package httputil

import (
	"net/http"
)

// Instrumenter wraps a handler with per-route instrumentation. The route is
// the ServeMux pattern the handler is registered under; it is passed
// explicitly because the pattern ServeMux records on a request is not
// visible to middleware wrapping the mux from the outside.
type Instrumenter func(route string, h http.Handler) http.Handler

// Router is a thin layer over http.ServeMux that applies an Instrumenter to
// every route and knows how to answer unrouted requests the Matrix way.
//
// Patterns use Go 1.22 syntax, method included:
//
//	r.HandleFunc("GET /_matrix/client/versions", versions)
type Router struct {
	mux        *http.ServeMux
	instrument Instrumenter
}

// NewRouter returns a router. A nil Instrumenter means no instrumentation.
func NewRouter(instrument Instrumenter) *Router {
	if instrument == nil {
		instrument = func(_ string, h http.Handler) http.Handler { return h }
	}
	mux := http.NewServeMux()
	r := &Router{mux: mux, instrument: instrument}
	// Anything that matches no other pattern is M_UNRECOGNIZED, per the
	// Client-Server API's "Unsupported endpoints" rule.
	r.Handle("/", NotFoundHandler())
	return r
}

// Handle registers a handler for a pattern.
func (r *Router) Handle(pattern string, h http.Handler) {
	r.mux.Handle(pattern, r.instrument(pattern, h))
}

// HandleFunc registers an error-returning handler for a pattern.
func (r *Router) HandleFunc(pattern string, h Handler) {
	r.Handle(pattern, Wrap(h))
}

// ServeHTTP implements http.Handler.
func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	r.mux.ServeHTTP(w, req)
}