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/*
* Copyright © 2020-present Peter M. Stahl pemistahl@gmail.com
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either expressed or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
use std::collections::HashSet;
use crate::detector::LanguageDetector;
use crate::isocode::{IsoCode639_1, IsoCode639_3};
use crate::language::Language;
pub(crate) const MISSING_LANGUAGE_MESSAGE: &str =
"LanguageDetector needs at least 2 languages to choose from";
pub(crate) const MINIMUM_RELATIVE_DISTANCE_MESSAGE: &str =
"Minimum relative distance must lie in between 0.0 and 0.99";
/// This struct configures and creates an instance of [LanguageDetector].
#[derive(Clone)]
#[cfg_attr(feature = "python", pyo3::prelude::pyclass)]
pub struct LanguageDetectorBuilder {
languages: HashSet<Language>,
minimum_relative_distance: f64,
is_every_language_model_preloaded: bool,
is_low_accuracy_mode_enabled: bool,
}
impl LanguageDetectorBuilder {
/// Creates and returns an instance of `LanguageDetectorBuilder` with all built-in languages.
pub fn from_all_languages() -> Self {
Self::from(Language::all())
}
/// Creates and returns an instance of `LanguageDetectorBuilder`
/// with all built-in spoken languages.
pub fn from_all_spoken_languages() -> Self {
Self::from(Language::all_spoken_ones())
}
/// Creates and returns an instance of `LanguageDetectorBuilder`
/// with all built-in languages supporting the Arabic script.
pub fn from_all_languages_with_arabic_script() -> Self {
Self::from(Language::all_with_arabic_script())
}
/// Creates and returns an instance of `LanguageDetectorBuilder`
/// with all built-in languages supporting the Cyrillic script.
pub fn from_all_languages_with_cyrillic_script() -> Self {
Self::from(Language::all_with_cyrillic_script())
}
/// Creates and returns an instance of `LanguageDetectorBuilder`
/// with all built-in languages supporting the Devanagari script.
pub fn from_all_languages_with_devanagari_script() -> Self {
Self::from(Language::all_with_devanagari_script())
}
/// Creates and returns an instance of `LanguageDetectorBuilder`
/// with all built-in languages supporting the Latin script.
pub fn from_all_languages_with_latin_script() -> Self {
Self::from(Language::all_with_latin_script())
}
/// Creates and returns an instance of `LanguageDetectorBuilder`
/// with all built-in languages except those specified in `languages`.
///
/// ⚠ Panics if less than two `languages` are used to build the
/// `LanguageDetector`.
pub fn from_all_languages_without(languages: &[Language]) -> Self {
let mut languages_to_load = Language::all();
languages_to_load.retain(|it| !languages.contains(it));
if languages_to_load.len() < 2 {
panic!("{}", MISSING_LANGUAGE_MESSAGE);
}
Self::from(languages_to_load)
}
/// Creates and returns an instance of `LanguageDetectorBuilder`
/// with the specified `languages`.
///
/// ⚠ Panics if less than two `languages` are specified.
pub fn from_languages(languages: &[Language]) -> Self {
if languages.len() < 2 {
panic!("{}", MISSING_LANGUAGE_MESSAGE);
}
Self::from(languages.iter().cloned().collect())
}
/// Creates and returns an instance of `LanguageDetectorBuilder`
/// with the languages specified by the respective ISO 639-1 codes.
///
/// ⚠ Panics if less than two `iso_codes` are specified.
pub fn from_iso_codes_639_1(iso_codes: &[IsoCode639_1]) -> Self {
if iso_codes.len() < 2 {
panic!("{}", MISSING_LANGUAGE_MESSAGE);
}
let languages = iso_codes
.iter()
.map(Language::from_iso_code_639_1)
.collect::<HashSet<_>>();
Self::from(languages)
}
/// Creates and returns an instance of `LanguageDetectorBuilder`
/// with the languages specified by the respective ISO 639-3 codes.
