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package gemini
import (
"bytes"
"context"
"net/url"
"strings"
"time"
)
// 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 may also call ResponseWriter.Close to
// manually close the connection.
//
// The provided context is canceled when the client's connection is closed,
// when ResponseWriter.Close is called, or when the ServeGemini method returns.
//
// Handlers should not modify the provided Request.
type Handler interface {
ServeGemini(context.Context, *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(context.Context, *ResponseWriter, *Request)
// ServeGemini calls f(ctx, w, r).
func (f HandlerFunc) ServeGemini(ctx context.Context, w *ResponseWriter, r *Request) {
f(ctx, w, r)
}
// StatusHandler returns a request handler that responds to each request
// with the provided status code and meta.
func StatusHandler(status Status, meta string) Handler {
return HandlerFunc(func(ctx context.Context, w *ResponseWriter, r *Request) {
w.WriteHeader(status, meta)
})
}
// NotFoundHandler returns a simple request handler that replies to each
// request with a “51 Not found” reply.
func NotFoundHandler() Handler {
return StatusHandler(StatusNotFound, "Not found")
}
// 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(ctx context.Context, 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(ctx, w, r2)
} else {
w.WriteHeader(StatusNotFound, "Not found")
}
})
}
// TimeoutHandler returns a Handler that runs h with the given time limit.
//
// The new Handler calls h.ServeGemini to handle each request, but
// if a call runs for longer than its time limit, the handler responds with a
// 40 Temporary Failure error.
func TimeoutHandler(h Handler, dt time.Duration) Handler {
return &timeoutHandler{
h: h,
dt: dt,
}
}
type timeoutHandler struct {
h Handler
dt time.Duration
}
func (t *timeoutHandler) ServeGemini(ctx context.Context, w *ResponseWriter, r *Request) {
ctx, cancel := context.WithTimeout(ctx, t.dt)
defer cancel()
conn := w.Hijack()
var b bytes.Buffer
w.reset(nopCloser{&b})
done := make(chan struct{})
go func() {
t.h.ServeGemini(ctx, w, r)
close(done)
}()
select {
case <-done:
conn.Write(b.Bytes())
case <-ctx.Done():
w.reset(conn)
w.WriteHeader(StatusTemporaryFailure, "Timeout")
}
}
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