WebSocket trigger script with preprocessor template

/**

 * General Trigger Preprocessor

 *

 * ⚠️ This function runs BEFORE the main function.

 *

 * It processes raw trigger data (e.g., MQTT, HTTP, SQS, WebSocket) before passing it to main().

 * Common tasks:

 * - Convert binary payloads to string/JSON

 * - Extract metadata

 * - Filter messages

 * - Add timestamps/context

 *

 * The returned object determines main() parameters:

 * - {a: 1, b: 2} → main(a, b)

 * - {msg} → main(msg)

 *

 * @param event - Trigger data (e.g., MQTT, HTTP, SQS, WebSocket)

 * @returns Processed data for main()

 */

export async function preprocessor(

  event: {

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

    msg: string

    url: string // The WebSocket URL

  },

) {

  if (event.kind === 'websocket') {

    let data;

    try {

      // Assuming the message received is a JSON value

      data = JSON.parse(event.msg);

    } catch (error) {

      throw new Error("Failed to parse WebSocket message as JSON");

    }

    return {

      msg: event.msg,

      data,

    };

  }

  throw new Error(`Expected websocket trigger kind, got: ${event.kind}`);

}

/**

 * Main Function - Handles processed trigger events

 *

 * ⚠️ Called AFTER preprocessor(), with its return values.

 *

 * @param msg - Raw message content

 * @param data - Parsed JSON data from the WebSocket message

 */

export async function main(

  msg: string,

  data: any,

) {

  // Implement the main function logic here

}