/**
 * @file  config.h
 * @brief Simple key=value configuration file parser.
 *
 * Parses configuration files with one key=value pair per line.
 * Lines starting with '#' are comments.  Blank lines are ignored.
 * Repeated keys are allowed (used for list-valued settings like
 * trustList).
 */

#ifndef DISCOVERY_CONFIG_H
#define DISCOVERY_CONFIG_H

#include <stddef.h>

/**
 * @brief A single key=value entry from a config file.
 *
 * Both key and value are heap-allocated, null-terminated strings
 * with leading/trailing whitespace trimmed.
 */
typedef struct
{
  char *key;
  char *value;
} ConfigEntry;

/**
 * @brief A parsed configuration file.
 *
 * Holds a dynamic array of ConfigEntry items.  Duplicate keys are
 * allowed (used for list-valued settings like trustList).
 */
typedef struct
{
  ConfigEntry *entries;
  size_t count;
  size_t capacity;
} Config;

/**
 * @brief Parses a configuration file into a Config structure.
 *
 * Each non-blank, non-comment line must contain '=' separating key
 * and value.  Whitespace is trimmed around both key and value.
 *
 * @param path  Path to the configuration file.
 * @param cfg   Output: the parsed configuration.  Must be freed
 *              with configFree() when no longer needed.
 * @return 0 on success, -1 on error (logged via UA_LOG_ERROR).
 */
int configLoad (const char *path, Config *cfg);

/**
 * @brief Looks up a single-valued key.
 *
 * Returns the value of the first entry matching @p key, or NULL
 * if the key is not present.
 *
 * @param cfg  The parsed configuration.
 * @param key  The key to search for.
 * @return The value string (owned by cfg), or NULL.
 */
const char *configGet (const Config *cfg, const char *key);

/**
 * @brief Looks up a required single-valued key.
 *
 * Like configGet(), but logs a FATAL error and returns NULL when
 * the key is missing.
 *
 * @param cfg      The parsed configuration.
 * @param key      The key to search for.
 * @param program  Program name (for error messages).
 * @return The value string (owned by cfg), or NULL if missing.
 */
const char *configRequire (const Config *cfg, const char *key,
                           const char *program);

/**
 * @brief Looks up a required integer-valued key.
 *
 * Parses the value of @p key as an integer.  If the key is
 * missing or the value is not a valid integer, logs a FATAL
 * error and returns -1.
 *
 * @param cfg      The parsed configuration.
 * @param key      The key to search for.
 * @param program  Program name (for error messages).
 * @return The parsed integer, or -1 on error.
 */
int configRequireInt (const Config *cfg, const char *key, const char *program);

/**
 * @brief Collects all values for a repeated key.
 *
 * Allocates an array of char* pointers to the values stored
 * in @p cfg.  The caller must free the array itself (but not
 * the strings, which are owned by cfg).
 *
 * @param cfg   The parsed configuration.
 * @param key   The key to collect (e.g. "trustList").
 * @param out   Output: heap-allocated array of string pointers.
 *              Set to NULL if the key is not present.
 * @param size  Output: number of entries in @p out.
 */
void configGetAll (const Config *cfg, const char *key, char ***out,
                   size_t *size);

/**
 * @brief Frees all memory owned by a Config structure.
 *
 * After this call the Config is zeroed and must not be used
 * unless configLoad() is called again.
 *
 * @param cfg  The configuration to free.
 */
void configFree (Config *cfg);

#endif /* DISCOVERY_CONFIG_H */