package objects

import "math"
import "image"
import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/tomo/input"
import "git.tebibyte.media/tomo/tomo/event"

var _ tomo.Object = new(Slider)

// Slider is a control that selects a numeric value between 0 and 1.
//
// Sub-components:
//   - SliderHandle is the grabbable handle of the slider.
//
// Tags:
//   - [vertical] The slider is oriented vertically.
//   - [horizontall] The slider is oriented horizontally.
//
// SliderHandle tags:
//   - [vertical] The handle is oriented vertically.
//   - [horizontall] The handle is oriented horizontally.
type Slider struct {
	box        tomo.ContainerBox
	handle     *sliderHandle
	layout     sliderLayout
	dragging   bool
	dragOffset image.Point
	step       float64

	on struct {
		valueChange event.FuncBroadcaster
		confirm     event.FuncBroadcaster
	}
}

type sliderHandle struct {
	tomo.Box
}

func newSlider (orient string, value float64) *Slider {
	slider := &Slider {
		box: tomo.NewContainerBox(),
		handle: &sliderHandle {
			Box: tomo.NewBox(),
		},
		layout: sliderLayout {
			vertical: orient == "vertical",
			value:    math.NaN(),
		},
		step: 0.05,
	}

	slider.handle.SetRole(tomo.R("objects", "SliderHandle"))
	slider.handle.SetTag(orient, true)
	slider.box.SetRole(tomo.R("objects", "Slider"))
	slider.box.SetTag(orient, true)
	
	slider.box.Add(slider.handle)
	slider.box.SetFocusable(true)
	slider.SetValue(value)

	slider.box.SetInputMask(true)
	slider.box.OnKeyUp(slider.handleKeyUp)
	slider.box.OnKeyDown(slider.handleKeyDown)
	slider.box.OnButtonDown(slider.handleButtonDown)
	slider.box.OnButtonUp(slider.handleButtonUp)
	slider.box.OnMouseMove(slider.handleMouseMove)
	slider.box.OnScroll(slider.handleScroll)
	return slider
}

// NewVerticalSlider creates a new vertical slider with the specified value.
func NewVerticalSlider (value float64) *Slider {
	return newSlider("vertical", value)
}

// NewHorizontalSlider creates a new horizontal slider with the specified value.
func NewHorizontalSlider (value float64) *Slider {
	return newSlider("horizontal", value)
}

// GetBox returns the underlying box.
func (this *Slider) GetBox () tomo.Box {
	return this.box
}

// SetFocused sets whether or not this slider has keyboard focus. If set to
// true, this method will steal focus away from whichever object currently has
// focus.
func (this *Slider) SetFocused (focused bool) {
	this.box.SetFocused(focused)
}

// SetValue sets the value of the slider between 0 and 1.
func (this *Slider) SetValue (value float64) {
	if value < 0 { value = 0 }
	if value > 1 { value = 1 }
	if value == this.layout.value { return }
	this.layout.value = value
	this.box.SetAttr(tomo.ALayout(this.layout))
}

// Value returns the value of the slider between 0 and 1.
func (this *Slider) Value () float64 {
	return this.layout.value
}

// OnValueChange specifies a function to be called when the user moves the
// slider.
func (this *Slider) OnValueChange (callback func ()) event.Cookie {
	return this.on.valueChange.Connect(callback)
}

// OnConfirm specifies a function to be called when the user stops moving the
// slider.
func (this *Slider) OnConfirm (callback func ()) event.Cookie {
	return this.on.confirm.Connect(callback)
}

func (this *Slider) handleKeyDown (key input.Key, numpad bool) bool {
	var increment float64; if this.layout.vertical {
		increment = -0.05
	} else {
		increment = 0.05
	}

	switch key {
	case input.KeyUp, input.KeyLeft:
		if this.box.Window().Modifiers().Alt {
			this.SetValue(0)
		} else {
			this.SetValue(this.Value() - increment)
		}
		this.on.valueChange.Broadcast()
		return true
	case input.KeyDown, input.KeyRight:
		if this.box.Window().Modifiers().Alt {
			this.SetValue(1)
		} else {
			this.SetValue(this.Value() + increment)
		}
		this.on.valueChange.Broadcast()
		return true
	case input.KeyHome:
		this.SetValue(0)
		this.on.valueChange.Broadcast()
		return true
	case input.KeyEnd:
		this.SetValue(1)
		this.on.valueChange.Broadcast()
		return true
	}
	return false
}

