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package model
type UndoStack struct {
states []Entry
pos int
}
type Entry struct {
Target *Map
State *Map
}
func (u *UndoStack) Push(target *Map) {
keep := u.pos + 1
if keep > len(u.states) {
keep = len(u.states)
}
u.states = append(u.states[:keep], Entry{Target: target, State: target.Clone()})
u.pos = len(u.states) - 1
if len(u.states) > 100 {
u.states = u.states[1:]
u.pos--
}
}
func (u *UndoStack) Undo() *Entry {
if u.pos <= 0 {
return nil
}
u.pos--
return &u.states[u.pos]
}
func (u *UndoStack) Redo() *Entry {
if u.pos >= len(u.states)-1 {
return nil
}
u.pos++
return &u.states[u.pos]
}
func (u *UndoStack) Pos() int { return u.pos }
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