/**
 * \file paths.h
 * XDG Directory Specification implementation
 */

#ifndef PATHS_H
#define PATHS_H

/**
 * Opaque type for paths
 */
typedef struct paths_t paths_t;

/**
 * Opaque type for a currently open file
 */
typedef struct paths_file_t paths_file_t;

/**
 * The different sources or directories if you will that are in the
 * specification.
 */
typedef enum paths_source_t
{
    /** directory for data files */
    PATHS_DATA,
    /** directory for config files */
    PATHS_CONFIG,
    /** directory for cache files */
    PATHS_CACHE,
    /** directory for runtime files */
    PATHS_RUNTIME,
} paths_source_t;

/** Do not block write calls */
#define PATHS_NONBLOCK  (0x01)
/** Append on each write */
#define PATHS_APPEND    (0x02)
/** Create file if needed */
#define PATHS_CREATE    (0x04)
/** Truncate file when opening */
#define PATHS_TRUNCATE  (0x08)
/** If PATHS_CREATE is set, give error if file already exists */
#define PATHS_EXCLUSIVE (0x10)

/**
 * Create a new paths.
 * Initializes the list of directories from enviroment variables.
 * Returned object has a reference count of one.
 * Threadsafe.
 * Returns NULL in case of allocation errors.
 * @return a new paths
 */
MALLOC paths_t* paths_new(void);

/**
 * Increase the reference count for paths.
 * Threadsafe.
 * @param paths paths object, may not be NULL
 */
NONULL void paths_ref(paths_t* paths);

/**
 * Decrease the reference count for paths and free if it reached zero.
 * Threadsafe.
 * @param paths paths object, may be NULL
 */
void paths_unref(paths_t* paths);

/**
 * Get single directory where user-specific files should be written.
 * May only return NULL for PATHS_RUNTIME all other sources are guaranteed to
 * return a non-NULL string. They may however return non-existant paths.
 * PATHS_RUNTIME will return NULL if no such path was found as it has no
 * default.
 * If you wish paths to be created if missing, please use paths_write().
 * Threadsafe.
 * @param paths paths object, may not be NULL
 * @param source requested directory
 * @return absolute path to directory or NULL
 */
NONULL const char* paths_user_dir(paths_t* paths, paths_source_t source);

/**
 * Get preference ordered list of directories to search for files.
 * All paths are absolute and NULL terminated. The list itself is NULL
 * terminated and may never be empty. Path returned by paths_user_dir() for
 * the same source is not included.
 * Will return NULL for PATHS_CACHE and PATHS_RUNTIME as they are only
 * user-specific writable directories.
 * Threadsafe.
 * @param paths paths object, may not be NULL
 * @param source requested directory
 * @return NULL terminated list of absolute paths to search or NULL
 */
NONULL const char** paths_search_dirs(paths_t* paths, paths_source_t source);

/**
 * Callback called with the result(s) from paths_find(). May be called from
 * any thread. Return false to cancel the search, true to continue until all
 * has been found. filename will be NULL when no more matches was found.
 * The filename pointer is only valid until the callback has returned.
 * @param userdata userdata given to paths_find()
 * @param filenamme found file or NULL if no more results
 * @return true to continue the search, false to not */
typedef bool (* paths_find_callback_t)(void* userdata, const char* filename);

/**
 * Asynchronous search for matching files in directories for source.
 * Returned in preference order, first paths_user_dir() and then
 * paths_search_dirs().
 * The callback is always called at least once.
 * Match may use *, ?, [] and {} glob matches. It may also contain / characters
 * to search in subdirectories
 * Threadsafe.
 * @param paths paths object, may not be NULL
 * @param source requested directory
 * @param match glob pattern to search with. may not be NULL
 * @param find_callback callback to call when finding results, may not be NULL
 * @param userdata argument to callback, may be NULL
 */
NONULL_ARGS(1, 3, 4)
void paths_find(paths_t* paths, paths_source_t source, const char* match,
                paths_find_callback_t find_callback, void* userdata);

