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package validator
import (
"sort"
"strings"
"github.com/agnivade/levenshtein"
)
// Given an invalid input string and a list of valid options, returns a filtered
// list of valid options sorted based on their similarity with the input.
func SuggestionList(input string, options []string) []string {
var results []string
optionsByDistance := map[string]int{}
for _, option := range options {
distance := lexicalDistance(input, option)
threshold := calcThreshold(input, option)
if distance <= threshold {
results = append(results, option)
optionsByDistance[option] = distance
}
}
sort.Slice(results, func(i, j int) bool {
return optionsByDistance[results[i]] < optionsByDistance[results[j]]
})
return results
}
func calcThreshold(a, b string) (threshold int) {
if len(a) >= len(b) {
threshold = len(a) / 2
} else {
threshold = len(b) / 2
}
if threshold < 1 {
threshold = 1
}
return
}
// Computes the lexical distance between strings A and B.
//
// The "distance" between two strings is given by counting the minimum number
// of edits needed to transform string A into string B. An edit can be an
// insertion, deletion, or substitution of a single character, or a swap of two
// adjacent characters.
//
// Includes a custom alteration from Damerau-Levenshtein to treat case changes
// as a single edit which helps identify mis-cased values with an edit distance
// of 1.
//
// This distance can be useful for detecting typos in input or sorting
func lexicalDistance(a, b string) int {
if a == b {
return 0
}
a = strings.ToLower(a)
b = strings.ToLower(b)
// Any case change counts as a single edit
if a == b {
return 1
}
return levenshtein.ComputeDistance(a, b)
}
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