node2, options, 0);
}

LIBYANG_API_DEF LY_ERR
lyd_compare_siblings(const struct lyd_node *node1, const struct lyd_node *node2, uint32_t options)
{
    for ( ; node1 && node2; node1 = node1->next, node2 = node2->next) {
        LY_CHECK_RET(lyd_compare_single(node1, node2, options));
    }

    if (node1 == node2) {
        return LY_SUCCESS;
    }
    return LY_ENOT;
}

LIBYANG_API_DEF LY_ERR
lyd_compare_meta(const struct lyd_meta *meta1, const struct lyd_meta *meta2)
{
    if (!meta1 || !meta2) {
        if (meta1 == meta2) {
            return LY_SUCCESS;
        } else {
            return LY_ENOT;
        }
    }

    if ((meta1->annotation->module->ctx != meta2->annotation->module->ctx) || (meta1->annotation != meta2->annotation)) {
        return LY_ENOT;
    }

    return meta1->value.realtype->plugin->compare(&meta1->value, &meta2->value);
}

/**
 * @brief Create a copy of the attribute.
 *
 * @param[in] attr Attribute to copy.
 * @param[in] node Opaque where to append the new attribute.
 * @param[out] dup Optional created attribute copy.
 * @return LY_ERR value.
 */
static LY_ERR
lyd_dup_attr_single(const struct lyd_attr *attr, struct lyd_node *node, struct lyd_attr **dup)
{
    LY_ERR ret = LY_SUCCESS;
    struct lyd_attr *a, *last;
    struct lyd_node_opaq *opaq = (struct lyd_node_opaq *)node;

    LY_CHECK_ARG_RET(NULL, attr, node, !node->schema, LY_EINVAL);

    /* create a copy */
    a = calloc(1, sizeof *attr);
    LY_CHECK_ERR_RET(!a, LOGMEM(LYD_CTX(node)), LY_EMEM);

    LY_CHECK_GOTO(ret = lydict_insert(LYD_CTX(node), attr->name.name, 0, &a->name.name), finish);
    LY_CHECK_GOTO(ret = lydict_insert(LYD_CTX(node), attr->name.prefix, 0, &a->name.prefix), finish);
    LY_CHECK_GOTO(ret = lydict_insert(LYD_CTX(node), attr->name.module_ns, 0, &a->name.module_ns), finish);
    LY_CHECK_GOTO(ret = lydict_insert(LYD_CTX(node), attr->value, 0, &a->value), finish);
    a->hints = attr->hints;
    a->format = attr->format;
    if (attr->val_prefix_data) {
        ret = ly_dup_prefix_data(LYD_CTX(node), attr->format, attr->val_prefix_data, &a->val_prefix_data);
        LY_CHECK_GOTO(ret, finish);
    }

    /* insert as the last attribute */
    a->parent = opaq;
    if (opaq->attr) {
        for (last = opaq->attr; last->next; last = last->next) {}
        last->next = a;
    } else {
        opaq->attr = a;
    }

finish:
    if (ret) {
        lyd_free_attr_single(LYD_CTX(node), a);
    } else if (dup) {
        *dup = a;
    }
    return LY_SUCCESS;
}

/**
 * @brief Find @p schema equivalent in @p trg_ctx.
 *
 * @param[in] schema Schema node to find.
 * @param[in] trg_ctx Target context to search in.
 * @param[in] parent Data parent of @p schema, if any.
 * @param[out] trg_schema Found schema from @p trg_ctx to use.
 * @return LY_RRR value.
 */
static LY_ERR
lyd_dup_find_schema(const struct lysc_node *schema, const struct ly_ctx *trg_ctx, const struct lyd_node *parent,
        const struct lysc_node **trg_schema)
{
    const struct lysc_node *src_parent = NULL, *trg_parent = NULL, *sp, *tp;
    const struct lys_module *trg_mod = NULL;
    char *path;

    if (!schema) {
        /* opaque node */
        *trg_schema = NULL;
        return LY_SUCCESS;
    }

    if (lysc_data_parent(schema) && parent && parent->schema) {
        /* start from schema parent */
        trg_parent = parent->schema;
        src_parent = lysc_data_parent(schema);
    }

    do {
        /* find the next parent */
        sp = schema;
        while (sp->parent != src_parent) {
            sp = sp->parent;
        }
        src_parent = sp;

        if (!src_parent->parent) {
            /* find the module first */
            trg_mod = ly_ctx_get_module_implemented(trg_ctx, src_parent->module->name);
            if (!trg_mod) {
                LOGERR(trg_ctx, LY_ENOTFOUND, "Module \"%s\" not present/implemented in the target context.",
                        src_parent->module->name);
                return LY_ENOTFOUND;
            }
        }

        /* find the next parent */
        assert(trg_parent || trg_mod);
        tp = NULL;
        while ((tp = lys_getnext(tp, trg_parent, trg_mod ? trg_mod->compiled : NULL, 0))) {
            if (!strcmp(tp->name, src_parent->name) && !strcmp(tp->module->name, src_parent->module->name)) {
                break;
            }
        }
        if (!tp) {
            /* schema node not found */
            path = lysc_path(src_parent, LYSC_PATH_LOG, NULL, 0);
            LOGERR(trg_ctx, LY_ENOTFOUND, "Schema node \"%s\" not found in the target context.", path);
            free(path);
            return LY_ENOTFOUND;
        }

        trg_parent = tp;
    } while (schema != src_parent);

    /* success */
    *trg_schema = trg_parent;
    return LY_SUCCESS;
}

/**
 * @brief Duplicate a single node and connect it into @p parent (if present) or last of @p first siblings.
 *
 * Ignores ::LYD_DUP_WITH_PARENTS and ::LYD_DUP_WITH_SIBLINGS which are supposed to be handled by lyd_dup().
 *
 * @param[in] node Node to duplicate.
 * @param[in] trg_ctx Target context for duplicated nodes.
 * @param[in] parent Parent to insert into, NULL for top-level sibling.
 * @param[in] insert_last Whether the duplicated node can be inserted as the last child of @p parent. Set for
 * recursive duplication as an optimization.
 * @param[in,out] first First sibling, NULL if no top-level sibling exist yet. Can be also NULL if @p parent is set.
 * @param[in] options Bitmask of options flags, see @ref dupoptions.
 * @param[out] dup_p Pointer where the created duplicated node is placed (besides connecting it to @p parent / @p first).
 * @return LY_ERR value.
 */
static LY_ERR
lyd_dup_r(const struct lyd_node *node, const struct ly_ctx *trg_ctx, struct lyd_node *parent, ly_bool insert_last,
        struct lyd_node **first, uint32_t options, struct lyd_node **dup_p)
{
    LY_ERR ret;
    struct lyd_node *dup = NULL;
    struct lyd_meta *meta;
    struct lyd_attr *attr;
    struct lyd_node_any *any;
    const struct lysc_type *type;
    const char *val_can;

