/**
 * Tests for persistAccountPool function
 * 
 * Issue #89: Multi-account login overwrites existing accounts
 * Root cause: loadAccounts() returning null is treated as "no accounts"
 * even when the file exists but couldn't be read (permissions, corruption, etc.)
 * 
 * @see https://github.com/NoeFabris/opencode-antigravity-auth/issues/89
 */

import { describe, expect, it, vi, beforeEach, afterEach } from "vitest";
import { promises as fs } from "node:fs";
import * as storageModule from "./storage";
import type { AccountStorageV4, AccountMetadataV3 } from "./storage";

vi.mock("proper-lockfile", () => ({
  default: {
    lock: vi.fn().mockResolvedValue(vi.fn().mockResolvedValue(undefined)),
  },
}));

vi.mock("node:fs", async () => {
  const actual = await vi.importActual<typeof import("node:fs")>("node:fs");
  return {
    ...actual,
    promises: {
      readFile: vi.fn(),
      writeFile: vi.fn(),
      mkdir: vi.fn().mockResolvedValue(undefined),
      access: vi.fn().mockResolvedValue(undefined),
      unlink: vi.fn(),
      rename: vi.fn().mockResolvedValue(undefined),
    },
  };
});

function createMockAccount(overrides: Partial<AccountMetadataV3> = {}): AccountMetadataV3 {
  return {
    email: "test@example.com",
    refreshToken: "test-refresh-token",
    projectId: "test-project-id",
    managedProjectId: "test-managed-project-id",
    addedAt: Date.now() - 10000,
    lastUsed: Date.now(),
    ...overrides,
  };
}

function createMockStorage(accounts: AccountMetadataV3[], activeIndex = 0): AccountStorageV4 {
  return {
    version: 4,
    accounts,
    activeIndex,
  };
}

describe("loadAccounts", () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  afterEach(() => {
    vi.restoreAllMocks();
  });

  describe("file not found (ENOENT)", () => {
    it("returns null when file does not exist", async () => {
      const error = new Error("ENOENT") as NodeJS.ErrnoException;
      error.code = "ENOENT";
      vi.mocked(fs.readFile).mockRejectedValue(error);

      const result = await storageModule.loadAccounts();

      expect(result).toBeNull();
    });
  });

  describe("file exists with valid data", () => {
    it("returns storage for valid V3 file", async () => {
      const mockStorage = createMockStorage([createMockAccount()]);
      vi.mocked(fs.readFile).mockResolvedValue(JSON.stringify(mockStorage));

      const result = await storageModule.loadAccounts();

      expect(result).not.toBeNull();
      expect(result?.version).toBe(4);
      expect(result?.accounts).toHaveLength(1);
    });

    it("returns storage with multiple accounts", async () => {
      const mockStorage = createMockStorage([
        createMockAccount({ email: "user1@example.com", refreshToken: "token1" }),
        createMockAccount({ email: "user2@example.com", refreshToken: "token2" }),
      ]);
      vi.mocked(fs.readFile).mockResolvedValue(JSON.stringify(mockStorage));

      const result = await storageModule.loadAccounts();

      expect(result?.accounts).toHaveLength(2);
      expect(result?.accounts[0]?.email).toBe("user1@example.com");
      expect(result?.accounts[1]?.email).toBe("user2@example.com");
    });

    it("preserves activeIndex from storage", async () => {
      const mockStorage = createMockStorage([
        createMockAccount({ email: "user1@example.com" }),
        createMockAccount({ email: "user2@example.com" }),
      ], 1);
      vi.mocked(fs.readFile).mockResolvedValue(JSON.stringify(mockStorage));

      const result = await storageModule.loadAccounts();

      expect(result?.activeIndex).toBe(1);
    });
  });

  describe("error handling - THE BUG (Issue #89)", () => {
    /**
     * THIS IS THE BUG: loadAccounts returns null for ANY error, not just ENOENT.
     * The caller (persistAccountPool) cannot distinguish between:
     * - File doesn't exist (safe to create new)
     * - File exists but couldn't be read (DANGEROUS - would overwrite!)
     */

    it("returns null on permission denied (EACCES)", async () => {
      const error = new Error("EACCES") as NodeJS.ErrnoException;
      error.code = "EACCES";
      vi.mocked(fs.readFile).mockRejectedValue(error);

