#include <stdio.h>

#include <glad/glx.h>
#include <stb_image.h>

#include "shader.h"
#include "zephr.h"

Shader ui_shader;
unsigned int ui_vao;
unsigned int ui_vbo;

int init_ui(const char* font_path) {
  int res = init_fonts(font_path);
  if (res == -1) {
    printf("[ERROR]: could not initialize freetype library\n");
    return 1;
  } else if (res == -2) {
    printf("[ERROR]: could not load font file: \"%s\"\n", font_path);
    return 1;
  }

  ui_shader = create_shader("shaders/ui.vert", "shaders/ui.frag");

  glGenVertexArrays(1, &ui_vao);
  glGenBuffers(1, &ui_vbo);

  glBindVertexArray(ui_vao);
  glBindBuffer(GL_ARRAY_BUFFER, ui_vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 6 * 4, NULL, GL_DYNAMIC_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void *)0);

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

  return 0;
}

void set_parent_constraint(UIConstraints *constraints, UIConstraints *parent_constraints) {
  constraints->parent = parent_constraints;
}

void set_x_constraint(UIConstraints *constraints, float value, UIConstraint type) {
  switch (type) {
    case UI_CONSTRAINT_ASPECT_RATIO:
      // no-op. fallback to FIXED
    case UI_CONSTRAINT_FIXED:
      constraints->x = value;
      break;
    case UI_CONSTRAINT_RELATIVE:
      constraints->x = (value * zephr_ctx->window.size.width);
      break;
    case UI_CONSTRAINT_RELATIVE_PIXELS:
      constraints->x = zephr_ctx->window.size.width / (float)zephr_ctx->screen_size.width * value;
      break;
  }

  if (constraints->parent) {
    constraints->x += constraints->parent->x;
  }
}

void set_y_constraint(UIConstraints *constraints, float value, UIConstraint type) {
  switch (type) {
    case UI_CONSTRAINT_ASPECT_RATIO:
      // no-op. fallback to FIXED
    case UI_CONSTRAINT_FIXED:
      constraints->y = value;
      break;
    case UI_CONSTRAINT_RELATIVE:
      constraints->y = (value * zephr_ctx->window.size.height);
      break;
    case UI_CONSTRAINT_RELATIVE_PIXELS:
      constraints->y = zephr_ctx->window.size.height / (float)zephr_ctx->screen_size.height * value;
      break;
  }

  if (constraints->parent) {
    constraints->y += constraints->parent->y;
  }
}

void set_width_constraint(UIConstraints *constraints, float value, UIConstraint type) {
  switch (type) {
    case UI_CONSTRAINT_FIXED:
      constraints->width = value;
      break;
    case UI_CONSTRAINT_RELATIVE:
      constraints->width = (value * zephr_ctx->window.size.width);
      break;
    case UI_CONSTRAINT_RELATIVE_PIXELS:
      constraints->width = zephr_ctx->window.size.width / (float)zephr_ctx->screen_size.width * value;
      break;
    case UI_CONSTRAINT_ASPECT_RATIO:
      constraints->width = constraints->height * value;
      break;
  }
}

void set_height_constraint(UIConstraints *constraints, float value, UIConstraint type) {
  switch (type) {
    case UI_CONSTRAINT_FIXED:
      constraints->height = value;
      break;
    case UI_CONSTRAINT_RELATIVE:
      constraints->height = (value * zephr_ctx->window.size.height);
      break;
    case UI_CONSTRAINT_RELATIVE_PIXELS:
      constraints->height = zephr_ctx->window.size.height / (float)zephr_ctx->screen_size.height * value;
      break;
    case UI_CONSTRAINT_ASPECT_RATIO:
      constraints->height = constraints->width * value;
      break;
  }
}

void set_rotation_constraint(UIConstraints *constraints, float angle_d) {
  constraints->rotation = angle_d;
}

void apply_constraints(UIConstraints *constraints, Vec2f *pos, Sizef *size) {
  *pos = (Vec2f){constraints->x, constraints->y};
  *size = (Sizef){constraints->width, constraints->height};
}

void apply_constraints_rect(UIConstraints *constraints, Rect *rect) {
  rect->pos = (Vec2f){constraints->x, constraints->y};
  rect->size = (Sizef){constraints->width, constraints->height};
}

void apply_alignment(Alignment align, UIConstraints *constraints, Vec2f *pos, Sizef size) {
  // if we don't have a parent then we're a top level element and we should align against the window
  Sizef parent_size = (Sizef){zephr_ctx->window.size.width, zephr_ctx->window.size.height};
  if (constraints->parent) {
    parent_size = (Sizef){constraints->parent->width, constraints->parent->height};
  }

