Improve Paco-Sako rules. Draft Isardam

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

diff --git a/client/src/variants/Isardam.js b/client/src/variants/Isardam.js
new file mode 100644 (file)
index 0000000..4ca9a85
--- /dev/null
+++ b/client/src/variants/Isardam.js
@@ -0,0 +1,76 @@
+import { ChessRules } from "@/base_rules";
+
+export class IsardamRules extends ChessRules {
+
+  isImmobilized(sq) {
+    const oppCol = V.GetOppCol(this.getColor(sq[0], sq[1]));
+    const piece = this.getPiece(sq[0], sq[1]);
+    let steps = [];
+    switch (piece) {
+      // NOTE: cannot use super.isAttackedByXXX
+      // because it would call the redefined isAttackedBySlideNJump
+      // => Infinite recursive calls.
+      case V.PAWN: {
+        const forward = (oppCol == 'w' ? 1 : -1);
+        steps = [[forward, 1], [forward, -1]];
+        break;
+      }
+      case V.ROOK:
+      case V.BISHOP:
+      case V.KNIGHT:
+        steps = V.steps[piece];
+        break;
+      case V.KING:
+      case V.QUEEN:
+        steps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
+        break;
+    }
+    return super.isAttackedBySlideNJump(
+      sq, oppCol, piece, steps, [V.KING, V.PAWN, V.KNIGHT].includes(piece))
+  }
+
+  getPotentialMovesFrom([x, y]) {
+    return (
+      super.getPotentialMovesFrom([x, y]).filter(m => {
+        let res = true;
+        this.play(m);
+        if (this.isImmobilized([m.end.x, m.end.y])) res = false;
+        else {
+          // Check discovered attacks
+          for (let step of V.steps[V.BISHOP].concat(V.steps[V.ROOK])) {
+            let allowedPieces = [V.QUEEN];
+            if (step[0] == 0 || step[1] == 0) allowedPieces.push(V.ROOK);
+            else allowedPieces.push(V.BISHOP);
+            let [i, j] = [m.start.x + step[0], m.start.y + step[1]];
+            while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
+              i += step[0];
+              j += step[1];
+            }
+            if (V.OnBoard(i, j)) {
+              const meet = { c: this.getColor(i, j), p: this.getPiece(i, j) };
+              if (allowedPieces.includes(meet.p)) {
+                // Search in the other direction
+                [i, j] = [m.start.x - step[0], m.start.y - 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) == meet.p &&
+                  this.getColor(i, j) != meet.c
+                ) {
+                  res = false;
+                  break;
+                }
+              }
+            }
+          }
+        }
+        this.undo(m);
+        return res;
+      })
+    );
+  }
+
+};