/**
 * @defgroup Elm_Prefs Elementary Prefs
 * @ingroup Elementary
 *
 * Elementary provides a prefs (for "preferences") infrastructure, which
 * consists of two sets of APIs:
 * - prefs data and
 * - prefs view.
 *
 * @section elm-prefs-data Prefs Data
 *
 * Prefs data are simple key/value storage handles. One is able to
 * set/get their values, which are @c Eina_Value blobs
 * (i.e. dynamically typed). You may also control the version of this
 * data set, for updating purposes. Finally, you may register
 * callbacks on changes on these data.
 *
 * The main user of prefs data is the prefs @b widget. After its
 * creation, it's bound to a given prefs data handle (if not, if gets
 * its values from its definition file, which may have defaults). An
 * elm prefs widget has its visuals defined by an @c .epb file, which
 * is a compiled form of a @c .edc counterpart -- a textual definition
 * much like Edje @c .edc files. On these files, one defines the
 * values (items) a prefs widget hold, which translate to other
 * Elementary widgets. In other words, it does the mapping between UI
 * widgets into prefs data values, and it keeps the synchrony between
 * its child widgets' states and their corresponding prefs data
 * values.
 *
 * @{
 */

/** Modes of resetting a prefs widget. see elm_prefs_reset()
 *
 * @since 1.8
 */
typedef enum
{
  ELM_PREFS_RESET_DEFAULTS = 0, /**< reset to default values, declared in its
                                 * <b>.epb</b> file */
  ELM_PREFS_RESET_LAST /**< prefs will keep a small history of changes, so this
                        *  resets back to last batch of changes on the UI
                        * elements. it does <b>not</b> work on autosave mode */
} Elm_Prefs_Reset_Mode;

/** Elm Prefs item types.
 *
 * @since 1.8
 */
typedef enum
{
  ELM_PREFS_TYPE_UNKNOWN = 0, /**< Unknown type */
  ELM_PREFS_TYPE_ACTION, /**< action type, bound to button-like UI elements */
  ELM_PREFS_TYPE_BOOL, /**< boolean type, bound to checkbox-like UI elements */
  ELM_PREFS_TYPE_INT, /**< integer type, bound to spinner-like UI elements */
  ELM_PREFS_TYPE_FLOAT, /**< floating point type, bound to spinner-like UI elements */
  ELM_PREFS_TYPE_LABEL, /**< label type, bound to read-only, label UI elements */
  ELM_PREFS_TYPE_DATE, /**< date type, bound to date selection UI elements */
  ELM_PREFS_TYPE_TEXT, /**< text type, bound to single-line, text entry UI elements */
  ELM_PREFS_TYPE_TEXTAREA, /**< text area type, bound to multi-line, text entry UI elements */
  ELM_PREFS_TYPE_PAGE, /**< page type, used to nest pages */
  ELM_PREFS_TYPE_RESET, /**< values resetting trigger type, bound to button-like UI elements */
  ELM_PREFS_TYPE_SAVE, /**< saving trigger type, bound to button-like UI elements */
  ELM_PREFS_TYPE_SEPARATOR, /**< separator type, bound to separator-like UI elements */
  ELM_PREFS_TYPE_SWALLOW /**< swallow type, bound to an empty 'spot' on the UI
                          * meant to receive and display external content */
} Elm_Prefs_Item_Type;

/**
 * Types of events a given prefs data handle may issue.
 *
 * @see elm_prefs_data_event_callback_add()
 *
 * @since 1.8
 */
typedef enum {
   ELM_PREFS_DATA_EVENT_GROUP_AUTOSAVED, /** The group of values has been automatically saved (event info is the group's name (key)) */
   ELM_PREFS_DATA_EVENT_ITEM_CHANGED, /** A given item (prefs data value) has been changed (event info is an #Elm_Prefs_Data_Event_Changed pointer) */
   ELM_PREFS_DATA_EVENT_LAST /** sentinel value, don't use it */
} Elm_Prefs_Data_Event_Type;

/**
 * @typedef Elm_Prefs_Data
 *
 * An Elm Prefs Data handle.
 *
 * @since 1.8
 */
typedef struct _Elm_Prefs_Data Elm_Prefs_Data;

typedef void                 (*Elm_Prefs_Data_Event_Cb)(void *cb_data,
                                                        Elm_Prefs_Data_Event_Type type,
                                                        Elm_Prefs_Data *prefs_data,
                                                        void *event_info);

