#include <iostream>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <unordered_map>
#include <cmath>
#include <cstring>

#include "common/utils/Types.h"
#include "client/GameClient.h"
#include "client/input/Keys.h"
#include "client/input/MouseButtons.h"
#include "client/rendering/Shader.h"
#include "client/rendering/FontRenderer.h"
#include "client/rendering/Mesh.h"
#include "client/rendering/Framebuffer.h"
#include "client/Utils.h"
#include "client/math/Camera.h"
#include "client/math/Matrix.h"
#include "client/math/MatrixStack.h"
#include "client/Game.h"
#include "rendering/NoiseTexture.h"

struct InternGameClient
{
    ~InternGameClient()
    {
        if(window != nullptr)
        {
            glfwDestroyWindow(window);
        }
        if(glfwInitDone)
        {
            glfwTerminate();
        }
    }
    
    bool glfwInitDone = false;
    GLFWwindow* window = nullptr;
};

static const u64 NANOS_PER_TICK = 50000000;
static const float lagFactor = 1.0f / NANOS_PER_TICK;
static u64 timeFactor = 1;
static int width = 0;
static int height = 0;
static bool resize = false;
static float fovY = 60.0f;
static float nearClip = 0.1f;
static float farClip = 1000.0f;
static InternGameClient client;
static Keys keys;
static MouseButtons mButtons;
static bool useSSAO = false;

struct Shaders
{
    Shaders() : 
        world("resources/shader/worldVertex.vs", "resources/shader/worldFragment.fs"),
        ssao("resources/shader/ssaoVertex.vs", "resources/shader/ssaoFragment.fs"),
        ssaoBlur("resources/shader/ssaoBlurVertex.vs", "resources/shader/ssaoBlurFragment.fs"),
        shadow("resources/shader/worldShadowVertex.vs", "resources/shader/worldShadowFragment.fs"),
        postWorld("resources/shader/worldPostVertex.vs", "resources/shader/worldPostFragment.fs"),
        text("resources/shader/textVertex.vs", "resources/shader/textFragment.fs")
    {
    }
    
    Shader world;
    Shader ssao;
    Shader ssaoBlur;
    Shader shadow;
    Shader postWorld;
    Shader text;
    bool once = true;
    
    float worldProj[16] = 
    {
        1.0f, 0.0f, 0.0f, 0.0f,
        0.0f, 1.0f, 0.0f, 0.0f,
        0.0f, 0.0f, 1.0f, -1.0f,
        0.0f, 0.0f, 1.0, 0.0f
    };
    
    float worldView[16]= 
    {
        1.0f, 0.0f, 0.0f, 0.0f,
        0.0f, 1.0f, 0.0f, 0.0f,
        0.0f, 0.0f, 1.0f, 0.0f,
        0.0f, 0.0f, 0.0f, 1.0f
    };
    
    float worldShadowProj[16] = 
    {
        1.0f, 0.0f, 0.0f, 0.0f,
        0.0f, 1.0f, 0.0f, 0.0f,
        0.0f, 0.0f, 1.0f, -1.0f,
        0.0f, 0.0f, 1.0, 0.0f
    };
    
    float worldShadowView[16]= 
    {
        1.0f, 0.0f, 0.0f, 0.0f,
        0.0f, 1.0f, 0.0f, 0.0f,
        0.0f, 0.0f, 1.0f, 0.0f,
        0.0f, 0.0f, 0.0f, 1.0f
    };
    
    bool isValid() const
    {
        return world.isValid() && ssao.isValid() && ssaoBlur.isValid() && 
                shadow.isValid() && postWorld.isValid() && text.isValid();
    }
    
    void updateWorldProjection()
    {
        float tan = tanf((0.5f * fovY) * M_PI / 180.0f);
        float q = 1.0f / tan;
        float aspect = (float) width / height;
        worldProj[0] = q / aspect;
        worldProj[5] = q;
        worldProj[10] = (nearClip + farClip) / (nearClip - farClip);
        worldProj[14] = (2.0f * nearClip * farClip) / (nearClip - farClip);
        
        if(once)
        {
            worldShadowProj[0] = q / aspect;
            worldShadowProj[5] = q;
            worldShadowProj[10] = (nearClip + farClip) / (nearClip - farClip);
            worldShadowProj[14] = (2.0f * nearClip * farClip) / (nearClip - farClip);
        }
    }

    void updateWorldView(float lag, Camera& cam)
    {
        cam.update(lag);
        const Vector right = cam.getRight();
        const Vector up = cam.getUp();
        const Vector back = cam.getBack();
        const Vector pos = cam.getPosition();
        worldView[0] = right.getX();
        worldView[1] = up.getX();
        worldView[2] = back.getX();
        worldView[4] = right.getY();
        worldView[5] = up.getY();
        worldView[6] = back.getY();
        worldView[8] = right.getZ();
        worldView[9] = up.getZ();
        worldView[10] = back.getZ();
        worldView[12] = right.dotInverse(pos);
        worldView[13] = up.dotInverse(pos);
        worldView[14] = back.dotInverse(pos);
        
