/*
 *	Copyright (C) 2011-2011 Gregory hainaut
 *	Copyright (C) 2007-2009 Gabest
 *
 *  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, 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 GNU Make; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 *  http://www.gnu.org/copyleft/gpl.html
 *
 */

// Note: it is same code that was developed for GSdx plugin

#pragma once

#ifdef GLSL4_API
struct GSInputLayoutOGL {
	GLuint  index;
	GLint   size;
	GLenum  type;
	GLboolean normalize;
	GLsizei stride;
	const GLvoid* offset;
};

class GSBufferOGL {
	size_t m_stride;
	size_t m_start;
	size_t m_count;
	size_t m_limit;
	GLenum m_target;
	GLuint m_buffer;
	size_t m_default_size;

	public: 
	GSBufferOGL(GLenum target, size_t stride) : 
		m_stride(stride)
		, m_start(0)
		, m_count(0)
		, m_limit(0)
		, m_target(target)
	{
		glGenBuffers(1, &m_buffer);
		// Opengl works best with 1-4MB buffer.
		m_default_size = 2 * 1024 * 1024 / m_stride;
	}

	~GSBufferOGL() { glDeleteBuffers(1, &m_buffer); }

	void allocate() { allocate(m_default_size); }

	void allocate(size_t new_limit)
	{
		m_start = 0;
		m_limit = new_limit;
		glBufferData(m_target,  m_limit * m_stride, NULL, GL_STREAM_DRAW);
	}

	void bind()
	{
		glBindBuffer(m_target, m_buffer);
	}

	void upload(const void* src, uint32 count)
	{
		// Upload the data to the buffer
		void* dst;
		if (Map(&dst, count)) {
			// FIXME which one to use
			// GSVector4i::storent(dst, src, m_count * m_stride);
			memcpy(dst, src, m_stride*m_count);
			Unmap();
		}
	}

	bool Map(void** pointer, uint32 count ) {
#ifdef OGL_DEBUG
		GLint b_size = -1;
		glGetBufferParameteriv(m_target, GL_BUFFER_SIZE, &b_size);

		if (b_size <= 0) return false;
#endif

		m_count = count;

		// Note: For an explanation of the map flag
		// see http://www.opengl.org/wiki/Buffer_Object_Streaming
		uint32 map_flags = GL_MAP_WRITE_BIT | GL_MAP_UNSYNCHRONIZED_BIT;

		// Current GPU buffer is really too small need to allocate a new one
		if (m_count > m_limit) {
			allocate(std::max<int>(m_count * 3 / 2, m_default_size));

		} else if (m_count > (m_limit - m_start) ) {
			// Not enough left free room. Just go back at the beginning
			m_start = 0;

			// Tell the driver that it can orphan previous buffer and restart from a scratch buffer.
			// Technically the buffer will not be accessible by the application anymore but the
			// GL will effectively remove it when draws call are finised.
			map_flags |= GL_MAP_INVALIDATE_BUFFER_BIT;
		} else {
			// Tell the driver that it doesn't need to contain any valid buffer data, and that you promise to write the entire range you map
			map_flags |= GL_MAP_INVALIDATE_RANGE_BIT;
		}

		// Upload the data to the buffer
		*pointer = (uint8*) glMapBufferRange(m_target, m_stride*m_start, m_stride*m_count, map_flags);
		//fprintf(stderr, "Map %x from %d to %d\n", *pointer, m_start, m_start+m_count);
#ifdef OGL_DEBUG
		if (*pointer == NULL) {
			fprintf(stderr, "CRITICAL ERROR map failed for vb!!!\n");
			return false;
		}
#endif
		return true;
	}

	void Unmap() { glUnmapBuffer(m_target); }

	void EndScene()
	{
		m_start += m_count;
		m_count = 0;
	}

	void Draw(GLenum mode)
	{
		glDrawArrays(mode, m_start, m_count);
	}

	void Draw(GLenum mode, GLint basevertex)
	{
		glDrawElementsBaseVertex(mode, m_count, GL_UNSIGNED_INT, (void*)(m_start * m_stride), basevertex);
	}

	void Draw(GLenum mode, GLint basevertex, int offset, int count)
	{
		glDrawElementsBaseVertex(mode, count, GL_UNSIGNED_INT, (void*)((m_start + offset) * m_stride), basevertex);
	}

	size_t GetStart() { return m_start; }

	void debug() 
	{
		fprintf(stderr, "data buffer: start %d, count %d\n", m_start, m_count);
	}