/**
 * @typedef Elm_Prefs_Data_Event_Changed
 *
 * An Elm Prefs #ELM_PREFS_DATA_EVENT_ITEM_CHANGED event info data
 * blob.
 *
 * @since 1.8
 */
typedef struct _Elm_Prefs_Data_Event_Changed
{
   const char       *key; /** key of the data value which changed */
   const Eina_Value *value; /** the value, itself, to be used as a @b read-only Eina_Value (it can be @c NULL, if the data was deleted) */
} Elm_Prefs_Data_Event_Changed;

/**
 * Create a new prefs data handle.
 *
 * @param data_file The (user) file where to read data from
 * @param key The key where the data is stored under
 * @param mode The mode of access to the given file
 * @return A new prefs data handle
 *
 * If @a data_file is @c NULL,
 * efreet_config_home_get()/<appname>/preferences.cfg will be used, by
 * default. If @a key is @c NULL, it is considered a default key --
 * "main".
 *
 * If @a mode is @c EET_FILE_MODE_READ, autosave will be always false
 * for this elm_prefs_data handle. If @a mode is
 * @c EET_FILE_MODE_WRITE, than @a data_file @b won't be read, but just
 * written to.
 *
 * @note An elm prefs data handle starts with a reference count of @b
 * 1 (see elm_prefs_data_ref()). Use elm_prefs_data_unref() to delete
 * it.
 *
 * @since 1.8
 */
EAPI Elm_Prefs_Data *elm_prefs_data_new(const char *data_file,
                                        const char *key,
                                        Eet_File_Mode mode);

/**
 * Set the version field of a given prefs data handle.
 *
 * @param prefs_data A valid prefs data handle
 * @param version The version number
 * @return @c EINA_TRUE on success, @c EINA_FALSE otherwise
 *
 * @see elm_prefs_data_version_get()
 *
 * @since 1.8
 */
EAPI Eina_Bool       elm_prefs_data_version_set(Elm_Prefs_Data *prefs_data,
                                                unsigned int version);

/**
 * Get the version field of a given prefs data handle.
 *
 * @param prefs_data A valid prefs data handle
 * @return The version of @a prefs_data or -1, on errors.
 *
 * @see elm_prefs_data_version_set()
 *
 * @since 1.8
 */
EAPI unsigned int    elm_prefs_data_version_get(const Elm_Prefs_Data *prefs_data);

/**
 * Increment reference count on a given prefs data handle.
 *
 * @param prefs_data A valid prefs data handle
 * @return The same prefs data handle, @a prefs_data
 *
 * This increments the reference count of @a by 1. Use this to pass
 * the handle safely to contexts other than the creation one, for
 * example. Only when the reference count on a prefs data handle
 * reaches @b 0 (see elm_prefs_data_unref()) will it be deleted.
 *
 * @since 1.8
 */
EAPI Elm_Prefs_Data *elm_prefs_data_ref(Elm_Prefs_Data *prefs_data);

/**
 * Decrement reference count on a given prefs data handle.
 *
 * @param prefs_data A valid prefs data handle
 *
 * This decrements the reference count of @a by 1. When the reference
 * count on @a reach @b 0, it will it be deleted.
 *
 * @see elm_prefs_data_ref() for more details.
 *
 * @since 1.8
 */
EAPI void            elm_prefs_data_unref(Elm_Prefs_Data *prefs_data);

/**
 * Set (or delete) one value of a given prefs data handle.
 *
 * @param prefs_data A valid prefs data handle
 * @param path The (unique) name (key) of the given value
 * @param type The item type to which the value is to be associated
 * @param value The value, itself. It must be a valid @c Eina_Value
 *              handle, bound to a given type and value or @c NULL. On
 *              the second case, the call will actually @b delete the
 *              given key from @a prefs_data.
 * @return @c EINA_TRUE on success, @c EINA_FALSE otherwise
 *
 * A prefs data handle holds a list of key/value entries. This will
 * set one of @a's values, by name. The value itself may be any valid
 * and filled up @c Eina_Value handle.
 *
 * @since 1.8
 */
EAPI Eina_Bool       elm_prefs_data_value_set(Elm_Prefs_Data *prefs_data,
                                              const char *path,
                                              const Elm_Prefs_Item_Type type,
                                              const Eina_Value *value);

