feat(tui): even better model selector

1 files changed, 222 insertions, 20 deletions

diff --git a/packages/tui/internal/components/list/list.go b/packages/tui/internal/components/list/list.go
index 8a18d28fc..2405440fe 100644
--- a/packages/tui/internal/components/list/list.go
+++ b/packages/tui/internal/components/list/list.go
@@ -11,7 +11,8 @@ import (
 )
 
 type ListItem interface {
-	Render(selected bool, width int) string
+	Render(selected bool, width int, isFirstInViewport bool) string
+	Selectable() bool
 }
 
 type List[T ListItem] interface {
@@ -24,6 +25,8 @@ type List[T ListItem] interface {
 	SetSelectedIndex(idx int)
 	SetEmptyMessage(msg string)
 	IsEmpty() bool
+	GetMaxVisibleItems() int
+	GetActualHeight() int
 }
 
 type listComponent[T ListItem] struct {
@@ -72,14 +75,10 @@ func (c *listComponent[T]) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	case tea.KeyMsg:
 		switch {
 		case key.Matches(msg, simpleListKeys.Up) || (c.useAlphaNumericKeys && key.Matches(msg, simpleListKeys.UpAlpha)):
-			if c.selectedIdx > 0 {
-				c.selectedIdx--
-			}
+			c.moveUp()
 			return c, nil
 		case key.Matches(msg, simpleListKeys.Down) || (c.useAlphaNumericKeys && key.Matches(msg, simpleListKeys.DownAlpha)):
-			if c.selectedIdx < len(c.items)-1 {
-				c.selectedIdx++
-			}
+			c.moveDown()
 			return c, nil
 		}
 	}
@@ -87,8 +86,50 @@ func (c *listComponent[T]) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	return c, nil
 }
 
+// moveUp moves the selection up, skipping non-selectable items
+func (c *listComponent[T]) moveUp() {
+	if len(c.items) == 0 {
+		return
+	}
+
+	// Find the previous selectable item
+	for i := c.selectedIdx - 1; i >= 0; i-- {
+		if c.items[i].Selectable() {
+			c.selectedIdx = i
+			return
+		}
+	}
+
+	// If no selectable item found above, stay at current position
+}
+
+// moveDown moves the selection down, skipping non-selectable items
+func (c *listComponent[T]) moveDown() {
+	if len(c.items) == 0 {
+		return
+	}
+
+	originalIdx := c.selectedIdx
+	for {
+		if c.selectedIdx < len(c.items)-1 {
+			c.selectedIdx++
+		} else {
+			break
+		}
+
+		if c.items[c.selectedIdx].Selectable() {
+			return
+		}
+
+		// Prevent infinite loop
+		if c.selectedIdx == originalIdx {
+			break
+		}
+	}
+}
+
 func (c *listComponent[T]) GetSelectedItem() (T, int) {
-	if len(c.items) > 0 {
+	if len(c.items) > 0 && c.items[c.selectedIdx].Selectable() {
 		return c.items[c.selectedIdx], c.selectedIdx
 	}
 
@@ -97,8 +138,13 @@ func (c *listComponent[T]) GetSelectedItem() (T, int) {
 }
 
 func (c *listComponent[T]) SetItems(items []T) {
-	c.selectedIdx = 0
 	c.items = items
+	c.selectedIdx = 0
+
+	// Ensure initial selection is on a selectable item
+	if len(items) > 0 && !items[0].Selectable() {
+		c.moveDown()
+	}
 }
 
 func (c *listComponent[T]) GetItems() []T {
@@ -123,19 +169,19 @@ func (c *listComponent[T]) SetSelectedIndex(idx int) {
 	}
 }
 
-func (c *listComponent[T]) View() string {
+func (c *listComponent[T]) GetMaxVisibleItems() int {
+	return c.maxVisibleItems
+}
+
+func (c *listComponent[T]) GetActualHeight() int {
 	items := c.items
-	maxWidth := c.maxWidth
-	if maxWidth == 0 {
-		maxWidth = 80 // Default width if not set
+	if len(items) == 0 {
+		return 1 // For empty message
 	}
+
 	maxVisibleItems := min(c.maxVisibleItems, len(items))
 	startIdx := 0
 
-	if len(items) <= 0 {
-		return c.fallbackMsg
-	}
-
 	if len(items) > maxVisibleItems {
 		halfVisible := maxVisibleItems / 2
 		if c.selectedIdx >= halfVisible && c.selectedIdx < len(items)-halfVisible {
@@ -147,17 +193,142 @@ func (c *listComponent[T]) View() string {
 
 	endIdx := min(startIdx+maxVisibleItems, len(items))
 
