import { TransportError } from "../exceptions";
import { IncomingRequestMessage } from "../messages";
import { Timers } from "../timers";
import { Transport } from "../transport";
import { ServerTransaction } from "./server-transaction";
import { TransactionState } from "./transaction-state";
import { ServerTransactionUser } from "./transaction-user";

/**
 * Non-INVITE Server Transaction.
 * @remarks
 * https://tools.ietf.org/html/rfc3261#section-17.2.2
 * @public
 */
export class NonInviteServerTransaction extends ServerTransaction {
  private lastResponse: string | undefined;
  private J: any | undefined;

  /**
   * Constructor.
   * After construction the transaction will be in the "trying": state and the transaction
   * `id` will equal the branch parameter set in the Via header of the incoming request.
   * https://tools.ietf.org/html/rfc3261#section-17.2.2
   * @param request - Incoming Non-INVITE request from the transport.
   * @param transport - The transport.
   * @param user - The transaction user.
   */
  constructor(request: IncomingRequestMessage, transport: Transport, user: ServerTransactionUser) {
    super(
      request,
      transport,
      user,
      TransactionState.Trying,
      "sip.transaction.nist"
    );
  }

  /**
   * Destructor.
   */
  public dispose(): void {
    if (this.J) {
      clearTimeout(this.J);
      this.J = undefined;
    }
    super.dispose();
  }

  /** Transaction kind. Deprecated. */
  get kind(): string {
    return "nist";
  }

  /**
   * Receive requests from transport matching this transaction.
   * @param request - Request matching this transaction.
   */
  public receiveRequest(request: IncomingRequestMessage): void {
    switch (this.state) {
      case TransactionState.Trying:
        // Once in the "Trying" state, any further request retransmissions are discarded.
        // https://tools.ietf.org/html/rfc3261#section-17.2.2
        break;
      case TransactionState.Proceeding:
        // If a retransmission of the request is received while in the "Proceeding" state,
        // the most recently sent provisional response MUST be passed to the transport layer for retransmission.
        // https://tools.ietf.org/html/rfc3261#section-17.2.2
        if (!this.lastResponse) {
          throw new Error("Last response undefined.");
        }
        this.send(this.lastResponse).catch((error: TransportError) => {
          this.logTransportError(error, "Failed to send retransmission of provisional response.");
        });
        break;
      case TransactionState.Completed:
        // While in the "Completed" state, the server transaction MUST pass the final response to the transport
        // layer for retransmission whenever a retransmission of the request is received. Any other final responses
        // passed by the TU to the server transaction MUST be discarded while in the "Completed" state.
        // https://tools.ietf.org/html/rfc3261#section-17.2.2
        if (!this.lastResponse) {
          throw new Error("Last response undefined.");
        }
        this.send(this.lastResponse).catch((error: TransportError) => {
          this.logTransportError(error, "Failed to send retransmission of final response.");
        });
        break;
      case TransactionState.Terminated:
        break;
      default:
        throw new Error(`Invalid state ${this.state}`);
    }
  }

  /**
   * Receive responses from TU for this transaction.
   * @param statusCode - Status code of repsonse. 101-199 not allowed per RFC 4320.
   * @param response - Response to send.
   */
  public receiveResponse(statusCode: number, response: string): void {
    if (statusCode < 100 || statusCode > 699) {
      throw new Error(`Invalid status code ${statusCode}`);
    }

    // An SIP element MUST NOT send any provisional response with a
    // Status-Code other than 100 to a non-INVITE request.
    // An SIP element MUST NOT respond to a non-INVITE request with a
    // Status-Code of 100 over any unreliable transport, such as UDP,
    // before the amount of time it takes a client transaction's Timer E to be reset to T2.
    // An SIP element MAY respond to a non-INVITE request with a
    // Status-Code of 100 over a reliable transport at any time.
    // https://tools.ietf.org/html/rfc4320#section-4.1
    if (statusCode > 100 && statusCode <= 199) {
      throw new Error("Provisional response other than 100 not allowed.");
    }