///
/// ⚠ Panics if less than two `iso_codes` are specified.
pub fn from_iso_codes_639_3(iso_codes: &[IsoCode639_3]) -> Self {
if iso_codes.len() < 2 {
panic!("{}", MISSING_LANGUAGE_MESSAGE);
}
let languages = iso_codes
.iter()
.map(Language::from_iso_code_639_3)
.collect::<HashSet<_>>();
Self::from(languages)
}
/// Sets the desired value for the minimum relative distance measure.
///
/// By default, *Lingua* returns the most likely language for a given
/// input text. However, there are certain words that are spelled the
/// same in more than one language. The word *prologue*, for instance,
/// is both a valid English and French word. Lingua would output either
/// English or French which might be wrong in the given context.
/// For cases like that, it is possible to specify a minimum relative
/// distance that the logarithmized and summed up probabilities for
/// each possible language have to satisfy.
///
/// Be aware that the distance between the language probabilities is
/// dependent on the length of the input text. The longer the input
/// text, the larger the distance between the languages. So if you
/// want to classify very short text phrases, do not set the minimum
/// relative distance too high. Otherwise you will get most results
/// returned as [`None`] which is the return value for cases
/// where language detection is not reliably possible.
///
/// ⚠ Panics if `distance` is smaller than 0.0 or greater than 0.99.
pub fn with_minimum_relative_distance(&mut self, distance: f64) -> &mut Self {
if !(0.0..=0.99).contains(&distance) {
panic!("{}", MINIMUM_RELATIVE_DISTANCE_MESSAGE);
}
self.minimum_relative_distance = distance;
self
}
/// Configures `LanguageDetectorBuilder` to preload all language models when creating
/// the instance of [LanguageDetector].
///
/// By default, *Lingua* uses lazy-loading to load only those language models
/// on demand which are considered relevant by the rule-based filter engine.
/// For web services, for instance, it is rather beneficial to preload all language
/// models into memory to avoid unexpected latency while waiting for the
/// service response. This method allows to switch between these two loading modes.
pub fn with_preloaded_language_models(&mut self) -> &mut Self {
self.is_every_language_model_preloaded = true;
self
}
/// Disables the high accuracy mode in order to save memory and increase performance.
///
/// By default, *Lingua's* high detection accuracy comes at the cost of loading large
/// language models into memory which might not be feasible for systems running low on
/// resources.
///
/// This method disables the high accuracy mode so that only a small subset of language
/// models is loaded into memory. The downside of this approach is that detection accuracy
/// for short texts consisting of less than 120 characters will drop significantly. However,
/// detection accuracy for texts which are longer than 120 characters will remain mostly
/// unaffected.
pub fn with_low_accuracy_mode(&mut self) -> &mut Self {
self.is_low_accuracy_mode_enabled = true;
self
}
/// Creates and returns the configured instance of [LanguageDetector].
pub fn build(&mut self) -> LanguageDetector {
LanguageDetector::from(
self.languages.clone(),
self.minimum_relative_distance,
self.is_every_language_model_preloaded,
self.is_low_accuracy_mode_enabled,
)
}
fn from(languages: HashSet<Language>) -> Self {
Self {
languages,
minimum_relative_distance: 0.0,
is_every_language_model_preloaded: false,
is_low_accuracy_mode_enabled: false,
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn assert_detector_can_be_built_from_all_languages() {
let mut builder = LanguageDetectorBuilder::from_all_languages();
assert_eq!(builder.languages, Language::all());
assert_eq!(builder.minimum_relative_distance, 0.0);
builder.with_minimum_relative_distance(0.2);
assert_eq!(builder.minimum_relative_distance, 0.2);
}
#[test]
