fix #1074

Make snomask add/remove behavior match other ircds

irc/sno/utils.go

@@ -0,0 +1,87 @@
+// Copyright (c) 2020 Shivaram Lingamneni
+// released under the MIT license
+
+package sno
+
+import (
+	"strings"
+)
+
+func IsValidMask(r rune) bool {
+	for _, m := range ValidMasks {
+		if m == Mask(r) {
+			return true
+		}
+	}
+	return false
+}
+
+func (masks Masks) String() string {
+	var buf strings.Builder
+	buf.Grow(len(masks))
+	for _, m := range masks {
+		buf.WriteRune(rune(m))
+	}
+	return buf.String()
+}
+
+func (masks Masks) Contains(mask Mask) bool {
+	for _, m := range masks {
+		if mask == m {
+			return true
+		}
+	}
+	return false
+}
+
+// Evaluate changes to snomasks made with MODE. There are several cases:
+// adding snomasks with `/mode +s a` or `/mode +s +a`, removing them with `/mode +s -a`,
+// adding all with `/mode +s *` or `/mode +s +*`, removing all with `/mode +s -*` or `/mode -s`
+func EvaluateSnomaskChanges(add bool, arg string, currentMasks Masks) (addMasks, removeMasks Masks, newArg string) {
+	if add {
+		if len(arg) == 0 {
+			return
+		}
+		add := true
+		switch arg[0] {
+		case '+':
+			arg = arg[1:]
+		case '-':
+			add = false
+			arg = arg[1:]
+		default:
+			// add
+		}
+		if strings.IndexByte(arg, '*') != -1 {
+			if add {
+				for _, mask := range ValidMasks {
+					if !currentMasks.Contains(mask) {
+						addMasks = append(addMasks, mask)
+					}
+				}
+			} else {
+				removeMasks = currentMasks
+			}
+		} else {
+			for _, r := range arg {
+				if IsValidMask(r) {
+					m := Mask(r)
+					if add && !currentMasks.Contains(m) {
+						addMasks = append(addMasks, m)
+					} else if !add && currentMasks.Contains(m) {
+						removeMasks = append(removeMasks, m)
+					}
+				}
+			}
+		}
+		if len(addMasks) != 0 {
+			newArg = "+" + addMasks.String()
+		} else if len(removeMasks) != 0 {
+			newArg = "-" + removeMasks.String()
+		}
+	} else {
+		removeMasks = currentMasks
+		newArg = ""
+	}
+	return
+}