    LY_CHECK_ARG_RET(NULL, node, LY_EINVAL);

    if (node->flags & LYD_EXT) {
        if (options & LYD_DUP_NO_EXT) {
            /* no not duplicate this subtree */
            return LY_SUCCESS;
        }

        /* we need to use the same context */
        trg_ctx = LYD_CTX(node);
    }

    if (!node->schema) {
        dup = calloc(1, sizeof(struct lyd_node_opaq));
        ((struct lyd_node_opaq *)dup)->ctx = trg_ctx;
    } else {
        switch (node->schema->nodetype) {
        case LYS_RPC:
        case LYS_ACTION:
        case LYS_NOTIF:
        case LYS_CONTAINER:
        case LYS_LIST:
            dup = calloc(1, sizeof(struct lyd_node_inner));
            break;
        case LYS_LEAF:
        case LYS_LEAFLIST:
            dup = calloc(1, sizeof(struct lyd_node_term));
            break;
        case LYS_ANYDATA:
        case LYS_ANYXML:
            dup = calloc(1, sizeof(struct lyd_node_any));
            break;
        default:
            LOGINT(trg_ctx);
            ret = LY_EINT;
            goto error;
        }
    }
    LY_CHECK_ERR_GOTO(!dup, LOGMEM(trg_ctx); ret = LY_EMEM, error);

    if (options & LYD_DUP_WITH_FLAGS) {
        dup->flags = node->flags;
    } else {
        dup->flags = (node->flags & (LYD_DEFAULT | LYD_EXT)) | LYD_NEW;
    }
    if (trg_ctx == LYD_CTX(node)) {
        dup->schema = node->schema;
    } else {
        ret = lyd_dup_find_schema(node->schema, trg_ctx, parent, &dup->schema);
        if (ret) {
            /* has no schema but is not an opaque node */
            free(dup);
            dup = NULL;
            goto error;
        }
    }
    dup->prev = dup;

    /* duplicate metadata/attributes */
    if (!(options & LYD_DUP_NO_META)) {
        if (!node->schema) {
            LY_LIST_FOR(((struct lyd_node_opaq *)node)->attr, attr) {
                LY_CHECK_GOTO(ret = lyd_dup_attr_single(attr, dup, NULL), error);
            }
        } else {
            LY_LIST_FOR(node->meta, meta) {
                LY_CHECK_GOTO(ret = lyd_dup_meta_single(meta, dup, NULL), error);
            }
        }
    }

    /* nodetype-specific work */
    if (!dup->schema) {
        struct lyd_node_opaq *opaq = (struct lyd_node_opaq *)dup;
        struct lyd_node_opaq *orig = (struct lyd_node_opaq *)node;
        struct lyd_node *child;

        if (options & LYD_DUP_RECURSIVE) {
            /* duplicate all the children */
            LY_LIST_FOR(orig->child, child) {
                LY_CHECK_GOTO(ret = lyd_dup_r(child, trg_ctx, dup, 1, NULL, options, NULL), error);
            }
        }
        LY_CHECK_GOTO(ret = lydict_insert(trg_ctx, orig->name.name, 0, &opaq->name.name), error);
        LY_CHECK_GOTO(ret = lydict_insert(trg_ctx, orig->name.prefix, 0, &opaq->name.prefix), error);
        LY_CHECK_GOTO(ret = lydict_insert(trg_ctx, orig->name.module_ns, 0, &opaq->name.module_ns), error);
        LY_CHECK_GOTO(ret = lydict_insert(trg_ctx, orig->value, 0, &opaq->value), error);
        opaq->hints = orig->hints;
        opaq->format = orig->format;
        if (orig->val_prefix_data) {
            ret = ly_dup_prefix_data(trg_ctx, opaq->format, orig->val_prefix_data, &opaq->val_prefix_data);
            LY_CHECK_GOTO(ret, error);
        }
    } else if (dup->schema->nodetype & LYD_NODE_TERM) {
        struct lyd_node_term *term = (struct lyd_node_term *)dup;
        struct lyd_node_term *orig = (struct lyd_node_term *)node;

        term->hash = orig->hash;
        if (trg_ctx == LYD_CTX(node)) {
            ret = orig->value.realtype->plugin->duplicate(trg_ctx, &orig->value, &term->value);
            LY_CHECK_ERR_GOTO(ret, LOGERR(trg_ctx, ret, "Value duplication failed."), error);
        } else {
            /* store canonical value in the target context */
            val_can = lyd_get_value(node);
            type = ((struct lysc_node_leaf *)term->schema)->type;
            ret = lyd_value_store(trg_ctx, &term->value, type, val_can, strlen(val_can), NULL, LY_VALUE_CANON, NULL,
                    LYD_HINT_DATA, term->schema, NULL);
            LY_CHECK_GOTO(ret, error);
        }
    } else if (dup->schema->nodetype & LYD_NODE_INNER) {
        struct lyd_node_inner *orig = (struct lyd_node_inner *)node;
        struct lyd_node *child;

        if (options & LYD_DUP_RECURSIVE) {
            /* duplicate all the children */
            LY_LIST_FOR(orig->child, child) {
                LY_CHECK_GOTO(ret = lyd_dup_r(child, trg_ctx, dup, 1, NULL, options, NULL), error);
            }
        } else if ((dup->schema->nodetype == LYS_LIST) && !(dup->schema->flags & LYS_KEYLESS)) {
            /* always duplicate keys of a list */
            for (child = orig->child; child && lysc_is_key(child->schema); child = child->next) {
                LY_CHECK_GOTO(ret = lyd_dup_r(child, trg_ctx, dup, 1, NULL, options, NULL), error);
            }
        }
        lyd_hash(dup);
    } else if (dup->schema->nodetype & LYD_NODE_ANY) {
        dup->hash = node->hash;
        any = (struct lyd_node_any *)node;
        LY_CHECK_GOTO(ret = lyd_any_copy_value(dup, &any->value, any->value_type), error);
    }

