/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * 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, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2011 Blender Foundation.
 * All rights reserved.
 *
 *
 * Contributor(s): Blender Foundation,
 *                 Sergey Sharybin
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/editors/space_clip/clip_editor.c
 *  \ingroup spclip
 */

#include <stddef.h>
#include <errno.h>
#include <sys/types.h>
#include <fcntl.h>

#ifndef WIN32
#  include <unistd.h>
#else
#  include <io.h>
#endif

#include "MEM_guardedalloc.h"

#include "DNA_mask_types.h"

#include "BLI_utildefines.h"
#include "BLI_fileops.h"
#include "BLI_math.h"
#include "BLI_rect.h"
#include "BLI_threads.h"

#include "BKE_global.h"
#include "BKE_main.h"
#include "BKE_movieclip.h"
#include "BKE_context.h"
#include "BKE_tracking.h"
#include "BKE_library.h"

#include "GPU_extensions.h"

#include "IMB_colormanagement.h"
#include "IMB_imbuf_types.h"
#include "IMB_imbuf.h"

#include "ED_screen.h"
#include "ED_clip.h"

#include "WM_api.h"
#include "WM_types.h"

#include "UI_view2d.h"

#include "clip_intern.h"	// own include

/* ******** operactor poll functions ******** */

int ED_space_clip_poll(bContext *C)
{
	SpaceClip *sc = CTX_wm_space_clip(C);

	if (sc && sc->clip)
		return true;

	return false;
}

int ED_space_clip_view_clip_poll(bContext *C)
{
	SpaceClip *sc = CTX_wm_space_clip(C);

	if (sc) {
		return sc->view == SC_VIEW_CLIP;
	}

	return false;
}

int ED_space_clip_tracking_poll(bContext *C)
{
	SpaceClip *sc = CTX_wm_space_clip(C);

	if (sc && sc->clip)
		return ED_space_clip_check_show_trackedit(sc);

	return false;
}

int ED_space_clip_maskedit_poll(bContext *C)
{
	SpaceClip *sc = CTX_wm_space_clip(C);

	if (sc && sc->clip) {
		return ED_space_clip_check_show_maskedit(sc);
	}

	return false;
}

int ED_space_clip_maskedit_mask_poll(bContext *C)
{
	if (ED_space_clip_maskedit_poll(C)) {
		MovieClip *clip = CTX_data_edit_movieclip(C);

		if (clip) {
			SpaceClip *sc = CTX_wm_space_clip(C);

			return sc->mask_info.mask != NULL;
		}
	}

	return false;
}

/* ******** common editing functions ******** */

void ED_space_clip_get_size(SpaceClip *sc, int *width, int *height)
{
	if (sc->clip) {
		BKE_movieclip_get_size(sc->clip, &sc->user, width, height);
	}
	else {
		*width = *height = IMG_SIZE_FALLBACK;
	}
}

void ED_space_clip_get_size_fl(SpaceClip *sc, float size[2])
{
	int size_i[2];
	ED_space_clip_get_size(sc, &size_i[0], &size_i[1]);
	size[0] = size_i[0];
	size[1] = size_i[1];
}

void ED_space_clip_get_zoom(SpaceClip *sc, ARegion *ar, float *zoomx, float *zoomy)
{
	int width, height;

	ED_space_clip_get_size(sc, &width, &height);

	*zoomx = (float)(BLI_rcti_size_x(&ar->winrct) + 1) / (BLI_rctf_size_x(&ar->v2d.cur) * width);
	*zoomy = (float)(BLI_rcti_size_y(&ar->winrct) + 1) / (BLI_rctf_size_y(&ar->v2d.cur) * height);
}

void ED_space_clip_get_aspect(SpaceClip *sc, float *aspx, float *aspy)
{
	MovieClip *clip = ED_space_clip_get_clip(sc);

	if (clip)
		BKE_movieclip_get_aspect(clip, aspx, aspy);
	else
		*aspx = *aspy = 1.0f;

	if (*aspx < *aspy) {
		*aspy = *aspy / *aspx;
		*aspx = 1.0f;
	}
	else {
		*aspx = *aspx / *aspy;
		*aspy = 1.0f;
	}
}

void ED_space_clip_get_aspect_dimension_aware(SpaceClip *sc, float *aspx, float *aspy)
{
	int w, h;

