import * as plugins from './plugins.js';
const __dirname = plugins.path.dirname(plugins.url.fileURLToPath(import.meta.url));

export interface IRunOptions {
  cwd?: string;
}

export interface ISpawnOptions {
  /** Working directory for the child process */
  cwd?: string;

  /** Environment variables (merged with parent's env) */
  env?: Record<string, string>;

  /** Additional CLI arguments to pass to the script */
  args?: string[];

  /**
   * Stdio configuration
   * - 'pipe': Create pipes for stdin/stdout/stderr (default)
   * - 'inherit': Use parent's stdio
   * - Array: Custom configuration per stream
   */
  stdio?: 'pipe' | 'inherit' | ['pipe' | 'inherit' | 'ignore', 'pipe' | 'inherit' | 'ignore', 'pipe' | 'inherit' | 'ignore'];

  /**
   * Optional timeout in milliseconds
   * If provided, process is automatically killed after timeout
   */
  timeout?: number;

  /**
   * AbortSignal for cancellation support
   * Allows external cancellation of the process
   */
  signal?: AbortSignal;
}

export interface ITsrunChildProcess {
  /** Direct access to Node's ChildProcess object */
  childProcess: plugins.ChildProcess;

  /** Readable stream for stdout (null if stdio is 'inherit') */
  stdout: plugins.Readable | null;

  /** Readable stream for stderr (null if stdio is 'inherit') */
  stderr: plugins.Readable | null;

  /** Promise that resolves with the exit code when process ends */
  exitCode: Promise<number>;

  /**
   * Send signal to process
   * Returns true if signal was sent successfully
   */
  kill(signal?: NodeJS.Signals): boolean;

  /**
   * Gracefully terminate the process
   * Tries SIGTERM first, waits 5s, then SIGKILL if still running
   * Returns a promise that resolves when process is terminated
   */
  terminate(): Promise<void>;
}

export const runPath = async (pathArg: string, fromFileUrl?: string, options?: IRunOptions) => {
  pathArg = fromFileUrl
    ? plugins.path.join(plugins.path.dirname(plugins.url.fileURLToPath(fromFileUrl)), pathArg)
    : pathArg;
  await runCli(pathArg, options);
};

export const runCli = async (pathArg?: string, options?: IRunOptions) => {
  // CRITICAL: Branch BEFORE splicing argv to avoid corruption
  if (options?.cwd) {
    return runInChildProcess(pathArg, options.cwd);
  }

  // Existing in-process execution
  // contents of argv array
  // process.argv[0] -> node Executable
  // process.argv[1] -> tsrun executable
  const relativePathToTsFile = pathArg ? pathArg : process.argv[2];
  const absolutePathToTsFile = plugins.path.isAbsolute(relativePathToTsFile)
    ? relativePathToTsFile
    : plugins.path.join(process.cwd(), relativePathToTsFile);

  // we want to have command line arguments available in the child process.
  // when we have a path sepcified through a function there is one argeument less to pay respect to.
  // thus when pathArg is specifed -> we only splice 2
  pathArg ? process.argv.splice(0, 2) : process.argv.splice(0, 3); // this ensures transparent arguments for the child process

  const tsx = await import('tsx/esm/api');
  const unregister = tsx.register();
  await import(absolutePathToTsFile);
};

const runInChildProcess = async (pathArg: string | undefined, cwd: string): Promise<void> => {
  const { spawn } = await import('child_process');

  // Resolve cli.child.js relative to this file
  const cliChildPath = plugins.path.join(__dirname, '../cli.child.js');

  // Build args: [Node flags, entry point, script path, script args]
  const args = [
    ...process.execArgv,           // Preserve --inspect, etc.
    cliChildPath,
    ...process.argv.slice(2)       // Original CLI args (not spliced)
  ];

  return new Promise((resolve, reject) => {
    const child = spawn(process.execPath, args, {
      cwd: cwd,
      env: process.env,
      stdio: 'inherit',
      shell: false,
      windowsHide: false
    });

