#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <cglm/cglm.h>
#include "include/rendlib.h"
#include "include/camera.h"
#include "include/object.h"

// global variables 
int window_width = 960;
int window_height = 540;
char *window_title = "rendlib window";

struct camera *ac;

void (*keyboard_probe)(int key, int scancode, int action, int mods);
void (*mouse_probe)(double x, double y);
void (*update_probe)(void);

float top_movement_speed = 0.4f;
vec3 speed = { 0.0f, 0.0f, 0.0f };
GLint screen_viewport[4];

struct object *objects;

unsigned int shader_program;
unsigned int vertex_shader;
unsigned int fragment_shader;

const char *object_vertex_shader_location = "assets/shaders/shader.vert";
const char *object_fragment_shader_location = "assets/shaders/shader.frag";

void update_screen_viewport(int x, int y, int width, int height) {
    GLFWwindow *w = glfwGetCurrentContext();
    glfwSetCursorPos(w, (width/2), (height/2));
    glViewport(x, y, width, height);
    glGetIntegerv(GL_VIEWPORT, screen_viewport);
}

int load_shader(const char *path, unsigned int shader) {
    FILE *fp = fopen(path, "r");
    if (fp == NULL) {
        fprintf(stderr, "error: cannot open file '%s'\n", path);
        return -1;
    }

    fseek(fp, 0L, SEEK_END);
    int len = ftell(fp);
    if (len == -1) {
        fprintf(stderr, "error: cannot fetch length of file '%s'\n", path);
        return -1;
    }

    fseek(fp, 0L, SEEK_SET);
    char *fc = (char *) malloc(len);
    if (fc == NULL) {
        fprintf(stderr, "error: not enough dynamic memory\n");
        return -1;
    }
    memset(fc, 0, len);
    int rb = 0;
    do {
        rb += fread(fc+rb, sizeof(char), len-rb, fp);
        if (rb == 0) {
            break;
        }
    } while (rb < len);

    fclose(fp);
    glShaderSource(shader, 1, (const char **) &fc, &rb);
    glCompileShader(shader);

    int success;
    glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
    if (success != GL_TRUE) {
        int log_length;
        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &log_length);

        char log[log_length];
        glGetShaderInfoLog(shader, log_length, NULL, log);

        fprintf(stderr, "Shader Compilation Error: %s\n", log);
        return -1;
    }

    free(fc);
    return 0;
}

int load_shaders(void) {
    glDeleteProgram(shader_program);
    shader_program = glCreateProgram();

    vertex_shader = glCreateShader(GL_VERTEX_SHADER);
    fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);

    if (load_shader(object_vertex_shader_location, vertex_shader) == -1) {
        return -1;
    }

    if (load_shader(object_fragment_shader_location, fragment_shader) == -1) {
        return -1;
    }

    glAttachShader(shader_program, vertex_shader);
    glAttachShader(shader_program, fragment_shader);
    glLinkProgram(shader_program);

    int success;
    glGetProgramiv(shader_program, GL_LINK_STATUS, &success);

    if (success != GL_TRUE) {
        int log_length;
        glGetProgramiv(shader_program, GL_INFO_LOG_LENGTH, &log_length);

        char log[log_length];
        glGetProgramInfoLog(shader_program, log_length, NULL, log);

        fprintf(stderr, "[object program] Shader Compilation Error: %s\n", log);
        return -1;
    }

    glDeleteShader(vertex_shader);
    glDeleteShader(fragment_shader);

    return 0;
}

void handle_input(void) {
}

void window_size(GLFWwindow *w, int width, int height) {
    update_screen_viewport(0, 0, width, height);
}

void display(void) {
    handle_input();
    GLFWwindow *w = glfwGetCurrentContext();