    /* insert */
    lyd_insert_node(parent, first, dup, insert_last);

    if (dup_p) {
        *dup_p = dup;
    }
    return LY_SUCCESS;

error:
    lyd_free_tree(dup);
    return ret;
}

/**
 * @brief Get a parent node to connect duplicated subtree to.
 *
 * @param[in] node Node (subtree) to duplicate.
 * @param[in] trg_ctx Target context for duplicated nodes.
 * @param[in] parent Initial parent to connect to.
 * @param[in] options Bitmask of options flags, see @ref dupoptions.
 * @param[out] dup_parent First duplicated parent node, if any.
 * @param[out] local_parent Correct parent to directly connect duplicated @p node to.
 * @return LY_ERR value.
 */
static LY_ERR
lyd_dup_get_local_parent(const struct lyd_node *node, const struct ly_ctx *trg_ctx, const struct lyd_node_inner *parent,
        uint32_t options, struct lyd_node **dup_parent, struct lyd_node_inner **local_parent)
{
    const struct lyd_node_inner *orig_parent, *iter;
    ly_bool repeat = 1;

    *dup_parent = NULL;
    *local_parent = NULL;

    for (orig_parent = node->parent; repeat && orig_parent; orig_parent = orig_parent->parent) {
        if (parent && (parent->schema == orig_parent->schema)) {
            /* stop creating parents, connect what we have into the provided parent */
            iter = parent;
            repeat = 0;
        } else {
            iter = NULL;
            LY_CHECK_RET(lyd_dup_r((struct lyd_node *)orig_parent, trg_ctx, NULL, 0, (struct lyd_node **)&iter, options,
                    (struct lyd_node **)&iter));
        }
        if (!*local_parent) {
            *local_parent = (struct lyd_node_inner *)iter;
        }
        if (iter->child) {
            /* 1) list - add after keys
             * 2) provided parent with some children */
            iter->child->prev->next = *dup_parent;
            if (*dup_parent) {
                (*dup_parent)->prev = iter->child->prev;
                iter->child->prev = *dup_parent;
            }
        } else {
            ((struct lyd_node_inner *)iter)->child = *dup_parent;
        }
        if (*dup_parent) {
            (*dup_parent)->parent = (struct lyd_node_inner *)iter;
        }
        *dup_parent = (struct lyd_node *)iter;
    }

    if (repeat && parent) {
        /* given parent and created parents chain actually do not interconnect */
        LOGERR(trg_ctx, LY_EINVAL,
                "Invalid argument parent (%s()) - does not interconnect with the created node's parents chain.", __func__);
        return LY_EINVAL;
    }

    return LY_SUCCESS;
}

static LY_ERR
lyd_dup(const struct lyd_node *node, const struct ly_ctx *trg_ctx, struct lyd_node_inner *parent, uint32_t options,
        ly_bool nosiblings, struct lyd_node **dup)
{
    LY_ERR rc;
    const struct lyd_node *orig;          /* original node to be duplicated */
    struct lyd_node *first = NULL;        /* the first duplicated node, this is returned */
    struct lyd_node *top = NULL;          /* the most higher created node */
    struct lyd_node_inner *local_parent = NULL; /* the direct parent node for the duplicated node(s) */

    assert(node && trg_ctx && (!parent || (LYD_CTX(parent) == trg_ctx)));

    if (options & LYD_DUP_WITH_PARENTS) {
        LY_CHECK_GOTO(rc = lyd_dup_get_local_parent(node, trg_ctx, parent, options & (LYD_DUP_WITH_FLAGS | LYD_DUP_NO_META),
                &top, &local_parent), error);
    } else {
        local_parent = parent;
    }

    LY_LIST_FOR(node, orig) {
        if (lysc_is_key(orig->schema)) {
            if (local_parent) {
                /* the key must already exist in the parent */
                rc = lyd_find_sibling_schema(local_parent->child, orig->schema, first ? NULL : &first);
                LY_CHECK_ERR_GOTO(rc, LOGINT(trg_ctx), error);
            } else {
                assert(!(options & LYD_DUP_WITH_PARENTS));
                /* duplicating a single key, okay, I suppose... */
                rc = lyd_dup_r(orig, trg_ctx, NULL, 0, &first, options, first ? NULL : &first);
                LY_CHECK_GOTO(rc, error);
            }
        } else {
            /* if there is no local parent, it will be inserted into first */
            rc = lyd_dup_r(orig, trg_ctx, local_parent ? &local_parent->node : NULL, 0, &first, options,
                    first ? NULL : &first);
            LY_CHECK_GOTO(rc, error);
        }
        if (nosiblings) {
            break;
        }
    }

    if (dup) {
        *dup = first;
    }
    return LY_SUCCESS;

error:
    if (top) {
        lyd_free_tree(top);
    } else {
        lyd_free_siblings(first);
    }
    return rc;
}

LIBYANG_API_DEF LY_ERR
lyd_dup_single(const struct lyd_node *node, struct lyd_node_inner *parent, uint32_t options, struct lyd_node **dup)
{
    LY_CHECK_ARG_RET(NULL, node, LY_EINVAL);
    if (node && parent && (LYD_CTX(node) != LYD_CTX(parent))) {
        LOGERR(NULL, LY_EINVAL, "Different contexts used in node duplication.");
        return LY_EINVAL;
    }

    return lyd_dup(node, LYD_CTX(node), parent, options, 1, dup);
}

LIBYANG_API_DEF LY_ERR
lyd_dup_single_to_ctx(const struct lyd_node *node, const struct ly_ctx *trg_ctx, struct lyd_node_inner *parent,
        uint32_t options, struct lyd_node **dup)
{
    LY_CHECK_ARG_RET(trg_ctx, node, trg_ctx, LY_EINVAL);

    return lyd_dup(node, trg_ctx, parent, options, 1, dup);
}

LIBYANG_API_DEF LY_ERR
lyd_dup_siblings(const struct lyd_node *node, struct lyd_node_inner *parent, uint32_t options, struct lyd_node **dup)
{
    LY_CHECK_ARG_RET(NULL, node, LY_EINVAL);
    if (node && parent && (LYD_CTX(node) != LYD_CTX(parent))) {
        LOGERR(NULL, LY_EINVAL, "Different contexts used in node duplication.");
        return LY_EINVAL;
    }

    return lyd_dup(node, LYD_CTX(node), parent, options, 0, dup);
}

LIBYANG_API_DEF LY_ERR
lyd_dup_siblings_to_ctx(const struct lyd_node *node, const struct ly_ctx *trg_ctx, struct lyd_node_inner *parent,
        uint32_t options, struct lyd_node **dup)
{
    LY_CHECK_ARG_RET(trg_ctx, node, trg_ctx, LY_EINVAL);

    return lyd_dup(node, trg_ctx, parent, options, 0, dup);
}

LIBYANG_API_DEF LY_ERR
lyd_dup_meta_single(const struct lyd_meta *meta, struct lyd_node *node, struct lyd_meta **dup)
{
    LY_ERR ret = LY_SUCCESS;
    struct lyd_meta *mt, *last;

