feat : add accuracy calculation

src/lib/chess.ts

@@ -3,7 +3,11 @@ import { Game } from "@/types/game";
 import { Chess } from "chess.js";
 
 export const getFens = (game: Chess): string[] => {
-  return game.history({ verbose: true }).map((move) => move.before);
+  const history = game.history({ verbose: true });
+  const fens = history.map((move) => move.before);
+  fens.push(history[history.length - 1].after);
+
+  return fens;
 };
 
 export const getGameFromPgn = (pgn: string): Chess => {
@@ -106,3 +110,9 @@ export const getEvaluationBarValue = (
 
   return { whiteBarPercentage, label: pEval.toFixed(1) };
 };
+
+export const getWhoIsCheckmated = (fen: string): "w" | "b" | null => {
+  const game = new Chess(fen);
+  if (!game.isCheckmate()) return null;
+  return game.turn();
+};

src/lib/engine/helpers/accuracy.ts

@@ -0,0 +1,111 @@
+import {
+  ceilsNumber,
+  getHarmonicMean,
+  getStandardDeviation,
+  getWeightedMean,
+} from "@/lib/helpers";
+import { Accuracy, MoveEval } from "@/types/eval";
+
+export const computeAccuracy = (moves: MoveEval[]): Accuracy => {
+  const movesWinPercentage = moves.map(getPositionWinPercentage);
+
+  const weights = getAccuracyWeights(movesWinPercentage);
+
+  const movesAccuracy = getMovesAccuracy(movesWinPercentage);
+
+  const whiteAccuracy = getPlayerAccuracy(movesAccuracy, weights, "white");
+  const blackAccuracy = getPlayerAccuracy(movesAccuracy, weights, "black");
+
+  return {
+    white: whiteAccuracy,
+    black: blackAccuracy,
+  };
+};
+
+const getPlayerAccuracy = (
+  movesAccuracy: number[],
+  weights: number[],
+  player: "white" | "black"
+): number => {
+  const remainder = player === "white" ? 0 : 1;
+  const playerAccuracies = movesAccuracy.filter(
+    (_, index) => index % 2 === remainder
+  );
+  const playerWeights = weights.filter((_, index) => index % 2 === remainder);
+
+  const weightedMean = getWeightedMean(playerAccuracies, playerWeights);
+  const harmonicMean = getHarmonicMean(playerAccuracies);
+
+  return (weightedMean + harmonicMean) / 2;
+};
+
+const getAccuracyWeights = (movesWinPercentage: number[]): number[] => {
+  const windowSize = ceilsNumber(
+    Math.ceil(movesWinPercentage.length / 10),
+    2,
+    8
+  );
+
+  const windows: number[][] = [];
+  const halfWindowSize = Math.round(windowSize / 2);
+
+  for (let i = 1; i < movesWinPercentage.length; i++) {
+    const startIdx = i - halfWindowSize;
+    const endIdx = i + halfWindowSize;
+
+    if (startIdx < 0) {
+      windows.push(movesWinPercentage.slice(0, windowSize));
+      continue;
+    }
+
+    if (endIdx > movesWinPercentage.length) {
+      windows.push(movesWinPercentage.slice(-windowSize));
+      continue;
+    }
+
+    windows.push(movesWinPercentage.slice(startIdx, endIdx));
+  }
+
+  const weights = windows.map((window) => {
+    const std = getStandardDeviation(window);
+    return ceilsNumber(std, 0.5, 12);
+  });
+
+  return weights;
+};
+
+const getMovesAccuracy = (movesWinPercentage: number[]): number[] =>
+  movesWinPercentage.slice(1).map((winPercent, index) => {
+    const lastWinPercent = movesWinPercentage[index];
+    const winDiff = Math.abs(lastWinPercent - winPercent);
+
+    const rawAccuracy =
+      103.1668100711649 * Math.exp(-0.04354415386753951 * winDiff) -
+      3.166924740191411;
+
+    return Math.min(100, Math.max(0, rawAccuracy + 1));
+  });
+
+const getPositionWinPercentage = (move: MoveEval): number => {
+  if (move.lines[0].cp !== undefined) {
+    return getWinPercentageFromCp(move.lines[0].cp);
+  }
+
+  if (move.lines[0].mate !== undefined) {
+    return getWinPercentageFromMate(move.lines[0].mate);
+  }
+
+  throw new Error("No cp or mate in move");
+};
+
+const getWinPercentageFromMate = (mate: number): number => {
+  const mateInf = mate * Infinity;
+  return getWinPercentageFromCp(mateInf);
+};
+
+const getWinPercentageFromCp = (cp: number): number => {
+  const cpCeiled = ceilsNumber(cp, -1000, 1000);
+  const MULTIPLIER = -0.00368208;
+  const winChances = 2 / (1 + Math.exp(MULTIPLIER * cpCeiled)) - 1;
+  return 50 + 50 * winChances;
+};