	/* most of tools does not require aspect to be returned with dimensions correction
	 * due to they're invariant to this stuff, but some transformation tools like rotation
	 * should be aware of aspect correction caused by different resolution in different
	 * directions.
	 * mainly this is sued for transformation stuff
	 */

	if (!sc->clip) {
		*aspx = 1.0f;
		*aspy = 1.0f;

		return;
	}

	ED_space_clip_get_aspect(sc, aspx, aspy);
	BKE_movieclip_get_size(sc->clip, &sc->user, &w, &h);

	*aspx *= (float) w;
	*aspy *= (float) h;

	if (*aspx < *aspy) {
		*aspy = *aspy / *aspx;
		*aspx = 1.0f;
	}
	else {
		*aspx = *aspx / *aspy;
		*aspy = 1.0f;
	}
}

/* return current frame number in clip space */
int ED_space_clip_get_clip_frame_number(SpaceClip *sc)
{
	MovieClip *clip = ED_space_clip_get_clip(sc);

	return BKE_movieclip_remap_scene_to_clip_frame(clip, sc->user.framenr);
}

ImBuf *ED_space_clip_get_buffer(SpaceClip *sc)
{
	if (sc->clip) {
		ImBuf *ibuf;

		ibuf = BKE_movieclip_get_postprocessed_ibuf(sc->clip, &sc->user, sc->postproc_flag);

		if (ibuf && (ibuf->rect || ibuf->rect_float))
			return ibuf;

		if (ibuf)
			IMB_freeImBuf(ibuf);
	}

	return NULL;
}

ImBuf *ED_space_clip_get_stable_buffer(SpaceClip *sc, float loc[2], float *scale, float *angle)
{
	if (sc->clip) {
		ImBuf *ibuf;

		ibuf = BKE_movieclip_get_stable_ibuf(sc->clip, &sc->user, loc, scale, angle, sc->postproc_flag);

		if (ibuf && (ibuf->rect || ibuf->rect_float))
			return ibuf;

		if (ibuf)
			IMB_freeImBuf(ibuf);
	}

	return NULL;
}

/* Returns color in the display space, matching ED_space_image_color_sample(). */
bool ED_space_clip_color_sample(Scene *scene, SpaceClip *sc, ARegion *ar, int mval[2], float r_col[3])
{
	const char *display_device = scene->display_settings.display_device;
	struct ColorManagedDisplay *display = IMB_colormanagement_display_get_named(display_device);
	ImBuf *ibuf;
	float fx, fy, co[2];
	bool ret = false;

	ibuf = ED_space_clip_get_buffer(sc);
	if (!ibuf) {
		return false;
	}

	/* map the mouse coords to the backdrop image space */
	ED_clip_mouse_pos(sc, ar, mval, co);

	fx = co[0];
	fy = co[1];

	if (fx >= 0.0f && fy >= 0.0f && fx < 1.0f && fy < 1.0f) {
		const float *fp;
		unsigned char *cp;
		int x = (int)(fx * ibuf->x), y = (int)(fy * ibuf->y);

		CLAMP(x, 0, ibuf->x - 1);
		CLAMP(y, 0, ibuf->y - 1);

		if (ibuf->rect_float) {
			fp = (ibuf->rect_float + (ibuf->channels) * (y * ibuf->x + x));
			copy_v3_v3(r_col, fp);
			ret = true;
		}
		else if (ibuf->rect) {
			cp = (unsigned char *)(ibuf->rect + y * ibuf->x + x);
			rgb_uchar_to_float(r_col, cp);
			IMB_colormanagement_colorspace_to_scene_linear_v3(r_col, ibuf->rect_colorspace);
			ret = true;
		}
	}

	if (ret) {
		IMB_colormanagement_scene_linear_to_display_v3(r_col, display);
	}

	IMB_freeImBuf(ibuf);

	return ret;
}

void ED_clip_update_frame(const Main *mainp, int cfra)
{
	wmWindowManager *wm;
	wmWindow *win;

	/* image window, compo node users */
	for (wm = mainp->wm.first; wm; wm = wm->id.next) { /* only 1 wm */
		for (win = wm->windows.first; win; win = win->next) {
			ScrArea *sa;

			for (sa = win->screen->areabase.first; sa; sa = sa->next) {
				if (sa->spacetype == SPACE_CLIP) {
					SpaceClip *sc = sa->spacedata.first;

					sc->scopes.ok = false;

