package ui

import "gioui.org/unit"

// Region defines a screen area in device-independent pixels (Dp).
type Region struct {
	X, Y unit.Dp
	W, H unit.Dp
}

// Element is the base interface for all UI elements.
type Element interface {
	Region() Region
	Visible() bool
}

// TextAlign specifies horizontal text alignment.
type TextAlign int

const (
	AlignStart TextAlign = iota
	AlignCenter
	AlignEnd
)

// Label displays static text.
type Label struct {
	id      string
	region  Region
	visible bool
	Text    string
	Align   TextAlign
	FontSize unit.Sp // 0 = theme default
	Color   Color    // 0 = theme default
	Bold    bool
}

func (l Label) Region() Region { return l.region }
func (l Label) Visible() bool  { return l.visible }
func (l Label) ID() string     { return l.id }

// TextField accepts text input or displays multiline text.
type TextField struct {
	id           string
	region       Region
	visible      bool
	Value        string
	Placeholder  string
	Focused      bool
	Multiline    bool
	ScrollOffset unit.Dp
}

func (tf TextField) Region() Region { return tf.region }
func (tf TextField) Visible() bool  { return tf.visible }
func (tf TextField) ID() string     { return tf.id }

// ListView displays a scrollable list of items.
type ListView struct {
	id           string
	region       Region
	visible      bool
	Items        []ListItem
	ScrollOffset int
	Selected     int
}

func (lv ListView) Region() Region { return lv.region }
func (lv ListView) Visible() bool  { return lv.visible }
func (lv ListView) ID() string     { return lv.id }

// ListItem is a single entry in a ListView.
type ListItem struct {
	Text     string
	Subtext  string
	Selected bool
}

// Color is an RGBA color.
type Color struct {
	R, G, B, A uint8
}

// Theme holds styling defaults for the UI.
type Theme struct {
	FontSize unit.Sp
}

// NewLabel creates a visible Label element.
func NewLabel(text string, fontSize unit.Sp, region Region) Label {
	return Label{
		region:   region,
		visible:  true,
		Text:     text,
		FontSize: fontSize,
	}
}

// NewListView creates a visible ListView element.
func NewListView(region Region, items []ListItem) ListView {
	return ListView{
		region:  region,
		visible: true,
		Items:   items,
	}
}