/* Copyright (C) 2018 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. 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.
 *
 * 0 A.D. 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 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "precompiled.h"

#include "lib/bits.h"
#include "lib/ogl.h"
#include "lib/sysdep/rtl.h"
#include "maths/Vector3D.h"

#include "graphics/Color.h"
#include "graphics/LightEnv.h"
#include "graphics/Model.h"
#include "graphics/ModelDef.h"
#include "graphics/ShaderProgram.h"

#include "renderer/HWLightingModelRenderer.h"
#include "renderer/Renderer.h"
#include "renderer/RenderModifiers.h"
#include "renderer/VertexArray.h"


struct ShaderModelDef : public CModelDefRPrivate
{
	/// Indices are the same for all models, so share them
	VertexIndexArray m_IndexArray;

	/// Static per-CModelDef vertex array
	VertexArray m_Array;

	/// The number of UVs is determined by the model
	std::vector<VertexArray::Attribute> m_UVs;

	ShaderModelDef(const CModelDefPtr& mdef);
};


ShaderModelDef::ShaderModelDef(const CModelDefPtr& mdef)
	: m_IndexArray(GL_STATIC_DRAW), m_Array(GL_STATIC_DRAW)
{
	size_t numVertices = mdef->GetNumVertices();

	m_UVs.resize(mdef->GetNumUVsPerVertex());
	for (size_t i = 0; i < mdef->GetNumUVsPerVertex(); ++i)
	{
		m_UVs[i].type = GL_FLOAT;
		m_UVs[i].elems = 2;
		m_Array.AddAttribute(&m_UVs[i]);
	}

	m_Array.SetNumVertices(numVertices);
	m_Array.Layout();

	for (size_t i = 0; i < mdef->GetNumUVsPerVertex(); ++i)
	{
		VertexArrayIterator<float[2]> UVit = m_UVs[i].GetIterator<float[2]>();
		ModelRenderer::BuildUV(mdef, UVit, i);
	}

	m_Array.Upload();
	m_Array.FreeBackingStore();

	m_IndexArray.SetNumVertices(mdef->GetNumFaces()*3);
	m_IndexArray.Layout();
	ModelRenderer::BuildIndices(mdef, m_IndexArray.GetIterator());
	m_IndexArray.Upload();
	m_IndexArray.FreeBackingStore();
}


struct ShaderModel : public CModelRData
{
	/// Dynamic per-CModel vertex array
	VertexArray m_Array;

	/// Position and normals/lighting are recalculated on CPU every frame
	VertexArray::Attribute m_Position;
	VertexArray::Attribute m_Normal; // valid iff cpuLighting == false
	VertexArray::Attribute m_Color; // valid iff cpuLighting == true

	ShaderModel(const void* key) : CModelRData(key), m_Array(GL_DYNAMIC_DRAW) { }
};


struct ShaderModelRendererInternals
{
	bool cpuLighting;

	/**
	 * Scratch space for normal vector calculation.
	 * Only used if cpuLighting == true.
	 * Space is reserved so we don't have to do frequent reallocations.
	 * Allocated with rtl_AllocateAligned(normalsNumVertices*16, 16) for SSE writes.
	 */
	char* normals;
	size_t normalsNumVertices;

	/// Previously prepared modeldef
	ShaderModelDef* shadermodeldef;
};


// Construction and Destruction
ShaderModelVertexRenderer::ShaderModelVertexRenderer(bool cpuLighting)
{
	m = new ShaderModelRendererInternals;
	m->cpuLighting = cpuLighting;
	m->normals = NULL;
	m->normalsNumVertices = 0;
	m->shadermodeldef = NULL;
}

ShaderModelVertexRenderer::~ShaderModelVertexRenderer()
{
	rtl_FreeAligned(m->normals);

	delete m;
}


// Build model data (and modeldef data if necessary)
CModelRData* ShaderModelVertexRenderer::CreateModelData(const void* key, CModel* model)
{
	CModelDefPtr mdef = model->GetModelDef();
	ShaderModelDef* shadermodeldef = (ShaderModelDef*)mdef->GetRenderData(m);

	if (!shadermodeldef)
	{
		shadermodeldef = new ShaderModelDef(mdef);
		mdef->SetRenderData(m, shadermodeldef);
	}

	// Build the per-model data
	ShaderModel* shadermodel = new ShaderModel(key);

	if (m->cpuLighting)
	{
		// Positions must be 16-byte aligned for SSE writes.
		// We can pack the color after the position; it will be corrupted by
		// BuildPositionAndNormals, but that's okay since we'll recompute the
		// colors afterwards.

		shadermodel->m_Color.type = GL_UNSIGNED_BYTE;
		shadermodel->m_Color.elems = 4;
		shadermodel->m_Array.AddAttribute(&shadermodel->m_Color);

		shadermodel->m_Position.type = GL_FLOAT;
		shadermodel->m_Position.elems = 3;
		shadermodel->m_Array.AddAttribute(&shadermodel->m_Position);
	}
	else
	{
		// Positions and normals must be 16-byte aligned for SSE writes.

		shadermodel->m_Position.type = GL_FLOAT;
		shadermodel->m_Position.elems = 4;
		shadermodel->m_Array.AddAttribute(&shadermodel->m_Position);

		shadermodel->m_Normal.type = GL_FLOAT;
		shadermodel->m_Normal.elems = 4;
		shadermodel->m_Array.AddAttribute(&shadermodel->m_Normal);
	}

	shadermodel->m_Array.SetNumVertices(mdef->GetNumVertices());
	shadermodel->m_Array.Layout();

