/**
 * @file extesnions.h
 * @author Radek Krejci <rkrejci@cesnet.cz>
 * @brief libyang support for YANG extensions implementation.
 *
 * Copyright (c) 2015 - 2018 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
 */

#ifndef LY_EXTENSIONS_H_
#define LY_EXTENSIONS_H_

#include "set.h"
#include "tree_schema.h"

#ifdef __cplusplus
extern "C" {
#endif


/**
 * @defgroup extensions YANG Extensions
 *
 * @{
 */

/**
 * @defgroup extensionscompile YANG Extensions - Compilation Helpers
 * @ingroup extensions
 * @brief Helper functions to compile (via lyext_clb_compile callback) statements inside the extension instance.
 *
 * NOTE: There is a lot of useful static functions in the tree_schema_compile.c which could be provided here. Since we don't want
 * to have a large API with functions which will be never used, we provide here just the functions which are evidently needed.
 * If you, as an extension plugin author, need to make some of the compile functions available, please contact libyang maintainers
 * via the GITHUB issue tracker.
 *
 * @{
 */

/**
 * @brief internal context for compilation
 */
struct lysc_ctx {
    struct ly_ctx *ctx;
    struct lys_module *mod;
    struct lys_module *mod_def; /**< context module for the definitions of the nodes being currently
                                     processed - groupings are supposed to be evaluated in place where
                                     defined, but its content instances are supposed to be placed into
                                     the target module (mod) */
    struct ly_set groupings;    /**< stack for groupings circular check */
    struct ly_set unres;        /**< to validate leafref's target and xpath of when/must */
    struct ly_set dflts;        /**< set of incomplete default values */
    struct ly_set tpdf_chain;
    uint16_t path_len;
    int options;                /**< various @ref scflags. */
#define LYSC_CTX_BUFSIZE 4078
    char path[LYSC_CTX_BUFSIZE];
};

/**
 * @brief Update path in the compile context, which is used for logging where the compilation failed.
 *
 * @param[in] ctx Compile context with the path.
 * @param[in] parent Parent of the current node to check difference of the node's module. The current module is taken from lysc_ctx::mod.
 * @param[in] name Name of the node to update path with. If NULL, the last segment is removed. If the format is `{keyword}`, the following
 * call updates the segment to the form `{keyword='name'}` (to remove this compound segment, 2 calls with NULL @p name must be used).
 */
void lysc_update_path(struct lysc_ctx *ctx, struct lysc_node *parent, const char *name);

/** @} extensionscompile */

/**
 * @brief Callback to compile extension from the lysp_ext_instance to the lysc_ext_instance. The later structure is generally prepared
 * and only the extension specific data are supposed to be added (if any).
 *
 * @param[in] cctx Current compile context.
 * @param[in] p_ext Parsed extension instance data.
 * @param[in,out] c_ext Prepared compiled extension instance structure where an addition, extension-specific, data are supposed to be placed
 * for later use (data validation or use of external tool).
 * @return LY_SUCCESS in case of success.
 * @return LY_EVALID in case of non-conforming parsed data.
 */
typedef LY_ERR (*lyext_clb_compile)(struct lysc_ctx *cctx, const struct lysp_ext_instance *p_ext, struct lysc_ext_instance *c_ext);

/**
 * @brief Callback to free the extension specific data created by the lyext_clb_compile callback of the same extension plugin.
 *
 * @param[in,out] ext Compiled extension structure where the data to free are placed.
 */
typedef void (*lyext_clb_free)(struct lysc_ext_instance *ext);

/**
 * @brief Callback to decide if data instance is valid according to the schema.
 *
 * The callback is used only for the extension instances placed in the following parent statements
 * (which is specified as lysc_ext_instance::parent_type):
 *     - LYEXT_PAR_NODE - @p node is instance of the schema node where the extension instance was specified.
 *     - LYEXT_PAR_TPDF - @p node is instance of the schema node with the value of the typedef's type where the extension instance was specified.
 *     - LYEXT_PAR_TYPE - @p node is instance of the schema node with the value of the type where the extension instance was specified.
 *     - LYEXT_PAR_TYPE_BIT - @p node is instance of the schema node with the value of the bit where the extension instance was specified.
 *     - LYEXT_PAR_TYPE_ENUM - @p node is instance of the schema node with the value of the enum where the extension instance was specified.
 *
 * @param[in] ext Extension instance to be checked.
 * @param[in] node Data node, where the extension data are supposed to be placed.
 *
 * @return LY_SUCCESS on data validation success.
 * @return LY_EVALID in case the validation fails.
 */
typedef LY_ERR (*lyext_clb_data_validation)(struct lysc_ext_instance *ext, struct lyd_node *node);

/**
 * @brief Extension plugin implementing various aspects of a YANG extension
 */
struct lyext_plugin {
    const char *id;                     /**< Plugin identification (mainly for distinguish incompatible versions of the plugins for external tools) */
    lyext_clb_compile compile;          /**< Callback to compile extension instance from the parsed data */
    lyext_clb_data_validation validate; /**< Callback to decide if data instance is valid according to the schema. */
    /* TODO printers? (schema/data) */
    lyext_clb_free free;                /**< Free the extension instance specific data created by lyext_plugin::compile callback */
};

/** @} extensions */

#ifdef __cplusplus
}
#endif

#endif /* LY_TREE_SCHEMA_H_ */