/* Write an image to a disc file.
 *
 * 19/3/10
 * 	- from im_wbuffer.c
 * 	- move on top of VipsThreadpool, instead of im_threadgroup_t
 * 23/6/10
 * 	- better buffer handling for single-line images
 * 17/7/10
 * 	- we could get stuck if allocate failed (thanks Tim)
 * 23/2/12
 * 	- we could deadlock if generate failed
 */

/*

	This file is part of VIPS.

	VIPS is free software; you can redistribute it and/or modify
	it under the terms of the GNU Lesser 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 Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  USA

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/*
#define VIPS_DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif /*HAVE_UNISTD_H*/

#include <vips/vips.h>
#include <vips/internal.h>
#include <vips/thread.h>
#include <vips/threadpool.h>
#include <vips/debug.h>

#include "sink.h"

/* A buffer we are going to write to disc in a background thread.
 */
typedef struct _WriteBuffer {
	struct _Write *write;

	VipsRegion *region;	  /* Pixels */
	VipsRect area;		  /* Part of image this region covers */
	VipsSemaphore go;	  /* Start bg thread loop */
	VipsSemaphore nwrite; /* Number of threads writing to region */
	VipsSemaphore done;	  /* Bg thread has done write */
	VipsSemaphore finish; /* Bg thread has finished */
	int write_errno;	  /* Save write errors here */
	gboolean running;	  /* Whether the bg writer thread is running */
	gboolean kill;		  /* Set to ask thread to exit */
} WriteBuffer;

/* Per-call state.
 */
typedef struct _Write {
	SinkBase sink_base;

	/* We are current writing tiles to buf, buf_back is in the hands of
	 * the bg write thread.
	 */
	WriteBuffer *buf;
	WriteBuffer *buf_back;

	/* The file format write operation.
	 */
	VipsRegionWrite write_fn;
	void *a;
} Write;

/* Our per-thread state ... we need to also track the buffer that pos is
 * supposed to write to.
 */
typedef struct _WriteThreadState {
	VipsThreadState parent_object;

	WriteBuffer *buf;
} WriteThreadState;

typedef struct _WriteThreadStateClass {
	VipsThreadStateClass parent_class;

} WriteThreadStateClass;

G_DEFINE_TYPE(WriteThreadState, write_thread_state, VIPS_TYPE_THREAD_STATE);

static void
write_thread_state_class_init(WriteThreadStateClass *class)
{
	VipsObjectClass *object_class = VIPS_OBJECT_CLASS(class);

	object_class->nickname = "writethreadstate";
	object_class->description = _("per-thread state for sinkdisc");
}

static void
write_thread_state_init(WriteThreadState *state)
{
	state->buf = NULL;
}

static VipsThreadState *
write_thread_state_new(VipsImage *im, void *a)
{
	return VIPS_THREAD_STATE(vips_object_new(
		write_thread_state_get_type(),
		vips_thread_state_set, im, a));
}

static void
wbuffer_free(WriteBuffer *wbuffer)
{
	/* Is there a thread running this region? Kill it!
	 */
	if (wbuffer->running) {
		wbuffer->kill = TRUE;
		vips_semaphore_up(&wbuffer->go);

		vips_semaphore_down(&wbuffer->finish);

		VIPS_DEBUG_MSG("wbuffer_free:\n");

		wbuffer->running = FALSE;
	}

	VIPS_UNREF(wbuffer->region);
	vips_semaphore_destroy(&wbuffer->go);
	vips_semaphore_destroy(&wbuffer->nwrite);
	vips_semaphore_destroy(&wbuffer->done);
	vips_semaphore_destroy(&wbuffer->finish);
	g_free(wbuffer);
}

static void
wbuffer_write(WriteBuffer *wbuffer)
{
	Write *write = wbuffer->write;

	VIPS_DEBUG_MSG("wbuffer_write: %d bytes from wbuffer %p\n",
		wbuffer->region->bpl * wbuffer->area.height, wbuffer);

	VIPS_GATE_START("wbuffer_write: work");

	wbuffer->write_errno = write->write_fn(wbuffer->region,
		&wbuffer->area, write->a);

	VIPS_GATE_STOP("wbuffer_write: work");
}

/* Run this as a thread to do a BG write.
 */
static void
wbuffer_write_thread(void *data, void *user_data)
{
	WriteBuffer *wbuffer = (WriteBuffer *) data;

	for (;;) {
		/* Wait to be told to write.
		 */
		vips_semaphore_down(&wbuffer->go);

		if (wbuffer->kill)
			break;

		/* Now block until the last worker finishes on this buffer.
		 */
		vips_semaphore_downn(&wbuffer->nwrite, 0);

		wbuffer_write(wbuffer);

