import { Injectable, Inject } from '@angular/core';

import { Subscription, Observable, Subject } from 'rxjs';
import { share, switchMap, retryWhen, delay, finalize } from 'rxjs/operators';

import { QueueingSubject } from 'queueing-subject';

import {
  makeWebSocketObservable,
  GetWebSocketResponses,
  NormalClosureMessage
} from '@ucap-webmessenger/web-socket';

import { _MODULE_CONFIG } from '../types/token';
import { ModuleConfig } from '../types/module-config';
import { PacketBody } from '../protocols/packet';
import {
  PacketBodyValueDivider,
  PacketBodyDivider
} from '../types/packet-body-divider';
import { PacketBodyValue } from '../types/packet-body-value.type';
import { SSVC_TYPE_ERROR_RES, ServerErrorCode } from '../types/service';
import { ProtocolMessage } from '../protocols/protocol';

import { NGXLogger } from 'ngx-logger';

interface RequestState {
  subject: Subject<ProtocolMessage>;
  request: {
    serviceType: number;
    subServiceType: number;
    bodyList: PacketBody[];
  };
}

@Injectable({
  providedIn: 'root'
})
export class ProtocolService {
  // tslint:disable-next-line: variable-name
  private _requestId: number | null = null;
  private readonly pendingRequests: Map<number, RequestState>;
  private readonly input$: QueueingSubject<string>;
  private socket$: Observable<GetWebSocketResponses<any>>;
  private messages$: Observable<any>;
  private messagesSubscription: Subscription | null = null;
  private serverMessageSubject: Subject<ProtocolMessage> | null = null;
  private serverMessage$: Observable<ProtocolMessage> | null = null;

  constructor(
    @Inject(_MODULE_CONFIG) private moduleConfig: ModuleConfig,
    private logger: NGXLogger
  ) {
    this.pendingRequests = new Map();
    this.input$ = new QueueingSubject<string>();
    this.serverMessageSubject = new Subject();
    this.serverMessage$ = this.serverMessageSubject
      .asObservable()
      .pipe(share());
  }

  public connect(serverIp: string | null = null): Observable<void> {
    return new Observable<void>(subscriber => {
      try {
        this.socket$ = makeWebSocketObservable(
          `${this.moduleConfig.urls.base}${serverIp ? serverIp : ''}`
        );
        this.messages$ = this.socket$.pipe(
          switchMap(getResponses => {
            subscriber.next();
            return getResponses(this.input$);
          }),
          retryWhen(errors =>
            errors.pipe(delay(this.moduleConfig.reconnect.delay))
          ),
          share()
        );

        this.messagesSubscription = this.messages$.subscribe(
          (message: string) => {
            const arg = message.split(PacketBodyDivider);
            if (2 > arg.length) {
              // OnError(3);
              return;
            }

            const res = this.decodePacket(arg);

            let requestState: RequestState | null = null;
            if (res.requestId) {
              requestState = this.pendingRequests.get(res.requestId);
            }

            if (SSVC_TYPE_ERROR_RES === res.message.subServiceType) {
              const errorCode: ServerErrorCode = res.message
                .bodyList[0] as ServerErrorCode;

              if (requestState) {
                requestState.subject.error(errorCode);
              }
              return;
            }

            if (
              requestState &&
              requestState.request.serviceType === res.message.serviceType
            ) {
              requestState.subject.next(res.message);
              return;
            }

            this.serverMessageSubject.next(res.message);
          },
          (error: Error) => {
            const { message } = error;
            if (message === NormalClosureMessage) {
              this.logger.info(
                'server closed the websocket connection normally'
              );
            } else {
              this.logger.error(
                'socket was disconnected due to error:',
                message
              );
            }
          },
          () => {
            // The clean termination only happens in response to the last
            // subscription to the observable being unsubscribed, any
            // other closure is considered an error.
            this.logger.info(
              'the connection was closed in response to the user'
            );
          }
        );
      } catch (error) {
        subscriber.error(error);
      }
    });
  }

  public disconnect(): void {
    this.messagesSubscription.unsubscribe();
  }

  public get serverMessage(): Observable<ProtocolMessage> {
    return this.serverMessage$;
  }

  public call(
    serviceType: number | null,
    subServiceType: number | null,
    ...bodyList: PacketBody[]
  ): Observable<ProtocolMessage> {
    return this.sendInternal(true, serviceType, subServiceType, bodyList);
  }

  public send(
    serviceType: number,
    subServiceType: number,
    ...bodyList: PacketBody[]
  ): void {
    this.sendInternal(false, serviceType, subServiceType, bodyList);
  }

