Add support for proxying HTTP requests over AS websocket

appservice/appservice.go

@@ -166,6 +166,7 @@ func (as *AppService) PrepareWebsocket() {
 	defer as.websocketHandlersLock.Unlock()
 	if as.websocketHandlers == nil {
 		as.websocketHandlers = make(map[string]WebsocketHandler, 32)
+		as.websocketHandlers[WebsocketCommandHTTPProxy] = as.WebsocketHTTPProxy
 		as.websocketRequests = make(map[int]chan<- *WebsocketCommand)
 	}
 }

appservice/wshttp.go

@@ -0,0 +1,83 @@
+package appservice
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+)
+
+const WebsocketCommandHTTPProxy = "http_proxy"
+
+type HTTPProxyRequest struct {
+	Method  string          `json:"method"`
+	Path    string          `json:"path"`
+	Query   string          `json:"query"`
+	Headers http.Header     `json:"headers"`
+	Body    json.RawMessage `json:"body"`
+}
+
+type HTTPProxyResponse struct {
+	Status  int             `json:"status"`
+	Headers http.Header     `json:"headers"`
+	Body    json.RawMessage `json:"body"`
+
+	bodyBuf bytes.Buffer
+}
+
+func (p *HTTPProxyResponse) Header() http.Header {
+	return p.Headers
+}
+
+func (p *HTTPProxyResponse) Write(bytes []byte) (int, error) {
+	if p.Status == 0 {
+		p.Status = http.StatusOK
+	}
+	return p.bodyBuf.Write(bytes)
+}
+
+func (p *HTTPProxyResponse) WriteHeader(statusCode int) {
+	p.Status = statusCode
+}
+
+func (as *AppService) WebsocketHTTPProxy(cmd WebsocketCommand) (bool, interface{}) {
+	var req HTTPProxyRequest
+	if err := json.Unmarshal(cmd.Data, &req); err != nil {
+		return false, fmt.Errorf("failed to parse proxy request: %w", err)
+	}
+	if cmd.Ctx == nil {
+		cmd.Ctx = context.Background()
+	}
+	reqURL := (&url.URL{
+		Scheme:   "http",
+		Host:     "localhost",
+		Path:     req.Path,
+		RawQuery: req.Query,
+	}).String()
+	httpReq, err := http.NewRequestWithContext(cmd.Ctx, req.Method, reqURL, bytes.NewReader(req.Body))
+	if err != nil {
+		return false, fmt.Errorf("failed to create fake HTTP request: %w", err)
+	}
+	httpReq.Header = req.Headers
+
+	var resp HTTPProxyResponse
+	resp.Headers = make(http.Header)
+
+	as.Router.ServeHTTP(&resp, httpReq)
+
+	if resp.bodyBuf.Len() > 0 {
+		bodyData := resp.bodyBuf.Bytes()
+		if json.Valid(bodyData) {
+			resp.Body = bodyData
+		} else {
+			resp.Body = make([]byte, 2+base64.RawStdEncoding.EncodedLen(len(bodyData)))
+			resp.Body[0] = '"'
+			base64.RawStdEncoding.Encode(resp.Body[1:], bodyData)
+			resp.Body[len(resp.Body)-1] = '"'
+		}
+	}
+	return true, &resp
+}