plugin: add identity and recipient encoding

plugin/encode.go

@@ -0,0 +1,55 @@
+// Copyright 2023 The age Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package plugin
+
+import (
+	"fmt"
+	"strings"
+
+	"filippo.io/age/internal/bech32"
+)
+
+// EncodeIdentity encodes a plugin identity string for a plugin with the given
+// name. If the name is invalid, it returns an empty string.
+func EncodeIdentity(name string, data []byte) string {
+	s, _ := bech32.Encode("AGE-PLUGIN-"+strings.ToUpper(name)+"-", data)
+	return s
+}
+
+// ParseIdentity decodes a plugin identity string. It returns the plugin name
+// in lowercase and the encoded data.
+func ParseIdentity(s string) (name string, data []byte, err error) {
+	hrp, data, err := bech32.Decode(s)
+	if err != nil {
+		return "", nil, fmt.Errorf("invalid identity encoding: %v", err)
+	}
+	if !strings.HasPrefix(hrp, "AGE-PLUGIN-") || !strings.HasSuffix(hrp, "-") {
+		return "", nil, fmt.Errorf("not a plugin identity: %v", err)
+	}
+	name = strings.TrimSuffix(strings.TrimPrefix(hrp, "AGE-PLUGIN-"), "-")
+	name = strings.ToLower(name)
+	return name, data, nil
+}
+
+// EncodeRecipient encodes a plugin recipient string for a plugin with the given
+// name. If the name is invalid, it returns an empty string.
+func EncodeRecipient(name string, data []byte) string {
+	s, _ := bech32.Encode("age1"+strings.ToLower(name), data)
+	return s
+}
+
+// ParseRecipient decodes a plugin recipient string. It returns the plugin name
+// in lowercase and the encoded data.
+func ParseRecipient(s string) (name string, data []byte, err error) {
+	hrp, data, err := bech32.Decode(s)
+	if err != nil {
+		return "", nil, fmt.Errorf("invalid recipient encoding: %v", err)
+	}
+	if !strings.HasPrefix(hrp, "age1") {
+		return "", nil, fmt.Errorf("not a plugin recipient: %v", err)
+	}
+	name = strings.TrimPrefix(hrp, "age1")
+	return name, data, nil
+}