					BKE_movieclip_user_set_frame(&sc->user, cfra);
				}
			}
		}
	}
}

static bool selected_boundbox(SpaceClip *sc, float min[2], float max[2])
{
	MovieClip *clip = ED_space_clip_get_clip(sc);
	MovieTrackingTrack *track;
	int width, height;
	bool ok = false;
	ListBase *tracksbase = BKE_tracking_get_active_tracks(&clip->tracking);
	int framenr = ED_space_clip_get_clip_frame_number(sc);

	INIT_MINMAX2(min, max);

	ED_space_clip_get_size(sc, &width, &height);

	track = tracksbase->first;
	while (track) {
		if (TRACK_VIEW_SELECTED(sc, track)) {
			MovieTrackingMarker *marker = BKE_tracking_marker_get(track, framenr);

			if (marker) {
				float pos[3];

				pos[0] = marker->pos[0] + track->offset[0];
				pos[1] = marker->pos[1] + track->offset[1];
				pos[2] = 0.0f;

				/* undistortion happens for normalized coords */
				if (sc->user.render_flag & MCLIP_PROXY_RENDER_UNDISTORT) {
					/* undistortion happens for normalized coords */
					ED_clip_point_undistorted_pos(sc, pos, pos);
				}

				pos[0] *= width;
				pos[1] *= height;

				mul_v3_m4v3(pos, sc->stabmat, pos);

				minmax_v2v2_v2(min, max, pos);

				ok = true;
			}
		}

		track = track->next;
	}

	return ok;
}

bool ED_clip_view_selection(const bContext *C, ARegion *ar, bool fit)
{
	SpaceClip *sc = CTX_wm_space_clip(C);
	int w, h, frame_width, frame_height;
	float min[2], max[2];

	ED_space_clip_get_size(sc, &frame_width, &frame_height);

	if ((frame_width == 0) || (frame_height == 0) || (sc->clip == NULL))
		return false;

	if (!selected_boundbox(sc, min, max))
		return false;

	/* center view */
	clip_view_center_to_point(sc, (max[0] + min[0]) / (2 * frame_width),
	                              (max[1] + min[1]) / (2 * frame_height));

	w = max[0] - min[0];
	h = max[1] - min[1];

	/* set zoom to see all selection */
	if (w > 0 && h > 0) {
		int width, height;
		float zoomx, zoomy, newzoom, aspx, aspy;

		ED_space_clip_get_aspect(sc, &aspx, &aspy);

		width  = BLI_rcti_size_x(&ar->winrct) + 1;
		height = BLI_rcti_size_y(&ar->winrct) + 1;

		zoomx = (float)width / w / aspx;
		zoomy = (float)height / h / aspy;

		newzoom = 1.0f / power_of_2(1.0f / min_ff(zoomx, zoomy));

		if (fit || sc->zoom > newzoom)
			sc->zoom = newzoom;
	}

	return true;
}

void ED_clip_point_undistorted_pos(SpaceClip *sc, const float co[2], float r_co[2])
{
	copy_v2_v2(r_co, co);

	if (sc->user.render_flag & MCLIP_PROXY_RENDER_UNDISTORT) {
		MovieClip *clip = ED_space_clip_get_clip(sc);
		float aspy = 1.0f / clip->tracking.camera.pixel_aspect;
		int width, height;

		BKE_movieclip_get_size(sc->clip, &sc->user, &width, &height);

		r_co[0] *= width;
		r_co[1] *= height * aspy;

		BKE_tracking_undistort_v2(&clip->tracking, r_co, r_co);

		r_co[0] /= width;
		r_co[1] /= height * aspy;
	}
}

void ED_clip_point_stable_pos(SpaceClip *sc, ARegion *ar, float x, float y, float *xr, float *yr)
{
	int sx, sy, width, height;
	float zoomx, zoomy, pos[3], imat[4][4];

	ED_space_clip_get_zoom(sc, ar, &zoomx, &zoomy);
	ED_space_clip_get_size(sc, &width, &height);

	UI_view2d_view_to_region(&ar->v2d, 0.0f, 0.0f, &sx, &sy);

	pos[0] = (x - sx) / zoomx;
	pos[1] = (y - sy) / zoomy;
	pos[2] = 0.0f;

	invert_m4_m4(imat, sc->stabmat);
	mul_v3_m4v3(pos, imat, pos);

