Move server code to its own file

1 files changed, 265 insertions, 0 deletions

diff --git a/server.go b/server.go
new file mode 100644
index 0000000..cb3782a
--- /dev/null
+++ b/server.go
@@ -0,0 +1,265 @@
+package gemini
+
+import (
+	"bufio"
+	"crypto/tls"
+	"log"
+	"net"
+	"net/url"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Server is a Gemini server.
+type Server struct {
+	// Addr specifies the address that the server should listen on.
+	// If Addr is empty, the server will listen on the address ":1965".
+	Addr string
+
+	// Certificate provides a TLS certificate for use by the server.
+	// Using a self-signed certificate is recommended.
+	Certificate tls.Certificate
+
+	// Handler specifies the Handler for requests.
+	// If Handler is not set, the server will error.
+	Handler Handler
+}
+
+// ListenAndServe listens for requests at the server's configured address.
+func (s *Server) ListenAndServe() error {
+	addr := s.Addr
+
+	if addr == "" {
+		addr = ":1965"
+	}
+
+	ln, err := net.Listen("tcp", addr)
+	if err != nil {
+		return err
+	}
+	defer ln.Close()
+
+	config := &tls.Config{
+		InsecureSkipVerify: true,
+		Certificates:       []tls.Certificate{s.Certificate},
+		ClientAuth:         tls.RequestClientCert,
+	}
+	tlsListener := tls.NewListener(ln, config)
+	return s.Serve(tlsListener)
+}
+
+// Serve listens for requests on the provided listener.
+func (s *Server) Serve(l net.Listener) error {
+	var tempDelay time.Duration // how long to sleep on accept failure
+
+	for {
+		rw, err := l.Accept()
+		if err != nil {
+			// If this is a temporary error, sleep
+			if ne, ok := err.(net.Error); ok && ne.Temporary() {
+				if tempDelay == 0 {
+					tempDelay = 5 * time.Millisecond
+				} else {
+					tempDelay *= 2
+				}
+				if max := 1 * time.Second; tempDelay > max {
+					tempDelay = max
+				}
+				log.Printf("gemini: Accept error: %v; retrying in %v", err, tempDelay)
+				time.Sleep(tempDelay)
+				continue
+			}
+
+			// Otherwise, return the error
+			return err
+		}
+
+		tempDelay = 0
+		go s.respond(rw)
+	}
+}
+
+// ResponseWriter is used by a Gemini handler to construct a Gemini response.
+type ResponseWriter struct {
+	w           *bufio.Writer
+	bodyAllowed bool
+}
+
+func newResponseWriter(conn net.Conn) *ResponseWriter {
+	return &ResponseWriter{
+		w: bufio.NewWriter(conn),
+	}
+}
+
+// WriteHeader writes the response header.
+//
+// Meta contains more information related to the response status.
+// For successful responses, Meta should contain the mimetype of the response.
+// For failure responses, Meta should contain a short description of the failure.
+// Meta should not be longer than 1024 bytes.
+func (r *ResponseWriter) WriteHeader(status int, meta string) {
+	r.w.WriteString(strconv.Itoa(status))
+	r.w.WriteByte(' ')
+	r.w.WriteString(meta)
+	r.w.Write(crlf)
+
+	// Only allow body to be written on successful status codes.
+	if status/10 == StatusClassSuccess {
+		r.bodyAllowed = true
+	}
+}
+
+// Write writes the response body.
+// If the response status does not allow for a response body, Write returns
+// ErrBodyNotAllowed.
+// WriteHeader must be called before Write.
+func (r *ResponseWriter) Write(b []byte) (int, error) {
+	if !r.bodyAllowed {
+		return 0, ErrBodyNotAllowed
+	}
+	return r.w.Write(b)
+}
+
+// respond responds to a connection.
