#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/math.h"
#include "include/object.h"

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

float fov = 90.0f;
float camera_yaw = -90.0f;
float camera_pitch = 0.0f;
float camera_sensitivity = 0.02f;
float top_movement_speed = 0.2f;
vec3 camera_pos = { 0.0f, 0.0f, 50.0f };
vec3 camera_front = { 0.0f, 0.0f, -1.0f };
vec3 camera_up = { 0.0f, 1.0f, 0.0f }; 
vec3 speed = { 0.0f, 0.0f, 0.0f };
struct object *camera_lock = NULL;
GLint screen_viewport[4];

// tmp input 
char input = 0;

// tmp 
struct model *sphere_model;
struct object *objects;

// opengl
unsigned int shader_program;
unsigned int vertex_shader;
unsigned int fragment_shader;

// shaders
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();

    // create and load new shaders
    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;
    }

    // compile object shader program
    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) {
    int ret = 0; 
    if (input & RENDLIB_INPUT_ESC) {
        exit(EXIT_SUCCESS);
        input &= ~RENDLIB_INPUT_ESC;
    }
    
    if (input & RENDLIB_INPUT_REL) {
        ret = load_shaders();
        if (ret < 0) {
            fprintf(stderr, "--error: reloading shaders\n");
            exit(EXIT_FAILURE);
        }
        input &= ~RENDLIB_INPUT_REL;
    }

    if (input & RENDLIB_INPUT_LEFT) {
        vec3 side_scalar = {top_movement_speed, top_movement_speed, top_movement_speed };
        vec3 camera_side;
        glm_cross(camera_front, camera_up, camera_side);
        glm_normalize(camera_side);
        glm_vec3_mul(camera_side, side_scalar, camera_side);
        glm_vec3_sub(camera_pos, camera_side, camera_pos);
    }

    if (input & RENDLIB_INPUT_RIGHT) {
        vec3 side_scalar = {top_movement_speed, top_movement_speed, top_movement_speed };
        vec3 camera_side;
        glm_cross(camera_front, camera_up, camera_side);
        glm_normalize(camera_side);
        glm_vec3_mul(camera_side, side_scalar, camera_side);
        glm_vec3_add(camera_pos, camera_side, camera_pos);
    }

    if (input & RENDLIB_INPUT_BACKW) {
        vec3 front_scalar = {top_movement_speed, top_movement_speed, top_movement_speed };
        glm_vec3_mul(front_scalar, camera_front, front_scalar);
        glm_vec3_sub(camera_pos, front_scalar, camera_pos);
    }

    if (input & RENDLIB_INPUT_FORW) {
        vec3 front_scalar = {top_movement_speed, top_movement_speed, top_movement_speed };
        glm_vec3_mul(front_scalar, camera_front, front_scalar);
        glm_vec3_add(camera_pos, front_scalar, camera_pos);
    }
}

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

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

    mat4 view;
    mat4 projection;

    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);

    glm_mat4_identity(view);
    vec3 camera_center;
    glm_vec3_add(camera_pos, camera_front, camera_center);
    glm_lookat(camera_pos, camera_center, camera_up, view);

    glm_mat4_identity(projection);
    glm_perspective(glm_rad(fov), (float) screen_viewport[2]/(float) screen_viewport[3], 0.01f, 100000.0f, projection);

    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 *) view);
    glUniformMatrix4fv(projection_uniform, 1, GL_FALSE, (float *) 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;

        // calculate gravity
        for (struct object *target = objects; target != NULL; target = target->next) {
            if (target == obj) {
                continue;
            }

            vec3 force;
            glm_vec3_zero(force);
            calculate_gravity(obj, target, force);

            vec4 force_new;
            for (int i = 0; i < 3; i++) {
                force_new[i] = force[i];
            }
            force_new[3] = 0.0f;

            float n = obj->mass;
            vec4 scaler = {n,n,n,1.0f};
            glm_vec4_div(force_new, scaler, force_new);

            glm_vec4_add(force_new, obj->translation_force, obj->translation_force);
        }

        glm_vec4_add(obj->position, obj->translation_force, obj->position);

        // follow object if camera locked 
        if (camera_lock == obj) {
            glm_vec3_add(camera_pos, obj->translation_force, camera_pos);
        }

        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);

        glBindVertexArray(obj->pvao);

        glBindBuffer(GL_ARRAY_BUFFER, obj->pbo);
        glBufferData(GL_ARRAY_BUFFER, obj->paths_num*3*sizeof(float),obj->paths, GL_STATIC_DRAW);