		/* Signal write complete.
		 */
		vips_semaphore_up(&wbuffer->done);
	}

	/* We are exiting: tell the main thread.
	 */
	vips_semaphore_up(&wbuffer->finish);
}

static WriteBuffer *
wbuffer_new(Write *write)
{
	WriteBuffer *wbuffer;

	if (!(wbuffer = VIPS_NEW(NULL, WriteBuffer)))
		return NULL;
	wbuffer->write = write;
	wbuffer->region = NULL;
	vips_semaphore_init(&wbuffer->go, 0, "go");
	vips_semaphore_init(&wbuffer->nwrite, 0, "nwrite");
	vips_semaphore_init(&wbuffer->done, 0, "done");
	vips_semaphore_init(&wbuffer->finish, 0, "finish");
	wbuffer->write_errno = 0;
	wbuffer->running = FALSE;
	wbuffer->kill = FALSE;

	if (!(wbuffer->region = vips_region_new(write->sink_base.im))) {
		wbuffer_free(wbuffer);
		return NULL;
	}

	/* The worker threads need to be able to move the buffers around.
	 */
	vips__region_no_ownership(wbuffer->region);

	/* Make this last (picks up parts of wbuffer on startup).
	 */
	if (vips_thread_execute("wbuffer", wbuffer_write_thread, wbuffer)) {
		wbuffer_free(wbuffer);
		return NULL;
	}

	wbuffer->running = TRUE;

	return wbuffer;
}

/* Block until the previous write completes, then write the front buffer.
 */
static int
wbuffer_flush(Write *write)
{
	VIPS_DEBUG_MSG("wbuffer_flush:\n");

	/* Block until the other buffer has been written. We have to do this
	 * before we can set this buffer writing or we'll lose output ordering.
	 */
	if (write->buf->area.top > 0) {
		vips_semaphore_down(&write->buf_back->done);

		/* Previous write succeeded?
		 */
		if (write->buf_back->write_errno) {
			vips_error_system(write->buf_back->write_errno,
				"wbuffer_write", "%s", _("write failed"));
			return -1;
		}
	}

	/* Set the background writer going for this buffer.
	 */
	vips_semaphore_up(&write->buf->go);

	return 0;
}

/* Move a wbuffer to a position.
 */
static int
wbuffer_position(WriteBuffer *wbuffer, int top, int height)
{
	VipsRect image, area;
	int result;

	image.left = 0;
	image.top = 0;
	image.width = wbuffer->write->sink_base.im->Xsize;
	image.height = wbuffer->write->sink_base.im->Ysize;

	area.left = 0;
	area.top = top;
	area.width = wbuffer->write->sink_base.im->Xsize;
	area.height = height;

	vips_rect_intersectrect(&area, &image, &wbuffer->area);

	/* The workers take turns to move the buffers.
	 */
	vips__region_take_ownership(wbuffer->region);

	result = vips_region_buffer(wbuffer->region, &wbuffer->area);

	vips__region_no_ownership(wbuffer->region);

	/* This should be an exclusive buffer, hopefully.
	 */
	if (!result)
		g_assert(!wbuffer->region->buffer->done);

	return result;
}

/* Our VipsThreadpoolAllocate function ... move the thread to the next tile
 * that needs doing. If no buffer is available (the bg writer hasn't yet
 * finished with it), we block. If all tiles are done, we return FALSE to end
 * iteration.
 */
static gboolean
wbuffer_allocate_fn(VipsThreadState *state, void *a, gboolean *stop)
{
	WriteThreadState *wstate = (WriteThreadState *) state;
	Write *write = (Write *) a;
	SinkBase *sink_base = (SinkBase *) write;

	VipsRect image;
	VipsRect tile;

	VIPS_DEBUG_MSG("wbuffer_allocate_fn:\n");

	/* Is the state x/y OK? New line or maybe new buffer or maybe even
	 * all done.
	 */
	if (sink_base->x >= write->buf->area.width) {
		sink_base->x = 0;
		sink_base->y += sink_base->tile_height;

		if (sink_base->y >= VIPS_RECT_BOTTOM(&write->buf->area)) {
			VIPS_DEBUG_MSG("wbuffer_allocate_fn: "
						   "finished top = %d, height = %d\n",
				write->buf->area.top, write->buf->area.height);

			/* Block until the write of the previous buffer
			 * is done, then set write of this buffer going.
			 */
			if (wbuffer_flush(write)) {
				*stop = TRUE;
				return -1;
			}

			/* End of image?
			 */
			if (sink_base->y >= sink_base->im->Ysize) {
				*stop = TRUE;
				return 0;
			}

			VIPS_DEBUG_MSG("wbuffer_allocate_fn: "
						   "starting top = %d, height = %d\n",
				sink_base->y, sink_base->n_lines);

			/* Swap buffers.
			 */
			VIPS_SWAP(WriteBuffer *, write->buf, write->buf_back);

