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use std::borrow::Cow;
use crate::char_buffer::CharBuffer;
use crate::newline_terminated_chars::NewlineTerminatedChars;
use crate::token::{ListDelimiter, Location, Token};
use std::io;
use std::num::ParseIntError;
use std::str::FromStr;
#[derive(Debug, thiserror::Error)]
pub enum Error<'a> {
#[error("i/o error {0}")]
Io(#[from] io::Error),
#[error("unexpected character '{0}' at {1}")]
UnexpectedCharacter(char, Location),
#[error("unterminated literal at {0}")]
UnterminatedLiteral(Location),
#[error("unknown escape sequence '{0}' at {1}")]
UnknownEscapeSequence(char, Location),
#[error("unparsable integer {0} ({1}) at {2}")]
UnparsableInteger(Cow<'a, str>, ParseIntError, Location),
#[error("unparsable decimal {0}.{1} ({2}) at {3}")]
UnparsableDecimal(u128, Cow<'a, str>, ParseIntError, Location),
#[error("empty character literal at {0}")]
EmptyCharacterLiteral(Location),
}
enum Mode {
Whitespace,
TextBody,
TextEscape,
CharacterBody,
CharacterEscape,
Integer,
Decimal(u128),
Ident
}
pub struct Tokeniser<'a> {
bytes: &'a [u8],
char_indexes: NewlineTerminatedChars<'a>,
token: CharBuffer,
mode: Mode,
location: Location,
stashed_char: Option<(usize, char)>,
error: bool
}
impl<'a> Tokeniser<'a> {
#[inline]
pub fn new(str: &'a str) -> Self {
Self {
bytes: str.as_bytes(),
char_indexes: NewlineTerminatedChars::new(str.char_indices()),
token: CharBuffer::default(),
mode: Mode::Whitespace,
location: Location { line: 1, column: 0 },
stashed_char: None,
error: false,
}
}
#[inline(always)]
fn next_char(&mut self) -> Option<(usize, char)> {
match self.stashed_char.take() {
None => self.char_indexes.next(),
Some((index, char)) => Some((index, char))
}
}
}
impl<'a> Iterator for Tokeniser<'a> {
type Item = Result<Token<'a>, Error<'a>>;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
if self.error {
return None;
}
while let Some((index, char)) = self.next_char() {
self.location.column += 1;
match self.mode {
Mode::Whitespace => {
match char {
'\\' => {
self.error = true;
return Some(Err(Error::UnexpectedCharacter(char, self.location.clone())))
}
'"' => {
self.mode = Mode::TextBody;
}
'\'' => {
self.mode = Mode::CharacterBody;
}
'\t' | '\r' | ' ' => {}
'\n' => {
self.location.line += 1;
self.location.column = 1;
return Some(Ok(Token::Newline))
}
'(' => {
return Some(Ok(Token::Left(ListDelimiter::Paren)));
}
')' => {
return Some(Ok(Token::Right(ListDelimiter::Paren)));
}
'{' => {
return Some(Ok(Token::Left(ListDelimiter::Brace)));
}
'}' => {
return Some(Ok(Token::Right(ListDelimiter::Brace)));
}
'[' => {
return Some(Ok(Token::Left(ListDelimiter::Bracket)));
}
']' => {
return Some(Ok(Token::Right(ListDelimiter::Bracket)));
}
'-' => {
return Some(Ok(Token::Dash));
}
':' => {
return Some(Ok(Token::Colon));
}
',' => {
return Some(Ok(Token::Comma));
}
'0'..='9' => {
self.mode = Mode::Integer;
self.token.push(index, char);
}
'.' => {
self.mode = Mode::Decimal(0);
}
_ => {
self.mode = Mode::Ident;
self.token.push(index, char);
}
}
}
Mode::TextBody => {
match char {
'\\' => {
self.token.copy(self.bytes);
self.mode = Mode::TextEscape;
}
'"' => {
let token = Token::Text(self.token.string(self.bytes));
self.token.clear();
self.mode = Mode::Whitespace;
return Some(Ok(token))
}
'\n' => {
self.error = true;
return Some(Err(Error::UnterminatedLiteral(self.location.clone())))
}
_ => {
self.token.push(index, char);
}
}
}
Mode::CharacterEscape | Mode::TextEscape => {
match char {
'\\' | '"' | '\'' => {
self.token.push(0, char);
}
'n' => {
