class DataCache {
  constructor() {
    this.devices = new Map(); // deviceNumber -> { data, updatedAt }
  }

  setDeviceData(deviceNumber, data) {
    const now = Date.now();
    this.devices.set(deviceNumber, { data, updatedAt: now });
  }

  getDeviceData(deviceNumber) {
    const entry = this.devices.get(deviceNumber);
    return entry || null;
  }

  getAllDeviceData() {
    const result = {};
    for (const [deviceNumber, value] of this.devices.entries()) {
      result[deviceNumber] = value;
    }
    return result;
  }

  getDeviceList() {
    const list = [];
    for (const [deviceNumber, value] of this.devices.entries()) {
      list.push({ deviceNumber, updatedAt: value.updatedAt });
    }
    return list;
  }

  getStats() {
    const list = this.getDeviceList();
    return {
      count: list.length,
      devices: list
    };
  }

  getIdleDevices(timeoutMs) {
    const now = Date.now();
    const result = [];
    for (const [deviceNumber, value] of this.devices.entries()) {
      if (now - value.updatedAt > timeoutMs) {
        result.push({ deviceNumber, updatedAt: value.updatedAt });
      }
    }
    return result;
  }

  clear() {
    this.devices.clear();
  }
}

module.exports = DataCache;