#define GLFW_INCLUDE_NONE
#include "GLFW/glfw3.h"

#include "cbt/opengl/context.hpp"
#include "cbt/opengl/shader.hpp"
#include "cbt/opengl/buffer.hpp"
#include "cbt/opengl/vao.hpp"

#include <chrono>

#include <asio.hpp>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include "glad/glad.h"

auto main(int, char const*[]) -> int {
    auto ctx = cbt::opengl::context("cuber", 1280, 720);

    if (!ctx.valid()) {
        return 1;
    }

    // compile shader
    auto prog = cbt::opengl::shader();

    char const* vert_src = R"glsl(
        #version 410 core
        layout(location = 0) in vec3 a_pos;
        layout(location = 1) in vec3 a_color;
        uniform mat4 u_model;
        uniform mat4 u_view;
        uniform mat4 u_proj;
        out vec3 v_color;
        void main() {
            gl_Position = u_proj * u_view * u_model * vec4(a_pos, 1.0);
            v_color = a_color;
        }
    )glsl";

    char const* frag_src = R"glsl(
        #version 410 core
        in vec3 v_color;
        out vec4 frag_color;
        void main() {
            frag_color = vec4(v_color, 1.0);
        }
    )glsl";

    if (!prog.compile_vertex(vert_src) || !prog.compile_fragment(frag_src) || !prog.link()) {
        return 1;
    }

    // cube vertices: 6 faces, 2 triangles per face, 3 verts each = 36 vertices
    // each vertex: x, y, z, r, g, b
    std::array<float, 36 * 6> vertices = {
        // front face (cyan)
         0.5f, -0.5f,  0.5f,  0.0f, 1.0f, 1.0f,
        -0.5f, -0.5f,  0.5f,  0.0f, 1.0f, 1.0f,
        -0.5f,  0.5f,  0.5f,  0.0f, 1.0f, 1.0f,
         0.5f, -0.5f,  0.5f,  0.0f, 1.0f, 1.0f,
        -0.5f,  0.5f,  0.5f,  0.0f, 1.0f, 1.0f,
         0.5f,  0.5f,  0.5f,  0.0f, 1.0f, 1.0f,

        // back face (magenta)
         0.5f, -0.5f, -0.5f,  1.0f, 0.0f, 1.0f,
        -0.5f, -0.5f, -0.5f,  1.0f, 0.0f, 1.0f,
        -0.5f,  0.5f, -0.5f,  1.0f, 0.0f, 1.0f,
         0.5f, -0.5f, -0.5f,  1.0f, 0.0f, 1.0f,
        -0.5f,  0.5f, -0.5f,  1.0f, 0.0f, 1.0f,
         0.5f,  0.5f, -0.5f,  1.0f, 0.0f, 1.0f,

        // top face (yellow)
         0.5f,  0.5f,  0.5f,  1.0f, 1.0f, 0.0f,
        -0.5f,  0.5f,  0.5f,  1.0f, 1.0f, 0.0f,
        -0.5f,  0.5f, -0.5f,  1.0f, 1.0f, 0.0f,
         0.5f,  0.5f,  0.5f,  1.0f, 1.0f, 0.0f,
        -0.5f,  0.5f, -0.5f,  1.0f, 1.0f, 0.0f,
         0.5f,  0.5f, -0.5f,  1.0f, 1.0f, 0.0f,

        // bottom face (white)
         0.5f, -0.5f, -0.5f,  1.0f, 1.0f, 1.0f,
        -0.5f, -0.5f, -0.5f,  1.0f, 1.0f, 1.0f,
        -0.5f, -0.5f,  0.5f,  1.0f, 1.0f, 1.0f,
         0.5f, -0.5f, -0.5f,  1.0f, 1.0f, 1.0f,
        -0.5f, -0.5f,  0.5f,  1.0f, 1.0f, 1.0f,
         0.5f, -0.5f,  0.5f,  1.0f, 1.0f, 1.0f,

        // right face (lime)
         0.5f, -0.5f, -0.5f,  0.0f, 1.0f, 0.0f,
         0.5f, -0.5f,  0.5f,  0.0f, 1.0f, 0.0f,
         0.5f,  0.5f,  0.5f,  0.0f, 1.0f, 0.0f,
         0.5f, -0.5f, -0.5f,  0.0f, 1.0f, 0.0f,
         0.5f,  0.5f,  0.5f,  0.0f, 1.0f, 0.0f,
         0.5f,  0.5f, -0.5f,  0.0f, 1.0f, 0.0f,

        // left face (orange)
        -0.5f, -0.5f, -0.5f,  1.0f, 0.5f, 0.0f,
        -0.5f, -0.5f,  0.5f,  1.0f, 0.5f, 0.0f,
        -0.5f,  0.5f,  0.5f,  1.0f, 0.5f, 0.0f,
        -0.5f, -0.5f, -0.5f,  1.0f, 0.5f, 0.0f,
        -0.5f,  0.5f,  0.5f,  1.0f, 0.5f, 0.0f,
        -0.5f,  0.5f, -0.5f,  1.0f, 0.5f, 0.0f,
    };

    auto vbo = cbt::opengl::buffer(cbt::opengl::buffer_type::vertex);
    vbo.upload(vertices.data(), vertices.size() * sizeof(float));

    // bind VAO and configure vertex attributes
    auto vao = cbt::opengl::vao();
    vao.bind();
    vbo.bind();
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), nullptr);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float),
                         reinterpret_cast<void*>(3 * sizeof(float)));
    vbo.unbind();
    vao.unbind();

    // enable depth testing
    glEnable(GL_DEPTH_TEST);

    // signal handling
    asio::io_context io;
    asio::signal_set signals(io, SIGINT, SIGTERM);
    bool quit = false;

    signals.async_wait([&](auto, auto) {
        quit = true;
        io.stop();
    });

    auto process_signals = [&]() -> void {
        while (io.poll()) {}
    };

    // render loop
    auto start = std::chrono::steady_clock::now();

    while (!ctx.should_close()) {
        process_signals();

        if (quit || glfwGetKey(ctx.raw(), GLFW_KEY_Q) == GLFW_PRESS) {
            break;
        }

        auto now = std::chrono::steady_clock::now();
        auto elapsed = std::chrono::duration<float>(now - start).count();

        glClearColor(0.15f, 0.15f, 0.2f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        // compute MVP matrices
        auto aspect = 1280.0f / 720.0f;
        auto proj = glm::perspective(glm::radians(45.0f), aspect, 0.1f, 100.0f);
        auto view = glm::translate(glm::mat4{1.0f}, glm::vec3{0.0f, 0.0f, -3.0f});
        auto model = glm::rotate(glm::mat4{1.0f}, elapsed, glm::vec3{1.0f, 0.5f, 0.3f});

        prog.use();
        glUniformMatrix4fv(glGetUniformLocation(prog.id(), "u_proj"), 1, GL_FALSE, glm::value_ptr(proj));
        glUniformMatrix4fv(glGetUniformLocation(prog.id(), "u_view"), 1, GL_FALSE, glm::value_ptr(view));
        glUniformMatrix4fv(glGetUniformLocation(prog.id(), "u_model"), 1, GL_FALSE, glm::value_ptr(model));

        vao.bind();
        glDrawArrays(GL_TRIANGLES, 0, 36);
        vao.unbind();
        prog.unuse();

        ctx.swap_buffers();
        ctx.poll_events();
    }

    return 0;
}