-	listItems := make([]string, 0, maxVisibleItems)
+	height := 0
+	for i := startIdx; i < endIdx; i++ {
+		item := items[i]
+		isFirstInViewport := (i == startIdx)
+
+		// Check if this is a HeaderItem and calculate its height
+		if _, ok := any(item).(HeaderItem); ok {
+			if isFirstInViewport {
+				height += 1 // No top margin
+			} else {
+				height += 2 // With top margin
+			}
+		} else {
+			height += 1 // Regular items take 1 line
+		}
+	}
+
+	return height
+}
+
+func (c *listComponent[T]) View() string {
+	items := c.items
+	maxWidth := c.maxWidth
+	if maxWidth == 0 {
+		maxWidth = 80 // Default width if not set
+	}
+
+	if len(items) <= 0 {
+		return c.fallbackMsg
+	}
+
+	// Calculate viewport based on actual heights, not item counts
+	startIdx, endIdx := c.calculateViewport()
+
+	listItems := make([]string, 0, endIdx-startIdx)
 
 	for i := startIdx; i < endIdx; i++ {
 		item := items[i]
-		title := item.Render(i == c.selectedIdx, maxWidth)
+		isFirstInViewport := (i == startIdx)
+		title := item.Render(i == c.selectedIdx, maxWidth, isFirstInViewport)
 		listItems = append(listItems, title)
 	}
 
 	return strings.Join(listItems, "\n")
 }
 
+// calculateViewport determines which items to show based on available height
+func (c *listComponent[T]) calculateViewport() (startIdx, endIdx int) {
+	items := c.items
+	if len(items) == 0 {
+		return 0, 0
+	}
+
+	// Helper function to calculate height of an item at given position
+	getItemHeight := func(idx int, isFirst bool) int {
+		if _, ok := any(items[idx]).(HeaderItem); ok {
+			if isFirst {
+				return 1 // No top margin
+			} else {
+				return 2 // With top margin
+			}
+		}
+		return 1 // Regular items
+	}
+
+	// If we have fewer items than max, show all
+	if len(items) <= c.maxVisibleItems {
+		return 0, len(items)
+	}
+
+	// Try to center the selected item in the viewport
+	// Start by trying to put selected item in the middle
+	targetStart := c.selectedIdx - c.maxVisibleItems/2
+	if targetStart < 0 {
+		targetStart = 0
+	}
+
+	// Find the actual start and end indices that fit within our height budget
+	bestStart := 0
+	bestEnd := 0
+	bestHeight := 0
+
+	// Try different starting positions around our target
+	for start := max(0, targetStart-2); start <= min(len(items)-1, targetStart+2); start++ {
+		currentHeight := 0
+		end := start
+
+		for end < len(items) && currentHeight < c.maxVisibleItems {
+			itemHeight := getItemHeight(end, end == start)
+			if currentHeight+itemHeight > c.maxVisibleItems {
+				break
+			}
+			currentHeight += itemHeight
+			end++
+		}
+
+		// Check if this viewport contains the selected item and is better than current best
+		if start <= c.selectedIdx && c.selectedIdx < end {
+			if currentHeight > bestHeight || (currentHeight == bestHeight && abs(start+end-2*c.selectedIdx) < abs(bestStart+bestEnd-2*c.selectedIdx)) {
+				bestStart = start
+				bestEnd = end
+				bestHeight = currentHeight
+			}
+		}
+	}
+
+	// If no good viewport found that contains selected item, just show from selected item
+	if bestEnd == 0 {
+		bestStart = c.selectedIdx
+		currentHeight := 0
+		for bestEnd = bestStart; bestEnd < len(items) && currentHeight < c.maxVisibleItems; bestEnd++ {
+			itemHeight := getItemHeight(bestEnd, bestEnd == bestStart)
+			if currentHeight+itemHeight > c.maxVisibleItems {
+				break
+			}
+			currentHeight += itemHeight
+		}
+	}
+
+	return bestStart, bestEnd
+}
+
+func abs(x int) int {
+	if x < 0 {
+		return -x
+	}
+	return x
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
 func NewListComponent[T ListItem](
 	items []T,
 	maxVisibleItems int,
@@ -176,7 +347,7 @@ func NewListComponent[T ListItem](
 // StringItem is a simple implementation of ListItem for string values
 type StringItem string
 
-func (s StringItem) Render(selected bool, width int) string {
+func (s StringItem) Render(selected bool, width int, isFirstInViewport bool) string {
 	t := theme.CurrentTheme()
 	baseStyle := styles.NewStyle()
 
@@ -198,6 +369,37 @@ func (s StringItem) Render(selected bool, width int) string {
 	return itemStyle.Render(truncatedStr)
 }
 
+func (s StringItem) Selectable() bool {
+	return true
+}
+
+// HeaderItem is a non-selectable header item for grouping
+type HeaderItem string
+
+func (h HeaderItem) Render(selected bool, width int, isFirstInViewport bool) string {
+	t := theme.CurrentTheme()
+	baseStyle := styles.NewStyle()
+
+	truncatedStr := truncate.StringWithTail(string(h), uint(width-1), "...")
+
+	headerStyle := baseStyle.
+		Foreground(t.Accent()).
+		Bold(true).
+		MarginBottom(0).
+		PaddingLeft(1)
+
+	// Only add top margin if this is not the first item in the viewport
+	if !isFirstInViewport {
+		headerStyle = headerStyle.MarginTop(1)
+	}
+
+	return headerStyle.Render(truncatedStr)
+}
+
+func (h HeaderItem) Selectable() bool {
+	return false
+}
+
 // NewStringList creates a new list component with string items
 func NewStringList(
 	items []string,