import * as fs from 'fs';
import * as path from 'path';
import { NupstSnmp, type SnmpConfig } from './snmp.js';

/**
 * Configuration interface for the daemon
 */
export interface NupstConfig {
  /** SNMP configuration settings */
  snmp: SnmpConfig;
  /** Threshold settings for initiating shutdown */
  thresholds: {
    /** Shutdown when battery below this percentage */
    battery: number;
    /** Shutdown when runtime below this minutes */
    runtime: number;
  };
  /** Check interval in milliseconds */
  checkInterval: number;
}

/**
 * Daemon class for monitoring UPS and handling shutdown
 * Responsible for loading/saving config and monitoring the UPS status
 */
export class NupstDaemon {
  /** Default configuration path */
  private readonly CONFIG_PATH = '/etc/nupst/config.json';

  /** Default configuration */
  private readonly DEFAULT_CONFIG: NupstConfig = {
    snmp: {
      host: '127.0.0.1',
      port: 161,
      community: 'public',
      version: 1,
      timeout: 5000,
      // SNMPv3 defaults (used only if version === 3)
      securityLevel: 'authPriv',
      username: '',
      authProtocol: 'SHA',
      authKey: '',
      privProtocol: 'AES',
      privKey: '',
      // UPS model for OID selection
      upsModel: 'cyberpower'
    },
    thresholds: {
      battery: 60, // Shutdown when battery below 60%
      runtime: 20, // Shutdown when runtime below 20 minutes
    },
    checkInterval: 30000, // Check every 30 seconds
  };

  private config: NupstConfig;
  private snmp: NupstSnmp;
  private isRunning: boolean = false;
  
  /**
   * Create a new daemon instance with the given SNMP manager
   */
  constructor(snmp: NupstSnmp) {
    this.snmp = snmp;
    this.config = this.DEFAULT_CONFIG;
  }

  /**
   * Load configuration from file
   * @throws Error if configuration file doesn't exist
   */
  public async loadConfig(): Promise<NupstConfig> {
    try {
      // Check if config file exists
      const configExists = fs.existsSync(this.CONFIG_PATH);
      if (!configExists) {
        const errorMsg = `No configuration found at ${this.CONFIG_PATH}`;
        this.logConfigError(errorMsg);
        throw new Error(errorMsg);
      }
      
      // Read and parse config
      const configData = fs.readFileSync(this.CONFIG_PATH, 'utf8');
      this.config = JSON.parse(configData);
      return this.config;
    } catch (error) {
      if (error.message.includes('No configuration found')) {
        throw error; // Re-throw the no configuration error
      }
      
      this.logConfigError(`Error loading configuration: ${error.message}`);
      throw new Error('Failed to load configuration');
    }
  }

  /**
   * Save configuration to file
   */
  public async saveConfig(config: NupstConfig): Promise<void> {
    try {
      const configDir = path.dirname(this.CONFIG_PATH);
      if (!fs.existsSync(configDir)) {
        fs.mkdirSync(configDir, { recursive: true });
      }
      fs.writeFileSync(this.CONFIG_PATH, JSON.stringify(config, null, 2));
      this.config = config;
      
      console.log('┌─ Configuration Saved ─────────────────────┐');
      console.log(`│ Location: ${this.CONFIG_PATH}`);
      console.log('└──────────────────────────────────────────┘');
    } catch (error) {
      console.error('Error saving configuration:', error);
    }
  }

  /**
   * Helper method to log configuration errors consistently
   */
  private logConfigError(message: string): void {
    console.error('┌─ Configuration Error ─────────────────────┐');
    console.error(`│ ${message}`);
    console.error('│ Please run \'nupst setup\' first to create a configuration.');
    console.error('└──────────────────────────────────────────┘');
  }

  /**
   * Get the current configuration
   */
  public getConfig(): NupstConfig {
    return this.config;
  }
  
  /**
   * Get the SNMP instance
   */
  public getNupstSnmp(): NupstSnmp {
    return this.snmp;
  }

