#include <array>
#include <span>

#include "glad/glad.h"
#include "glm/gtc/matrix_transform.hpp"

#include "scenes/cube.hpp"

namespace cbt::scenes {

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

auto cube::init() -> bool {
    if (!build_pipeline()) {
        return false;
    }
    return true;
}

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

auto cube::render(int width, int height) -> void {
    glViewport(0, 0, width, height);

    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 = float(width) / float(height);
    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_pipeline.draw(model, view, proj);
}

auto cube::build_pipeline() -> 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";

    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,
    };

    gfx::pipeline_desc desc{
        .vertex_data = std::as_bytes(std::span{vertices}),
        .attributes = {
            {.location = 0, .num_components = 3, .offset = 0},
            {.location = 1, .num_components = 3, .offset = 12},
        },
        .vertex_stride = 24,
        .vertex_shader_src = vert_src,
        .fragment_shader_src = frag_src,
        .depth_test = true,
        .primitive = gfx::primitive_type::triangles
        // no index data
    };

    m_pipeline = gfx::pipeline{desc};
    return m_pipeline.valid();
}

}