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+/**
+ * @file log.h
+ * @author Radek Krejci <rkrejci@cesnet.cz>
+ * @brief Logger manipulation routines and error definitions.
+ *
+ * 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_LOG_H_
+#define LY_LOG_H_
+
+#include "libyang.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @defgroup log Logger
+ * @{
+ *
+ * Publicly visible functions and values of the libyang logger. For more
+ * information, see \ref howtologger.
+ */
+
+/**
+ * @typedef LY_LOG_LEVEL
+ * @brief Verbosity levels of the libyang logger.
+ */
+typedef enum
+{
+ LY_LLERR = 0, /**< Print only error messages, default value. */
+ LY_LLWRN = 1, /**< Print error and warning messages. */
+ LY_LLVRB = 2, /**< Besides errors and warnings, print some other verbose messages. */
+ LY_LLDBG = 3 /**< Print all messages including some development debug messages (be careful,
+ without subsequently calling ly_verb_dbg() no debug messages will be printed!). */
+} LY_LOG_LEVEL;
+
+/**
+ * @brief Set logger verbosity level.
+ * @param[in] level Verbosity level.
+ * @return Previous verbosity level.
+ */
+LY_LOG_LEVEL ly_verb (LY_LOG_LEVEL level);
+
+/**
+ * @defgroup logopts Logging options
+ * @ingroup logger
+ *
+ * Logging option bits of libyang.
+ *
+ * @{
+ */
+#define LY_LOLOG 0x01 /**< Log messages normally, using callback if set. If not set, messages will
+ not be printed by libyang. */
+#define LY_LOSTORE 0x02 /**< Store any generated errors or warnings, never verbose or debug messages.
+ Note that if #LY_LOLOG is not set then verbose and debug messages are always lost. */
+#define LY_LOSTORE_LAST 0x06 /**< Store any generated errors or warnings but only the last message, always overwrite
+ the previous one. */
+
+/**
+ * @}
+ */
+
+/**
+ * @brief Set additional logger options. Default is #LY_LOLOG | #LY_LOSTORE_LAST.
+ *
+ * @param[in] opts Bitfield of @ref logopts.
+ * @return Previous logger options.
+ */
+int ly_log_options (int opts);
+
+#ifndef NDEBUG
+
+/**
+ * @defgroup dbggroup Debug message groups
+ * @ingroup log
+ *
+ * Selected displayed debug message groups.
+ *
+ * @{
+ */
+
+#define LY_LDGDICT 0x01 /**< Dictionary additions and deletions. */
+#define LY_LDGYANG 0x02 /**< YANG parser messages. */
+#define LY_LDGYIN 0x04 /**< YIN parser messages. */
+#define LY_LDGXPATH 0x08 /**< XPath parsing end evaluation. */
+#define LY_LDGDIFF 0x10 /**< Diff processing and creation. */
+
+/**
+ * @}
+ */
+
+/**
+ * @brief Enable specific debugging messages (independent of log level).
+ * @param[in] dbg_groups Bitfield of enabled debug message groups (see @ref dbggroup).
+ */
+void ly_verb_dbg (int dbg_groups);
+
+#endif
+
+/**
+ * @brief Set logger callback.
+ *
+ * !IMPORTANT! If an error has a specific error-app-tag defined in the model, it will NOT be set
+ * at the time of calling this callback. It will be set right after, so to retrieve it
+ * it must be checked afterwards with ly_errapptag().
+ *
+ * @param[in] clb Logging callback.
+ * @param[in] path flag to resolve and provide path as the third parameter of the callback function. In case of
+ * validation and some other errors, it can be useful to get the path to the problematic element. Note,
+ * that according to the tree type and the specific situation, the path can slightly differs (keys
+ * presence) or it can be NULL, so consider it as an optional parameter. If the flag is 0, libyang will
+ * not bother with resolving the path.
+ */
+void ly_set_log_clb (void(*clb) (LY_LOG_LEVEL level, const char *msg, const char *path), int path);
+
+/**
+ * @brief Get logger callback.
+ * @return Logger callback (can be NULL).
+ */
+void (*ly_get_log_clb (void)) (LY_LOG_LEVEL, const char *, const char *);
+
+/** @} log */
+
+/**
+ * @defgroup errors Error information
+ * @{
+ */
+
+/**
+ * @typedef LY_ERR
+ * @brief libyang's error codes returned by the libyang functions.
