import { randomUUID } from "crypto";
import type { MqttClient } from "mqtt";
import { errorResponse } from "../messages/build.js";
import { AlexaErrors } from "../messages/errors.js";
import type { AlexaError } from "../messages/errors.js";
import type { ErrorResponseMessage } from "../messages/types.js";

/** An ErrorResponse as 1.x builds it: device.getErrorMessage(token), setErrorMessage(), send(). */
export class AlexaErrorResponse {
  // Sent when setErrorMessage() was not called: 1.x published an empty payload, which is no ErrorResponse to Alexa
  private error: AlexaError = AlexaErrors.of("INTERNAL_ERROR", "the device answered with an error and did not say which");
  private namespace?: string;
  // One id for the message, however often toJSON() is called
  private readonly messageId = randomUUID();
  /** Where a failed publish is reported (set by the Device that built this message, 1.5.2): send() never rejects. */
  public onPublishError?: (err: Error) => void;

  constructor(
    private readonly correlationToken: string,
    private readonly rootTopic: string,
    private readonly endpointId: string,
    private readonly mqttClient: MqttClient
  ) {}

  /**
   * The error to answer with. otherParams are the fields the type adds to the payload (validRange). The header
   * carries the namespace the type is documented under, Alexa.ThermostatController for THERMOSTAT_IS_OFF;
   * options.namespace names another.
   */
  setErrorMessage(
    type: string,
    message: string,
    otherParams: Record<string, any> = {},
    options: { namespace?: string } = {}
  ): void {
    this.error = AlexaErrors.of(type, message, otherParams);
    this.namespace = options.namespace;
  }

  toJSON(): ErrorResponseMessage {
    const { type, alexaMessage, extra } = this.error;
    return errorResponse({
      endpointId: this.endpointId,
      messageId: this.messageId,
      correlationToken: this.correlationToken,
      type,
      message: alexaMessage,
      extra,
      namespace: this.namespace ?? this.error.namespace,
    });
  }

  /** Resolves with the topic published to, or "" when the publish failed. Never rejects. */
  send(sendAsync = false): Promise<string> {
    const topic = `${this.rootTopic}/${this.endpointId}/${sendAsync ? "deferredResponse" : "alexaResponce"}`; // "alexaResponce" is how Alex2MQTT and Alex2ESP spell the topic
    return new Promise((resolve) => {
      this.mqttClient.publish(topic, JSON.stringify(this.toJSON()), (err) => {
        if (!err) return resolve(topic);
        if (this.onPublishError) this.onPublishError(err); // -> the bridge's "error" event (when somebody listens)
        resolve(""); // 1.5.1 rejected here, and an un-caught send() then killed the host on any broker hiccup
      });
    });
  }
}