// Package components provides custom tview primitives for the Nebara OS TUI.
// Each component is self-contained and themed using the centralized design system.
package components

import (
	"github.com/gdamore/tcell/v2"
	"github.com/nebara/nebara-os/internal/model"
	"github.com/nebara/nebara-os/internal/ui/theme"
	"github.com/rivo/tview"
)

// MenuWidget is a custom tview.Primitive that renders the navigation menu
// with full-width row highlighting, a single-cell border, and inner padding.
// It implements the exact Figma selection design: full-width BBBBBB background.
type MenuWidget struct {
	*tview.Box

	items       []model.MenuItem
	selectedIdx int
	innerPad    int // horizontal cells of padding inside the border

	// onSelectionChanged is called whenever the selected index changes.
	onSelectionChanged func(idx int)
	// onEnter is called when the user presses Enter on an item.
	onEnter func(idx int)
	// onBack is called when the user presses Escape.
	onBack func()
}

// NewMenuWidget creates a MenuWidget with the given items and padding.
func NewMenuWidget(items []model.MenuItem, innerPad int) *MenuWidget {
	m := &MenuWidget{
		Box:      tview.NewBox(),
		items:    items,
		innerPad: innerPad,
	}
	m.Box.SetBackgroundColor(theme.ColorBackground)
	m.Box.SetBorderColor(theme.ColorBorder)
	m.Box.SetBorder(true)
	return m
}

// SetInnerPad updates the horizontal padding inside the border.
func (m *MenuWidget) SetInnerPad(pad int) {
	m.innerPad = pad
}

// SetItems replaces the current menu items.
func (m *MenuWidget) SetItems(items []model.MenuItem) {
	m.items = items
	if m.selectedIdx >= len(items) {
		m.selectedIdx = 0
	}
}

// SetSelectedIndex sets the highlighted row.
func (m *MenuWidget) SetSelectedIndex(idx int) {
	if idx >= 0 && idx < len(m.items) {
		m.selectedIdx = idx
	}
}

// SelectedIndex returns the current highlighted row index.
func (m *MenuWidget) SelectedIndex() int {
	return m.selectedIdx
}

// SetOnSelectionChanged registers a callback invoked on selection movement.
func (m *MenuWidget) SetOnSelectionChanged(fn func(int)) {
	m.onSelectionChanged = fn
}

// SetOnEnter registers a callback invoked when Enter is pressed.
func (m *MenuWidget) SetOnEnter(fn func(int)) {
	m.onEnter = fn
}

// SetOnBack registers a callback invoked when Escape is pressed.
func (m *MenuWidget) SetOnBack(fn func()) {
	m.onBack = fn
}

// Draw renders the menu widget.
// The border is drawn by tview.Box; we draw the items in the inner area.
func (m *MenuWidget) Draw(screen tcell.Screen) {
	// Draw the box border first.
	m.Box.Draw(screen)

	// Get the inner area (inside the border).
	x, y, w, h := m.Box.GetInnerRect()
	if w <= 0 || h <= 0 {
		return
	}

	// Render each item. Each item occupies exactly one row with one blank row
	// between items for visual breathing room, matching the Figma layout.
	// We use a 1-cell vertical inset inside the border (top and bottom).
	innerY := y + 1 // 1-cell top inset
	innerH := h - 2 // reserve 1-cell bottom inset
	_ = innerH

	for i, item := range m.items {
		row := innerY + i*2 // 2 rows per item: text + blank separator
		if row >= y+h-1 {
			break // do not overflow the border bottom
		}

		isSelected := i == m.selectedIdx

		var fg, bg tcell.Color
		var bold bool
		if isSelected {
			fg = theme.ColorSelectionFg
			bg = theme.ColorSelectionBg
			bold = false
		} else {
			fg = theme.ColorPrimary
			bg = theme.ColorBackground
			bold = false
		}

		style := tcell.StyleDefault.Background(bg).Foreground(fg)
		if bold {
			style = style.Bold(true)
		}

		// Build the label: ">" prefix for selected, "  " otherwise.
		prefix := "  "
		if isSelected {
			prefix = "> "
		}
		label := prefix + item.Label

		// Fill the entire row width with the selection background.
		// This gives the full-width highlight shown in the mockup.
		fillRow(screen, x, row, w, style)

		// Draw the label text (with left padding inside the border).
		textX := x + m.innerPad
		drawText(screen, textX, row, label, style)
	}
}

// InputHandler handles keyboard events for the menu widget.
func (m *MenuWidget) InputHandler() func(event *tcell.EventKey, setFocus func(p tview.Primitive)) {
	return m.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p tview.Primitive)) {
		switch event.Key() {
		case tcell.KeyUp:
			if m.selectedIdx > 0 {
				m.selectedIdx--
				if m.onSelectionChanged != nil {
					m.onSelectionChanged(m.selectedIdx)
				}
			}
		case tcell.KeyDown:
			if m.selectedIdx < len(m.items)-1 {
				m.selectedIdx++
				if m.onSelectionChanged != nil {
					m.onSelectionChanged(m.selectedIdx)
				}
			}
		case tcell.KeyHome:
			if m.selectedIdx != 0 {
				m.selectedIdx = 0
				if m.onSelectionChanged != nil {
					m.onSelectionChanged(m.selectedIdx)
				}
			}
		case tcell.KeyEnd:
			last := len(m.items) - 1
			if m.selectedIdx != last {
				m.selectedIdx = last
				if m.onSelectionChanged != nil {
					m.onSelectionChanged(m.selectedIdx)
				}
			}
		case tcell.KeyEnter:
			if m.onEnter != nil {
				m.onEnter(m.selectedIdx)
			}
		case tcell.KeyEscape:
			if m.onBack != nil {
				m.onBack()
			}
		}
	})
}

// HasFocus is required to satisfy tview.Primitive.
func (m *MenuWidget) HasFocus() bool {
	return m.Box.HasFocus()
}

// Focus is required to satisfy tview.Primitive.
func (m *MenuWidget) Focus(delegate func(p tview.Primitive)) {
	m.Box.Focus(delegate)
}

// fillRow paints an entire horizontal row with the given style.
func fillRow(screen tcell.Screen, x, y, width int, style tcell.Style) {
	for col := x; col < x+width; col++ {
		screen.SetContent(col, y, ' ', nil, style)
	}
}

// drawText writes a string starting at (x, y) using the given style.
func drawText(screen tcell.Screen, x, y int, text string, style tcell.Style) {
	for i, ch := range text {
		screen.SetContent(x+i, y, ch, nil, style)
	}
}