	*xr = pos[0] / width;
	*yr = pos[1] / height;

	if (sc->user.render_flag & MCLIP_PROXY_RENDER_UNDISTORT) {
		MovieClip *clip = ED_space_clip_get_clip(sc);
		MovieTracking *tracking = &clip->tracking;
		float aspy = 1.0f / tracking->camera.pixel_aspect;
		float tmp[2] = {*xr * width, *yr * height * aspy};

		BKE_tracking_distort_v2(tracking, tmp, tmp);

		*xr = tmp[0] / width;
		*yr = tmp[1] / (height * aspy);
	}
}

/**
 * \brief the reverse of ED_clip_point_stable_pos(), gets the marker region coords.
 * better name here? view_to_track / track_to_view or so?
 */
void ED_clip_point_stable_pos__reverse(SpaceClip *sc, ARegion *ar, const float co[2], float r_co[2])
{
	float zoomx, zoomy;
	float pos[3];
	int width, height;
	int sx, sy;

	UI_view2d_view_to_region(&ar->v2d, 0.0f, 0.0f, &sx, &sy);
	ED_space_clip_get_size(sc, &width, &height);
	ED_space_clip_get_zoom(sc, ar, &zoomx, &zoomy);

	ED_clip_point_undistorted_pos(sc, co, pos);
	pos[2] = 0.0f;

	/* untested */
	mul_v3_m4v3(pos, sc->stabmat, pos);

	r_co[0] = (pos[0] * width  * zoomx) + (float)sx;
	r_co[1] = (pos[1] * height * zoomy) + (float)sy;
}

/* takes event->mval */
void ED_clip_mouse_pos(SpaceClip *sc, ARegion *ar, const int mval[2], float co[2])
{
	ED_clip_point_stable_pos(sc, ar, mval[0], mval[1], &co[0], &co[1]);
}

bool ED_space_clip_check_show_trackedit(SpaceClip *sc)
{
	if (sc) {
		return sc->mode == SC_MODE_TRACKING;
	}

	return false;
}

bool ED_space_clip_check_show_maskedit(SpaceClip *sc)
{
	if (sc) {
		return sc->mode == SC_MODE_MASKEDIT;
	}

	return false;
}

/* ******** clip editing functions ******** */

MovieClip *ED_space_clip_get_clip(SpaceClip *sc)
{
	return sc->clip;
}

void ED_space_clip_set_clip(bContext *C, bScreen *screen, SpaceClip *sc, MovieClip *clip)
{
	MovieClip *old_clip;
	bool old_clip_visible = false;

	if (!screen && C)
		screen = CTX_wm_screen(C);

	old_clip = sc->clip;
	sc->clip = clip;

	id_us_ensure_real((ID *)sc->clip);

	if (screen && sc->view == SC_VIEW_CLIP) {
		ScrArea *area;
		SpaceLink *sl;

		for (area = screen->areabase.first; area; area = area->next) {
			for (sl = area->spacedata.first; sl; sl = sl->next) {
				if (sl->spacetype == SPACE_CLIP) {
					SpaceClip *cur_sc = (SpaceClip *) sl;

					if (cur_sc != sc) {
						if (cur_sc->view == SC_VIEW_CLIP) {
							if (cur_sc->clip == old_clip)
								old_clip_visible = true;
						}
						else {
							if (cur_sc->clip == old_clip || cur_sc->clip == NULL) {
								cur_sc->clip = clip;
							}
						}
					}
				}
			}
		}
	}

	/* If clip is no longer visible on screen, free memory used by it's cache */
	if (old_clip && old_clip != clip && !old_clip_visible) {
		BKE_movieclip_clear_cache(old_clip);
	}

	if (C)
		WM_event_add_notifier(C, NC_MOVIECLIP | NA_SELECTED, sc->clip);
}

/* ******** masking editing functions ******** */

Mask *ED_space_clip_get_mask(SpaceClip *sc)
{
	return sc->mask_info.mask;
}

void ED_space_clip_set_mask(bContext *C, SpaceClip *sc, Mask *mask)
{
	sc->mask_info.mask = mask;

	id_us_ensure_real((ID *)sc->mask_info.mask);

	if (C) {
		WM_event_add_notifier(C, NC_MASK | NA_SELECTED, mask);
	}
}

/* ******** pre-fetching functions ******** */

typedef struct PrefetchJob {
	MovieClip *clip;
	int start_frame, current_frame, end_frame;
	short render_size, render_flag;
} PrefetchJob;

typedef struct PrefetchQueue {
	int initial_frame, current_frame, start_frame, end_frame;
	short render_size, render_flag;

