workwatch/src/file/file.js

A Linux terminal program for honest worktime tracking and billing.

/**
 * This file is part of the WorkWatch, a Linux terminal program for honest
 * worktime tracking and billing.
 *
 * Copyright (C) 2020-2025 by Artur Rutkowski
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * WorkWatch is beeing developped and maintained by Artur (locust) Rutkwoski
 * <locust@mailbox.org>
 */

/**
 * This file defines the basic file-handling object which is beeing extended to
 * the particular file-type objects with their methods and getters using
 * prototype chaining as the natural JavaScript inheritance.
 */
const fs = require("node:fs");

// Constructor.
function WorkWatchFile(jsonContent, pathToJSONFile = null) {
  let workWatchFileJSON = JSON.parse(jsonContent);
  let workWatchFilePath = pathToJSONFile;
  
  // The getter providing the instantiated file content.
  Object.defineProperty(this, "fileContent", {
    get() {
      return workWatchFileJSON;
    },
    enumerable: false,
    configurable: false
  });

  // The getter providing instantiated file path.
  Object.defineProperty(this, "filePath", {
    get() {
      return workWatchFilePath;
    },
    enumerable: false,
    configurable: false
  });

  Object.preventExtensions(this);
}

// The prototype method which creates new file or saves existing one.
Object.defineProperty(WorkWatchFile.prototype, "createOrSave", {
  value: function createOrSave() {
    return new Promise((resolve, reject) => {
      // Validate file content before writing to disk.
      this.verify()
      .then(verifySuccess => {
        const jsonFileWriteStream = fs.createWriteStream(this.filePath);
        jsonFileWriteStream.on("error", (err) => {
          reject(err);
        });
        jsonFileWriteStream.on("ready", () => {
          jsonFileWriteStream.end(JSON.stringify(this.fileContent));
          resolve(true);
        });
      })
      .catch(verifyError => reject(verifyError));
    });
  },
  writable: false,
  enumerable: false,
  configurable: false
});

// The prototype empty file content verification method designated to be
// overriden by derived objects' one.
Object.defineProperty(WorkWatchFile.prototype, "verify", {
  value: function verify() {
    return Promise.resolve(true);
  },
  writable: false,
  enumerable: false,
  configurable: false
});

// Reads and instantiates existing file. Used by derived objects which
// extend it by handling errors.
Object.defineProperty(WorkWatchFile, "load", {
  value: function load(
    pathToJSONFile,
    validateContent = true,
    fileObjectConstructor = WorkWatchFile
  ) {
    return new Promise((resolve, reject) => {
      // Each derived file object is singleton, so return existing instance
      // of the object.
      if (fileObjectConstructor.instance !== undefined) {
        resolve(fileObjectConstructor.instance);
      } else {
        // Load file and create the instance property pointing to it.
        let jsonContent = "";
        const jsonFileReadStream = fs.createReadStream(pathToJSONFile);
        jsonFileReadStream.on("error", (err) => {
          reject(err);
        });
        jsonFileReadStream.on("data", (chunk) => jsonContent += chunk);
        jsonFileReadStream.on("end", () => {
          Object.defineProperty(fileObjectConstructor, "instance", {
            value: new fileObjectConstructor(jsonContent, pathToJSONFile),
            writable: false,
            enumerable: false,
            configurable: false
          });
          if (!validateContent) {
            resolve(fileObjectConstructor.instance);
          } else {
            fileObjectConstructor.instance.verify()
            .then(verifySuccess => resolve(fileObjectConstructor.instance))
            .catch(verifyError => reject(verifyError));
          }
        });
      }
    });
  },
  writable: false,
  enumerable: false,
  configurable: false
});
module.exports = WorkWatchFile;