moveAndMaybeCompressFile.js

const debug = require('debug')('streamroller:moveAndMaybeCompressFile');
const fs = require('fs-extra');
const zlib = require('zlib');

const _parseOption = function(rawOptions){
  const defaultOptions = {
    mode: parseInt("0600", 8),
    compress: false,
  };
  const options = Object.assign({}, defaultOptions, rawOptions);
  debug(`_parseOption: moveAndMaybeCompressFile called with option=${JSON.stringify(options)}`);
  return options;
};

const moveAndMaybeCompressFile = async (
  sourceFilePath,
  targetFilePath,
  options
) => {
  options = _parseOption(options);

  if (sourceFilePath === targetFilePath) {
    debug(`moveAndMaybeCompressFile: source and target are the same, not doing anything`);
    return;
  }

  if (await fs.pathExists(sourceFilePath)) {
    debug(
      `moveAndMaybeCompressFile: moving file from ${sourceFilePath} to ${targetFilePath} ${
        options.compress ? "with" : "without"
      } compress`
    );
    if (options.compress) {
      await new Promise((resolve, reject) => {
        let isCreated = false;
        // to avoid concurrency, the forked process which can create the file will proceed (using flags wx)
        const writeStream = fs.createWriteStream(targetFilePath, { mode: options.mode, flags: "wx" })
          // wait until writable stream is valid before proceeding to read
          .on("open", () => {
            isCreated = true;
            const readStream = fs.createReadStream(sourceFilePath)
              // wait until readable stream is valid before piping
              .on("open", () => {
                readStream.pipe(zlib.createGzip()).pipe(writeStream);
              })
              .on("error", (e) => {
                debug(`moveAndMaybeCompressFile: error reading ${sourceFilePath}`, e);
                // manually close writable: https://nodejs.org/api/stream.html#readablepipedestination-options
                writeStream.destroy(e);
              });
          })
          .on("finish", () => {
            debug(`moveAndMaybeCompressFile: finished compressing ${targetFilePath}, deleting ${sourceFilePath}`);
            // delete sourceFilePath
            fs.unlink(sourceFilePath)
              .then(resolve)
              .catch((e) => {
                debug(`moveAndMaybeCompressFile: error deleting ${sourceFilePath}, truncating instead`, e);
                // fallback to truncate
                fs.truncate(sourceFilePath)
                  .then(resolve)
                  .catch((e) => {
                    debug(`moveAndMaybeCompressFile: error truncating ${sourceFilePath}`, e);
                    reject(e);
                  });
              });
          })
          .on("error", (e) => {
            if (!isCreated) {
              debug(`moveAndMaybeCompressFile: error creating ${targetFilePath}`, e);
              // do not do anything if handled by another forked process
              reject(e);
            } else {
              debug(`moveAndMaybeCompressFile: error writing ${targetFilePath}, deleting`, e);
              // delete targetFilePath (taking as nothing happened)
              fs.unlink(targetFilePath)
                .then(() => { reject(e); })
                .catch((e) => {
                  debug(`moveAndMaybeCompressFile: error deleting ${targetFilePath}`, e);
                  reject(e);
                });
            }
          });
      }).catch(() => {});
    } else {
      debug(`moveAndMaybeCompressFile: renaming ${sourceFilePath} to ${targetFilePath}`);
      try {
        await fs.move(sourceFilePath, targetFilePath, { overwrite: true });
      } catch (e) {
        debug(`moveAndMaybeCompressFile: error renaming ${sourceFilePath} to ${targetFilePath}`, e);
        /* istanbul ignore else: no need to do anything if file does not exist */
        if (e.code !== "ENOENT") {
          debug(`moveAndMaybeCompressFile: trying copy+truncate instead`);
          try {
            await fs.copy(sourceFilePath, targetFilePath, { overwrite: true });
            await fs.truncate(sourceFilePath);
          } catch (e) {
            debug(`moveAndMaybeCompressFile: error copy+truncate`, e);
          }
        }
      }
    }
  }
};

module.exports = moveAndMaybeCompressFile;