    LY_CHECK_ARG_RET(NULL, meta, node, LY_EINVAL);

    /* create a copy */
    mt = calloc(1, sizeof *mt);
    LY_CHECK_ERR_RET(!mt, LOGMEM(LYD_CTX(node)), LY_EMEM);
    mt->annotation = meta->annotation;
    ret = meta->value.realtype->plugin->duplicate(LYD_CTX(node), &meta->value, &mt->value);
    LY_CHECK_ERR_GOTO(ret, LOGERR(LYD_CTX(node), LY_EINT, "Value duplication failed."), finish);
    LY_CHECK_GOTO(ret = lydict_insert(LYD_CTX(node), meta->name, 0, &mt->name), finish);

    /* insert as the last attribute */
    mt->parent = node;
    if (node->meta) {
        for (last = node->meta; last->next; last = last->next) {}
        last->next = mt;
    } else {
        node->meta = mt;
    }

finish:
    if (ret) {
        lyd_free_meta_single(mt);
    } else if (dup) {
        *dup = mt;
    }
    return LY_SUCCESS;
}

/**
 * @brief Merge a source sibling into target siblings.
 *
 * @param[in,out] first_trg First target sibling, is updated if top-level.
 * @param[in] parent_trg Target parent.
 * @param[in,out] sibling_src Source sibling to merge, set to NULL if spent.
 * @param[in] merge_cb Optional merge callback.
 * @param[in] cb_data Arbitrary callback data.
 * @param[in] options Merge options.
 * @param[in,out] dup_inst Duplicate instance cache for all @p first_trg siblings.
 * @return LY_ERR value.
 */
static LY_ERR
lyd_merge_sibling_r(struct lyd_node **first_trg, struct lyd_node *parent_trg, const struct lyd_node **sibling_src_p,
        lyd_merge_cb merge_cb, void *cb_data, uint16_t options, struct lyd_dup_inst **dup_inst)
{
    const struct lyd_node *child_src, *tmp, *sibling_src;
    struct lyd_node *match_trg, *dup_src, *elem;
    struct lyd_node_opaq *opaq_trg, *opaq_src;
    struct lysc_type *type;
    struct lyd_dup_inst *child_dup_inst = NULL;
    LY_ERR ret;
    ly_bool first_inst = 0;

    sibling_src = *sibling_src_p;
    if (!sibling_src->schema) {
        /* try to find the same opaque node */
        lyd_find_sibling_opaq_next(*first_trg, LYD_NAME(sibling_src), &match_trg);
    } else if (sibling_src->schema->nodetype & (LYS_LIST | LYS_LEAFLIST)) {
        /* try to find the exact instance */
        lyd_find_sibling_first(*first_trg, sibling_src, &match_trg);
    } else {
        /* try to simply find the node, there cannot be more instances */
        lyd_find_sibling_val(*first_trg, sibling_src->schema, NULL, 0, &match_trg);
    }

    if (match_trg) {
        /* update match as needed */
        LY_CHECK_RET(lyd_dup_inst_next(&match_trg, *first_trg, dup_inst));
    } else {
        /* first instance of this node */
        first_inst = 1;
    }

    if (match_trg) {
        /* call callback */
        if (merge_cb) {
            LY_CHECK_RET(merge_cb(match_trg, sibling_src, cb_data));
        }

        /* node found, make sure even value matches for all node types */
        if (!match_trg->schema) {
            if (lyd_compare_single(sibling_src, match_trg, 0)) {
                /* update value */
                opaq_trg = (struct lyd_node_opaq *)match_trg;
                opaq_src = (struct lyd_node_opaq *)sibling_src;

                lydict_remove(LYD_CTX(opaq_trg), opaq_trg->value);
                lydict_insert(LYD_CTX(opaq_trg), opaq_src->value, 0, &opaq_trg->value);
                opaq_trg->hints = opaq_src->hints;

                ly_free_prefix_data(opaq_trg->format, opaq_trg->val_prefix_data);
                opaq_trg->format = opaq_src->format;
                ly_dup_prefix_data(LYD_CTX(opaq_trg), opaq_src->format, opaq_src->val_prefix_data,
                        &opaq_trg->val_prefix_data);
            }
        } else if ((match_trg->schema->nodetype == LYS_LEAF) &&
                lyd_compare_single(sibling_src, match_trg, LYD_COMPARE_DEFAULTS)) {
            /* since they are different, they cannot both be default */
            assert(!(sibling_src->flags & LYD_DEFAULT) || !(match_trg->flags & LYD_DEFAULT));

            /* update value (or only LYD_DEFAULT flag) only if flag set or the source node is not default */
            if ((options & LYD_MERGE_DEFAULTS) || !(sibling_src->flags & LYD_DEFAULT)) {
                type = ((struct lysc_node_leaf *)match_trg->schema)->type;
                type->plugin->free(LYD_CTX(match_trg), &((struct lyd_node_term *)match_trg)->value);
                LY_CHECK_RET(type->plugin->duplicate(LYD_CTX(match_trg), &((struct lyd_node_term *)sibling_src)->value,
                        &((struct lyd_node_term *)match_trg)->value));

                /* copy flags and add LYD_NEW */
                match_trg->flags = sibling_src->flags | ((options & LYD_MERGE_WITH_FLAGS) ? 0 : LYD_NEW);
            }
        } else if ((match_trg->schema->nodetype & LYS_ANYDATA) && lyd_compare_single(sibling_src, match_trg, 0)) {
            /* update value */
            LY_CHECK_RET(lyd_any_copy_value(match_trg, &((struct lyd_node_any *)sibling_src)->value,
                    ((struct lyd_node_any *)sibling_src)->value_type));

            /* copy flags and add LYD_NEW */
            match_trg->flags = sibling_src->flags | ((options & LYD_MERGE_WITH_FLAGS) ? 0 : LYD_NEW);
        }

