import * as path from 'path';
import { execSync } from 'child_process';
import { TsPublishConfig } from '../mod_config/index.js';
import { FsHelpers } from '../mod_fs/index.js';

/**
 * TsUnpacker handles flattening of nested TypeScript output directories.
 *
 * When TypeScript compiles files that import from sibling directories,
 * it creates a nested structure like:
 *   dist_ts_core/ts_core/index.js
 *   dist_ts_core/ts_shared/helper.js
 *
 * This class flattens it to:
 *   dist_ts_core/index.js
 */
export class TsUnpacker {
  private sourceFolderName: string;
  private destDir: string;
  private cwd: string;
  private config: TsPublishConfig;

  constructor(sourceFolderName: string, destDir: string, cwd: string = process.cwd()) {
    this.sourceFolderName = sourceFolderName;
    this.destDir = destDir;
    this.cwd = cwd;
    this.config = new TsPublishConfig(path.join(cwd, sourceFolderName));
  }

  /**
   * Create an unpacker from a glob pattern
   * './ts_core/**\/*.ts' → sourceFolderName = 'ts_core'
   */
  public static fromGlobPattern(
    sourcePattern: string,
    destDir: string,
    cwd: string = process.cwd()
  ): TsUnpacker | null {
    const sourceFolderName = FsHelpers.extractSourceFolder(sourcePattern);
    if (!sourceFolderName) {
      return null;
    }
    return new TsUnpacker(sourceFolderName, destDir, cwd);
  }

  /**
   * Get the source folder name
   */
  public getSourceFolderName(): string {
    return this.sourceFolderName;
  }

  /**
   * Get the destination directory
   */
  public getDestDir(): string {
    return this.destDir;
  }

  /**
   * Check if unpacking should be performed based on tspublish.json config
   * Default is true if not specified
   */
  public async shouldUnpack(): Promise<boolean> {
    return this.config.shouldUnpack;
  }

  /**
   * Check if nested structure exists in the destination directory
   */
  public async detectNesting(): Promise<boolean> {
    const nestedPath = path.join(this.destDir, this.sourceFolderName);
    return FsHelpers.directoryExists(nestedPath);
  }

  /**
   * Get the path to the nested directory
   */
  public getNestedPath(): string {
    return path.join(this.destDir, this.sourceFolderName);
  }

  /**
   * Perform the unpack operation - flatten nested output directories.
   *
   * Uses shell commands (mv, rm) via execSync for reliability. Node.js async
   * fs operations (rename, rm) can race on XFS filesystems where metadata
   * commits are delayed, causing ENOENT or partial directory listings.
   * Shell commands execute as direct syscalls without libuv's async layer.
   *
   * Returns true if unpacking was performed, false if skipped.
   */
  public async unpack(): Promise<boolean> {
    if (!(await this.shouldUnpack())) {
      return false;
    }

    if (!(await this.detectNesting())) {
      return false;
    }

    const nestedPath = this.getNestedPath();
    const tempPath = this.destDir + '.__unpack_temp__';

    // Use shell commands for atomic, sequential filesystem operations.
    // This avoids race conditions between Node.js async fs operations on XFS.
    execSync(`rm -rf "${tempPath}"`, { stdio: 'ignore' });
    execSync(`mv "${nestedPath}" "${tempPath}"`, { stdio: 'ignore' });
    execSync(`rm -rf "${this.destDir}"`, { stdio: 'ignore' });
    execSync(`mv "${tempPath}" "${this.destDir}"`, { stdio: 'ignore' });

    return true;
  }
}

/**
 * Convenience function to perform unpack operation
 * Can be used directly without instantiating the class
 */
export async function performUnpack(
  sourcePattern: string,
  destDir: string,
  cwd: string = process.cwd()
): Promise<boolean> {
  const unpacker = TsUnpacker.fromGlobPattern(sourcePattern, destDir, cwd);
  if (!unpacker) {
    return false;
  }
  return unpacker.unpack();
}