import path from 'path';
import fs from 'fs';

export default class HistoryFile {
  constructor(fileName) {
    this.path = path.join(process.cwd(), fileName);
    this.history = [];
    this.load();
  }

  /**
   * Writes history to file
   * @returns {boolean} true if successful, false otherwise
   */
  writeToFile() {
    try {
      fs.writeFileSync(this.path, JSON.stringify(this.history, null, 2));
      return true;
    } catch (err) {
      console.error(`Failed to write data to history file: ${err.message}`);
      return false;
    }
  }

  /**
   * Reads history file, and returns it as JSON
   * @returns {array}
   */
  readFromFile() {
    try {
      const raw = fs.readFileSync(this.path, 'utf-8');
      return JSON.parse(raw);
    } catch (err) {
      console.warn(`Failed at reading history, using empty history: ${err.message}`);
      return [];
    }
  }

  /**
   * Loads history file, if it exists
   * If not, creates empty file
   */
  load() {
    if (fs.existsSync(this.path)) {
      // Read file, and update this.history
      const data = this.readFromFile();
      this.history = data;
    } else {
      // Create empty history file, if doesn't exist
      this.writeToFile();
    }
  }

  /**
   * Saves most recent 15 entries to history file
   */
  save() {
    // If there's more than 15 entries, we need to save only most recent 15 ones
    if (this.history.length > 15) {
      this.history = this.history.slice(this.history.length - 15);
    }

    // Write to history file
    this.writeToFile();
  }

  /**
   * Appends new entry to history file
   * Returns most recent entry
   * @param {number} number
   * @returns {object}
   */
  append(number) {
    const data = { number, timestamp: Date.now() };
    // Push new entry to history
    this.history.push(data);
    // Save history file, and keep only 15 entries
    this.save();
    // Return most recent entry
    return data;
  }
}