justcaptcha/internal/captcha/dwelling_captcha.go

package captcha

import (
	"crypto/rand"
	"image"
	"math/big"
	"time"

	"github.com/fogleman/gg"
)

const (
	dwImageWidth  = 160
	dwImageHeight = 40
)

type DwellingCaptcha struct {
	Captcha
}

func NewDwellingCaptcha(expiry time.Duration) *DwellingCaptcha {
	return &DwellingCaptcha{
		Captcha: Captcha{
			Answer:   GenerateAnswer(),
			ExpireIn: ExpiryDate(expiry)}}
}

func (c *DwellingCaptcha) generateImage() *image.Image {
	ctx := gg.NewContext(dwImageWidth, dwImageHeight)

	// fill background
	ctx.SetRGB255(0x0a, 0x0a, 0x0a)
	ctx.Clear()

	// draw text
	ctx.SetRGB255(0xf5, 0xf5, 0xf5)
	ctx.Scale(4.0, 2.7)
	ctx.DrawStringAnchored(string(c.GetAnswer()), 20, 5, .5, .5)

	// draw lines and points

	ctx.SetRGB255(0x9f, 0x2b, 0x68)
	for i := 0; i < 16; i++ {
		x0, _ := rand.Int(rand.Reader, big.NewInt(int64(ctx.Height())))
		x1, _ := rand.Int(rand.Reader, big.NewInt(int64(ctx.Height())))
		ctx.SetLineWidth(2)
		r, _ := rand.Int(rand.Reader, big.NewInt(int64(4)))
		ctx.DrawPoint(float64(x0.Int64()), float64(x1.Int64()), float64(r.Int64()))
		ctx.DrawLine(float64(x0.Int64()), 0, float64(ctx.Height()), float64(x1.Int64()))
		ctx.Stroke()
	}

	for i := 0; i < 16; i++ {
		x0, _ := rand.Int(rand.Reader, big.NewInt(int64(ctx.Height())))
		x1, _ := rand.Int(rand.Reader, big.NewInt(int64(ctx.Height())))
		ctx.SetLineWidth(2)
		ctx.DrawLine(0, float64(x0.Int64()), float64(x1.Int64()), float64(ctx.Height()))
		r, _ := rand.Int(rand.Reader, big.NewInt(int64(4)))
		ctx.DrawPoint(float64(x0.Int64()), float64(x1.Int64()), float64(r.Int64()))
		ctx.Stroke()
	}

	c.Image = ctx.Image()

	return &c.Image
}

func (c *DwellingCaptcha) GetImage() *image.Image {
	if c.Image == nil {
		return c.generateImage()
	}

	return &c.Image
}

func (c *DwellingCaptcha) Solve(answer Answer) bool {
	c.Solved = c.Answer == answer
	return c.Solved
}

func (c *DwellingCaptcha) GetAnswer() Answer {
	return c.Answer
}

func (c *DwellingCaptcha) IsSolved() bool {
	return c.Solved
}

func (c *DwellingCaptcha) Expiry() time.Time {
	return c.ExpireIn
}