justcaptcha/pkg/captcha/captcha.go

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package captcha
import (
"crypto/rand"
"errors"
"image"
"math/big"
"time"
)
const (
maxAnswer = 999999
)
var errorNotFound = errors.New("captcha not found")
type Answer string
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// ICaptcha interface that should be implemented by captcha.
type ICaptcha interface {
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// generateImage is used to create a captcha image.
generateImage(style string) *image.Image
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// GetImage() returns an image of captcha. Calls
// generateImage() method if image doesn't exist.
GetImage(style string) *image.Image
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// GetAnswer returns a pregenerated answer.
GetAnswer() Answer
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// Solve compares a stored answer with a passed one.
// Sets field Solved to true if they are equal.
Solve(answer Answer) bool
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// IsSolved returns field IsSolved.
IsSolved() bool
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// Expiry returns a date after what captcha will expire.
Expiry() time.Time
}
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// Captcha is a base implementation of a CAPTCHA.
//
// All derivatives that embed this struct only need to
// implement GetImage() and generateImage() methods.
// And GetImage() could simply be copied.
//
// You need to do that because in Go there is no inheritance,
// and if you won't do that, calling a base GetImage
// method will call an empty base generateImage() method.
type Captcha struct {
Image image.Image
Answer Answer
Solved bool
ExpireIn time.Time
}
func (c *Captcha) generateImage(style string) *image.Image {
return nil
}
func (c *Captcha) GetImage(style string) *image.Image {
if c.Image == nil {
return c.generateImage(style)
}
return &c.Image
}
func (c *Captcha) Solve(answer Answer) bool {
c.Solved = c.Answer == answer
return c.Solved
}
func (c *Captcha) GetAnswer() Answer {
if c.Answer == "" {
c.Answer = generateAnswer()
}
return c.Answer
}
func (c *Captcha) IsSolved() bool {
return c.Solved
}
func (c *Captcha) Expiry() time.Time {
return c.ExpireIn
}
func generateAnswer() Answer {
ans, _ := rand.Int(rand.Reader, big.NewInt(maxAnswer))
return (Answer(ans.String()))
}
func ExpiryDate(expiry time.Duration) time.Time {
return time.Now().Add(expiry)
}