Problem

msgbuf currently only generates Java classes from .proto files. For web applications using SSE (Server-Sent Events) or WebSocket protocols, the client-side TypeScript/JavaScript deserialization and dispatch code must be written by hand. This is repetitive, error-prone, and defeats the purpose of a code generator.

Use Case

A server sends SSE events defined in a .proto file. The Java server code is generated, but the TypeScript client code must be manually written:

// Currently hand-written for each message type:
function dispatchSSEEvent(json: any): void {
    switch (json._type) {
        case "PatchEvent":
            handlePatch(json.controlId, json.patch);
            break;
        case "StateEvent":
            handleState(json.controlId, json.state);
            break;
        // ... every new event type requires manual additions
    }
}

Proposed Solution

Add a TypeScript/JavaScript code generation target to msgbuf. From the same .proto file, generate:

1. TypeScript interfaces/classes with typed properties
2. JSON deserialization (fromJson / readFrom methods)
3. JSON serialization (toJson / writeTo methods)
4. Polymorphic dispatch for abstract message hierarchies (automatic type-tag based deserialization)

Example generated output:

// Generated from sse.proto
export abstract class SSEEvent {
    static fromJson(reader: JsonReader): SSEEvent { /* dispatch by _type */ }
}

export class PatchEvent extends SSEEvent {
    controlId: string;
    patch: string;

    static fromJson(reader: JsonReader): PatchEvent { ... }
    toJson(writer: JsonWriter): void { ... }
}

This would ensure client and server are always in sync and eliminate an entire class of serialization bugs.