import path from 'path';
import os from 'os';
import fs from 'fs/promises';

import { TransformerPath } from '../types/runner';
import { generateUID, merge } from './helper';

/**
 * Filters out the list of file paths containing the given extension
 * @param files List of file paths
 * @param extensions Extensions of the file to filter out from the given list
 * @returns list of filtered files list
 */
export const filterFiles = (files: string[], extensions: string[]): string[][] => {
  const filtered: string[][] = [];
  const lastIdx = extensions.length;

  extensions.forEach((_, idx) => (filtered[idx] = []));
  filtered[lastIdx] = [];

  files.forEach((file) => {
    const ext = file.split('.').pop() || '';
    const idx = extensions.indexOf(ext);

    if (idx > -1) {
      filtered[idx].push(file);
    } else {
      filtered[lastIdx].push(file);
    }
  });

  return filtered;
};

/**
 * Returns the path to the transform file used by JSCodeshift
 * @param transformer Partial path to the transform file
 * @param ext Extension of the transform file
 */
export const getTransformFile = (transformer: TransformerPath, ext: 'ts' | 'js' = 'js'): string =>
  path.resolve(__dirname, `../transformers/${transformer}.${ext}`);

/**
 * Creates a directory in the OS temp directory where temporary files will be stored
 * @param prefix Prefix for the temp directory
 * @returns The path to the created temp directory
 */
export const initTempDir = async (prefix: string): Promise<string> => fs.mkdtemp(path.join(os.tmpdir(), prefix));

/**
 * Saves data into a temporary file storage
 * @param data Data to be stored
 * @param dirPath Path to the temporary directory where a temp file will be created
 */
export const saveTempData = async <T>(data: T, dirPath: string): Promise<void> => {
  try {
    const tmpFilePath = path.join(dirPath, `${generateUID()}.json`);

    await fs.writeFile(tmpFilePath, JSON.stringify(data), { encoding: 'utf8' });
  } catch (e: any) {
    throw new Error(e.message);
  }
};

/**
 * Reads and returns the data from the temporary file storage
 * @param dirPath Path to temp directory
 * @param cleanup Should delete temp directory
 * @returns Data merged from all the files in the temp directory
 */
export const readTempData = async <T>(dirPath: string, cleanup: boolean = true): Promise<T> => {
  try {
    const files = await fs.readdir(dirPath);
    const finalResult = {} as T;
    for (const file of files) {
      const fileContent = await fs.readFile(path.resolve(dirPath, file), { encoding: 'utf8' });
      const data = JSON.parse(fileContent) as T;
      merge<T>(finalResult, data);
    }

    if (cleanup) {
      await fs.rm(dirPath, { recursive: true, force: true });
    }

    return finalResult;
  } catch (e: any) {
    throw new Error(e.message);
  }
};