exp/textinput: initialize a piece table by replacing

If the first operation is 'replace', disable undoing this.

Updates guigui-gui/guigui#279

exp/textinput/piecetable.go

@@ -150,10 +150,39 @@ func (p *pieceTable) Len() int {
 }
 
 func (p *pieceTable) replace(text string, start, end int) {
+	// If the first operation is 'replace', initialize the table.
+	if len(p.history) == 0 {
+		p.init(text)
+		return
+	}
+
 	p.maybeAppendHistory(text, start, end, 0, 0, 1, false)
 	p.doReplace(text, start, end)
 }
 
+func (p *pieceTable) init(text string) {
+	if len(p.history) > 0 {
+		panic("textinput: init should be called when history is empty")
+	}
+	if len(p.table) > 0 {
+		panic("textinput: init should be called when table is empty")
+	}
+
+	p.table = append(p.table, text...)
+	p.history = append(p.history, historyItem{
+		items: []pieceTableItem{
+			{
+				start: 0,
+				end:   len(text),
+			},
+		},
+		undoSelectionStart: 0,
+		undoSelectionEnd:   0,
+		redoSelectionStart: 0,
+		redoSelectionEnd:   len(text),
+	})
+}
+
 func (p *pieceTable) doReplace(text string, start, end int) {
 	items := p.history[p.historyIndex].items
 

exp/textinput/piecetable_test.go

@@ -574,7 +574,163 @@ func TestPieceTableHistoryMergingApplePressHold(t *testing.T) {
 	}
 	check("foo")
 
-	// Undo Op 1
+	// Undo Op 1 fails, as the initial state is determined by Replace.
+	start, end, ok = p.Undo()
+	if ok {
+		t.Fatal("Undo should fail")
+	}
+	check("foo")
+
+	// Redo Op 2, 3, 4, 5
+	start, end, ok = p.Redo()
+	if !ok {
+		t.Fatal("Redo failed")
+	}
+	if start != 3 || end != 7 {
+		t.Errorf("Redo: got (%d, %d), want (3, 7)", start, end)
+	}
+	check("fooàà")
+}
+
+func TestPieceTableInitialStateWithReplace(t *testing.T) {
+	var p textinput.PieceTable
+
+	check := func(want string) {
+		t.Helper()
+		var b strings.Builder
+		if _, err := p.WriteTo(&b); err != nil {
+			t.Fatalf("WriteTo failed: %v", err)
+		}
+		if got := b.String(); got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+	}
+
+	check("")
+
+	// Op 1
+	p.Replace("foo", 0, 0)
+	check("foo")
+
+	// Op 2
+	p.Replace("bar", 0, 3)
+	check("bar")
+
+	// Op 3
+	p.Replace("baz", 0, 3)
+	check("baz")
+
+	// Undo Op 3
+	start, end, ok := p.Undo()
+	if !ok {
+		t.Fatal("Undo failed")
+	}
+	if start != 0 || end != 3 {
+		t.Errorf("Undo: got (%d, %d), want (0, 3)", start, end)
+	}
+	check("bar")
+
+	// Undo Op 2
+	start, end, ok = p.Undo()
+	if !ok {
+		t.Fatal("Undo failed")
+	}
+	if start != 0 || end != 3 {
+		t.Errorf("Undo: got (%d, %d), want (0, 3)", start, end)
+	}
+	check("foo")
+
+	// Undo Op 1 fails, as the initial state is determined by Replace.
+	start, end, ok = p.Undo()
+	if ok {
+		t.Fatal("Undo should fail")
+	}
+	check("foo")
+
+	// Redo Op 2
+	start, end, ok = p.Redo()
+	if !ok {
+		t.Fatal("Redo failed")
+	}
+	if start != 0 || end != 3 {
+		t.Errorf("Redo: got (%d, %d), want (0, 3)", start, end)
+	}
+	check("bar")
+
+	// Redo Op 3
+	start, end, ok = p.Redo()
+	if !ok {
+		t.Fatal("Redo failed")
+	}
+	if start != 0 || end != 3 {
+		t.Errorf("Redo: got (%d, %d), want (0, 3)", start, end)
+	}
+	check("baz")
+}
+
+func TestPieceTableInitialStateWithUpdateIME(t *testing.T) {
+	var p textinput.PieceTable
+
+	check := func(want string) {
+		t.Helper()
+		var b strings.Builder
+		if _, err := p.WriteTo(&b); err != nil {
+			t.Fatalf("WriteTo failed: %v", err)
+		}
+		if got := b.String(); got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+	}
+
+	check("")
+
+	// Op 1
+	p.UpdateByIME(textinput.TextInputState{Text: "foo"}, 0, 0)
+	check("foo")
+
+	// Op 2
+	p.Replace("", 0, 3)
+	check("")
+
+	// Op 3
+	p.Replace("bar", 0, 0)
+	check("bar")
+
+	// Op 4
+	p.Replace("baz", 0, 3)
+	check("baz")
+
+	// Undo Op 4
+	start, end, ok := p.Undo()
+	if !ok {
+		t.Fatal("Undo failed")
+	}
+	if start != 0 || end != 3 {
+		t.Errorf("Undo: got (%d, %d), want (0, 3)", start, end)
+	}
+	check("bar")
+
+	// Undo Op 3
+	start, end, ok = p.Undo()
+	if !ok {
+		t.Fatal("Undo failed")
+	}
+	if start != 0 || end != 0 {
+		t.Errorf("Undo: got (%d, %d), want (0, 0)", start, end)
+	}
+	check("")
+
+	// Undo Op 2
+	start, end, ok = p.Undo()
+	if !ok {
+		t.Fatal("Undo failed")
+	}
+	if start != 0 || end != 3 {
+		t.Errorf("Undo: got (%d, %d), want (0, 3)", start, end)
+	}
+	check("foo")
+
+	// Undo Op 1 succeeds, as the first operation is UpdateByIME.
 	start, end, ok = p.Undo()
 	if !ok {
 		t.Fatal("Undo failed")
@@ -594,13 +750,33 @@ func TestPieceTableHistoryMergingApplePressHold(t *testing.T) {
 	}
 	check("foo")
 
-	// Redo Op 2, 3, 4, 5
+	// Redo Op 2
 	start, end, ok = p.Redo()
 	if !ok {
 		t.Fatal("Redo failed")
 	}
-	if start != 3 || end != 7 {
-		t.Errorf("Redo: got (%d, %d), want (3, 7)", start, end)
+	if start != 0 || end != 0 {
+		t.Errorf("Redo: got (%d, %d), want (0, 0)", start, end)
 	}
-	check("fooàà")
+	check("")
+
+	// Redo Op 3
+	start, end, ok = p.Redo()
+	if !ok {
+		t.Fatal("Redo failed")
+	}
+	if start != 0 || end != 3 {
+		t.Errorf("Redo: got (%d, %d), want (0, 3)", start, end)
+	}
+	check("bar")
+
+	// Redo Op 4
+	start, end, ok = p.Redo()
+	if !ok {
+		t.Fatal("Redo failed")
+	}
+	if start != 0 || end != 3 {
+		t.Errorf("Redo: got (%d, %d), want (0, 3)", start, end)
+	}
+	check("baz")
 }