1 files changed, 130 insertions, 0 deletions
diff --git a/vendor/maunium.net/go/mautrix/userids.go b/vendor/maunium.net/go/mautrix/userids.go
new file mode 100644
index 0000000..ce6e02d
--- /dev/null
+++ b/vendor/maunium.net/go/mautrix/userids.go
@@ -0,0 +1,130 @@
+package mautrix
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"strings"
+)
+
+const lowerhex = "0123456789abcdef"
+
+// encode the given byte using quoted-printable encoding (e.g "=2f")
+// and writes it to the buffer
+// See https://golang.org/src/mime/quotedprintable/writer.go
+func encode(buf *bytes.Buffer, b byte) {
+	buf.WriteByte('=')
+	buf.WriteByte(lowerhex[b>>4])
+	buf.WriteByte(lowerhex[b&0x0f])
+}
+
+// escape the given alpha character and writes it to the buffer
+func escape(buf *bytes.Buffer, b byte) {
+	buf.WriteByte('_')
+	if b == '_' {
+		buf.WriteByte('_') // another _
+	} else {
+		buf.WriteByte(b + 0x20) // ASCII shift A-Z to a-z
+	}
+}
+
+func shouldEncode(b byte) bool {
+	return b != '-' && b != '.' && b != '_' && !(b >= '0' && b <= '9') && !(b >= 'a' && b <= 'z') && !(b >= 'A' && b <= 'Z')
+}
+
+func shouldEscape(b byte) bool {
+	return (b >= 'A' && b <= 'Z') || b == '_'
+}
+
+func isValidByte(b byte) bool {
+	return isValidEscapedChar(b) || (b >= '0' && b <= '9') || b == '.' || b == '=' || b == '-'
+}
+
+func isValidEscapedChar(b byte) bool {
+	return b == '_' || (b >= 'a' && b <= 'z')
+}
+
+// EncodeUserLocalpart encodes the given string into Matrix-compliant user ID localpart form.
+// See http://matrix.org/docs/spec/intro.html#mapping-from-other-character-sets
+//
+// This returns a string with only the characters "a-z0-9._=-". The uppercase range A-Z
+// are encoded using leading underscores ("_"). Characters outside the aforementioned ranges
+// (including literal underscores ("_") and equals ("=")) are encoded as UTF8 code points (NOT NCRs)
+// and converted to lower-case hex with a leading "=". For example:
+//   Alph@Bet_50up  => _alph=40_bet=5f50up
+func EncodeUserLocalpart(str string) string {
+	strBytes := []byte(str)
+	var outputBuffer bytes.Buffer
+	for _, b := range strBytes {
+		if shouldEncode(b) {
+			encode(&outputBuffer, b)
+		} else if shouldEscape(b) {
+			escape(&outputBuffer, b)
+		} else {
+			outputBuffer.WriteByte(b)
+		}
+	}
+	return outputBuffer.String()
+}
+
+// DecodeUserLocalpart decodes the given string back into the original input string.
+// Returns an error if the given string is not a valid user ID localpart encoding.
+// See http://matrix.org/docs/spec/intro.html#mapping-from-other-character-sets
+//
+// This decodes quoted-printable bytes back into UTF8, and unescapes casing. For
+// example:
+//  _alph=40_bet=5f50up  =>  Alph@Bet_50up
+// Returns an error if the input string contains characters outside the
+// range "a-z0-9._=-", has an invalid quote-printable byte (e.g. not hex), or has
+// an invalid _ escaped byte (e.g. "_5").
+func DecodeUserLocalpart(str string) (string, error) {
+	strBytes := []byte(str)
+	var outputBuffer bytes.Buffer
+	for i := 0; i < len(strBytes); i++ {
+		b := strBytes[i]
+		if !isValidByte(b) {
+			return "", fmt.Errorf("Byte pos %d: Invalid byte", i)
+		}
+
+		if b == '_' { // next byte is a-z and should be upper-case or is another _ and should be a literal _
+			if i+1 >= len(strBytes) {
+				return "", fmt.Errorf("Byte pos %d: expected _[a-z_] encoding but ran out of string", i)
+			}
+			if !isValidEscapedChar(strBytes[i+1]) { // invalid escaping
+				return "", fmt.Errorf("Byte pos %d: expected _[a-z_] encoding", i)
+			}
+			if strBytes[i+1] == '_' {
+				outputBuffer.WriteByte('_')
+			} else {
+				outputBuffer.WriteByte(strBytes[i+1] - 0x20) // ASCII shift a-z to A-Z
+			}
+			i++ // skip next byte since we just handled it
+		} else if b == '=' { // next 2 bytes are hex and should be buffered ready to be read as utf8
+			if i+2 >= len(strBytes) {
+				return "", fmt.Errorf("Byte pos: %d: expected quote-printable encoding but ran out of string", i)
+			}
+			dst := make([]byte, 1)
+			_, err := hex.Decode(dst, strBytes[i+1:i+3])
+			if err != nil {
+				return "", err
+			}
+			outputBuffer.WriteByte(dst[0])
+			i += 2 // skip next 2 bytes since we just handled it
+		} else { // pass through
+			outputBuffer.WriteByte(b)
+		}
+	}
+	return outputBuffer.String(), nil
+}
+
+// ExtractUserLocalpart extracts the localpart portion of a user ID.
+// See http://matrix.org/docs/spec/intro.html#user-identifiers
+func ExtractUserLocalpart(userID string) (string, error) {
+	if len(userID) == 0 || userID[0] != '@' {
+		return "", fmt.Errorf("%s is not a valid user id", userID)
+	}
+	return strings.TrimPrefix(
+		strings.SplitN(userID, ":", 2)[0], // @foo:bar:8448 => [ "@foo", "bar:8448" ]
+		"@",                               // remove "@" prefix
+	), nil
+}