/* Copyright (C) 2021 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 "DecalRData.h"

#include "graphics/Decal.h"
#include "graphics/Model.h"
#include "graphics/ShaderManager.h"
#include "graphics/Terrain.h"
#include "graphics/TextureManager.h"
#include "ps/CLogger.h"
#include "ps/Game.h"
#include "ps/Profile.h"
#include "renderer/Renderer.h"
#include "renderer/TerrainRenderer.h"
#include "simulation2/Simulation2.h"
#include "simulation2/components/ICmpWaterManager.h"

// TODO: Currently each decal is a separate CDecalRData. We might want to use
// lots of decals for special effects like shadows, footprints, etc, in which
// case we should probably redesign this to batch them all together for more
// efficient rendering.

CDecalRData::CDecalRData(CModelDecal* decal, CSimulation2* simulation)
	: m_Decal(decal), m_IndexArray(GL_STATIC_DRAW), m_Array(GL_STATIC_DRAW), m_Simulation(simulation)
{
	m_Position.type = GL_FLOAT;
	m_Position.elems = 3;
	m_Array.AddAttribute(&m_Position);

	m_Normal.type = GL_FLOAT;
	m_Normal.elems = 3;
	m_Array.AddAttribute(&m_Normal);

	m_UV.type = GL_FLOAT;
	m_UV.elems = 2;
	m_Array.AddAttribute(&m_UV);

	BuildArrays();
}

CDecalRData::~CDecalRData()
{
}

void CDecalRData::Update(CSimulation2* simulation)
{
	m_Simulation = simulation;
	if (m_UpdateFlags != 0)
	{
		BuildArrays();
		m_UpdateFlags = 0;
	}
}

void CDecalRData::RenderDecals(
	std::vector<CDecalRData*>& decals, const CShaderDefines& context, ShadowMap* shadow)
{
	CShaderDefines contextDecal = context;
	contextDecal.Add(str_DECAL, str_1);

	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	for (size_t i = 0; i < decals.size(); ++i)
	{
		CDecalRData *decal = decals[i];

		CMaterial &material = decal->m_Decal->m_Decal.m_Material;

		if (material.GetShaderEffect().length() == 0)
		{
			LOGERROR("Terrain renderer failed to load shader effect.\n");
			continue;
		}

		CShaderTechniquePtr techBase = g_Renderer.GetShaderManager().LoadEffect(
			material.GetShaderEffect(), contextDecal, material.GetShaderDefines(0));
		if (!techBase)
		{
			LOGERROR("Terrain renderer failed to load shader effect (%s)\n",
					material.GetShaderEffect().string().c_str());
			continue;
		}

		const int numPasses = techBase->GetNumPasses();
		for (int pass = 0; pass < numPasses; ++pass)
		{
			techBase->BeginPass(pass);
			TerrainRenderer::PrepareShader(techBase->GetShader(), shadow);

			const CShaderProgramPtr& shader = techBase->GetShader(pass);

			if (material.GetSamplers().size() != 0)
			{
				const CMaterial::SamplersVector& samplers = material.GetSamplers();
				size_t samplersNum = samplers.size();

				for (size_t s = 0; s < samplersNum; ++s)
				{
					const CMaterial::TextureSampler& samp = samplers[s];
					shader->BindTexture(samp.Name, samp.Sampler);
				}

				material.GetStaticUniforms().BindUniforms(shader);

				// TODO: Need to handle floating decals correctly. In particular, we need
				// to render non-floating before water and floating after water (to get
				// the blending right), and we also need to apply the correct lighting in
				// each case, which doesn't really seem possible with the current
				// TerrainRenderer.
				// Also, need to mark the decals as dirty when water height changes.

