#include "scenes/cube.hpp"

#include <array>

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

#include "glad/glad.h"

namespace cbt::scenes {

cube::cube() {
    m_start = std::chrono::steady_clock::now();
}

auto cube::init() -> bool {
    if (!build_shader()) {
        return false;
    }
    build_mesh();
    glEnable(GL_DEPTH_TEST);
    return true;
}

auto cube::update(float) -> void {}

auto cube::render() -> void {
    auto now = std::chrono::steady_clock::now();
    auto elapsed = std::chrono::duration<float>(now - m_start).count();

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

    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});

    m_prog.use();
    glUniformMatrix4fv(m_loc_proj, 1, GL_FALSE, glm::value_ptr(proj));
    glUniformMatrix4fv(m_loc_view, 1, GL_FALSE, glm::value_ptr(view));
    glUniformMatrix4fv(m_loc_model, 1, GL_FALSE, glm::value_ptr(model));

    m_vao.bind();
    glDrawArrays(GL_TRIANGLES, 0, 36);
    m_vao.unbind();
    m_prog.unuse();
}

auto cube::build_mesh() -> void {
    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,
    };

    m_vbo.upload(vertices.data(), vertices.size() * sizeof(float));

    m_vao.bind();
    m_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)));
    m_vbo.unbind();
    m_vao.unbind();
}

auto cube::build_shader() -> bool {
    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 (!m_prog.compile_vertex(vert_src) || !m_prog.compile_fragment(frag_src) || !m_prog.link()) {
        return false;
    }

    m_loc_proj = glGetUniformLocation(m_prog.id(), "u_proj");
    m_loc_view = glGetUniformLocation(m_prog.id(), "u_view");
    m_loc_model = glGetUniformLocation(m_prog.id(), "u_model");

    return true;
}

}