MeiliSearch/meilidb-tokenizer/src/lib.rs

296 lines
10 KiB
Rust
Raw Normal View History

use std::iter::Peekable;
use slice_group_by::StrGroupBy;
use self::SeparatorCategory::*;
pub fn is_cjk(c: char) -> bool {
(c >= '\u{2e80}' && c <= '\u{2eff}') ||
(c >= '\u{2f00}' && c <= '\u{2fdf}') ||
(c >= '\u{3040}' && c <= '\u{309f}') ||
(c >= '\u{30a0}' && c <= '\u{30ff}') ||
(c >= '\u{3100}' && c <= '\u{312f}') ||
(c >= '\u{3200}' && c <= '\u{32ff}') ||
(c >= '\u{3400}' && c <= '\u{4dbf}') ||
(c >= '\u{4e00}' && c <= '\u{9fff}') ||
(c >= '\u{f900}' && c <= '\u{faff}')
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum SeparatorCategory {
Soft,
Hard,
}
impl SeparatorCategory {
fn merge(self, other: SeparatorCategory) -> SeparatorCategory {
if let (Soft, Soft) = (self, other) { Soft } else { Hard }
}
fn to_usize(self) -> usize {
match self {
Soft => 1,
Hard => 8,
}
}
}
fn is_separator(c: char) -> bool {
classify_separator(c).is_some()
}
fn classify_separator(c: char) -> Option<SeparatorCategory> {
match c {
' ' | '-' | '_' | '\'' | ':' | '"' => Some(Soft),
'.' | ';' | ',' | '!' | '?' | '(' | ')' => Some(Hard),
_ => None,
}
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum CharCategory {
Separator(SeparatorCategory),
Cjk,
Other,
}
fn classify_char(c: char) -> CharCategory {
if let Some(category) = classify_separator(c) {
CharCategory::Separator(category)
} else if is_cjk(c) {
CharCategory::Cjk
} else {
CharCategory::Other
}
}
fn is_str_word(s: &str) -> bool {
!s.chars().any(is_separator)
}
fn same_group_category(a: char, b: char) -> bool {
match (classify_char(a), classify_char(b)) {
(CharCategory::Cjk, _) | (_, CharCategory::Cjk) => false,
(CharCategory::Separator(_), CharCategory::Separator(_)) => true,
(a, b) => a == b,
}
}
// fold the number of chars along with the index position
fn chars_count_index((n, _): (usize, usize), (i, c): (usize, char)) -> (usize, usize) {
(n + 1, i + c.len_utf8())
}
pub fn split_query_string(query: &str) -> impl Iterator<Item=&str> {
Tokenizer::new(query).map(|t| t.word)
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub struct Token<'a> {
pub word: &'a str,
pub word_index: usize,
pub char_index: usize,
}
pub struct Tokenizer<'a> {
inner: &'a str,
word_index: usize,
char_index: usize,
}
impl<'a> Tokenizer<'a> {
pub fn new(string: &str) -> Tokenizer {
// skip every separator and set `char_index`
// to the number of char trimmed
let (count, index) = string.char_indices()
.take_while(|(_, c)| is_separator(*c))
.fold((0, 0), chars_count_index);
Tokenizer {
inner: &string[index..],
word_index: 0,
char_index: count,
}
}
}
impl<'a> Iterator for Tokenizer<'a> {
type Item = Token<'a>;
fn next(&mut self) -> Option<Self::Item> {
let mut iter = self.inner.linear_group_by(same_group_category).peekable();
while let (Some(string), next_string) = (iter.next(), iter.peek()) {
let (count, index) = string.char_indices().fold((0, 0), chars_count_index);
if !is_str_word(string) {
self.word_index += string.chars()
.filter_map(classify_separator)
.fold(Soft, |a, x| a.merge(x))
.to_usize();
self.char_index += count;
self.inner = &self.inner[index..];
continue;
}
let token = Token {
word: string,
word_index: self.word_index,
char_index: self.char_index,
};
if next_string.filter(|s| is_str_word(s)).is_some() {
self.word_index += 1;
}
self.char_index += count;
self.inner = &self.inner[index..];
return Some(token);
}
self.inner = "";
None
}
}
pub struct SeqTokenizer<'a, I>
where I: Iterator<Item=&'a str>,
{
inner: I,
current: Option<Peekable<Tokenizer<'a>>>,
word_offset: usize,
char_offset: usize,
}
impl<'a, I> SeqTokenizer<'a, I>
where I: Iterator<Item=&'a str>,
{
pub fn new(mut iter: I) -> SeqTokenizer<'a, I> {
let current = iter.next().map(|s| Tokenizer::new(s).peekable());
SeqTokenizer {
inner: iter,
current: current,
word_offset: 0,
char_offset: 0,
}
}
}
impl<'a, I> Iterator for SeqTokenizer<'a, I>
where I: Iterator<Item=&'a str>,
{
type Item = Token<'a>;
fn next(&mut self) -> Option<Self::Item> {
match &mut self.current {
Some(current) => {
match current.next() {
Some(token) => {
// we must apply the word and char offsets
// to the token before returning it
