/*
 * Copyright (C)  2022 Kristóf Marussy <kristof@marussy.com>
 *
 * This file is part of Sophie.
 *
 * Sophie is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * SPDX-License-Identifier: AGPL-3.0-only
 */

import {
  chmod,
  mkdir,
  mkdtemp,
  readFile,
  rename,
  rm,
  stat,
  utimes,
  writeFile,
} from 'node:fs/promises';
import { platform, tmpdir, userInfo } from 'node:os';
import path from 'node:path';

import { jest } from '@jest/globals';
import { testIf } from '@sophie/test-utils';
import { mocked } from 'jest-mock';

import Disposer from '../../../../utils/Disposer.js';
import ConfigFile, { CONFIG_FILE_NAME } from '../ConfigFile.js';

const CONFIG_CHANGE_DEBOUNCE_MS = 10;

let filesystemDelay = 100;
let realSetTimeout: typeof setTimeout;
let userDataDir: string | undefined;
let configFilePath: string;
let repository: ConfigFile;

async function realDelay(ms: number): Promise<void> {
  return new Promise<void>((resolve) => {
    realSetTimeout(() => resolve(), ms);
  });
}

/**
 * Wait for a short (real-time) delay to let node be notified of file changes.
 *
 * Use the `SOPHIE_INTEG_TEST_DELAY` environmental variable to customize the delay
 * (e.g., quicker test execution on faster computers or longer wait time in CI).
 * The default delay is 100 ms, but as little as 10 ms might be enough, depending on your system.
 *
 * @param ms The time that should elapse after noticing the filesystem change.
 * @returns A promise that resolves in a `filesystemDelay` ms.
 */
async function catchUpWithFilesystem(
  ms = CONFIG_CHANGE_DEBOUNCE_MS,
): Promise<void> {
  await realDelay(filesystemDelay);
  jest.advanceTimersByTime(ms);
  // Some extra real time is needed after advancing the timer to make sure the callback runs.
  await realDelay(Math.max(filesystemDelay / 10, 1));
}

beforeAll(() => {
  const delayEnv = process.env.SOPHIE_INTEG_TEST_DELAY;
  if (delayEnv !== undefined) {
    filesystemDelay = Number.parseInt(delayEnv, 10);
  }
  jest.useRealTimers();
  // Save the real implementation of `setTimeout` before we mock it.
  realSetTimeout = setTimeout;
  jest.useFakeTimers();
});

beforeEach(async () => {
  try {
    userDataDir = await mkdtemp(path.join(tmpdir(), 'sophie-configFile-'));
    configFilePath = path.join(userDataDir, CONFIG_FILE_NAME);
    repository = new ConfigFile(
      userDataDir,
      CONFIG_FILE_NAME,
      CONFIG_CHANGE_DEBOUNCE_MS,
    );
  } catch (error) {
    userDataDir = undefined;
    throw error;
  }
});

afterEach(async () => {
  jest.clearAllTimers();
  if (userDataDir === undefined) {
    return;
  }
  if (!userDataDir.startsWith(tmpdir())) {
    throw new Error(
      `Refusing to delete directory ${userDataDir} outside of tmp directory`,
    );
  }
  await rm(userDataDir, {
    force: true,
    recursive: true,
  });
  userDataDir = undefined;
});

describe('readConfig', () => {
  test('returns false when the config file is not found', async () => {
    const result = await repository.readConfig();
    expect(result.found).toBe(false);
  });

  test('reads the contents of the config file if found', async () => {
    await writeFile(configFilePath, 'Hello World!', 'utf8');
    const result = await repository.readConfig();
    expect(result.found).toBe(true);
    expect(result).toHaveProperty('contents', 'Hello World!');
  });

  test('throws an error if the config file cannot be read', async () => {
    await mkdir(configFilePath);
    await expect(repository.readConfig()).rejects.toThrow();
  });
});

describe('writeConfig', () => {
  test('writes the config file', async () => {
    await repository.writeConfig('Hi Mars!');
    const contents = await readFile(configFilePath, 'utf8');
    expect(contents).toBe('Hi Mars!');
  });

  test('overwrites the config file', async () => {
    await writeFile(configFilePath, 'Hello World!', 'utf8');
    await repository.writeConfig('Hi Mars!');
    const contents = await readFile(configFilePath, 'utf8');
    expect(contents).toBe('Hi Mars!');
  });

  test('throws an error if the config file cannot be written', async () => {
    await mkdir(configFilePath);
    await expect(repository.writeConfig('Hi Mars!')).rejects.toThrow();
  });