				//	glDisable(GL_TEXTURE_2D);
				//	m_Decal->GetBounds().Render();
				//	glEnable(GL_TEXTURE_2D);

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

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

				shader->Uniform(str_shadingColor, decal->m_Decal->GetShadingColor());

				shader->VertexPointer(3, GL_FLOAT, stride, base + decal->m_Position.offset);
				shader->NormalPointer(GL_FLOAT, stride, base + decal->m_Normal.offset);
				shader->TexCoordPointer(GL_TEXTURE0, 2, GL_FLOAT, stride, base + decal->m_UV.offset);

				shader->AssertPointersBound();

				if (!g_Renderer.m_SkipSubmit)
				{
					glDrawElements(GL_TRIANGLES, (GLsizei)decal->m_IndexArray.GetNumVertices(), GL_UNSIGNED_SHORT, indexBase);
				}

				// bump stats
				g_Renderer.m_Stats.m_DrawCalls++;
				g_Renderer.m_Stats.m_TerrainTris += decal->m_IndexArray.GetNumVertices() / 3;

				CVertexBuffer::Unbind();
			}

			techBase->EndPass();
		}
	}

	glDisable(GL_BLEND);
}

void CDecalRData::BuildArrays()
{
	PROFILE("decal build");

	const SDecal& decal = m_Decal->m_Decal;

	// TODO: Currently this constructs an axis-aligned bounding rectangle around
	// the decal. It would be more efficient for rendering if we excluded tiles
	// that are outside the (non-axis-aligned) decal rectangle.

	ssize_t i0, j0, i1, j1;
	m_Decal->CalcVertexExtents(i0, j0, i1, j1);

	// Construct vertex data arrays

	CmpPtr<ICmpWaterManager> cmpWaterManager(*m_Simulation, SYSTEM_ENTITY);

	m_Array.SetNumVertices((i1-i0+1)*(j1-j0+1));
	m_Array.Layout();
	VertexArrayIterator<CVector3D> Position = m_Position.GetIterator<CVector3D>();
	VertexArrayIterator<CVector3D> Normal = m_Normal.GetIterator<CVector3D>();
	VertexArrayIterator<float[2]> UV = m_UV.GetIterator<float[2]>();

	for (ssize_t j = j0; j <= j1; ++j)
	{
		for (ssize_t i = i0; i <= i1; ++i)
		{
			CVector3D pos;
			m_Decal->m_Terrain->CalcPosition(i, j, pos);

			if (decal.m_Floating && cmpWaterManager)
				pos.Y = std::max(pos.Y, cmpWaterManager->GetExactWaterLevel(pos.X, pos.Z));

			*Position = pos;
			++Position;

			CVector3D normal;
			m_Decal->m_Terrain->CalcNormal(i, j, normal);
			*Normal = normal;
			Normal++;

			// Map from world space back into decal texture space
			CVector3D inv = m_Decal->GetInvTransform().Transform(pos);
			(*UV)[0] = 0.5f + (inv.X - decal.m_OffsetX) / decal.m_SizeX;
			(*UV)[1] = 0.5f - (inv.Z - decal.m_OffsetZ) / decal.m_SizeZ; // flip V to match our texture convention
			++UV;
		}
	}

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

	// Construct index arrays for each terrain tile

	m_IndexArray.SetNumVertices((i1-i0)*(j1-j0)*6);
	m_IndexArray.Layout();
	VertexArrayIterator<u16> Index = m_IndexArray.GetIterator();

	u16 base = 0;
	ssize_t w = i1-i0+1;
	for (ssize_t dj = 0; dj < j1-j0; ++dj)
	{
		for (ssize_t di = 0; di < i1-i0; ++di)
		{
			bool dir = m_Decal->m_Terrain->GetTriangulationDir(i0+di, j0+dj);
			if (dir)
			{
				*Index++ = u16(((dj+0)*w+(di+0))+base);
				*Index++ = u16(((dj+0)*w+(di+1))+base);
				*Index++ = u16(((dj+1)*w+(di+0))+base);

				*Index++ = u16(((dj+0)*w+(di+1))+base);
				*Index++ = u16(((dj+1)*w+(di+1))+base);
				*Index++ = u16(((dj+1)*w+(di+0))+base);
			}
			else
			{
				*Index++ = u16(((dj+0)*w+(di+0))+base);
				*Index++ = u16(((dj+0)*w+(di+1))+base);
				*Index++ = u16(((dj+1)*w+(di+1))+base);

				*Index++ = u16(((dj+1)*w+(di+1))+base);
				*Index++ = u16(((dj+1)*w+(di+0))+base);
				*Index++ = u16(((dj+0)*w+(di+0))+base);
			}
		}
	}

	m_IndexArray.Upload();
	m_IndexArray.FreeBackingStore();
}