};

class GSVertexBufferStateOGL {
	GSBufferOGL *m_vb;
	GSBufferOGL *m_ib;

	GLuint m_va;
	GLenum m_topology;

	// DEBUG
	vector<GSInputLayoutOGL> layout_store;

public:
	GSVertexBufferStateOGL(size_t stride, GSInputLayoutOGL* layout, uint32 layout_nbr)
	{
		glGenVertexArrays(1, &m_va);
		layout_store.clear();

		m_vb = new GSBufferOGL(GL_ARRAY_BUFFER, stride);
		m_ib = new GSBufferOGL(GL_ELEMENT_ARRAY_BUFFER, sizeof(uint32));

		bind();
		// Note: index array are part of the VA state so it need to be bind only once.
		m_ib->bind();

		m_vb->allocate();
		m_ib->allocate();
		set_internal_format(layout, layout_nbr);
	}

	void bind()
	{
		glBindVertexArray(m_va);
		m_vb->bind();
	}

	void set_internal_format()
	{
		for (vector<GSInputLayoutOGL>::iterator it = layout_store.begin(); it != layout_store.end(); it++)
			set_internal_format(*it);
	}

	void set_internal_format(GSInputLayoutOGL& layout) {
		// Note this function need both a vertex array object and a GL_ARRAY_BUFFER buffer
		glEnableVertexAttribArray(layout.index);
		switch (layout.type) {
			case GL_UNSIGNED_SHORT:
			case GL_UNSIGNED_INT:
			case GL_SHORT:
			case GL_INT:
				// Rule: when shader use integral (not normalized) you must use glVertexAttribIPointer (note the extra I)
				if (layout.normalize == false)
					glVertexAttribIPointer(layout.index, layout.size, layout.type, layout.stride, layout.offset);
				else
					glVertexAttribPointer(layout.index, layout.size, layout.type, layout.normalize,  layout.stride, layout.offset);
				break;
			default:
				glVertexAttribPointer(layout.index, layout.size, layout.type, layout.normalize,  layout.stride, layout.offset);
				break;
		}
	}

	void set_internal_format(GSInputLayoutOGL* layout, uint32 layout_nbr)
	{
		for (uint i = 0; i < layout_nbr; i++) {
			// DEBUG
			layout_store.push_back(layout[i]);

			set_internal_format(layout[i]);
		}
	}

	void EndScene()
	{
		m_vb->EndScene();
		m_ib->EndScene();
	}

	void DrawPrimitive() { m_vb->Draw(m_topology); }

	void DrawIndexedPrimitive() { m_ib->Draw(m_topology, m_vb->GetStart() ); }

	void DrawIndexedPrimitive(int offset, int count) { m_ib->Draw(m_topology, m_vb->GetStart(), offset, count ); }

	void SetTopology(GLenum topology) { m_topology = topology; }

	void UploadVB(const void* vertices, size_t count) { m_vb->upload(vertices, count); }

	void UploadIB(const void* index, size_t count) { m_ib->upload(index, count); }

	bool MapVB(void **pointer, size_t count) { return m_vb->Map(pointer, count); }

	void UnmapVB() { m_vb->Unmap(); }

	~GSVertexBufferStateOGL()
	{
		glDeleteVertexArrays(1, &m_va);
		delete m_vb;
		delete m_ib;
	}

	void debug()
	{
		string topo;
		switch (m_topology) {
			case GL_POINTS:
				topo = "point";
				break;
			case GL_LINES:
				topo = "line";
				break;
			case GL_TRIANGLES: 
				topo = "triangle";
				break;
			case GL_TRIANGLE_STRIP:
				topo = "triangle strip";
				break;
		}
		m_vb->debug();
		m_ib->debug();
		fprintf(stderr, "primitives of %s\n", topo.c_str());

	}
};
#endif