import * as fs from 'fs';
import * as path from 'path';
import { exec, execFile } from 'child_process';
import { promisify } from 'util';
import { NupstSnmp } from './snmp/manager.js';
import type { ISnmpConfig } from './snmp/types.js';

const execAsync = promisify(exec);
const execFileAsync = promisify(execFile);

/**
 * Configuration interface for the daemon
 */
export interface INupstConfig {
  /** SNMP configuration settings */
  snmp: ISnmpConfig;
  /** 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: INupstConfig = {
    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: INupstConfig;
  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<INupstConfig> {
    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: INupstConfig): 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(): INupstConfig {
    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();
      
      // Log version information
      this.snmp.getNupst().logVersionInfo(false); // Don't check for updates immediately on startup
      
      // Check for updates in the background
      this.snmp.getNupst().checkForUpdates().then(updateAvailable => {
        if (updateAvailable) {
          const updateStatus = this.snmp.getNupst().getUpdateStatus();
          console.log('┌─ Update Available ───────────────────────┐');
          console.log(`│ Current Version: ${updateStatus.currentVersion}`);
          console.log(`│ Latest Version: ${updateStatus.latestVersion}`);
          console.log('│ Run "sudo nupst update" to update');
          console.log('└──────────────────────────────────────────┘');
        }
      }).catch(() => {}); // Ignore errors checking for updates
      
      // 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';
    let lastLogTime = 0; // Track when we last logged status
    const LOG_INTERVAL = 5 * 60 * 1000; // Log at least every 5 minutes (300000ms)
    
    // Monitor continuously
    while (this.isRunning) {
      try {
        const status = await this.snmp.getUpsStatus(this.config.snmp);
        const currentTime = Date.now();
        const shouldLogStatus = (currentTime - lastLogTime) >= LOG_INTERVAL;
        
        // Log status changes
        if (status.powerStatus !== lastStatus) {
          console.log('┌──────────────────────────────────────────┐');
          console.log(`│ Power status changed: ${lastStatus} → ${status.powerStatus}`);
          console.log('└──────────────────────────────────────────┘');
          lastStatus = status.powerStatus;
          lastLogTime = currentTime; // Reset log timer when status changes
        }
        // Log status periodically (at least every 5 minutes)
        else if (shouldLogStatus) {
          const timestamp = new Date().toISOString();
          console.log('┌──────────────────────────────────────────┐');
          console.log(`│ [${timestamp}] Periodic Status Update`);
          console.log(`│ Power Status: ${status.powerStatus}`);
          console.log(`│ Battery: ${status.batteryCapacity}% | Runtime: ${status.batteryRuntime} min`);
          console.log('└──────────────────────────────────────────┘');
          lastLogTime = currentTime;
        }
        
        // 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.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.initiateShutdown('Runtime below threshold');
      return;
    }
  }
  
  /**
   * Initiate system shutdown with UPS monitoring during shutdown
   * @param reason Reason for shutdown
   */
  public async initiateShutdown(reason: string): Promise<void> {
    console.log(`Initiating system shutdown due to: ${reason}`);
    
    // Set a longer delay for shutdown to allow VMs and services to close
    const shutdownDelayMinutes = 5;
    
    try {
      // Find shutdown command in common system paths
      const shutdownPaths = [
        '/sbin/shutdown',
        '/usr/sbin/shutdown',
        '/bin/shutdown',
        '/usr/bin/shutdown'
      ];
      
      let shutdownCmd = '';
      for (const path of shutdownPaths) {
        try {
          if (fs.existsSync(path)) {
            shutdownCmd = path;
            console.log(`Found shutdown command at: ${shutdownCmd}`);
            break;
          }
        } catch (e) {
          // Continue checking other paths
        }
      }
      
      if (shutdownCmd) {
        // Execute shutdown command with delay to allow for VM graceful shutdown
        console.log(`Executing: ${shutdownCmd} -h +${shutdownDelayMinutes} "UPS battery critical..."`);
        const { stdout } = await execFileAsync(shutdownCmd, [
          '-h', 
          `+${shutdownDelayMinutes}`, 
          `UPS battery critical, shutting down in ${shutdownDelayMinutes} minutes`
        ]);
        console.log('Shutdown initiated:', stdout);
        console.log(`Allowing ${shutdownDelayMinutes} minutes for VMs to shut down safely`);
      } else {
        // Try using the PATH to find shutdown
        try {
          console.log('Shutdown command not found in common paths, trying via PATH...');
          const { stdout } = await execAsync(`shutdown -h +${shutdownDelayMinutes} "UPS battery critical, shutting down in ${shutdownDelayMinutes} minutes"`, {
            env: process.env // Pass the current environment
          });
          console.log('Shutdown initiated:', stdout);
        } catch (e) {
          throw new Error(`Shutdown command not found: ${e.message}`);
        }
      }
      
      // Monitor UPS during shutdown and force immediate shutdown if battery gets too low
      console.log('Monitoring UPS during shutdown process...');
      await this.monitorDuringShutdown();
    } catch (error) {
      console.error('Failed to initiate shutdown:', error);
      
