Class FishInstaller

src/core/completions/installers/fish-installer.ts:11–162

 * Fish automatically loads completions from ~/.config/fish/completions/
 */
export class FishInstaller {
  private readonly homeDir: string;

  constructor(homeDir: string = os.homedir()) {
    this.homeDir = homeDir;
  }

  /**
   * Get the installation path for Fish completions
   *
   * @returns Installation path
   */
  getInstallationPath(): string {
    return path.join(this.homeDir, '.config', 'fish', 'completions', 'openspec.fish');
  }

  /**
   * Backup an existing completion file if it exists
   *
   * @param targetPath - Path to the file to backup
   * @returns Path to the backup file, or undefined if no backup was needed
   */
  async backupExistingFile(targetPath: string): Promise<string | undefined> {
    try {
      await fs.access(targetPath);
      // File exists, create a backup
      const timestamp = new Date().toISOString().replace(/[:.]/g, '-');
      const backupPath = `${targetPath}.backup-${timestamp}`;
      await fs.copyFile(targetPath, backupPath);
      return backupPath;
    } catch {
      // File doesn't exist, no backup needed
      return undefined;
    }
  }

  /**
   * Install the completion script
   *
   * @param completionScript - The completion script content to install
   * @returns Installation result with status and instructions
   */
  async install(completionScript: string): Promise<InstallationResult> {
    try {
      const targetPath = this.getInstallationPath();

      // Check if already installed with same content
      let isUpdate = false;
      try {
        const existingContent = await fs.readFile(targetPath, 'utf-8');
        if (existingContent === completionScript) {
          // Already installed and up to date
          return {
            success: true,
            installedPath: targetPath,
            message: 'Completion script is already installed (up to date)',
            instructions: [
              'The completion script is already installed and up to date.',