/**
 * Synchronous setup to create file in directory.
 * Returns NULL in case of error, see errno for details.
 * Depending on source and convention, the actual file may not be created with
 * the given name until paths_file_close().
 * The file will eventually always end up in paths_user_dir() for directory.
 * If any part of the target path is missing it will be created if possible.
 * If flags contains PATHS_CREATE then the 5th argument mode_t mode must be
 * given, just as for open().
 * Threadsafe but what happens if two threads at the same time opens the same
 * target file is up to the platforms locking mechanism.
 * The returned paths_file_t is not threadsafe.
 * @param paths paths object, may not be NULL
 * @param source target directoru
 * @param filename relative path of target file, may not be NULL
 * @param flags flags
 * @param ... mode if PATHS_CREATE is included in flags
 * @return a file reference or NULL
 */
NONULL paths_file_t* paths_write(paths_t* paths, paths_source_t source,
                                 const char* filename, unsigned int flags,
                                 ...);

/**
 * Write data to file.
 * Works just as libc write().
 * Not threadsafe,
 * the paths_file_t must only be accessed by one thread at a time.
 * @param file target file, may not be NULL
 * @param data data to write, may be NULL if size is zero
 * @param size the maximum number of bytes to read from data
 * @return number of bytes written to target
 */
NONULL_ARGS(1)
ssize_t paths_file_write(paths_file_t* file, const void* data, size_t size);

/**
 * Close and finish saving file.
 * If the file was saved successfully, the paths_file_t object is freed.
 * If the save failed in any way, the object is not freed so you must call
 * paths_file_abort() to finish up (or call paths_file_close() again and
 * hope for better luck this time).
 * Not threadsafe,
 * the paths_file_t must only be accessed by one thread at a time.
 * @param file target file, may not be NULL
 * @return zero on success, non-zero in case of error
 */
NONULL int paths_file_close(paths_file_t* file);

/**
 * Abort saving the file. The target file is removed unless the original version
 * before paths_write() could be restored.
 * Not threadsafe,
 * the paths_file_t must only be accessed by one thread at a time.
 * @param file target file, may be NULL
 */
void paths_file_abort(paths_file_t* file);

/**
 * Get absolute path to directory where user-specific data files should be
 * written. Returned directory may not exist.
 * Threadsafe.
 * @param paths paths object, may not be NULL
 * @return absolute path to data directory
 */
static inline NONULL const char* paths_user_data(paths_t* paths)
{
    return paths_user_dir(paths, PATHS_DATA);
}

/**
 * Get absolute path to directory where user-specific config files should be
 * written. Returned directory may not exist.
 * Threadsafe.
 * @param paths paths object, may not be NULL
 * @return absolute path to config directory
 */
static inline NONULL const char* paths_user_config(paths_t* paths)
{
    return paths_user_dir(paths, PATHS_CONFIG);
}

/**
 * Get absolute path to directory where user-specific cache files should be
 * written. Returned directory may not exist.
 * Threadsafe.
 * @param paths paths object, may not be NULL
 * @return absolute path to cache directory
 */
static inline NONULL const char* paths_user_cache(paths_t* paths)
{
    return paths_user_dir(paths, PATHS_CACHE);
}

/**
 * Get absolute path to directory where user-specific runtime files should be
 * written.
 * If not defined in enviroment or not valid NULL is returned.
 * Threadsafe.
 * @param paths paths object, may not be NULL
 * @return absolute path to runtime directory or NULL
 */
static inline NONULL const char* paths_user_runtime(paths_t* paths)
{
    return paths_user_dir(paths, PATHS_RUNTIME);
}

/**
 * Get preference ordered list of directories to search for data files.
 * All paths are absolute and NULL terminated. The list itself is NULL
 * terminated and may never be empty. Path returned by paths_user_data()
 * is not included.
 * Threadsafe.
 * @param paths paths object, may not be NULL
 * @return NULL terminated list of absolute paths to search
 */
static inline NONULL const char** paths_data(paths_t* paths)
{
    return paths_search_dirs(paths, PATHS_DATA);
}

/**
 * Get preference ordered list of directories to search for config files.
 * All paths are absolute and NULL terminated. The list itself is NULL
 * terminated and may never be empty. Path returned by paths_user_config()
 * is not included.
 * Threadsafe.
 * @param paths paths object, may not be NULL
 * @return NULL terminated list of absolute paths to search
 */
static inline NONULL const char** paths_config(paths_t* paths)
{
    return paths_search_dirs(paths, PATHS_CONFIG);
}

#endif /* PATHS_H */