        if(once)
        {
            once = false;
            worldShadowView[0] = right.getX();
            worldShadowView[1] = up.getX();
            worldShadowView[2] = back.getX();
            worldShadowView[4] = right.getY();
            worldShadowView[5] = up.getY();
            worldShadowView[6] = back.getY();
            worldShadowView[8] = right.getZ();
            worldShadowView[9] = up.getZ();
            worldShadowView[10] = back.getZ();
            worldShadowView[12] = right.dotInverse(pos);
            worldShadowView[13] = up.dotInverse(pos);
            worldShadowView[14] = back.dotInverse(pos);
        }
    }
};

struct Framebuffers
{
    Framebuffers(u32 w, u32 h) : world(w, h, Framebuffer::POSITION | 
        Framebuffer::NORMAL | Framebuffer::COLOR | Framebuffer::RED | Framebuffer::DEPTH24_STENCIL8),
        ssao(w, h, Framebuffer::RED), ssaoBlur(w, h, Framebuffer::RED),
        shadow(w, h, Framebuffer::DEPTH24_STENCIL8)
    {
    }
    
    void resize(u32 w, u32 h) const
    {
        world.resize(w, h);
        ssao.resize(w, h);
        ssaoBlur.resize(w, h);
        shadow.resize(w, h);
    }
    
    bool isValid() const
    {
        return world.isValid() && ssao.isValid() && ssaoBlur.isValid();
    }
    
    Framebuffer world;
    Framebuffer ssao;
    Framebuffer ssaoBlur;
    Framebuffer shadow;
};

struct InternGame
{
    InternGame() : ssaoNoise(4, 4)
    {
        rectangle.add({-1, -1, 0, 0, 0, 0, 0, 0});
        rectangle.add({ 1,  1, 0, 1, 1, 0, 0, 0});
        rectangle.add({-1,  1, 0, 0, 1, 0, 0, 0});
        rectangle.add({-1, -1, 0, 0, 0, 0, 0, 0});
        rectangle.add({ 1, -1, 0, 1, 0, 0, 0, 0});
        rectangle.add({ 1,  1, 0, 1, 1, 0, 0, 0});
        rectangle.build();
    }
    
    Game game;
    Camera cam;
    MatrixStack model;
    FontRenderer fontRenderer;
    NoiseTexture ssaoNoise;
    Mesh rectangle;
};

static u64 getTimeNanos()
{
    return glfwGetTimerValue() * timeFactor;
}

static bool initGLFW()
{
    client.glfwInitDone = glfwInit();
    if(!client.glfwInitDone)
    {
        std::cout << "could not initialize GLFW\n";
        return true;
    }
    timeFactor = 1000000000 / glfwGetTimerFrequency();
    return false;
}

static bool initWindow(int w, int h, const char* windowName)
{
    width = w;
    height = h;
    
    glfwDefaultWindowHints();
    glfwWindowHint(GLFW_VISIBLE, 0);
    glfwWindowHint(GLFW_RESIZABLE, 1);
    
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    
    client.window = glfwCreateWindow(width, height, windowName, nullptr, nullptr);
    if(client.window == nullptr)
    {
        std::cout << "could not create window\n";
        return true;
    }
    glfwMakeContextCurrent(client.window);
    glfwSwapInterval(1);
    return false;
}

static bool initGLEW()
{
    GLenum err = glewInit();
    if(err != GLEW_OK)
    {
        std::cout << "could not initialize GLEW: " << glewGetErrorString(err) << "\n";
        return true;
    }
    std::cout << "using GLEW " << glewGetString(GLEW_VERSION) << "\n";
    return false;
}

static void initCallbacks()
{
    // GLFWwindow* w, int key, int scancode, int action, int mod
    glfwSetKeyCallback(client.window, [](GLFWwindow*, int key, int, int action, int)
    {
        if(action == GLFW_PRESS)
        {
            keys.press(key);
        }
        else if(action == GLFW_RELEASE)
        {
            keys.release(key);
        }
    });
    // GLFWwindow* w, int button, int action, int mods
    glfwSetMouseButtonCallback(client.window, [](GLFWwindow*, int button, int action, int)
    {
        if(action == GLFW_PRESS)
        {
            mButtons.press(button);
        }
        else if(action == GLFW_RELEASE)
        {
            mButtons.release(button);
        }
    });
    // GLFWwindow* w, double xpos, double ypos
    glfwSetCursorPosCallback(client.window, [](GLFWwindow*, double x, double y)
    {
        mButtons.move(x, y);
    });
    // GLFWwindow* w, int width, int height
    glfwSetFramebufferSizeCallback(client.window, [](GLFWwindow*, int w, int h)
    {
        glViewport(0, 0, w, h);
        width = w;
        height = h;
        resize = true;
    });
}

static void tick(InternGame& game)
{
    keys.tick();
    mButtons.tick();
    game.game.tick(keys, mButtons, game.cam);
    if(keys.test.getDownTime() == 1)
    {
        useSSAO = !useSSAO;
    }
    mButtons.postTick();
}

