package ui

import (
	"image/color"
	"iter"

	"github.com/hajimehoshi/ebiten/v2"
	"github.com/hajimehoshi/ebiten/v2/text/v2"

	"muhq.space/muhqs-game/go/font"
)

var (
	BUFFER_BACKGROUND = Gray
	BUFFER_FOREGROUND = color.White
)

type Buffer struct {
	WidgetBase
	lines       []string
	pos         int
	font        *text.GoTextFace
	lineSpacing float64
	xMargin     float64
	bg          color.Color
	fg          color.Color
}

func NewBuffer(x, y int, width, height int) *Buffer {
	b := &Buffer{
		NewWidgetBase(x, y, width, height),
		[]string{},
		0,
		font.Font18,
		1.5,
		10.,
		BUFFER_BACKGROUND,
		BUFFER_FOREGROUND,
	}
	b.renderImpl = func() *ebiten.Image { return b.render() }
	return b
}

func (b *Buffer) render() *ebiten.Image {
	img := ebiten.NewImage(b.Width, b.Height)
	img.Fill(b.bg)
	var y float64 = -b.font.Size
	for _, line := range b.lines[b.pos:] {
		_, h := text.Measure(line, b.font, b.font.Size*b.lineSpacing)
		y += h
		if y > float64(b.Height) {
			break
		}
		op := &text.DrawOptions{}
		op.ColorScale.ScaleWithColor(b.fg)
		op.GeoM.Translate(b.xMargin, float64(y))
		op.LineSpacing = b.font.Size * b.lineSpacing
		text.Draw(img, line, b.font, op)
	}
	return img
}

func (b *Buffer) AddLines(lines []string) {
	b.lines = append(b.lines, lines...)
	b.ForceRedraw()
}

func (b *Buffer) AddLine(line string) {
	b.AddLines([]string{line})
}

func (b *Buffer) AddText(text string) {
	// TODO: auto break text
	lines := []string{text}
	b.AddLines(lines)
}

func (b *Buffer) ClearLines() {
	b.lines = []string{}
	b.ForceRedraw()
}

func (b *Buffer) RemoveLast() {
	b.lines = b.lines[:len(b.lines)-1]
	b.ForceRedraw()
}

func (b *Buffer) Remove(idx int) {
	b.lines = append(b.lines[:idx], b.lines[idx+1:]...)
	b.ForceRedraw()
}

func (b *Buffer) PrefixLine(idx int, prefix string) {
	b.lines[idx] = prefix + b.lines[idx]
	b.ForceRedraw()
}

func (b *Buffer) LinesSeq() iter.Seq[string] {
	return func(yield func(string) bool) {
		for _, l := range b.lines {
			if !yield(l) {
				return
			}
		}
	}
}

func (*Buffer) IsScrollable() bool { return true }

func (b *Buffer) Scroll(x, y int) {
	if y == 0 {
		return
	}

	if y < 0 && b.pos > 0 {
		b.pos--
	} else if y > 0 && b.pos < len(b.lines)-1 {
		b.pos++
	}
	b.ForceRedraw()
}

func (b *Buffer) Bg(bg color.Color) *Buffer {
	b.bg = bg
	return b
}

func (b *Buffer) Fg(fg color.Color) *Buffer {
	b.fg = fg
	return b
}