			/* Position buf at the new y.
			 */
			if (wbuffer_position(write->buf,
					sink_base->y, sink_base->n_lines)) {
				*stop = TRUE;
				return -1;
			}

			/* This will be the first tile of a new buffer ...
			 * stall for a moment to stress the caching system.
			 */
			state->stall = TRUE;
		}
	}

	/* x, y and buf are good: save params for thread.
	 */
	image.left = 0;
	image.top = 0;
	image.width = sink_base->im->Xsize;
	image.height = sink_base->im->Ysize;
	tile.left = sink_base->x;
	tile.top = sink_base->y;
	tile.width = sink_base->tile_width;
	tile.height = sink_base->tile_height;
	vips_rect_intersectrect(&image, &tile, &state->pos);

	/* The thread needs to know which buffer it's writing to.
	 */
	wstate->buf = write->buf;

	VIPS_DEBUG_MSG("  thread %p allocated "
				   "left = %d, top = %d, width = %d, height = %d\n",
		g_thread_self(),
		tile.left, tile.top, tile.width, tile.height);

	/* Add to the number of writers on the buffer.
	 */
	vips_semaphore_upn(&write->buf->nwrite, -1);

	/* Move state on.
	 */
	sink_base->x += sink_base->tile_width;

	/* Add the number of pixels we've just allocated to progress.
	 */
	sink_base->processed += state->pos.width * state->pos.height;

	return 0;
}

/* Our VipsThreadpoolWork function ... generate a tile!
 */
static int
wbuffer_work_fn(VipsThreadState *state, void *a)
{
	WriteThreadState *wstate = (WriteThreadState *) state;

	int result;

	VIPS_DEBUG_MSG("wbuffer_work_fn: thread %p, %d x %d\n",
		g_thread_self(),
		state->pos.left, state->pos.top);

	result = vips_region_prepare_to(state->reg, wstate->buf->region,
		&state->pos, state->pos.left, state->pos.top);

	VIPS_DEBUG_MSG("wbuffer_work_fn: thread %p result = %d\n",
		g_thread_self(), result);

	/* Tell the bg write thread we've left.
	 */
	vips_semaphore_upn(&wstate->buf->nwrite, 1);

	return result;
}

static void
write_init(Write *write,
	VipsImage *image, VipsRegionWrite write_fn, void *a)
{
	vips_sink_base_init(&write->sink_base, image);

	write->buf = wbuffer_new(write);
	write->buf_back = wbuffer_new(write);
	write->write_fn = write_fn;
	write->a = a;
}

static void
write_free(Write *write)
{
	VIPS_FREEF(wbuffer_free, write->buf);
	VIPS_FREEF(wbuffer_free, write->buf_back);
}

/**
 * VipsRegionWrite:
 * @region: get pixels from here
 * @area: area to write
 * @a: client data
 *
 * The function should write the pixels in @area from @region. @a is the
 * value passed into vips_sink_disc().
 *
 * See also: vips_sink_disc().
 *
 * Returns: 0 on success, -1 on error.
 */

/**
 * vips_sink_disc: (method)
 * @im: image to process
 * @write_fn: (scope call): called for every batch of pixels
 * @a: (closure write_fn): client data
 *
 * vips_sink_disc() loops over @im, top-to-bottom, generating it in sections.
 * As each section is produced, @write_fn is called.
 *
 * @write_fn is always called single-threaded (though not always from the same
 * thread), it's always given image
 * sections in top-to-bottom order, and there are never any gaps.
 *
 * This operation is handy for making image sinks which output to things like
 * disc files. Things like vips_jpegsave(), for example, use this to write
 * images to files in JPEG format.
 *
 * See also: vips_concurrency_set().
 *
 * Returns: 0 on success, -1 on error.
 */
int
vips_sink_disc(VipsImage *im, VipsRegionWrite write_fn, void *a)
{
	Write write;
	int result;

	vips_image_preeval(im);

	write_init(&write, im, write_fn, a);

	result = 0;
	if (!write.buf ||
		!write.buf_back ||
		wbuffer_position(write.buf, 0, write.sink_base.n_lines) ||
		vips_threadpool_run(im,
			write_thread_state_new,
			wbuffer_allocate_fn,
			wbuffer_work_fn,
			vips_sink_base_progress,
			&write))
		result = -1;

	/* Just before allocate signalled stop, it set write.buf writing. We
	 * need to wait for this write to finish.
	 *
	 * We can't just free the buffers (which will wait for the bg threads
	 * to finish), since the bg thread might see the kill before it gets a
	 * chance to write.
	 *
	 * If the pool exited with an error, write.buf might not have been
	 * started (if the allocate failed), and in any case, we don't care if
	 * the final write went through or not.
	 */
	if (!result)
		vips_semaphore_down(&write.buf->done);

	vips_image_posteval(im);

	write_free(&write);

	vips_image_minimise_all(im);

	return result;
}
