Pull request: 2479 simpl

Updates #2479.

Squashed commit of the following:

commit 0fdb0d0
Author: Ainar Garipov <[email protected]>
Date:   Mon Mar 29 19:22:56 2021 +0300

    dnsfilter: add a comment

commit d5d6538
Merge: 6a09acc e710ce1
Author: Ainar Garipov <[email protected]>
Date:   Mon Mar 29 19:19:39 2021 +0300

    Merge branch 'master' into 2479-simpl

commit 6a09acc
Author: jvoisin <[email protected]>
Date:   Tue Dec 22 16:43:47 2020 +0100

    Generalise a construct to simplify a function

Author: ainar-g

internal/dnsfilter/rewrites.go

@@ -122,21 +122,27 @@ func findRewrites(a []RewriteEntry, host string) []RewriteEntry {
 
 	sort.Sort(rr)
 
-	isWC := isWildcard(rr[0].Domain)
-	if !isWC {
-		for i, r := range rr {
-			if isWildcard(r.Domain) {
-				rr = rr[:i]
-				break
-			}
+	for i, r := range rr {
+		if isWildcard(r.Domain) {
+			// Don't use rr[:0], because we need to return at least
+			// one item here.
+			rr = rr[:max(1, i)]
+
+			break
 		}
-	} else {
-		rr = rr[:1]
 	}
 
 	return rr
 }
 
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+
+	return b
+}
+
 func rewriteArrayDup(a []RewriteEntry) []RewriteEntry {
 	a2 := make([]RewriteEntry, len(a))
 	copy(a2, a)