  switch (align) {
    case ALIGN_TOP_LEFT:
      pos->x = pos->x;
      pos->y = pos->y;
      break;
    case ALIGN_TOP_CENTER:
      pos->x += parent_size.width / 2.f - size.width / 2.f;
      pos->y = pos->y;
      break;
    case ALIGN_TOP_RIGHT:
      pos->x += parent_size.width - size.width;
      pos->y = pos->y;
      break;
    case ALIGN_BOTTOM_LEFT:
      pos->x = pos->x;
      pos->y += parent_size.height - size.height;
      break;
    case ALIGN_BOTTOM_CENTER:
      pos->x += parent_size.width / 2.f - size.width / 2.f;
      pos->y += parent_size.height - size.height;
      break;
    case ALIGN_BOTTOM_RIGHT:
      pos->x += parent_size.width - size.width;
      pos->y += parent_size.height - size.height;
      break;
    case ALIGN_LEFT_CENTER:
      pos->x = pos->x;
      pos->y += parent_size.height / 2.f - size.height / 2.f;
      break;
    case ALIGN_RIGHT_CENTER:
      pos->x += parent_size.width - size.width;
      pos->y += parent_size.height / 2.f - size.height / 2.f;
      break;
    case ALIGN_CENTER:
      pos->x += parent_size.width / 2.f - size.width / 2.f;
      pos->y += parent_size.height / 2.f - size.height / 2.f;
      break;
  }
}

bool inside_rect(Rect *rect, Vec2 *point) {
  if (point->x >= rect->pos.x && point->x <= rect->pos.x + rect->size.width &&
      point->y >= rect->pos.y && point->y <= rect->pos.y + rect->size.height) {
    return true;
  }
  return false;
}

void draw_quad(UIConstraints *constraints, const Color color, float border_radius, Alignment align) {
  use_shader(ui_shader);

  set_vec4f(ui_shader, "aColor", color.r / 255.f, color.g / 255.f, color.b / 255.f, color.a / 255.f);
  set_float(ui_shader, "uiWidth", constraints->width);
  set_float(ui_shader, "uiHeight", constraints->height);
  set_float(ui_shader, "borderRadius", border_radius);
  set_mat4f(ui_shader, "projection", (float *)zephr_ctx->projection.m);

  Vec2f pos = { 0.f, 0.f };
  Sizef size = { 0.f, 0.f };

  apply_constraints(constraints, &pos, &size);
  apply_alignment(align, constraints, &pos, size);

  // set the positions after applying alignment so children can use them
  constraints->x = pos.x;
  constraints->y = pos.y;

  Matrix4x4 model = identity();
  apply_translation(&model, (Vec2f){-size.width / 2.f, -size.height / 2.f});
  apply_rotation(&model, to_radians(constraints->rotation));
  apply_translation(&model, (Vec2f){size.width / 2.f, size.height / 2.f});

  apply_translation(&model, pos);

  set_mat4f(ui_shader, "model", (float *)model.m);

  glBindVertexArray(ui_vao);

  float vertices[6][4] = {
    // bottom left tri
    {0,              0 + size.height, 0.0, 1.0},
    {0,              0,               0.0, 0.0},
    {0 + size.width, 0,               1.0, 0.0},

    // top right tri
    {0,              0 + size.height, 0.0, 1.0},
    {0 + size.width, 0,               1.0, 0.0},
    {0 + size.width, 0 + size.height, 1.0, 1.0},
  };

  glBindBuffer(GL_ARRAY_BUFFER, ui_vbo);
  glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
  glBindBuffer(GL_ARRAY_BUFFER, 0);

  glDrawArrays(GL_TRIANGLES, 0, 6);

  glBindVertexArray(0);
}

void draw_circle(UIConstraints *constraints, const Color color, Alignment align) {
  float radius = 0.f;

  if (constraints->width > constraints->height) {
    radius = constraints->height / 2.f;
  } else {
    radius = constraints->width / 2.f;
  }
  draw_quad(constraints, color, radius, align);
}

void draw_triangle(UIConstraints *constraints, const Color color, Alignment align) {
  use_shader(ui_shader);

  set_vec4f(ui_shader, "aColor", color.r / 255.f, color.g / 255.f, color.b / 255.f, color.a / 255.f);
  set_mat4f(ui_shader, "projection", (float *)zephr_ctx->projection.m);

