/*
	author: leeenx
	@ 贪吃蛇的 model 类 
*/

// 随机打散数组
import randomList from "../lib/utils/randomList";

// 链表类
import Chain from "../lib/utils/Chain";

// model 类
export default class model {
  // 构造函数
  constructor() {
    // 活动空间
    this.zone = [];

    // 蛇链表
    this.snake = new Chain();

    // 封装 snake 的 unshift, push, shift, pop 方法
    let { unshift, push, shift, pop } = this.snake;

    this.snake.unshift = (index) => {
      unshift.call(this.snake, index);
      // 更新 zone
      this.updateZone(index, "snake", "unshift");
    };

    this.snake.shift = () => {
      let index = shift.call(this.snake).data;
      // 更新 zone
      this.updateZone(index, undefined, "shift");
    };

    this.snake.push = (index) => {
      push.call(this.snake, index);
      // 更新 zone
      this.updateZone(index, "snake", "push");
    };

    this.snake.pop = () => {
      let index = pop.call(this.snake).data;
      // 更新 zone
      this.updateZone(index, undefined, "pop");
    };

    // 投食后自动更新 zone
    Reflect.defineProperty(this, "food", {
      get: () => {
        return Reflect.get(this, "_food");
      },
      set: (value) => {
        // 将值记录到 _food
        Reflect.set(this, "_food", value);
        // 更新 zone
        value !== undefined && this.updateZone(value, "food");
      },
    });
  }

  // 初始化
  init(config) {
    // 指定 zone 长度
    this.zone.length = config.row * config.column;
    // 填充 zone 的初始信息
    for (let i = 0, len = this.zone.length; i < len; ++i) {
      let [col, row] = [i % config.column, Math.floor(i / config.column)];
      this.zone[i] = {
        col: col,
        row: row,
        left: col > 0 ? i - 1 : -1,
        right: col < config.column - 1 ? i + 1 : -1,
        up: row > 0 ? i - config.column : -1,
        down: row < config.row - 1 ? i + config.column : -1,
      };
    }
    this.snake.push(
      Math.floor(config.column / 2) + Math.floor(config.row / 2) * config.column
    );
    // 初始蛇的长度
    while (this.snake.length < config.min) {
      let index = this.snake.length
        ? this.neighbour()
        : (Math.random() * this.zone.length) >> 0;
      this.snake.unshift(index);
    }
    // 投食
    this.feed();
  }

  // 销毁
  destroy() {
    // 清空 zone 内容
    this.zone = [];
    // 清空链表数组
    this.snake.clean();
    // 清除食物
    this.food = undefined;
    // 清空 bar
    delete this.bar;
  }

  // 邻居元素
  neighbour() {
    return randomList(
      [this.leader.left, this.leader.right, this.leader.up, this.leader.down],
      1,
      (index) => index !== -1 && this.zone[index].fill === undefined
    );
  }

  // zone 区域更新状态
  updateZone(index, fill, type) {
    // console.log(index, fill, type);
    // fill == undefine 表示 free
    this.zone[index].fill = fill;
    // leader 更新
    this.updateLeader();
  }

  // 更新蛇头在 zone 的坐标
  updateLeader() {
    if (this.snake.length !== 0) {
      this.leader = this.zone[this.snake.first().data];
    }
    this.dirty = true;
  }

  // 清理dirty
  cleanDirty() {
    this.dirty = false;
  }

  // 蛇运动
  move(direction) {
    let index = this.leader[direction],
      skipTail = false;
    if (-1 === index) {
      // 撞墙
      this.collision("bounds");
      return;
    }
    if (this.snake.last().data === index) {
      // 即将撞上的尾巴
      skipTail = true;
    }
    let next = this.zone[index];
    switch (next.fill) {
      // 吃食
      case "food":
        this.eat();
        break;
      // 撞到自己
      case "snake": {
        // 判断是否咬尾
        if (!skipTail) {
          this.collision("self");
          break;
        }
      }
      // 默认前进
      default:
        this.snake.pop() & this.snake.unshift(index);
    }
  }

  // 吃食
  eat() {
    // 食物变成了头
    this.snake.unshift(this.food);
    // 重新投食
    this.feed();
  }

  // 撞到东西
  collision(bar) {
    // bar 不为空就认为游戏结束
    this.bar = bar;
  }

  // 赌博
  bet() {
    let rnd = (Math.random() * this.zone.length) >> 0;
    return this.zone[rnd].fill === undefined ? rnd : -1;
  }

  // 随机喂食
  feed() {
    // 赌一次
    let rnd = this.bet();
    if (rnd !== -1) {
      this.food = rnd;
      return;
    }
    let index = 0,
      count = 0,
      len = this.zone.length - this.snake.length;
    rnd = ((Math.random() * count) >> 0) + 1;
    // 无法投食
    if (0 === len) {
      this.food = undefined;
      return;
    }
    while (rnd !== count) {
      this.zone[index++].fill === undefined && ++count;
    }
    this.food = index - 1;
  }
}