fn assert_detector_can_be_built_from_spoken_languages() {
let mut builder = LanguageDetectorBuilder::from_all_spoken_languages();
assert_eq!(builder.languages, Language::all_spoken_ones());
assert_eq!(builder.minimum_relative_distance, 0.0);
builder.with_minimum_relative_distance(0.2);
assert_eq!(builder.minimum_relative_distance, 0.2);
}
#[test]
fn assert_detector_can_be_built_from_languages_with_arabic_script() {
let builder = LanguageDetectorBuilder::from_all_languages_with_arabic_script();
assert_eq!(builder.languages, Language::all_with_arabic_script());
}
#[test]
fn assert_detector_can_be_built_from_languages_with_cyrillic_script() {
let builder = LanguageDetectorBuilder::from_all_languages_with_cyrillic_script();
assert_eq!(builder.languages, Language::all_with_cyrillic_script());
}
#[test]
fn assert_detector_can_be_built_from_languages_with_devanagari_script() {
let builder = LanguageDetectorBuilder::from_all_languages_with_devanagari_script();
assert_eq!(builder.languages, Language::all_with_devanagari_script());
}
#[test]
fn assert_detector_can_be_built_from_languages_with_latin_script() {
let builder = LanguageDetectorBuilder::from_all_languages_with_latin_script();
assert_eq!(builder.languages, Language::all_with_latin_script());
}
#[test]
fn assert_detector_can_be_built_from_blacklist() {
let builder = LanguageDetectorBuilder::from_all_languages_without(&[
Language::Turkish,
Language::Romanian,
]);
let expected_languages = Language::all()
.difference(&hashset!(Language::Turkish, Language::Romanian))
.cloned()
.collect::<HashSet<Language>>();
assert_eq!(builder.languages, expected_languages);
}
#[test]
#[should_panic(expected = "LanguageDetector needs at least 2 languages to choose from")]
fn assert_detector_cannot_be_built_from_too_long_blacklist() {
let languages = Language::all()
.difference(&hashset!(Language::German))
.cloned()
.collect::<Vec<_>>();
LanguageDetectorBuilder::from_all_languages_without(&languages);
}
#[test]
fn assert_detector_can_be_built_from_whitelist() {
let builder =
LanguageDetectorBuilder::from_languages(&[Language::German, Language::English]);
assert_eq!(
builder.languages,
hashset!(Language::German, Language::English)
);
}
#[test]
#[should_panic(expected = "LanguageDetector needs at least 2 languages to choose from")]
fn assert_detector_cannot_be_built_from_too_short_whitelist() {
LanguageDetectorBuilder::from_languages(&[Language::German]);
}
#[test]
fn assert_detector_can_be_built_from_iso_639_1_codes() {
let builder =
LanguageDetectorBuilder::from_iso_codes_639_1(&[IsoCode639_1::DE, IsoCode639_1::ZU]);
assert_eq!(
builder.languages,
hashset!(Language::German, Language::Zulu)
);
}
#[test]
#[should_panic(expected = "LanguageDetector needs at least 2 languages to choose from")]
fn assert_detector_cannot_be_built_from_too_few_iso_639_1_codes() {
LanguageDetectorBuilder::from_iso_codes_639_1(&[IsoCode639_1::DE]);
}
#[test]
fn assert_detector_can_be_built_from_iso_639_3_codes() {
let builder =
LanguageDetectorBuilder::from_iso_codes_639_3(&[IsoCode639_3::DEU, IsoCode639_3::ZUL]);
assert_eq!(
builder.languages,
hashset!(Language::German, Language::Zulu)
);
}
#[test]
#[should_panic(expected = "LanguageDetector needs at least 2 languages to choose from")]
fn assert_detector_cannot_be_built_from_too_few_iso_639_3_codes() {
LanguageDetectorBuilder::from_iso_codes_639_3(&[IsoCode639_3::DEU]);
}
#[test]
#[should_panic(expected = "Minimum relative distance must lie in between 0.0 and 0.99")]
fn assert_detector_cannot_be_built_from_too_small_minimum_relative_distance() {
LanguageDetectorBuilder::from_all_languages().with_minimum_relative_distance(-2.3);
}
#[test]
#[should_panic(expected = "Minimum relative distance must lie in between 0.0 and 0.99")]
fn assert_detector_cannot_be_built_from_too_large_minimum_relative_distance() {
LanguageDetectorBuilder::from_all_languages().with_minimum_relative_distance(1.7);
}
}