#include "sparrowrenderer.h"
#include "deferredpipeline.h"

// renderer
#include "texture.h"
#include "scene.h"
#include "mesh.h"
#include "shader.h"
#include "shadersource.h"
#include "pbrmaterial.h"
#include "camera.h"
#include "skybox.h"
#include "guimesh.h"

// GLM
#include <glm/ext.hpp>

// Stl
#include <algorithm>

// imgui
#include <imgui/imgui.h>

// resource packs
#include <resource.h>

RESOURCE_PACK(shaders)

GBuffer::GBuffer(int width, int height, GLuint renderBuffer) : FrameBuffer()
{
    Texture* tex;
    
    // - Position buffer
    tex = new Texture(GL_RGBA, GL_RGBA16F, width, height, GL_FLOAT, GL_TEXTURE_RECTANGLE);
    tex->setFiltering(GL_NEAREST);
    tex->setUnit(POSITION);
    addTexture(tex, GL_COLOR_ATTACHMENT0);
    
    // - Albedo + Roughness
    tex = new Texture(GL_RGBA, GL_RGBA, width, height, GL_UNSIGNED_BYTE, GL_TEXTURE_RECTANGLE);
    tex->setFiltering(GL_NEAREST);
    tex->setUnit(ALBEDO);
    addTexture(tex, GL_COLOR_ATTACHMENT1);
    
    // - Normal buffer
    tex = new Texture(GL_RGB, GL_RGB16F, width, height, GL_FLOAT, GL_TEXTURE_RECTANGLE);
    tex->setFiltering(GL_NEAREST);
    tex->setUnit(NORMAL);
    addTexture(tex, GL_COLOR_ATTACHMENT2);

    // - Emission + Metallic
    tex = new Texture(GL_RGBA, GL_RGBA, width, height, GL_UNSIGNED_BYTE, GL_TEXTURE_RECTANGLE);
    tex->setFiltering(GL_NEAREST);
    tex->setUnit(EMISSION);
    addTexture(tex, GL_COLOR_ATTACHMENT3);

    addRenderBuffer(renderBuffer, GL_DEPTH_ATTACHMENT);
    addRenderBuffer(renderBuffer, GL_STENCIL_ATTACHMENT);

    initColorAttachments();
}

void GBuffer::bindTextures()
{
    for(int i=0; i<NB_BUFFERS; ++i)
        getTexture(i)->bind();
}

void GBuffer::unbindTextures()
{
    for(int i=0; i<NB_BUFFERS; ++i)
        getTexture(i)->unbind();
}

LightingBuffer::LightingBuffer(int width, int height, GLuint renderBuffer) : FrameBuffer()
{
    // colors are encoded in float to allow tonemapping
    Texture* tex = new Texture(GL_RGBA, GL_RGBA16F, width, height, GL_FLOAT, GL_TEXTURE_RECTANGLE);
    tex->setFiltering(GL_NEAREST);
    addTexture(tex, GL_COLOR_ATTACHMENT0);

    addRenderBuffer(renderBuffer, GL_DEPTH_ATTACHMENT);
    addRenderBuffer(renderBuffer, GL_STENCIL_ATTACHMENT);

    initColorAttachments();
}

DeferredPipeline::DeferredPipeline() :
    m_camera(nullptr),
    m_skybox(nullptr),
    m_width(512),
    m_height(512),
    m_postEffectsShader(nullptr),
    m_depth_stencil_renderBuffer(0),
    m_gBuffer(nullptr),
    m_lightingBuffer(nullptr),
    m_renderTarget(nullptr),
    m_debugGuiEnabled(false),
    m_gammaCorrectEnabled(true),
    m_hdrTonemappingEnabled(false)
{
    Resource::ResourceMap shaderMap;
    Resource::getResourcePack_shaders(shaderMap);
    m_gBufferSource = new ShaderSource();
    m_gBufferSource->setSource(shaderMap["shaders/gbuffer.vert.glsl"], ShaderSource::VERTEX);
    m_gBufferSource->setSource(shaderMap["shaders/gbuffer.frag.glsl"], ShaderSource::FRAGMENT);
    m_lightingSource = new ShaderSource();
    m_lightingSource->setSource(shaderMap["shaders/lighting.vert.glsl"], ShaderSource::VERTEX);
    m_lightingSource->setSource(shaderMap["shaders/lighting.frag.glsl"], ShaderSource::FRAGMENT);
    m_mesh2DSource = new ShaderSource();
    m_mesh2DSource->setSource(shaderMap["shaders/gui.vert.glsl"], ShaderSource::VERTEX);
    m_mesh2DSource->setSource(shaderMap["shaders/gui.frag.glsl"], ShaderSource::FRAGMENT);

