feat: add data generation logic and history file class

backend/classes/HistoryFile.js

@@ -0,0 +1,82 @@
+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));
+      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;
+  }
+}