v0.1.0 initial commit

tui/tree_state.go

@@ -0,0 +1,97 @@
+package tui
+
+// TreeState manages navigation state for a tree
+type TreeState struct {
+	Cursor  int
+	Scroll  int
+	Visible int // Viewport height
+}
+
+// NewTreeState creates initialized tree state
+func NewTreeState(visible int) *TreeState {
+	return &TreeState{
+		Visible: visible,
+	}
+}
+
+// --- Cursor movement ---
+
+// MoveCursor adjusts cursor position by delta
+func (t *TreeState) MoveCursor(delta, total int) {
+	t.Cursor += delta
+	if t.Cursor < 0 {
+		t.Cursor = 0
+	}
+	if t.Cursor >= total {
+		t.Cursor = total - 1
+	}
+	if t.Cursor < 0 {
+		t.Cursor = 0
+	}
+	t.AdjustScroll(total)
+}
+
+// AdjustScroll ensures cursor is visible
+func (t *TreeState) AdjustScroll(total int) {
+	if t.Visible <= 0 {
+		return
+	}
+	if t.Cursor < t.Scroll {
+		t.Scroll = t.Cursor
+	}
+	if t.Cursor >= t.Scroll+t.Visible {
+		t.Scroll = t.Cursor - t.Visible + 1
+	}
+	// Clamp scroll
+	maxScroll := total - t.Visible
+	if maxScroll < 0 {
+		maxScroll = 0
+	}
+	if t.Scroll > maxScroll {
+		t.Scroll = maxScroll
+	}
+	if t.Scroll < 0 {
+		t.Scroll = 0
+	}
+}
+
+// --- Jump navigation ---
+
+// JumpStart moves cursor to first item
+func (t *TreeState) JumpStart() {
+	t.Cursor = 0
+	t.Scroll = 0
+}
+
+// JumpEnd moves cursor to last item
+func (t *TreeState) JumpEnd(total int) {
+	if total > 0 {
+		t.Cursor = total - 1
+	}
+	t.AdjustScroll(total)
+}
+
+// --- Page navigation ---
+
+// PageUp scrolls up by half viewport
+func (t *TreeState) PageUp(total int) {
+	delta := t.Visible / 2
+	if delta < 1 {
+		delta = 1
+	}
+	t.MoveCursor(-delta, total)
+}
+
+// PageDown scrolls down by half viewport
+func (t *TreeState) PageDown(total int) {
+	delta := t.Visible / 2
+	if delta < 1 {
+		delta = 1
+	}
+	t.MoveCursor(delta, total)
+}
+
+// SetVisible updates viewport height
+func (t *TreeState) SetVisible(visible int) {
+	t.Visible = visible
+}