	/* If true prefecthing goes forward in time,
	 * othwewise it goes backwards in time (starting from current frame).
	 */
	bool forward;

	SpinLock spin;

	short *stop;
	short *do_update;
	float *progress;
} PrefetchQueue;

typedef struct PrefetchThread {
	MovieClip *clip;
	PrefetchQueue *queue;
} PrefetchThread;

/* check whether pre-fetching is allowed */
static bool check_prefetch_break(void)
{
	return G.is_break;
}

/* read file for specified frame number to the memory */
static unsigned char *prefetch_read_file_to_memory(MovieClip *clip, int current_frame, short render_size,
                                                   short render_flag, size_t *size_r)
{
	MovieClipUser user = {0};
	char name[FILE_MAX];
	size_t size;
	int file;
	unsigned char *mem;

	user.framenr = current_frame;
	user.render_size = render_size;
	user.render_flag = render_flag;

	BKE_movieclip_filename_for_frame(clip, &user, name);

	file = BLI_open(name, O_BINARY | O_RDONLY, 0);
	if (file == -1) {
		return NULL;
	}

	size = BLI_file_descriptor_size(file);
	if (size < 1) {
		close(file);
		return NULL;
	}

	mem = MEM_mallocN(size, "movieclip prefetch memory file");

	if (read(file, mem, size) != size) {
		close(file);
		MEM_freeN(mem);
		return NULL;
	}

	*size_r = size;

	close(file);

	return mem;
}

/* find first uncached frame within prefetching frame range */
static int prefetch_find_uncached_frame(MovieClip *clip, int from_frame, int end_frame,
                                        short render_size, short render_flag, short direction)
{
	int current_frame;
	MovieClipUser user = {0};

	user.render_size = render_size;
	user.render_flag = render_flag;

	if (direction > 0) {
		for (current_frame = from_frame; current_frame <= end_frame; current_frame++) {
			user.framenr = current_frame;

			if (!BKE_movieclip_has_cached_frame(clip, &user))
				break;
		}
	}
	else {
		for (current_frame = from_frame; current_frame >= end_frame; current_frame--) {
			user.framenr = current_frame;

			if (!BKE_movieclip_has_cached_frame(clip, &user))
				break;
		}
	}

	return current_frame;
}

/* get memory buffer for first uncached frame within prefetch frame range */
static unsigned char *prefetch_thread_next_frame(PrefetchQueue *queue, MovieClip *clip,
                                                 size_t *size_r, int *current_frame_r)
{
	unsigned char *mem = NULL;

	BLI_spin_lock(&queue->spin);
	if (!*queue->stop && !check_prefetch_break() &&
	    IN_RANGE_INCL(queue->current_frame, queue->start_frame, queue->end_frame))
	{
		int current_frame;

		if (queue->forward) {
			current_frame = prefetch_find_uncached_frame(clip, queue->current_frame + 1, queue->end_frame,
			                                             queue->render_size, queue->render_flag, 1);
			/* switch direction if read frames from current up to scene end frames */
			if (current_frame > queue->end_frame) {
				queue->current_frame = queue->initial_frame;
				queue->forward = false;
			}
		}

		if (!queue->forward) {
			current_frame = prefetch_find_uncached_frame(clip, queue->current_frame - 1, queue->start_frame,
			                                             queue->render_size, queue->render_flag, -1);
		}

		if (IN_RANGE_INCL(current_frame, queue->start_frame, queue->end_frame)) {
			int frames_processed;

			mem = prefetch_read_file_to_memory(clip, current_frame, queue->render_size,
			                                   queue->render_flag, size_r);

			*current_frame_r = current_frame;

			queue->current_frame = current_frame;

			if (queue->forward) {
				frames_processed = queue->current_frame - queue->initial_frame;
			}
			else {
				frames_processed = (queue->end_frame - queue->initial_frame) +
				                   (queue->initial_frame - queue->current_frame);
			}

