/*
 * ***** 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) 2016 by Mike Erwin.
 * All rights reserved.
 *
 * Contributor(s): Blender Foundation, Clément Foucault
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/gpu/intern/gwn_vertex_buffer.c
 *  \ingroup gpu
 *
 * Gawain vertex buffer
 */

#include "GPU_vertex_buffer.h"
#include "GPU_buffer_id.h"
#include "gpu_vertex_format_private.h"
#include <stdlib.h>
#include <string.h>

#define KEEP_SINGLE_COPY 1

static uint vbo_memory_usage;

static GLenum convert_usage_type_to_gl(Gwn_UsageType type)
{
	static const GLenum table[] = {
		[GWN_USAGE_STREAM] = GL_STREAM_DRAW,
		[GWN_USAGE_STATIC] = GL_STATIC_DRAW,
		[GWN_USAGE_DYNAMIC] = GL_DYNAMIC_DRAW
	};
	return table[type];
}

Gwn_VertBuf* GWN_vertbuf_create(Gwn_UsageType usage)
{
	Gwn_VertBuf* verts = malloc(sizeof(Gwn_VertBuf));
	GWN_vertbuf_init(verts, usage);
	return verts;
}

Gwn_VertBuf* GWN_vertbuf_create_with_format_ex(const Gwn_VertFormat* format, Gwn_UsageType usage)
{
	Gwn_VertBuf* verts = GWN_vertbuf_create(usage);
	GWN_vertformat_copy(&verts->format, format);
	if (!format->packed) {
		VertexFormat_pack(&verts->format);
	}
	return verts;

	/* this function might seem redundant, but there is potential for memory savings here... */
	/* TODO: implement those memory savings */
}

void GWN_vertbuf_init(Gwn_VertBuf* verts, Gwn_UsageType usage)
{
	memset(verts, 0, sizeof(Gwn_VertBuf));
	verts->usage = usage;
	verts->dirty = true;
}

void GWN_vertbuf_init_with_format_ex(Gwn_VertBuf* verts, const Gwn_VertFormat* format, Gwn_UsageType usage)
{
	GWN_vertbuf_init(verts, usage);
	GWN_vertformat_copy(&verts->format, format);
	if (!format->packed) {
		VertexFormat_pack(&verts->format);
	}
}

void GWN_vertbuf_discard(Gwn_VertBuf* verts)
{
	if (verts->vbo_id) {
		GWN_buf_id_free(verts->vbo_id);
#if VRAM_USAGE
		vbo_memory_usage -= GWN_vertbuf_size_get(verts);
#endif
	}
	if (verts->data) {
		free(verts->data);
	}
	free(verts);
}

uint GWN_vertbuf_size_get(const Gwn_VertBuf* verts)
{
	return vertex_buffer_size(&verts->format, verts->vertex_len);
}

/* create a new allocation, discarding any existing data */
void GWN_vertbuf_data_alloc(Gwn_VertBuf* verts, uint v_len)
{
	Gwn_VertFormat* format = &verts->format;
	if (!format->packed) {
		VertexFormat_pack(format);
	}
#if TRUST_NO_ONE
	/* catch any unnecessary use */
	assert(verts->vertex_alloc != v_len || verts->data == NULL);
#endif
	/* only create the buffer the 1st time */
	if (verts->vbo_id == 0) {
		verts->vbo_id = GWN_buf_id_alloc();
	}
	/* discard previous data if any */
	if (verts->data) {
		free(verts->data);
	}
#if VRAM_USAGE
	uint new_size = vertex_buffer_size(&verts->format, v_len);
	vbo_memory_usage += new_size - GWN_vertbuf_size_get(verts);
#endif
	verts->dirty = true;
	verts->vertex_len = verts->vertex_alloc = v_len;
	verts->data = malloc(sizeof(GLubyte) * GWN_vertbuf_size_get(verts));
}

/* resize buffer keeping existing data */
void GWN_vertbuf_data_resize(Gwn_VertBuf* verts, uint v_len)
{
#if TRUST_NO_ONE
	assert(verts->data != NULL);
	assert(verts->vertex_alloc != v_len);
#endif

#if VRAM_USAGE
	uint new_size = vertex_buffer_size(&verts->format, v_len);
	vbo_memory_usage += new_size - GWN_vertbuf_size_get(verts);
#endif
	verts->dirty = true;
	verts->vertex_len = verts->vertex_alloc = v_len;
	verts->data = realloc(verts->data, sizeof(GLubyte) * GWN_vertbuf_size_get(verts));
}

