import * as plugins from './plugins.js';
import type {
  IRadiusClientOptions,
  IClientAuthRequest,
  IClientAuthResponse,
  IClientAccountingRequest,
  IClientAccountingResponse,
} from './interfaces.js';
import {
  RadiusPacket,
  RadiusAuthenticator,
  RadiusAttributes,
  ERadiusCode,
  ERadiusAttributeType,
} from '../ts_server/index.js';

/**
 * Pending request tracking
 */
interface IPendingRequest {
  identifier: number;
  requestAuthenticator: Buffer;
  resolve: (response: Buffer) => void;
  reject: (error: Error) => void;
  timeoutId?: ReturnType<typeof setTimeout>;
  retries: number;
  packet: Buffer;
  port: number;
}

/**
 * RADIUS Client implementation
 * Supports PAP, CHAP authentication and accounting
 */
export class RadiusClient {
  private socket?: plugins.dgram.Socket;
  private readonly options: Required<IRadiusClientOptions>;
  private currentIdentifier = 0;
  private readonly pendingRequests: Map<number, IPendingRequest> = new Map();
  private isConnected = false;

  constructor(options: IRadiusClientOptions) {
    this.options = {
      host: options.host,
      authPort: options.authPort ?? 1812,
      acctPort: options.acctPort ?? 1813,
      secret: options.secret,
      timeout: options.timeout ?? 5000,
      retries: options.retries ?? 3,
      retryDelay: options.retryDelay ?? 1000,
      nasIpAddress: options.nasIpAddress ?? '0.0.0.0',
      nasIdentifier: options.nasIdentifier ?? 'smartradius-client',
    };
  }

  /**
   * Connect the client (bind UDP socket)
   */
  public async connect(): Promise<void> {
    if (this.isConnected) {
      return;
    }

    return new Promise((resolve, reject) => {
      this.socket = plugins.dgram.createSocket('udp4');

      this.socket.on('error', (err) => {
        if (!this.isConnected) {
          reject(err);
        }
      });

      this.socket.on('message', (msg) => {
        this.handleResponse(msg);
      });

      this.socket.bind(0, () => {
        this.isConnected = true;
        resolve();
      });
    });
  }

  /**
   * Disconnect the client
   */
  public async disconnect(): Promise<void> {
    if (!this.isConnected || !this.socket) {
      return;
    }

    // Reject all pending requests
    for (const [, pending] of this.pendingRequests) {
      if (pending.timeoutId) {
        clearTimeout(pending.timeoutId);
      }
      pending.reject(new Error('Client disconnected'));
    }
    this.pendingRequests.clear();

    return new Promise((resolve) => {
      this.socket!.close(() => {
        this.socket = undefined;
        this.isConnected = false;
        resolve();
      });
    });
  }

  /**
   * Authenticate a user using PAP
   */
  public async authenticatePap(username: string, password: string): Promise<IClientAuthResponse> {
    return this.authenticate({
      username,
      password,
    });
  }

  /**
   * Authenticate a user using CHAP
   */
  public async authenticateChap(
    username: string,
    password: string,
    challenge?: Buffer
  ): Promise<IClientAuthResponse> {
    // Generate challenge if not provided
    const chapChallenge = challenge || plugins.crypto.randomBytes(16);
    const chapId = Math.floor(Math.random() * 256);

    // Calculate CHAP response
    const chapResponse = RadiusAuthenticator.calculateChapResponse(chapId, password, chapChallenge);

    // CHAP-Password = CHAP Ident (1 byte) + Response (16 bytes)
    const chapPassword = Buffer.allocUnsafe(17);
    chapPassword.writeUInt8(chapId, 0);
    chapResponse.copy(chapPassword, 1);

    return this.authenticate({
      username,
      chapPassword,
      chapChallenge,
    });
  }

