import * as fs from 'fs';
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.
   *
   * Strategy: instead of listing entries and moving them individually (which is
   * vulnerable to async readdir returning partial results under signal pressure),
   * we rename the entire nested directory out, remove the dest dir, then rename
   * the nested directory back as the dest dir. This 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__';

    // Log what we're about to do
    const nestedEntries = fs.readdirSync(nestedPath);
    console.log(`   📦 Unpacking ${this.sourceFolderName}/: ${nestedEntries.length} entries in nested dir`);
    console.log(`   📦 Entries: [${nestedEntries.join(', ')}]`);
    // Also list the dest dir to see what TypeScript created
    const destEntries = fs.readdirSync(this.destDir);
    console.log(`   📦 destDir entries: [${destEntries.join(', ')}]`);

    // Clean up any leftover temp dir from a previous failed unpack
    await fs.promises.rm(tempPath, { recursive: true, force: true });

    // Step 1: Rename the nested source folder out to a temp location.
    //         e.g. dist_ts/ts/ → dist_ts.__unpack_temp__/
    await fs.promises.rename(nestedPath, tempPath);

    // Verify step 1
    const tempEntries = fs.readdirSync(tempPath);
    console.log(`   📦 Step 1 (rename to temp): ${tempEntries.length} entries in temp`);

    // Step 2: Remove the dest dir (which now only contains sibling folders
    //         like ts_interfaces/). Use recursive rm to handle any contents.
    await fs.promises.rm(this.destDir, { recursive: true, force: true, maxRetries: 3, retryDelay: 100 });
    console.log(`   📦 Step 2 (remove dest): done`);

    // Step 3: Rename the temp dir to the dest dir.
    //         e.g. dist_ts.__unpack_temp__/ → dist_ts/
    await fs.promises.rename(tempPath, this.destDir);

    // Verify final state
    const finalEntries = fs.readdirSync(this.destDir);
    const finalDirs = finalEntries.filter((e: string) => {
      return fs.statSync(path.join(this.destDir, e)).isDirectory();
    });
    console.log(`   📦 Step 3 (rename to dest): ${finalEntries.length} entries (${finalDirs.length} dirs)`);

    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();
}