galaxy-game/ui/wasm/main.go

// Command wasm is the TinyGo WebAssembly entry point for the Galaxy UI
// client. It exposes a small "compute boundary" API on
// `globalThis.galaxyCore` so the TypeScript-side `WasmCore` adapter can
// call into the Go canonical-bytes serializer and signature verifier
// without duplicating the contract in JavaScript.
//
// Public surface (all functions live under `globalThis.galaxyCore`):
//
//   - signRequest(fields)                        -> Uint8Array
//     Returns the canonical bytes for a v1 request envelope. The actual
//     Ed25519 signing happens outside WASM (Phase 6 introduces WebCrypto
//     with non-exportable keys).
//   - verifyResponse(publicKey, signature, fields) -> boolean
//   - verifyEvent(publicKey, signature, fields)    -> boolean
//   - verifyPayloadHash(payloadBytes, payloadHash) -> boolean
//
// Field objects are plain JS objects with camelCase keys matching the
// TypeScript `Core` interface, and bytes fields are Uint8Array.
// Timestamps are JS Number (Unix milliseconds fit in 53 bits well past
// year 2200).
//
// All functions return either a Uint8Array, a boolean, or fail closed.
// They never throw — callers may inspect the boolean result or rely on
// the canon-byte length to detect malformed input.

//go:build js && wasm

package main

import (
	"syscall/js"

	"galaxy/core/canon"
)

func main() {
	js.Global().Set("galaxyCore", js.ValueOf(map[string]any{
		"signRequest":       js.FuncOf(signRequest),
		"verifyResponse":    js.FuncOf(verifyResponse),
		"verifyEvent":       js.FuncOf(verifyEvent),
		"verifyPayloadHash": js.FuncOf(verifyPayloadHash),
	}))

	// Block forever so the Go runtime stays alive while JS keeps calling
	// the registered functions.
	select {}
}

func signRequest(_ js.Value, args []js.Value) any {
	if len(args) != 1 {
		return js.Null()
	}
	fields := canon.RequestSigningFields{
		ProtocolVersion: args[0].Get("protocolVersion").String(),
		DeviceSessionID: args[0].Get("deviceSessionId").String(),
		MessageType:     args[0].Get("messageType").String(),
		TimestampMS:     int64(args[0].Get("timestampMs").Float()),
		RequestID:       args[0].Get("requestId").String(),
		PayloadHash:     copyBytesFromJS(args[0].Get("payloadHash")),
	}
	return copyBytesToJS(canon.BuildRequestSigningInput(fields))
}

func verifyResponse(_ js.Value, args []js.Value) any {
	if len(args) != 3 {
		return js.ValueOf(false)
	}
	fields := canon.ResponseSigningFields{
		ProtocolVersion: args[2].Get("protocolVersion").String(),
		RequestID:       args[2].Get("requestId").String(),
		TimestampMS:     int64(args[2].Get("timestampMs").Float()),
		ResultCode:      args[2].Get("resultCode").String(),
		PayloadHash:     copyBytesFromJS(args[2].Get("payloadHash")),
	}
	publicKey := copyBytesFromJS(args[0])
	signature := copyBytesFromJS(args[1])
	if err := canon.VerifyResponseSignature(publicKey, signature, fields); err != nil {
		return js.ValueOf(false)
	}
	return js.ValueOf(true)
}

func verifyEvent(_ js.Value, args []js.Value) any {
	if len(args) != 3 {
		return js.ValueOf(false)
	}
	fields := canon.EventSigningFields{
		EventType:   args[2].Get("eventType").String(),
		EventID:     args[2].Get("eventId").String(),
		TimestampMS: int64(args[2].Get("timestampMs").Float()),
		RequestID:   args[2].Get("requestId").String(),
		TraceID:     args[2].Get("traceId").String(),
		PayloadHash: copyBytesFromJS(args[2].Get("payloadHash")),
	}
	publicKey := copyBytesFromJS(args[0])
	signature := copyBytesFromJS(args[1])
	if err := canon.VerifyEventSignature(publicKey, signature, fields); err != nil {
		return js.ValueOf(false)
	}
	return js.ValueOf(true)
}

func verifyPayloadHash(_ js.Value, args []js.Value) any {
	if len(args) != 2 {
		return js.ValueOf(false)
	}
	payloadBytes := copyBytesFromJS(args[0])
	payloadHash := copyBytesFromJS(args[1])
	if err := canon.VerifyPayloadHash(payloadBytes, payloadHash); err != nil {
		return js.ValueOf(false)
	}
	return js.ValueOf(true)
}

// copyBytesFromJS materialises a JS Uint8Array (or any indexable
// byte-shaped value) into a Go byte slice. We avoid `js.CopyBytesToGo`
// because TinyGo's implementation panics on values it does not
// recognise as Uint8Array — a check that misfires for Uint8Arrays
// constructed from Node's Buffer in Vitest's jsdom environment. The
// per-element copy is slower but always correct, and the canonical
// envelope payloads are small enough (≤ a few hundred bytes) that the
// difference is negligible.
func copyBytesFromJS(value js.Value) []byte {
	if value.IsUndefined() || value.IsNull() {
		return nil
	}
	length := value.Length()
	if length == 0 {
		return nil
	}
	dst := make([]byte, length)
	for i := 0; i < length; i++ {
		dst[i] = byte(value.Index(i).Int())
	}
	return dst
}

// copyBytesToJS allocates a JS Uint8Array of the same length as src and
// copies src into it. The result is safe to hand back across the
// JS/Go boundary as the canonical-bytes return value.
func copyBytesToJS(src []byte) js.Value {
	dst := js.Global().Get("Uint8Array").New(len(src))
	js.CopyBytesToJS(dst, src)
	return dst
}