  Vec2f pos = { 0.f, 0.f };
  Sizef size = { 0.f, 0.f };

  apply_constraints(constraints, &pos, &size);
  apply_alignment(align, constraints, &pos, size);

  // set the positions after applying alignment so children can use them
  constraints->x = pos.x;
  constraints->y = pos.y;

  Matrix4x4 model = identity();
  apply_translation(&model, (Vec2f){-size.width / 2.f, -size.height / 2.f});
  apply_rotation(&model, to_radians(constraints->rotation));
  apply_translation(&model, (Vec2f){size.width / 2.f, size.height / 2.f});

  apply_translation(&model, pos);

  set_mat4f(ui_shader, "model", (float *)model.m);

  glBindVertexArray(ui_vao);

  float vertices[3][4] = {
    {0 + size.width,     0,               0.0, 0.0},
    {0,                  0,               0.0, 0.0},
    {0 + size.width / 2, 0 + size.height, 0.0, 0.0},
  };

  glBindBuffer(GL_ARRAY_BUFFER, ui_vbo);
  glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
  glBindBuffer(GL_ARRAY_BUFFER, 0);

  glDrawArrays(GL_TRIANGLES, 0, 3);

  glBindVertexArray(0);
}

void draw_texture(UIConstraints *constraints, const TextureId texture_id, const Color color, f32 radius, Alignment align) {
  use_shader(ui_shader);

  set_vec4f(ui_shader, "aColor", color.r / 255.f, color.g / 255.f, color.b / 255.f, color.a / 255.f);
  set_float(ui_shader, "uiWidth", constraints->width);
  set_float(ui_shader, "uiHeight", constraints->height);
  set_float(ui_shader, "borderRadius", radius);
  set_bool(ui_shader, "hasTexture", true);

  set_mat4f(ui_shader, "projection", (float *)zephr_ctx->projection.m);

  Vec2f pos = { 0.f, 0.f };
  Sizef size = { 0.f, 0.f };

  apply_constraints(constraints, &pos, &size);
  apply_alignment(align, constraints, &pos, size);

  // set the positions after applying alignment so children can use them
  constraints->x = pos.x;
  constraints->y = pos.y;

  Matrix4x4 model = identity();
  apply_translation(&model, (Vec2f){-size.width / 2.f, -size.height / 2.f});
  apply_rotation(&model, to_radians(constraints->rotation));
  apply_translation(&model, (Vec2f){size.width / 2.f, size.height / 2.f});

  apply_translation(&model, pos);

  set_mat4f(ui_shader, "model", (float *)model.m);

  glBindVertexArray(ui_vao);

  float vertices[6][4] = {
    // bottom left tri
    {0,              0 + size.height, 0.0, 1.0},
    {0,              0,               0.0, 0.0},
    {0 + size.width, 0,               1.0, 0.0},

    // top right tri
    {0,              0 + size.height, 0.0, 1.0},
    {0 + size.width, 0,               1.0, 0.0},
    {0 + size.width, 0 + size.height, 1.0, 1.0},
  };

  glBindBuffer(GL_ARRAY_BUFFER, ui_vbo);
  glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
  glBindBuffer(GL_ARRAY_BUFFER, 0);

  glActiveTexture(GL_TEXTURE0);
  glBindTexture(GL_TEXTURE_2D, texture_id);

  glDrawArrays(GL_TRIANGLES, 0, 6);

  glBindVertexArray(0);
  set_bool(ui_shader, "hasTexture", false);
}

bool draw_button(UIConstraints *constraints, const Color color, const char *text, f32 radius, Alignment align, ButtonState state) {
  Color text_color = COLOR_BLACK;
  Rect rect = {0};

  apply_constraints(constraints, &rect.pos, &rect.size);
  apply_alignment(align, constraints, &rect.pos, rect.size);

  bool is_hovered = inside_rect(&rect, &zephr_ctx->mouse.pos);
  bool left_mouse_pressed = zephr_ctx->mouse.pressed && zephr_ctx->mouse.button == ZEPHR_MOUSE_BUTTON_LEFT;

  if (is_hovered && state == BUTTON_STATE_ACTIVE) {
    zephr_set_cursor(ZEPHR_CURSOR_HAND);

    if (left_mouse_pressed) {
      Color new_color = mult_color(color, 0.8f);
      draw_quad(constraints, new_color, radius, align);
    } else {
      Color new_color = mult_color(color, 0.9f);
      draw_quad(constraints, new_color, radius, align);
    }
  } else if (state == BUTTON_STATE_DISABLED) {
    if (is_hovered) {
      zephr_set_cursor(ZEPHR_CURSOR_DISABLED);
    }