        /* check descendants, recursively */
        ret = LY_SUCCESS;
        LY_LIST_FOR_SAFE(lyd_child_no_keys(sibling_src), tmp, child_src) {
            ret = lyd_merge_sibling_r(lyd_node_child_p(match_trg), match_trg, &child_src, merge_cb, cb_data, options,
                    &child_dup_inst);
            if (ret) {
                break;
            }
        }
        lyd_dup_inst_free(child_dup_inst);
        LY_CHECK_RET(ret);
    } else {
        /* node not found, merge it */
        if (options & LYD_MERGE_DESTRUCT) {
            dup_src = (struct lyd_node *)sibling_src;
            lyd_unlink_tree(dup_src);
            /* spend it */
            *sibling_src_p = NULL;
        } else {
            LY_CHECK_RET(lyd_dup_single(sibling_src, NULL, LYD_DUP_RECURSIVE | LYD_DUP_WITH_FLAGS, &dup_src));
        }

        if (!(options & LYD_MERGE_WITH_FLAGS)) {
            /* set LYD_NEW for all the new nodes, required for validation */
            LYD_TREE_DFS_BEGIN(dup_src, elem) {
                elem->flags |= LYD_NEW;
                LYD_TREE_DFS_END(dup_src, elem);
            }
        }

        /* insert */
        lyd_insert_node(parent_trg, first_trg, dup_src, 0);

        if (first_inst) {
            /* remember not to find this instance next time */
            LY_CHECK_RET(lyd_dup_inst_next(&dup_src, *first_trg, dup_inst));
        }

        /* call callback, no source node */
        if (merge_cb) {
            LY_CHECK_RET(merge_cb(dup_src, NULL, cb_data));
        }
    }

    return LY_SUCCESS;
}

static LY_ERR
lyd_merge(struct lyd_node **target, const struct lyd_node *source, const struct lys_module *mod,
        lyd_merge_cb merge_cb, void *cb_data, uint16_t options, ly_bool nosiblings)
{
    const struct lyd_node *sibling_src, *tmp;
    struct lyd_dup_inst *dup_inst = NULL;
    ly_bool first;
    LY_ERR ret = LY_SUCCESS;

    LY_CHECK_ARG_RET(NULL, target, LY_EINVAL);
    LY_CHECK_CTX_EQUAL_RET(*target ? LYD_CTX(*target) : NULL, source ? LYD_CTX(source) : NULL, mod ? mod->ctx : NULL,
            LY_EINVAL);

    if (!source) {
        /* nothing to merge */
        return LY_SUCCESS;
    }

    if ((*target && lysc_data_parent((*target)->schema)) || lysc_data_parent(source->schema)) {
        LOGERR(LYD_CTX(source), LY_EINVAL, "Invalid arguments - can merge only 2 top-level subtrees (%s()).", __func__);
        return LY_EINVAL;
    }

    LY_LIST_FOR_SAFE(source, tmp, sibling_src) {
        if (mod && (lyd_owner_module(sibling_src) != mod)) {
            /* skip data nodes from different modules */
            continue;
        }

        first = (sibling_src == source) ? 1 : 0;
        ret = lyd_merge_sibling_r(target, NULL, &sibling_src, merge_cb, cb_data, options, &dup_inst);
        if (ret) {
            break;
        }
        if (first && !sibling_src) {
            /* source was spent (unlinked), move to the next node */
            source = tmp;
        }

        if (nosiblings) {
            break;
        }
    }

    if (options & LYD_MERGE_DESTRUCT) {
        /* free any leftover source data that were not merged */
        lyd_free_siblings((struct lyd_node *)source);
    }

    lyd_dup_inst_free(dup_inst);
    return ret;
}

LIBYANG_API_DEF LY_ERR
lyd_merge_tree(struct lyd_node **target, const struct lyd_node *source, uint16_t options)
{
    return lyd_merge(target, source, NULL, NULL, NULL, options, 1);
}

LIBYANG_API_DEF LY_ERR
lyd_merge_siblings(struct lyd_node **target, const struct lyd_node *source, uint16_t options)
{
    return lyd_merge(target, source, NULL, NULL, NULL, options, 0);
}

LIBYANG_API_DEF LY_ERR
lyd_merge_module(struct lyd_node **target, const struct lyd_node *source, const struct lys_module *mod,
        lyd_merge_cb merge_cb, void *cb_data, uint16_t options)
{
    return lyd_merge(target, source, mod, merge_cb, cb_data, options, 0);
}

static LY_ERR
lyd_path_str_enlarge(char **buffer, size_t *buflen, size_t reqlen, ly_bool is_static)
{
    /* ending \0 */
    ++reqlen;

    if (reqlen > *buflen) {
        if (is_static) {
            return LY_EINCOMPLETE;
        }

        *buffer = ly_realloc(*buffer, reqlen * sizeof **buffer);
        if (!*buffer) {
            return LY_EMEM;
        }

        *buflen = reqlen;
    }

    return LY_SUCCESS;
}

LY_ERR
lyd_path_list_predicate(const struct lyd_node *node, char **buffer, size_t *buflen, size_t *bufused, ly_bool is_static)
{
    const struct lyd_node *key;
    size_t len;
    const char *val;
    char quot;

    for (key = lyd_child(node); key && key->schema && (key->schema->flags & LYS_KEY); key = key->next) {
        val = lyd_get_value(key);
        len = 1 + strlen(key->schema->name) + 2 + strlen(val) + 2;
        LY_CHECK_RET(lyd_path_str_enlarge(buffer, buflen, *bufused + len, is_static));

        quot = '\'';
        if (strchr(val, '\'')) {
            quot = '"';
        }
        *bufused += sprintf(*buffer + *bufused, "[%s=%c%s%c]", key->schema->name, quot, val, quot);
    }

    return LY_SUCCESS;
}

/**
 * @brief Append leaf-list value predicate to path.
 *
 * @param[in] node Node to print.
 * @param[in,out] buffer Buffer to print to.
 * @param[in,out] buflen Current buffer length.
 * @param[in,out] bufused Current number of characters used in @p buffer.
 * @param[in] is_static Whether buffer is static or can be reallocated.
 * @return LY_ERR
 */
static LY_ERR
lyd_path_leaflist_predicate(const struct lyd_node *node, char **buffer, size_t *buflen, size_t *bufused, ly_bool is_static)
{
    size_t len;
    const char *val;
    char quot;

    val = lyd_get_value(node);
    len = 4 + strlen(val) + 2; /* "[.='" + val + "']" */
    LY_CHECK_RET(lyd_path_str_enlarge(buffer, buflen, *bufused + len, is_static));

    quot = '\'';
    if (strchr(val, '\'')) {
        quot = '"';
    }
    *bufused += sprintf(*buffer + *bufused, "[.=%c%s%c]", quot, val, quot);

    return LY_SUCCESS;
}

/**
 * @brief Append node position (relative to its other instances) predicate to path.
 *
 * @param[in] node Node to print.
 * @param[in,out] buffer Buffer to print to.
 * @param[in,out] buflen Current buffer length.
 * @param[in,out] bufused Current number of characters used in @p buffer.
 * @param[in] is_static Whether buffer is static or can be reallocated.
 * @return LY_ERR
 */
static LY_ERR
lyd_path_position_predicate(const struct lyd_node *node, char **buffer, size_t *buflen, size_t *bufused, ly_bool is_static)
{
    size_t len;
    uint32_t pos;
    char *val = NULL;
    LY_ERR rc;

    pos = lyd_list_pos(node);
    if (asprintf(&val, "%" PRIu32, pos) == -1) {
        return LY_EMEM;
    }

    len = 1 + strlen(val) + 1;
    rc = lyd_path_str_enlarge(buffer, buflen, *bufused + len, is_static);
    if (rc != LY_SUCCESS) {
        goto cleanup;
    }