      const result = await storageModule.loadAccounts();

      expect(result).toBeNull();
    });

    it("returns null on JSON parse error", async () => {
      vi.mocked(fs.readFile).mockResolvedValue("{ invalid json }}}");

      const result = await storageModule.loadAccounts();

      expect(result).toBeNull();
    });

    it("returns null on invalid storage format", async () => {
      vi.mocked(fs.readFile).mockResolvedValue(JSON.stringify({ version: 4, notAccounts: [] }));

      const result = await storageModule.loadAccounts();

      expect(result).toBeNull();
    });

    it("returns null on unknown version", async () => {
      vi.mocked(fs.readFile).mockResolvedValue(JSON.stringify({ version: 999, accounts: [] }));

      const result = await storageModule.loadAccounts();

      expect(result).toBeNull();
    });
  });

  describe("migration", () => {
    it("migrates V2 to V3 successfully", async () => {
      const v2Storage = {
        version: 2,
        accounts: [
          {
            refreshToken: "token1",
            addedAt: Date.now() - 10000,
            lastUsed: Date.now(),
          },
        ],
        activeIndex: 0,
      };
      vi.mocked(fs.readFile).mockResolvedValue(JSON.stringify(v2Storage));
      vi.mocked(fs.writeFile).mockResolvedValue(undefined);

      const result = await storageModule.loadAccounts();

      expect(result?.version).toBe(4);
      expect(result?.accounts).toHaveLength(1);
    });
  });
});

describe("saveAccounts", () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  it("saves valid storage to disk", async () => {
    vi.mocked(fs.writeFile).mockResolvedValue(undefined);
    vi.mocked(fs.mkdir).mockResolvedValue(undefined);

    const storage = createMockStorage([createMockAccount()]);
    await storageModule.saveAccounts(storage);

    expect(fs.writeFile).toHaveBeenCalledTimes(1);
    const writtenContent = vi.mocked(fs.writeFile).mock.calls[0]?.[1];
    expect(writtenContent).toBeDefined();
    const parsed = JSON.parse(writtenContent as string);
    expect(parsed.version).toBe(4);
    expect(parsed.accounts).toHaveLength(1);
  });
});

/**
 * Tests for the expected behavior of persistAccountPool
 * 
 * NOTE: persistAccountPool is currently a private function in plugin.ts.
 * These tests document the EXPECTED behavior after the fix.
 * To run these tests, persistAccountPool should be exported.
 */
describe("persistAccountPool behavior (Issue #89)", () => {
  beforeEach(() => {
    vi.clearAllMocks();
    vi.useFakeTimers();
    vi.setSystemTime(new Date("2026-01-01T12:00:00Z"));
  });

  afterEach(() => {
    vi.useRealTimers();
  });

  describe("merging behavior (replaceAll=false)", () => {
    it.todo("merges new account with existing accounts");
    
    it.todo("deduplicates by email, keeping the newest token");
    
    it.todo("deduplicates by refresh token when email not available");
    
    it.todo("preserves activeIndex when adding new accounts");
    
    it.todo("updates lastUsed timestamp for existing accounts");
  });

  describe("fresh start behavior (replaceAll=true)", () => {
    it.todo("replaces all existing accounts with new ones");
    
    it.todo("resets activeIndex to 0");
    
    it.todo("ignores existing accounts file");
  });

  describe("THE BUG: error handling when loadAccounts fails (Issue #89)", () => {
    /**
     * Current buggy behavior:
     * 1. User has accounts saved in ~/.config/opencode/antigravity-accounts.json
     * 2. loadAccounts() fails (permission error, JSON parse error, etc.)
     * 3. loadAccounts() returns null
     * 4. persistAccountPool treats null as "no accounts exist"
     * 5. New account REPLACES existing accounts instead of merging
     * 
     * Expected behavior after fix:
     * 1. loadAccounts() should distinguish ENOENT from other errors
     * 2. persistAccountPool should throw/warn when file exists but can't be read
     * 3. User should be prompted about potential data loss
     */

    it.todo("should NOT overwrite accounts when loadAccounts returns null due to permission error");
    
    it.todo("should throw error when file exists but cannot be read");
    
    it.todo("should prompt user when existing accounts may be lost");
    
    it.todo("should only treat ENOENT as 'safe to create new file'");
  });
});

