import * as path from 'path';
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.
   *
   * Renames the nested directory to a temp location, removes the dest dir,
   * then renames the temp dir back as dest. Uses only rename operations
   * which are atomic at the kernel level.
   *
   * 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__';

    // Step 1: Clean up any leftover temp dir from a previous failed run
    await FsHelpers.removeDirectory(tempPath);

    // Step 2: Rename nested → temp
    await FsHelpers.move(nestedPath, tempPath);

    // Step 3: Remove dest dir (now contains only sibling folders)
    await FsHelpers.removeDirectory(this.destDir);

    // Step 4: Rename temp → dest
    await FsHelpers.move(tempPath, this.destDir);

    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();
}