let token = Token {
word: token.word,
word_index: token.word_index + self.word_offset,
char_index: token.char_index + self.char_offset,
};
// if this is the last iteration on this text
// we must save the offsets for next texts
if current.peek().is_none() {
let hard_space = SeparatorCategory::Hard.to_usize();
self.word_offset = token.word_index + hard_space;
self.char_offset = token.char_index + hard_space;
}
Some(token)
},
None => {
// no more words in this text we must
// start tokenizing the next text
self.current = self.inner.next().map(|s| Tokenizer::new(s).peekable());
self.next()
},
}
},
// no more texts available
None => None,
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn easy() {
let mut tokenizer = Tokenizer::new("salut");
assert_eq!(tokenizer.next(), Some(Token { word: "salut", word_index: 0, char_index: 0 }));
assert_eq!(tokenizer.next(), None);
let mut tokenizer = Tokenizer::new("yo ");
assert_eq!(tokenizer.next(), Some(Token { word: "yo", word_index: 0, char_index: 0 }));
assert_eq!(tokenizer.next(), None);
}
#[test]
fn hard() {
let mut tokenizer = Tokenizer::new(" .? yo lolo. aïe (ouch)");
assert_eq!(tokenizer.next(), Some(Token { word: "yo", word_index: 0, char_index: 4 }));
assert_eq!(tokenizer.next(), Some(Token { word: "lolo", word_index: 1, char_index: 7 }));
assert_eq!(tokenizer.next(), Some(Token { word: "aïe", word_index: 9, char_index: 13 }));
assert_eq!(tokenizer.next(), Some(Token { word: "ouch", word_index: 17, char_index: 18 }));
assert_eq!(tokenizer.next(), None);
let mut tokenizer = Tokenizer::new("yo ! lolo ? wtf - lol . aïe ,");
assert_eq!(tokenizer.next(), Some(Token { word: "yo", word_index: 0, char_index: 0 }));
assert_eq!(tokenizer.next(), Some(Token { word: "lolo", word_index: 8, char_index: 5 }));
assert_eq!(tokenizer.next(), Some(Token { word: "wtf", word_index: 16, char_index: 12 }));
assert_eq!(tokenizer.next(), Some(Token { word: "lol", word_index: 17, char_index: 18 }));
assert_eq!(tokenizer.next(), Some(Token { word: "aïe", word_index: 25, char_index: 24 }));
assert_eq!(tokenizer.next(), None);
}
#[test]
fn hard_long_chars() {
let mut tokenizer = Tokenizer::new(" .? yo 😂. aïe");
assert_eq!(tokenizer.next(), Some(Token { word: "yo", word_index: 0, char_index: 4 }));
assert_eq!(tokenizer.next(), Some(Token { word: "😂", word_index: 1, char_index: 7 }));
assert_eq!(tokenizer.next(), Some(Token { word: "aïe", word_index: 9, char_index: 10 }));
assert_eq!(tokenizer.next(), None);
let mut tokenizer = Tokenizer::new("yo ! lolo ? 😱 - lol . 😣 ,");
assert_eq!(tokenizer.next(), Some(Token { word: "yo", word_index: 0, char_index: 0 }));
assert_eq!(tokenizer.next(), Some(Token { word: "lolo", word_index: 8, char_index: 5 }));
assert_eq!(tokenizer.next(), Some(Token { word: "😱", word_index: 16, char_index: 12 }));
assert_eq!(tokenizer.next(), Some(Token { word: "lol", word_index: 17, char_index: 16 }));
assert_eq!(tokenizer.next(), Some(Token { word: "😣", word_index: 25, char_index: 22 }));
assert_eq!(tokenizer.next(), None);
}
#[test]
fn hard_kanjis() {
let mut tokenizer = Tokenizer::new("\u{2ec4}lolilol\u{2ec7}");
assert_eq!(tokenizer.next(), Some(Token { word: "\u{2ec4}", word_index: 0, char_index: 0 }));
assert_eq!(tokenizer.next(), Some(Token { word: "lolilol", word_index: 1, char_index: 1 }));
assert_eq!(tokenizer.next(), Some(Token { word: "\u{2ec7}", word_index: 2, char_index: 8 }));
assert_eq!(tokenizer.next(), None);
let mut tokenizer = Tokenizer::new("\u{2ec4}\u{2ed3}\u{2ef2} lolilol - hello \u{2ec7}");
assert_eq!(tokenizer.next(), Some(Token { word: "\u{2ec4}", word_index: 0, char_index: 0 }));
assert_eq!(tokenizer.next(), Some(Token { word: "\u{2ed3}", word_index: 1, char_index: 1 }));
assert_eq!(tokenizer.next(), Some(Token { word: "\u{2ef2}", word_index: 2, char_index: 2 }));
assert_eq!(tokenizer.next(), Some(Token { word: "lolilol", word_index: 3, char_index: 4 }));
assert_eq!(tokenizer.next(), Some(Token { word: "hello", word_index: 4, char_index: 14 }));
assert_eq!(tokenizer.next(), Some(Token { word: "\u{2ec7}", word_index: 5, char_index: 23 }));
assert_eq!(tokenizer.next(), None);
}
}