Add true repetition detection

[vchess.git] / public / javascripts / base_rules.js

diff --git a/public/javascripts/base_rules.js b/public/javascripts/base_rules.js
index 5020094..a10a43c 100644 (file)
--- a/public/javascripts/base_rules.js
+++ b/public/javascripts/base_rules.js
@@ -54,6 +54,7 @@ class ChessRules
        constructor(fen, moves)
        {
                this.moves = moves;
+               this.hashStates = {}; //for repetitions detection
                // Use fen string to initialize variables, flags and board
                this.board = VariantRules.GetBoard(fen);
                this.setFlags(fen);
@@ -727,6 +728,18 @@ class ChessRules
                        this.kingPos[c] = [move.start.x, move.start.y];
        }
 
+       // Store a hash of the position + flags + turn after a move is played
+       // (for repetitions detection)
+       addHashState()
+       {
+               const strToHash = this.getFen() + " " + this.turn;
+               const hash = hex_md5(strToHash);
+               if (!this.hashStates[hash])
+                       this.hashStates[hash] = 1;
+               else
+                       this.hashStates[hash]++;
+       }
+
        play(move, ingame)
        {
                // DEBUG:
@@ -741,6 +754,9 @@ class ChessRules
                this.moves.push(move);
                this.epSquares.push( this.getEpSquare(move) );
                VariantRules.PlayOnBoard(this.board, move);
+
+               if (!!ingame)
+                       this.addHashState();
        }
 
        undo(move)
@@ -760,22 +776,10 @@ class ChessRules
        //////////////
        // END OF GAME
 
-       // Basic check for 3 repetitions (in the last moves only)
-       // TODO: extend to usual 3-repetition recognition (storing FEN with move?)
+       // Check for 3 repetitions (position + flags + turn)
        checkRepetition()
        {
-               if (this.moves.length >= 8)
-               {
-                       const L = this.moves.length;
-                       if (_.isEqual(this.moves[L-1], this.moves[L-5]) &&
-                               _.isEqual(this.moves[L-2], this.moves[L-6]) &&
-                               _.isEqual(this.moves[L-3], this.moves[L-7]) &&
-                               _.isEqual(this.moves[L-4], this.moves[L-8]))
-                       {
-                               return true;
-                       }
-               }
-               return false;
+               return Object.values(this.hashStates).some(elt => { return (elt >= 3); });
        }
 
        // Is game over ? And if yes, what is the score ?