/**
 * Tests for TUI flow integration (Issue #89)
 * 
 * The user's logs showed they went through TUI flow, not CLI flow.
 * TUI flow calls persistAccountPool with replaceAll=false,
 * which should merge accounts but doesn't when loadAccounts fails.
 */
describe("TUI flow integration (Issue #89)", () => {
  describe("account persistence after OAuth", () => {
    it.todo("should merge new account with existing accounts in TUI flow");
    
    it.todo("should show warning when existing accounts cannot be loaded");
    
    it.todo("should ask user for confirmation before potentially overwriting accounts");
  });

  describe("authorize function behavior", () => {
    it.todo("TUI flow (inputs falsy) should check for existing accounts");
    
    it.todo("should handle loadAccounts returning null gracefully");
  });
});

/**
 * Regression tests to ensure the fix doesn't break normal operation
 */
describe("regression tests", () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  describe("first-time user experience", () => {
    it("should work correctly when no accounts file exists (ENOENT)", async () => {
      const error = new Error("ENOENT") as NodeJS.ErrnoException;
      error.code = "ENOENT";
      vi.mocked(fs.readFile).mockRejectedValue(error);

      const result = await storageModule.loadAccounts();
      expect(result).toBeNull();

      vi.mocked(fs.writeFile).mockResolvedValue(undefined);
      vi.mocked(fs.mkdir).mockResolvedValue(undefined);

      const newStorage = createMockStorage([createMockAccount()]);
      await expect(storageModule.saveAccounts(newStorage)).resolves.not.toThrow();
    });
  });

  describe("normal multi-account workflow", () => {
    it("should load existing accounts correctly", async () => {
      const existingStorage = createMockStorage([
        createMockAccount({ email: "existing@example.com" }),
      ]);
      vi.mocked(fs.readFile).mockResolvedValue(JSON.stringify(existingStorage));

      const result = await storageModule.loadAccounts();

      expect(result).not.toBeNull();
      expect(result?.accounts).toHaveLength(1);
      expect(result?.accounts[0]?.email).toBe("existing@example.com");
    });

  it("should preserve all accounts when saving", async () => {
    const enoent = new Error("ENOENT") as NodeJS.ErrnoException;
    enoent.code = "ENOENT";
    vi.mocked(fs.readFile).mockRejectedValue(enoent);
    vi.mocked(fs.writeFile).mockResolvedValue(undefined);
    vi.mocked(fs.mkdir).mockResolvedValue(undefined);

    const storage = createMockStorage([
        createMockAccount({ email: "user1@example.com", refreshToken: "token1" }),
        createMockAccount({ email: "user2@example.com", refreshToken: "token2" }),
        createMockAccount({ email: "user3@example.com", refreshToken: "token3" }),
      ]);

      await storageModule.saveAccounts(storage);

      expect(fs.writeFile).toHaveBeenCalledTimes(2);

      const tmpWriteCall = vi.mocked(fs.writeFile).mock.calls.find(
        (call) => (call[0] as string).includes(".tmp")
      );
      expect(tmpWriteCall).toBeDefined();
      const parsed = JSON.parse(tmpWriteCall![1] as string);
      expect(parsed.accounts).toHaveLength(3);

      const gitignoreWriteCall = vi.mocked(fs.writeFile).mock.calls.find(
        (call) => (call[0] as string).includes(".gitignore")
      );
      expect(gitignoreWriteCall).toBeDefined();
    });
  });
});

/**
 * Proposed fix validation tests
 * 
 * These tests validate enhanced error handling behavior.
 */
describe("proposed fix validation", () => {
  describe("loadAccounts should distinguish error types", () => {
    it.todo("should return { error: 'ENOENT' } when file doesn't exist");
    it.todo("should return { error: 'PERMISSION_DENIED' } on EACCES");
    it.todo("should return { error: 'PARSE_ERROR' } on invalid JSON");
    it.todo("should return { error: 'INVALID_FORMAT' } on schema mismatch");
  });

  describe("persistAccountPool should handle errors safely", () => {
    it.todo("should throw AccountFileUnreadableError when file exists but can't be read");
    it.todo("should include recovery instructions in error message");
  });

  describe("user prompts for data safety", () => {
    it.todo("should prompt user when accounts file exists but is unreadable");
    it.todo("should offer options: (r)etry, (b)ackup and continue, (a)bort");
  });
});