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use erl_tokenize::LexicalToken;
use crate::traits::{Expect, Parse, ParseTail, TokenRead};
use crate::{Error, ErrorKind, Result};
#[derive(Debug)]
pub struct Parser<T> {
reader: T,
transactions: Vec<Vec<LexicalToken>>,
last_read_error: Option<Error>,
}
impl<T> Parser<T>
where
T: TokenRead,
{
pub fn new(reader: T) -> Self {
Parser {
reader,
transactions: Vec::new(),
last_read_error: None,
}
}
pub fn parse<P: Parse>(&mut self) -> Result<P> {
track!(P::parse(self))
}
pub fn parse_tail<P: ParseTail>(&mut self, head: P::Head) -> Result<P> {
track!(P::parse_tail(self, head))
}
pub fn expect<P: Parse + Expect>(&mut self, expected: &P::Value) -> Result<P> {
self.transaction(|parser| {
let actual = track!(parser.parse::<P>(), "expected={:?}", expected)?;
track!(actual.expect(expected))?;
Ok(actual)
})
}
pub fn expect_any<P: Parse + Expect>(&mut self, expected: &[&P::Value]) -> Result<P> {
let actual = track!(self.parse::<P>())?;
let mut last_error = None;
for e in expected.iter() {
if let Err(e) = track!(actual.expect(e)) {
last_error = Some(e);
} else {
last_error = None;
break;
}
}
if let Some(e) = last_error {
Err(e)
} else {
Ok(actual)
}
}
pub fn peek<F, P>(&mut self, f: F) -> Result<P>
where
F: FnOnce(&mut Self) -> Result<P>,
{
self.start_transaction();
let result = track!(f(self));
self.abort_transaction();
result
}
pub fn transaction<F, P>(&mut self, f: F) -> Result<P>
where
F: FnOnce(&mut Self) -> Result<P>,
{
self.start_transaction();
let result = track!(f(self));
if result.is_ok() {
self.commit_transaction();
} else {
self.abort_transaction();
}
result
}
pub fn eos(&mut self) -> Result<bool> {
if let Some(t) = track!(self.reader.try_read_token())? {
self.reader.unread_token(t);
Ok(false)
} else {
Ok(true)
}
}
fn next_token(&mut self) -> Result<LexicalToken> {
if let Some(ref e) = self.last_read_error {
return Err(e.clone());
}
match self.reader.read_token() {
Err(e) => {
if let ErrorKind::UnexpectedEos = *e.kind() {
} else {
self.last_read_error = Some(e.clone());
}
Err(e)
}
Ok(t) => {
if let Some(tail) = self.transactions.last_mut() {
tail.push(t.clone());
}
Ok(t)
}
}
}
fn start_transaction(&mut self) {
self.transactions.push(Vec::new());
}
fn commit_transaction(&mut self) {
let last = self.transactions.pop().unwrap();
if let Some(tail) = self.transactions.last_mut() {
tail.extend(last);
}
}
fn abort_transaction(&mut self) {
let last = self.transactions.pop().unwrap();
for t in last.into_iter().rev() {
self.reader.unread_token(t);
}
}
}
impl<T> Parser<T> {
pub fn reader(&self) -> &T {
&self.reader
}
pub fn reader_mut(&mut self) -> &mut T {
&mut self.reader
}
pub fn into_reader(self) -> T {
self.reader
}
}
impl Parse for LexicalToken {
fn parse<T>(parser: &mut Parser<T>) -> Result<Self>
where
T: TokenRead,
{
track!(parser.next_token())
}
}