implemented autoplay for O

src/backend/main/boardgame-handler.ts

@@ -2,11 +2,16 @@ import type { Request, Response } from "express";
 import { rewriteQueryParamsWith, safeGetQueryValue } from "../utils.ts";
 import { BoardgameState } from "../../shared/boardgame-state.ts";
 import { getBoardgameHtml } from "../components/boardgame.tsx";
-import { gamesRules } from "../../shared/rules.spec.ts";
+import { gamesRules } from "../../shared/rules.ts";
+import { getAllSolutions } from "../../shared/solver-cache.ts";
+import { CurrentOutcome, Player } from "../../shared/datatypes.ts";
+import { createOpponent } from "../../shared/opponent.ts";
 
 // Returns nothing if query parameter is uninitialized and a redirect was made,
 // or component if query parameter is initialized.
 export const handleBoardgame = (req: Request, res: Response, key: string) => {
+  const rules = gamesRules.tictactoe;
+
   const serializedState = safeGetQueryValue(req, key);
   const state = BoardgameState.fromSerialized(serializedState);
 
@@ -16,5 +21,16 @@ export const handleBoardgame = (req: Request, res: Response, key: string) => {
     return;
   }
 
-  return getBoardgameHtml(key, state, gamesRules.tictactoe);
+  if (state.board && state.currentPlayer === Player.O) {
+    const currentOutcome = rules.getBoardOutcome(state.board);
+    if (currentOutcome === CurrentOutcome.Undecided) {
+      const solutions = getAllSolutions(state.rows, state.columns, rules);
+      const nextMove = createOpponent(solutions).getNextMove(state.board, state.currentPlayer);
+      const newState = state.withMove(nextMove.row, nextMove.column);
+      rewriteQueryParamsWith(req, res, { [key]: newState.serialize() });
+      return;
+    }
+  }
+
+  return getBoardgameHtml(key, state, rules);
 };

src/shared/datatypes.ts

@@ -57,7 +57,7 @@ export type GameRules = {
 };
 
 export type Opponent = {
-  getNextMove(board: BoardType, currentPlayer: Player): BoardType;
+  getNextMove(board: BoardType, currentPlayer: Player): { row: number; column: number };
 };
 
 export const getExpectedOutcomeByCurrentOutcome = (

src/shared/opponent.spec.ts

@@ -1,6 +1,6 @@
 import t from "tap";
 import { Board } from "./board.ts";
-import { ExpectedOutcome, FinalOutcome, Player } from "./datatypes.ts";
+import { ExpectedOutcome, FinalOutcome, Player, getOccupiedStateByPlayer } from "./datatypes.ts";
 import { createOpponent } from "./opponent.ts";
 
 void t.test("createOpponent", async (t) => {
@@ -34,10 +34,10 @@ void t.test("createOpponent", async (t) => {
     currentPlayer: Player,
     expectedNextBoardSerialized: string,
   ) => {
-    t.equal(
+    const currentBoard = Board.fromSerialized(currentBoardSerialized);
-      opponent.getNextMove(Board.fromSerialized(currentBoardSerialized), currentPlayer).serialize(),
+    const nextMove = opponent.getNextMove(currentBoard, currentPlayer);
-      expectedNextBoardSerialized,
+    const nextBoard = currentBoard.with(nextMove.row, nextMove.column, getOccupiedStateByPlayer(currentPlayer));
-    );
+    t.equal(nextBoard.serialize(), expectedNextBoardSerialized);
   };
 
   checkNextMove("X_|__|__", Player.O, "X_|__|_O");

src/shared/opponent.ts

@@ -25,7 +25,7 @@ export const createOpponent = (outcomesByBoard: Map<string, ExpectedOutcome>): O
             nextExpectedOutcome.finalOutcome === currentExpectedOutcome.finalOutcome &&
             nextExpectedOutcome.movesLeft === currentExpectedOutcome.movesLeft - 1
           ) {
-            return nextBoard;
+            return { row, column };
           }
         }
       }

src/shared/solver-cache.ts

@@ -0,0 +1,20 @@
+import { ExpectedOutcome, GameRules } from "./datatypes.ts";
+import { computeAllSolutions } from "./solver.ts";
+
+const solverCache = new Map<GameRules, Map<string, Map<string, ExpectedOutcome>>>();
+
+export const getAllSolutions = (rows: number, columns: number, rules: GameRules) => {
+  if (!solverCache.has(rules)) {
+    solverCache.set(rules, new Map<string, Map<string, ExpectedOutcome>>());
+  }
+
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion -- we have just ensured that it exists.
+  const solverCacheForRules = solverCache.get(rules)!;
+  const dimensionsKey = `${rows}x${columns}`;
+  if (!solverCacheForRules.has(dimensionsKey)) {
+    solverCacheForRules.set(dimensionsKey, computeAllSolutions(rows, columns, rules));
+  }
+
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion -- we have just ensured that it exists.
+  return solverCacheForRules.get(dimensionsKey)!;
+};

src/shared/tictactoe.test.ts

@@ -1,7 +1,7 @@
 import t, { Test } from "tap";
 
 import { Board } from "./board.ts";
-import { ExpectedOutcome, FinalOutcome, Opponent, Player } from "./datatypes.ts";
+import { ExpectedOutcome, FinalOutcome, Opponent, Player, getOccupiedStateByPlayer } from "./datatypes.ts";
 import { createOpponent } from "./opponent.ts";
 import { computeAllSolutions } from "./solver.ts";
 import { rules } from "./tictactoe-rules.ts";
@@ -153,10 +153,10 @@ void t.test("createOpponent", async (t) => {
     currentPlayer: Player,
     expectedNextBoardSerialized: string,
   ) => {
-    t.equal(
+    const currentBoard = Board.fromSerialized(currentBoardSerialized);
-      opponent.getNextMove(Board.fromSerialized(currentBoardSerialized), currentPlayer).serialize(),
+    const nextMove = opponent.getNextMove(currentBoard, currentPlayer);
-      expectedNextBoardSerialized,
+    const nextBoard = currentBoard.with(nextMove.row, nextMove.column, getOccupiedStateByPlayer(currentPlayer));
-    );
+    t.equal(nextBoard.serialize(), expectedNextBoardSerialized);
   };
 
   void t.test("1x5 board", async (t) => {