  /**
   * Send an authentication request
   */
  public async authenticate(request: IClientAuthRequest): Promise<IClientAuthResponse> {
    await this.ensureConnected();

    const identifier = this.nextIdentifier();
    const attributes: Array<{ type: number | string; value: string | number | Buffer }> = [];

    // Add User-Name
    attributes.push({ type: ERadiusAttributeType.UserName, value: request.username });

    // Add NAS-IP-Address or NAS-Identifier
    if (this.options.nasIpAddress && this.options.nasIpAddress !== '0.0.0.0') {
      attributes.push({ type: ERadiusAttributeType.NasIpAddress, value: this.options.nasIpAddress });
    }
    if (this.options.nasIdentifier) {
      attributes.push({ type: ERadiusAttributeType.NasIdentifier, value: this.options.nasIdentifier });
    }

    // Add PAP password or CHAP credentials
    if (request.password !== undefined) {
      // PAP - password will be encrypted in createAccessRequest
      attributes.push({ type: ERadiusAttributeType.UserPassword, value: request.password });
    } else if (request.chapPassword) {
      // CHAP
      attributes.push({ type: ERadiusAttributeType.ChapPassword, value: request.chapPassword });
      if (request.chapChallenge) {
        attributes.push({ type: ERadiusAttributeType.ChapChallenge, value: request.chapChallenge });
      }
    }

    // Add optional attributes
    if (request.nasPort !== undefined) {
      attributes.push({ type: ERadiusAttributeType.NasPort, value: request.nasPort });
    }
    if (request.nasPortType !== undefined) {
      attributes.push({ type: ERadiusAttributeType.NasPortType, value: request.nasPortType });
    }
    if (request.serviceType !== undefined) {
      attributes.push({ type: ERadiusAttributeType.ServiceType, value: request.serviceType });
    }
    if (request.calledStationId) {
      attributes.push({ type: ERadiusAttributeType.CalledStationId, value: request.calledStationId });
    }
    if (request.callingStationId) {
      attributes.push({ type: ERadiusAttributeType.CallingStationId, value: request.callingStationId });
    }
    if (request.state) {
      attributes.push({ type: ERadiusAttributeType.State, value: request.state });
    }

    // Add custom attributes
    if (request.customAttributes) {
      attributes.push(...request.customAttributes);
    }

    // Create packet
    const packet = RadiusPacket.createAccessRequest(identifier, this.options.secret, attributes);

    // Extract request authenticator from packet (bytes 4-20)
    const requestAuthenticator = packet.subarray(4, 20);

    // Send and wait for response
    const responseBuffer = await this.sendRequest(
      identifier,
      packet,
      requestAuthenticator,
      this.options.authPort
    );

    // Verify response authenticator
    if (!RadiusAuthenticator.verifyResponseAuthenticator(
      responseBuffer,
      requestAuthenticator,
      this.options.secret
    )) {
      throw new Error('Invalid response authenticator');
    }

    // Parse response
    const response = RadiusPacket.decodeAndParse(responseBuffer);

    return this.buildAuthResponse(response);
  }

  /**
   * Send an accounting request
   */
  public async accounting(request: IClientAccountingRequest): Promise<IClientAccountingResponse> {
    await this.ensureConnected();

    const identifier = this.nextIdentifier();
    const attributes: Array<{ type: number | string; value: string | number | Buffer }> = [];

    // Add required attributes
    attributes.push({ type: ERadiusAttributeType.AcctStatusType, value: request.statusType });
    attributes.push({ type: ERadiusAttributeType.AcctSessionId, value: request.sessionId });

    // Add NAS identification
    if (this.options.nasIpAddress && this.options.nasIpAddress !== '0.0.0.0') {
      attributes.push({ type: ERadiusAttributeType.NasIpAddress, value: this.options.nasIpAddress });
    }
    if (this.options.nasIdentifier) {
      attributes.push({ type: ERadiusAttributeType.NasIdentifier, value: this.options.nasIdentifier });
    }

