libakgl/include/akgl/registry.h

/**
 * @file registry.h
 * @brief The name-to-object lookup tables, and the string configuration store.
 *
 * Nothing in this library is passed around by pointer where a name will do. An
 * actor names the character it instantiates, a character names the sprites it
 * draws, a sprite names the sheet it cuts frames from -- all resolved at load
 * time through these eight registries. That is what lets the whole asset graph
 * be described in JSON files that reference each other by name.
 *
 * They are SDL property sets, not akgl types, so a caller can enumerate one with
 * `SDL_EnumerateProperties` -- which is exactly what akgl_registry_iterate_actor
 * and akgl_character_state_sprites_iterate are for.
 *
 * Every id starts at 0, which SDL treats as "no such property set": reads return
 * the default and writes are silently dropped. So an uninitialized registry does
 * not fail loudly, it fails quietly, and akgl_registry_init has to run first.
 *
 * @warning akgl_registry_init does *not* initialize
 *          #AKGL_REGISTRY_PROPERTIES -- akgl_registry_init_properties is a
 *          separate call, made by akgl_game_init but by nothing else. A program
 *          that builds its own startup path and skips it gets a silently
 *          no-op akgl_set_property and an akgl_get_property that always hands
 *          back the caller's default, which in turn means akgl_render_init2d
 *          and akgl_physics_init_arcade quietly ignore their configuration.
 *          TODO.md, "Known and still open" item 3.
 */

#ifndef _REGISTRY_H_
#define _REGISTRY_H_

#include <akgl/error.h>
#include <akgl/staticstring.h>

/** @brief Actor name -> `akgl_Actor *`. Written by akgl_actor_initialize, cleared when an actor's last reference goes. */
extern SDL_PropertiesID AKGL_REGISTRY_ACTOR;
/** @brief Sprite name -> `akgl_Sprite *`. The `name` field from a sprite JSON. */
extern SDL_PropertiesID AKGL_REGISTRY_SPRITE;
/** @brief Resolved image path -> `akgl_SpriteSheet *`. Keyed by path so two sprites sharing an image share the texture. */
extern SDL_PropertiesID AKGL_REGISTRY_SPRITESHEET;
/** @brief Character name -> `akgl_Character *`. What akgl_actor_set_character resolves against. */
extern SDL_PropertiesID AKGL_REGISTRY_CHARACTER;
/** @brief Actor-state name -> its bit value, as a number. Lets character JSON say "AKGL_ACTOR_STATE_FACE_LEFT" instead of 2. */
extern SDL_PropertiesID AKGL_REGISTRY_ACTOR_STATE_STRINGS;
/** @brief Font name -> `TTF_Font *`. Names are chosen by the caller of akgl_text_loadfont, not derived from the file. */
extern SDL_PropertiesID AKGL_REGISTRY_FONT;
/** @brief Music name -> audio handle. Created but not yet populated by anything in the library. */
extern SDL_PropertiesID AKGL_REGISTRY_MUSIC;
/** @brief Configuration key -> string value. Read through akgl_get_property; everything is a string, including numbers. */
extern SDL_PropertiesID AKGL_REGISTRY_PROPERTIES;