    GLint translation_uniform;
    GLint view_uniform;
    GLint projection_uniform;
    GLint color_uniform;
    GLint scale_uniform;

    glClearColor(0.13f, 0.13f, 0.13f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glUseProgram(shader_program);

    int ret = bake_camera(ac);
    if (ret < 0) {
        fprintf(stderr, "--error: failed baking camera\n");
        return;
    }

    view_uniform = glGetUniformLocation(shader_program, "view");
    projection_uniform = glGetUniformLocation(shader_program, "projection");
    translation_uniform = glGetUniformLocation(shader_program, "translation");
    color_uniform = glGetUniformLocation(shader_program, "color");
    scale_uniform = glGetUniformLocation(shader_program, "scale");

    glUniformMatrix4fv(view_uniform, 1, GL_FALSE, (float *) ac->view);
    glUniformMatrix4fv(projection_uniform, 1, GL_FALSE, (float *) ac->projection);

    for (struct object *obj = objects; obj != NULL; obj = obj->next) {
        mat4 translation_matrix;
        glm_mat4_identity(translation_matrix);

        struct model *obj_model = obj->model;
        glm_translate(translation_matrix, obj->position);

        glUniformMatrix4fv(translation_uniform, 1, GL_FALSE, (float *) translation_matrix);

        glUniform3fv(color_uniform, 1, (float *) obj->color);
        glUniform1f(scale_uniform, obj->scale);

        glBindVertexArray(obj->vao);
        glDrawElements(GL_TRIANGLES, obj_model->indices_num, GL_UNSIGNED_INT, (void *) 0);
    }

    glfwSwapBuffers(w);
    glfwPollEvents();
}

void rendlib_bake_graphics(void) {
    glGetIntegerv(GL_VIEWPORT, screen_viewport);

    for (struct object *obj = objects; obj != NULL; obj = obj->next) {
        struct model *obj_model = obj->model;
        glGenVertexArrays(1, &obj->vao);
        glGenBuffers(1, &obj->vbo);
        glGenBuffers(1, &obj->ebo);
        glGenBuffers(1, &obj->nbo);

        glBindVertexArray(obj->vao);

        glBindBuffer(GL_ARRAY_BUFFER,obj->vbo);
        glBufferData(GL_ARRAY_BUFFER,obj_model->vertices_num*3*sizeof(float),obj_model->vertices, GL_STATIC_DRAW);

        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3*sizeof(float), (void *) 0);
        glEnableVertexAttribArray(0);

        glBindBuffer(GL_ARRAY_BUFFER, obj->nbo);
        glBufferData(GL_ARRAY_BUFFER, obj_model->normals_num*3*sizeof(float), obj_model->normals, GL_STATIC_DRAW);

        glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3*sizeof(float), (void *) 0);
        glEnableVertexAttribArray(1);

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,obj->ebo);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, obj_model->indices_num*sizeof(unsigned int), obj_model->indices, GL_STATIC_DRAW);

        glBindVertexArray(0);
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    }

    glEnable(GL_DEPTH_TEST);
}
void keyboard(GLFWwindow *w, int key, int scancode, int action, int mods) {
    if (keyboard_probe == NULL) {
        return; 
    }

    (keyboard_probe)(key, scancode, action, mods);
}

void mouse_motion(GLFWwindow *window, double x, double y) {
    if (mouse_probe == NULL) {
        return;
    }

    (mouse_probe)(x, y);
}

int rendlib_start_window(int argc, char *argv[]) {
    int ret = glfwInit();
    if (!ret) {
        return err_glfw_init;
    }

    GLFWwindow *w = glfwCreateWindow(window_width, window_height, window_title, NULL, NULL);
    if (w == NULL) {
        return err_glfw_win;
    }

    glfwMakeContextCurrent(w);
    glfwSetWindowSizeCallback(w, window_size);
    glfwSetCursorPosCallback(w, mouse_motion);
    glfwSetKeyCallback(w, keyboard);
    glfwSetInputMode(w, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

    ret = glewInit();
    if (ret != GLEW_OK) {
        return err_glew_init;
    }

    ret = load_shaders();
    if (ret < 0) {
        return err_shaders_init;
    }

    return 0;
}

int setup_default_camera(void) {
    ac = create_camera(CAMERA_PERSPECTIVE);
    if (ac == NULL) {
        return -1;
    }
    return 0;
}

int rendlib_render(void) {
    if (ac == NULL) {
        if (setup_default_camera() < 0) {
            return -1;
        }
    }
    rendlib_bake_graphics();
    for (;;) {
        if (update_probe != NULL) {
            (update_probe)();
        }

        display();
    }
    return 0;
}