    Color new_color = color;
    new_color.a = 100;
    text_color.a = 100;
    draw_quad(constraints, new_color, radius, align);
  } else {
    draw_quad(constraints, color, radius, align);
  }

  if (text) {
    UIConstraints text_constraints = {0};

    set_parent_constraint(&text_constraints, constraints);
    set_x_constraint(&text_constraints, 0, UI_CONSTRAINT_RELATIVE_PIXELS);
    set_y_constraint(&text_constraints, 0, UI_CONSTRAINT_RELATIVE_PIXELS);
    set_width_constraint(&text_constraints, 1.0, UI_CONSTRAINT_RELATIVE_PIXELS);

    u8 font_size = (u8)((constraints->width) / (text_constraints.width * 0.1 * 65.f));

    // TODO: need to adjust the font size based on the text height

    draw_text(text, font_size, text_constraints, text_color, ALIGN_CENTER);
  }

  if (is_hovered && state == BUTTON_STATE_ACTIVE && zephr_ctx->mouse.released && zephr_ctx->mouse.button == ZEPHR_MOUSE_BUTTON_LEFT) {
    return true;
  }

  return false;
}

bool draw_icon_button(UIConstraints *constraints, Color btn_color, const TextureId icon_tex_id, f32 radius, Alignment align, ButtonState state) {
  CORE_DEBUG_ASSERT(icon_tex_id, "draw_icon_button() requires that you provide an icon texture");

  Rect rect = {0};
  Color icon_color = COLOR_WHITE;

  apply_constraints(constraints, &rect.pos, &rect.size);
  apply_alignment(align, constraints, &rect.pos, rect.size);

  bool is_hovered = inside_rect(&rect, &zephr_ctx->mouse.pos);
  bool left_mouse_pressed = zephr_ctx->mouse.pressed && zephr_ctx->mouse.button == ZEPHR_MOUSE_BUTTON_LEFT;

  if (is_hovered && state == BUTTON_STATE_ACTIVE) {
    zephr_set_cursor(ZEPHR_CURSOR_HAND);

    if (left_mouse_pressed) {
      btn_color = mult_color(btn_color, 0.8f);
      icon_color = mult_color(icon_color, 0.8f);
    } else {
      btn_color = mult_color(btn_color, 0.9f);
      icon_color = mult_color(icon_color, 0.9f);
    }
  } else if (state == BUTTON_STATE_DISABLED) {
    if (is_hovered) {
      zephr_set_cursor(ZEPHR_CURSOR_DISABLED);
    }

    icon_color.a = 100;
    btn_color.a = 100;
  }

  draw_quad(constraints, btn_color, radius, align);

  UIConstraints icon_constraints = {0};

  set_parent_constraint(&icon_constraints, constraints);
  set_x_constraint(&icon_constraints, 0, UI_CONSTRAINT_RELATIVE_PIXELS);
  set_y_constraint(&icon_constraints, 0, UI_CONSTRAINT_RELATIVE_PIXELS);
  set_width_constraint(&icon_constraints, constraints->width * 0.8f, UI_CONSTRAINT_FIXED);
  set_height_constraint(&icon_constraints, constraints->height * 0.8f, UI_CONSTRAINT_FIXED);
  draw_texture(&icon_constraints, icon_tex_id, icon_color, 0, ALIGN_CENTER);

  if (is_hovered && state == BUTTON_STATE_ACTIVE && zephr_ctx->mouse.released && zephr_ctx->mouse.button == ZEPHR_MOUSE_BUTTON_LEFT) {
    return true;
  }

  return false;
}


/* enum Element { */
/*   Rect, */
/*   Circle, */
/* }; */

/* struct UIElement { */
/*   Vec2 pos; */
/*   Size size; */
/*   Color *color; */
/*   enum Element type; */
/* }; */

/* struct UIText { */
/*   Vec2 pos; */
/*   float scale; */
/*   Color *color; */
/*   const char* text; */
/* }; */

/* struct UIElement *create_element(Vec2 pos, Size size, Color *color, enum Element type) { */
/*   struct UIElement *element = malloc(sizeof(struct UIElement)); */
/*   element->pos = pos; */
/*   element->size = size; */
/*   element->color = color; */
/*   element->type = type; */
/*   return element; */
/* } */