Move basic multi key shortcut handling into its own package

tools/tui/shortcuts/implementation.go

@@ -0,0 +1,64 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package shortcuts
+
+import (
+	"fmt"
+)
+
+var _ = fmt.Print
+
+func (self *ShortcutMap[T]) first_action() (ans T) {
+	for _, ac := range self.leaves {
+		return ac
+	}
+	for _, child := range self.children {
+		return child.first_action()
+	}
+	return
+}
+
+func (self *ShortcutMap[T]) shortcut_for(ac T) (keys []string) {
+	keys = []string{}
+	for key, q := range self.leaves {
+		if ac == q {
+			return append(keys, key)
+		}
+	}
+	for key, child := range self.children {
+		ckeys := child.shortcut_for(ac)
+		if len(ckeys) > 0 {
+			return append(append(keys, key), ckeys...)
+		}
+	}
+	return
+}
+
+func (self *ShortcutMap[T]) add(ac T, keys []string) (conflict T) {
+	sm := self
+	last := len(keys) - 1
+	for i, key := range keys {
+		if i == last {
+			if c, found := sm.leaves[key]; found {
+				conflict = c
+			}
+			sm.leaves[key] = ac
+			if c, found := sm.children[key]; found {
+				conflict = c.first_action()
+				delete(sm.children, key)
+			}
+		} else {
+			if c, found := sm.leaves[key]; found {
+				conflict = c
+				delete(sm.leaves, key)
+			}
+			q := sm.children[key]
+			if q == nil {
+				q = &ShortcutMap[T]{leaves: map[string]T{}, children: map[string]*ShortcutMap[T]{}}
+				sm.children[key] = q
+			}
+			sm = q
+		}
+	}
+	return
+}