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use std::collections::HashMap;
use crate::regex::RegexToken;
#[derive(Debug, Clone, PartialEq)]
struct State {
id: usize,
transitions: Vec<(usize, char)>,
}
impl State {
fn new(id: usize) -> Self {
Self {
id,
transitions: Vec::new(),
}
}
}
#[derive(Debug, Clone, PartialEq)]
pub struct NFA {
states: HashMap<usize, State>,
transitions: HashMap<usize, Vec<usize>>,
initial_state: usize,
accepting_states: Vec<usize>,
}
impl NFA {
pub fn new() -> Self {
Self {
states: HashMap::new(),
transitions: HashMap::new(),
initial_state: 0,
accepting_states: Vec::new(),
}
}
pub fn add_state(&mut self) -> usize {
let new_state = State::new(self.states.len());
let id = new_state.id;
self.states.insert(id, new_state);
id
}
pub fn regex_to_nfa(&mut self, input: RegexToken) {
match input {
RegexToken::Symbol(ch) => {
let state_1 = self.add_state();
self.add_transition(state_1, state_1 + 1, ch);
}
RegexToken::Concat((left, right)) => {
self.regex_to_nfa(*left);
self.regex_to_nfa(*right);
}
RegexToken::Union(_) => todo!(),
RegexToken::Plus(_) => todo!(),
RegexToken::Star(_) => todo!(),
RegexToken::Dot => {
self.add_state();
}
RegexToken::None => {
self.add_state();
}
}
}
pub fn add_transition(&mut self, from: usize, to: usize, trans: char) {
self.transitions
.entry(from)
.and_modify(|val| val.push(to))
.or_insert_with(|| vec![to]);
self.states
.get_mut(&from)
.unwrap()
.transitions
.push((to, trans));
}
fn deduce_accepting_states(&mut self) {
for (id, state) in &self.states {
if state.transitions.is_empty() {
self.accepting_states.push(*id)
}
}
}
pub fn simulate(&mut self, input: String) -> bool {
let mut current = self.states.get(&self.initial_state).unwrap();
let mut chars = input.chars();
'simu: while let Some(nxt) = chars.next() {
println!("current: {current:?}");
for (id, ch) in ¤t.transitions {
println!("nxt: {nxt} ch: {ch}");
if *ch == nxt {
current = self.states.get(id).unwrap();
} else {
break 'simu;
}
}
}
println!("current node: {current:?}");
let current_id = current.id;
self.deduce_accepting_states();
self.accepting_states.iter().any(|&id| id == current_id)
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::regex::Regex;
#[test]
fn test_simple_succ() {
let input = "abc";
let token = Regex::new(String::from(input));
let mut nfa = NFA::new();
nfa.regex_to_nfa(token);
nfa.add_state();
let inp = "abc";
let output = nfa.simulate(String::from(inp));
assert!(output)
}
#[test]
fn test_simple_fail() {
let input = "abc";
let token = Regex::new(String::from(input));
let mut nfa = NFA::new();
nfa.regex_to_nfa(token);
nfa.add_state();
let inp = "abd";
let output = nfa.simulate(String::from(inp));
assert!(!output)
}
}
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