// SPDX-License-Identifier: Unlicense OR MIT

package material

import (
	"image"
	"image/color"

	"gioui.org/f32"
	"gioui.org/internal/f32color"
	"gioui.org/layout"
	"gioui.org/op/clip"
	"gioui.org/op/paint"
	"gioui.org/unit"
)

type ProgressBarStyle struct {
	Color      color.NRGBA
	TrackColor color.NRGBA
	Progress   float32
}

func ProgressBar(th *Theme, progress float32) ProgressBarStyle {
	return ProgressBarStyle{
		Progress:   progress,
		Color:      th.Palette.ContrastBg,
		TrackColor: f32color.MulAlpha(th.Palette.Fg, 0x88),
	}
}

func (p ProgressBarStyle) Layout(gtx layout.Context) layout.Dimensions {
	shader := func(width float32, color color.NRGBA) layout.Dimensions {
		maxHeight := unit.Dp(4)
		rr := float32(gtx.Px(unit.Dp(2)))

		d := image.Point{X: int(width), Y: gtx.Px(maxHeight)}

		height := float32(gtx.Px(maxHeight))
		clip.UniformRRect(f32.Rectangle{Max: f32.Pt(width, height)}, rr).Add(gtx.Ops)
		paint.ColorOp{Color: color}.Add(gtx.Ops)
		paint.PaintOp{}.Add(gtx.Ops)

		return layout.Dimensions{Size: d}
	}

	progressBarWidth := float32(gtx.Constraints.Max.X)
	return layout.Stack{Alignment: layout.W}.Layout(gtx,
		layout.Stacked(func(gtx layout.Context) layout.Dimensions {
			return shader(progressBarWidth, p.TrackColor)
		}),
		layout.Stacked(func(gtx layout.Context) layout.Dimensions {
			fillWidth := progressBarWidth * clamp1(p.Progress)
			fillColor := p.Color
			if gtx.Queue == nil {
				fillColor = f32color.Disabled(fillColor)
			}
			return shader(fillWidth, fillColor)
		}),
	)
}

// clamp1 limits v to range [0..1].
func clamp1(v float32) float32 {
	if v >= 1 {
		return 1
	} else if v <= 0 {
		return 0
	} else {
		return v
	}
}