src/lib/engine/helpers/parseResults.ts

@@ -0,0 +1,99 @@
+import { LineEval, MoveEval } from "@/types/eval";
+
+export const parseEvaluationResults = (
+  results: string[],
+  whiteToPlay: boolean
+): MoveEval => {
+  const parsedResults: MoveEval = {
+    bestMove: "",
+    lines: [],
+  };
+  const tempResults: Record<string, LineEval> = {};
+
+  for (const result of results) {
+    if (result.startsWith("bestmove")) {
+      const bestMove = getResultProperty(result, "bestmove");
+      if (bestMove) {
+        parsedResults.bestMove = bestMove;
+      }
+    }
+
+    if (result.startsWith("info")) {
+      const pv = getResultPv(result);
+      const multiPv = getResultProperty(result, "multipv");
+      const depth = getResultProperty(result, "depth");
+      if (!pv || !multiPv || !depth) continue;
+
+      if (
+        tempResults[multiPv] &&
+        parseInt(depth) < tempResults[multiPv].depth
+      ) {
+        continue;
+      }
+
+      const cp = getResultProperty(result, "cp");
+      const mate = getResultProperty(result, "mate");
+
+      tempResults[multiPv] = {
+        pv,
+        cp: cp ? parseInt(cp) : undefined,
+        mate: mate ? parseInt(mate) : undefined,
+        depth: parseInt(depth),
+        multiPv: parseInt(multiPv),
+      };
+    }
+  }
+
+  parsedResults.lines = Object.values(tempResults).sort(sortLines);
+
+  if (!whiteToPlay) {
+    parsedResults.lines = parsedResults.lines.map((line) => ({
+      ...line,
+      cp: line.cp ? -line.cp : line.cp,
+      mate: line.mate ? -line.mate : line.mate,
+    }));
+  }
+
+  return parsedResults;
+};
+
+const sortLines = (a: LineEval, b: LineEval): number => {
+  if (a.mate !== undefined && b.mate !== undefined) {
+    return a.mate - b.mate;
+  }
+
+  if (a.mate !== undefined) {
+    return -a.mate;
+  }
+
+  if (b.mate !== undefined) {
+    return b.mate;
+  }
+
+  return (b.cp ?? 0) - (a.cp ?? 0);
+};
+
+const getResultProperty = (
+  result: string,
+  property: string
+): string | undefined => {
+  const splitResult = result.split(" ");
+  const propertyIndex = splitResult.indexOf(property);
+
+  if (propertyIndex === -1 || propertyIndex + 1 >= splitResult.length) {
+    return undefined;
+  }
+
+  return splitResult[propertyIndex + 1];
+};
+
+const getResultPv = (result: string): string[] | undefined => {
+  const splitResult = result.split(" ");
+  const pvIndex = splitResult.indexOf("pv");
+
+  if (pvIndex === -1 || pvIndex + 1 >= splitResult.length) {
+    return undefined;
+  }
+
+  return splitResult.slice(pvIndex + 1);
+};

src/lib/engine/uciEngine.ts

@@ -2,9 +2,11 @@ import { EngineName } from "@/types/enums";
 import {
   EvaluatePositionWithUpdateParams,
   GameEval,
-  LineEval,
   MoveEval,
 } from "@/types/eval";
+import { parseEvaluationResults } from "./helpers/parseResults";
+import { computeAccuracy } from "./helpers/accuracy";
+import { getWhoIsCheckmated } from "../chess";
 
 export abstract class UciEngine {
   private worker: Worker;
@@ -104,14 +106,31 @@ export abstract class UciEngine {
 
     const moves: MoveEval[] = [];
     for (const fen of fens) {
+      const whoIsCheckmated = getWhoIsCheckmated(fen);
+      if (whoIsCheckmated) {
+        moves.push({
+          bestMove: "",
+          lines: [
+            {
+              pv: [],
+              depth: 0,
+              multiPv: 1,
+              mate: whoIsCheckmated === "w" ? -1 : 1,
+            },
+          ],
+        });
+        continue;
+      }
       const result = await this.evaluatePosition(fen, depth);
       moves.push(result);
     }
 
+    const accuracy = computeAccuracy(moves);
+
     this.ready = true;
     return {
-      moves,
-      accuracy: { white: 82.34, black: 67.49 }, // TODO: Calculate accuracy
+      moves: moves.slice(0, -1),
+      accuracy,
       settings: {
         engine: this.engineName,
         date: new Date().toISOString(),
@@ -131,7 +150,7 @@ export abstract class UciEngine {
 
     const whiteToPlay = fen.split(" ")[1] === "w";
 
