/* SinkMemory an image to a memory buffer, keeping top-to-bottom ordering.
 *
 * For sequential operations we need to keep requests reasonably ordered: we
 * can't let some tiles get very delayed. So we need to stall starting new
 * threads if the last thread gets too far behind.
 *
 * 17/2/12
 * 	- from sinkdisc.c
 * 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 <vips/vips.h>
#include <vips/internal.h>
#include <vips/thread.h>
#include <vips/threadpool.h>
#include <vips/debug.h>

#include "sink.h"

/* A part of the image we are writing.
 */
typedef struct _SinkMemoryArea {
	struct _SinkMemory *memory;

	VipsRect rect;		  /* Part of image this area covers */
	VipsSemaphore nwrite; /* Number of threads writing to this area */
} SinkMemoryArea;

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

	/* We are current writing tiles to area, we'll delay starting a new
	 * area if old_area (the previous position) hasn't completed.
	 */
	SinkMemoryArea *area;
	SinkMemoryArea *old_area;

	/* A region covering the whole of the output image ... we write to
	 * this from many workers with vips_region_prepare_to().
	 */
	VipsRegion *region;
} SinkMemory;

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

	SinkMemoryArea *area;
} SinkMemoryThreadState;

typedef struct _SinkMemoryThreadStateClass {
	VipsThreadStateClass parent_class;

} SinkMemoryThreadStateClass;

G_DEFINE_TYPE(SinkMemoryThreadState,
	sink_memory_thread_state, VIPS_TYPE_THREAD_STATE);

static void
sink_memory_thread_state_class_init(SinkMemoryThreadStateClass *class)
{
	VipsObjectClass *object_class = VIPS_OBJECT_CLASS(class);

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

static void
sink_memory_thread_state_init(SinkMemoryThreadState *state)
{
}

static VipsThreadState *
sink_memory_thread_state_new(VipsImage *image, void *a)
{
	return VIPS_THREAD_STATE(vips_object_new(
		sink_memory_thread_state_get_type(),
		vips_thread_state_set, image, a));
}

static void
sink_memory_area_free(SinkMemoryArea *area)
{
	vips_semaphore_destroy(&area->nwrite);
	g_free(area);
}

static SinkMemoryArea *
sink_memory_area_new(SinkMemory *memory)
{
	SinkMemoryArea *area;

	if (!(area = VIPS_NEW(NULL, SinkMemoryArea)))
		return NULL;
	area->memory = memory;
	vips_semaphore_init(&area->nwrite, 0, "nwrite");

	return area;
}

/* Move an area to a position.
 */
static void
sink_memory_area_position(SinkMemoryArea *area, int top, int height)
{
	SinkMemory *memory = area->memory;

	VipsRect all, rect;

	all.left = 0;
	all.top = 0;
	all.width = memory->sink_base.im->Xsize;
	all.height = memory->sink_base.im->Ysize;

	rect.left = 0;
	rect.top = top;
	rect.width = memory->sink_base.im->Xsize;
	rect.height = height;

	vips_rect_intersectrect(&all, &rect, &area->rect);
}

/* Our VipsThreadpoolAllocate function ... move the thread to the next tile
 * that needs doing. If we fill the current area, we block until the previous
 * area is finished, then swap areas.
 * If all tiles are done, we return FALSE to end
 * iteration.
 */
static gboolean
sink_memory_area_allocate_fn(VipsThreadState *state, void *a, gboolean *stop)
{
	SinkMemoryThreadState *smstate = (SinkMemoryThreadState *) state;
	SinkMemory *memory = (SinkMemory *) a;
	SinkBase *sink_base = (SinkBase *) memory;

	VipsRect image;
	VipsRect tile;

	VIPS_DEBUG_MSG("sink_memory_area_allocate_fn: %p\n", g_thread_self());

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

		if (sink_base->y >= VIPS_RECT_BOTTOM(&memory->area->rect)) {
			/* Block until the previous area is done.
			 */
			if (memory->area->rect.top > 0)
				vips_semaphore_downn(
					&memory->old_area->nwrite, 0);

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

			/* Swap buffers.
			 */
			VIPS_SWAP(SinkMemoryArea *,
				memory->area, memory->old_area);

			/* Position buf at the new y.
			 */
			sink_memory_area_position(memory->area,
				sink_base->y, sink_base->n_lines);
		}
	}

	/* 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 area it's writing to.
	 */
	smstate->area = memory->area;

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

	/* Add to the number of writers on the area.
	 */
	vips_semaphore_upn(&memory->area->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
sink_memory_area_work_fn(VipsThreadState *state, void *a)
{
	SinkMemory *memory = (SinkMemory *) a;
	SinkMemoryThreadState *smstate = (SinkMemoryThreadState *) state;
	SinkMemoryArea *area = smstate->area;

	int result;

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

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

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

	/* Tell the allocator we're done.
	 */
	vips_semaphore_upn(&area->nwrite, 1);

	return result;
}

static void
sink_memory_free(SinkMemory *memory)
{
	VIPS_FREEF(sink_memory_area_free, memory->area);
	VIPS_FREEF(sink_memory_area_free, memory->old_area);
	VIPS_UNREF(memory->region);
}

static int
sink_memory_init(SinkMemory *memory, VipsImage *image)
{
	VipsRect all;

	vips_sink_base_init(&memory->sink_base, image);
	memory->area = NULL;
	memory->old_area = NULL;

	all.left = 0;
	all.top = 0;
	all.width = image->Xsize;
	all.height = image->Ysize;

	if (!(memory->region = vips_region_new(image)) ||
		vips_region_image(memory->region, &all) ||
		!(memory->area = sink_memory_area_new(memory)) ||
		!(memory->old_area = sink_memory_area_new(memory))) {
		sink_memory_free(memory);
		return -1;
	}

	return 0;
}

/**
 * vips_sink_memory:
 * @im: generate this image to memory
 *
 * Loops over @im, generating it to a memory buffer attached to @im. It is
 * used by vips to implement writing to a memory buffer.
 *
 * See also: vips_sink(), vips_get_tile_size(), vips_image_new_memory().
 *
 * Returns: 0 on success, or -1 on error.
 */
int
vips_sink_memory(VipsImage *image)
{
	SinkMemory memory;
	int result;

	if (sink_memory_init(&memory, image))
		return -1;

	vips_image_preeval(image);

	result = 0;
	sink_memory_area_position(memory.area, 0, memory.sink_base.n_lines);
	if (vips_threadpool_run(image,
			sink_memory_thread_state_new,
			sink_memory_area_allocate_fn,
			sink_memory_area_work_fn,
			vips_sink_base_progress,
			&memory))
		result = -1;

	vips_image_posteval(image);

	sink_memory_free(&memory);

	vips_image_minimise_all(image);

	VIPS_DEBUG_MSG("vips_sink_memory: done\n");

	return result;
}
