Adds static fileserver middleware

static.go

@@ -0,0 +1,108 @@
+package narco
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+	"strings"
+
+	"github.com/codemodus/chain"
+	"golang.org/x/net/context"
+)
+
+type StaticFileServer struct {
+	dir    http.FileSystem
+	prefix string
+}
+
+type StaticFileServerError struct {
+	error  string
+	status int
+}
+
+func NewStaticFileServer(dir http.FileSystem, prefix string) *StaticFileServer {
+	return &StaticFileServer{
+		dir:    dir,
+		prefix: prefix,
+	}
+}
+
+func (e StaticFileServerError) Error() string {
+	return fmt.Sprintf("%d: %s", e.status, e.error)
+}
+
+func (fs *StaticFileServer) ServeHTTPError(rw http.ResponseWriter, req *http.Request) error {
+	if req.Method != "GET" && req.Method != "HEAD" {
+		return StaticFileServerError{"Invalid " + req.Method + " method", http.StatusMethodNotAllowed}
+	}
+
+	fpath := req.URL.Path
+	if len(fs.prefix) != 0 {
+		if strings.HasPrefix(fpath, fs.prefix) == false {
+			return StaticFileServerError{"Invalid path " + fpath, http.StatusNotFound}
+		}
+
+		fpath = strings.TrimPrefix(fpath, fs.prefix)
+	}
+
+	f, err := fs.dir.Open(fpath)
+	if err != nil {
+		if os.IsNotExist(err) == true {
+			return StaticFileServerError{"Unknown path " + fpath, http.StatusNotFound}
+		} else {
+			return StaticFileServerError{"Internal FS error", http.StatusInternalServerError}
+		}
+	}
+	defer f.Close()
+
+	fi, err := f.Stat()
+	if err != nil {
+		if os.IsNotExist(err) == true {
+			return StaticFileServerError{"Unknown path " + fpath, http.StatusNotFound}
+		} else {
+			return StaticFileServerError{"Internal FS error", http.StatusInternalServerError}
+		}
+	}
+
+	if fi.IsDir() == true {
+		if fpath[len(fpath)-1] == '/' {
+			return StaticFileServerError{"Cannot index directory", http.StatusUnauthorized}
+		} else {
+			http.Redirect(rw, req, req.URL.Path+"/", http.StatusFound)
+			return nil
+		}
+	}
+
+	http.ServeContent(rw, req, fpath, fi.ModTime(), f)
+	return nil
+}
+
+//http.Handler interface
+func (fs *StaticFileServer) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	err := fs.ServeHTTPError(rw, req)
+	if err != nil {
+		fsErr := err.(StaticFileServerError)
+		http.Error(rw, err.Error(), fsErr.status)
+	}
+}
+
+//chain handler interface
+func (fs *StaticFileServer) ServeHTTPContext(ctx context.Context, rw http.ResponseWriter, req *http.Request) {
+	fs.ServeHTTP(rw, req)
+}
+
+// chain wrapper. we just ignore the error, and send the request to
+// the next middleware. I would prefer to use as an endpoint, i.e. we
+// fail if its not good
+
+func (fs *StaticFileServer) Wrap() func(chain.Handler) chain.Handler {
+	return func(other chain.Handler) chain.Handler {
+		return chain.HandlerFunc(func(ctx context.Context, rw http.ResponseWriter, req *http.Request) {
+			fs.ServeHTTPError(rw, req)
+			// todo ? put the error in the context ?? otherwise we
+			// should simply use endpoint, which is good for static
+			// resources we serve here !
+			other.ServeHTTPContext(ctx, rw, req)
+		})
+	}
+}