self.token.push(0, '\n');
}
'r' => {
self.token.push(0, '\r');
}
't' => {
self.token.push(0, '\t');
}
'x' => {
//TODO handle hex (e.g., \x7F)
self.error = true;
return Some(Err(Error::UnknownEscapeSequence(char, self.location.clone())))
}
'u' => {
//TODO handle unicode (e.g., \u{7FFF})
self.error = true;
return Some(Err(Error::UnknownEscapeSequence(char, self.location.clone())))
}
_ => {
self.error = true;
return Some(Err(Error::UnknownEscapeSequence(char, self.location.clone())))
}
}
match self.mode {
Mode::TextEscape => {
self.mode = Mode::TextBody;
}
Mode::CharacterEscape => {
self.mode = Mode::CharacterBody;
}
_ => {
// by the encompassing pattern, mode must be one of the two variants above
unreachable!()
}
}
}
Mode::CharacterBody => {
match char {
'\\' => {
self.mode = Mode::CharacterEscape;
self.token.copy(self.bytes);
}
'\'' => {
let mut chars = self.token.as_str(self.bytes).chars();
return match chars.next() {
None => {
self.error = true;
Some(Err(Error::EmptyCharacterLiteral(self.location.clone())))
}
Some(first_char) => {
let token = Token::Character(first_char);
self.token.clear();
self.mode = Mode::Whitespace;
Some(Ok(token))
}
}
}
'\n' => {
self.error = true;
return Some(Err(Error::UnterminatedLiteral(self.location.clone())))
}
_ => {
if self.token.is_empty() {
self.token.push(index, char);
} else {
self.error = true;
return Some(Err(Error::UnexpectedCharacter(char, self.location.clone())))
}
}
}
}
Mode::Integer => {
match char {
'_' => {
self.token.copy(self.bytes);
}
'.' => {
let str = self.token.as_str(self.bytes);
match u128::from_str(str) {
Ok(int) => {
self.mode = Mode::Decimal(int);
self.token.clear()
}
Err(err) => {
self.error = true;
return Some(Err(Error::UnparsableInteger(self.token.string(self.bytes), err, self.location.clone())))
}
}
}
')' | ']' | '}' | ':' | '-' | ',' | '\n' | '\t' | '\r' | ' ' => {
let str = self.token.as_str(self.bytes);
return match u128::from_str(str) {
Ok(whole) => {
let token = Token::Integer(whole);
self.token.clear();
self.mode = Mode::Whitespace;
self.stashed_char = Some((index, char)); // don't consume the char
self.location.column -= 1;
Some(Ok(token))
}
Err(err) => {
Some(Err(Error::UnparsableInteger(self.token.string(self.bytes), err, self.location.clone())))
}
}
}
_ => {
self.token.push(index, char);
}
}
}
Mode::Decimal(whole) => {
match char {
'_' => {
self.token.copy(self.bytes);
}
')' | ']' | '}' | ':' | '-' | ',' | '\n' | '\t' | '\r' | ' ' => {
let str = self.token.as_str(self.bytes);
return match u128::from_str(str) {
Ok(fractional) => {
let token = Token::Decimal(whole, fractional, self.token.len().try_into().expect("fractional part is too long"));
self.token.clear();
self.mode = Mode::Whitespace;
self.stashed_char = Some((index, char)); // don't consume the char
self.location.column -= 1;
Some(Ok(token))
}
Err(err) => {
Some(Err(Error::UnparsableDecimal(whole, self.token.string(self.bytes), err, self.location.clone())))
}
}
}
_ => {
self.token.push(index, char);
}
}
}
Mode::Ident => {
match char {
')' | ']' | '}' | ':' | '-' | ',' | '\n' | '\t' | '\r' | ' ' => {
let str = self.token.as_str(self.bytes);
let token = match str {
"true" => {
Token::Boolean(true)
}
"false" => {
Token::Boolean(false)
}
_ => {
Token::Ident(self.token.string(self.bytes))
}
};
self.token.clear();
self.mode = Mode::Whitespace;
self.stashed_char = Some((index, char)); // don't consume the char
self.location.column -= 1;
return Some(Ok(token))
}
_ => {
self.token.push(index, char);
}
}
}
}
}
None
}
}
#[cfg(test)]
mod tests;