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similarity.go
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/
similarity.go
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package validator
import (
"fmt"
"strings"
)
// Similarity returns ValidateFunc that validate whether the password is sufficiently different from the attributes
//
// Attributes can be: user login, email, first name, last name, …
func Similarity(attributes []string, maxSimilarity *float64, customError error) ValidateFunc {
if maxSimilarity == nil {
maxSimilarity = new(float64)
*maxSimilarity = 0.7
}
return ValidateFunc(func(password string) error {
for idx := range attributes {
if ratio(password, attributes[idx]) > *maxSimilarity {
if customError != nil {
return customError
}
return fmt.Errorf("The password is too similar to the %s", attributes[idx])
}
}
return nil
})
}
// Return a measure of the sequences' similarity (float in [0,1]).
//
// Where T is the total number of elements in both sequences, and M is the number of matches, this is 2.0*M / T.
// Note that this is 1 if the sequences are identical, and 0 if they have nothing in common.
func ratio(a, b string) float64 {
t := float64(len(a) + len(b))
m := 0.0
sa := strings.Split(a, "")
sb := strings.Split(b, "")
for idx := range sb {
aidx := strings.Index(a, sb[idx])
if aidx > -1 {
sa = append(sa[:aidx], sa[aidx+1:]...)
a = strings.Join(sa, "")
m = m + 1.0
}
}
return 2.0 * m / t
}