package ui

import (
	"log"

	"github.com/hajimehoshi/ebiten/v2"
	"github.com/hajimehoshi/ebiten/v2/inpututil"
	"golang.org/x/exp/slices"
)

// Container to organise multiple Widgets
// A collection does implement the Widget interface and thus can be nested in
// another Collection.
type Collection struct {
	Width, Height int
	hoverDetector hoverDetector
	widgets       []Widget
	focused       Widget
}

func (c *Collection) Layout() (int, int) {
	return c.Width, c.Height
}

func (c *Collection) Widgets() []Widget {
	return c.widgets
}

func (c *Collection) Clear() {
	c.widgets = []Widget{}
}

func (c *Collection) ResetHover() {
	c.hoverDetector.reset(0, 0)
}

func (c *Collection) AddWidget(w Widget) {
	if w == nil {
		log.Panicf("Adding nil widget to collection")
	}
	if slices.Contains(c.widgets, w) {
		log.Panicf("Double insertion of %v", w)
	}
	c.widgets = append(c.widgets, w)
}

func (c *Collection) FindWidget(toFind Widget) int {
	for i, w := range c.widgets {
		if w != toFind {
			continue
		}
		return i
	}
	return -1
}

func (c *Collection) RemoveWidget(widget Widget) {
	idx := c.FindWidget(widget)
	if idx != -1 {
		c.RemoveWidgetAt(idx)
	}
}

func (c *Collection) RemoveWidgetAt(idx int) {
	nwidgets := len(c.widgets)
	c.widgets[idx] = c.widgets[nwidgets-1]
	c.widgets = c.widgets[:nwidgets-1]
}

func (c *Collection) Draw(screen *ebiten.Image) {
	for _, w := range c.widgets {
		w.Draw(screen)
	}
}

func (c *Collection) Contains(x, y int) bool {
	for _, w := range c.widgets {
		if w.Contains(x, y) {
			return true
		}
	}
	return false
}

func (c *Collection) FindWidgetAt(x, y int) Widget {

	// Iterate the widget in reverse order to ensure that upper widgets are
	// considered first
	for i := len(c.widgets) - 1; i >= 0; i-- {
		w := c.widgets[i]
		if !w.Contains(x, y) {
			continue
		}
		return w
	}
	return nil
}

func (c *Collection) FindObjectAt(x, y int) interface{} {

	// Iterate the widget in reverse order to ensure that upper widgets are
	// considered first
	for i := len(c.widgets) - 1; i >= 0; i-- {
		w := c.widgets[i]
		if o := w.FindObjectAt(x, y); o != nil {
			return o
		}
	}

	return nil
}

func (c *Collection) switchFocus(fcsbl Widget) {
	log.Printf("switch focus from %v to %v\n", c.focused, fcsbl)
	if c.focused != nil {
		c.focused.Focus(false)

	}
	if fcsbl != nil {
		fcsbl.Focus(true)
		c.focused = fcsbl
	} else {
		c.focused = nil
	}
}

func (c *Collection) handleTouchInputs() error {
	for _, tap := range TouchManager.Taps {
		for i := len(c.widgets) - 1; i >= 0; i-- {
			w := c.widgets[i]
			if !w.Contains(tap.X, tap.Y) {
				continue
			}
			if w.IsClickable() {
				w.Click(tap.X, tap.Y)
			}
			if w.IsFocusable() {
				c.switchFocus(w)
			} else if c.focused != nil {
				c.switchFocus(nil)
			}
			break
		}
	}

	// TODO: handle pinching
	if TouchManager.Pan != nil {
		pan := TouchManager.Pan
		iX, iY := pan.Incremental()

		w := c.FindWidgetAt(int(pan.originX), (pan.originY))
		if w != nil && w.IsScrollable() {
			w.Scroll(int(iX)/10, int(iY)/10)
		}
	}

	return nil
}

func passInput(textInput *TextInput) {
	var input []rune
	input = ebiten.AppendInputChars(input)
	if len(input) > 0 {
		textInput.AddInput(input)
	}
	textInput.HandleKey()
}

func (c *Collection) IsUpdatable() bool {
	return true
}

func (c *Collection) Update() error {
	// Update all updatables
	for _, w := range c.widgets {
		if w.IsUpdatable() {
			if err := w.Update(); err != nil {
				return err
			}
		}
	}

	if err := c.handleTouchInputs(); err != nil {
		return err
	}

	x, y := ebiten.CursorPosition()

	activeWidget := c.FindWidgetAt(x, y)

	c.hoverDetector.update(c, x, y, activeWidget)

	if activeWidget == nil {
		if txt, ok := c.focused.(*TextInput); ok {
			if ebiten.IsKeyPressed(ebiten.KeyA) {
				txt.AddInput([]rune{'a'})
			}
			passInput(txt)
		}
		return nil
	}

	scrollX, scrollY := ebiten.Wheel()
	if scrollX != 0 || scrollY != 0 {
		if activeWidget.IsScrollable() {
			activeWidget.Scroll(int(scrollX), int(scrollY))
		}
	}

	if textInput, ok := activeWidget.(*TextInput); ok {
		passInput(textInput)
	}

	if inpututil.IsMouseButtonJustPressed(ebiten.MouseButtonLeft) {
		if activeWidget.IsClickable() {
			activeWidget.Click(x, y)
		}
	}

	return nil
}

// The events for the contained widgets
// are emitted during the collections
// Update method.
func (c *Collection) IsClickable() bool {
	return false
}
func (c *Collection) Click(int, int) {}

func (c *Collection) IsScrollable() bool {
	return false
}
func (c *Collection) Scroll(int, int) {}

func (c *Collection) IsFocusable() bool {
	return false
}
func (c *Collection) Focus(bool) {}