#include "render/skybox.h"
#include "render/shader.h"

#include <string.h>

static const float CUBE_VERTICES[] = {
    -1,  1, -1,  -1, -1, -1,   1, -1, -1,   1, -1, -1,   1,  1, -1,  -1,  1, -1,
    -1, -1,  1,  -1, -1, -1,  -1,  1, -1,  -1,  1, -1,  -1,  1,  1,  -1, -1,  1,
     1, -1, -1,   1, -1,  1,   1,  1,  1,   1,  1,  1,   1,  1, -1,   1, -1, -1,
    -1, -1,  1,  -1,  1,  1,   1,  1,  1,   1,  1,  1,   1, -1,  1,  -1, -1,  1,
    -1,  1, -1,   1,  1, -1,   1,  1,  1,   1,  1,  1,  -1,  1,  1,  -1,  1, -1,
    -1, -1, -1,  -1, -1,  1,   1, -1, -1,   1, -1, -1,  -1, -1,  1,   1, -1,  1,
};

bool Skybox_init(Skybox *sky) {
    memset(sky, 0, sizeof(*sky));

    sky->program = Shader_load("shaders/skybox.vert", "shaders/skybox.frag");
    if (!sky->program) return false;
    sky->u_view        = glGetUniformLocation(sky->program, "view");
    sky->u_projection  = glGetUniformLocation(sky->program, "projection");
    sky->u_sky_time    = glGetUniformLocation(sky->program, "skyTime");
    sky->u_sun_dir     = glGetUniformLocation(sky->program, "sunDirection");
    sky->u_light_color = glGetUniformLocation(sky->program, "lightColor");
    sky->u_sky_top     = glGetUniformLocation(sky->program, "skyTop");
    sky->u_sky_horizon = glGetUniformLocation(sky->program, "skyHorizon");
    sky->u_day_factor  = glGetUniformLocation(sky->program, "dayFactor");
    sky->u_overcast    = glGetUniformLocation(sky->program, "overcast");

    glGenVertexArrays(1, &sky->vao);
    glGenBuffers(1, &sky->vbo);
    glBindVertexArray(sky->vao);
    glBindBuffer(GL_ARRAY_BUFFER, sky->vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(CUBE_VERTICES), CUBE_VERTICES, GL_STATIC_DRAW);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), NULL);
    glEnableVertexAttribArray(0);
    glBindVertexArray(0);
    return true;
}

static void setVec3(GLint loc, Vec3 v) { glUniform3f(loc, v.x, v.y, v.z); }

void Skybox_draw(const Skybox *sky, const Renderer *renderer, const Camera *camera,
                 const Lighting *light) {
    Mat4 view = camera->view;
    view.m[12] = view.m[13] = view.m[14] = 0.0f; /* sky follows the camera */

    glDisable(GL_CULL_FACE); /* seen from inside */
    glDepthFunc(GL_LEQUAL);
    glUseProgram(sky->program);
    glUniformMatrix4fv(sky->u_view, 1, GL_FALSE, view.m);
    glUniformMatrix4fv(sky->u_projection, 1, GL_FALSE, camera->projection.m);
    glUniform1f(sky->u_sky_time, renderer->time);
    glUniform1f(sky->u_day_factor, light->day_factor);
    glUniform1f(sky->u_overcast, light->overcast);
    setVec3(sky->u_sun_dir, light->sun_direction);
    setVec3(sky->u_light_color, light->light_color);
    setVec3(sky->u_sky_top, light->sky_top);
    setVec3(sky->u_sky_horizon, light->sky_horizon);

    glBindVertexArray(sky->vao);
    glDrawArrays(GL_TRIANGLES, 0, 36);
    glBindVertexArray(0);
    glDepthFunc(GL_LESS);
}

void Skybox_shutdown(Skybox *sky) {
    if (sky->vbo) glDeleteBuffers(1, &sky->vbo);
    if (sky->vao) glDeleteVertexArrays(1, &sky->vao);
    Shader_destroy(&sky->program);
    memset(sky, 0, sizeof(*sky));
}