pixi-demo/tests/chase/chaseGenerator.test.ts

import { describe, expect, it } from "vitest";
import { shortestPath, shortestPathLength } from "../../src/stages/games/chase/logic/hexGraph";
import { generateChaseRound } from "../../src/stages/games/chase/logic/generator";
import { thiefHasWinningStrategy } from "../../src/stages/games/chase/logic/solvability";
import type { Difficulty, GameGraph } from "../../src/stages/games/chase/logic/types";

describe("chase round generator", () => {
  it("is deterministic for same seed and difficulty", () => {
    const options = { seed: 20260426, difficulty: "normal" as Difficulty };
    const roundA = generateChaseRound(options);
    const roundB = generateChaseRound(options);

    expect(roundA).toEqual(roundB);
  });

  it("matches golden snapshot for fixed seed", () => {
    const round = generateChaseRound({ seed: 424242, difficulty: "easy" });

    expect({
      seed: round.snapshot.seed,
      difficulty: round.snapshot.difficulty,
      thiefStartNodeId: round.snapshot.thiefStartNodeId,
      guardStartNodeId: round.snapshot.guardStartNodeId,
      thiefNodeId: round.snapshot.thiefNodeId,
      guardNodeId: round.snapshot.guardNodeId,
      exitNodeId: round.snapshot.exitNodeId,
      status: round.snapshot.status,
      hasEscapePath: round.meta.hasEscapePath,
      nodeCount: Object.keys(round.snapshot.graph.nodes).length,
      edgeCount: round.snapshot.graph.edgeList.length,
      firstFiveNodeIds: Object.keys(round.snapshot.graph.nodes).slice(0, 5),
    }).toMatchInlineSnapshot(`
      {
        "difficulty": "easy",
        "edgeCount": 25,
        "exitNodeId": "-2,0",
        "firstFiveNodeIds": [
          "0,0",
          "0,1",
          "0,-1",
          "-1,1",
          "-1,2",
        ],
        "guardNodeId": "-2,1",
        "guardStartNodeId": "-2,1",
        "hasEscapePath": true,
        "nodeCount": 24,
        "seed": 2654860011,
        "status": "playing",
        "thiefNodeId": "2,-1",
        "thiefStartNodeId": "2,-1",
      }
    `);
  });

  it("generates graph node count between 20 and 30", () => {
    const round = generateChaseRound({ seed: 11, difficulty: "normal" });
    const nodeCount = Object.keys(round.snapshot.graph.nodes).length;
    expect(nodeCount).toBeGreaterThanOrEqual(20);
    expect(nodeCount).toBeLessThanOrEqual(30);
  });

  it("ensures an escape path exists", () => {
    const round = generateChaseRound({ seed: 99, difficulty: "hard" });
    const pathLength = shortestPathLength(
      round.snapshot.graph,
      round.snapshot.thiefNodeId,
      round.snapshot.exitNodeId,
    );

    expect(round.meta.hasEscapePath).toBe(true);
    expect(pathLength).toBeGreaterThan(0);
    expect(pathLength).toBeLessThan(Infinity);
  });

  it("ensures thief and guard do not start on the same node", () => {
    const round = generateChaseRound({ seed: 123456, difficulty: "normal" });
    expect(round.snapshot.thiefStartNodeId).not.toBe(round.snapshot.guardStartNodeId);
  });

  it("stays playable and stable across many seeds", () => {
    for (let seed = 1; seed <= 60; seed += 1) {
      const round = generateChaseRound({ seed, difficulty: "normal" });
      const nodeCount = Object.keys(round.snapshot.graph.nodes).length;

      expect(nodeCount).toBeGreaterThanOrEqual(20);
      expect(nodeCount).toBeLessThanOrEqual(30);
      expect(round.meta.hasEscapePath).toBe(true);
      expect(round.snapshot.thiefStartNodeId).not.toBe(
        round.snapshot.guardStartNodeId,
      );
    }
  });

  it("places guard strictly between thief and exit on the canonical shortest path", () => {
    for (let seed = 1; seed <= 40; seed += 1) {
      for (const difficulty of ["easy", "normal", "hard"] as const) {
        const round = generateChaseRound({ seed, difficulty });
        const path = shortestPath(
          round.snapshot.graph,
          round.snapshot.thiefStartNodeId,
          round.snapshot.exitNodeId,
        );
        expect(path.length).toBeGreaterThanOrEqual(3);
        const inner = path.slice(1, -1);
        expect(inner).toContain(round.snapshot.guardStartNodeId);
        expect(round.meta.pathLength).toBeGreaterThanOrEqual(
          difficulty === "easy" ? 3 : difficulty === "hard" ? 6 : 4,
        );
      }
    }
  });

  it("throws after retry limit when all attempts are unplayable", () => {
    let attemptCount = 0;
    const unplayableStrategy = (seed: number, difficulty: Difficulty) => {
      attemptCount += 1;
      return {
        snapshot: {
          seed,
          difficulty,
          graph: { nodes: {}, edgeList: [] },
          thiefStartNodeId: "A",
          guardStartNodeId: "A",
          thiefNodeId: "A",
          guardNodeId: "A",
          exitNodeId: "A",
          status: "playing" as const,
        },
        meta: {
          hasEscapePath: false,
          pathLength: 0,
          attemptsUsed: 1,
        },
      };
    };

    expect(() =>
      generateChaseRound(
        { seed: 7, difficulty: "normal" },
        { generateAttempt: unplayableStrategy },
      ),
    ).toThrow("Unable to generate playable chase round within retry limit");
    expect(attemptCount).toBe(80);
  });

  it("rejects rounds that are unwinnable against optimal guard", () => {
    const trapGraph: GameGraph = {
      nodes: {
        L: { id: "L", q: 0, r: 0, neighbors: ["N"] },
        N: { id: "N", q: 1, r: 0, neighbors: ["L", "E"] },
        E: { id: "E", q: 2, r: 0, neighbors: ["N"] },
      },
      edgeList: [
        ["L", "N"],
        ["N", "E"],
      ],
    };

    expect(thiefHasWinningStrategy(trapGraph, "L", "N", "E")).toBe(false);

    let attemptCount = 0;
    const corridorTrap = (seed: number, difficulty: Difficulty) => {
      attemptCount += 1;
      return {
        snapshot: {
          seed,
          difficulty,
          graph: trapGraph,
          thiefStartNodeId: "L",
          guardStartNodeId: "N",
          thiefNodeId: "L",
          guardNodeId: "N",
          exitNodeId: "E",
          status: "playing" as const,
        },
        meta: {
          hasEscapePath: true,
          pathLength: 2,
          attemptsUsed: 1,
        },
      };
    };

    expect(() =>
      generateChaseRound({ seed: 1, difficulty: "normal" }, { generateAttempt: corridorTrap }),
    ).toThrow("Unable to generate playable chase round within retry limit");
    expect(attemptCount).toBe(80);
  });
});