/**
 * UPSD/NIS (Network UPS Tools) TCP client
 *
 * Connects to a NUT upsd server via TCP and queries UPS variables
 * using the NUT network protocol (RFC-style line protocol).
 *
 * Protocol format:
 *   Request:  GET VAR <upsname> <varname>\n
 *   Response: VAR <upsname> <varname> "<value>"\n
 *   Logout:   LOGOUT\n
 */

import * as net from 'node:net';
import { logger } from '../logger.ts';
import { UPSD } from '../constants.ts';
import type { IUpsdConfig } from './types.ts';
import type { IUpsStatus } from '../snmp/types.ts';

/**
 * NupstUpsd - TCP client for the NUT UPSD protocol
 */
export class NupstUpsd {
  private debug = false;

  /**
   * Enable debug logging
   */
  public enableDebug(): void {
    this.debug = true;
    logger.info('UPSD debug mode enabled');
  }

  /**
   * Get the current UPS status via UPSD protocol
   * @param config UPSD connection configuration
   * @returns UPS status matching the IUpsStatus interface
   */
  public async getUpsStatus(config: IUpsdConfig): Promise<IUpsStatus> {
    const host = config.host || '127.0.0.1';
    const port = config.port || UPSD.DEFAULT_PORT;
    const upsName = config.upsName || UPSD.DEFAULT_UPS_NAME;
    const timeout = config.timeout || UPSD.DEFAULT_TIMEOUT_MS;

    if (this.debug) {
      logger.dim('---------------------------------------');
      logger.dim('Getting UPS status via UPSD protocol:');
      logger.dim(`  Host: ${host}:${port}`);
      logger.dim(`  UPS Name: ${upsName}`);
      logger.dim(`  Timeout: ${timeout}ms`);
      logger.dim('---------------------------------------');
    }

    // Variables to query from NUT
    const varsToQuery = [
      'ups.status',
      'battery.charge',
      'battery.runtime',
      'ups.load',
      'ups.realpower',
      'output.voltage',
      'output.current',
    ];

    const values = new Map<string, string>();

    // Open a TCP connection, query all variables, then logout
    const conn = await this.connect(host, port, timeout);

    try {
      // Authenticate if credentials provided
      if (config.username && config.password) {
        await this.sendCommand(conn, `USERNAME ${config.username}`, timeout);
        await this.sendCommand(conn, `PASSWORD ${config.password}`, timeout);
      }

      // Query each variable
      for (const varName of varsToQuery) {
        const value = await this.safeGetVar(conn, upsName, varName, timeout);
        if (value !== null) {
          values.set(varName, value);
        }
      }

      // Logout gracefully
      try {
        await this.sendCommand(conn, 'LOGOUT', timeout);
      } catch (_e) {
        // Ignore logout errors
      }
    } finally {
      conn.destroy();
    }

    // Map NUT variables to IUpsStatus
    const powerStatus = this.parsePowerStatus(values.get('ups.status') || '');
    const batteryCapacity = parseFloat(values.get('battery.charge') || '0');
    const batteryRuntimeSeconds = parseFloat(values.get('battery.runtime') || '0');
    const batteryRuntime = Math.floor(batteryRuntimeSeconds / 60); // NUT reports seconds, convert to minutes
    const outputLoad = parseFloat(values.get('ups.load') || '0');
    const outputPower = parseFloat(values.get('ups.realpower') || '0');
    const outputVoltage = parseFloat(values.get('output.voltage') || '0');
    const outputCurrent = parseFloat(values.get('output.current') || '0');

    const result: IUpsStatus = {
      powerStatus,
      batteryCapacity: isNaN(batteryCapacity) ? 0 : batteryCapacity,
      batteryRuntime: isNaN(batteryRuntime) ? 0 : batteryRuntime,
      outputLoad: isNaN(outputLoad) ? 0 : outputLoad,
      outputPower: isNaN(outputPower) ? 0 : outputPower,
      outputVoltage: isNaN(outputVoltage) ? 0 : outputVoltage,
      outputCurrent: isNaN(outputCurrent) ? 0 : outputCurrent,
      raw: Object.fromEntries(values),
    };

