/*
 * Purple - Internet Messaging Library
 * Copyright (C) Pidgin Developers <devel@pidgin.im>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <https://www.gnu.org/licenses/>.
 */

#include "queuedoutputstream.h"

struct _PurpleQueuedOutputStream
{
	GFilterOutputStream parent;

	GAsyncQueue *queue;
	gboolean pending_queued;
} PurpleQueuedOutputStreamPrivate;

G_DEFINE_TYPE(PurpleQueuedOutputStream, purple_queued_output_stream,
              G_TYPE_FILTER_OUTPUT_STREAM)

/******************************************************************************
 * Helpers
 *****************************************************************************/

static void purple_queued_output_stream_start_push_bytes_async(GTask *task);

static void
purple_queued_output_stream_push_bytes_async_cb(GObject *source,
                                                GAsyncResult *res,
                                                gpointer user_data)
{
	GTask *task = G_TASK(user_data);
	PurpleQueuedOutputStream *stream = g_task_get_source_object(task);
	gssize written;
	GBytes *bytes;
	gsize size;
	GError *error = NULL;

	written = g_output_stream_write_bytes_finish(G_OUTPUT_STREAM(source),
	                                             res, &error);

	bytes = g_task_get_task_data(task);
	size = g_bytes_get_size(bytes);

	if (written < 0) {
		/* Error occurred, return error */
		g_task_return_error(task, error);
		g_clear_object(&task);
	} else if (size > (gsize)written) {
		/* Partial write, prepare to send remaining data */
		bytes = g_bytes_new_from_bytes(bytes, written, size - written);
		g_task_set_task_data(task, bytes, (GDestroyNotify)g_bytes_unref);
	} else {
		/* Full write, this task is finished */
		g_task_return_boolean(task, TRUE);
		g_clear_object(&task);
	}

	/* If g_task_return_* was called in this function, the callback
	 * may have cleared the stream. If so, there will be no remaining
	 * tasks to process here.
	 */

	if (task == NULL) {
		/* Any queued data left? */
		task = g_async_queue_try_pop(stream->queue);
	}

	if (task != NULL) {
		/* More to process */
		purple_queued_output_stream_start_push_bytes_async(task);
	} else {
		/* All done */
		stream->pending_queued = FALSE;
		g_output_stream_clear_pending(G_OUTPUT_STREAM(stream));
	}
}

static void
purple_queued_output_stream_start_push_bytes_async(GTask *task) {
	PurpleQueuedOutputStream *stream = g_task_get_source_object(task);
	GOutputStream *base_stream = NULL;
	GFilterOutputStream *filtered = NULL;

	filtered = G_FILTER_OUTPUT_STREAM(stream);
	base_stream = g_filter_output_stream_get_base_stream(filtered);

	g_output_stream_write_bytes_async(base_stream, g_task_get_task_data(task),
	                                  g_task_get_priority(task),
	                                  g_task_get_cancellable(task),
	                                  purple_queued_output_stream_push_bytes_async_cb,
	                                  task);
}

/******************************************************************************
 * GObject Implementation
 *****************************************************************************/
static void
purple_queued_output_stream_dispose(GObject *object) {
	PurpleQueuedOutputStream *stream = PURPLE_QUEUED_OUTPUT_STREAM(object);

	g_clear_pointer(&stream->queue, g_async_queue_unref);

	G_OBJECT_CLASS(purple_queued_output_stream_parent_class)->dispose(object);
}

static void
purple_queued_output_stream_class_init(PurpleQueuedOutputStreamClass *klass) {
	GObjectClass *obj_class = G_OBJECT_CLASS(klass);

	obj_class->dispose = purple_queued_output_stream_dispose;
}

static void
purple_queued_output_stream_init(PurpleQueuedOutputStream *stream) {
	stream->queue = g_async_queue_new_full((GDestroyNotify)g_bytes_unref);
	stream->pending_queued = FALSE;
}

/******************************************************************************
 * Public API
 *****************************************************************************/
PurpleQueuedOutputStream *
purple_queued_output_stream_new(GOutputStream *base_stream) {
	g_return_val_if_fail(G_IS_OUTPUT_STREAM(base_stream), NULL);

	return g_object_new(
		PURPLE_TYPE_QUEUED_OUTPUT_STREAM,
		"base-stream", base_stream,
		NULL);
}

void
purple_queued_output_stream_push_bytes_async(PurpleQueuedOutputStream *stream,
                                             GBytes *bytes, int io_priority,
                                             GCancellable *cancellable,
                                             GAsyncReadyCallback callback,
                                             gpointer user_data)
{
	GTask *task;
	gboolean set_pending;
	GError *error = NULL;

	g_return_if_fail(PURPLE_IS_QUEUED_OUTPUT_STREAM(stream));
	g_return_if_fail(bytes != NULL);

	task = g_task_new(stream, cancellable, callback, user_data);
	g_task_set_task_data(task, g_bytes_ref(bytes),
	                     (GDestroyNotify)g_bytes_unref);
	g_task_set_source_tag(task, purple_queued_output_stream_push_bytes_async);
	g_task_set_priority(task, io_priority);

	set_pending = g_output_stream_set_pending(G_OUTPUT_STREAM(stream), &error);

	/* Since we're allowing queuing requests without blocking,
	 * it's not an error to be pending while processing queued operations.
	 */
	if(!set_pending &&
	   (!g_error_matches(error, G_IO_ERROR, G_IO_ERROR_PENDING) ||
	    !stream->pending_queued))
	{
		g_task_return_error(task, error);
		g_object_unref(task);
		return;
	}

	g_clear_error(&error);
	stream->pending_queued = TRUE;

	if(set_pending) {
		/* Start processing if there were no pending operations */
		purple_queued_output_stream_start_push_bytes_async(task);
	} else {
		/* Otherwise queue the data */
		g_async_queue_push(stream->queue, task);
	}
}

gboolean
purple_queued_output_stream_push_bytes_finish(PurpleQueuedOutputStream *stream,
                                              GAsyncResult *result,
                                              GError **error)
{
	g_return_val_if_fail(PURPLE_IS_QUEUED_OUTPUT_STREAM(stream), FALSE);
	g_return_val_if_fail(g_task_is_valid(result, stream), FALSE);
	g_return_val_if_fail(g_async_result_is_tagged(result,
	                                              purple_queued_output_stream_push_bytes_async),
	                     FALSE);

	return g_task_propagate_boolean(G_TASK(result), error);
}

void
purple_queued_output_stream_clear_queue(PurpleQueuedOutputStream *stream) {
	GTask *task;

	g_return_if_fail(PURPLE_IS_QUEUED_OUTPUT_STREAM(stream));

	while((task = g_async_queue_try_pop(stream->queue)) != NULL) {
		g_task_return_new_error(task, G_IO_ERROR, G_IO_ERROR_CANCELLED,
		                        "PurpleQueuedOutputStream queue cleared");
		g_object_unref(task);
	}
}