package main

import (
	"bytes"
	"image/color"
	"image/png"

	"github.com/fogleman/gg"
	"golang.org/x/image/font"
)

type BackgroundType int

const (
	Transparent BackgroundType = iota
	White
	Black
	Gradient
)

type Image struct {
	ctx     *gg.Context
	face    font.Face
	bgType  BackgroundType
	fgColor color.Color
}

func NewImage(ctx *gg.Context, bgType BackgroundType, face font.Face) Image {
	fgColor := color.Black
	if bgType == Transparent || bgType == Black || bgType == Gradient {
		fgColor = color.White
	}
	return Image{
		ctx:     ctx,
		bgType:  bgType,
		fgColor: fgColor,
		face:    face,
	}
}

func (img *Image) GenText(text string) {
	img.MakeBackground()
	img.Print(text)
}

func (img *Image) ToBytes() (*[]byte, error) {
	buff := new(bytes.Buffer)
	err := png.Encode(buff, img.ctx.Image())
	if err != nil {
		return nil, err
	}
	b := buff.Bytes()
	return &b, nil
}

func (img *Image) MakeBackground() {
	if img.bgType == Transparent {
		return
	}
	if img.bgType == Gradient {
		img.fillGradient()
	} else {
		img.fillBG()
	}
}

func (img *Image) Print(text string) {
	imgW, imgH := img.ctx.Width(), img.ctx.Height()
	img.ctx.SetColor(img.fgColor)
	img.ctx.SetFontFace(img.face)
	img.ctx.DrawStringWrapped(text, float64(imgW)/2, float64(imgH)/2, 0.5, 0.5, 600, 1, gg.AlignCenter)
}

func (img *Image) fillGradient() {
	imgW, imgH := img.ctx.Width(), img.ctx.Height()
	grad := gg.NewLinearGradient(0, 0, 0, float64(imgH))
	grad.AddColorStop(0, color.RGBA{200, 50, 50, 255})
	grad.AddColorStop(1, color.RGBA{20, 0, 0, 255})
	img.ctx.SetFillStyle(grad)
	img.ctx.DrawRectangle(0, 0, float64(imgW), float64(imgH))
	img.ctx.Fill()
}

func (img *Image) fillBG() {
	col := color.White
	if img.bgType == Black {
		col = color.Black
	}
	imgW, imgH := img.ctx.Width(), img.ctx.Height()
	img.ctx.SetFillStyle(gg.NewSolidPattern(col))
	img.ctx.DrawRectangle(0, 0, float64(imgW), float64(imgH))
	img.ctx.Fill()
}