AMP Cache Origin changes as described in ampproject/amphtml#26205

PiperOrigin-RevId: 298721329

transformer/internal/amphtml/urls.go

@@ -231,6 +231,7 @@ func ToCacheURLSubdomain(originHost string) string {
 	if err != nil {
 		return fallbackCacheURLSubdomain(originHost)
 	}
+
 	var sb strings.Builder
 	for _, rune := range unicode {
 		switch rune {
@@ -242,12 +243,36 @@ func ToCacheURLSubdomain(originHost string) string {
 			sb.WriteRune(rune)
 		}
 	}
-	if result, err := p.ToASCII(sb.String()); err == nil && strings.ContainsRune(sb.String(), '-') {
+
+	utf8 := sb.String()
+	result, err := p.ToASCII(utf8)
+	if err == nil && isValidCurls(result) {
 		return result
 	}
+
+	// If there was an error due to the hyphen being in positions 3 and 4, try
+	// to create a human readable version for CURLS label v2. Since err does not
+	// tell us the specific error, check the hyphens manually.
+	if utf8[2] == '-' && utf8[3] == '-' {
+		var sb2 strings.Builder
+		sb2.WriteString("0-")
+		sb2.WriteString(utf8)
+		sb2.WriteString("-0")
+
+		utf8 = sb2.String()
+		result, err = p.ToASCII(utf8)
+		if err == nil && isValidCurls(result) {
+			return result
+		}
+	}
+
 	return fallbackCacheURLSubdomain(originHost)
 }
 
+func isValidCurls(result string) bool {
+	return strings.ContainsRune(result, '-')
+}
+
 
 func fallbackCacheURLSubdomain(originHost string) string {
 	sha := sha256.New()

transformer/internal/amphtml/urls_test.go

@@ -366,12 +366,12 @@ func TestToCacheURLDomain(t *testing.T) {
 		{
 			desc:     "R-LDH #2",
 			input:    "in-trouble.com",
-			expected: "j7pweznglei73fva3bo6oidjt74j3hx4tfyncjsdwud7r7cci4va",
+			expected: "0-in--trouble-com-0",
 		},
 		{
 			desc:     "R-LDH #3",
 			input:    "a--problem.com",
-			expected: "a47psvede4jpgjom2kzmuhop74zzmdpjzasoctyoqqaxbkdbsyiq",
+			expected: "0-a----problem-com-0",
 		},
 		{
 			desc:     "Transition mapping per UTS #46",

transformer/transformer_test.go

@@ -6,7 +6,7 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/golang/protobuf/proto"
+	"google3/net/proto2/go/proto"
 	rpb "github.com/ampproject/amppackager/transformer/request"
 	"github.com/ampproject/amppackager/transformer/transformers"
 	"github.com/google/go-cmp/cmp"