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

        glm_mat4_identity(translation_matrix);
        glUniformMatrix4fv(translation_uniform, 1, GL_FALSE, (float *) translation_matrix);
        glUniform1f(scale_uniform, 1.0f);

        glDrawArrays(GL_LINE_STRIP, 0, obj->paths_num);
    }

    /*glutPostRedisplay();
    glutSwapBuffers();*/
    glfwSwapBuffers(w);
    glfwPollEvents();
}

void rendlib_bake_graphics(void) {
    // setup default mouse position
    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);
        glGenVertexArrays(1, &obj->pvao);
        glGenBuffers(1, &obj->vbo);
        glGenBuffers(1, &obj->ebo);
        glGenBuffers(1, &obj->nbo);
        glGenBuffers(1, &obj->pbo);

        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 (action == GLFW_PRESS) {
        switch (key) {
            case GLFW_KEY_Q: 
            case GLFW_KEY_ESCAPE: 
                input |= RENDLIB_INPUT_ESC; 
                break;
            case GLFW_KEY_R: 
                input |= RENDLIB_INPUT_REL;
                break;
            case GLFW_KEY_A:
            case GLFW_KEY_LEFT:
                input |= RENDLIB_INPUT_LEFT;
                break;
            case GLFW_KEY_D:
            case GLFW_KEY_RIGHT:
                input |= RENDLIB_INPUT_RIGHT;
                break;
            case GLFW_KEY_S:
            case GLFW_KEY_DOWN:
                input |= RENDLIB_INPUT_BACKW;
                break;
            case GLFW_KEY_W:
            case GLFW_KEY_UP:
                input |= RENDLIB_INPUT_FORW;
                break;
            case GLFW_KEY_F11: {
                GLFWmonitor *m = glfwGetPrimaryMonitor();
                const GLFWvidmode *vm = glfwGetVideoMode(m);
                GLFWwindow *w = glfwGetCurrentContext();
                glfwSetWindowMonitor(w, m, 0, 0, vm->width, vm->height, vm->refreshRate);

                update_screen_viewport(0, 0, vm->width, vm->height);
                break;
            }
        }

    } else if (action == GLFW_RELEASE) {
        switch (key) {
            case GLFW_KEY_A:
            case GLFW_KEY_LEFT:
                input &= ~RENDLIB_INPUT_LEFT;
                break;
            case GLFW_KEY_D:
            case GLFW_KEY_RIGHT:
                input &= ~RENDLIB_INPUT_RIGHT;
                break;
            case GLFW_KEY_S:
            case GLFW_KEY_DOWN:
                input &= ~RENDLIB_INPUT_BACKW;
                break;
            case GLFW_KEY_W:
            case GLFW_KEY_UP:
                input &= ~RENDLIB_INPUT_FORW;
                break;
        }
    }
}

int warped_pointer = 0;
int first_pointer = 1;
void mouse_motion(GLFWwindow *window, double x, double y) {
    if (warped_pointer == 1) {
        warped_pointer = 0;
        return;
    }

    warped_pointer = 1;
    glGetIntegerv(GL_VIEWPORT, screen_viewport);
    GLFWwindow *w = glfwGetCurrentContext();
    glfwSetCursorPos(w, (screen_viewport[2]/2), (screen_viewport[3]/2));

    if (first_pointer == 1) {
        first_pointer = 0;
        return;
    }

    float offset_x = (float) (x - (screen_viewport[2]/2)) * camera_sensitivity;
    float offset_y = (float) (y - (screen_viewport[3]/2)) * camera_sensitivity;

    camera_yaw += offset_x;
    camera_pitch -= offset_y;

    // limit view rotation
    if (camera_pitch < -89.9f) {
        camera_pitch = -89.9f;
    }
    if (camera_pitch > 89.9f) {
        camera_pitch = 89.9f;
    }

    vec3 view_direction = { cos(glm_rad(camera_yaw)) * cos(glm_rad(camera_pitch)),
	sin(glm_rad(camera_pitch)),
	sin(glm_rad(camera_yaw)) * cos(glm_rad(camera_pitch))
    };
    glm_normalize_to(view_direction, camera_front);
}

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 rendlib_render(void) {
    rendlib_bake_graphics();
    for (;;) {
        display();
    }
    return 0;
}