Answer 500, not 404, when the IP lookup cannot read the database (closes #109)

A failed database read for an address was listed in the answer's errors
as if the address had no route, so the lookup answered 404, or 200 next
to a routed address. Only a missing route or an invalid address is
listed now; any other read error is logged and answers 500 with the JSON
error body, as the AS and prefix JSON routes do.

Model: opus-5-5

internal/server/handlers.go

@@ -675,10 +675,7 @@ func (s *Server) handleIPInfo() http.HandlerFunc {
 		}
 
 		ctx := r.Context()
-		response := IPLookupResponse{
-			Query:   target,
-			Results: make([]*database.IPInfo, 0),
-		}
+		response := IPLookupResponse{Query: target, Results: make([]*database.IPInfo, 0)}
 
 		// Collect all IPs to look up
 		ipsToLookup, resolveErrors := s.resolveLookupTargets(ctx, target)
@@ -708,11 +705,16 @@ func (s *Server) handleIPInfo() http.HandlerFunc {
 				return
 			}
 
-			if err != nil {
-				response.Errors = append(response.Errors,
-					ip+": "+s.lookupErrorMessage(ip, err))
+			switch {
+			case errors.Is(err, database.ErrNoRoute), errors.Is(err, database.ErrInvalidIP):
+				response.Errors = append(response.Errors, ip+": "+err.Error())
 
 				continue
+			case err != nil:
+				s.logger.Error("Failed to look up IP", "ip", ip, "error", err)
+				s.writeJSONError(w, http.StatusInternalServerError, internalErrorMessage)
+
+				return
 			}
 
 			// Do PTR lookup for this IP
@@ -751,19 +753,6 @@ func (s *Server) handleIPInfo() http.HandlerFunc {
 	}
 }
 
-// lookupErrorMessage returns what an IP lookup answer says about err, the
-// failed lookup of ip: err's own text when ip is not a valid address or has no
-// route, otherwise a fixed message, with err in the log.
-func (s *Server) lookupErrorMessage(ip string, err error) string {
-	if errors.Is(err, database.ErrNoRoute) || errors.Is(err, database.ErrInvalidIP) {
-		return err.Error()
-	}
-
-	s.logger.Error("Failed to look up IP", "ip", ip, "error", err)
-
-	return internalErrorMessage
-}
-
 // lookupTarget returns what an IP lookup request asks for: the ip or addr URL
 // parameter, or else the client's own address.
 func lookupTarget(r *http.Request) string {