refactor(copy): add immutable history views

commit: 296e94c10516e6bc5579af126bd487940e5abf12
author: brice · 3mo ago · 2026-07-11 05:51 UTC
committer: brice · 3mo ago · 2026-07-11 06:15 UTC
parent: bf7a30f
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

2 files · +60 -0

M internal/usecase/copy/scrollback.go +26 -0


@@ -56,6 +56,32 @@ func (s *Scrollback) Snapshot() [][]renderer.Cell {
56	56		return rows
57	57		}
58	58
	59	+	// HistoryView is a frozen oldest-first view of scrollback rows.
	60	+	//
	61	+	// Its rows share cell slices with the scrollback at the time View is called.
	62	+	// Callers must treat rows returned by Row as read-only.
	63	+	type HistoryView struct {
	64	+	rows [][]renderer.Cell
	65	+	}
	66	+
	67	+	// View returns a frozen scrollback view. Appending to the scrollback cannot
	68	+	// alter the view because Append replaces ring slots rather than mutating rows.
	69	+	func (s *Scrollback) View() HistoryView {
	70	+	return HistoryView{rows: s.Snapshot()}
	71	+	}
	72	+
	73	+	// Len returns the number of rows in the view.
	74	+	func (v HistoryView) Len() int { return len(v.rows) }
	75	+
	76	+	// Row returns the row at logical index i, oldest first, or nil when i is out
	77	+	// of range. Returned rows are shared with the view and must be read-only.
	78	+	func (v HistoryView) Row(i int) []renderer.Cell {
	79	+	if i < 0 \|\| i >= len(v.rows) {
	80	+	return nil
	81	+	}
	82	+	return v.rows[i]
	83	+	}
	84	+
59	85		// Row returns a copy of the retained row at logical index i, oldest first.
60	86		func (s *Scrollback) Row(i int) []renderer.Cell {
61	87		if i < 0 \|\| i >= s.len \|\| len(s.rows) == 0 {


@@ -56,6 +56,32 @@ func (s *Scrollback) Snapshot() [][]renderer.Cell {
56	return rows	56		return rows
57	}	57		}
58		58
		59	+	// HistoryView is a frozen oldest-first view of scrollback rows.
		60	+	//
		61	+	// Its rows share cell slices with the scrollback at the time View is called.
		62	+	// Callers must treat rows returned by Row as read-only.
		63	+	type HistoryView struct {
		64	+	rows [][]renderer.Cell
		65	+	}
		66	+
		67	+	// View returns a frozen scrollback view. Appending to the scrollback cannot
		68	+	// alter the view because Append replaces ring slots rather than mutating rows.
		69	+	func (s *Scrollback) View() HistoryView {
		70	+	return HistoryView{rows: s.Snapshot()}
		71	+	}
		72	+
		73	+	// Len returns the number of rows in the view.
		74	+	func (v HistoryView) Len() int { return len(v.rows) }
		75	+
		76	+	// Row returns the row at logical index i, oldest first, or nil when i is out
		77	+	// of range. Returned rows are shared with the view and must be read-only.
		78	+	func (v HistoryView) Row(i int) []renderer.Cell {
		79	+	if i < 0 \|\| i >= len(v.rows) {
		80	+	return nil
		81	+	}
		82	+	return v.rows[i]
		83	+	}
		84	+
59	// Row returns a copy of the retained row at logical index i, oldest first.	85		// Row returns a copy of the retained row at logical index i, oldest first.
60	func (s *Scrollback) Row(i int) []renderer.Cell {	86		func (s *Scrollback) Row(i int) []renderer.Cell {
61	if i < 0 \|\| i >= s.len \|\| len(s.rows) == 0 {	87		if i < 0 \|\| i >= s.len \|\| len(s.rows) == 0 {

M internal/usecase/copy/scrollback_test.go +34 -0


@@ -175,3 +175,37 @@ func TestScrollbackAppendDoesNotMutateSnapshottedRows(t *testing.T) {
175	175		t.Fatalf("snapshot[1] after append = %q, want original row", text)
176	176		}
177	177		}
	178	+
	179	+	func TestScrollbackViewSurvivesCompleteRingOverwrite(t *testing.T) {
	180	+	sb := NewScrollback(2)
	181	+	sb.Append(row("aa"))
	182	+	sb.Append(row("bb"))
	183	+	view := sb.View()
	184	+	if &view.Row(0)[0] != &sb.rows[0][0] {
	185	+	t.Fatal("View() deep-copied cells, want shared row storage")
	186	+	}
	187	+
	188	+	sb.Append(row("cc"))
	189	+	sb.Append(row("dd"))
	190	+
	191	+	if got := view.Len(); got != 2 {
	192	+	t.Fatalf("View().Len() = %d, want 2", got)
	193	+	}
	194	+	for i, want := range []string{"aa", "bb"} {
	195	+	if got := rowText(view.Row(i)); got != want {
	196	+	t.Fatalf("View().Row(%d) = %q, want %q", i, got, want)
	197	+	}
	198	+	}
	199	+	}
	200	+
	201	+	func TestHistoryViewRowBounds(t *testing.T) {
	202	+	sb := NewScrollback(1)
	203	+	sb.Append(row("aa"))
	204	+	view := sb.View()
	205	+
	206	+	for _, i := range []int{-1, 1} {
	207	+	if got := view.Row(i); got != nil {
	208	+	t.Errorf("View().Row(%d) = %v, want nil", i, got)
	209	+	}
	210	+	}
	211	+	}


@@ -175,3 +175,37 @@ func TestScrollbackAppendDoesNotMutateSnapshottedRows(t *testing.T) {
175	t.Fatalf("snapshot[1] after append = %q, want original row", text)	175		t.Fatalf("snapshot[1] after append = %q, want original row", text)
176	}	176		}
177	}	177		}
		178	+
		179	+	func TestScrollbackViewSurvivesCompleteRingOverwrite(t *testing.T) {
		180	+	sb := NewScrollback(2)
		181	+	sb.Append(row("aa"))
		182	+	sb.Append(row("bb"))
		183	+	view := sb.View()
		184	+	if &view.Row(0)[0] != &sb.rows[0][0] {
		185	+	t.Fatal("View() deep-copied cells, want shared row storage")
		186	+	}
		187	+
		188	+	sb.Append(row("cc"))
		189	+	sb.Append(row("dd"))
		190	+
		191	+	if got := view.Len(); got != 2 {
		192	+	t.Fatalf("View().Len() = %d, want 2", got)
		193	+	}
		194	+	for i, want := range []string{"aa", "bb"} {
		195	+	if got := rowText(view.Row(i)); got != want {
		196	+	t.Fatalf("View().Row(%d) = %q, want %q", i, got, want)
		197	+	}
		198	+	}
		199	+	}
		200	+
		201	+	func TestHistoryViewRowBounds(t *testing.T) {
		202	+	sb := NewScrollback(1)
		203	+	sb.Append(row("aa"))
		204	+	view := sb.View()
		205	+
		206	+	for _, i := range []int{-1, 1} {
		207	+	if got := view.Row(i); got != nil {
		208	+	t.Errorf("View().Row(%d) = %v, want nil", i, got)
		209	+	}
		210	+	}
		211	+	}