1st

go.mod

@@ -0,0 +1,3 @@
+module github.com/zeevdiukman/go-reverseproxy
+
+go 1.24.0

reverseproxy.go

@@ -0,0 +1,70 @@
+package reverseproxy
+
+import (
+	"context"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"strings"
+)
+
+type ReverseProxy struct {
+	*httputil.ReverseProxy
+}
+
+type CtxKey string
+
+func New(ctx context.Context, host string) *ReverseProxy {
+	ctxKey := CtxKey("host")
+	ctx = context.WithValue(ctx, ctxKey, host)
+	reverseproxy := &httputil.ReverseProxy{
+		Director: func(r *http.Request) {
+			r = r.WithContext(ctx)
+			hostFromCtx := ctx.Value(ctxKey).(string)
+			target, _ := url.Parse(hostFromCtx)
+			targetQuery := target.RawQuery
+			r.URL.Scheme = target.Scheme
+			r.URL.Host = target.Host
+			r.URL.Path, r.URL.RawPath = joinURLPath(target, r.URL)
+			if targetQuery == "" || r.URL.RawQuery == "" {
+				r.URL.RawQuery = targetQuery + r.URL.RawQuery
+			} else {
+				r.URL.RawQuery = targetQuery + "&" + r.URL.RawQuery
+			}
+		},
+	}
+	return &ReverseProxy{reverseproxy}
+}
+
+func singleJoiningSlash(a, b string) string {
+	aslash := strings.HasSuffix(a, "/")
+	bslash := strings.HasPrefix(b, "/")
+	switch {
+	case aslash && bslash:
+		return a + b[1:]
+	case !aslash && !bslash:
+		return a + "/" + b
+	}
+	return a + b
+}
+
+func joinURLPath(a, b *url.URL) (path, rawpath string) {
+	if a.RawPath == "" && b.RawPath == "" {
+		return singleJoiningSlash(a.Path, b.Path), ""
+	}
+	// Same as singleJoiningSlash, but uses EscapedPath to determine
+	// whether a slash should be added
+	apath := a.EscapedPath()
+	bpath := b.EscapedPath()
+
+	aslash := strings.HasSuffix(apath, "/")
+	bslash := strings.HasPrefix(bpath, "/")
+
+	switch {
+	case aslash && bslash:
+		return a.Path + b.Path[1:], apath + bpath[1:]
+	case !aslash && !bslash:
+		return a.Path + "/" + b.Path, apath + "/" + bpath
+	}
+	return a.Path + b.Path, apath + bpath
+}