justcaptcha/pkg/captcha/captcha.go

84 lines
1.8 KiB
Go

package captcha
import (
"crypto/rand"
"image"
"math/big"
"time"
)
const (
maxIntAnswer = 999999
)
type Answer string
func NewIntAnswer() Answer {
ans, _ := rand.Int(rand.Reader, big.NewInt(maxIntAnswer))
return (Answer(ans.String()))
}
// Captcha interface that should be implemented by a CAPTCHA.
type Captcha interface {
// Image generates and returns a pointer to an image of CAPTCHA.
Image(style string) *image.Image
// Answer returns a pregenerated answer.
Answer() Answer
// Solve compares a stored answer with a passed one.
Solve(answer Answer) bool
// IsSolved returns if a CAPTCHA is solved or not.
IsSolved() bool
// Expiry returns a date after what CAPTCHA will expire.
Expiry() time.Time
}
// BaseCaptcha is a base implementation of a CAPTCHA.
//
// All derivatives that embed this struct only need to implement
// an Image() method.
type BaseCaptcha struct {
answer Answer
solved bool
expireIn time.Time
}
func NewBaseCaptcha(expiry time.Duration) *BaseCaptcha {
return &BaseCaptcha{
expireIn: ExpiryDate(expiry),
}
}
func (c *BaseCaptcha) Image(style string) *image.Image {
return nil
}
// Answer generates an integer answer for a CAPTCHA or just returns
// an existing one.
func (c *BaseCaptcha) Answer() Answer {
if c.answer == "" {
c.answer = NewIntAnswer()
}
return c.answer
}
// Solve sets solved field to true if given answer is right and returns a result
// of a check.
func (c *BaseCaptcha) Solve(answer Answer) bool {
c.solved = c.answer == answer
return c.solved
}
func (c *BaseCaptcha) IsSolved() bool {
return c.solved
}
func (c *BaseCaptcha) Expiry() time.Time {
return c.expireIn
}
// ExpiryDate returns a date when CAPTCHA expires. It adds a passed
// expiry duration to a current time.
func ExpiryDate(expiry time.Duration) time.Time {
return time.Now().Add(expiry)
}