			*queue->do_update = 1;
			*queue->progress = (float)frames_processed / (queue->end_frame - queue->start_frame);
		}
	}
	BLI_spin_unlock(&queue->spin);

	return mem;
}

static void *do_prefetch_thread(void *data_v)
{
	PrefetchThread *data = (PrefetchThread *) data_v;
	MovieClip *clip = data->clip;
	unsigned char *mem;
	size_t size;
	int current_frame;

	while ((mem = prefetch_thread_next_frame(data->queue, data->clip, &size, &current_frame))) {
		ImBuf *ibuf;
		MovieClipUser user = {0};
		int flag = IB_rect | IB_alphamode_detect;
		int result;
		char *colorspace_name = NULL;

		user.framenr = current_frame;
		user.render_size = data->queue->render_size;
		user.render_flag = data->queue->render_flag;

		/* Proxies are stored in the display space. */
		if (data->queue->render_flag & MCLIP_USE_PROXY) {
			colorspace_name = clip->colorspace_settings.name;
		}

		ibuf = IMB_ibImageFromMemory(mem, size, flag, colorspace_name, "prefetch frame");

		result = BKE_movieclip_put_frame_if_possible(data->clip, &user, ibuf);

		IMB_freeImBuf(ibuf);

		MEM_freeN(mem);

		if (!result) {
			/* no more space in the cache, stop reading frames */
			*data->queue->stop = 1;
			break;
		}
	}

	return NULL;
}

static void start_prefetch_threads(MovieClip *clip, int start_frame, int current_frame, int end_frame,
                                   short render_size, short render_flag, short *stop, short *do_update,
                                   float *progress)
{
	ListBase threads;
	PrefetchQueue queue;
	PrefetchThread *handles;
	int tot_thread = BLI_system_thread_count();
	int i;

	/* reserve one thread for the interface */
	if (tot_thread > 1)
		tot_thread--;

	/* initialize queue */
	BLI_spin_init(&queue.spin);

	queue.current_frame = current_frame;
	queue.initial_frame = current_frame;
	queue.start_frame = start_frame;
	queue.end_frame = end_frame;
	queue.render_size = render_size;
	queue.render_flag = render_flag;
	queue.forward = 1;

	queue.stop = stop;
	queue.do_update = do_update;
	queue.progress = progress;

	/* fill in thread handles */
	handles = MEM_callocN(sizeof(PrefetchThread) * tot_thread, "prefetch threaded handles");

	if (tot_thread > 1)
		BLI_init_threads(&threads, do_prefetch_thread, tot_thread);

	for (i = 0; i < tot_thread; i++) {
		PrefetchThread *handle = &handles[i];

		handle->clip = clip;
		handle->queue = &queue;

		if (tot_thread > 1)
			BLI_insert_thread(&threads, handle);
	}

	/* run the threads */
	if (tot_thread > 1)
		BLI_end_threads(&threads);
	else
		do_prefetch_thread(handles);

	MEM_freeN(handles);
}

static bool prefetch_movie_frame(MovieClip *clip, int frame, short render_size,
                                 short render_flag, short *stop)
{
	MovieClipUser user = {0};
	ImBuf *ibuf;

	if (check_prefetch_break() || *stop)
		return false;

	user.framenr = frame;
	user.render_size = render_size;
	user.render_flag = render_flag;

	if (!BKE_movieclip_has_cached_frame(clip, &user)) {
		ibuf = BKE_movieclip_anim_ibuf_for_frame(clip, &user);

		if (ibuf) {
			int result;

			result = BKE_movieclip_put_frame_if_possible(clip, &user, ibuf);

			if (!result) {
				/* no more space in the cache, we could stop prefetching here */
				*stop = 1;
			}

			IMB_freeImBuf(ibuf);
		}
		else {
			/* error reading frame, fair enough stop attempting further reading */
			*stop = 1;
		}
	}

	return true;
}

static void do_prefetch_movie(MovieClip *clip, int start_frame, int current_frame, int end_frame,
                              short render_size, short render_flag, short *stop, short *do_update,
                              float *progress)
{
	int frame;
	int frames_processed = 0;

	/* read frames starting from current frame up to scene end frame */
	for (frame = current_frame; frame <= end_frame; frame++) {
		if (!prefetch_movie_frame(clip, frame, render_size, render_flag, stop))
			return;

		frames_processed++;

		*do_update = 1;
		*progress = (float) frames_processed / (end_frame - start_frame);
	}