    switch (this.state) {
      case TransactionState.Trying:
        // While in the "Trying" state, if the TU passes a provisional response
        // to the server transaction, the server transaction MUST enter the "Proceeding" state.
        // The response MUST be passed to the transport layer for transmission.
        // https://tools.ietf.org/html/rfc3261#section-17.2.2
        this.lastResponse = response;
        if (statusCode >= 100 && statusCode < 200) {
          this.stateTransition(TransactionState.Proceeding);
          this.send(response).catch((error: TransportError) => {
            this.logTransportError(error, "Failed to send provisional response.");
          });
          return;
        }
        if (statusCode >= 200 && statusCode <= 699) {
          this.stateTransition(TransactionState.Completed);
          this.send(response).catch((error: TransportError) => {
            this.logTransportError(error, "Failed to send final response.");
          });
          return;
        }
        break;
      case TransactionState.Proceeding:
        // Any further provisional responses that are received from the TU while
        // in the "Proceeding" state MUST be passed to the transport layer for transmission.
        // If the TU passes a final response (status codes 200-699) to the server while in
        // the "Proceeding" state, the transaction MUST enter the "Completed" state, and
        // the response MUST be passed to the transport layer for transmission.
        // https://tools.ietf.org/html/rfc3261#section-17.2.2
        this.lastResponse = response;
        if (statusCode >= 200 && statusCode <= 699) {
          this.stateTransition(TransactionState.Completed);
          this.send(response).catch((error: TransportError) => {
            this.logTransportError(error, "Failed to send final response.");
          });
          return;
        }
        break;
      case TransactionState.Completed:
        // Any other final responses passed by the TU to the server
        // transaction MUST be discarded while in the "Completed" state.
        // https://tools.ietf.org/html/rfc3261#section-17.2.2
        return;
      case TransactionState.Terminated:
        break;
      default:
        throw new Error(`Invalid state ${this.state}`);
    }

    const message =
      `Non-INVITE server transaction received unexpected ${statusCode} response from TU while in state ${this.state}.`;
    this.logger.error(message);
    throw new Error(message);
  }

  /**
   * First, the procedures in [4] are followed, which attempt to deliver the response to a backup.
   * If those should all fail, based on the definition of failure in [4], the server transaction SHOULD
   * inform the TU that a failure has occurred, and SHOULD transition to the terminated state.
   * https://tools.ietf.org/html/rfc3261#section-17.2.4
   */
  protected onTransportError(error: Error): void {
    if (this.user.onTransportError) {
      this.user.onTransportError(error);
    }
    this.stateTransition(TransactionState.Terminated, true);
  }

  /** For logging. */
  protected typeToString(): string {
    return "non-INVITE server transaction";
  }

  private stateTransition(newState: TransactionState, dueToTransportError = false): void {
    // Assert valid state transitions.
    const invalidStateTransition = () => {
      throw new Error(`Invalid state transition from ${this.state} to ${newState}`);
    };

    switch (newState) {
      case TransactionState.Trying:
        invalidStateTransition();
        break;
      case TransactionState.Proceeding:
        if (this.state !== TransactionState.Trying) {
          invalidStateTransition();
        }
        break;
      case TransactionState.Completed:
        if (this.state !== TransactionState.Trying && this.state !== TransactionState.Proceeding) {
          invalidStateTransition();
        }
        break;
      case TransactionState.Terminated:
        if (this.state !== TransactionState.Proceeding && this.state !== TransactionState.Completed) {
          if (!dueToTransportError) {
            invalidStateTransition();
          }
        }
        break;
      default:
        invalidStateTransition();
    }

    // When the server transaction enters the "Completed" state, it MUST set Timer J to fire
    // in 64*T1 seconds for unreliable transports, and zero seconds for reliable transports.
    // https://tools.ietf.org/html/rfc3261#section-17.2.2
    if (newState === TransactionState.Completed) {
      this.J = setTimeout(() => this.timer_J(), Timers.TIMER_J);
    }

    // The server transaction MUST be destroyed the instant it enters the "Terminated" state.
    // https://tools.ietf.org/html/rfc3261#section-17.2.2
    if (newState === TransactionState.Terminated) {
      this.dispose();
    }

    this.setState(newState);
  }

  /**
   * The server transaction remains in this state until Timer J fires,
   * at which point it MUST transition to the "Terminated" state.
   * https://tools.ietf.org/html/rfc3261#section-17.2.2
   */
  private timer_J(): void {
    this.logger.debug(`Timer J expired for NON-INVITE server transaction ${this.id}.`);
    if (this.state === TransactionState.Completed) {
      this.stateTransition(TransactionState.Terminated);
    }
  }
}