package generator

import (
	"github.com/pkg/errors"
	"image"
	"image/color"

	"golang.org/x/image/font"
	"golang.org/x/image/font/basicfont"
	"golang.org/x/image/math/fixed"
)

var (
	errInvalidFormat = errors.New("invalid format")
)

func parseHexColorFast(s string) (color.RGBA, error) {
	var err error
	c := color.RGBA{}
	c.A = 0xff

	if s[0] != '#' {
		return c, errInvalidFormat
	}

	hexToByte := func(b byte) byte {
		switch {
		case b >= '0' && b <= '9':
			return b - '0'
		case b >= 'a' && b <= 'f':
			return b - 'a' + 10
		case b >= 'A' && b <= 'F':
			return b - 'A' + 10
		}
		err = errInvalidFormat
		return 0
	}

	switch len(s) {
	case 7:
		c.R = hexToByte(s[1])<<4 + hexToByte(s[2])
		c.G = hexToByte(s[3])<<4 + hexToByte(s[4])
		c.B = hexToByte(s[5])<<4 + hexToByte(s[6])
	case 4:
		c.R = hexToByte(s[1]) * 17
		c.G = hexToByte(s[2]) * 17
		c.B = hexToByte(s[3]) * 17
	default:
		err = errInvalidFormat
	}
	return c, err
}

func drawText(img *image.RGBA, x, y int, col color.RGBA, text string) {
	point := fixed.Point26_6{fixed.Int26_6(x * 64), fixed.Int26_6(y * 64)}

	d := &font.Drawer{
		Dst:  img,
		Src:  image.NewUniform(col),
		Face: basicfont.Face7x13,
		Dot:  point,
	}
	d.DrawString(text)
}