/**
 * @b Generic data needs to be type-casted to plugin-specific data,
 * depending on @c type of plugin in @x XuiPlugin object.
 * */
typedef void *XuiPluginGenericData;

typedef Bool (*XuiPluginInit)();
typedef Bool (*XuiPluginDeinit)();

typedef struct XuiPluginVersion {
    Uint16 year;
    Uint8  month;
    Uint8  date;
} XuiPluginVersion;

typedef enum XuiPluginType {
    XUI_PLUGIN_TYPE_NONE     = 0,
    XUI_PLUGIN_TYPE_GRAPHICS = 1, /**< @b Defined in Plugin/Graphics */
    XUI_PLUGIN_TYPE_MAX
} XuiPluginType;

typedef Uint8 XuiPluginPlatform;

typedef enum XuiPluginPlatformMask : XuiPluginPlatform {
    XUI_PLUGIN_PLATFORM_MASK_NONE    = 0, /**< @b No platform supported. (Must not be the case) */
    XUI_PLUGIN_PLATFORM_MASK_LINUX   = (1 << 0), /**< @b Plugin can work on Linux. */
    XUI_PLUGIN_PLATFORM_MASK_WINDOWS = (1 << 1), /**< @b Plugin can work on windows. */
    XUI_PLUGIN_PLATFORM_MASK_MAC     = (1 << 2), /**< @b Plugin can work on MacOS */
    XUI_PLUGIN_PLATFORM_MASK_ANDROID = (1 << 3), /**< @b Plugin can work on android */
    XUI_PLUGIN_PLATFORM_MASK_ALL =
        (XuiPluginPlatform)-1                    /**< @b The plugin works on all platforms */
} XuiPluginPlatfomMask;

typedef struct XuiPlugin {
    XuiPluginType     type;                /**< @b Type of plugin */
    CString           name;                /**< @b Name of plugin. */
    XuiPluginVersion  version;             /**< @b Plugin version. */
    CString           license;             /**< @b License information about plugin.*/
    XuiPluginPlatform supported_platforms; /**< @b Bitmask of supported platforms by the plugin */
    XuiPluginGenericData plugin_data;      /**< @b Data of plugin dependent on plugin type. */
    XuiPluginInit        init;             /**< @b Initialize plugin. */
    XuiPluginDeinit      deinit;           /**< @b De-initialize plugin. */
    void                *plugin_handle;    /**< @b Loaded plugin library handle. */
} XuiPlugin;

XuiPlugin *xui_plugin_load (CString plugin_name);
void       xui_plugin_unload (XuiPlugin *plugin);

/**
 * @b Opaque structure, defined by the plugin.
 *
 * Rendered image presentation method is different in different rendering APIs.
 * To abstract this away, I've decided to use a GraphicsContext, that's plugin
 * dependent. This needs to be passed to plugin whenever we need to render something.
 *
 * One can think of GraphicsContext having one-to-one correspondence with window.
 * */
typedef struct XuiGraphicsContext XuiGraphicsContext;

/**
 * @b Create a graphics context for given window.
 *
 * @param window 
 *
 * @return @c XuiGraphicsContext opaque object pointer on success.
 * @return @c Null otherwise.
 * */
typedef XuiGraphicsContext *(*XuiGraphicsContextCreate) (XwWindow *window);

/**
 * @b Destroy the given graphics context.
 *
 * @param gctx GraphicsContext object to be destroyed.
 * */
typedef void (*XuiGraphicsContextDestroy) (XuiGraphicsContext *gctx);

/**
 * @b Plugin must render given 2D shape.
 *
 * This is a per-vertex draw call.  
 *
 * @param graphics_context The @c XuiGraphicsContext object created for @x xwin.
 * @param xwin @c XwWindow object used to create @c graphics context.
 * @param vertices Array of 2D vertices.
 * @param vertex_count Number of vertices.
 *
 * @return True if draw was successful.
 * @return False otherwise.
 *
 * @sa XuiGraphicsDrawIndexed2D
 * */
typedef Bool (*XuiGraphicsDraw2D) (
    XuiGraphicsContext *graphics_context,
    XwWindow           *xwin,
    Vertex2D           *vertices,
    Size                vertex_count
);