+func (s *Server) respond(conn net.Conn) {
+	r := bufio.NewReader(conn)
+	rw := newResponseWriter(conn)
+	// Read requested URL
+	rawurl, err := r.ReadString('\r')
+	if err != nil {
+		return
+	}
+	// Read terminating line feed
+	if b, err := r.ReadByte(); err != nil {
+		return
+	} else if b != '\n' {
+		rw.WriteHeader(StatusBadRequest, "Bad request")
+	}
+	// Trim carriage return
+	rawurl = rawurl[:len(rawurl)-1]
+	// Ensure URL is valid
+	if len(rawurl) > 1024 {
+		rw.WriteHeader(StatusBadRequest, "Requested URL exceeds 1024 bytes")
+	} else if url, err := url.Parse(rawurl); err != nil || url.User != nil {
+		// Note that we return an error status if User is specified in the URL
+		rw.WriteHeader(StatusBadRequest, "Requested URL is invalid")
+	} else {
+		// Gather information about the request
+		req := &Request{
+			URL:        url,
+			RemoteAddr: conn.RemoteAddr(),
+			TLS:        conn.(*tls.Conn).ConnectionState(),
+		}
+		s.Handler.Serve(rw, req)
+	}
+	rw.w.Flush()
+	conn.Close()
+}
+
+// A Handler responds to a Gemini request.
+type Handler interface {
+	// Serve accepts a Request and constructs a Response.
+	Serve(*ResponseWriter, *Request)
+}
+
+// ServeMux is a Gemini request multiplexer.
+// It matches the URL of each incoming request against a list of registered
+// patterns and calls the handler for the pattern that most closesly matches
+// the URL.
+type ServeMux struct {
+	entries []muxEntry
+}
+
+type muxEntry struct {
+	u       *url.URL
+	handler Handler
+}
+
+func (m *ServeMux) match(url *url.URL) Handler {
+	for _, e := range m.entries {
+		if (e.u.Scheme == "" || url.Scheme == e.u.Scheme) &&
+			(e.u.Host == "" || url.Host == e.u.Host) &&
+			strings.HasPrefix(url.Path, e.u.Path) {
+			return e.handler
+		}
+	}
+	return nil
+}
+
+// Handle registers a Handler for the given pattern.
+func (m *ServeMux) Handle(pattern string, handler Handler) {
+	url, err := url.Parse(pattern)
+	if err != nil {
+		panic(err)
+	}
+	e := muxEntry{
+		url,
+		handler,
+	}
+	m.entries = appendSorted(m.entries, e)
+}
+
+// HandleFunc registers a HandlerFunc for the given pattern.
+func (m *ServeMux) HandleFunc(pattern string, handlerFunc func(*ResponseWriter, *Request)) {
+	handler := HandlerFunc(handlerFunc)
+	m.Handle(pattern, handler)
+}
+
+// Serve responds to the request with the appropriate handler.
+func (m *ServeMux) Serve(rw *ResponseWriter, req *Request) {
+	h := m.match(req.URL)
+	if h == nil {
+		rw.WriteHeader(StatusNotFound, "Not found")
+		return
+	}
+	h.Serve(rw, req)
+}
+
+// appendSorted appends the entry e in the proper place in entries.
+func appendSorted(es []muxEntry, e muxEntry) []muxEntry {
+	n := len(es)
+	// sort by length
+	i := sort.Search(n, func(i int) bool {
+		// Sort entries by length.
+		// - Entries with a scheme take preference over entries without.
+		// - Entries with a host take preference over entries without.
+		// - Longer paths take preference over shorter paths.
+		//
+		// Long version:
+		// if es[i].scheme != "" {
+		// 	if e.scheme == "" {
+		// 		return false
+		// 	}
+		// 	return len(es[i].scheme) < len(e.scheme)
+		// }
+		// if es[i].host != "" {
+		// 	if e.host == "" {
+		// 		return false
+		// 	}
+		// 	return len(es[i].host) < len(e.host)
+		// }
+		// return len(es[i].path) < len(e.path)
+
+		// Condensed version:
+		return (es[i].u.Scheme == "" || (e.u.Scheme != "" && len(es[i].u.Scheme) < len(e.u.Scheme))) &&
+			(es[i].u.Host == "" || (e.u.Host != "" && len(es[i].u.Host) < len(e.u.Host))) &&
+			len(es[i].u.Path) < len(e.u.Path)
+	})
+	if i == n {
+		return append(es, e)
+	}
+	// we now know that i points at where we want to insert
+	es = append(es, muxEntry{}) // try to grow the slice in place, any entry works.
+	copy(es[i+1:], es[i:])      // Move shorter entries down
+	es[i] = e
+	return es
+}
+
+// A wrapper around a bare function that implements Handler.
+type HandlerFunc func(*ResponseWriter, *Request)
+
+func (f HandlerFunc) Serve(rw *ResponseWriter, req *Request) {
+	f(rw, req)
+}