41 lines
1.1 KiB
Go
41 lines
1.1 KiB
Go
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package usecase
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import (
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"crypto/rand"
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"errors"
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"fmt"
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"math/big"
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)
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// ErrInvalidDigits is returned when the number of digits is invalid
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var ErrInvalidDigits = errors.New("invalid number of digits")
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// generateVerifyCode generates a cryptographically secure verification code.
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// The digits parameter specifies the number of digits in the code (4-10).
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// If digits is 0 or negative, it defaults to 6 digits.
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func generateVerifyCode(digits int) (string, error) {
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// Default to 6 digits if not specified or invalid
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if digits <= 0 {
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digits = 6
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}
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// Validate digit range
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if digits < 4 || digits > 10 {
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return "", fmt.Errorf("%w: digits must be between 4 and 10, got %d", ErrInvalidDigits, digits)
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}
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// Calculate maximum value (10^digits - 1)
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exp := new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(digits)), nil)
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// Generate cryptographically secure random number
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randomNumber, err := rand.Int(rand.Reader, exp)
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if err != nil {
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return "", fmt.Errorf("failed to generate random number: %w", err)
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}
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// Convert to string with zero padding
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verifyCode := fmt.Sprintf("%0*d", digits, randomNumber)
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return verifyCode, nil
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}
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