/******************************************************************************
    Copyright (C) 2023 by Lain Bailey <lain@obsproject.com>

    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 <http://www.gnu.org/licenses/>.
******************************************************************************/

#include "gl-subsystem.h"

static bool create_pixel_pack_buffer(struct gs_stage_surface *surf)
{
	GLsizeiptr size;
	bool success = true;

	if (!gl_gen_buffers(1, &surf->pack_buffer))
		return false;

	if (!gl_bind_buffer(GL_PIXEL_PACK_BUFFER, surf->pack_buffer))
		return false;

	size = surf->width * surf->bytes_per_pixel;
	size = (size + 3) & 0xFFFFFFFC; /* align width to 4-byte boundary */
	size *= surf->height;

	glBufferData(GL_PIXEL_PACK_BUFFER, size, 0, GL_DYNAMIC_READ);
	if (!gl_success("glBufferData"))
		success = false;

	if (!gl_bind_buffer(GL_PIXEL_PACK_BUFFER, 0))
		success = false;

	return success;
}

gs_stagesurf_t *device_stagesurface_create(gs_device_t *device, uint32_t width, uint32_t height,
					   enum gs_color_format color_format)
{
	struct gs_stage_surface *surf;
	surf = bzalloc(sizeof(struct gs_stage_surface));
	surf->device = device;
	surf->format = color_format;
	surf->width = width;
	surf->height = height;
	surf->gl_format = convert_gs_format(color_format);
	surf->gl_internal_format = convert_gs_internal_format(color_format);
	surf->gl_type = get_gl_format_type(color_format);
	surf->bytes_per_pixel = gs_get_format_bpp(color_format) / 8;

	if (!create_pixel_pack_buffer(surf)) {
		blog(LOG_ERROR, "device_stagesurface_create (GL) failed");
		gs_stagesurface_destroy(surf);
		return NULL;
	}

	return surf;
}

void gs_stagesurface_destroy(gs_stagesurf_t *stagesurf)
{
	if (stagesurf) {
		if (stagesurf->pack_buffer)
			gl_delete_buffers(1, &stagesurf->pack_buffer);

		bfree(stagesurf);
	}
}

static bool can_stage(struct gs_stage_surface *dst, struct gs_texture_2d *src)
{
	if (!src) {
		blog(LOG_ERROR, "Source texture is NULL");
		return false;
	}

	if (src->base.type != GS_TEXTURE_2D) {
		blog(LOG_ERROR, "Source texture must be a 2D texture");
		return false;
	}

	if (!dst) {
		blog(LOG_ERROR, "Destination surface is NULL");
		return false;
	}

	if (src->base.format != dst->format) {
		blog(LOG_ERROR, "Source and destination formats do not match");
		return false;
	}

	if (src->width != dst->width || src->height != dst->height) {
		blog(LOG_ERROR, "Source and destination must have the same "
				"dimensions");
		return false;
	}

	return true;
}

#ifdef __APPLE__

/* Apparently for mac, PBOs won't do an asynchronous transfer unless you use
 * FBOs along with glReadPixels, which is really dumb. */
void device_stage_texture(gs_device_t *device, gs_stagesurf_t *dst, gs_texture_t *src)
{
	struct gs_texture_2d *tex2d = (struct gs_texture_2d *)src;
	struct fbo_info *fbo;
	GLint last_fbo;
	bool success = false;

	if (!can_stage(dst, tex2d))
		goto failed;

	if (!gl_bind_buffer(GL_PIXEL_PACK_BUFFER, dst->pack_buffer))
		goto failed;

	fbo = get_fbo(src, dst->width, dst->height);

	if (!gl_get_integer_v(GL_READ_FRAMEBUFFER_BINDING, &last_fbo))
		goto failed_unbind_buffer;
	if (!gl_bind_framebuffer(GL_READ_FRAMEBUFFER, fbo->fbo))
		goto failed_unbind_buffer;

	glFramebufferTexture2D(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + 0, src->gl_target, src->texture, 0);
	if (!gl_success("glFrameBufferTexture2D"))
		goto failed_unbind_all;

	glReadPixels(0, 0, dst->width, dst->height, dst->gl_format, dst->gl_type, 0);
	if (!gl_success("glReadPixels"))
		goto failed_unbind_all;

	success = true;

failed_unbind_all:
	gl_bind_framebuffer(GL_READ_FRAMEBUFFER, last_fbo);

failed_unbind_buffer:
	gl_bind_buffer(GL_PIXEL_PACK_BUFFER, 0);

failed:
	if (!success)
		blog(LOG_ERROR, "device_stage_texture (GL) failed");

	UNUSED_PARAMETER(device);
}

#else

void device_stage_texture(gs_device_t *device, gs_stagesurf_t *dst, gs_texture_t *src)
{
	struct gs_texture_2d *tex2d = (struct gs_texture_2d *)src;
	if (!can_stage(dst, tex2d))
		goto failed;

	if (!gl_bind_buffer(GL_PIXEL_PACK_BUFFER, dst->pack_buffer))
		goto failed;
	if (!gl_bind_texture(GL_TEXTURE_2D, tex2d->base.texture))
		goto failed;

	glGetTexImage(GL_TEXTURE_2D, 0, dst->gl_format, dst->gl_type, 0);
	if (!gl_success("glGetTexImage"))
		goto failed;

	gl_bind_texture(GL_TEXTURE_2D, 0);
	gl_bind_buffer(GL_PIXEL_PACK_BUFFER, 0);
	return;

failed:
	gl_bind_buffer(GL_PIXEL_PACK_BUFFER, 0);
	gl_bind_texture(GL_TEXTURE_2D, 0);
	blog(LOG_ERROR, "device_stage_texture (GL) failed");

	UNUSED_PARAMETER(device);
}

#endif

uint32_t gs_stagesurface_get_width(const gs_stagesurf_t *stagesurf)
{
	return stagesurf->width;
}

uint32_t gs_stagesurface_get_height(const gs_stagesurf_t *stagesurf)
{
	return stagesurf->height;
}

enum gs_color_format gs_stagesurface_get_color_format(const gs_stagesurf_t *stagesurf)
{
	return stagesurf->format;
}

bool gs_stagesurface_map(gs_stagesurf_t *stagesurf, uint8_t **data, uint32_t *linesize)
{
	if (!gl_bind_buffer(GL_PIXEL_PACK_BUFFER, stagesurf->pack_buffer))
		goto fail;

	*data = glMapBuffer(GL_PIXEL_PACK_BUFFER, GL_READ_ONLY);
	if (!gl_success("glMapBuffer"))
		goto fail;

	gl_bind_buffer(GL_PIXEL_PACK_BUFFER, 0);

	*linesize = stagesurf->bytes_per_pixel * stagesurf->width;
	return true;

fail:
	blog(LOG_ERROR, "stagesurf_map (GL) failed");
	return false;
}

void gs_stagesurface_unmap(gs_stagesurf_t *stagesurf)
{
	if (!gl_bind_buffer(GL_PIXEL_PACK_BUFFER, stagesurf->pack_buffer))
		return;

	glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
	gl_success("glUnmapBuffer");

	gl_bind_buffer(GL_PIXEL_PACK_BUFFER, 0);
}