/**
 * @b Plugin must render given 2D shape, along with indices data.
 *
 * This is an indexed, per-vertex call. Indices define the actual shape.
 * Refer to indexed drawing method for more detail.
 *
 * @param graphics_context The @c XuiGraphicsContext object created for @x xwin.
 * @param xwin @c XwWindow object used to create @c graphics context.
 * @param vertices Array of 2D vertices.
 * @param vertex_count Number of vertices.
 * @param indices Array of 2D vertices.
 * @param index_count Number of vertices.
 *
 * @return True if draw was successful.
 * @return False otherwise.
 *
 * @sa XuiGraphicsDrawIndexed2D
 * */
typedef Bool (*XuiGraphicsDrawIndexed2D) (
    XuiGraphicsContext *graphics_context,
    XwWindow           *xwin,
    Vertex2D           *vertices,
    Size                vertex_count,
    Uint32              indices,
    Size                index_count
);

/**
 * @b Defines set of callbacks to be used to interact with the plugin.
 * */
typedef struct XuiGraphicsPlugin {
    XuiGraphicsContextCreate context_create;
    XuiGraphicsContextDestroy context_destroy;
    XuiGraphicsDraw2D        draw_2d;
    XuiGraphicsDrawIndexed2D draw_indexed_2d;
} XuiGraphicsPlugin;

/* Describe callbacks in graphics plugin data */
static XuiGraphicsPlugin vulkan_graphics_plugin_data = {
    .context_create  = graphics_context_create,
    .context_destroy = graphics_context_destroy,
    .draw_2d         = draw_2d,
    .draw_indexed_2d = Null
};

/**
 * @b Vulkan Graphics Plugin
 * */
XuiPlugin xui_plugin = {
    .type                = XUI_PLUGIN_TYPE_GRAPHICS,
    .name                = "Vulkan Graphics Plugin",
    .version             = {.date = 20, .month = 4, .year = 2024},
    .license             = "BSD 3-Clause License",
    .supported_platforms = XUI_PLUGIN_PLATFORM_MASK_LINUX,
    .plugin_data         = &vulkan_graphics_plugin_data,
    .init                = (XuiPluginInit)init,
    .deinit              = (XuiPluginDeinit)deinit
};

XuiPlugin *xui_plugin_load (CString plugin_name) {
    RETURN_VALUE_IF (!plugin_name, Null, ERR_INVALID_ARGUMENTS);

    void *plugin_handle = dlopen (plugin_name, RTLD_NOW);
    RETURN_VALUE_IF (!plugin_handle, Null, "Failed to open plugin %s\n", plugin_name);

    XuiPlugin *plugin = (XuiPlugin *)dlsym (plugin_handle, "xui_plugin");
    GOTO_HANDLER_IF (
        !plugin,
        PLUGIN_NOT_FOUND,
        "Failed to find plugin info \"xui_plugin\". Did you define it publicly in the plugin?\n"
    );

    plugin->plugin_handle = plugin_handle;

    PRINT_ERR (
        "Loaded plugin \"%s\" Version %u.%u.%u\n",
        plugin->name,
        plugin->version.date,
        plugin->version.month,
        plugin->version.year
    );

    return plugin;
PLUGIN_NOT_FOUND:
    dlclose (plugin_handle);
    return Null;
}

void xui_plugin_unload (XuiPlugin *plugin) {
    RETURN_IF (!plugin, ERR_INVALID_ARGUMENTS);

    dlclose (plugin->plugin_handle);
}

int main (Int32 argc, CString *argv) {
    RETURN_VALUE_IF (argc < 2, EXIT_FAILURE, "%s <plugin path>\n", argv[0]);

    XuiPlugin *plugin = xui_plugin_load (argv[1]);
    RETURN_VALUE_IF (!plugin, EXIT_FAILURE, "Failed to load plugin\n");

    plugin->init();
    XuiGraphicsPlugin *gplug = (XuiGraphicsPlugin *)plugin->plugin_data;

    XwWindow           *xwin = xw_window_create (Null, 540, 360, 0, 0);
    XuiGraphicsContext *gctx = gplug->context_create (xwin);
    RETURN_VALUE_IF (!gctx, EXIT_FAILURE, "Failed to create graphics context\n");

    XwEvent e;
    Bool    is_running = True;
    while (is_running) {
        while (xw_event_poll (&e)) {
            is_running = e.type != XW_EVENT_TYPE_CLOSE_WINDOW;
        }
        gplug->draw_2d (gctx, xwin, (Vertex2D *)1, 1);
    }

    gplug->context_destroy (gctx);
    xw_window_destroy (xwin);
    plugin->deinit();

    xui_plugin_unload (plugin);

    return EXIT_SUCCESS;
}