func (this *Slider) handleKeyUp (key input.Key, numpad bool) bool {
	switch key {
	case input.KeyUp,   input.KeyLeft:  return true
	case input.KeyDown, input.KeyRight: return true
	case input.KeyHome: return true
	case input.KeyEnd:  return true
	}
	return false
}

func (this *Slider) handleButtonDown (button input.Button) bool {
	pointer := this.box.Window().MousePosition()
	handle  := this.handle.Bounds()
	
	within := pointer.In(handle)
	var above bool; if this.layout.vertical {
		above = pointer.Y < handle.Min.Y + handle.Dy() / 2
	} else {
		above = pointer.X < handle.Min.X + handle.Dx() / 2
	}

	switch button {
	case input.ButtonLeft:
		if within {
			this.dragging   = true
			this.dragOffset =
				pointer.Sub(this.handle.Bounds().Min).
				Add(this.box.InnerBounds().Min)
			this.drag()
		} else {
			this.dragOffset = this.fallbackDragOffset()
			this.dragging   = true
			this.drag()
		}
	case input.ButtonMiddle:
		if above {
			this.SetValue(0)
			this.on.valueChange.Broadcast()
			this.on.confirm.Broadcast()
		} else {
			this.SetValue(1)
			this.on.valueChange.Broadcast()
			this.on.confirm.Broadcast()
		}
	case input.ButtonRight:
		if above {
			this.SetValue(this.Value() - this.step)
			this.on.valueChange.Broadcast()
			this.on.confirm.Broadcast()
		} else {
			this.SetValue(this.Value() + this.step)
			this.on.valueChange.Broadcast()
			this.on.confirm.Broadcast()
		}
	}
	return true
}

func (this *Slider) handleButtonUp (button input.Button) bool {
	if button != input.ButtonLeft || !this.dragging { return true }
	this.dragging = false
	this.on.confirm.Broadcast()
	return true
}

func (this *Slider) handleMouseMove () bool {
	if !this.dragging { return false }
	this.drag()
	return true
}

func (this *Slider) handleScroll (x, y float64) bool {
	delta := (x + y) * 0.005
	this.SetValue(this.Value() + delta)
	this.on.valueChange.Broadcast()
	this.on.confirm.Broadcast()
	return true
}

func (this *Slider) drag () {
	pointer := this.box.Window().MousePosition().Sub(this.dragOffset)
	gutter  := this.box.InnerBounds()
	handle  := this.handle.Bounds()

	if this.layout.vertical {
		this.SetValue (
			1 -
			float64(pointer.Y) /
			float64(gutter.Dy() - handle.Dy()))
	} else {
		this.SetValue (
			float64(pointer.X) /
			float64(gutter.Dx() - handle.Dx()))
	}
	this.on.valueChange.Broadcast()
}

func (this *Slider) fallbackDragOffset () image.Point {
	if this.layout.vertical {
		return this.box.InnerBounds().Min.
			Add(image.Pt(0, this.handle.Bounds().Dy() / 2))
	} else {
		return this.box.InnerBounds().Min.
			Add(image.Pt(this.handle.Bounds().Dx() / 2, 0))
	}
}

type sliderLayout struct {
	vertical bool
	value    float64
}

func (sliderLayout) MinimumSize (hints tomo.LayoutHints, boxes tomo.BoxQuerier) image.Point {
	if boxes.Len() != 1 { return image.Pt(0, 0) }
	return boxes.MinimumSize(0)
}

func (this sliderLayout) Arrange (hints tomo.LayoutHints, boxes tomo.BoxArranger) {
	if boxes.Len() != 1 { return }
	handle := image.Rectangle { Max: boxes.MinimumSize(0) }
	gutter := hints.Bounds

	if this.vertical {
		height := gutter.Dy() - handle.Dy()
		offset := int(float64(height) * (1 - this.value))
		handle.Max.X = gutter.Dx()
		boxes.SetBounds (
			0,
			handle.Add(image.Pt(0, offset)).Add(gutter.Min))
	} else {
		width  := gutter.Dx() - handle.Dx()
		offset := int(float64(width) * this.value)
		handle.Max.Y = gutter.Dy()
		boxes.SetBounds (
			0,
			handle.Add(image.Pt(offset, 0)).Add(gutter.Min))
	}
}

func (this sliderLayout) RecommendedHeight (hints tomo.LayoutHints, boxes tomo.BoxQuerier, width int) int {
	return this.MinimumSize(hints, boxes).X
}

func (this sliderLayout) RecommendedWidth (hints tomo.LayoutHints, boxes tomo.BoxQuerier, height int) int {
	return this.MinimumSize(hints, boxes).Y
}