    *bufused += sprintf(*buffer + *bufused, "[%s]", val);

cleanup:
    free(val);
    return rc;
}

LIBYANG_API_DEF char *
lyd_path(const struct lyd_node *node, LYD_PATH_TYPE pathtype, char *buffer, size_t buflen)
{
    ly_bool is_static = 0;
    uint32_t i, depth;
    size_t bufused = 0, len;
    const struct lyd_node *iter, *parent;
    const struct lys_module *mod, *prev_mod;
    LY_ERR rc = LY_SUCCESS;

    LY_CHECK_ARG_RET(NULL, node, NULL);
    if (buffer) {
        LY_CHECK_ARG_RET(LYD_CTX(node), buflen > 1, NULL);
        is_static = 1;
    } else {
        buflen = 0;
    }

    switch (pathtype) {
    case LYD_PATH_STD:
    case LYD_PATH_STD_NO_LAST_PRED:
        depth = 1;
        for (iter = node; iter->parent; iter = lyd_parent(iter)) {
            ++depth;
        }

        goto iter_print;
        while (depth) {
            /* find the right node */
            for (iter = node, i = 1; i < depth; iter = lyd_parent(iter), ++i) {}
iter_print:
            /* get the module */
            mod = iter->schema ? iter->schema->module : lyd_owner_module(iter);
            parent = lyd_parent(iter);
            prev_mod = (parent && parent->schema) ? parent->schema->module : lyd_owner_module(parent);
            if (prev_mod == mod) {
                mod = NULL;
            }

            /* realloc string */
            len = 1 + (mod ? strlen(mod->name) + 1 : 0) + (iter->schema ? strlen(iter->schema->name) :
                    strlen(((struct lyd_node_opaq *)iter)->name.name));
            rc = lyd_path_str_enlarge(&buffer, &buflen, bufused + len, is_static);
            if (rc != LY_SUCCESS) {
                break;
            }

            /* print next node */
            bufused += sprintf(buffer + bufused, "/%s%s%s", mod ? mod->name : "", mod ? ":" : "",
                    iter->schema ? iter->schema->name : ((struct lyd_node_opaq *)iter)->name.name);

            /* do not always print the last (first) predicate */
            if (iter->schema && ((depth > 1) || (pathtype == LYD_PATH_STD))) {
                switch (iter->schema->nodetype) {
                case LYS_LIST:
                    if (iter->schema->flags & LYS_KEYLESS) {
                        /* print its position */
                        rc = lyd_path_position_predicate(iter, &buffer, &buflen, &bufused, is_static);
                    } else {
                        /* print all list keys in predicates */
                        rc = lyd_path_list_predicate(iter, &buffer, &buflen, &bufused, is_static);
                    }
                    break;
                case LYS_LEAFLIST:
                    if (iter->schema->flags & LYS_CONFIG_W) {
                        /* print leaf-list value */
                        rc = lyd_path_leaflist_predicate(iter, &buffer, &buflen, &bufused, is_static);
                    } else {
                        /* print its position */
                        rc = lyd_path_position_predicate(iter, &buffer, &buflen, &bufused, is_static);
                    }
                    break;
                default:
                    /* nothing to print more */
                    break;
                }
            }
            if (rc != LY_SUCCESS) {
                break;
            }

            --depth;
        }
        break;
    }

    return buffer;
}

LIBYANG_API_DEF struct lyd_meta *
lyd_find_meta(const struct lyd_meta *first, const struct lys_module *module, const char *name)
{
    struct lyd_meta *ret = NULL;
    const struct ly_ctx *ctx;
    const char *prefix, *tmp;
    char *str;
    size_t pref_len, name_len;

    LY_CHECK_ARG_RET(NULL, module || strchr(name, ':'), name, NULL);
    LY_CHECK_CTX_EQUAL_RET(first ? first->annotation->module->ctx : NULL, module ? module->ctx : NULL, NULL);

    if (!first) {
        return NULL;
    }

    ctx = first->annotation->module->ctx;

    /* parse the name */
    tmp = name;
    if (ly_parse_nodeid(&tmp, &prefix, &pref_len, &name, &name_len) || tmp[0]) {
        LOGERR(ctx, LY_EINVAL, "Metadata name \"%s\" is not valid.", name);
        return NULL;
    }

    /* find the module */
    if (prefix) {
        str = strndup(prefix, pref_len);
        module = ly_ctx_get_module_latest(ctx, str);
        free(str);
        LY_CHECK_ERR_RET(!module, LOGERR(ctx, LY_EINVAL, "Module \"%.*s\" not found.", (int)pref_len, prefix), NULL);
    }

    /* find the metadata */
    LY_LIST_FOR(first, first) {
        if ((first->annotation->module == module) && !strcmp(first->name, name)) {
            ret = (struct lyd_meta *)first;
            break;
        }
    }

    return ret;
}

LIBYANG_API_DEF LY_ERR
lyd_find_sibling_first(const struct lyd_node *siblings, const struct lyd_node *target, struct lyd_node **match)
{
    struct lyd_node **match_p, *iter, *dup = NULL;
    struct lyd_node_inner *parent;
    ly_bool found;

    LY_CHECK_ARG_RET(NULL, target, LY_EINVAL);
    if (!siblings) {
        /* no data */
        if (match) {
            *match = NULL;
        }
        return LY_ENOTFOUND;
    }

    if (LYD_CTX(siblings) != LYD_CTX(target)) {
        /* create a duplicate in this context */
        LY_CHECK_RET(lyd_dup_single_to_ctx(target, LYD_CTX(siblings), NULL, 0, &dup));
        target = dup;
    }

    if ((siblings->schema && target->schema && (lysc_data_parent(siblings->schema) != lysc_data_parent(target->schema)))) {
        /* schema mismatch */
        lyd_free_tree(dup);
        if (match) {
            *match = NULL;
        }
        return LY_ENOTFOUND;
    }

