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franco.go
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franco.go
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package franco
import (
"encoding/json"
"log"
"os"
"regexp"
"sort"
"strings"
)
const MAX_DIFFERENCE = float64(300)
const MAX_LENGTH = 2048
const MIN_LENGTH = 3
var scripts map[string]languages
var expressions map[string]regexp.Regexp
//Init `scripts` and `expressions` dictionaries
func init() {
var scriptData map[string]interface{}
err := json.Unmarshal([]byte(SCRIPT_DATA), &scriptData)
if err != nil {
log.Printf("Error during languages decoding: %v\n", err)
os.Exit(1)
}
scripts = make(map[string]languages)
for scriptCode, scriptValue := range scriptData {
languages := make(map[string]trigrams)
lang := scriptValue.(map[string]interface{})
for code, trigramsRaw := range lang {
trigramsString := trigramsRaw.(string)
trigramsStringArray := strings.Split(trigramsString, "|")
trigrams := make(map[string]int)
for i := len(trigramsStringArray) - 1; i >= 0; i-- {
trigrams[trigramsStringArray[i]] = i + 1
}
languages[code] = trigrams
}
scripts[scriptCode] = languages
}
var expressionsData map[string]interface{}
err = json.Unmarshal([]byte(EXPRESSION_DATA), &expressionsData)
if err != nil {
log.Printf("Error during expressions decoding: %v\n", err)
os.Exit(1)
}
expressions = make(map[string]regexp.Regexp)
for code, v := range expressionsData {
expressions[code] = *regexp.MustCompile(v.(string))
}
}
//Filter `languages` by removing languages in `blacklist`, or including languages in `whitelist`.
func filterLanguages(langs languages, whitelist []string, blacklist []string) languages {
filteredLanguages := make(languages)
if len(whitelist) == 0 && len(blacklist) == 0 {
return langs
}
if len(whitelist) == 0 {
filteredLanguages = langs
} else {
for _, code := range whitelist {
filteredLanguages[code] = langs[code]
}
}
for _, code := range blacklist {
if _, ok := filteredLanguages[code]; ok {
delete(filteredLanguages, code)
}
}
return filteredLanguages
}
//Get the distance between `trigrams`, and a trigram `model`.
func getDistance(trigrams tuples, model trigrams) float64 {
distance := float64(0)
for _, t := range trigrams {
difference := float64(0)
if modelVal, ok := model[t.Code]; ok {
difference = t.Count - float64(modelVal)
if difference < 0 {
difference = -difference
}
} else {
difference = MAX_DIFFERENCE
}
distance += difference
}
return distance
}
//Get the distance between `trigrams`, and multiple trigram dictionaries `languages`.
func getDistances(trigrams tuples, languages languages, whitelist []string, blacklist []string) tuples {
filteredLanguages := filterLanguages(languages, whitelist, blacklist)
tuples := make(tuples, 0)
for code, language := range filteredLanguages {
dis := getDistance(trigrams, language)
t := tuple{Code: code, Count: dis}
tuples = append(tuples, t)
}
return tuples
}
//Get the occurrence ratio of `expression` for `value`.
func getOccurrence(value string, expression regexp.Regexp) float64 {
count := len(expression.FindAllString(value, -1))
if count < 1 {
count = 0
}
return float64(count) / float64(len(value))
}
//From `scripts`, get the most occurring script for `value`
func getTopScript(value string) string {
topCount := float64(-1)
expressionCode := ""
for code, e := range expressions {
count := getOccurrence(value, e)
if count > topCount {
topCount = count
expressionCode = code
}
}
return expressionCode
}
//Create a single tuple as a list of tuples from a given language code.
func singleLanguageTuples(code string) tuples {
tuples := make(tuples, 1)
tuples[0] = tuple{Code: code, Count: 1}
return tuples
}
//Get a list of probable languages the given value is written in.
func DetectWithFilters(value string, whitelist []string, blacklist []string) tuples {
if len(value) < MIN_LENGTH {
return singleLanguageTuples("und")
}
if len(value) > MAX_LENGTH {
value = value[0:MAX_LENGTH]
}
code := getTopScript(value)
if _, ok := scripts[code]; !ok {
return singleLanguageTuples(code)
}
return normalize(value, getDistances(getTrigramsAsTuples(value), scripts[code], whitelist, blacklist))
}
//Get a list of probable languages the given value is written in.
func Detect(value string) tuples {
return DetectWithFilters(value, make([]string, 0), make([]string, 0))
}
//Get the most probable language for the given value.
func DetectOne(value string) tuple {
return Detect(value)[0]
}
//Get the most probable language for the given value.
func DetectOneWithFilters(value string, whitelist []string, blacklist []string) tuple {
return DetectWithFilters(value, whitelist, blacklist)[0]
}
func normalize(value string, distances tuples) tuples {
sort.Sort(distances)
min := distances[0].Count
max := (float64(len(value)) * MAX_DIFFERENCE) - min
for i, d := range distances {
distances[i].Count = float64(1) - ((d.Count - min) / max)
}
return distances
}