/**
 * @brief Create the seven asset registries, in dependency order.
 *
 * Spritesheet, sprite, character, actor, actor-state-strings, font, music. Call
 * it once at startup, before loading anything.
 *
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If SDL cannot allocate any one of the property sets;
 *         the message names which registry failed. The registries created before
 *         the failure are left in place rather than torn down.
 *
 * @warning This does not create #AKGL_REGISTRY_PROPERTIES -- see the warning on
 *          this file.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_init();
/**
 * @brief Create the music registry.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If SDL cannot allocate the property set.
 * @note Overwrites the existing id without destroying the old set, so calling it
 *       twice leaks the first one along with everything registered in it.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_init_music();
/**
 * @brief Create the font registry.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If SDL cannot allocate the property set.
 * @note Overwrites the existing id without destroying the old set. See
 *       akgl_registry_init_music.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_init_font();
/**
 * @brief Create the actor registry, destroying any previous one first.
 *
 * The one initializer here that cleans up after itself, which is what makes it
 * safe to call between levels: it destroys the old property set before creating
 * the replacement, so the actors from the previous map are unregistered in one
 * step. Note that it destroys the *registry*, not the actors -- releasing those
 * is akgl_heap_release_actor's job.
 *
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If SDL cannot allocate the property set. The old one
 *         has already been destroyed at that point, so the registry is left at 0.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_init_actor();
/**
 * @brief Create the sprite registry.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If SDL cannot allocate the property set.
 * @note Overwrites the existing id without destroying the old set. See
 *       akgl_registry_init_music.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_init_sprite();
/**
 * @brief Create the spritesheet registry.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If SDL cannot allocate the property set.
 * @note Overwrites the existing id without destroying the old set. See
 *       akgl_registry_init_music.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_init_spritesheet();
/**
 * @brief Create the character registry.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If SDL cannot allocate the property set.
 * @note Overwrites the existing id without destroying the old set. See
 *       akgl_registry_init_music.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_init_character();
/**
 * @brief Create the configuration-property registry.
 *
 * Deliberately separate from akgl_registry_init, because configuration has to be
 * in place before the subsystems that read it start up. akgl_game_init creates
 * it; filling it in -- with akgl_registry_load_properties or akgl_set_property --
 * is the caller's job, and has to happen before akgl_render_init2d or
 * akgl_physics_init_arcade run.
 *
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If SDL cannot allocate the property set.
 * @note Overwrites the existing id without destroying the old set, so every
 *       property set before a second call is lost.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_init_properties();
/**
 * @brief Load a JSON configuration file into the property registry.
 *
 * Expects a document with a top-level `properties` object whose members are all
 * strings; each becomes one entry. Numbers are configured as strings here and
 * parsed by whoever reads them -- `game.screenwidth` is `"800"`, not `800`.
 *
 * @param fname Path to the JSON document. Required. Used verbatim.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If @p fname is `NULL`, or if the file cannot be
 *         opened or does not parse. The message carries jansson's line number
 *         and text.
 * @throws AKERR_KEY If the document has no top-level `properties` member.
 * @throws AKERR_TYPE If `properties` is not an object, or if one of its members
 *         is not a string.
 * @throws AKGL_ERR_HEAP If the string pool is exhausted.
 *
 * @note Writes into #AKGL_REGISTRY_PROPERTIES, so akgl_registry_init_properties
 *       has to have run -- otherwise every entry is silently dropped and this
 *       still returns success.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_load_properties(char *fname);
/**
 * @brief Create the actor-state-name registry and fill it from the name table.
 *
 * Walks `AKGL_ACTOR_STATE_STRING_NAMES` and maps entry `i` to the value `1 << i`,
 * which is what lets a character JSON write `"AKGL_ACTOR_STATE_FACE_LEFT"` and
 * have akgl_character_load_json turn it into a bit.
 *
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If SDL cannot allocate the property set. The
 *         individual name registrations are not checked.
 *
 * @note The name table it reads disagrees with actor.h in two places: bits 11
 *       and 12 are named `UNDEFINED_11`/`UNDEFINED_12` rather than `MOVING_IN`
 *       and `MOVING_OUT`, so those two states cannot be named from JSON at all.
 *       TODO.md items 24-26.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_registry_init_actor_state_strings();
/**
 * @brief Set one configuration property.
 *
 * @param name  Property key. Required.
 * @param value Property value. Required. SDL copies it, so the caller's buffer
 *              can go away afterwards.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If @p name or @p value is `NULL`.
 *
 * @note The write itself is unchecked. If #AKGL_REGISTRY_PROPERTIES is still 0 --
 *       akgl_registry_init_properties never having run -- this discards the
 *       value and returns success.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_set_property(char *name, char *value);
/**
 * @brief Read one configuration property into a pooled string, with a fallback.
 *
 * Absence is not an error: an unset property yields @p def, which is how every
 * caller in the library gets a working default without checking first.
 *
 * @param name Property key. Required.
 * @param dest Receives the value. Required. If `*dest` is `NULL` a string is
 *             claimed from the pool for you, so initialize it to `NULL` on the
 *             first call; either way the caller releases it with
 *             akgl_heap_release_string. If `*dest` is non-`NULL` it is written
 *             in place.
 * @param def  Value to use when @p name is not set. Effectively required --
 *             a `NULL` here on an unset property is an AKERR_NULLPOINTER rather
 *             than an empty result.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER If @p name or @p dest is `NULL`, or if the property
 *         is unset and @p def is `NULL`.
 * @throws AKERR_OUTOFBOUNDS If the stored value is #AKGL_MAX_STRING_LENGTH bytes
 *         or longer, which will not fit an akgl_String with its terminator.
 * @throws AKERR_VALUE If the value and the destination overlap in memory.
 * @throws AKGL_ERR_HEAP If `*dest` was `NULL` and the string pool is exhausted.
 *
 * @note Only the value and its terminator are copied. The rest of @p dest keeps
 *       whatever the previous holder left there, so read the result as a C
 *       string rather than as #AKGL_MAX_STRING_LENGTH bytes.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_get_property(char *name, akgl_String **dest, char *def);

#endif //_REGISTRY_H_