package browser

import (
	"pad/internal/ui"
)

// BrowserLayout computes the element tree for the browser (file listing) page.
// Pure function: (screen dimensions, browser state, sort handler) → []ui.Element
func BrowserLayout(screenW, screenH ui.Dp, state *BrowserState, sortHandler func(any)) []ui.Element {
	margin := ui.Dp(10)
	contentWidth := screenW - margin*2

	// --- Header bar: directory path + sort toggle ---
	headerHeight := ui.Dp(24)
	headerRegion := ui.Region{
		X: margin, Y: margin,
		W: contentWidth, H: headerHeight,
	}
	sortLabel := sortModeLabel(state.SortMode)
	headerBar := ui.NewContainer(
		headerRegion,
		ui.Color{R: 230, G: 230, B: 230, A: 255},
		[]ui.Element{
			ui.NewLabel(state.CurrentPath, 14, ui.Region{X: 0, Y: 0, W: contentWidth, H: headerHeight}, ui.AlignStart, "", nil),
			ui.NewLabel(sortLabel, 12, ui.Region{X: 0, Y: 0, W: contentWidth, H: headerHeight}, ui.AlignEnd, "sort",
				[]ui.Interaction{{Gesture: ui.Tap, Handler: sortHandler}}),
		},
	)

	// --- Search bar (Gio editor) ---
	searchHeight := ui.Dp(36)
	searchY := headerRegion.Y + headerRegion.H + margin/2
	searchRegion := ui.Region{
		X: margin, Y: searchY,
		W: contentWidth, H: searchHeight,
	}
	state.SearchEditor.SingleLine = true
	searchBar := ui.NewGioEditor("search_bar", searchRegion, &state.SearchEditor)

	var searchPlaceholder ui.Element
	if state.SearchEditor.Len() == 0 {
		searchPlaceholder = ui.NewLabel("Search…", 14,
			ui.Region{X: margin + ui.Dp(8), Y: searchY + ui.Dp(8), W: contentWidth - ui.Dp(16), H: searchHeight - ui.Dp(16)},
			ui.AlignStart, "", nil)
	}

	// --- ListView ---
	listY := searchY + searchHeight + margin/2
	listHeight := screenH - listY - margin
	listRegion := ui.Region{
		X: margin, Y: listY,
		W: contentWidth, H: listHeight,
	}

	// Compute visible entries
	visibleEntries := computeVisibleEntries(state)

	// Create a scroll handler that captures the current browser state
	scrollHandler := func(data any) {
		delta := data.(int) // entries
		HandleScroll(state, delta)
	}

	listView := ui.NewListView(
		"browser_list",
		visibleEntries,
		listRegion,
		ui.Dp(state.ScrollIndex)*ui.Dp(48), // scroll offset in pixels
		state.SelectedIndex,
		[]ui.Interaction{{Gesture: ui.Scroll, Handler: scrollHandler}},
	)

	elems := []ui.Element{headerBar, searchBar}
	if searchPlaceholder != nil {
		elems = append(elems, searchPlaceholder)
	}
	elems = append(elems, listView)
	return elems
}

// sortModeLabel returns the display label for the given sort mode.
func sortModeLabel(mode SortMode) string {
	switch mode {
	case SortModeNameAsc:
		return "Name ↑"
	case SortModeNameDesc:
		return "Name ↓"
	case SortModeDateAsc:
		return "Date ↑"
	case SortModeDateDesc:
		return "Date ↓"
	default:
		return "Name ↑"
	}
}



// ComputeVisibleEntriesForTest is exported for testing purposes.
// It builds the list of ui.ListItem entries that should be rendered.
func ComputeVisibleEntriesForTest(state *BrowserState) []ui.ListItem {
	return computeVisibleEntries(state)
}

// computeVisibleEntries builds the list of ui.ListItem entries that should be
// rendered based on the current scroll position and visible count.
func computeVisibleEntries(state *BrowserState) []ui.ListItem {
	if state.TotalEntries == 0 {
		return nil
	}

	startIndex := state.ScrollIndex
	endIndex := startIndex + state.VisibleCount
	if endIndex > state.TotalEntries {
		endIndex = state.TotalEntries
	}

	var items []ui.ListItem
	for idx := startIndex; idx < endIndex; idx++ {
		entry, ok := getEntryByIndex(state, idx)
		if !ok {
			// Page not loaded yet; add placeholder
			items = append(items, ui.ListItem{
				Text:    "...",
				Subtext: "Loading...",
			})
			continue
		}
		item := entry.ToListItem()
		item.Selected = (idx == state.SelectedIndex)
		items = append(items, item)
	}

	return items
}