    // Add optional attributes
    if (request.username) {
      attributes.push({ type: ERadiusAttributeType.UserName, value: request.username });
    }
    if (request.nasPort !== undefined) {
      attributes.push({ type: ERadiusAttributeType.NasPort, value: request.nasPort });
    }
    if (request.nasPortType !== undefined) {
      attributes.push({ type: ERadiusAttributeType.NasPortType, value: request.nasPortType });
    }
    if (request.sessionTime !== undefined) {
      attributes.push({ type: ERadiusAttributeType.AcctSessionTime, value: request.sessionTime });
    }
    if (request.inputOctets !== undefined) {
      attributes.push({ type: ERadiusAttributeType.AcctInputOctets, value: request.inputOctets });
    }
    if (request.outputOctets !== undefined) {
      attributes.push({ type: ERadiusAttributeType.AcctOutputOctets, value: request.outputOctets });
    }
    if (request.inputPackets !== undefined) {
      attributes.push({ type: ERadiusAttributeType.AcctInputPackets, value: request.inputPackets });
    }
    if (request.outputPackets !== undefined) {
      attributes.push({ type: ERadiusAttributeType.AcctOutputPackets, value: request.outputPackets });
    }
    if (request.terminateCause !== undefined) {
      attributes.push({ type: ERadiusAttributeType.AcctTerminateCause, value: request.terminateCause });
    }
    if (request.calledStationId) {
      attributes.push({ type: ERadiusAttributeType.CalledStationId, value: request.calledStationId });
    }
    if (request.callingStationId) {
      attributes.push({ type: ERadiusAttributeType.CallingStationId, value: request.callingStationId });
    }

    // Add custom attributes
    if (request.customAttributes) {
      attributes.push(...request.customAttributes);
    }

    // Create packet
    const packet = RadiusPacket.createAccountingRequest(identifier, this.options.secret, attributes);

    // Extract request authenticator from packet
    const requestAuthenticator = packet.subarray(4, 20);

    // Send and wait for response
    const responseBuffer = await this.sendRequest(
      identifier,
      packet,
      requestAuthenticator,
      this.options.acctPort
    );

    // Verify response authenticator
    if (!RadiusAuthenticator.verifyResponseAuthenticator(
      responseBuffer,
      requestAuthenticator,
      this.options.secret
    )) {
      throw new Error('Invalid response authenticator');
    }

    // Parse response
    const response = RadiusPacket.decodeAndParse(responseBuffer);

    return {
      success: response.code === ERadiusCode.AccountingResponse,
      attributes: response.parsedAttributes,
      rawPacket: response,
    };
  }

  /**
   * Send accounting start
   */
  public async accountingStart(sessionId: string, username?: string): Promise<IClientAccountingResponse> {
    const { EAcctStatusType } = await import('../ts_server/index.js');
    return this.accounting({
      statusType: EAcctStatusType.Start,
      sessionId,
      username,
    });
  }

  /**
   * Send accounting stop
   */
  public async accountingStop(
    sessionId: string,
    options?: {
      username?: string;
      sessionTime?: number;
      inputOctets?: number;
      outputOctets?: number;
      terminateCause?: number;
    }
  ): Promise<IClientAccountingResponse> {
    const { EAcctStatusType } = await import('../ts_server/index.js');
    return this.accounting({
      statusType: EAcctStatusType.Stop,
      sessionId,
      ...options,
    });
  }

  /**
   * Send accounting interim update
   */
  public async accountingUpdate(
    sessionId: string,
    options?: {
      username?: string;
      sessionTime?: number;
      inputOctets?: number;
      outputOctets?: number;
    }
  ): Promise<IClientAccountingResponse> {
    const { EAcctStatusType } = await import('../ts_server/index.js');
    return this.accounting({
      statusType: EAcctStatusType.InterimUpdate,
      sessionId,
      ...options,
    });
  }

  private async ensureConnected(): Promise<void> {
    if (!this.isConnected) {
      await this.connect();
    }
  }

