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// Copyright 2019 Fredrik Portström <https://portstrom.com>
// This is free software distributed under the terms specified in
// the file LICENSE at the top-level directory of this distribution.
use crate::case_folding_simple::CASE_FOLDING_SIMPLE;
struct Character<T> {
character: u8,
next_state: State<T>,
}
#[derive(Clone, Copy)]
enum State<T> {
Continue(u32),
Final(T),
}
pub struct Trie<T> {
states: Vec<Vec<Character<T>>>,
}
impl<T: Copy> Trie<T> {
pub fn add_case_sensitive_term(&mut self, term: &str, payload: T) -> bool {
self.add_term_internal(term, payload, false)
}
fn add_folded_characters(&mut self, character: char, initial_state: u32, next_state: State<T>) {
if let Some(folded_characters) = simple_fold(character) {
for character in folded_characters {
let mut last_state = initial_state;
let mut character_buffer = [0; 4];
let character_bytes = character.encode_utf8(&mut character_buffer).as_bytes();
let mut byte_iterator = character_bytes.iter().cloned();
let mut byte_item = byte_iterator.next();
'b: while let Some(byte) = byte_item {
for item in &self.states[last_state as usize] {
if item.character == byte {
match item.next_state {
State::Continue(next_state) => last_state = next_state,
State::Final(_) => unreachable!(),
}
byte_item = byte_iterator.next();
continue 'b;
}
}
byte_item = byte_iterator.next();
if byte_item.is_none() {
self.states[last_state as usize].push(Character {
character: byte,
next_state,
});
break;
}
let intermediate_state = self.states.len() as _;
self.states[last_state as usize].push(Character {
character: byte,
next_state: State::Continue(intermediate_state),
});
last_state = intermediate_state;
self.states.push(vec![]);
}
}
}
}
pub fn add_term(&mut self, term: &str, payload: T) -> bool {
self.add_term_internal(term, payload, true)
}
fn add_term_internal(&mut self, term: &str, payload: T, case_folded: bool) -> bool {
let mut last_state = 0;
let mut character_iterator = term.chars();
let mut character_item = character_iterator.next();
while let Some(character) = character_item {
let mut character_buffer = [0; 4];
let character_bytes = character.encode_utf8(&mut character_buffer).as_bytes();
character_item = character_iterator.next();
let mut byte_iterator = character_bytes.iter().cloned();
let mut byte_item = byte_iterator.next();
let state_before_character = last_state;
'a: while let Some(byte) = byte_item {
for item in &self.states[last_state as usize] {
if item.character == byte {
match item.next_state {
State::Continue(next_state) => last_state = next_state,
State::Final(_) => return false,
}
byte_item = byte_iterator.next();
continue 'a;
}
}
byte_item = byte_iterator.next();
if byte_item.is_none() {
if character_item.is_none() {
self.states[last_state as usize].push(Character {
character: byte,
next_state: State::Final(payload),
});
if case_folded {
self.add_folded_characters(
character,
state_before_character,
State::Final(payload),
);
}
return true;
}
let next_state = self.states.len() as _;
self.states[last_state as usize].push(Character {
character: byte,
next_state: State::Continue(next_state),
});
self.states.push(vec![]);
if case_folded {
self.add_folded_characters(
character,
state_before_character,
State::Continue(next_state),
);
}
last_state = next_state;
break;
}
let next_state = self.states.len() as _;
self.states[last_state as usize].push(Character {
character: byte,
next_state: State::Continue(next_state),
});
last_state = next_state;
self.states.push(vec![]);
}
}
false
}
pub fn find(&self, text: &str) -> Result<(usize, T), usize> {
let mut state = 0;
'outer: for (position, character1) in text.as_bytes().iter().cloned().enumerate() {
for character2 in &self.states[state as usize] {
if character1 == character2.character {
match character2.next_state {
State::Continue(next_state) => {
state = next_state;
continue 'outer;
}
State::Final(payload) => return Ok((position + 1, payload)),
}
}
}
return Err(position);
}
Err(0)
}
pub fn new() -> Self {
Trie {
states: vec![vec![]],
}
}
}
fn simple_fold(character: char) -> Option<&'static [char]> {
match CASE_FOLDING_SIMPLE.binary_search_by_key(&character, |&(character, _)| character) {
Err(_) => None,
Ok(index) => Some(CASE_FOLDING_SIMPLE[index].1),
}
}
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