Added Payload class to encode/decode Thrift CompactProtocol payloads

Author: Nordskog

src/mqtt/payloads/Payload.ts

@@ -0,0 +1,45 @@
+import { Thrift, TCompactProtocol, TBufferedTransport } from 'thrift'
+
+export default abstract class Payload {
+ /**
+  * Write this payload into the specified stream
+  */
+  encode (proto: TCompactProtocol): Promise<void> {
+    return null
+  }
+
+  /**
+   * Decodes thrift buffer into this payload
+   */
+  decode (data: Buffer): Promise<void> {
+    return null
+  }
+
+  /**
+   * Get topic this payload should published to
+   * Only single-level topics have been observed,
+   * but mqtt works with multiple, possibly dynamically
+   * generated topics.
+   */
+  getTopic (): string {
+        // Maybe thrown?
+    return null
+  }
+
+  /**
+   * Static convenience method for writing a payload to a
+   * buffered transport and returning it as a buffer
+   */
+  static encodePayload (payload: Payload): Promise<Buffer> {
+    return new Promise<Buffer>((resolve, reject) => {
+      const trans = new TBufferedTransport(null, (msg, seqid) => {
+        resolve(msg)
+      })
+
+      const proto = new TCompactProtocol(trans)
+      payload.encode(proto)
+
+      proto.flush()
+    })
+  }
+}

src/mqtt/payloads/index.ts

@@ -0,0 +1,5 @@
+import Payload from './Payload'
+
+export { Payload }
+
+export const encodePayload = Payload.encodePayload