    m_postEffectsShaders = new ShaderSource();
    m_postEffectsShaders->setSource(shaderMap["shaders/posteffects.vert.glsl"], ShaderSource::VERTEX);
    m_postEffectsShaders->setSource(shaderMap["shaders/posteffects.frag.glsl"], ShaderSource::FRAGMENT);
    recompilePostEffectsShader();

    m_debugShaders = new ShaderSource();
    m_debugShaders->setSource(shaderMap["shaders/debug.vert.glsl"], ShaderSource::VERTEX);
    m_debugShaders->setSource(shaderMap["shaders/debug.frag.glsl"], ShaderSource::FRAGMENT);


	m_guiMesh = new GuiMesh();
	m_guiMesh->initGL();

    glEnable(GL_TEXTURE_CUBE_MAP_SEAMLESS);
}

bool depthCompare(const GeometryNode* firstElem, const GeometryNode* secondElem) {
  return firstElem->mesh->getDepth() < secondElem->mesh->getDepth();
}

void DeferredPipeline::renderGL(Scene *scene)
{
    if(m_renderTarget == NULL)
        return;

    glViewport(0, 0, m_width, m_height);

    // GEOMETRY PASS
    std::vector<GeometryNode*> mesh2D;
    m_gBuffer->bindFBO();
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_STENCIL_TEST);
    glDepthFunc(GL_LESS);
    glDisable(GL_BLEND);
    glClearColor(0.0f, 0.0f, 0.0f, 1.f);
    glClearDepth(1.0f);
    glClearStencil(0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
    glStencilMask(0x01);
    glStencilFunc(GL_ALWAYS, 0x01, 0x01); // always draw fragments (ignore the stencil buffer values for now)
    // draw skybox
    if(m_skybox != nullptr)
    {
        glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
        m_skybox->renderGL(m_camera);
        glClear(GL_DEPTH_BUFFER_BIT);
    }
    // loop on geometry
    for(SceneIterator<GeometryNode*>* geometryIt = scene->getGeometry();
        geometryIt->isValid(); geometryIt->next())
    {
        GeometryNode* node = geometryIt->getItem();
        unsigned int type = node->mesh->getFlags();
        if(type & (1 << Mesh::MESH_2D))
        {
            mesh2D.push_back(node); // TODO : not every frame
            continue;
        }
        Shader *shader = m_mesh3DShaders[node->mesh->getFlags()];
        if(shader == NULL)
        {
            fprintf(stderr, "no shader to render this 3D geometry, please call refreshScene to generate the shader\n");
            continue;
        }
        shader->bind();

        glm::mat4 modelViewMatrix = m_camera->getViewMatrix() * node->modelMatrix;
        glm::mat4 normalMatrix = glm::transpose(glm::inverse(modelViewMatrix));
        shader->bindMat4(shader->getLocation("projectionMatrix"), m_camera->getProjectionMatrix());
        shader->bindMat4(shader->getLocation("modelViewMatrix"), modelViewMatrix);
        shader->bindMat3(shader->getLocation("normalMatrix"), glm::mat3(normalMatrix));
        // draw geometry
        node->mesh->draw(shader);
    }
    
    // LIGHTING PASS
    m_lightingBuffer->bindFBO();

    glDepthFunc(GL_LEQUAL);
    glEnable(GL_BLEND);
    glEnable(GL_STENCIL_TEST);
    glBlendFunc(GL_ONE, GL_ONE);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
    m_gBuffer->bindTextures();

    // draw unlit fragments

    Shader *shader = m_lightShaders[1 << Light::UNLIT_FLAG];
    if(shader != nullptr)
    {
        shader->bind();
        shader->bindInteger(shader->getLocation("emissionBuffer"), GBuffer::EMISSION);
        glStencilFunc(GL_EQUAL, 1, 0x01);
        SparrowRenderer::drawQuad();
    }