    // Signal forwarding with cleanup
    const signalHandler = (signal: NodeJS.Signals) => {
      try { child.kill(signal); } catch {}
    };

    const signals: NodeJS.Signals[] = ['SIGINT', 'SIGTERM', 'SIGHUP'];
    signals.forEach(sig => process.on(sig, signalHandler));

    child.on('error', (err) => {
      signals.forEach(sig => process.off(sig, signalHandler));
      reject(err);
    });

    child.on('close', (code, signal) => {
      // Clean up signal handlers
      signals.forEach(sig => process.off(sig, signalHandler));

      if (signal) {
        // Child was terminated by signal
        // On POSIX: try to exit with same signal
        // On Windows: exit with convention (128 + signal number)
        try {
          process.kill(process.pid, signal);
        } catch {
          // Fallback to exit code
          const signalExitCode = signal === 'SIGINT' ? 130 : 128;
          process.exit(signalExitCode);
        }
      } else if (code !== null && code !== 0) {
        process.exit(code);
      } else {
        resolve();
      }
    });
  });
};

export const spawnPath = (
  filePath: string,
  fromFileUrl?: string | URL,
  options?: ISpawnOptions
): ITsrunChildProcess => {
  // 1. Resolve path (similar to runPath)
  const resolvedPath = fromFileUrl
    ? plugins.path.join(
        plugins.path.dirname(
          plugins.url.fileURLToPath(
            typeof fromFileUrl === 'string' ? fromFileUrl : fromFileUrl.href
          )
        ),
        filePath
      )
    : filePath;

  // 2. Build spawn args
  const cliChildPath = plugins.path.join(__dirname, '../cli.child.js');
  const args = [
    ...process.execArgv,
    cliChildPath,
    resolvedPath,
    ...(options?.args || [])
  ];

  // 3. Build spawn options
  const spawnOptions = {
    cwd: options?.cwd || process.cwd(),
    env: { ...process.env, ...options?.env },
    stdio: options?.stdio || 'pipe',
    shell: false,
    windowsHide: false
  };

  // 4. Spawn child process
  const child = plugins.spawn(process.execPath, args, spawnOptions);

  // 5. Set up timeout if provided
  let timeoutId: NodeJS.Timeout | undefined;
  let timeoutTriggered = false;

  if (options?.timeout) {
    timeoutId = setTimeout(() => {
      timeoutTriggered = true;
      child.kill('SIGTERM');
    }, options.timeout);
  }

  // 6. Set up AbortSignal if provided
  let abortHandler: (() => void) | undefined;
  if (options?.signal) {
    abortHandler = () => {
      child.kill('SIGTERM');
    };
    options.signal.addEventListener('abort', abortHandler);
  }

  // 7. Create exitCode promise
  const exitCodePromise = new Promise<number>((resolve, reject) => {
    child.on('close', (code: number | null, signal: NodeJS.Signals | null) => {
      if (timeoutId) clearTimeout(timeoutId);
      if (abortHandler && options?.signal) {
        options.signal.removeEventListener('abort', abortHandler);
      }

      if (timeoutTriggered) {
        reject(new Error(`Process killed: timeout of ${options?.timeout}ms exceeded`));
      } else if (options?.signal?.aborted) {
        reject(new Error('Process killed: aborted by signal'));
      } else if (signal) {
        reject(new Error(`Process killed with signal ${signal}`));
      } else {
        resolve(code || 0);
      }
    });

    child.on('error', (err: Error) => {
      if (timeoutId) clearTimeout(timeoutId);
      if (abortHandler && options?.signal) {
        options.signal.removeEventListener('abort', abortHandler);
      }
      reject(err);
    });
  });

  // 8. Implement terminate() method
  const terminate = async (): Promise<void> => {
    return new Promise((resolve) => {
      if (child.killed) {
        resolve();
        return;
      }

      child.kill('SIGTERM');

      const killTimeout = setTimeout(() => {
        if (!child.killed) {
          child.kill('SIGKILL');
        }
      }, 5000);

      child.on('close', () => {
        clearTimeout(killTimeout);
        resolve();
      });
    });
  };

  // 9. Return ITsrunChildProcess object
  return {
    childProcess: child,
    stdout: child.stdout,
    stderr: child.stderr,
    exitCode: exitCodePromise,
    kill: (signal?: NodeJS.Signals) => child.kill(signal),
    terminate
  };
};