Rewrite irc2md()

mm-go-irckit/server_commands.go

@@ -814,73 +814,69 @@ func CmdWhois(s Server, u *User, msg *irc.Message) error {
 
 //nolint:funlen,gocognit,gocyclo,cyclop
 func irc2md(msg string) string {
-	data := []byte(msg)
+	emphasis_supported := map[byte][]byte{
+		'\x02': []byte{'*', '*'}, // Bold      0x02  **   (**text**)
+		'\x1d': []byte{'_'},      // Italics   0x1D  _    (_text_)
+		'\x11': []byte{'`'},      // Monospace 0x11  `    (`text`)
+		'\x0f': []byte{' '},      // Reset     0x0F       (**text\x0f)
+	}
+	emphasis_unsupported := map[byte]string{
+		'\x1f': "", // Underline 0x1f
+		'\x1e': "", // Strikethr 0x1e
+	}
 
 	var buf []byte
-	emphasis := ""
-	for _, char := range data {
-		switch {
-		// Bold      0x02  **   (**text**)
-		case char == '\x02' && emphasis == "":
-			buf = append(buf, '*', '*')
-			emphasis = "b"
-		case char == '\x02' && emphasis == "b":
-			buf = append(buf, '*', '*')
-			emphasis = ""
-		// Italics   0x1D  _    (_text_)
-		case char == '\x1d' && emphasis == "":
-			buf = append(buf, '_')
-			emphasis = "i"
-		case char == '\x1d' && emphasis == "i":
-			buf = append(buf, '_')
-			emphasis = ""
-		// Bold+Ital 0x02+0x1D **_  (**_text_**)
-		case char == '\x1d' && emphasis == "b":
-			buf = append(buf, '_')
-			emphasis = "bi"
-		case char == '\x1d' && emphasis == "bi":
-			buf = append(buf, '_')
-			emphasis = "b"
-		// Monospace 0x11  `    (`text`)
-		case char == '\x11' && emphasis == "":
-			buf = append(buf, '`')
-			emphasis = "m"
-		case char == '\x11' && emphasis == "m":
-			buf = append(buf, '`')
-			emphasis = ""
-
-		// Reset     0x0F       (**text\x0f)
-		case char == '\x0f' && emphasis != "":
-			switch {
-			case emphasis == "b":
-				buf = append(buf, '*', '*')
-				emphasis = ""
-			case emphasis == "i":
-				buf = append(buf, '_')
-				emphasis = ""
-			case emphasis == "bi":
-				buf = append(buf, '_', '*', '*')
-				emphasis = ""
-			case emphasis == "m":
-				buf = append(buf, '`')
-				emphasis = ""
-			}
 
-		default:
+	var cur_emphasis []byte
+	for _, char := range []byte(msg) {
+		var ok bool
+		var emp []byte
+
+		if _, ok = emphasis_unsupported[char]; ok {
 			buf = append(buf, char)
+			continue
+		}
+
+		if emp, ok = emphasis_supported[char]; !ok {
+			buf = append(buf, char)
+			continue
+		}
+
+		// Reset formatting
+		if char == '\x0f' {
+			// Close off any current emphasis
+			for _, c := range cur_emphasis {
+				buf = append(buf, emphasis_supported[c]...)
+			}
+			cur_emphasis = nil
+			continue
+		}
+
+		buf = append(buf, emp...)
+
+		// Remove closing emphasis.
+		found := false
+		var new_emphasis []byte
+		for _, c := range cur_emphasis {
+			if !found && c == char {
+				found = true
+				continue
+			}
+			new_emphasis = append(new_emphasis, c)
+		}
+
+		if found {
+			cur_emphasis = new_emphasis
+			continue
 		}
+
+		cur_emphasis = append([]byte{char}, cur_emphasis...)
 	}
 
-	switch {
-	case emphasis == "b":
-		buf = append(buf, '*', '*')
-	case emphasis == "i":
-		buf = append(buf, '_')
-	case emphasis == "bi":
-		buf = append(buf, '_', '*', '*')
-	case emphasis == "m":
-		buf = append(buf, '`')
+	for _, c := range cur_emphasis {
+		buf = append(buf, emphasis_supported[c]...)
 	}
+	cur_emphasis = nil
 
 	return string(buf)
 }