lila/apps/api/src/services/gameService.test.ts

import { describe, it, expect, vi, beforeEach } from "vitest";
import type { GameRequest, AnswerSubmission } from "@lila/shared";

vi.mock("@lila/db", () => ({ getGameTerms: vi.fn(), getDistractors: vi.fn() }));

import { getGameTerms, getDistractors } from "@lila/db";
import { createGameSession, evaluateAnswer } from "./gameService.js";

const mockGetGameTerms = vi.mocked(getGameTerms);
const mockGetDistractors = vi.mocked(getDistractors);

const validRequest: GameRequest = {
  source_language: "en",
  target_language: "it",
  pos: "noun",
  difficulty: "easy",
  rounds: "3",
};

const fakeTerms = [
  { termId: "t1", sourceText: "dog", targetText: "cane", sourceGloss: null },
  { termId: "t2", sourceText: "cat", targetText: "gatto", sourceGloss: null },
  {
    termId: "t3",
    sourceText: "house",
    targetText: "casa",
    sourceGloss: "a building for living in",
  },
];

beforeEach(() => {
  vi.clearAllMocks();
  mockGetGameTerms.mockResolvedValue(fakeTerms);
  mockGetDistractors.mockResolvedValue(["wrong1", "wrong2", "wrong3"]);
});

describe("createGameSession", () => {
  it("returns a session with the correct number of questions", async () => {
    const session = await createGameSession(validRequest);

    expect(session.sessionId).toBeDefined();
    expect(session.questions).toHaveLength(3);
  });

  it("each question has exactly 4 options", async () => {
    const session = await createGameSession(validRequest);

    for (const question of session.questions) {
      expect(question.options).toHaveLength(4);
    }
  });

  it("each question has a unique questionId", async () => {
    const session = await createGameSession(validRequest);
    const ids = session.questions.map((q) => q.questionId);

    expect(new Set(ids).size).toBe(ids.length);
  });

  it("options have sequential optionIds 0-3", async () => {
    const session = await createGameSession(validRequest);

    for (const question of session.questions) {
      const optionIds = question.options.map((o) => o.optionId);
      expect(optionIds).toEqual([0, 1, 2, 3]);
    }
  });

  it("the correct answer is always among the options", async () => {
    const session = await createGameSession(validRequest);

    for (let i = 0; i < session.questions.length; i++) {
      const question = session.questions[i]!;
      const correctText = fakeTerms[i]!.targetText;
      const optionTexts = question.options.map((o) => o.text);

      expect(optionTexts).toContain(correctText);
    }
  });

  it("distractors are never the correct answer", async () => {
    const session = await createGameSession(validRequest);

    for (let i = 0; i < session.questions.length; i++) {
      const question = session.questions[i]!;
      const correctText = fakeTerms[i]!.targetText;
      const distractorTexts = question.options
        .map((o) => o.text)
        .filter((t) => t !== correctText);

      for (const text of distractorTexts) {
        expect(text).not.toBe(correctText);
      }
    }
  });

  it("sets the prompt from the source text", async () => {
    const session = await createGameSession(validRequest);

    expect(session.questions[0]!.prompt).toBe("dog");
    expect(session.questions[1]!.prompt).toBe("cat");
    expect(session.questions[2]!.prompt).toBe("house");
  });

  it("passes gloss through (null or string)", async () => {
    const session = await createGameSession(validRequest);

    expect(session.questions[0]!.gloss).toBeNull();
    expect(session.questions[2]!.gloss).toBe("a building for living in");
  });

  it("calls getGameTerms with the correct arguments", async () => {
    await createGameSession(validRequest);

    expect(mockGetGameTerms).toHaveBeenCalledWith(
      "en",
      "it",
      "noun",
      "easy",
      3,
    );
  });

  it("calls getDistractors once per question", async () => {
    await createGameSession(validRequest);

    expect(mockGetDistractors).toHaveBeenCalledTimes(3);
  });

  it("propagates unexpected errors from getGameTerms", async () => {
    mockGetGameTerms.mockRejectedValue(new Error("connection refused"));

    await expect(createGameSession(validRequest)).rejects.toThrow(
      "connection refused",
    );
  });
});

describe("evaluateAnswer", () => {
  it("returns isCorrect: true when the correct option is selected", async () => {
    const session = await createGameSession(validRequest);
    const question = session.questions[0]!;
    const correctText = fakeTerms[0]!.targetText;
    const correctOption = question.options.find((o) => o.text === correctText)!;

    const result = await evaluateAnswer({
      sessionId: session.sessionId,
      questionId: question.questionId,
      selectedOptionId: correctOption.optionId,
    });

    expect(result.isCorrect).toBe(true);
    expect(result.correctOptionId).toBe(correctOption.optionId);
    expect(result.selectedOptionId).toBe(correctOption.optionId);
  });

  it("returns isCorrect: false when a wrong option is selected", async () => {
    const session = await createGameSession(validRequest);
    const question = session.questions[0]!;
    const correctText = fakeTerms[0]!.targetText;
    const correctOption = question.options.find((o) => o.text === correctText)!;
    const wrongOption = question.options.find((o) => o.text !== correctText)!;

    const result = await evaluateAnswer({
      sessionId: session.sessionId,
      questionId: question.questionId,
      selectedOptionId: wrongOption.optionId,
    });

    expect(result.isCorrect).toBe(false);
    expect(result.correctOptionId).toBe(correctOption.optionId);
    expect(result.selectedOptionId).toBe(wrongOption.optionId);
  });

  it("throws NotFoundError for a non-existent session", async () => {
    const submission: AnswerSubmission = {
      sessionId: "00000000-0000-0000-0000-000000000000",
      questionId: "00000000-0000-0000-0000-000000000000",
      selectedOptionId: 0,
    };

    await expect(evaluateAnswer(submission)).rejects.toThrow(
      "Game session not found",
    );
  });

  it("throws NotFoundError for a non-existent question", async () => {
    const session = await createGameSession(validRequest);

    const submission: AnswerSubmission = {
      sessionId: session.sessionId,
      questionId: "00000000-0000-0000-0000-000000000000",
      selectedOptionId: 0,
    };

    await expect(evaluateAnswer(submission)).rejects.toThrow(
      "Question not found",
    );
  });
});