    if (this.debug) {
      logger.dim('---------------------------------------');
      logger.dim('UPSD status result:');
      logger.dim(`  Power Status: ${result.powerStatus}`);
      logger.dim(`  Battery Capacity: ${result.batteryCapacity}%`);
      logger.dim(`  Battery Runtime: ${result.batteryRuntime} minutes`);
      logger.dim(`  Output Load: ${result.outputLoad}%`);
      logger.dim(`  Output Power: ${result.outputPower} watts`);
      logger.dim(`  Output Voltage: ${result.outputVoltage} volts`);
      logger.dim(`  Output Current: ${result.outputCurrent} amps`);
      logger.dim('---------------------------------------');
    }

    return result;
  }

  /**
   * Open a TCP connection to the UPSD server
   */
  private connect(host: string, port: number, timeout: number): Promise<net.Socket> {
    return new Promise((resolve, reject) => {
      const socket = net.createConnection({ host, port }, () => {
        if (this.debug) {
          logger.dim(`Connected to UPSD at ${host}:${port}`);
        }
        resolve(socket);
      });

      socket.setTimeout(timeout);
      socket.on('timeout', () => {
        socket.destroy();
        reject(new Error(`UPSD connection timed out after ${timeout}ms`));
      });
      socket.on('error', (err) => {
        reject(new Error(`UPSD connection error: ${err.message}`));
      });
    });
  }

  /**
   * Send a command and read the response line
   */
  private sendCommand(socket: net.Socket, command: string, timeout: number): Promise<string> {
    return new Promise((resolve, reject) => {
      let responseData = '';
      const timer = setTimeout(() => {
        cleanup();
        reject(new Error(`UPSD command timed out: ${command}`));
      }, timeout);

      const decoder = new TextDecoder();
      const onData = (data: Uint8Array) => {
        responseData += decoder.decode(data, { stream: true });
        // Look for newline to indicate end of response
        const newlineIdx = responseData.indexOf('\n');
        if (newlineIdx !== -1) {
          cleanup();
          const line = responseData.substring(0, newlineIdx).trim();
          if (this.debug) {
            logger.dim(`UPSD << ${line}`);
          }
          resolve(line);
        }
      };

      const onError = (err: Error) => {
        cleanup();
        reject(err);
      };

      const cleanup = () => {
        clearTimeout(timer);
        socket.removeListener('data', onData);
        socket.removeListener('error', onError);
      };

      socket.on('data', onData);
      socket.on('error', onError);

      if (this.debug) {
        logger.dim(`UPSD >> ${command}`);
      }
      socket.write(command + '\n');
    });
  }

  /**
   * Safely get a single NUT variable, returning null on error
   */
  private async safeGetVar(
    socket: net.Socket,
    upsName: string,
    varName: string,
    timeout: number,
  ): Promise<string | null> {
    try {
      const response = await this.sendCommand(
        socket,
        `GET VAR ${upsName} ${varName}`,
        timeout,
      );

      // Expected response: VAR <upsname> <varname> "<value>"
      // Also handle: ERR ... for unsupported variables
      if (response.startsWith('ERR')) {
        if (this.debug) {
          logger.dim(`UPSD variable ${varName} not available: ${response}`);
        }
        return null;
      }

      // Parse: VAR ups battery.charge "100"
      const match = response.match(/^VAR\s+\S+\s+\S+\s+"(.*)"/);
      if (match) {
        return match[1];
      }

      // Some implementations don't quote the value
      const parts = response.split(/\s+/);
      if (parts.length >= 4 && parts[0] === 'VAR') {
        return parts.slice(3).join(' ').replace(/^"/, '').replace(/"$/, '');
      }

      if (this.debug) {
        logger.dim(`UPSD unexpected response for ${varName}: ${response}`);
      }
      return null;
    } catch (error) {
      if (this.debug) {
        logger.dim(
          `UPSD error getting ${varName}: ${error instanceof Error ? error.message : String(error)}`,
        );
      }
      return null;
    }
  }

  /**
   * Parse NUT ups.status tokens into a power status
   * NUT status tokens: OL (online), OB (on battery), LB (low battery),
   * HB (high battery), RB (replace battery), CHRG (charging), etc.
   */
  private parsePowerStatus(statusString: string): 'online' | 'onBattery' | 'unknown' {
    const tokens = statusString.trim().split(/\s+/);

    if (tokens.includes('OB')) {
      return 'onBattery';
    }
    if (tokens.includes('OL')) {
      return 'online';
    }

    return 'unknown';
  }
}