      // Try alternative shutdown methods
      const alternatives = [
        { cmd: 'poweroff', args: ['--force'] },
        { cmd: 'halt', args: ['-p'] },
        { cmd: 'systemctl', args: ['poweroff'] },
        { cmd: 'reboot', args: ['-p'] } // Some systems allow reboot -p for power off
      ];
      
      for (const alt of alternatives) {
        try {
          // First check if command exists in common system paths
          const paths = [
            `/sbin/${alt.cmd}`,
            `/usr/sbin/${alt.cmd}`,
            `/bin/${alt.cmd}`,
            `/usr/bin/${alt.cmd}`
          ];
          
          let cmdPath = '';
          for (const path of paths) {
            if (fs.existsSync(path)) {
              cmdPath = path;
              break;
            }
          }
          
          if (cmdPath) {
            console.log(`Trying alternative shutdown method: ${cmdPath} ${alt.args.join(' ')}`);
            await execFileAsync(cmdPath, alt.args);
            return; // Exit if successful
          } else {
            // Try using PATH environment
            console.log(`Trying alternative via PATH: ${alt.cmd} ${alt.args.join(' ')}`);
            await execAsync(`${alt.cmd} ${alt.args.join(' ')}`, {
              env: process.env // Pass the current environment
            });
            return; // Exit if successful
          }
        } catch (altError) {
          console.error(`Alternative method ${alt.cmd} failed:`, altError);
          // Continue to next method
        }
      }
      
      console.error('All shutdown methods failed');
    }
  }
  
  /**
   * Monitor UPS during system shutdown
   * Force immediate shutdown if battery gets critically low
   */
  private async monitorDuringShutdown(): Promise<void> {
    const EMERGENCY_RUNTIME_THRESHOLD = 5; // 5 minutes remaining is critical
    const CHECK_INTERVAL = 30000; // Check every 30 seconds during shutdown
    const MAX_MONITORING_TIME = 5 * 60 * 1000; // Max 5 minutes of monitoring
    const startTime = Date.now();
    
    console.log(`Emergency shutdown threshold: ${EMERGENCY_RUNTIME_THRESHOLD} minutes remaining battery runtime`);
    
    // Continue monitoring until max monitoring time is reached
    while (Date.now() - startTime < MAX_MONITORING_TIME) {
      try {
        console.log('Checking UPS status during shutdown...');
        const status = await this.snmp.getUpsStatus(this.config.snmp);
        
        console.log(`Current battery: ${status.batteryCapacity}%, Runtime: ${status.batteryRuntime} minutes`);
        
        // If battery runtime gets critically low, force immediate shutdown
        if (status.batteryRuntime < EMERGENCY_RUNTIME_THRESHOLD) {
          console.log('┌─ EMERGENCY SHUTDOWN ─────────────────────┐');
          console.log(`│ Battery runtime critically low: ${status.batteryRuntime} minutes`);
          console.log('│ Forcing immediate shutdown!');
          console.log('└──────────────────────────────────────────┘');
          
          try {
            // Find shutdown command in common system paths
            const shutdownPaths = [
              '/sbin/shutdown',
              '/usr/sbin/shutdown',
              '/bin/shutdown',
              '/usr/bin/shutdown'
            ];
            
            let shutdownCmd = '';
            for (const path of shutdownPaths) {
              if (fs.existsSync(path)) {
                shutdownCmd = path;
                console.log(`Found shutdown command at: ${shutdownCmd}`);
                break;
              }
            }
            
            if (shutdownCmd) {
              console.log(`Executing emergency shutdown: ${shutdownCmd} -h now`);
              await execFileAsync(shutdownCmd, ['-h', 'now', 'EMERGENCY: UPS battery critically low, shutting down NOW']);
            } else {
              // Try using the PATH to find shutdown
              console.log('Shutdown command not found in common paths, trying via PATH...');
              await execAsync('shutdown -h now "EMERGENCY: UPS battery critically low, shutting down NOW"', {
                env: process.env // Pass the current environment
              });
            }
          } catch (error) {
            console.error('Emergency shutdown failed, trying alternative methods...');
            
            // Try alternative shutdown methods in sequence
            const alternatives = [
              { cmd: 'poweroff', args: ['--force'] },
              { cmd: 'halt', args: ['-p'] },
              { cmd: 'systemctl', args: ['poweroff'] }
            ];
            
            for (const alt of alternatives) {
              try {
                // Check common paths
                const paths = [
                  `/sbin/${alt.cmd}`,
                  `/usr/sbin/${alt.cmd}`,
                  `/bin/${alt.cmd}`,
                  `/usr/bin/${alt.cmd}`
                ];
                
                let cmdPath = '';
                for (const path of paths) {
                  if (fs.existsSync(path)) {
                    cmdPath = path;
                    break;
                  }
                }
                
                if (cmdPath) {
                  console.log(`Emergency: using ${cmdPath} ${alt.args.join(' ')}`);
                  await execFileAsync(cmdPath, alt.args);
                  return; // Exit if successful
                } else {
                  // Try using PATH
                  console.log(`Emergency: trying ${alt.cmd} via PATH`);
                  await execAsync(`${alt.cmd} ${alt.args.join(' ')}`, {
                    env: process.env
                  });
                  return; // Exit if successful
                }
              } catch (altError) {
                // Continue to next method
              }
            }
            
            console.error('All emergency shutdown methods failed');
          }
          
          // Stop monitoring after initiating emergency shutdown
          return;
        }
        
        // Wait before checking again
        await this.sleep(CHECK_INTERVAL);
      } catch (error) {
        console.error('Error monitoring UPS during shutdown:', error);
        await this.sleep(CHECK_INTERVAL);
      }
    }
    
    console.log('UPS monitoring during shutdown completed');
  }

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