  private sendInternal(
    hasResponse: boolean,
    serviceType: number,
    subServiceType: number,
    bodyList: PacketBody[]
  ): Observable<ProtocolMessage> | undefined {
    let packet: string;
    let responseSubject: Subject<ProtocolMessage> | null = null;

    if (hasResponse) {
      const requestId = this.requestId;

      packet = this.encodePacket(serviceType, subServiceType, [
        ...bodyList,
        { type: PacketBodyValue.RequestId, value: requestId }
      ]);

      responseSubject = new Subject<ProtocolMessage>().pipe(
        finalize(() => {
          if (this.pendingRequests.has(requestId)) {
            this.pendingRequests.delete(requestId);
          }
          this.logger.debug(
            'ProtocolService::pendingRequests.size',
            this.pendingRequests.size
          );
        })
      ) as Subject<ProtocolMessage>;

      this.pendingRequests.set(requestId, {
        subject: responseSubject,
        request: { serviceType, subServiceType, bodyList }
      });
    } else {
      packet = this.encodePacket(serviceType, subServiceType, bodyList);
    }

    this.input$.next(packet);

    return responseSubject ? responseSubject.asObservable() : undefined;
  }

  private get requestId() {
    if (
      null === this._requestId ||
      this.moduleConfig.requestId.max < this._requestId
    ) {
      this._requestId = this.moduleConfig.requestId.min;
    }

    return this._requestId++;
  }

  private decodePacket(
    arg: string[]
  ): { requestId: number; message: ProtocolMessage } | null {
    const cmdArg = arg[0].split(PacketBodyValueDivider);
    if (2 > cmdArg.length) {
      // OnError(3);
      return null;
    }

    const serviceType = Number(cmdArg[0]);
    const subServiceType = Number(cmdArg[1]);

    const seqArg = arg[1].split(PacketBodyValueDivider);
    if (2 > seqArg.length) {
      // OnError(3);
      return null;
    }
    const senderSeq = Number(seqArg[0]);

    const bodyList: any[] = [];
    let requestId: number | null = null;

    for (let i = 2; i < arg.length; i++) {
      const bodyArg = arg[i].split(PacketBodyValueDivider);
      if (2 > bodyArg.length) {
        // OnError(3);
        return null;
      }

      const valueType: PacketBodyValue = bodyArg[0] as PacketBodyValue;
      const value = bodyArg[1];

      switch (valueType) {
        case PacketBodyValue.None:
          bodyList.push(value);
          break;
        case PacketBodyValue.Binary:
          bodyList.push(value);
          break;
        case PacketBodyValue.Integer:
          bodyList.push(Number(value));
          break;
        case PacketBodyValue.String:
          bodyList.push(value);
          break;
        case PacketBodyValue.EncodedString:
          bodyList.push(value);
          break;
        case PacketBodyValue.MultiByteString:
          bodyList.push(value);
          break;
        case PacketBodyValue.WideString:
          bodyList.push(value);
          break;
        case PacketBodyValue.IuId:
          bodyList.push(value);
          break;
        case PacketBodyValue.RequestId:
          requestId = parseInt(value, 10);
          break;
        default:
          break;
      }
    }

    return {
      requestId,
      message: {
        serviceType,
        subServiceType,
        senderSeq,
        bodyList
      }
    };
  }

  private encodePacket(
    serviceType: number | null,
    subServiceType: number | null,
    bodyList: PacketBody[] = []
  ): string {
    const packet: string[] = [];
    packet.push(serviceType ? serviceType.toString() : '0');
    packet.push(PacketBodyValueDivider);
    packet.push(subServiceType ? subServiceType.toString() : '0');
    packet.push(PacketBodyDivider);

    for (const body of bodyList) {
      packet.push(body.type);
      packet.push(PacketBodyValueDivider);

      switch (body.type) {
        case PacketBodyValue.None:
          packet.push(body.value);
          break;
        case PacketBodyValue.Binary:
          packet.push(body.value);
          break;
        case PacketBodyValue.Integer:
          packet.push(String(body.value));
          break;
        case PacketBodyValue.String:
          packet.push(body.value);
          break;
        case PacketBodyValue.EncodedString:
          packet.push(body.value);
          break;
        case PacketBodyValue.MultiByteString:
          packet.push(body.value);
          break;
        case PacketBodyValue.WideString:
          packet.push(body.value);
          break;
        case PacketBodyValue.IuId:
          packet.push(body.value);
          break;
        case PacketBodyValue.RequestId:
          packet.push(String(body.value));
          break;
        default:
          break;
      }
      packet.push(PacketBodyDivider);
    }

    return packet.join('');
  }
}