package main

import (
	"image"
	"image/color"

	"gioui.org/ui"
	"gioui.org/ui/f32"
	"gioui.org/ui/gesture"
	"gioui.org/ui/input"
	"gioui.org/ui/layout"
	"gioui.org/ui/paint"
	"gioui.org/ui/pointer"
	"gioui.org/ui/text"
)

var (
	black    = color.RGBA{A: 0xff, R: 0, G: 0, B: 0}
	white    = color.RGBA{A: 0xff, R: 0xff, G: 0xff, B: 0xff}
	gray     = color.RGBA{A: 0xff, R: 0xf0, G: 0xf0, B: 0xf0}
	darkgray = color.RGBA{A: 0xff, R: 0xa0, G: 0xa0, B: 0xa0}
)

type Overlay struct {
	Face       text.Face
	Text       string
	Click      gesture.Click
	Color      color.RGBA
	Background color.RGBA
	Alignment  text.Alignment
}

func (b *Overlay) Layout(c ui.Config, ops *ui.Ops, cs layout.Constraints) layout.Dimensions {
	ins := layout.UniformInset(ui.Dp(1))
	cs = ins.Begin(c, ops, cs)
	var dims layout.Dimensions
	st := layout.Stack{}
	st.Init(ops, cs)
	{
		cs = st.Rigid()
		l := text.Label{
			Face:      b.Face,
			Text:      b.Text,
			Alignment: b.Alignment,
		}
		ins := layout.UniformInset(ui.Dp(4))
		l.Material.Record(ops)
		paint.ColorOp{Color: b.Color}.Add(ops)
		l.Material.Stop()
		dims = ins.End(l.Layout(ops, ins.Begin(c, ops, cs)))
		pointer.RectAreaOp{image.Rect(0, 0, dims.Size.X, dims.Size.Y)}.Add(ops)
	}
	c2 := st.End(dims)
	c1 := st.End(layoutRRect(b.Background, c, ops, st.Expand()))
	dims = st.Layout(c1, c2)
	return ins.End(dims)
}

type Button struct {
	Face       text.Face
	Label      string
	Click      gesture.Click
	Color      color.RGBA
	Background color.RGBA
	Alignment  text.Alignment
	clicked    bool
}

func layoutRRect(col color.RGBA, c ui.Config, ops *ui.Ops, cs layout.Constraints) layout.Dimensions {
	r := float32(c.Px(ui.Dp(4)))
	sz := image.Point{X: cs.Width.Min, Y: cs.Height.Min}
	w, h := float32(sz.X), float32(sz.Y)
	rrect(ops, w, h, r, r, r, r)
	paint.ColorOp{Color: col}.Add(ops)
	paint.PaintOp{Rect: f32.Rectangle{Max: f32.Point{X: w, Y: h}}}.Add(ops)
	return layout.Dimensions{Size: sz}
}

// https://pomax.github.io/bezierinfo/#circles_cubic.
func rrect(ops *ui.Ops, width, height, se, sw, nw, ne float32) {
	w, h := float32(width), float32(height)
	const c = 0.55228475 // 4*(sqrt(2)-1)/3
	var b paint.PathBuilder
	b.Init(ops)
	b.Move(f32.Point{X: w, Y: h - se})
	b.Cube(f32.Point{X: 0, Y: se * c}, f32.Point{X: -se + se*c, Y: se}, f32.Point{X: -se, Y: se}) // SE
	b.Line(f32.Point{X: sw - w + se, Y: 0})
	b.Cube(f32.Point{X: -sw * c, Y: 0}, f32.Point{X: -sw, Y: -sw + sw*c}, f32.Point{X: -sw, Y: -sw}) // SW
	b.Line(f32.Point{X: 0, Y: nw - h + sw})
	b.Cube(f32.Point{X: 0, Y: -nw * c}, f32.Point{X: nw - nw*c, Y: -nw}, f32.Point{X: nw, Y: -nw}) // NW
	b.Line(f32.Point{X: w - ne - nw, Y: 0})
	b.Cube(f32.Point{X: ne * c, Y: 0}, f32.Point{X: ne, Y: ne - ne*c}, f32.Point{X: ne, Y: ne}) // NE
	b.End()
}

func (b *Button) Layout(c ui.Config, q input.Queue, ops *ui.Ops, cs layout.Constraints) layout.Dimensions {
	b.clicked = false
	for ev, ok := b.Click.Next(q); ok; ev, ok = b.Click.Next(q) {
		if ev.Type == gesture.TypeClick {
			b.clicked = true
		}
	}
	ins := layout.UniformInset(ui.Dp(1))
	cs = ins.Begin(c, ops, cs)
	var dims layout.Dimensions
	st := layout.Stack{}
	st.Init(ops, cs)
	{
		cs = st.Rigid()
		l := text.Label{
			Face:      b.Face,
			Text:      b.Label,
			Alignment: b.Alignment,
		}
		ins := layout.UniformInset(ui.Dp(4))
		paint.ColorOp{Color: b.Color}.Add(ops)
		dims = ins.End(l.Layout(ops, ins.Begin(c, ops, cs)))
		pointer.RectAreaOp{image.Rect(0, 0, dims.Size.X, dims.Size.Y)}.Add(ops)
		b.Click.Add(ops)
	}
	c2 := st.End(dims)
	c1 := st.End(layoutRRect(b.Background, c, ops, st.Expand()))
	dims = st.Layout(c1, c2)
	return ins.End(dims)
}

func (b *Button) Clicked() bool {
	return b.clicked
}