fix(chase): restore snapshot state shape and retry semantics

Made-with: Cursor

src/game/chase/model.ts

@@ -9,17 +9,14 @@ import type { Difficulty, NodeId } from "./types";
 
 type GameStatus = "playing" | "win" | "lose";
 
-interface ChaseGameState {
-  seed: number;
-  difficulty: Difficulty;
+type ModelSnapshot = Omit<ChaseRound["snapshot"], "status"> & {
   status: GameStatus;
+};
+
+interface ChaseGameState {
+  snapshot: ModelSnapshot;
   winCount: number;
-  thiefNodeId: NodeId;
-  guardNodeId: NodeId;
-  thiefStartNodeId: NodeId;
-  guardStartNodeId: NodeId;
-  exitNodeId: NodeId;
-  graph: ChaseRound["snapshot"]["graph"];
+  turn: number;
 }
 
 interface ChaseGameModelOptions {
@@ -34,25 +31,26 @@ const GUARD_SHORTEST_RATE: Record<Difficulty, number> = {
 
 function cloneRound(round: ChaseRound): ChaseGameState {
   return {
-    seed: round.snapshot.seed,
-    difficulty: round.snapshot.difficulty,
-    status: round.snapshot.status,
+    snapshot: {
+      ...round.snapshot,
+      status: "playing",
+    },
     winCount: 0,
-    thiefNodeId: round.snapshot.thiefNodeId,
-    guardNodeId: round.snapshot.guardNodeId,
-    thiefStartNodeId: round.snapshot.thiefStartNodeId,
-    guardStartNodeId: round.snapshot.guardStartNodeId,
-    exitNodeId: round.snapshot.exitNodeId,
-    graph: round.snapshot.graph,
+    turn: 0,
   };
 }
 
 export class ChaseGameModel {
   private state: ChaseGameState;
+  private initialSnapshot: ModelSnapshot;
   private random: () => number;
 
   private constructor(state: ChaseGameState, random: () => number) {
     this.state = state;
+    this.initialSnapshot = {
+      ...state.snapshot,
+      graph: state.snapshot.graph,
+    };
     this.random = random;
   }
 
@@ -62,29 +60,32 @@ export class ChaseGameModel {
   ): ChaseGameModel {
     const round = generateChaseRound(input);
     const state = cloneRound(round);
-    const rng = options.random ?? createRng(normalizeSeed(state.seed));
+    const rng = options.random ?? createRng(normalizeSeed(state.snapshot.seed));
     return new ChaseGameModel(state, rng);
   }
 
   getState(): ChaseGameState {
-    return { ...this.state };
+    return {
+      ...this.state,
+      snapshot: { ...this.state.snapshot },
+    };
   }
 
   getAvailableMoves(): NodeId[] {
-    if (this.state.status !== "playing") {
+    if (this.state.snapshot.status !== "playing") {
       return [];
     }
 
-    const node = this.state.graph.nodes[this.state.thiefNodeId];
+    const node = this.state.snapshot.graph.nodes[this.state.snapshot.thiefNodeId];
     if (!node) {
       return [];
     }
 
-    return node.neighbors.filter((id) => id !== this.state.guardNodeId);
+    return node.neighbors.filter((id) => id !== this.state.snapshot.guardNodeId);
   }
 
   moveThief(target: NodeId): ChaseGameState {
-    if (this.state.status !== "playing") {
+    if (this.state.snapshot.status !== "playing") {
       return this.getState();
     }
 
@@ -93,43 +94,55 @@ export class ChaseGameModel {
       return this.getState();
     }
 
-    this.state.thiefNodeId = target;
-    if (this.state.thiefNodeId === this.state.exitNodeId) {
-      this.state.status = "win";
+    this.state.turn += 1;
+    this.state.snapshot.thiefNodeId = target;
+    if (this.state.snapshot.thiefNodeId === this.state.snapshot.exitNodeId) {
+      this.state.snapshot.status = "win";
       this.state.winCount += 1;
       return this.getState();
     }
 
     this.moveGuardOneStep();
 