  test('throws an error when called reentrantly', async () => {
    const promise = repository.writeConfig('Hello World!');
    try {
      await expect(repository.writeConfig('Hi Mars!')).rejects.toThrow();
    } finally {
      await promise;
    }
  });
});

describe('watchConfig', () => {
  let callback: () => Promise<void>;
  let watcher: Disposer | undefined;

  beforeEach(() => {
    callback = jest.fn(() => Promise.resolve());
  });

  afterEach(() => {
    if (watcher !== undefined) {
      // Make sure we dispose the watcher.
      watcher();
    }
  });

  describe('when the config file does not exist', () => {
    beforeEach(() => {
      watcher = repository.watchConfig(callback);
    });

    test('notifies when the config file is created externally', async () => {
      await writeFile(configFilePath, 'Hello World!', 'utf8');
      await catchUpWithFilesystem();
      expect(callback).toHaveBeenCalled();
    });

    test('does not notify when the config file is created by the repository', async () => {
      await repository.writeConfig('Hello World!');
      await catchUpWithFilesystem();
      expect(callback).not.toHaveBeenCalled();
    });
  });

  describe('when the config file already exists', () => {
    beforeEach(async () => {
      await writeFile(configFilePath, 'Hello World!', 'utf8');
      watcher = repository.watchConfig(callback);
    });

    test('notifies when the config file is updated externally', async () => {
      await writeFile(configFilePath, 'Hi Mars!', 'utf8');
      await catchUpWithFilesystem();
      expect(callback).toHaveBeenCalled();
    });

    test('does not notify when the config file is created by the repository', async () => {
      await repository.writeConfig('Hi Mars!');
      await catchUpWithFilesystem();
      expect(callback).not.toHaveBeenCalled();
    });

    test('debounces changes to the config file', async () => {
      await writeFile(configFilePath, 'Hi Mars!', 'utf8');
      await catchUpWithFilesystem(5);
      expect(callback).not.toHaveBeenCalled();

      await writeFile(configFilePath, 'Hi Mars!', 'utf8');
      await catchUpWithFilesystem();
      expect(callback).toHaveBeenCalledTimes(1);
    });

    test('handles the config file being deleted', async () => {
      await rm(configFilePath);
      await catchUpWithFilesystem();
      expect(callback).not.toHaveBeenCalled();

      await writeFile(configFilePath, 'Hello World!', 'utf8');
      await catchUpWithFilesystem();
      expect(callback).toHaveBeenCalled();
    });

    test('handles the config file being renamed', async () => {
      const renamedPath = `${configFilePath}.renamed`;

      await rename(configFilePath, renamedPath);
      await catchUpWithFilesystem();
      expect(callback).not.toHaveBeenCalled();

      await writeFile(renamedPath, 'Hello World!', 'utf8');
      await catchUpWithFilesystem();
      expect(callback).not.toHaveBeenCalled();

      await writeFile(configFilePath, 'Hello World!', 'utf8');
      await catchUpWithFilesystem();
      expect(callback).toHaveBeenCalled();
    });

    // We can only cause a filesystem error by changing permissions if we run on a POSIX-like
    // system and we aren't root (i.e., not in CI).
    testIf(platform() !== 'win32' && userInfo().uid !== 0)(
      'handles other filesystem errors',
      async () => {
        const { mode } = await stat(userDataDir!);
        await writeFile(configFilePath, 'Hi Mars!', 'utf8');
        // Remove permission to force a filesystem error.
        // eslint-disable-next-line no-bitwise -- Compute reduced permissions.
        await chmod(userDataDir!, mode & 0o666);
        try {
          await catchUpWithFilesystem();
          expect(callback).not.toHaveBeenCalled();
        } finally {
          await chmod(userDataDir!, mode);
        }
      },
    );

    test('does not notify when the modification date is prior to the last write', async () => {
      await repository.writeConfig('Hello World!');
      const date = new Date(Date.now() - 3_600_000);
      await utimes(configFilePath, date, date);
      await catchUpWithFilesystem();
      expect(callback).not.toHaveBeenCalled();
    });

    test('handles callback errors', async () => {
      mocked(callback).mockRejectedValue(new Error('Test error'));
      await writeFile(configFilePath, 'Hi Mars!', 'utf8');
      await catchUpWithFilesystem();
      // This test would fail an unhandled promise rejection error if `ConfigFile`
      // did not handle the rejection properly.
      expect(callback).toHaveBeenCalled();
    });
  });
});