    /* get first sibling */
    siblings = lyd_first_sibling(siblings);

    parent = siblings->parent;
    if (parent && parent->schema && parent->children_ht) {
        assert(target->hash);

        if (lysc_is_dup_inst_list(target->schema)) {
            /* we must search the instances from beginning to find the first matching one */
            found = 0;
            LYD_LIST_FOR_INST(siblings, target->schema, iter) {
                if (!lyd_compare_single(target, iter, 0)) {
                    found = 1;
                    break;
                }
            }
            if (found) {
                siblings = iter;
            } else {
                siblings = NULL;
            }
        } else {
            /* find by hash */
            if (!lyht_find(parent->children_ht, &target, target->hash, (void **)&match_p)) {
                siblings = *match_p;
            } else {
                /* not found */
                siblings = NULL;
            }
        }
    } else {
        /* no children hash table */
        for ( ; siblings; siblings = siblings->next) {
            if (!lyd_compare_single(siblings, target, 0)) {
                break;
            }
        }
    }

    lyd_free_tree(dup);
    if (!siblings) {
        if (match) {
            *match = NULL;
        }
        return LY_ENOTFOUND;
    }

    if (match) {
        *match = (struct lyd_node *)siblings;
    }
    return LY_SUCCESS;
}

LIBYANG_API_DEF LY_ERR
lyd_find_sibling_val(const struct lyd_node *siblings, const struct lysc_node *schema, const char *key_or_value,
        size_t val_len, struct lyd_node **match)
{
    LY_ERR rc;
    struct lyd_node *target = NULL;
    const struct lyd_node *parent;

    LY_CHECK_ARG_RET(NULL, schema, !(schema->nodetype & (LYS_CHOICE | LYS_CASE)), LY_EINVAL);
    if (!siblings) {
        /* no data */
        if (match) {
            *match = NULL;
        }
        return LY_ENOTFOUND;
    }

    if ((LYD_CTX(siblings) != schema->module->ctx)) {
        /* parent of ext nodes is useless */
        parent = (siblings->flags & LYD_EXT) ? NULL : lyd_parent(siblings);
        LY_CHECK_RET(lyd_dup_find_schema(schema, LYD_CTX(siblings), parent, &schema));
    }

    if (siblings->schema && (lysc_data_parent(siblings->schema) != lysc_data_parent(schema))) {
        /* schema mismatch */
        if (match) {
            *match = NULL;
        }
        return LY_ENOTFOUND;
    }

    if (key_or_value && !val_len) {
        val_len = strlen(key_or_value);
    }

    if ((schema->nodetype & (LYS_LIST | LYS_LEAFLIST)) && key_or_value) {
        /* create a data node and find the instance */
        if (schema->nodetype == LYS_LEAFLIST) {
            /* target used attributes: schema, hash, value */
            rc = lyd_create_term(schema, key_or_value, val_len, NULL, LY_VALUE_JSON, NULL, LYD_HINT_DATA, NULL, &target);
            LY_CHECK_RET(rc);
        } else {
            /* target used attributes: schema, hash, child (all keys) */
            LY_CHECK_RET(lyd_create_list2(schema, key_or_value, val_len, &target));
        }

        /* find it */
        rc = lyd_find_sibling_first(siblings, target, match);
    } else {
        /* find the first schema node instance */
        rc = lyd_find_sibling_schema(siblings, schema, match);
    }

    lyd_free_tree(target);
    return rc;
}

LIBYANG_API_DEF LY_ERR
lyd_find_sibling_dup_inst_set(const struct lyd_node *siblings, const struct lyd_node *target, struct ly_set **set)
{
    struct lyd_node **match_p, *first, *iter;
    struct lyd_node_inner *parent;

    LY_CHECK_ARG_RET(NULL, target, set, LY_EINVAL);
    LY_CHECK_CTX_EQUAL_RET(siblings ? LYD_CTX(siblings) : NULL, LYD_CTX(target), LY_EINVAL);

    LY_CHECK_RET(ly_set_new(set));

    if (!siblings || (siblings->schema && (lysc_data_parent(siblings->schema) != lysc_data_parent(target->schema)))) {
        /* no data or schema mismatch */
        return LY_ENOTFOUND;
    }

    /* get first sibling */
    siblings = lyd_first_sibling(siblings);

    parent = siblings->parent;
    if (parent && parent->schema && parent->children_ht) {
        assert(target->hash);

        /* find the first instance */
        lyd_find_sibling_first(siblings, target, &first);
        if (first) {
            /* add it so that it is the first in the set */
            if (ly_set_add(*set, first, 1, NULL)) {
                goto error;
            }

            /* find by hash */
            if (!lyht_find(parent->children_ht, &target, target->hash, (void **)&match_p)) {
                iter = *match_p;
            } else {
                /* not found */
                iter = NULL;
            }
            while (iter) {
                /* add all found nodes into the set */
                if ((iter != first) && !lyd_compare_single(iter, target, 0) && ly_set_add(*set, iter, 1, NULL)) {
                    goto error;
                }

                /* find next instance */
                if (lyht_find_next(parent->children_ht, &iter, iter->hash, (void **)&match_p)) {
                    iter = NULL;
                } else {
                    iter = *match_p;
                }
            }
        }
    } else {
        /* no children hash table */
        LY_LIST_FOR(siblings, siblings) {
            if (!lyd_compare_single(target, siblings, 0)) {
                ly_set_add(*set, (void *)siblings, 1, NULL);
            }
        }
    }

    if (!(*set)->count) {
        return LY_ENOTFOUND;
    }
    return LY_SUCCESS;

error:
    ly_set_free(*set, NULL);
    *set = NULL;
    return LY_EMEM;
}

LIBYANG_API_DEF LY_ERR
lyd_find_sibling_opaq_next(const struct lyd_node *first, const char *name, struct lyd_node **match)
{
    LY_CHECK_ARG_RET(NULL, name, LY_EINVAL);

    for ( ; first; first = first->next) {
        if (!first->schema && !strcmp(LYD_NAME(first), name)) {
            break;
        }
    }

    if (match) {
        *match = (struct lyd_node *)first;
    }
    return first ? LY_SUCCESS : LY_ENOTFOUND;
}

LIBYANG_API_DEF LY_ERR
lyd_find_xpath4(const struct lyd_node *ctx_node, const struct lyd_node *tree, const char *xpath, LY_VALUE_FORMAT format,
        void *prefix_data, const struct lyxp_var *vars, struct ly_set **set)
{
    LY_ERR ret = LY_SUCCESS;
    struct lyxp_set xp_set = {0};
    struct lyxp_expr *exp = NULL;
    uint32_t i;