  private nextIdentifier(): number {
    this.currentIdentifier = (this.currentIdentifier + 1) % 256;
    return this.currentIdentifier;
  }

  private sendRequest(
    identifier: number,
    packet: Buffer,
    requestAuthenticator: Buffer,
    port: number
  ): Promise<Buffer> {
    return new Promise((resolve, reject) => {
      const pending: IPendingRequest = {
        identifier,
        requestAuthenticator,
        resolve,
        reject,
        retries: 0,
        packet,
        port,
      };

      this.pendingRequests.set(identifier, pending);
      this.sendWithRetry(pending);
    });
  }

  private sendWithRetry(pending: IPendingRequest): void {
    // Send packet
    this.socket!.send(pending.packet, pending.port, this.options.host, (err) => {
      if (err) {
        this.pendingRequests.delete(pending.identifier);
        pending.reject(err);
        return;
      }

      // Set timeout
      pending.timeoutId = setTimeout(() => {
        pending.retries++;
        if (pending.retries >= this.options.retries) {
          this.pendingRequests.delete(pending.identifier);
          pending.reject(new Error(`Request timed out after ${this.options.retries} retries`));
          return;
        }

        // Exponential backoff
        const delay = this.options.retryDelay * Math.pow(2, pending.retries - 1);
        setTimeout(() => {
          if (this.pendingRequests.has(pending.identifier)) {
            this.sendWithRetry(pending);
          }
        }, delay);
      }, this.options.timeout);
    });
  }

  private handleResponse(msg: Buffer): void {
    if (msg.length < 20) {
      return;
    }

    const identifier = msg.readUInt8(1);
    const pending = this.pendingRequests.get(identifier);

    if (!pending) {
      // Response for unknown request
      return;
    }

    // Clear timeout
    if (pending.timeoutId) {
      clearTimeout(pending.timeoutId);
    }

    // Remove from pending
    this.pendingRequests.delete(identifier);

    // Resolve with response
    pending.resolve(msg);
  }

  private buildAuthResponse(packet: any): IClientAuthResponse {
    const code = packet.code as ERadiusCode;
    const accepted = code === ERadiusCode.AccessAccept;
    const rejected = code === ERadiusCode.AccessReject;
    const challenged = code === ERadiusCode.AccessChallenge;

    // Extract common attributes
    let replyMessage: string | undefined;
    let sessionTimeout: number | undefined;
    let idleTimeout: number | undefined;
    let state: Buffer | undefined;
    let classAttr: Buffer | undefined;
    let framedIpAddress: string | undefined;
    let framedIpNetmask: string | undefined;
    const framedRoutes: string[] = [];

    for (const attr of packet.parsedAttributes) {
      switch (attr.type) {
        case ERadiusAttributeType.ReplyMessage:
          replyMessage = attr.value as string;
          break;
        case ERadiusAttributeType.SessionTimeout:
          sessionTimeout = attr.value as number;
          break;
        case ERadiusAttributeType.IdleTimeout:
          idleTimeout = attr.value as number;
          break;
        case ERadiusAttributeType.State:
          state = attr.rawValue;
          break;
        case ERadiusAttributeType.Class:
          classAttr = attr.rawValue;
          break;
        case ERadiusAttributeType.FramedIpAddress:
          framedIpAddress = attr.value as string;
          break;
        case ERadiusAttributeType.FramedIpNetmask:
          framedIpNetmask = attr.value as string;
          break;
        case ERadiusAttributeType.FramedRoute:
          framedRoutes.push(attr.value as string);
          break;
      }
    }

    return {
      code,
      accepted,
      rejected,
      challenged,
      replyMessage,
      sessionTimeout,
      idleTimeout,
      state,
      class: classAttr,
      framedIpAddress,
      framedIpNetmask,
      framedRoutes: framedRoutes.length > 0 ? framedRoutes : undefined,
      attributes: packet.parsedAttributes,
      rawPacket: packet,
    };
  }
}

export default RadiusClient;