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[vchess.git] / client / src / variants / Magnetic.js

import { ChessRules, PiPo } from "@/base_rules";

export const VariantRules = class  MagneticRules extends ChessRules
{
  static get HasEnpassant() { return false; }

  getPotentialMovesFrom([x,y])
  {
    let standardMoves = super.getPotentialMovesFrom([x,y]);
    let moves = [];
    standardMoves.forEach(m => {
      let newMove_s = this.applyMagneticLaws(m);
      if (newMove_s.length == 1)
        moves.push(newMove_s[0]);
      else //promotion
        moves = moves.concat(newMove_s);
    });
    return moves;
  }

  // Complete a move with magnetic actions
  // TODO: job is done multiple times for (normal) promotions.
  applyMagneticLaws(move)
  {
    if (move.appear[0].p == V.KING && move.appear.length==1)
      return [move]; //kings are not charged
    const aIdx = (move.appear[0].p != V.KING ? 0 : 1); //if castling, rook is charged
    const [x,y] = [move.appear[aIdx].x, move.appear[aIdx].y];
    const color = this.turn;
    const lastRank = (color=="w" ? 0 : 7);
    const standardMove = JSON.parse(JSON.stringify(move));
    this.play(standardMove);
    for (let step of [[-1,0],[1,0],[0,-1],[0,1]])
    {
      let [i,j] = [x+step[0],y+step[1]];
      while (V.OnBoard(i,j))
      {
        if (this.board[i][j] != V.EMPTY)
        {
          // Found something. Same color or not?
          if (this.getColor(i,j) != color)
          {
            // Attraction
            if ((Math.abs(i-x)>=2 || Math.abs(j-y)>=2) && this.getPiece(i,j) != V.KING)
            {
              move.vanish.push(
                new PiPo({
                  p:this.getPiece(i,j),
                  c:this.getColor(i,j),
                  x:i,
                  y:j
                })
              );
              move.appear.push(
                new PiPo({
                  p:this.getPiece(i,j),
                  c:this.getColor(i,j),
                  x:x+step[0],
                  y:y+step[1]
                })
              );
            }
          }
          else
          {
            // Repulsion
            if (this.getPiece(i,j) != V.KING)
            {
              // Push it until we meet an obstacle or edge of the board
              let [ii,jj] = [i+step[0],j+step[1]];
              while (V.OnBoard(ii,jj))
              {
                if (this.board[ii][jj] != V.EMPTY)
                  break;
                ii += step[0];
                jj += step[1];
              }
              ii -= step[0];
              jj -= step[1];
              if (Math.abs(ii-i)>=1 || Math.abs(jj-j)>=1)
              {
                move.vanish.push(
                  new PiPo({
                    p:this.getPiece(i,j),
                    c:this.getColor(i,j),
                    x:i,
                    y:j
                  })
                );
                move.appear.push(
                  new PiPo({
                    p:this.getPiece(i,j),
                    c:this.getColor(i,j),
                    x:ii,
                    y:jj
                  })
                );
              }
            }
          }
          break;
        }
        i += step[0];
        j += step[1];
      }
    }
    this.undo(standardMove);
    let moves = [];
    // Scan move for pawn (max 1) on 8th rank
    for (let i=1; i<move.appear.length; i++)
    {
      if (move.appear[i].p==V.PAWN && move.appear[i].c==color
        && move.appear[i].x==lastRank)
      {
        move.appear[i].p = V.ROOK;
        moves.push(move);
        for (let piece of [V.KNIGHT, V.BISHOP, V.QUEEN])
        {
          let cmove = JSON.parse(JSON.stringify(move));
          cmove.appear[i].p = piece;
          moves.push(cmove);
        }
        // Swap appear[i] and appear[0] for moves presentation (TODO: this is awkward)
        moves.forEach(m => {
          let tmp = m.appear[0];
          m.appear[0] = m.appear[i];
          m.appear[i] = tmp;
        });
        break;
      }
    }
    if (moves.length == 0) //no pawn on 8th rank
      moves.push(move);
    return moves;
  }

  atLeastOneMove()
  {
    if (this.kingPos[this.turn][0] < 0)
      return false;
    return true; //TODO: is it right?
  }

  underCheck(color)
  {
    return false; //there is no check
  }

  getCheckSquares(move)
  {
    return [];
  }

  updateVariables(move)
  {
    super.updateVariables(move);
    const c = move.vanish[0].c;
    if (move.vanish.length >= 2 && move.vanish[1].p == V.KING)
    {
      // We took opponent king !
      const oppCol = V.GetOppCol(c);
      this.kingPos[oppCol] = [-1,-1];
      this.castleFlags[oppCol] = [false,false];
    }
    // Did we magnetically move our (init) rooks or opponents' ones ?
    const firstRank = (c == "w" ? 7 : 0);
    const oppFirstRank = 7 - firstRank;
    const oppCol = V.GetOppCol(c);
    move.vanish.forEach(psq => {
      if (psq.x == firstRank && this.INIT_COL_ROOK[c].includes(psq.y))
        this.castleFlags[c][psq.y==this.INIT_COL_ROOK[c][0] ? 0 : 1] = false;
      else if (psq.x == oppFirstRank && this.INIT_COL_ROOK[oppCol].includes(psq.y))
        this.castleFlags[oppCol][psq.y==this.INIT_COL_ROOK[oppCol][0] ? 0 : 1] = false;
    });
  }

  unupdateVariables(move)
  {
    super.unupdateVariables(move);
    const c = move.vanish[0].c;
    const oppCol = V.GetOppCol(c);
    if (this.kingPos[oppCol][0] < 0)
    {
      // Last move took opponent's king
      for (let psq of move.vanish)
      {
        if (psq.p == 'k')
        {
          this.kingPos[oppCol] = [psq.x, psq.y];
          break;
        }
      }
    }
  }

  getCurrentScore()
  {
    const color = this.turn;
    const kp = this.kingPos[color];
    if (kp[0] < 0) //king disappeared
      return (color == "w" ? "0-1" : "1-0");
    if (this.atLeastOneMove()) // game not over
      return "*";
    return "1/2"; //no moves but kings still there
  }

  static get THRESHOLD_MATE()
  {
    return 500; //checkmates evals may be slightly below 1000
  }
}