-    if (this.state.guardNodeId === this.state.thiefNodeId) {
-      this.state.status = "lose";
+    if (this.state.snapshot.guardNodeId === this.state.snapshot.thiefNodeId) {
+      this.state.snapshot.status = "lose";
       return this.getState();
     }
 
     if (this.getAvailableMoves().length === 0) {
-      this.state.status = "lose";
+      this.state.snapshot.status = "lose";
     }
 
     return this.getState();
   }
 
   retryRound(): ChaseGameState {
-    return this.newRound(this.state.seed, this.state.difficulty);
+    const winCount = this.state.winCount;
+    this.state = {
+      snapshot: {
+        ...this.initialSnapshot,
+        graph: this.initialSnapshot.graph,
+      },
+      winCount,
+      turn: 0,
+    };
+    return this.getState();
   }
 
   newRound(seed: number | string, difficulty: Difficulty): ChaseGameState {
     const round = generateChaseRound({ seed, difficulty });
     const winCount = this.state.winCount;
-    this.state = {
-      ...cloneRound(round),
-      winCount,
+    const newState = cloneRound(round);
+    this.state = { ...newState, winCount };
+    this.initialSnapshot = {
+      ...newState.snapshot,
+      graph: newState.snapshot.graph,
     };
     return this.getState();
   }
 
   private moveGuardOneStep(): void {
-    const guardNode = this.state.graph.nodes[this.state.guardNodeId];
+    const guardNode = this.state.snapshot.graph.nodes[this.state.snapshot.guardNodeId];
     if (!guardNode || guardNode.neighbors.length === 0) {
       return;
     }
@@ -137,9 +150,9 @@ export class ChaseGameModel {
     const movesWithDistance = guardNode.neighbors.map((neighborId) => ({
       nodeId: neighborId,
       distance: shortestPathLength(
-        this.state.graph,
+        this.state.snapshot.graph,
         neighborId,
-        this.state.thiefNodeId,
+        this.state.snapshot.thiefNodeId,
       ),
     }));
 
@@ -153,13 +166,13 @@ export class ChaseGameModel {
     const shortestMoves = finiteMoves.filter((item) => item.distance === shortestDistance);
     const nonShortestMoves = finiteMoves.filter((item) => item.distance !== shortestDistance);
 
-    const shortestRate = GUARD_SHORTEST_RATE[this.state.difficulty];
+    const shortestRate = GUARD_SHORTEST_RATE[this.state.snapshot.difficulty];
     let nextMove = shortestMoves[0];
     if (shortestRate < 1 && this.random() > shortestRate && nonShortestMoves.length > 0) {
       const idx = Math.floor(this.random() * nonShortestMoves.length);
       nextMove = nonShortestMoves[idx];
     }
 
-    this.state.guardNodeId = nextMove.nodeId;
+    this.state.snapshot.guardNodeId = nextMove.nodeId;
   }
 }

tests/chase/chaseModel.test.ts

@@ -58,12 +58,13 @@ describe("chase game model", () => {
     });
 
     const state = model.getState();
-    expect(state.seed).toBe(123);
-    expect(state.difficulty).toBe("normal");
-    expect(state.status).toBe("playing");
-    expect(state.thiefNodeId).toBe("B");
-    expect(state.guardNodeId).toBe("D");
-    expect(state.exitNodeId).toBe("C");
+    expect(state.snapshot.seed).toBe(123);
+    expect(state.snapshot.difficulty).toBe("normal");
+    expect(state.snapshot.status).toBe("playing");
+    expect(state.snapshot.thiefNodeId).toBe("B");
+    expect(state.snapshot.guardNodeId).toBe("D");
+    expect(state.snapshot.exitNodeId).toBe("C");
+    expect(state.turn).toBe(0);
     expect(model.getAvailableMoves()).toEqual(["A", "C"]);
   });
 