	// Verify alignment
	ENSURE(shadermodel->m_Position.offset % 16 == 0);
	if (!m->cpuLighting)
		ENSURE(shadermodel->m_Normal.offset % 16 == 0);
	ENSURE(shadermodel->m_Array.GetStride() % 16 == 0);

	return shadermodel;
}


// Fill in and upload dynamic vertex array
void ShaderModelVertexRenderer::UpdateModelData(CModel* model, CModelRData* data, int updateflags)
{
	ShaderModel* shadermodel = static_cast<ShaderModel*>(data);

	if (!m->cpuLighting && (updateflags & RENDERDATA_UPDATE_VERTICES))
	{
		// build vertices
		VertexArrayIterator<CVector3D> Position = shadermodel->m_Position.GetIterator<CVector3D>();
		VertexArrayIterator<CVector3D> Normal = shadermodel->m_Normal.GetIterator<CVector3D>();

		ModelRenderer::BuildPositionAndNormals(model, Position, Normal);

		// upload everything to vertex buffer
		shadermodel->m_Array.Upload();
	}

	if (m->cpuLighting && (updateflags & (RENDERDATA_UPDATE_VERTICES|RENDERDATA_UPDATE_COLOR)))
	{
		CModelDefPtr mdef = model->GetModelDef();
		size_t numVertices = mdef->GetNumVertices();

		// allocate working space for computing normals
		if (numVertices > m->normalsNumVertices)
		{
			rtl_FreeAligned(m->normals);

			size_t newSize = round_up_to_pow2(numVertices);
			m->normals = (char*)rtl_AllocateAligned(newSize*16, 16);
			m->normalsNumVertices = newSize;
		}

		VertexArrayIterator<CVector3D> Position = shadermodel->m_Position.GetIterator<CVector3D>();
		VertexArrayIterator<CVector3D> Normal = VertexArrayIterator<CVector3D>(m->normals, 16);

		ModelRenderer::BuildPositionAndNormals(model, Position, Normal);

		VertexArrayIterator<SColor4ub> Color = shadermodel->m_Color.GetIterator<SColor4ub>();

		ModelRenderer::BuildColor4ub(model, Normal, Color);

		// upload everything to vertex buffer
		shadermodel->m_Array.Upload();
	}

	shadermodel->m_Array.PrepareForRendering();
}


// Setup one rendering pass
void ShaderModelVertexRenderer::BeginPass(int streamflags)
{
	if (m->cpuLighting)
		ENSURE(streamflags == (streamflags & (STREAM_POS | STREAM_UV0 | STREAM_UV1 | STREAM_COLOR)));
	else
		ENSURE(streamflags == (streamflags & (STREAM_POS | STREAM_UV0 | STREAM_UV1 | STREAM_NORMAL)));
}

// Cleanup one rendering pass
void ShaderModelVertexRenderer::EndPass(int UNUSED(streamflags))
{
	CVertexBuffer::Unbind();
}


// Prepare UV coordinates for this modeldef
void ShaderModelVertexRenderer::PrepareModelDef(const CShaderProgramPtr& shader, int streamflags, const CModelDef& def)
{
	m->shadermodeldef = (ShaderModelDef*)def.GetRenderData(m);

	ENSURE(m->shadermodeldef);

	u8* base = m->shadermodeldef->m_Array.Bind();
	GLsizei stride = (GLsizei)m->shadermodeldef->m_Array.GetStride();

	if (streamflags & STREAM_UV0)
		shader->TexCoordPointer(GL_TEXTURE0, 2, GL_FLOAT, stride, base + m->shadermodeldef->m_UVs[0].offset);

	if ((streamflags & STREAM_UV1) && def.GetNumUVsPerVertex() >= 2)
		shader->TexCoordPointer(GL_TEXTURE1, 2, GL_FLOAT, stride, base + m->shadermodeldef->m_UVs[1].offset);
}


// Render one model
void ShaderModelVertexRenderer::RenderModel(const CShaderProgramPtr& shader, int streamflags, CModel* model, CModelRData* data)
{
	CModelDefPtr mdldef = model->GetModelDef();
	ShaderModel* shadermodel = static_cast<ShaderModel*>(data);

	u8* base = shadermodel->m_Array.Bind();
	GLsizei stride = (GLsizei)shadermodel->m_Array.GetStride();

	u8* indexBase = m->shadermodeldef->m_IndexArray.Bind();

	if (streamflags & STREAM_POS)
		shader->VertexPointer(3, GL_FLOAT, stride, base + shadermodel->m_Position.offset);

	if (streamflags & STREAM_NORMAL)
		shader->NormalPointer(GL_FLOAT, stride, base + shadermodel->m_Normal.offset);

	if (streamflags & STREAM_COLOR)
		shader->ColorPointer(3, GL_UNSIGNED_BYTE, stride, base + shadermodel->m_Color.offset);

	shader->AssertPointersBound();

	// render the lot
	size_t numFaces = mdldef->GetNumFaces();

	if (!g_Renderer.m_SkipSubmit)
	{
		// Draw with DrawRangeElements where available, since it might be more efficient
#if CONFIG2_GLES
		glDrawElements(GL_TRIANGLES, (GLsizei)numFaces*3, GL_UNSIGNED_SHORT, indexBase);
#else
		pglDrawRangeElementsEXT(GL_TRIANGLES, 0, (GLuint)mdldef->GetNumVertices()-1,
			(GLsizei)numFaces*3, GL_UNSIGNED_SHORT, indexBase);
#endif
	}

	// bump stats
	g_Renderer.m_Stats.m_DrawCalls++;
	g_Renderer.m_Stats.m_ModelTris += numFaces;
}