Implement --host flag to override {{.Host}}

Fixes #15

router.go

@@ -4,23 +4,30 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"net/url"
 	"runtime/debug"
 	"strconv"
 	"time"
 
 	"gitea.hashru.nl/dsprenkels/rushlink/internal/db"
 	"github.com/gorilla/mux"
+	"github.com/pkg/errors"
 )
 
 const urlKeyExpr = "{key:[A-Za-z0-9-_]{4,}}"
 const urlKeyWithExtExpr = urlKeyExpr + "{ext:\\.[A-Za-z0-9-_]+}"
 
 type rushlink struct {
-	db *db.Database
-	fs *db.FileStore
+	db   *db.Database
+	fs   *db.FileStore
+	host *url.URL
 }
 
-func recoveryMiddleware(next http.Handler) http.Handler {
+func (rl *rushlink) Host() *url.URL {
+	return rl.host
+}
+
+func (rl *rushlink) recoveryMiddleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		defer func() {
 			defer func() {
@@ -34,13 +41,22 @@ func recoveryMiddleware(next http.Handler) http.Handler {
 			if err := recover(); err != nil {
 				log.Printf("error: %v\n", err)
 				debug.PrintStack()
-				renderInternalServerError(w, r, err)
+				rl.renderInternalServerError(w, r, err)
 			}
 		}()
 		next.ServeHTTP(w, r)
 	})
 }
 
+func (rl *rushlink) metricsMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		srw := statusResponseWriter{Inner: w}
+		next.ServeHTTP(&srw, r)
+		status := strconv.Itoa(srw.StatusCode)
+		metricRequestsTotalCounter.WithLabelValues(status, r.Method).Inc()
+	})
+}
+
 type statusResponseWriter struct {
 	Inner      http.ResponseWriter
 	StatusCode int
@@ -62,26 +78,26 @@ func (w *statusResponseWriter) WriteHeader(statusCode int) {
 	w.Inner.WriteHeader(statusCode)
 }
 
-func metricsMiddleware(next http.Handler) http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		srw := statusResponseWriter{Inner: w}
-		next.ServeHTTP(&srw, r)
-		status := strconv.Itoa(srw.StatusCode)
-		metricRequestsTotalCounter.WithLabelValues(status, r.Method).Inc()
-	})
-}
-
 // StartMainServer starts the main http server listening on addr.
-func StartMainServer(addr string, db *db.Database, fs *db.FileStore) {
+func StartMainServer(addr string, db *db.Database, fs *db.FileStore, rawhost *string) {
+	var host *url.URL
+	if rawhost != nil {
+		var err error
+		host, err = url.Parse(*rawhost)
+		if err != nil {
+			log.Fatalln(errors.Wrap(err, "could not parse host flag"))
+		}
+	}
 	rl := rushlink{
-		db: db,
-		fs: fs,
+		db:   db,
+		fs:   fs,
+		host: host,
 	}
 
 	// Initialize Gorilla router
 	router := mux.NewRouter()
-	router.Use(recoveryMiddleware)
-	router.Use(metricsMiddleware)
+	router.Use(rl.recoveryMiddleware)
+	router.Use(rl.metricsMiddleware)
 	router.HandleFunc("/uploads/{id:[A-Za-z0-9-_]+}/{filename:.+}", rl.uploadFileGetHandler).Methods("GET", "HEAD")
 	router.HandleFunc("/", rl.indexGetHandler).Methods("GET", "HEAD")
 	router.HandleFunc("/", rl.newPasteHandler).Methods("POST")