Draft Hiddenqueen, Grasshopper and Knightmate chess (rules unwritten)

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

diff --git a/client/src/variants/Grasshopper.js b/client/src/variants/Grasshopper.js
new file mode 100644 (file)
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+++ b/client/src/variants/Grasshopper.js
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+import { ChessRules } from "@/base_rules";
+import { ArrayFun } from "@/utils/array";
+import { randInt } from "@/utils/alea";
+
+export const VariantRules = class GrasshopperRules extends ChessRules {
+  static get GRASSHOPPER() {
+    return "g";
+  }
+
+  static get PIECES() {
+    return ChessRules.PIECES.concat([V.GRASSHOPPER]);
+  }
+
+  getPpath(b) {
+    return (b[1] == V.GRASSHOPPER ? "Grasshopper/" : "") + b;
+  }
+
+  getPotentialMovesFrom([x, y]) {
+    switch (this.getPiece(x, y)) {
+      case V.GRASSHOPPER:
+        return this.getPotentialGrasshopperMoves([x, y]);
+      default:
+        return super.getPotentialMovesFrom([x, y]);
+    }
+  }
+
+  getPotentialGrasshopperMoves([x, y]) {
+    let moves = [];
+    // Look in every direction until an obstacle (to jump) is met
+    for (const step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
+      let i = x + step[0];
+      let j = y + step[1];
+      while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
+        i += step[0];
+        j += step[1];
+      }
+      // Move is valid if the next square is empty or occupied by enemy
+      const nextSq = [i+step[0], j+step[1]];
+      if (V.OnBoard(nextSq[0], nextSq[1]) && this.canTake([x, y], nextSq))
+        moves.push(this.getBasicMove([x, y], nextSq));
+    }
+    return moves;
+  }
+
+  isAttacked(sq, colors) {
+    return (
+      super.isAttacked(sq, colors) ||
+      this.isAttackedByGrasshopper(sq, colors)
+    );
+  }
+
+  isAttackedByGrasshopper([x, y], colors) {
+    // Reversed process: is there an adjacent obstacle,
+    // and a grasshopper next in the same line?
+    for (const step of V.steps[V.ROOK].concat(V.steps[V.BISHOP])) {
+      const nextSq = [x+step[0], y+step[1]];
+      if (
+        V.OnBoard(nextSq[0], nextSq[1]) &&
+        this.board[nextSq[0]][nextSq[1]] != V.EMPTY
+      ) {
+        let i = nextSq[0] + step[0];
+        let j = nextSq[1] + step[1];
+        while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
+          i += step[0];
+          j += step[1];
+        }
+        if (
+          V.OnBoard(i, j) &&
+          this.getPiece(i, j) == V.GRASSHOPPER &&
+          colors.includes(this.getColor(i, j))
+        ) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  static get VALUES() {
+    return Object.assign(
+      // TODO: grasshoppers power decline when less pieces on board...
+      { g: 3 },
+      ChessRules.VALUES
+    );
+  }
+
+  static GenRandInitFen() {
+    let pieces = { w: new Array(10), b: new Array(10) };
+    for (let c of ["w", "b"]) {
+      let positions = ArrayFun.range(8);
+
+      // Get random squares for grasshoppers (unconstrained)
+      let randIndex = randInt(8);
+      const grasshopper1Pos = positions[randIndex];
+      positions.splice(randIndex, 1);
+      randIndex = randInt(7);
+      const grasshopper2Pos = positions[randIndex];
+      positions.splice(randIndex, 1);
+
+      // Knights
+      randIndex = randInt(6);
+      let knight1Pos = positions[randIndex];
+      positions.splice(randIndex, 1);
+      randIndex = randInt(5);
+      let knight2Pos = positions[randIndex];
+      positions.splice(randIndex, 1);
+
+      // Queen
+      randIndex = randInt(4);
+      let queenPos = positions[randIndex];
+      positions.splice(randIndex, 1);
+
+      let rook1Pos = positions[0];
+      let kingPos = positions[1];
+      let rook2Pos = positions[2];
+
+      pieces[c][rook1Pos] = "r";
+      pieces[c][knight1Pos] = "n";
+      pieces[c][grasshopper1Pos] = "g";
+      pieces[c][queenPos] = "q";
+      pieces[c][kingPos] = "k";
+      pieces[c][grasshopper2Pos] = "g";
+      pieces[c][knight2Pos] = "n";
+      pieces[c][rook2Pos] = "r";
+    }
+    return (
+      pieces["b"].join("") +
+      "/pppppppp/8/8/8/8/PPPPPPPP/" +
+      pieces["w"].join("").toUpperCase() +
+      " w 0 1111 -"
+    );
+  }
+};