    // loop on light sources
    glStencilFunc(GL_EQUAL, 0, 0x01);
    for(SceneIterator<Light*>* lightIt = scene->getLights();
        lightIt->isValid(); lightIt->next())
    {
        Light* light = lightIt->getItem();
        Shader *shader = m_lightShaders[light->getFlags()];
        if(shader == nullptr)
        {
            fprintf(stderr, "no shader to render this light, please call refreshScene to generate the shader\n");
            continue;
        }
        shader->bind();

        // bind GBuffer
        shader->bindInteger(shader->getLocation("positionBuffer"), GBuffer::POSITION);
        shader->bindInteger(shader->getLocation("albedoBuffer"), GBuffer::ALBEDO);
        shader->bindInteger(shader->getLocation("normalBuffer"), GBuffer::NORMAL);
        shader->bindInteger(shader->getLocation("emissionBuffer"), GBuffer::EMISSION);

        // bind light
        light->bindAttributes(shader, m_camera);

        // compute fragments
        SparrowRenderer::drawQuad();
    }
    m_gBuffer->unbindTextures();
    
    // POST EFFECTS PASS
    m_renderTarget->bindFBO();
    glDisable(GL_BLEND);
    glDisable(GL_STENCIL_TEST);
    glStencilMask(0);
    m_lightingBuffer->getTexture(0)->bind(0);
    m_postEffectsShader->bind();
    m_postEffectsShader->bindInteger(m_postEffectsShader->getLocation("lightBuffer"), 0);
    SparrowRenderer::drawQuad();
    m_lightingBuffer->getTexture(0)->unbind();

    // 2D PASS
    glClear(GL_DEPTH_BUFFER_BIT);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    std::sort(mesh2D.begin(), mesh2D.end(), depthCompare);
    for(GeometryNode* node : mesh2D)
    {
        Shader *shader = m_mesh2DShaders[node->mesh->getFlags()];
        if(shader == NULL)
        {
            fprintf(stderr, "no shader to render this 2D geometry, please call refreshScene to generate the shader\n");
            continue;
        }
        shader->bind();

        shader->bindMat4(shader->getLocation("orthoMatrix"), m_orthoMatrix);
        shader->bindMat4(shader->getLocation("transformMatrix"), node->modelMatrix);
        // draw geometry
        node->mesh->draw(shader);
    }
	
    if(m_debugGuiEnabled)
        gui();

	// IMGUI PASS
    m_guiMesh->drawGL();
}

struct DebugCanvas
{
    glm::ivec2 top_left;
    glm::ivec2 bottom_right;

    void gui()
    {
        if(ImGui::Button("Left"))
        {
            if(top_left.x != -1)
                top_left.x = -1;
            else
                bottom_right.x = 0;
        }
        if(ImGui::Button("Right"))
        {
            if(bottom_right.x != 1)
                bottom_right.x = 1;
            else
                top_left.x = 0;
        }
        if(ImGui::Button("Up"))
        {
            if(top_left.y != 1)
                top_left.y = 1;
            else
                bottom_right.y = 0;
        }
        if(ImGui::Button("Down"))
        {
            if(bottom_right.y != -1)
                bottom_right.y = -1;
            else
                top_left.y = 0;
        }
    }

    void drawCanvas()
    {
        Shader* shader = nullptr;
        shader->bind();
        shader->bindVec2(shader->getLocation("origin"), (top_left+bottom_right)/2);
        shader->bindVec2(shader->getLocation("origin"), top_left-bottom_right);
        SparrowRenderer::drawQuad();
    }
};

void DeferredPipeline::gui()
{
    ImGui::Begin("Rendering Pipeline", &m_debugGuiEnabled);
    if(ImGui::Checkbox("Gamma correction", &m_gammaCorrectEnabled))
        recompilePostEffectsShader();
    if(ImGui::Checkbox("HDR tonemapping", &m_hdrTonemappingEnabled))
        recompilePostEffectsShader();
    if(ImGui::Button("Add a debug canvas"))
    {

    }
    ImGui::End();