@@ -73,9 +74,10 @@ describe("chase game model", () => {
 
     model.moveThief("C");
     const state = model.getState();
-    expect(state.status).toBe("win");
+    expect(state.snapshot.status).toBe("win");
     expect(state.winCount).toBe(1);
-    expect(state.thiefNodeId).toBe("C");
+    expect(state.snapshot.thiefNodeId).toBe("C");
+    expect(state.turn).toBe(1);
   });
 
   it("guard moves after thief and can cause lose by capture", () => {
@@ -95,9 +97,10 @@ describe("chase game model", () => {
     model.moveThief("B");
 
     const state = model.getState();
-    expect(state.guardNodeId).toBe("B");
-    expect(state.thiefNodeId).toBe("B");
-    expect(state.status).toBe("lose");
+    expect(state.snapshot.guardNodeId).toBe("B");
+    expect(state.snapshot.thiefNodeId).toBe("B");
+    expect(state.snapshot.status).toBe("lose");
+    expect(state.turn).toBe(1);
   });
 
   it("loses when thief has no legal move after guard turn", () => {
@@ -129,29 +132,26 @@ describe("chase game model", () => {
     const model = ChaseGameModel.createWithSeed({ seed: 33, difficulty: "normal" });
     model.moveThief("B");
     const state = model.getState();
-    expect(state.status).toBe("lose");
+    expect(state.snapshot.status).toBe("lose");
     expect(model.getAvailableMoves()).toEqual([]);
+    expect(state.turn).toBe(1);
   });
 
-  it("retryRound regenerates same seed/difficulty but keeps winCount", () => {
-    mockedGenerateChaseRound
-      .mockReturnValueOnce(makeRound(44, "easy"))
-      .mockReturnValueOnce({
-        ...makeRound(44, "easy"),
-        snapshot: { ...makeRound(44, "easy").snapshot, thiefNodeId: "A" },
-      });
+  it("retryRound restores the same initial round snapshot and keeps winCount", () => {
+    mockedGenerateChaseRound.mockReturnValueOnce(makeRound(44, "easy"));
 
     const model = ChaseGameModel.createWithSeed({ seed: 44, difficulty: "easy" });
+    const initialState = model.getState();
     model.moveThief("C");
     expect(model.getState().winCount).toBe(1);
 
     model.retryRound();
     const state = model.getState();
-    expect(state.seed).toBe(44);
-    expect(state.difficulty).toBe("easy");
-    expect(state.thiefNodeId).toBe("A");
-    expect(state.status).toBe("playing");
+    expect(state.snapshot).toEqual(initialState.snapshot);
+    expect(state.snapshot.status).toBe("playing");
     expect(state.winCount).toBe(1);
+    expect(state.turn).toBe(0);
+    expect(mockedGenerateChaseRound).toHaveBeenCalledTimes(1);
   });
 
   it("newRound switches seed/difficulty and keeps winCount", () => {
@@ -165,10 +165,11 @@ describe("chase game model", () => {
 
     model.newRound(99, "hard");
     const state = model.getState();
-    expect(state.seed).toBe(99);
-    expect(state.difficulty).toBe("hard");
-    expect(state.status).toBe("playing");
+    expect(state.snapshot.seed).toBe(99);
+    expect(state.snapshot.difficulty).toBe("hard");
+    expect(state.snapshot.status).toBe("playing");
     expect(state.winCount).toBe(1);
+    expect(state.turn).toBe(0);
   });
 
   it("guard strategy follows difficulty probability rule", () => {
@@ -207,7 +208,7 @@ describe("chase game model", () => {
       { random: () => 0.99 },
     );
     hardModel.moveThief("C");
-    expect(hardModel.getState().guardNodeId).toBe("C");
+    expect(hardModel.getState().snapshot.guardNodeId).toBe("C");
 
     mockedGenerateChaseRound.mockReturnValue({
       ...baseRound,
@@ -223,6 +224,6 @@ describe("chase game model", () => {
       { random: () => 0.95 },
     );
     easyModel.moveThief("C");
-    expect(easyModel.getState().guardNodeId).toBe("E");
+    expect(easyModel.getState().snapshot.guardNodeId).toBe("E");
   });
 });