	/* read frames starting from current frame up to scene start frame */
	for (frame = current_frame; frame >= start_frame; frame--) {
		if (!prefetch_movie_frame(clip, frame, render_size, render_flag, stop))
			return;

		frames_processed++;

		*do_update = 1;
		*progress = (float) frames_processed / (end_frame - start_frame);
	}
}

static void prefetch_startjob(void *pjv, short *stop, short *do_update, float *progress)
{
	PrefetchJob *pj = pjv;

	if (pj->clip->source == MCLIP_SRC_SEQUENCE) {
		/* read sequence files in multiple threads */
		start_prefetch_threads(pj->clip, pj->start_frame, pj->current_frame, pj->end_frame,
		                       pj->render_size, pj->render_flag,
		                       stop, do_update, progress);
	}
	else if (pj->clip->source == MCLIP_SRC_MOVIE) {
		/* read movie in a single thread */
		do_prefetch_movie(pj->clip, pj->start_frame, pj->current_frame, pj->end_frame,
		                  pj->render_size, pj->render_flag,
		                  stop, do_update, progress);
	}
	else {
		BLI_assert(!"Unknown movie clip source when prefetching frames");
	}
}

static void prefetch_freejob(void *pjv)
{
	PrefetchJob *pj = pjv;

	MEM_freeN(pj);
}

static int prefetch_get_start_frame(const bContext *C)
{
	Scene *scene = CTX_data_scene(C);

	return SFRA;
}

static int prefetch_get_final_frame(const bContext *C)
{
	Scene *scene = CTX_data_scene(C);
	SpaceClip *sc = CTX_wm_space_clip(C);
	MovieClip *clip = ED_space_clip_get_clip(sc);
	int end_frame;

	/* check whether all the frames from prefetch range are cached */
	end_frame = EFRA;

	if (clip->len)
		end_frame = min_ii(end_frame, clip->len);

	return end_frame;
}

/* returns true if early out is possible */
static bool prefetch_check_early_out(const bContext *C)
{
	SpaceClip *sc = CTX_wm_space_clip(C);
	MovieClip *clip = ED_space_clip_get_clip(sc);
	int first_uncached_frame, end_frame;
	int clip_len;

	if (clip == NULL) {
		return true;
	}

	clip_len = BKE_movieclip_get_duration(clip);

	/* check whether all the frames from prefetch range are cached */
	end_frame = prefetch_get_final_frame(C);

	first_uncached_frame =
		prefetch_find_uncached_frame(clip, sc->user.framenr, end_frame,
		                             sc->user.render_size, sc->user.render_flag, 1);

	if (first_uncached_frame > end_frame || first_uncached_frame == clip_len) {
		int start_frame = prefetch_get_start_frame(C);

		first_uncached_frame =
			prefetch_find_uncached_frame(clip, sc->user.framenr, start_frame,
			                             sc->user.render_size, sc->user.render_flag, -1);

		if (first_uncached_frame < start_frame)
			return true;
	}

	return false;
}

void clip_start_prefetch_job(const bContext *C)
{
	wmJob *wm_job;
	PrefetchJob *pj;
	SpaceClip *sc = CTX_wm_space_clip(C);

	if (prefetch_check_early_out(C))
		return;

	wm_job = WM_jobs_get(CTX_wm_manager(C), CTX_wm_window(C), CTX_wm_area(C), "Prefetching",
	                     WM_JOB_PROGRESS, WM_JOB_TYPE_CLIP_PREFETCH);

	/* create new job */
	pj = MEM_callocN(sizeof(PrefetchJob), "prefetch job");
	pj->clip = ED_space_clip_get_clip(sc);
	pj->start_frame = prefetch_get_start_frame(C);
	pj->current_frame = sc->user.framenr;
	pj->end_frame = prefetch_get_final_frame(C);
	pj->render_size = sc->user.render_size;
	pj->render_flag = sc->user.render_flag;

	WM_jobs_customdata_set(wm_job, pj, prefetch_freejob);
	WM_jobs_timer(wm_job, 0.2, NC_MOVIECLIP | ND_DISPLAY, 0);
	WM_jobs_callbacks(wm_job, prefetch_startjob, NULL, NULL, NULL);

	G.is_break = false;

	/* and finally start the job */
	WM_jobs_start(CTX_wm_manager(C), wm_job);
}