package ui

import (
	"fmt"
	"image"

	"code.ur.gs/lupine/ordoor/internal/assetstore"
	"code.ur.gs/lupine/ordoor/internal/menus"
)

func init() {
	registerBuilder(menus.TypeLineKbd, ownedByMenu)
	registerBuilder(menus.TypeLineBriefing, ownedByMenu)

	registerBuilder(menus.TypeThumb, ownedByMenu)
	registerBuilder(menus.TypeListBoxUp, ownedByMenu)
	registerBuilder(menus.TypeListBoxDown, ownedByMenu)
}

// listBox is a TListBox in VCL terms. It has a number of lines of text, one of
// which may be selected, and a slider with up and down buttons to scroll if the
// options in the box exceed its viewing capacity.
//
// TODO: multi-select functionality? Is it needed?
type listBox struct {
	upBtn   *button
	downBtn *button

	// FIXME: can we share code between slider and this element?
	thumbBase *assetstore.Sprite // Bounds are given by this
	thumbImg  *assetstore.Sprite // This is displayed at offset * (height / steps)

	base  *noninteractive   // The menu itself has a sprite to display
	lines []*noninteractive // We display to these

	// The list box acts as a window onto these
	strings []string

	// The start of our window
	offset int
}

func registerListBox(d *Driver, menu *menus.Record) ([]*menus.Record, error) {
	var upBtn *menus.Record
	var downBtn *menus.Record
	var thumb *menus.Record
	var items []*menus.Record
	var otherChildren []*menus.Record

	for _, rec := range menu.Children {
		switch rec.Type {
		case menus.TypeListBoxUp:
			if upBtn != nil {
				return nil, fmt.Errorf("Duplicate up buttons in menu %v", menu.Locator())
			}
			upBtn = rec
		case menus.TypeListBoxDown:
			if downBtn != nil {
				return nil, fmt.Errorf("Duplicate down buttons in menu %v", menu.Locator())
			}
			downBtn = rec
		case menus.TypeLineKbd, menus.TypeLineBriefing:
			items = append(items, rec)
		case menus.TypeThumb:
			if thumb != nil {
				return nil, fmt.Errorf("Duplicate thumbs in menu %v", menu.Locator())
			}
			thumb = rec
		default:
			// e.g. maingame:18.12 includes a button that is not part of the box
			otherChildren = append(otherChildren, rec)
		}
	}

	if len(items) == 0 || thumb == nil || upBtn == nil || downBtn == nil {
		return nil, fmt.Errorf("Missing items in menu %v", menu.Locator())
	}

	// Now build the wonderful thing
	baseElem, err := registerNoninteractive(d, menu)
	if err != nil {
		return nil, err
	}

	upSprId := upBtn.SpriteId[0]
	if upSprId == -1 {
		upSprId = upBtn.Share
	}

	elemUp, err := registerButton(d, upBtn, upSprId)
	if err != nil {
		return nil, err
	}

	dnSprId := downBtn.SpriteId[0]
	if dnSprId == -1 {
		dnSprId = downBtn.Share
	}
	elemDown, err := registerButton(d, downBtn, dnSprId)
	if err != nil {
		return nil, err
	}

	thumbBaseSpr, err := d.menu.Sprite(menu.ObjectIdx, thumb.Share)
	if err != nil {
		return nil, err
	}

	thumbSprId := thumb.SpriteId[0]
	if thumbSprId == -1 {
		thumbSprId = thumb.Share
	}

	thumbImgSpr, err := d.menu.Sprite(menu.ObjectIdx, thumbSprId)
	if err != nil {
		return nil, err
	}

	element := &listBox{
		base: baseElem,
		// TODO: upBtn needs to be frozen when offset == 0; downBtn when offset == max
		upBtn:   elemUp,
		downBtn: elemDown,

		// TODO: need to be able to drag the thumb
		thumbBase: thumbBaseSpr,
		thumbImg:  thumbImgSpr,
	}

	// Internal wiring-up
	elemUp.onClick(element.up)
	elemDown.onClick(element.down)

	// FIXME: Test data for now
	for i := 0; i < 50; i++ {
		element.strings = append(element.strings, fmt.Sprintf("FOO %v", i))
	}

	// Register everything. Since we're a composite of other controls, they are
	// mostly self-registered at the moment.
	d.paintables = append(d.paintables, element)

	// FIXME: we should be able to freeze/unfreeze as a group.

	// HURK: These need to be registered after the other elements so they are
	// drawn in the correct order to be visible
	for _, rec := range items {
		ni, err := registerNoninteractive(d, rec)
		if err != nil {
			return nil, err
		}
		// TODO: pick the correct font
		ni.label = &label{
			align: AlignModeLeft,
			font:  d.menu.Font(0),
			rect:  ni.rect,
		}

		element.lines = append(element.lines, ni)
	}

	element.refresh()

	return otherChildren, nil
}

func (l *listBox) SetStrings(to []string) {
	if len(to) < len(l.strings) {
		l.offset = 0 // FIXME: unconditional? Trim to max?
	}

	l.strings = to

	l.refresh()
}

// TODO: Selected returns the index and value of the selected item
func (l *listBox) Selected() (int, string) {
	return 0, ""
}

func (l *listBox) up() {
	if l.offset <= 0 {
		return
	}

	l.offset -= 1
	l.refresh()
}

func (l *listBox) down() {
	if l.offset > len(l.strings)-len(l.lines) {
		return
	}

	l.offset += 1
	l.refresh()
}

func (l *listBox) refresh() {
	for i, ni := range l.lines {
		// FIXME: noninteractive isn't set up for dynamic text yet. Need to
		// generate textImg on demand instead of once at start.
		if ni.label != nil {
			ni.label.text = ""
			if len(l.strings) > l.offset+i {
				ni.label.text = l.strings[l.offset+i]
			}
		}
	}
}

func (l *listBox) thumbPos() image.Point {
	pos := l.thumbImg.Rect.Min
	if len(l.strings) == 0 {
		return pos
	}

	pixPerLine := (l.thumbBase.Rect.Dy()) / (len(l.strings) - len(l.lines))
	pos.Y += pixPerLine * l.offset

	return pos
}

func (l *listBox) regions(tick int) []region {
	// Draw the slider at the appropriate point
	out := oneRegion(l.thumbBase.Rect.Min, l.thumbBase.Image)
	out = append(out, oneRegion(l.thumbPos(), l.thumbImg.Image)...)

	return out
}