import {
  SNSClient,
  PublishCommand,
  PublishCommandOutput,
  PublishCommandInput,
} from '@aws-sdk/client-sns'
import sha1 from 'sha1'
//reusable client
/**
 * A variable that holds the connection to the SNS client for publishing messages.
 * @type {SNSClient | null}
 */
// eslint-disable-next-line no-var
let PUBLISHER_CONN: SNSClient | null = null
/**
 * The connection hash for the publisher. It is initially set to null.
 * @type {string | null}
 */
// eslint-disable-next-line no-var
let PUBLISHER_CONN_HASH: string | null = null

/**
 * Represents the configuration options for a publisher.
 * @typedef {Object} PublisherConfig
 * @property {string} [region] - The region where the publisher is located.
 */
export type PublisherConfig = {
  region?: string
}

/**
 * Represents a publisher that can publish messages to an SNS topic.
 */
export default class Publisher {
  /**
   * The region of the object or entity.
   * @private
   * @type {string}
   */
  private region: string | undefined

  /**
   * Constructs a new instance of the Publisher class.
   * @param {PublisherConfig} [config] - The configuration object for the Publisher.
   * @returns None
   */
  constructor(config?: PublisherConfig) {
    if (config && config.region) {
      this.region = config.region
      // console.debug(`Using region: ${this.region}`);
    }
  }

  /**
   * Publishes a message on a specified topic.
   * @param {any} messageObject - The message object to be published.
   * @param {string} topic - The ARN of the topic to publish the message to.
   * @param {object} [additionalProps] - Additional properties to include in the publish command.
   * @returns {Promise<PublishCommandOutput>} - A promise that resolves to the response from the publish command.
   */
  public async publishOnTopic(
    messageObject: any,
    topic: string,
    additionalProps?: object
  ): Promise<PublishCommandOutput | undefined> {
    let resp: undefined | PublishCommandOutput = undefined
    try {
      this.connect()
      //Send to SNS
      const params: PublishCommandInput = {
        Message: JSON.stringify(messageObject),
        TopicArn: topic,
        ...(additionalProps ? additionalProps : {}),
      }
      resp = await PUBLISHER_CONN!.send(new PublishCommand(params))
    } catch (e) {
      console.error(`Error while publishing into topic ${topic} with error: ${e}`)
    }
    console.debug('Publisher resp', resp)
    return resp
  }

  /**
   * Publishes a message on a specified topic.
   * @param {string} message - The SMS message to publish.
   * @param {string} phone - The phone number to publish the message to.
   * @returns {Promise<PublishCommandOutput>} - A promise that resolves to the response from the publish command.
   */
  public async publishSMS(
    message: string,
    phone: string
  ): Promise<PublishCommandOutput | undefined> {
    let resp: undefined | PublishCommandOutput = undefined
    try {
      this.connect()
      //Send to SNS
      const params: PublishCommandInput = {
        Message: message,
        PhoneNumber: phone,
      }
      resp = await PUBLISHER_CONN!.send(new PublishCommand(params))
    } catch (e) {
      console.error(`Error while publishing SMS ${message} with error: ${e}`)
    }
    console.debug('Publisher resp', resp)
    return resp
  }

  /**
   * Establishes a connection to the SNS client if it does not already exist or if the region has changed.
   * @returns None
   */
  private connect(): void {
    if ((!PUBLISHER_CONN && !PUBLISHER_CONN_HASH) || PUBLISHER_CONN_HASH != sha1(this.region)) {
      PUBLISHER_CONN = new SNSClient({
        apiVersion: '2010-03-31',
        region: this.region,
      })
      PUBLISHER_CONN_HASH = sha1(this.region).toString()
    }
  }
}