MQTT trigger script template

/**

 * MQTT Preprocessor Function

 * 

 * This function is called when an MQTT message is received, BEFORE your main handler function.

 * It allows you to transform or validate the incoming data before processing.

 * 

 * Flow: MQTT message → preprocessor function → main function

 * 

 * IMPORTANT: The object you return from this preprocessor determines the parameters passed to your main function:

 * - If you return {a: 1, b: 2}, then main will be called as main(a, b)

 * - If you return {payload}, then main will be called as main(payload)

 * - If you return nothing or {}, then main will only receive the raw payload as main(payload)

 * 

 * @param wm_trigger - Information about the trigger source (MQTT in this case)

 * @param payload - The raw bytes of the MQTT message (as Uint8Array)

 * @returns An object with the arguments to pass to the main function

 */

export async function preprocessor(

  wm_trigger: {

    kind: 'http' | 'email' | 'webhook' | 'websocket' | 'kafka' | 'nats' | 'postgres' | 'sqs' | 'mqtt',

    mqtt: {

      topic: string,

      retain: boolean,

      pkid: number,

      qos: number,

      v5?: {

        payload_format_indicator?: number,

        topic_alias?: number,

        response_topic?: string,

        correlation_data?: Array<number>,

        user_properties?: Array<[string, string]>,

        subscription_identifiers?: Array<number>,

        content_type?: string

      }

    }

  },

  /**

   * The raw message payload from the MQTT broker as bytes

   * This preprocessor function is called before your main function

   * The object you return from this function will be passed as arguments to your main function

   * You can transform the payload here before it reaches your main handler

   */

  payload: Uint8Array,

) {

  return {

    content_type: wm_trigger.mqtt.v5?.content_type,

    payload,

    payloadAsString: new TextDecoder().decode(payload)

  }

}

/**

 * Main Function - Handles MQTT Messages

 * 

 * This function receives arguments based on what was returned by the preprocessor:

 * - If preprocessor returns {payload, content_type}, main is called as main(payload, content_type)

 * - If preprocessor returns {payload, someValue}, main is called as main(payload, someValue)

 * - If preprocessor returns {}, main is called as main(payload) with the raw payload only

 * 

 * IMPORTANT: 

 * - The 'payload' parameter will always be available to the main function

 * - Any other parameters only exist if explicitly returned from the preprocessor

 * - There are no "special" parameters - all additional parameter names come directly 

 *   from what you return in the preprocessor

 * 

 * @param content_type - The content type from MQTT v5 properties if available

 * @param payload - The raw binary payload from MQTT

 * @param payloadAsString - The payload converted to a string

 * @returns The result of processing the MQTT message

 */

export async function main(payload: string, content_type?: string, payloadAsString: string) {

}