2048.js

module.exports = class Game2048{
  constructor(size){
    this.size = size;
    this.layout = new Array(size);
    for(let i=0; i<size; i++){
      this.layout[i] = new Array(size);
    }
    //assert(this.size=this.layout.length)
    for(let i=0; i<size; i++){
      for(let j=0; j<size; j++){
        this.layout[i][j] = 0;
      }
    }
    this.__update_layout();
    this.__update_layout();

    //for test:
    // this.layout[0] = [0,0,0,0];
    // this.layout[1] = [0,0,2,0];
    // this.layout[2] = [0,0,0,4];
    // this.layout[3] = [0,0,0,0];
  }

  //show the current layout
  show(){
    for(let i=0; i<this.size; i++){
      console.log(this.layout[i]);
      for(let j=0; j<this.size; j++){
        //console.log("%10c",this.layout[i][j])
      }
    }
  //console.log(this.layout)
  }

  __move_left(){
    let movable = 0;
    for(let i = 0; i < this.size; i++){
      let compressed = [];
      let meetblank = 0;
      for(let j = 0; j < this.size; j++){
        if(this.layout[i][j]){
          compressed.push(this.layout[i][j]);
          if(meetblank)
            movable = 1;
        }
        else
          meetblank = 1;
      }
      
      for(let k = 0; k + 1 < compressed.length; k++){
        if(compressed[k] && compressed[k] === compressed[k+1]){
          movable = 1;
          compressed[k] *= 2;
          compressed = compressed.slice(0,k+1).concat(compressed.slice(k+2))
        }
      }
      
      this.layout[i] = compressed.concat(new Array(this.size-compressed.length).fill(0));
    }

    if(movable === 0){
      return false;
    }else{
      return true;
    }
  }

  __move_right(){
    for(let i = 0; i < this.size; i++){
      this.layout[i].reverse();
    }

    let result = this.__move_left();

    for(let i = 0; i < this.size; i++){
      this.layout[i].reverse();
    }

    return result;
  }

  
  __move_up(){
    let transpose = a => a[0].map((_, c) => a.map(r => r[c]));
    this.layout = transpose(this.layout);
    let result = this.__move_left();
    this.layout = transpose(this.layout);
    return result;
  }

  __move_down(){
    let transpose = a => a[0].map((_, c) => a.map(r => r[c]));
    this.layout = transpose(this.layout);
    let result = this.__move_right();
    this.layout = transpose(this.layout);
    return result;
  }

  __move(direction){

    if(direction === "left")
      return this.__move_left();
    else if(direction === "right")
      return this.__move_right();
    else if(direction === "up")
      return this.__move_up();
    else if(direction === "down")
      return this.__move_down();
  }

  move(direction){
    if(this.__move(direction)){
      if(this.__check_win()){
        console.log("You win!");
        return "win";
      }else{
        this.__update_layout();
        if(this.__check_movable()){
          return "continue";
        }else{
          console.log("You lost!");
          return "lost";
        }
      }
    }
    console.log("not movable");
    return "continue";
  }

  left(){
    return this.move("left");
  }

  right(){
    return this.move("right");
  }

  down(){
    return this.move("down");

  }

  up(){
    return this.move("up");
  }

  //judgut if already win
  __check_win(){
    for(let i=0; i<this.size; i++){
      for(let j=0; j<this.size; j++){
        if(this.layout[i][j]===2048){
          return true;
        }
      }
    }
    return false;
  }

  __new_w(){
    //in the ratio of 1:4 to generate 4:2
    return (Math.floor(5*Math.random())>0)?2:4;
  }

  //add one weight into the current layout
  __update_layout(){
    let empty_blocks = [];
    for(let i=0; i<this.size; i++){
      for(let j=0; j<this.size; j++){
        if(this.layout[i][j] === 0){
          empty_blocks.push([i,j]);
        }
      }
    }
    let insert_n = Math.floor(Math.random()*empty_blocks.length);
    var [insert_i,insert_j] = [empty_blocks[insert_n][0],empty_blocks[insert_n][1]];
    this.layout[insert_i][insert_j] = this.__new_w();

  }

  __check_movable(){
    for(let i=0; i<this.size; i++){
      for(let j=0; j<this.size; j++){
        if(this.layout[i][j] === 0){
          return true;
        }
      }
    }
    for(let i=0; i<this.size; i++){
      for(let j=0; j<this.size-1; j++){
        if(this.layout[i][j] === this.layout[i][j+1])
          return true;
      }
    }

    for(let j=0; j<this.size; j++){
      for(let i=0; i<this.size-1; i++){
        if(this.layout[i][j] === this.layout[i+1][j])
          return true;
      }
    }
    return false;
  }

}