    // debug render

}

void DeferredPipeline::recompilePostEffectsShader()
{
    std::vector<const char*> defines;
    if(m_gammaCorrectEnabled)
        defines.push_back("GAMMA_CORRECT");
    if(m_hdrTonemappingEnabled)
        defines.push_back("HDR_TONEMAPPING");
    if(m_postEffectsShader != nullptr)
        delete m_postEffectsShader;
    m_postEffectsShader = m_postEffectsShaders->compile(defines);
}

void DeferredPipeline::setSkybox(Texture* texture)
{
    if(m_skybox != nullptr)
        delete m_skybox;
    m_skybox = nullptr;
    if(texture != nullptr)
    {
        m_skybox = new Skybox(texture);
        m_skybox->resizeGL(m_width, m_height);
    }
}

void DeferredPipeline::resizeGL(int w, int h)
{
    // updating dimensions
    m_width = w;
    m_height = h;
    
    if(m_skybox != nullptr)
        m_skybox->resizeGL(w, h);

    if(m_depth_stencil_renderBuffer != 0)
        glDeleteRenderbuffers(1, &m_depth_stencil_renderBuffer);

    // rebuilding FrameBuffers
    if(m_gBuffer != NULL)
    {
        delete m_gBuffer;
        delete m_lightingBuffer;
    }

    glGenRenderbuffers(1, &m_depth_stencil_renderBuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, m_depth_stencil_renderBuffer);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, w, h);

    m_gBuffer = new GBuffer(w, h, m_depth_stencil_renderBuffer);
    m_lightingBuffer = new LightingBuffer(w, h, m_depth_stencil_renderBuffer);
    m_orthoMatrix = glm::ortho(0.f, float(m_width), float(m_height), 0.f);
	m_guiMesh->resizeGL(w, h);
}

void DeferredPipeline::setSources(ShaderSource *gBufferSource, ShaderSource *lightingSource, ShaderSource *guiSource, Shader *postEffectsShader)
{
    if(m_gBufferSource != NULL)
        delete m_gBufferSource;
    m_gBufferSource = gBufferSource;
    if(m_lightingSource != NULL)
        delete m_lightingSource;
    m_lightingSource = lightingSource;
    if(m_mesh2DSource != NULL)
        delete m_mesh2DSource;
    m_mesh2DSource = guiSource;
    if(m_postEffectsShader != NULL)
        delete m_postEffectsShader;
    m_postEffectsShader = postEffectsShader;
}

void DeferredPipeline::refreshScene(Scene *scene)
{
    // delete previous shaders
    for(auto it : m_mesh3DShaders)
        delete it.second;
    m_mesh3DShaders.clear();
    m_meshTypes.clear();

    // gather all unique mesh flags
    scene->getMeshTypes(m_meshTypes);
    for(unsigned int type : m_meshTypes)
    {
        if(type & (1 << Mesh::MESH_2D))
            m_mesh2DShaders[type] = m_mesh2DSource->compile(type, 0);
        else
            m_mesh3DShaders[type] = m_gBufferSource->compile(type, 0);
    }
    
    for(auto it : m_lightShaders)
        delete it.second;
    m_lightShaders.clear();
    m_lightTypes.clear();
    m_lightTypes.push_back(1 << Light::UNLIT_FLAG);
    scene->getLightTypes(m_lightTypes);
    for(unsigned int type : m_lightTypes)
        m_lightShaders[type] = m_lightingSource->compile(0, type);
}

glm::vec4 DeferredPipeline::pick(int x, int y)
{
    m_gBuffer->setTarget(GL_READ_FRAMEBUFFER);
    m_gBuffer->bindFBO();
	float values[4] = {1};
    glReadPixels(x, y, 1, 1, GL_RGBA, GL_FLOAT, values);
    GLenum err = glGetError();
    while(err != GL_NO_ERROR)
    {
        switch(err)
        {
            case GL_INVALID_ENUM : printf("OpenGL error : GL_INVALID_ENUM\n"); break;
            case GL_INVALID_VALUE : printf("OpenGL error : GL_INVALID_VALUE\n"); break;
            case GL_INVALID_OPERATION : printf("OpenGL error : GL_INVALID_OPERATION\n"); break;
            default : printf("OpenGL error : other\n"); break;
        }
        err = glGetError();
    }
    m_gBuffer->setTarget();
	FrameBuffer::screen->bindFBO();
	return glm::vec4(values[0], values[1], values[2], values[3]);
}