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