Add messaging & messaging-internal libraries (#15711)

libs/messaging/src/message.sender.ts

@@ -0,0 +1,65 @@
+import { CommandDefinition } from "./types";
+
+class MultiMessageSender implements MessageSender {
+  constructor(private readonly innerMessageSenders: MessageSender[]) {}
+
+  send<T extends Record<string, unknown>>(
+    commandDefinition: string | CommandDefinition<T>,
+    payload: Record<string, unknown> | T = {},
+  ): void {
+    for (const messageSender of this.innerMessageSenders) {
+      messageSender.send(commandDefinition, payload);
+    }
+  }
+}
+
+export abstract class MessageSender {
+  /**
+   * A method for sending messages in a type safe manner. The passed in command definition
+   * will require you to provide a compatible type in the payload parameter.
+   *
+   * @example
+   * const MY_COMMAND = new CommandDefinition<{ test: number }>("myCommand");
+   *
+   * this.messageSender.send(MY_COMMAND, { test: 14 });
+   *
+   * @param commandDefinition
+   * @param payload
+   */
+  abstract send<T extends Record<string, unknown>>(
+    commandDefinition: CommandDefinition<T>,
+    payload: T,
+  ): void;
+
+  /**
+   * A legacy method for sending messages in a non-type safe way.
+   *
+   * @remarks Consider defining a {@link CommandDefinition} and passing that in for the first parameter to
+   * get compilation errors when defining an incompatible payload.
+   *
+   * @param command The string based command of your message.
+   * @param payload Extra contextual information regarding the message. Be aware that this payload may
+   *   be serialized and lose all prototype information.
+   */
+  abstract send(command: string, payload?: Record<string, unknown>): void;
+
+  /** Implementation of the other two overloads, read their docs instead. */
+  abstract send<T extends Record<string, unknown>>(
+    commandDefinition: CommandDefinition<T> | string,
+    payload: T | Record<string, unknown>,
+  ): void;
+
+  /**
+   * A helper method for combine multiple {@link MessageSender}'s.
+   * @param messageSenders The message senders that should be combined.
+   * @returns A message sender that will relay all messages to the given message senders.
+   */
+  static combine(...messageSenders: MessageSender[]) {
+    return new MultiMessageSender(messageSenders);
+  }
+
+  /**
+   * A helper property for creating a {@link MessageSender} that sends to nowhere.
+   */
+  static readonly EMPTY: MessageSender = new MultiMessageSender([]);
+}