From f6a26896c967a2f6e782f1e4a216204cebaa1507 Mon Sep 17 00:00:00 2001
From: Anmol Sethi <hi@nhooyr.io>
Date: Fri, 20 Sep 2019 22:18:29 -0500
Subject: [PATCH] Implement low level typed interface to the browser WebSocket
API
Updates #121
---
internal/websocketjs/websocketjs.go | 149 +++++++++++++++++++++++
internal/websocketjs/websocketjs_test.go | 26 ++++
2 files changed, 175 insertions(+)
create mode 100644 internal/websocketjs/websocketjs.go
create mode 100644 internal/websocketjs/websocketjs_test.go
diff --git a/internal/websocketjs/websocketjs.go b/internal/websocketjs/websocketjs.go
new file mode 100644
index 0000000..0265956
--- /dev/null
+++ b/internal/websocketjs/websocketjs.go
@@ -0,0 +1,149 @@
+// +build js
+
+// websocketjs implements typed access to the browser javascript WebSocket API.
+// https://developer.mozilla.org/en-US/docs/Web/API/WebSocket
+package websocketjs
+
+import (
+ "context"
+ "syscall/js"
+)
+
+func handleJSError(err *error, onErr func()) {
+ r := recover()
+
+ if jsErr, ok := r.(js.Error); ok {
+ *err = jsErr
+
+ if onErr != nil {
+ onErr()
+ }
+ return
+ }
+
+ if r != nil {
+ panic(r)
+ }
+}
+
+func New(ctx context.Context, url string, protocols []string) (c *WebSocket, err error) {
+ defer handleJSError(&err, func() {
+ c = nil
+ })
+
+ jsProtocols := make([]interface{}, len(protocols))
+ for i, p := range protocols {
+ jsProtocols[i] = p
+ }
+
+ c = &WebSocket{
+ v: js.Global().Get("WebSocket").New(url, jsProtocols),
+ }
+
+ c.setBinaryType("arrayBuffer")
+
+ c.Extensions = c.v.Get("extensions").String()
+ c.Protocol = c.v.Get("protocol").String()
+ c.URL = c.v.Get("url").String()
+
+ return c, nil
+}
+
+type WebSocket struct {
+ Extensions string
+ Protocol string
+ URL string
+
+ v js.Value
+}
+
+func (c *WebSocket) setBinaryType(typ string) {
+ c.v.Set("binaryType", string(typ))
+}
+
+func (c *WebSocket) BufferedAmount() uint32 {
+ return uint32(c.v.Get("bufferedAmount").Int())
+}
+
+func (c *WebSocket) addEventListener(eventType string, fn func(e js.Value)) {
+ c.v.Call("addEventListener", eventType, js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+ fn(args[0])
+ return nil
+ }))
+}
+
+type CloseEvent struct {
+ Code uint16
+ Reason string
+ WasClean bool
+}
+
+func (c *WebSocket) OnClose(fn func(CloseEvent)) {
+ c.addEventListener("close", func(e js.Value) {
+ ce := CloseEvent{
+ Code: uint16(e.Get("code").Int()),
+ Reason: e.Get("reason").String(),
+ WasClean: e.Get("wasClean").Bool(),
+ }
+ fn(ce)
+ })
+}
+
+func (c *WebSocket) OnError(fn func(e js.Value)) {
+ c.addEventListener("error", fn)
+}
+
+type MessageEvent struct {
+ Data []byte
+ // There are more types to the interface but we don't use them.
+ // See https://developer.mozilla.org/en-US/docs/Web/API/MessageEvent
+}
+
+func (c *WebSocket) OnMessage(fn func(m MessageEvent)) {
+ c.addEventListener("message", func(e js.Value) {
+ arrayBuffer := e.Get("data")
+ data := extractArrayBuffer(arrayBuffer)
+
+ me := MessageEvent{
+ Data: data,
+ }
+ fn(me)
+
+ return
+ })
+}
+
+func (c *WebSocket) OnOpen(fn func(e js.Value)) {
+ c.addEventListener("open", fn)
+}
+
+func (c *WebSocket) Close(code int, reason string) (err error) {
+ defer handleJSError(&err, nil)
+ c.v.Call("close", code, reason)
+ return err
+}
+
+func (c *WebSocket) SendText(v string) (err error) {
+ defer handleJSError(&err, nil)
+ c.v.Call("send", v)
+ return err
+}
+
+func (c *WebSocket) SendBytes(v []byte) (err error) {
+ defer handleJSError(&err, nil)
+ c.v.Call("send", uint8Array(v))
+ return err
+}
+
+func extractArrayBuffer(arrayBuffer js.Value) []byte {
+ uint8Array := js.Global().Get("Uint8Array").New(arrayBuffer)
+ dst := make([]byte, uint8Array.Length())
+ js.CopyBytesToGo(dst, uint8Array)
+ return dst
+}
+
+func uint8Array(src []byte) js.Value {
+ uint8Array := js.Global().Get("Uint8Array").New(len(src))
+ js.CopyBytesToJS(uint8Array, src)
+ return uint8Array
+}
diff --git a/internal/websocketjs/websocketjs_test.go b/internal/websocketjs/websocketjs_test.go
new file mode 100644
index 0000000..46819bd
--- /dev/null
+++ b/internal/websocketjs/websocketjs_test.go
@@ -0,0 +1,26 @@
+// +build js
+
+package websocketjs
+
+import (
+ "context"
+ "syscall/js"
+ "testing"
+ "time"
+)
+
+func TestWebSocket(t *testing.T) {
+ t.Parallel()
+
+ c, err := New(context.Background(), "ws://localhost:8081", nil)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ c.OnError(func(e js.Value) {
+ t.Log(js.Global().Get("JSON").Call("stringify", e))
+ t.Log(c.v.Get("readyState"))
+ })
+
+ time.Sleep(time.Second)
+}
--
GitLab