From eb25ddd86499c209a0b8290561ac2c075b29a59a Mon Sep 17 00:00:00 2001
From: vsariola <vsariola@users.noreply.github.com>
Date: Fri, 8 Jan 2021 22:00:15 +0200
Subject: [PATCH] feat(tracker): implement simple undo / redo

---
 tracker/keyevent.go | 33 ++++++++++++++++++++++-----------
 tracker/tracker.go  | 22 ++++++++++++++++++++++
 tracker/undo.go     | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+), 11 deletions(-)
 create mode 100644 tracker/undo.go

diff --git a/tracker/keyevent.go b/tracker/keyevent.go
index 4978274..b7e2c85 100644
--- a/tracker/keyevent.go
+++ b/tracker/keyevent.go
@@ -45,18 +45,17 @@ var noteMap = map[string]int{
 // KeyEvent handles incoming key events and returns true if repaint is needed.
 func (t *Tracker) KeyEvent(e key.Event) bool {
 	if e.State == key.Press {
-		if t.CursorColumn == 0 {
-			if val, ok := noteMap[e.Name]; ok {
-				t.NotePressed(val)
-				return true
-			}
-		} else {
-			if iv, err := strconv.ParseInt(e.Name, 16, 8); err == nil {
-				t.NumberPressed(byte(iv))
-				return true
-			}
-		}
 		switch e.Name {
+		case "Z":
+			if e.Modifiers.Contain(key.ModCtrl) {
+				t.Undo()
+				return true
+			}
+		case "Y":
+			if e.Modifiers.Contain(key.ModCtrl) {
+				t.Redo()
+				return true
+			}
 		case "A":
 			t.setCurrent(0)
 			return true
@@ -114,6 +113,17 @@ func (t *Tracker) KeyEvent(e key.Event) bool {
 			t.CursorColumn = 0
 			return true
 		}
+		if t.CursorColumn == 0 {
+			if val, ok := noteMap[e.Name]; ok {
+				t.NotePressed(val)
+				return true
+			}
+		} else {
+			if iv, err := strconv.ParseInt(e.Name, 16, 8); err == nil {
+				t.NumberPressed(byte(iv))
+				return true
+			}
+		}
 	}
 	return false
 }
@@ -135,6 +145,7 @@ func (t *Tracker) moveCursor(delta int) {
 
 // setCurrent sets the (note) value in current pattern under cursor to iv
 func (t *Tracker) setCurrent(iv byte) {
+	t.SaveUndo()
 	t.song.Tracks[t.ActiveTrack].Patterns[t.song.Tracks[t.ActiveTrack].Sequence[t.DisplayPattern]][t.CursorRow] = iv
 }
 
diff --git a/tracker/tracker.go b/tracker/tracker.go
index 66878c9..6753f0a 100644
--- a/tracker/tracker.go
+++ b/tracker/tracker.go
@@ -44,6 +44,8 @@ type Tracker struct {
 	synth        sointu.Synth
 	playBuffer   []float32
 	closer       chan struct{}
+	undoStack    []sointu.Song
+	redoStack    []sointu.Song
 }
 
 func (t *Tracker) LoadSong(song sointu.Song) error {
@@ -59,6 +61,21 @@ func (t *Tracker) LoadSong(song sointu.Song) error {
 	} else {
 		t.synth = synth
 	}
+	if t.DisplayPattern >= song.SequenceLength() {
+		t.DisplayPattern = song.SequenceLength() - 1
+	}
+	if t.CursorRow >= song.PatternRows() {
+		t.CursorRow = song.PatternRows() - 1
+	}
+	if t.PlayPattern >= song.SequenceLength() {
+		t.PlayPattern = song.SequenceLength() - 1
+	}
+	if t.PlayRow >= song.PatternRows() {
+		t.PlayRow = song.PatternRows() - 1
+	}
+	if t.ActiveTrack >= len(song.Tracks) {
+		t.ActiveTrack = len(song.Tracks) - 1
+	}
 	return nil
 }
 
@@ -153,6 +170,7 @@ func (t *Tracker) ChangeOctave(delta int) bool {
 }
 
 func (t *Tracker) ChangeBPM(delta int) bool {
+	t.SaveUndo()
 	newBPM := t.song.BPM + delta
 	if newBPM < 1 {
 		newBPM = 1
@@ -169,6 +187,7 @@ func (t *Tracker) ChangeBPM(delta int) bool {
 }
 
 func (t *Tracker) AddTrack() {
+	t.SaveUndo()
 	if t.song.TotalTrackVoices() < t.song.Patch.TotalVoices() {
 		seq := make([]byte, t.song.SequenceLength())
 		patterns := [][]byte{make([]byte, t.song.PatternRows())}
@@ -181,6 +200,7 @@ func (t *Tracker) AddTrack() {
 }
 
 func (t *Tracker) AddInstrument() {
+	t.SaveUndo()
 	if t.song.Patch.TotalVoices() < 32 {
 		units := make([]sointu.Unit, len(defaultInstrument.Units))
 		for i, defUnit := range defaultInstrument.Units {
@@ -220,6 +240,8 @@ func New(audioContext sointu.AudioContext) *Tracker {
 		patternJump:      make(chan int),
 		ticked:           make(chan struct{}),
 		closer:           make(chan struct{}),
+		undoStack:        []sointu.Song{},
+		redoStack:        []sointu.Song{},
 	}
 	t.Theme.Color.Primary = color.RGBA{R: 64, G: 64, B: 64, A: 255}
 	go t.sequencerLoop(t.closer)
diff --git a/tracker/undo.go b/tracker/undo.go
new file mode 100644
index 0000000..cf1fb86
--- /dev/null
+++ b/tracker/undo.go
@@ -0,0 +1,37 @@
+package tracker
+
+var undoSkip = map[string]int{
+	"setNote": 10,
+}
+
+const maxUndo = 256
+
+func (t *Tracker) SaveUndo() {
+	if len(t.undoStack) >= maxUndo {
+		t.undoStack = t.undoStack[1:]
+	}
+	t.undoStack = append(t.undoStack, t.song.Copy())
+	t.redoStack = t.redoStack[:0]
+}
+
+func (t *Tracker) Undo() {
+	if len(t.undoStack) > 0 {
+		if len(t.redoStack) >= maxUndo {
+			t.redoStack = t.redoStack[1:]
+		}
+		t.redoStack = append(t.redoStack, t.song.Copy())
+		t.LoadSong(t.undoStack[len(t.undoStack)-1])
+		t.undoStack = t.undoStack[:len(t.undoStack)-1]
+	}
+}
+
+func (t *Tracker) Redo() {
+	if len(t.redoStack) > 0 {
+		if len(t.undoStack) >= maxUndo {
+			t.undoStack = t.undoStack[1:]
+		}
+		t.undoStack = append(t.undoStack, t.song.Copy())
+		t.LoadSong(t.redoStack[len(t.redoStack)-1])
+		t.redoStack = t.redoStack[:len(t.redoStack)-1]
+	}
+}