/* Set vertex count but does not change allocation.
 * Only this many verts will be uploaded to the GPU and rendered.
 * This is usefull for streaming data. */
void GWN_vertbuf_vertex_count_set(Gwn_VertBuf* verts, uint v_len)
{
#if TRUST_NO_ONE
	assert(verts->data != NULL); /* only for dynamic data */
	assert(v_len <= verts->vertex_alloc);
#endif

#if VRAM_USAGE
	uint new_size = vertex_buffer_size(&verts->format, v_len);
	vbo_memory_usage += new_size - GWN_vertbuf_size_get(verts);
#endif
	verts->vertex_len = v_len;
}

void GWN_vertbuf_attr_set(Gwn_VertBuf* verts, uint a_idx, uint v_idx, const void* data)
{
	const Gwn_VertFormat* format = &verts->format;
	const Gwn_VertAttr* a = format->attribs + a_idx;

#if TRUST_NO_ONE
	assert(a_idx < format->attr_len);
	assert(v_idx < verts->vertex_alloc);
	assert(verts->data != NULL);
#endif
	verts->dirty = true;
	memcpy((GLubyte*)verts->data + a->offset + v_idx * format->stride, data, a->sz);
}

void GWN_vertbuf_attr_fill(Gwn_VertBuf* verts, uint a_idx, const void* data)
{
	const Gwn_VertFormat* format = &verts->format;
	const Gwn_VertAttr* a = format->attribs + a_idx;

#if TRUST_NO_ONE
	assert(a_idx < format->attr_len);
#endif
	const uint stride = a->sz; /* tightly packed input data */

	GWN_vertbuf_attr_fill_stride(verts, a_idx, stride, data);
}

void GWN_vertbuf_attr_fill_stride(Gwn_VertBuf* verts, uint a_idx, uint stride, const void* data)
{
	const Gwn_VertFormat* format = &verts->format;
	const Gwn_VertAttr* a = format->attribs + a_idx;

#if TRUST_NO_ONE
	assert(a_idx < format->attr_len);
	assert(verts->data != NULL);
#endif
	verts->dirty = true;
	const uint vertex_len = verts->vertex_len;

	if (format->attr_len == 1 && stride == format->stride) {
		/* we can copy it all at once */
		memcpy(verts->data, data, vertex_len * a->sz);
	}
	else {
		/* we must copy it per vertex */
		for (uint v = 0; v < vertex_len; ++v) {
			memcpy((GLubyte*)verts->data + a->offset + v * format->stride, (const GLubyte*)data + v * stride, a->sz);
		}
	}
}

void GWN_vertbuf_attr_get_raw_data(Gwn_VertBuf* verts, uint a_idx, Gwn_VertBufRaw *access)
{
	const Gwn_VertFormat* format = &verts->format;
	const Gwn_VertAttr* a = format->attribs + a_idx;

#if TRUST_NO_ONE
	assert(a_idx < format->attr_len);
	assert(verts->data != NULL);
#endif

	verts->dirty = true;

	access->size = a->sz;
	access->stride = format->stride;
	access->data = (GLubyte*)verts->data + a->offset;
	access->data_init = access->data;
#if TRUST_NO_ONE
	access->_data_end = access->data_init + (size_t)(verts->vertex_alloc * format->stride);
#endif
}

static void VertBuffer_upload_data(Gwn_VertBuf* verts)
{
	uint buffer_sz = GWN_vertbuf_size_get(verts);

	/* orphan the vbo to avoid sync */
	glBufferData(GL_ARRAY_BUFFER, buffer_sz, NULL, convert_usage_type_to_gl(verts->usage));
	/* upload data */
	glBufferSubData(GL_ARRAY_BUFFER, 0, buffer_sz, verts->data);

	if (verts->usage == GWN_USAGE_STATIC) {
		free(verts->data);
		verts->data = NULL;
	}
	verts->dirty = false;
}

void GWN_vertbuf_use(Gwn_VertBuf* verts)
{
	glBindBuffer(GL_ARRAY_BUFFER, verts->vbo_id);
	if (verts->dirty) {
		VertBuffer_upload_data(verts);
	}
}

uint GWN_vertbuf_get_memory_usage(void)
{
	return vbo_memory_usage;
}