package ui

import (
	"image/color"

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

var (
	BUFFER_BACKGROUND = gray
	BUFFER_FOREGROUND = color.White
)

type Buffer struct {
	X, Y          int
	Width, Height int
	img           *ebiten.Image
	lines         []string
	pos           int
}

func NewBuffer(x, y int, width, height int) *Buffer {
	return &Buffer{x, y, width, height, nil, []string{}, 0}
}

func (b *Buffer) render() {
	img := ebiten.NewImage(b.Width, b.Height)
	img.Fill(BUFFER_BACKGROUND)
	y := 0
	for _, line := range b.lines[b.pos:] {
		bounds := text.BoundString(Font, line)
		y += bounds.Dy()
		if y > b.Height {
			break
		}
		text.Draw(img, line, Font, 0, y, BUFFER_FOREGROUND)
	}
	b.img = img
}

func (b *Buffer) Draw(screen *ebiten.Image) {
	if b.img == nil {
		b.render()
	}
	op := &ebiten.DrawImageOptions{}
	op.GeoM.Translate(float64(b.X), float64(b.Y))
	screen.DrawImage(b.img, op)
}

func (b *Buffer) FindObjectAt(x, y int) interface{} {
	return nil
}

func (b *Buffer) ForceRedraw() {
	b.img = nil
}

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) 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()
}