102 lines
3.2 KiB
Go
102 lines
3.2 KiB
Go
// Copyright 2020 The Matrix.org Foundation C.I.C.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//go:build wasm
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// +build wasm
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package main
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import (
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"bufio"
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"fmt"
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"net/http"
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"net/http/httptest"
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"strings"
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"syscall/js"
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)
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// JSServer exposes an HTTP-like server interface which allows JS to 'send' requests to it.
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type JSServer struct {
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// The router which will service requests
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Mux http.Handler
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}
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// OnRequestFromJS is the function that JS will invoke when there is a new request.
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// The JS function signature is:
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// function(reqString: string): Promise<{result: string, error: string}>
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// Usage is like:
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// const res = await global._go_js_server.fetch(reqString);
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// if (res.error) {
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// // handle error: this is a 'network' error, not a non-2xx error.
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// }
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// const rawHttpResponse = res.result;
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func (h *JSServer) OnRequestFromJS(this js.Value, args []js.Value) interface{} {
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// we HAVE to spawn a new goroutine and return immediately or else Go will deadlock
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// if this request blocks at all e.g for /sync calls
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httpStr := args[0].String()
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promise := js.Global().Get("Promise").New(js.FuncOf(func(pthis js.Value, pargs []js.Value) interface{} {
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// The initial callback code for new Promise() is also called on the critical path, which is why
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// we need to put this in an immediately invoked goroutine.
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go func() {
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resolve := pargs[0]
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resStr, err := h.handle(httpStr)
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errStr := ""
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if err != nil {
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errStr = err.Error()
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}
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resolve.Invoke(map[string]interface{}{
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"result": resStr,
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"error": errStr,
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})
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}()
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return nil
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}))
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return promise
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}
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// handle invokes the http.ServeMux for this request and returns the raw HTTP response.
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func (h *JSServer) handle(httpStr string) (resStr string, err error) {
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req, err := http.ReadRequest(bufio.NewReader(strings.NewReader(httpStr)))
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if err != nil {
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return
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}
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w := httptest.NewRecorder()
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h.Mux.ServeHTTP(w, req)
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res := w.Result()
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var resBuffer strings.Builder
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err = res.Write(&resBuffer)
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return resBuffer.String(), err
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}
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// ListenAndServe registers a variable in JS-land with the given namespace. This variable is
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// a function which JS-land can call to 'send' HTTP requests. The function is attached to
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// a global object called "_go_js_server". See OnRequestFromJS for more info.
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func (h *JSServer) ListenAndServe(namespace string) {
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globalName := "_go_js_server"
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// register a hook in JS-land for it to invoke stuff
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server := js.Global().Get(globalName)
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if !server.Truthy() {
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server = js.Global().Get("Object").New()
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js.Global().Set(globalName, server)
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}
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server.Set(namespace, js.FuncOf(h.OnRequestFromJS))
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fmt.Printf("Listening for requests from JS on function %s.%s\n", globalName, namespace)
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// Block forever to mimic http.ListenAndServe
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select {}
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}
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