  /**
   * Start the monitoring daemon
   */
  public async start(): Promise<void> {
    if (this.isRunning) {
      console.log('Daemon is already running');
      return;
    }

    console.log('Starting NUPST daemon...');
    
    try {
      // Load configuration - this will throw an error if config doesn't exist
      await this.loadConfig();
      this.logConfigLoaded();
      
      // Start UPS monitoring
      this.isRunning = true;
      await this.monitor();
    } catch (error) {
      this.isRunning = false;
      console.error(`Daemon failed to start: ${error.message}`);
      process.exit(1); // Exit with error
    }
  }

  /**
   * Log the loaded configuration settings
   */
  private logConfigLoaded(): void {
    console.log('┌─ Configuration Loaded ─────────────────────┐');
    console.log('│ SNMP Settings:');
    console.log(`│   Host: ${this.config.snmp.host}`);
    console.log(`│   Port: ${this.config.snmp.port}`);
    console.log(`│   Version: ${this.config.snmp.version}`);
    console.log('│ Thresholds:');
    console.log(`│   Battery: ${this.config.thresholds.battery}%`);
    console.log(`│   Runtime: ${this.config.thresholds.runtime} minutes`);
    console.log(`│ Check Interval: ${this.config.checkInterval / 1000} seconds`);
    console.log('└──────────────────────────────────────────┘');
  }

  /**
   * Stop the monitoring daemon
   */
  public stop(): void {
    console.log('Stopping NUPST daemon...');
    this.isRunning = false;
  }

  /**
   * Monitor the UPS status and trigger shutdown when necessary
   */
  private async monitor(): Promise<void> {
    console.log('Starting UPS monitoring...');
    
    let lastStatus: 'online' | 'onBattery' | 'unknown' = 'unknown';
    
    // Monitor continuously
    while (this.isRunning) {
      try {
        const status = await this.snmp.getUpsStatus(this.config.snmp);
        
        // Log status changes
        if (status.powerStatus !== lastStatus) {
          console.log('┌──────────────────────────────────────────┐');
          console.log(`│ Power status changed: ${lastStatus} → ${status.powerStatus}`);
          console.log('└──────────────────────────────────────────┘');
          lastStatus = status.powerStatus;
        }
        
        // Handle battery power status
        if (status.powerStatus === 'onBattery') {
          await this.handleOnBatteryStatus(status);
        }
        
        // Wait before next check
        await this.sleep(this.config.checkInterval);
      } catch (error) {
        console.error('Error during UPS monitoring:', error);
        await this.sleep(this.config.checkInterval);
      }
    }
    
    console.log('UPS monitoring stopped');
  }

  /**
   * Handle UPS status when running on battery
   */
  private async handleOnBatteryStatus(status: { 
    powerStatus: string,
    batteryCapacity: number,
    batteryRuntime: number
  }): Promise<void> {
    console.log('┌─ UPS Status ───────────────────────────────┐');
    console.log(`│ Battery: ${status.batteryCapacity}% | Runtime: ${status.batteryRuntime} min │`);
    console.log('└──────────────────────────────────────────┘');
    
    // Check battery threshold
    if (status.batteryCapacity < this.config.thresholds.battery) {
      console.log('⚠️ WARNING: Battery capacity below threshold');
      console.log(`Current: ${status.batteryCapacity}% | Threshold: ${this.config.thresholds.battery}%`);
      await this.snmp.initiateShutdown('Battery capacity below threshold');
      return;
    }
    
    // Check runtime threshold
    if (status.batteryRuntime < this.config.thresholds.runtime) {
      console.log('⚠️ WARNING: Runtime below threshold');
      console.log(`Current: ${status.batteryRuntime} min | Threshold: ${this.config.thresholds.runtime} min`);
      await this.snmp.initiateShutdown('Runtime below threshold');
      return;
    }
  }

  /**
   * Sleep for the specified milliseconds
   */
  private sleep(ms: number): Promise<void> {
    return new Promise(resolve => setTimeout(resolve, ms));
  }
}