/**
 * Get one value of a given prefs data handle (by key).
 *
 * @param prefs_data A valid prefs data handle
 * @param path The (unique) name (key) of the given value
 * @param type The item type associated with the value
 * @param value A valid @c Eina_Value handle, where to store the
 *              value, itself.
 * @return @c EINA_TRUE on success, @c EINA_FALSE otherwise
 *
 * This will retrieve one of @a's values, by name. The value itself
 * will be written to @a value, which will be overriden.
 *
 * @since 1.8
 */
EAPI Eina_Bool       elm_prefs_data_value_get(const Elm_Prefs_Data *prefs_data,
                                              const char *path,
                                              Elm_Prefs_Item_Type *type,
                                              Eina_Value *value);

/**
 * Register a callback for one of the prefs data events.
 *
 * @param prefs_data A valid prefs data handle
 * @param type The type of event to register to
 * @param cb The callback function to issue on this event
 * @param cb_data The data pointer to pass to @a cb on this event
 * @return @c EINA_TRUE on success, @c EINA_FALSE otherwise
 *
 * @see #Elm_Prefs_Data_Event_Type for more details on the events.
 * @see elm_prefs_data_event_callback_del()
 *
 * @since 1.8
 */
EAPI Eina_Bool       elm_prefs_data_event_callback_add(Elm_Prefs_Data *prefs_data,
                                                       Elm_Prefs_Data_Event_Type type,
                                                       Elm_Prefs_Data_Event_Cb cb,
                                                       const void *cb_data);
/**
 * Unregister a callback for one of the prefs data events.
 *
 * @param prefs_data A valid prefs data handle
 * @param type The type of event to unregister
 * @param cb The callback function being used to this event
 * @param cb_data The data pointer being passed to @a cb on this event
 * @return @c EINA_TRUE on success, @c EINA_FALSE otherwise
 *
 * @see #Elm_Prefs_Data_Event_Type for more details on the events.
 * @see elm_prefs_data_event_callback_add()
 *
 * @note If a same event callback (with matching type, callback
 * function and data pointers) was added more than once on
 * @a prefs_data, them same number of matching calls of this type have to
 * issued to delete all them.
 *
 * @since 1.8
 */
EAPI Eina_Bool       elm_prefs_data_event_callback_del(Elm_Prefs_Data *prefs_data,
                                                       Elm_Prefs_Data_Event_Type type,
                                                       Elm_Prefs_Data_Event_Cb cb,
                                                       const void *cb_data);

/**
 * Set whether a given elm prefs data handle should save its values
 * back automatically on changes.
 *
 * @param prefs_data A valid prefs data handle
 * @param autosave @c EINA_TRUE to save automatically, @c EINA_FALSE otherwise.
 *
 * If @a autosave is @c EINA_TRUE, every call to
 * elm_prefs_data_value_set() will implicitly issue elm_prefs_data_save() too.
 *
 * @warning This call will do nothing if @a prefs_data was created
 * with mode EET_FILE_MODE_READ -- auto saving will be always disabled
 * in this mode, as it can't write back.
 *
 * @see elm_prefs_data_autosave_get()
 *
 * @since 1.8
 */
EAPI void      elm_prefs_data_autosave_set(Elm_Prefs_Data *prefs_data,
                                           Eina_Bool autosave);

/**
 * Get whether a given elm prefs data handle is saving its values
 * back automatically on changes.
 *
 * @param prefs_data A valid prefs data handle
 * @return @c EINA_TRUE if @a prefs_data is saving automatically,
 *         @c EINA_FALSE otherwise.
 *
 * @see elm_prefs_data_autosave_set()
 *
 * @since 1.8
 */
EAPI Eina_Bool elm_prefs_data_autosave_get(const Elm_Prefs_Data *prefs_data);

/**
 * Save, manually, a given elm prefs data handle data back, on the given
 * file and key.
 *
 * @param prefs_data A valid prefs data handle
 * @param file The file (path) to save to (@c NULL means same file as
 *             it was opened with)
 * @param key The under which to save values (@c NULL means the same
 *            key as it was opened with)
 * @return @c EINA_TRUE on success, @c EINA_FALSE otherwise.
 *
 * @see elm_prefs_data_autosave_set()
 *
 * @since 1.8
 */
EAPI Eina_Bool elm_prefs_data_save(const Elm_Prefs_Data *prefs_data,
                                   const char *file,
                                   const char *key);

/**
 * @}
 */