Implement websocket server

src/http/response/api.ts

@@ -1,7 +1,12 @@
 /**
  * Base type for an API response format.
  */
+import {BaseSerializer, Event, ObjectSerializer} from '../../support/bus'
+import {Awaitable, ErrorWithContext, hasOwnProperty, JSONState, uuid4} from '../../util'
+
 export interface APIResponse<T> {
+    eventName?: string,
+    eventUuid?: string,
     success: boolean,
     message?: string,
     data?: T,
@@ -12,6 +17,61 @@ export interface APIResponse<T> {
     }
 }
 
+export function isAPIResponse(what: unknown): what is APIResponse<unknown> {
+    return typeof what === 'object' && what !== null
+        && hasOwnProperty(what, 'success')
+        && typeof what.success === 'boolean'
+        && (!hasOwnProperty(what, 'message') || typeof what.message === 'string')
+        && (!hasOwnProperty(what, 'error') || (
+            typeof what.error === 'object' && what.error !== null
+                && hasOwnProperty(what.error, 'name') && typeof what.error.name === 'string'
+                && hasOwnProperty(what.error, 'message') && typeof what.error.message === 'string'
+                && (!hasOwnProperty(what.error, 'stack') || (
+                    Array.isArray(what.error.stack) && what.error.stack.every(x => typeof x === 'string')
+                )
+                )
+        )
+        )
+}
+
+export function apiEvent<T>(response: APIResponse<T>): APIResponse<T> & Event {
+    if ( !response.eventName ) {
+        response.eventName = '@extollo/lib:APIResponse'
+    }
+
+    if ( !response.eventUuid ) {
+        response.eventUuid = uuid4()
+    }
+
+    return response as APIResponse<T> & Event
+}
+
+/**
+ * Serializer implementation that can encode/decode APIResponse objects.
+ */
+@ObjectSerializer()
+export class APIResponseSerializer extends BaseSerializer<APIResponse<unknown>, JSONState> {
+    protected decodeSerial(serial: JSONState): Awaitable<APIResponse<unknown>> {
+        if ( isAPIResponse(serial) ) {
+            return serial
+        }
+
+        throw new ErrorWithContext('Could not decode API response: object is malformed')
+    }
+
+    protected encodeActual(actual: APIResponse<unknown>): Awaitable<JSONState> {
+        return actual as unknown as JSONState
+    }
+
+    protected getName(): string {
+        return '@extollo/lib:APIResponseSerializer'
+    }
+
+    matchActual(some: APIResponse<unknown>): boolean {
+        return isAPIResponse(some)
+    }
+}
+
 /**
  * Formats a mesage as a successful API response.
  * @param {string} displayMessage
@@ -56,7 +116,7 @@ export function many<T>(records: T[]): APIResponse<{records: T[], total: number}
  * @return APIResponse
  * @param thrownError
  */
-export function error(thrownError: string | Error): APIResponse<void> {
+export function error(thrownError: string | Error): APIResponse<undefined> {
     if ( typeof thrownError === 'string' ) {
         return {
             success: false,