Add utility Handler functions

1 files changed, 91 insertions, 0 deletions

diff --git a/handler.go b/handler.go
new file mode 100644
index 0000000..e0edd90
--- /dev/null
+++ b/handler.go
@@ -0,0 +1,91 @@
+package gemini
+
+import (
+	"net/url"
+	"strings"
+)
+
+// A Handler responds to a Gemini request.
+//
+// ServeGemini should write the response header and data to the ResponseWriter
+// and then return. Returning signals that the request is finished; it is not
+// valid to use the ResponseWriter after or concurrently with the completion
+// of the ServeGemini call.
+//
+// Handlers should not modify the provided Request.
+//
+// If ServeGemini panics, the server (the caller of ServeGemini) assumes that
+// the effect of the panic was isolated to the active request. It recovers
+// the panic, logs a stack trace to the server error log, and closes the
+// network connection. To abort a handler so the client sees an interrupted
+// response but the server doesn't log an error, panic with the value
+// ErrAbortHandler.
+type Handler interface {
+	ServeGemini(ResponseWriter, *Request)
+}
+
+// The HandlerFunc type is an adapter to allow the use of ordinary functions
+// as Gemini handlers. If f is a function with the appropriate signature,
+// HandlerFunc(f) is a Handler that calls f.
+type HandlerFunc func(ResponseWriter, *Request)
+
+// ServeGemini calls f(w, r).
+func (f HandlerFunc) ServeGemini(w ResponseWriter, r *Request) {
+	f(w, r)
+}
+
+// RedirectHandler returns a request handler that redirects each request it
+// receives to the given url using the given status code.
+//
+// The provided code should be in the 3x range and is usually
+// StatusRedirect or StatusPermanentRedirect.
+func RedirectHandler(url string, code int) Handler {
+	return &redirectHandler{url, code}
+}
+
+type redirectHandler struct {
+	url  string
+	code int
+}
+
+func (h *redirectHandler) ServeGemini(w ResponseWriter, r *Request) {
+	w.WriteHeader(h.code, h.url)
+}
+
+// NotFound replies to the request with a Gemini 51 not found error.
+func NotFound(w ResponseWriter, r *Request) {
+	w.WriteHeader(StatusNotFound, "Not found")
+}
+
+// NotFoundHandler returns a simple request handler that replies to each
+// request with a “51 Not found” reply.
+func NotFoundHandler() Handler {
+	return HandlerFunc(NotFound)
+}
+
+// StripPrefix returns a handler that serves Gemini requests by removing the
+// given prefix from the request URL's Path (and RawPath if set) and invoking
+// the handler h. StripPrefix handles a request for a path that doesn't begin
+// with prefix by replying with a Gemini 51 not found error. The prefix must
+// match exactly: if the prefix in the request contains escaped characters the
+// reply is also a Gemini 51 not found error.
+func StripPrefix(prefix string, h Handler) Handler {
+	if prefix == "" {
+		return h
+	}
+	return HandlerFunc(func(w ResponseWriter, r *Request) {
+		p := strings.TrimPrefix(r.URL.Path, prefix)
+		rp := strings.TrimPrefix(r.URL.RawPath, prefix)
+		if len(p) < len(r.URL.Path) && (r.URL.RawPath == "" || len(rp) < len(r.URL.RawPath)) {
+			r2 := new(Request)
+			*r2 = *r
+			r2.URL = new(url.URL)
+			*r2.URL = *r.URL
+			r2.URL.Path = p
+			r2.URL.RawPath = rp
+			h.ServeGemini(w, r2)
+		} else {
+			NotFound(w, r)
+		}
+	})
+}