    LY_CHECK_ARG_RET(NULL, tree, xpath, format, set, LY_EINVAL);

    *set = NULL;

    /* parse expression */
    ret = lyxp_expr_parse((struct ly_ctx *)LYD_CTX(tree), xpath, 0, 1, &exp);
    LY_CHECK_GOTO(ret, cleanup);

    /* evaluate expression */
    ret = lyxp_eval(LYD_CTX(tree), exp, NULL, format, prefix_data, ctx_node, tree, vars, &xp_set, LYXP_IGNORE_WHEN);
    LY_CHECK_GOTO(ret, cleanup);

    /* allocate return set */
    ret = ly_set_new(set);
    LY_CHECK_GOTO(ret, cleanup);

    /* transform into ly_set */
    if (xp_set.type == LYXP_SET_NODE_SET) {
        /* allocate memory for all the elements once (even though not all items must be elements but most likely will be) */
        (*set)->objs = malloc(xp_set.used * sizeof *(*set)->objs);
        LY_CHECK_ERR_GOTO(!(*set)->objs, LOGMEM(LYD_CTX(tree)); ret = LY_EMEM, cleanup);
        (*set)->size = xp_set.used;

        for (i = 0; i < xp_set.used; ++i) {
            if (xp_set.val.nodes[i].type == LYXP_NODE_ELEM) {
                ret = ly_set_add(*set, xp_set.val.nodes[i].node, 1, NULL);
                LY_CHECK_GOTO(ret, cleanup);
            }
        }
    }

cleanup:
    lyxp_set_free_content(&xp_set);
    lyxp_expr_free((struct ly_ctx *)LYD_CTX(tree), exp);
    if (ret) {
        ly_set_free(*set, NULL);
        *set = NULL;
    }
    return ret;
}

LIBYANG_API_DEF LY_ERR
lyd_find_xpath3(const struct lyd_node *ctx_node, const struct lyd_node *tree, const char *xpath,
        const struct lyxp_var *vars, struct ly_set **set)
{
    LY_CHECK_ARG_RET(NULL, tree, xpath, set, LY_EINVAL);

    return lyd_find_xpath4(ctx_node, tree, xpath, LY_VALUE_JSON, NULL, vars, set);
}

LIBYANG_API_DEF LY_ERR
lyd_find_xpath2(const struct lyd_node *ctx_node, const char *xpath, const struct lyxp_var *vars, struct ly_set **set)
{
    LY_CHECK_ARG_RET(NULL, ctx_node, xpath, set, LY_EINVAL);

    return lyd_find_xpath4(ctx_node, ctx_node, xpath, LY_VALUE_JSON, NULL, vars, set);
}

LIBYANG_API_DEF LY_ERR
lyd_find_xpath(const struct lyd_node *ctx_node, const char *xpath, struct ly_set **set)
{
    LY_CHECK_ARG_RET(NULL, ctx_node, xpath, set, LY_EINVAL);

    return lyd_find_xpath4(ctx_node, ctx_node, xpath, LY_VALUE_JSON, NULL, NULL, set);
}

LIBYANG_API_DEF LY_ERR
lyd_eval_xpath2(const struct lyd_node *ctx_node, const char *xpath, const struct lyxp_var *vars, ly_bool *result)
{
    LY_ERR ret = LY_SUCCESS;
    struct lyxp_set xp_set = {0};
    struct lyxp_expr *exp = NULL;

    LY_CHECK_ARG_RET(NULL, ctx_node, xpath, result, LY_EINVAL);

    /* compile expression */
    ret = lyxp_expr_parse((struct ly_ctx *)LYD_CTX(ctx_node), xpath, 0, 1, &exp);
    LY_CHECK_GOTO(ret, cleanup);

    /* evaluate expression */
    ret = lyxp_eval(LYD_CTX(ctx_node), exp, NULL, LY_VALUE_JSON, NULL, ctx_node, ctx_node, vars, &xp_set, LYXP_IGNORE_WHEN);
    LY_CHECK_GOTO(ret, cleanup);

    /* transform into boolean */
    ret = lyxp_set_cast(&xp_set, LYXP_SET_BOOLEAN);
    LY_CHECK_GOTO(ret, cleanup);

    /* set result */
    *result = xp_set.val.bln;

cleanup:
    lyxp_set_free_content(&xp_set);
    lyxp_expr_free((struct ly_ctx *)LYD_CTX(ctx_node), exp);
    return ret;
}

LIBYANG_API_DEF LY_ERR
lyd_eval_xpath(const struct lyd_node *ctx_node, const char *xpath, ly_bool *result)
{
    return lyd_eval_xpath2(ctx_node, xpath, NULL, result);
}

LIBYANG_API_DEF LY_ERR
lyd_find_path(const struct lyd_node *ctx_node, const char *path, ly_bool output, struct lyd_node **match)
{
    LY_ERR ret = LY_SUCCESS;
    struct lyxp_expr *expr = NULL;
    struct ly_path *lypath = NULL;

    LY_CHECK_ARG_RET(NULL, ctx_node, ctx_node->schema, path, LY_EINVAL);

    /* parse the path */
    ret = ly_path_parse(LYD_CTX(ctx_node), ctx_node->schema, path, strlen(path), 0, LY_PATH_BEGIN_EITHER,
            LY_PATH_PREFIX_OPTIONAL, LY_PATH_PRED_SIMPLE, &expr);
    LY_CHECK_GOTO(ret, cleanup);

    /* compile the path */
    ret = ly_path_compile(LYD_CTX(ctx_node), NULL, ctx_node->schema, NULL, expr,
            output ? LY_PATH_OPER_OUTPUT : LY_PATH_OPER_INPUT, LY_PATH_TARGET_SINGLE, 0, LY_VALUE_JSON, NULL, &lypath);
    LY_CHECK_GOTO(ret, cleanup);

    /* evaluate the path */
    ret = ly_path_eval_partial(lypath, ctx_node, NULL, match);

cleanup:
    lyxp_expr_free(LYD_CTX(ctx_node), expr);
    ly_path_free(LYD_CTX(ctx_node), lypath);
    return ret;
}

LIBYANG_API_DEF LY_ERR
lyd_find_target(const struct ly_path *path, const struct lyd_node *tree, struct lyd_node **match)
{
    LY_ERR ret;
    struct lyd_node *m;

    LY_CHECK_ARG_RET(NULL, path, LY_EINVAL);

    ret = ly_path_eval(path, tree, &m);
    if (ret) {
        if (match) {
            *match = NULL;
        }
        return LY_ENOTFOUND;
    }

    if (match) {
        *match = m;
    }
    return LY_SUCCESS;
}