astroturf/memory-fs.js

"use strict";

const path = require('path');

const {
  createHash
} = require('crypto');

const errors = require('errno');

const util = require('util');

const {
  ReadableStream,
  WritableStream
} = require('stream');

const MemoryFileSystemError = require('memory-fs/lib/MemoryFileSystem');

const debug = util.debuglog('astroturf:memory-fs');

const returnsTrue = () => true;

const returnsFalse = () => false;

const md5 = input => {
  const hash = createHash('md5');
  hash.update(input);
  return hash.digest('hex');
};

const read = (file, optsOrEncoding) => {
  const encoding = (optsOrEncoding === null || optsOrEncoding === void 0 ? void 0 : optsOrEncoding.encoding) || optsOrEncoding;
  file.atime = new Date();
  return encoding ? file.contents.toString(encoding) : file.contents;
};
/**
 * A simple in memorry ponyfill of the node fs that stores objects in memory.
 * We don't use `memory-fs` because our use-case is much narrower (only need files not dirs)
 * and it doesn't support stat timestamps
 */


class MemoryFs {
  constructor() {
    this.addFile = (p, data, updateMtime = false) => {
      p = path.normalize(p);
      const hash = md5(data);
      const existing = this.paths.get(p);
      const keepTime = !updateMtime && existing && existing.hash === hash;
      if (!keepTime) debug(`${existing ? 'modifying' : 'writing'} file ${path.relative(process.cwd(), p)} [${hash}]`);
      const mtime = keepTime ? existing.mtime : new Date();
      this.paths.set(p, {
        hash,
        contents: Buffer.isBuffer(data) ? data : Buffer.from(data),
        birthtime: existing ? existing.birthtime : new Date(),
        ctime: existing ? existing.ctime : new Date(),
        atime: existing ? existing.atime : new Date(),
        mtime
      });
      return mtime;
    };

    this.getPaths = () => this.paths;

    this.exists = (p, cb) => cb(this.existsSync(p));

    this.existsSync = p => this.paths.has(path.normalize(p));

    this.statSync = p => {
      const file = this.paths.get(path.normalize(p));
      if (file) return {
        mtime: file.mtime,
        atime: file.atime,
        ctime: file.ctime,
        birthtime: file.birthtime,
        mtimeMs: file.mtime.getTime(),
        atimeMs: file.atime.getTime(),
        ctimeMs: file.ctime.getTime(),
        birthtimeMs: file.birthtime.getTime(),
        isFile: returnsTrue,
        isDirectory: returnsFalse,
        isBlockDevice: returnsFalse,
        isCharacterDevice: returnsFalse,
        isSymbolicLink: returnsFalse,
        isFIFO: returnsFalse,
        isSocket: returnsFalse
      };
      throw new MemoryFileSystemError(errors.code.ENOENT, p, 'stat');
    };

    this.readFileSync = (p, optsOrEncoding) => {
      p = path.normalize(p);
      if (!this.existsSync(p)) throw new MemoryFileSystemError(errors.code.ENOENT, p, 'readFile');
      return read(this.paths.get(p), optsOrEncoding);
    };

    this.readdirSync = p => {
      const results = [];
      p = path.normalize(p);
      this.paths.forEach((_, key) => {
        if (key.startsWith(p)) results.push(key);
      });
    };

    this.rmdirSync = p => {
      p = path.normalize(p);
      this.paths.forEach((_, key) => {
        if (p.startsWith(key)) this.unlinkSync(key);
      });
    };

    this.unlinkSync = p => this.paths.delete(p);

    this.writeFileSync = (p, data) => {
      this.addFile(p, data, true);
    };

    this.paths = new Map();
    ['stat', 'readdir', 'rmdir', 'unlink', 'readFile', 'writeFile'].forEach(fn => {
      this[fn] = (...args) => {
        const cb = args.pop();
        let result;

        try {
          result = this[`${fn}Sync`](...args);
        } catch (err) {
          setImmediate(() => cb(err));
          return;
        }

        setImmediate(() => cb(null, result));
      };
    });
  }

  /** stream methods taken from memory-fs */
  createReadStream(p, options) {
    const stream = new ReadableStream();
    let done = false;
    let data;

    try {
      data = this.readFileSync(p);
    } catch (e) {
      // eslint-disable-next-line no-underscore-dangle
      stream._read = function $read() {
        if (done) return;
        done = true;
        this.emit('error', e);
        this.push(null);
      };

      return stream;
    }

    options = options || {};
    options.start = options.start || 0;
    options.end = options.end || data.length; // eslint-disable-next-line no-underscore-dangle

    stream._read = function $read() {
      if (done) return;
      done = true;
      this.push(data.slice(options.start, options.end));
      this.push(null);
    };

    return stream;
  }

  createWriteStream(p) {
    const stream = new WritableStream();

    try {
      this.writeFileSync(p, Buffer.from(0));
    } catch (e) {
      stream.once('prefinish', () => {
        stream.emit('error', e);
      });
      return stream;
    }

    const bl = [];
    let len = 0; // eslint-disable-next-line no-underscore-dangle

    stream._write = (chunk, encoding, callback) => {
      bl.push(chunk);
      len += chunk.length;
      this.writeFile(p, Buffer.concat(bl, len), callback);
    };

    return stream;
  }

}

module.exports = MemoryFs;