+ */
+typedef enum
+{
+ LY_SUCCESS = 0, /**< no error, not set by functions, included just to complete #LY_ERR enumeration */
+ LY_EMEM, /**< Memory allocation failure */
+ LY_EINVAL, /**< Invalid value */
+ LY_EEXIST, /**< Item already exists */
+ LY_EINT, /**< Internal error */
+ LY_EVALID, /**< Validation failure */
+ LY_EPLUGIN /**< Error reported by a plugin */
+} LY_ERR;
+
+/**
+ * @typedef LY_VECODE
+ * @brief libyang's codes of validation error. Whenever ly_errno is set to LY_EVALID, the ly_vecode is also set
+ * to the appropriate LY_VECODE value.
+ * @ingroup logger
+ */
+typedef enum {
+ LYVE_SUCCESS = 0, /**< no error */
+} LY_VECODE;
+
+/**
+ * @brief Libyang full error structure.
+ */
+struct ly_err_item {
+ LY_LOG_LEVEL level;
+ LY_ERR no;
+ LY_VECODE vecode;
+ char *msg;
+ char *path;
+ char *apptag;
+ struct ly_err_item *next;
+ struct ly_err_item *prev; /* first item's prev points to the last item */
+};
+
+/**
+ * @brief Get the last (thread, context-specific) validation error code.
+ *
+ * This value is set only if ly_errno is #LY_EVALID.
+ *
+ * @param[in] ctx Relative context.
+ * @return Validation error code.
+ */
+LY_VECODE ly_vecode(const struct ly_ctx *ctx);
+
+/**
+ * @brief Get the last (thread, context-specific) error message. If the coresponding module defined
+ * a specific error message, it will be used instead the default one.
+ *
+ * Sometimes, the error message is extended with path of the element where the problem is.
+ * The path is available via ly_errpath().
+ *
+ * @param[in] ctx Relative context.
+ * @return Text of the last error message, empty string if there is no error.
+ */
+const char *ly_errmsg(const struct ly_ctx *ctx);
+
+/**
+ * @brief Get the last (thread, context-specific) path of the element where was an error.
+ *
+ * The path always corresponds to the error message available via ly_errmsg(), so
+ * whenever a subsequent error message is printed, the path is erased or rewritten.
+ * The path reflects the type of the processed tree - data path for data tree functions
+ * and schema path in case of schema tree functions. In case of processing YIN schema
+ * or XML data, the path can be just XML path. In such a case, the corresponding
+ * ly_vecode (value 1-3) is set.
+ *
+ * @param[in] ctx Relative context.
+ * @return Path of the error element, empty string if error path does not apply to the last error.
+ */
+const char *ly_errpath(const struct ly_ctx *ctx);
+
+/**
+ * @brief Get the last (thread, context-specific) error-app-tag if there was a specific one defined
+ * in the module for the last error.
+ *
+ * The app-tag always corresponds to the error message available via ly_errmsg(), so
+ * whenever a subsequent error message is printed, the app-tag is erased or rewritten.
+ *
+ * @param[in] ctx Relative context.
+ * @return Error-app-tag of the last error, empty string if the error-app-tag does not apply to the last error.
+ */
+const char *ly_errapptag(const struct ly_ctx *ctx);
+
+/**
+ * @brief Get the first (thread, context-specific) generated error structure.
+ *
+ * @param[in] ctx Relative context.
+ * @return First error structure (can be NULL), do not modify!
+ */
+struct ly_err_item *ly_err_first(const struct ly_ctx *ctx);
+
+/**
+ * @brief Print the error structure as if just generated.
+ *
+ * @param[in] eitem Error item structure to print.
+ */
+void ly_err_print(struct ly_err_item *eitem);
+
+/**
+ * @brief Free error structures from a context.
+ *
+ * If \p eitem is not set, free all the error structures.
+ *
+ * @param[in] ctx Relative context.
+ * @param[in] eitem Oldest error structure to remove, optional.
+ */
+void ly_err_clean(struct ly_ctx *ctx, struct ly_err_item *eitem);
+
+/** @} errors */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* LY_LOG_H_ */