package giowrap

import (
	"image/color"
	"log"

	"gioui.org/ui"
	"gioui.org/ui/app"
	"gioui.org/ui/input"
	"gioui.org/ui/layout"
	"gioui.org/ui/measure"
	"gioui.org/ui/text"

	"gioui.org/ui/f32"
	gdraw "gioui.org/ui/draw"
	"gioui.org/ui/gesture"
	"gioui.org/ui/pointer"
)

type Context struct {
	Faces measure.Faces

	w *app.Window
	c *app.Config
	q input.Queue
	ops *ui.Ops
	cs layout.Constraints
	dims layout.Dimens
	extra map[string]interface{}
}

func NewContext(w *app.Window) Context {
	return Context{
		w: w,
		ops: new(ui.Ops),
		q: w.Queue(),
		extra: make(map[string]interface{}),
	}
}

func (ctx Context) Reset(e app.DrawEvent) Context {
	ctx.c = &e.Config
	ctx.ops.Reset()
	ctx.cs = layout.RigidConstraints(e.Size)
	ctx.Faces.Reset(ctx.c)
	return ctx
}

func (ctx Context) Draw() {
	ctx.w.Draw(ctx.ops)
}

type Layout func(Context) Context

type Widget interface {
	Layout(Context) Context
}

type WidgetCombinator func(...Widget) Widget

type Label struct {
	l *text.Label
}

func NewLabel(face text.Face, t string, alignment text.Alignment) *Label {
	ret := &Label{}
	ret.l = &text.Label{
		Face: face,
		Text: t,
		Alignment: alignment,
	}
	return ret
}

func (l *Label) Layout(ctx Context) Context {
	ctx.dims = l.l.Layout(ctx.ops, ctx.cs)
	return ctx
}

type Editor struct {
	e *text.Editor
}

func NewEditor(face text.Face, singleline bool) *Editor {
	ret := &Editor{}
	ret.e = &text.Editor{ Face: face, SingleLine: singleline }
	return ret
}

func (e *Editor) Layout(ctx Context) Context {
	ctx.dims = e.e.Layout(ctx.c, ctx.q, ctx.ops, ctx.cs)
	return ctx
}

func (e *Editor) Text() string { return e.e.Text() }
func (e *Editor) SetText(s string) { e.e.SetText(s) }
func (e *Editor) Focus() { e.e.Focus() }

type fWidget struct {
	l Layout
}

func NewfWidget(l Layout) fWidget {
	return fWidget{ l: l }
}

func (fw fWidget) Layout(ctx Context) Context {
	return fw.l(ctx)
}

type Flex WidgetCombinator

// This "Widget" does nothing except set the Flexible key of ctx.extra.
func Flexible(v float32) Widget {
	return NewfWidget(func(ctx Context) Context {
		ctx.extra["Flexible"] = v
		return ctx
	})
}

// NewFlex returns a WidgetCombinator that wraps the layout.Flex element.
func NewFlex(axis layout.Axis, mainAxisAlignment layout.MainAxisAlignment, crossAxisAlignment layout.CrossAxisAlignment) Flex {
	f := layout.Flex{
		Axis: axis,
		MainAxisAlignment: mainAxisAlignment,
		CrossAxisAlignment: crossAxisAlignment,
	}
	return func(ws ...Widget) Widget {
		return NewfWidget(func(ctx Context) Context {
			f.Init(ctx.ops, ctx.cs)
			fcs := make([]layout.FlexChild,len(ws))
			for i, w := range ws {
				if v,ok := ctx.extra["Flexible"]; ok {
					switch v := v.(type) {
					case float32:
						ctx.cs = f.Flexible(v)
					default:
						log.Fatal("Type error")
					}
				} else {
					ctx.cs = f.Rigid()
				}
				ctx = w.Layout(ctx)
				fcs[i] = f.End(ctx.dims)
			}
			ctx.dims = f.Layout(fcs...)
			delete(ctx.extra, "Flexible")
			return ctx
		})
	}
}

//NewInset returns a WidgetCombinator that wraps the layout.Inset element.
func NewInset(top, right, bottom, left ui.Value) WidgetCombinator {
	ins := layout.Inset{ Top: top, Right: right, Bottom: bottom, Left: left }
	return func(ws ...Widget) Widget {
		return NewfWidget(func(ctx Context) Context {
			ctx.cs = ins.Begin(ctx.c, ctx.ops, ctx.cs)
			var dims layout.Dimens
			for _, w := range ws {
				ctx = w.Layout(ctx)
			}
			ctx.dims = ins.End(dims)
			return ctx
		})
	}
}

type Background struct {
	Color color.RGBA
	Radius ui.Value
	Inset layout.Inset

	macro ui.MacroOp
}

type Enclosure interface {
	Begin(Context) Context
	End(Context) Context
}

func Enclose(e Enclosure, ws ...Widget) Widget {
	return NewfWidget(func(ctx Context) Context {
		ctx = e.Begin(ctx)
		for _,w := range ws {
			ctx = w.Layout(ctx)
		}
		ctx = e.End(ctx)
		return ctx
	})
}

func NewBackground(color color.RGBA, radius ui.Value) WidgetCombinator {
	bg := &Background{
		Color: color,
		Radius: radius,
		Inset: layout.UniformInset(radius), 	// FIXME: need to be able to
	}						// do math ops on Values
	return func(ws ...Widget) Widget {
		return Enclose(bg, ws...)
	}
}

func (bg *Background) Begin(ctx Context) Context {
	bg.macro.Record(ctx.ops)
	ctx.cs = bg.Inset.Begin(ctx.c, ctx.ops, ctx.cs)
	return ctx
}

func (bg *Background) End(ctx Context) Context {
	ctx.dims = bg.Inset.End(ctx.dims)
	bg.macro.Stop()
	//var stack ui.StackOp
	w, h := float32(ctx.dims.Size.X), float32(ctx.dims.Size.Y)
	if r := float32(ctx.c.Px(bg.Radius)); r > 0 {
		if r > w / 2 {
			r = w / 2
		}
		if r > h / 2 {
			r = h / 2
		}
		rrect(ctx.ops, w, h, r, r, r, r)
	}
	gdraw.ColorOp{Color: bg.Color}.Add(ctx.ops)
	gdraw.DrawOp{Rect: f32.Rectangle{Max: f32.Point{X: w, Y: h}}}.Add(ctx.ops)
	bg.macro.Add(ctx.ops)
	return ctx
}

// 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 gdraw.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()
}

//cWidget is a clickable Widget that provides the Clicked() method.
type cWidget struct {
	w Widget
	click *gesture.Click
}

func (w cWidget) Layout(ctx Context) Context {
	ctx = w.w.Layout(ctx)
	pointer.RectAreaOp{Size: ctx.dims.Size}.Add(ctx.ops)
	w.click.Add(ctx.ops)
	return ctx
}

func (w cWidget) Clicked(ctx Context) bool {
	for _,e := range w.click.Events(ctx.q) {
		if e.Type == gesture.TypeClick {
			return true
		}
	}
	return false
}

//Clickable converts any Widget into a clickable Widget.
func Clickable(w Widget) cWidget {
	return cWidget{ w: w, click: new(gesture.Click) }
}