From 6177824d28aea903843f409796497114b06d6391 Mon Sep 17 00:00:00 2001
From: GuillaumeSD <gsd.lfny@gmail.com>
Date: Tue, 26 Mar 2024 20:19:46 +0100
Subject: [PATCH] fix : remove piece recapture from great moves

---
 src/lib/chess.ts                             | 25 ++++++++++++++++----
 src/lib/engine/helpers/moveClassification.ts | 21 +++++++++++++---
 2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/src/lib/chess.ts b/src/lib/chess.ts
index 8216065..8392e4a 100644
--- a/src/lib/chess.ts
+++ b/src/lib/chess.ts
@@ -1,6 +1,6 @@
 import { EvaluateGameParams, PositionEval } from "@/types/eval";
 import { Game } from "@/types/game";
-import { Chess, PieceSymbol } from "chess.js";
+import { Chess, PieceSymbol, Square } from "chess.js";
 import { getPositionWinPercentage } from "./engine/helpers/winPercentage";
 import { Color } from "@/types/enums";
 
@@ -156,15 +156,30 @@ export const getWhoIsCheckmated = (fen: string): "w" | "b" | null => {
 export const uciMoveParams = (
   uciMove: string
 ): {
-  from: string;
-  to: string;
+  from: Square;
+  to: Square;
   promotion?: string | undefined;
 } => ({
-  from: uciMove.slice(0, 2),
-  to: uciMove.slice(2, 4),
+  from: uciMove.slice(0, 2) as Square,
+  to: uciMove.slice(2, 4) as Square,
   promotion: uciMove.slice(4, 5) || undefined,
 });
 
+export const isSimplePieceRecapture = (
+  fen: string,
+  uciMoves: [string, string]
+): boolean => {
+  const game = new Chess(fen);
+  const moves = uciMoves.map((uciMove) => uciMoveParams(uciMove));
+
+  if (moves[0].to !== moves[1].to) return false;
+
+  const piece = game.get(moves[0].to);
+  if (piece) return true;
+
+  return false;
+};
+
 export const getIsPieceSacrifice = (
   fen: string,
   playedMove: string,
diff --git a/src/lib/engine/helpers/moveClassification.ts b/src/lib/engine/helpers/moveClassification.ts
index 4c7174f..bce1b2a 100644
--- a/src/lib/engine/helpers/moveClassification.ts
+++ b/src/lib/engine/helpers/moveClassification.ts
@@ -5,7 +5,7 @@ import {
 } from "./winPercentage";
 import { MoveClassification } from "@/types/enums";
 import { openings } from "@/data/openings";
-import { getIsPieceSacrifice } from "@/lib/chess";
+import { getIsPieceSacrifice, isSimplePieceRecapture } from "@/lib/chess";
 
 export const getMovesClassification = (
   rawPositions: PositionEval[],
@@ -63,12 +63,18 @@ export const getMovesClassification = (
       };
     }
 
+    const fenTwoMovesAgo = index > 1 ? fens[index - 2] : null;
+    const uciNextTwoMoves: [string, string] | null =
+      index > 1 ? [uciMoves[index - 2], uciMoves[index - 1]] : null;
+
     if (
       isGreatMove(
         lastPositionWinPercentage,
         positionWinPercentage,
         isWhiteMove,
-        lastPositionAlternativeLineWinPercentage
+        lastPositionAlternativeLineWinPercentage,
+        fenTwoMovesAgo,
+        uciNextTwoMoves
       )
     ) {
       return {
@@ -155,7 +161,9 @@ const isGreatMove = (
   lastPositionWinPercentage: number,
   positionWinPercentage: number,
   isWhiteMove: boolean,
-  lastPositionAlternativeLineWinPercentage: number | undefined
+  lastPositionAlternativeLineWinPercentage: number | undefined,
+  fenTwoMovesAgo: string | null,
+  uciMoves: [string, string] | null
 ): boolean => {
   if (!lastPositionAlternativeLineWinPercentage) return false;
 
@@ -164,6 +172,13 @@ const isGreatMove = (
     (isWhiteMove ? 1 : -1);
   if (winPercentageDiff < -2) return false;
 
+  if (
+    fenTwoMovesAgo &&
+    uciMoves &&
+    isSimplePieceRecapture(fenTwoMovesAgo, uciMoves)
+  )
+    return false;
+
   const hasChangedGameOutcome = getHasChangedGameOutcome(
     lastPositionWinPercentage,
     positionWinPercentage,