static void renderShadow(float lag, Shaders& shaders, InternGame& game, Framebuffers& fb)
{
    fb.shadow.bind();
    glEnable(GL_DEPTH_TEST);
    shaders.shadow.use();
    shaders.shadow.setMatrix("proj", shaders.worldShadowProj);
    shaders.shadow.setMatrix("view", shaders.worldShadowView);
    glEnable(GL_POLYGON_OFFSET_FILL);
    glPolygonOffset(2.0f, 4.0f);
    game.game.renderWorld(lag, game.model, shaders.shadow);
    glDisable(GL_POLYGON_OFFSET_FILL);
}

static void renderWorld(float lag, Shaders& shaders, InternGame& game, Framebuffers& fb)
{
    fb.world.bind();
    glEnable(GL_DEPTH_TEST);
    shaders.world.use();
    shaders.world.setMatrix("projShadow", shaders.worldShadowProj);
    shaders.world.setMatrix("viewShadow", shaders.worldShadowView);
    shaders.world.setMatrix("proj", shaders.worldProj);
    shaders.world.setMatrix("view", shaders.worldView);
    game.model.clear();
    shaders.world.setMatrix("model", game.model.get().getValues());
    fb.shadow.bindDepthTexture(1);
    game.game.renderWorld(lag, game.model, shaders.world);
}

static void renderSSAO(Shaders& shaders, InternGame& game, Framebuffers& fb)
{
    // ssao
    shaders.ssao.use();
    shaders.ssao.setMatrix("view", shaders.worldView);
    shaders.ssao.setMatrix("proj", shaders.worldProj);
    shaders.ssao.setInt("width", width);
    shaders.ssao.setInt("height", height);
    fb.world.bindPositionTexture(0);
    fb.world.bindNormalTexture(1);
    fb.world.bindColorTexture(2);
    fb.world.bindDepthTexture(3);
    game.ssaoNoise.bind(4);
    fb.ssao.bind();
    game.rectangle.draw();
    // ssao blur
    shaders.ssaoBlur.use();
    fb.ssao.bindRedTexture(0);
    fb.ssaoBlur.bind();
    game.rectangle.draw();
}

static void renderPostWorld(Shaders& shaders, InternGame& game, Framebuffers& fb)
{
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
    shaders.postWorld.use();
    fb.world.bindColorTexture(0);
    fb.ssaoBlur.bindRedTexture(1);
    fb.world.bindRedTexture(2);
    shaders.postWorld.setInt("useSSAO", useSSAO);
    game.rectangle.draw();
}

static void renderTextOverlay(float lag, Shaders& shaders, InternGame& game)
{
    glDisable(GL_DEPTH_TEST);
    shaders.text.use();
    
    Matrix m;
    shaders.text.setMatrix("proj", m.getValues());
    m.translate(-1.0f, 1.0f, 0.0f);
    m.scale(2.0f / width, -2.0f / height, 1.0f);
    shaders.text.setMatrix("view", m.getValues());
    game.model.clear();
    game.model.get().scale(2.0f, 2.0f, 2.0f);
    shaders.text.setMatrix("model", game.model.get().getValues());
    
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glBlendEquation(GL_FUNC_ADD);
    game.game.renderTextOverlay(lag, game.model, shaders.text, game.fontRenderer);
    glDisable(GL_BLEND);
}

static void renderTick(float lag, Shaders& shaders, InternGame& game, Framebuffers& fb)
{
    if(resize)
    {
        fb.resize(width, height);
        resize = false;
    }
    shaders.updateWorldProjection();
    shaders.updateWorldView(lag, game.cam);
    
    renderShadow(lag, shaders, game, fb);
    renderWorld(lag, shaders, game, fb);
    if(useSSAO)
    {
        renderSSAO(shaders, game, fb);
    }
    renderPostWorld(shaders, game, fb);
    renderTextOverlay(lag, shaders, game);
}

static void loop()
{
    Shaders shaders;
    if(!shaders.isValid())
    {
        return;
    }
    Framebuffers fb(width, height);
    if(!fb.isValid())
    {
        return;
    }
    InternGame game;
    
    u64 lastTime = getTimeNanos();
    u64 lag = 0;
    while(!glfwWindowShouldClose(client.window))
    {
        renderTick(lag * lagFactor, shaders, game, fb);
        glfwSwapBuffers(client.window);
        
        u64 newTime = getTimeNanos();
        lag += newTime - lastTime;
        lastTime = newTime;
        
        while(lag >= NANOS_PER_TICK)
        {
            lag -= NANOS_PER_TICK;
            tick(game);
        }
        glfwPollEvents();
    }
}

void GameClient::start(int w, int h, const char* windowName)
{
    if(initGLFW() || initWindow(w, h, windowName) || initGLEW())
    {
        return;
    }
    initCallbacks();
    glfwShowWindow(client.window);
    loop();
}