From 22d5185575ebf2d43dbc83aa449f26f1645e146f Mon Sep 17 00:00:00 2001
From: Emil Guliyev <emil@laserlike.com>
Date: Tue, 14 Aug 2018 01:51:29 -0700
Subject: [PATCH] Optimize Decompose

---
 publicsuffix/publicsuffix.go | 79 +++++++++++++++++++++---------------
 1 file changed, 46 insertions(+), 33 deletions(-)

diff --git a/publicsuffix/publicsuffix.go b/publicsuffix/publicsuffix.go
index bcc47ebf..e4192950 100644
--- a/publicsuffix/publicsuffix.go
+++ b/publicsuffix/publicsuffix.go
@@ -11,7 +11,6 @@ import (
 	"io"
 	"net/http/cookiejar"
 	"os"
-	"regexp"
 	"strings"
 
 	"golang.org/x/net/idna"
@@ -208,12 +207,12 @@ func (l *List) Find(name string, options *FindOptions) *Rule {
 		}
 		i := strings.IndexRune(name, '.')
 		if i < 0 {
-			break
+			return options.DefaultRule
 		}
 		name = name[i+1:]
 	}
 
-	return options.DefaultRule
+	return nil
 }
 
 // NewRule parses the rule content, creates and returns a Rule.
@@ -291,36 +290,51 @@ func (r *Rule) Match(name string) bool {
 
 // Decompose takes a name as input and decomposes it into a tuple of <TRD+SLD, TLD>,
 // according to the rule definition and type.
-func (r *Rule) Decompose(name string) [2]string {
-	var parts []string
-
+func (r *Rule) Decompose(name string) (result [2]string) {
+	result = [2]string{"", ""}
 	switch r.Type {
+	case NormalType:
+		name = strings.TrimSuffix(name, r.Value)
+		if len(name) == 0 {
+			return
+		}
+		result[0] = name[:len(name)-1]
+		result[1] = r.Value
 	case WildcardType:
-		parts = append([]string{`.*?`}, r.parts()...)
-	default:
-		parts = r.parts()
-	}
-
-	suffix := strings.Join(parts, `\.`)
-	re := regexp.MustCompile(fmt.Sprintf(`^(.+)\.(%s)$`, suffix))
-
-	matches := re.FindStringSubmatch(name)
-	if len(matches) < 3 {
-		return [2]string{"", ""}
-	}
-
-	return [2]string{matches[1], matches[2]}
-}
-
-func (r *Rule) parts() []string {
-	labels := Labels(r.Value)
-	if r.Type == ExceptionType {
-		return labels[1:]
-	}
-	if r.Type == WildcardType && r.Value == "" {
-		return []string{}
+		if r == DefaultRule {
+			i := strings.LastIndexByte(name, byte('.'))
+			if i < 0 {
+				return
+			}
+			result[0] = name[:i]
+			result[1] = name[i+1:]
+			return
+		}
+		name := strings.TrimSuffix(name, r.Value)
+		if len(name) == 0 {
+			return
+		}
+		name = name[:len(name)-1]
+		i := strings.LastIndexByte(name, byte('.'))
+		if i < 0 {
+			return
+		}
+		result[0] = name[:i]
+		result[1] = name[i+1:] + "." + r.Value
+	case ExceptionType:
+		i := strings.IndexRune(r.Value, '.')
+		if i < 0 {
+			return
+		}
+		suffix := r.Value[i+1:]
+		name = strings.TrimSuffix(name, suffix)
+		if len(name) == 0 {
+			return
+		}
+		result[0] = name[:len(name)-1]
+		result[1] = suffix
 	}
-	return labels
+	return
 }
 
 // Labels decomposes given domain name into labels,
@@ -414,7 +428,6 @@ func DomainFromListWithOptions(l *List, name string, options *FindOptions) (stri
 	if err != nil {
 		return "", err
 	}
-
 	return dn.SLD + "." + dn.TLD, nil
 }
 
@@ -453,10 +466,10 @@ func normalize(name string) (string, error) {
 	ret := strings.ToLower(name)
 
 	if ret == "" {
-		return "", fmt.Errorf("Name is blank")
+		return "", fmt.Errorf("name is blank")
 	}
 	if ret[0] == '.' {
-		return "", fmt.Errorf("Name %s starts with a dot", ret)
+		return "", fmt.Errorf("name %s starts with a dot", ret)
 	}
 
 	return ret, nil