util/route: create route package.

The route package is a thin wrapper around github.com/julienschmidt/httprouter.
It brings the interface back to http.Handler and embedds params in a context.
The new router comes with prefixing support.

util/route/route.go

@@ -0,0 +1,98 @@
+package route
+
+import (
+	"net/http"
+	"sync"
+
+	"github.com/julienschmidt/httprouter"
+	"golang.org/x/net/context"
+)
+
+var (
+	mtx   = sync.RWMutex{}
+	ctxts = map[*http.Request]context.Context{}
+)
+
+// Context returns the context for the request.
+func Context(r *http.Request) context.Context {
+	mtx.RLock()
+	defer mtx.RUnlock()
+	return ctxts[r]
+}
+
+type param string
+
+// Param returns param p for the context.
+func Param(ctx context.Context, p string) string {
+	return ctx.Value(param(p)).(string)
+}
+
+// handle turns a Handle into httprouter.Handle
+func handle(h http.HandlerFunc) httprouter.Handle {
+	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+
+		for _, p := range params {
+			ctx = context.WithValue(ctx, param(p.Key), p.Value)
+		}
+
+		mtx.Lock()
+		ctxts[r] = ctx
+		mtx.Unlock()
+
+		h(w, r)
+
+		mtx.Lock()
+		delete(ctxts, r)
+		mtx.Unlock()
+	}
+}
+
+// Router wraps httprouter.Router and adds support for prefixed sub-routers.
+type Router struct {
+	rtr    *httprouter.Router
+	prefix string
+}
+
+// New returns a new Router.
+func New() *Router {
+	return &Router{rtr: httprouter.New()}
+}
+
+// WithPrefix returns a router that prefixes all registered routes
+// with preifx.
+func (r *Router) WithPrefix(prefix string) *Router {
+	return &Router{rtr: r.rtr, prefix: r.prefix + prefix}
+}
+
+// Get registers a new GET route.
+func (r *Router) Get(path string, h http.HandlerFunc) {
+	r.rtr.GET(r.prefix+path, handle(h))
+}
+
+// Del registers a new DELETE route.
+func (r *Router) Del(path string, h http.HandlerFunc) {
+	r.rtr.DELETE(r.prefix+path, handle(h))
+}
+
+// Post registers a new POST route.
+func (r *Router) Post(path string, h http.HandlerFunc) {
+	r.rtr.POST(r.prefix+path, handle(h))
+}
+
+// ServeHTTP implements http.Handler.
+func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	r.rtr.ServeHTTP(w, req)
+}
+
+// FileServe returns a new http.HandlerFunc that serves files from dir.
+// Using routes must provide the *filepath parameter.
+func FileServe(dir string) http.HandlerFunc {
+	fs := http.FileServer(http.Dir(dir))
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		r.URL.Path = Param(Context(r), "filepath")
+		fs.ServeHTTP(w, r)
+	}
+}