-    return this.parseResults(results, whiteToPlay);
+    return parseEvaluationResults(results, whiteToPlay);
   }
 
   public async evaluatePositionWithUpdate({
@@ -148,7 +167,7 @@ export abstract class UciEngine {
     const whiteToPlay = fen.split(" ")[1] === "w";
 
     const onNewMessage = (messages: string[]) => {
-      const parsedResults = this.parseResults(messages, whiteToPlay);
+      const parsedResults = parseEvaluationResults(messages, whiteToPlay);
       setPartialEval(parsedResults);
     };
 
@@ -159,99 +178,4 @@ export abstract class UciEngine {
       onNewMessage
     );
   }
-
-  private parseResults(results: string[], whiteToPlay: boolean): MoveEval {
-    const parsedResults: MoveEval = {
-      bestMove: "",
-      lines: [],
-    };
-    const tempResults: Record<string, LineEval> = {};
-
-    for (const result of results) {
-      if (result.startsWith("bestmove")) {
-        const bestMove = this.getResultProperty(result, "bestmove");
-        if (bestMove) {
-          parsedResults.bestMove = bestMove;
-        }
-      }
-
-      if (result.startsWith("info")) {
-        const pv = this.getResultPv(result);
-        const multiPv = this.getResultProperty(result, "multipv");
-        const depth = this.getResultProperty(result, "depth");
-        if (!pv || !multiPv || !depth) continue;
-
-        if (
-          tempResults[multiPv] &&
-          parseInt(depth) < tempResults[multiPv].depth
-        ) {
-          continue;
-        }
-
-        const cp = this.getResultProperty(result, "cp");
-        const mate = this.getResultProperty(result, "mate");
-
-        tempResults[multiPv] = {
-          pv,
-          cp: cp ? parseInt(cp) : undefined,
-          mate: mate ? parseInt(mate) : undefined,
-          depth: parseInt(depth),
-          multiPv: parseInt(multiPv),
-        };
-      }
-    }
-
-    parsedResults.lines = Object.values(tempResults).sort(this.sortLines);
-
-    if (!whiteToPlay) {
-      parsedResults.lines = parsedResults.lines.map((line) => ({
-        ...line,
-        cp: line.cp ? -line.cp : line.cp,
-        mate: line.mate ? -line.mate : line.mate,
-      }));
-    }
-
-    return parsedResults;
-  }
-
-  private sortLines(a: LineEval, b: LineEval): number {
-    if (a.mate !== undefined && b.mate !== undefined) {
-      return a.mate - b.mate;
-    }
-
-    if (a.mate !== undefined) {
-      return -a.mate;
-    }
-
-    if (b.mate !== undefined) {
-      return b.mate;
-    }
-
-    return (b.cp ?? 0) - (a.cp ?? 0);
-  }
-
-  private getResultProperty(
-    result: string,
-    property: string
-  ): string | undefined {
-    const splitResult = result.split(" ");
-    const propertyIndex = splitResult.indexOf(property);
-
-    if (propertyIndex === -1 || propertyIndex + 1 >= splitResult.length) {
-      return undefined;
-    }
-
-    return splitResult[propertyIndex + 1];
-  }
-
-  private getResultPv(result: string): string[] | undefined {
-    const splitResult = result.split(" ");
-    const pvIndex = splitResult.indexOf("pv");
-
-    if (pvIndex === -1 || pvIndex + 1 >= splitResult.length) {
-      return undefined;
-    }
-
-    return splitResult.slice(pvIndex + 1);
-  }
 }

src/lib/helpers.ts

@@ -5,3 +5,37 @@ export const getPaddedMonth = (month: number) => {
 export const capitalize = (s: string) => {
   return s.charAt(0).toUpperCase() + s.slice(1);
 };
+
+export const ceilsNumber = (number: number, min: number, max: number) => {
+  if (number > max) return max;
+  if (number < min) return min;
+  return number;
+};
+
+export const getHarmonicMean = (array: number[]) => {
+  const sum = array.reduce((acc, curr) => acc + 1 / curr, 0);
+  return array.length / sum;
+};
+
+export const getStandardDeviation = (array: number[]) => {
+  const n = array.length;
+  const mean = array.reduce((a, b) => a + b) / n;
+  return Math.sqrt(
+    array.map((x) => Math.pow(x - mean, 2)).reduce((a, b) => a + b) / n
+  );
+};
+
+export const getWeightedMean = (array: number[], weights: number[]) => {
+  if (array.length > weights.length)
+    throw new Error("Weights array is too short");
+
+  const weightedSum = array.reduce(
+    (acc, curr, index) => acc + curr * weights[index],
+    0
+  );
+  const weightSum = weights
+    .slice(0, array.length)
+    .reduce((acc, curr) => acc + curr, 0);
+
+  return weightedSum / weightSum;
+};