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

import { ChessRules, PiPo, Move } from "@/base_rules";
import { ArrayFun } from "@/utils/array";
import { randInt, shuffle } from "@/utils/alea";

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

  static get CanFlip() {
    return false;
  }

  setFlags(fenflags) {
    this.pawnFlags = {
      w: [...Array(8).fill(true)], //pawns can move 2 squares?
      b: [...Array(8).fill(true)]
    };
    for (let c of ["w", "b"]) {
      for (let i = 0; i < 8; i++)
        this.pawnFlags[c][i] = fenflags.charAt((c == "w" ? 0 : 8) + i) == "1";
    }
  }

  aggregateFlags() {
    return this.pawnFlags;
  }

  disaggregateFlags(flags) {
    this.pawnFlags = flags;
  }

  static GenRandInitFen() {
    let pieces = { w: new Array(8), b: new Array(8) };
    // Shuffle pieces on first and fifth rank
    for (let c of ["w", "b"]) {
      let positions = ArrayFun.range(8);

      // Get random squares for bishops
      let randIndex = 2 * randInt(4);
      const bishop1Pos = positions[randIndex];
      // The second bishop must be on a square of different color
      let randIndex_tmp = 2 * randInt(4) + 1;
      const bishop2Pos = positions[randIndex_tmp];
      // Remove chosen squares
      positions.splice(Math.max(randIndex, randIndex_tmp), 1);
      positions.splice(Math.min(randIndex, randIndex_tmp), 1);

      // Get random squares for knights
      randIndex = randInt(6);
      const knight1Pos = positions[randIndex];
      positions.splice(randIndex, 1);
      randIndex = randInt(5);
      const knight2Pos = positions[randIndex];
      positions.splice(randIndex, 1);

      // Get random square for queen
      randIndex = randInt(4);
      const queenPos = positions[randIndex];
      positions.splice(randIndex, 1);

      // Rooks and king positions are now fixed,
      // because of the ordering rook-king-rook
      const rook1Pos = positions[0];
      const kingPos = positions[1];
      const rook2Pos = positions[2];

      // Finally put the shuffled pieces in the board array
      pieces[c][rook1Pos] = "r";
      pieces[c][knight1Pos] = "n";
      pieces[c][bishop1Pos] = "b";
      pieces[c][queenPos] = "q";
      pieces[c][kingPos] = "k";
      pieces[c][bishop2Pos] = "b";
      pieces[c][knight2Pos] = "n";
      pieces[c][rook2Pos] = "r";
    }
    return (
      "8/8/pppppppp/" +
      pieces["b"].join("") +
      "/8/8/PPPPPPPP/" +
      pieces["w"].join("").toUpperCase() +
      // 16 flags: can pawns advance 2 squares?
      " w 0 1111111111111111"
    );
  }

  // Output basically x % 8 (circular board)
  static ComputeX(x) {
    let res = x % V.size.x;
    if (res < 0)
      res += V.size.x;
    return res;
  }

  getSlideNJumpMoves([x, y], steps, oneStep) {
    let moves = [];
    outerLoop: for (let step of steps) {
      let i = V.ComputeX(x + step[0]);
      let j = y + step[1];
      while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
        moves.push(this.getBasicMove([x, y], [i, j]));
        if (oneStep !== undefined) continue outerLoop;
        i = V.ComputeX(i + step[0]);
        j += step[1];
      }
      if (V.OnBoard(i, j) && this.canTake([x, y], [i, j]))
        moves.push(this.getBasicMove([x, y], [i, j]));
    }
    return moves;
  }

  getPotentialPawnMoves([x, y]) {
    const color = this.turn;
    let moves = [];
    const [sizeX, sizeY] = [V.size.x, V.size.y];
    // All pawns go in the same direction!
    const shiftX = -1;
    const startRank = color == "w" ? sizeX - 2 : 2;

    // One square forward
    const nextRow = V.ComputeX(x + shiftX);
    if (this.board[nextRow][y] == V.EMPTY) {
      moves.push(this.getBasicMove([x, y], [nextRow, y]));
      if (
        x == startRank &&
        this.pawnFlags[color][y] &&
        this.board[x + 2 * shiftX][y] == V.EMPTY
      ) {
        // Two squares jump
        moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
      }
    }
    // Captures
    for (let shiftY of [-1, 1]) {
      if (
        y + shiftY >= 0 &&
        y + shiftY < sizeY &&
        this.board[nextRow][y + shiftY] != V.EMPTY &&
        this.canTake([x, y], [nextRow, y + shiftY])
      ) {
        moves.push(this.getBasicMove([x, y], [nextRow, y + shiftY]));
      }
    }

    return moves;
  }

  getPotentialKingMoves(sq) {
    return this.getSlideNJumpMoves(
      sq,
      V.steps[V.ROOK].concat(V.steps[V.BISHOP]),
      "oneStep"
    );
  }

  filterValid(moves) {
    const filteredMoves = super.filterValid(moves);
    // If at least one full move made, everything is allowed:
    if (this.movesCount >= 2)
      return filteredMoves;
    // Else, forbid check:
    const oppCol = V.GetOppCol(this.turn);
    return filteredMoves.filter(m => {
      this.play(m);
      const res = !this.underCheck(oppCol);
      this.undo(m);
      return res;
    });
  }

  isAttackedByPawn([x, y], colors) {
    const pawnShift = 1;
    const attackerRow = V.ComputeX(x + pawnShift);
    for (let c of colors) {
      for (let i of [-1, 1]) {
        if (
          y + i >= 0 &&
          y + i < V.size.y &&
          this.getPiece(attackerRow, y + i) == V.PAWN &&
          this.getColor(attackerRow, y + i) == c
        ) {
          return true;
        }
      }
    }
    return false;
  }

  isAttackedBySlideNJump([x, y], colors, piece, steps, oneStep) {
    for (let step of steps) {
      let rx = V.ComputeX(x + step[0]),
          ry = y + step[1];
      while (V.OnBoard(rx, ry) && this.board[rx][ry] == V.EMPTY && !oneStep) {
        rx = V.ComputeX(rx + step[0]);
        ry += step[1];
      }
      if (
        V.OnBoard(rx, ry) &&
        this.getPiece(rx, ry) === piece &&
        colors.includes(this.getColor(rx, ry))
      ) {
        return true;
      }
    }
    return false;
  }

  getFlagsFen() {
    // Return pawns flags
    let flags = "";
    for (let c of ["w", "b"]) {
      for (let i = 0; i < 8; i++) flags += this.pawnFlags[c][i] ? "1" : "0";
    }
    return flags;
  }

  updateVariables(move) {
    const c = move.vanish[0].c;
    const secondRank = {"w":6, "b":2};
    // Update king position + flags
    if (move.vanish[0].p == V.KING && move.appear.length > 0) {
      this.kingPos[c][0] = move.appear[0].x;
      this.kingPos[c][1] = move.appear[0].y;
    }
    else if (move.vanish[0].p == V.PAWN && secondRank[c] == move.start.x)
      // This move turns off a 2-squares pawn flag
      this.pawnFlags[c][move.start.y] = false;
  }

  static get VALUES() {
    return {
      p: 1,
      r: 5,
      n: 3,
      b: 4,
      q: 10,
      k: 1000
    };
  }
};