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use crate::token::{keywords, Token};
use alloc::{str::Chars, string::String};
use core::{
iter::{Enumerate, Peekable},
num::ParseFloatError,
};
pub struct Scanner<'a> {
iterator: Peekable<Enumerate<Chars<'a>>>,
line: usize,
line_start_byte: usize,
token_num: usize,
}
impl<'a> Iterator for Scanner<'a> {
type Item = Result<Token, ScanError>;
fn next(&mut self) -> Option<Self::Item> {
while let Some((_, chr)) = self.iterator.peek() {
if *chr == ' ' || *chr == '\t' {
self.iterator.next(); // Ignore tabs and whitespace
} else if let Some((n, '\n')) = self.iterator.peek() {
self.line += 1;
self.line_start_byte = *n;
self.iterator.next();
} else {
break;
}
}
let token = if let Some((byte, string)) = self.iterator.next() {
match string {
'(' => Token::LeftParen,
')' => Token::RightParen,
'{' => Token::LeftBrace,
'}' => Token::RightBrace,
',' => Token::Comma,
'.' => Token::Dot,
'-' => Token::Minus,
'+' => Token::Plus,
';' => Token::Semicolon,
'*' => Token::Star,
'!' => {
if let Some((_, '=')) = self.iterator.peek() {
self.iterator.next();
Token::BangEqual
} else {
Token::Bang
}
}
'=' => {
if let Some((_, '=')) = self.iterator.peek() {
self.iterator.next();
Token::EqualEqual
} else {
Token::Equal
}
}
'<' => {
if let Some((_, '=')) = self.iterator.peek() {
self.iterator.next();
Token::LessEqual
} else {
Token::Less
}
}
'>' => {
if let Some((_, '=')) = self.iterator.peek() {
self.iterator.next();
Token::GreaterEqual
} else {
Token::Greater
}
}
'/' => {
if let Some((_, '/')) = self.iterator.peek() {
self.iterator.next();
// Ignore everything after double slashes (comment)
while self.iterator.next_if(|c| c.1 != '\n').is_some() {}
// Recursively call into the function to see what the next token is after
// the comment.
return self.next();
//TODO: Check to see if a long list of comments can overflow the stack due
//to this recursive call.
} else {
Token::Slash
}
}
'"' => {
let mut string_literal = String::from("");
loop {
if let Some((_, char)) = self.iterator.next() {
if char == '"' {
break;
} else {
string_literal = [string_literal, char.into()].concat();
}
} else {
return Some(Err(ScanError::UnterminatedString {
line_str: string_literal,
line_index: self.line,
col_index: byte - self.line_start_byte,
}));
}
}
Token::String(string_literal)
}
other_char => {
if other_char.is_numeric() {
match self.num_literal(other_char, byte) {
Ok(value) => value,
Err(value) => return value,
}
} else if other_char.is_alphabetic() {
let mut identifier = String::from(other_char);
while let Some((_, next_char)) = self.iterator.peek() {
if next_char.is_alphanumeric() {
identifier.push(*next_char);
self.iterator.next();
} else {
break;
}
}
if let Some(keyword) = keywords(&identifier) {
keyword.clone()
} else {
Token::Identifier(identifier)
}
} else {
return Some(Err(ScanError::UnexpectedChar {
char: other_char.into(),
line_index: self.line,
col_index: byte - self.line_start_byte,
}));
}
}
}
} else {
return None;
};
self.token_num += 1;
Some(Ok(token))
}
}
impl<'a> Scanner<'a> {
pub fn scan_all(&mut self) -> Result<Vec<Token>, (Vec<Token>, Vec<ScanError>)> {
let mut tokens = Vec::new();
let mut errors = Vec::new();
for result in self {
match result {
Ok(token) => tokens.push(token),
Err(error) => errors.push(error),
}
}
if errors.is_empty() {
Ok(tokens)
} else {
Err((tokens, errors))
}
}
pub fn peek(&mut self) -> Option<&(usize, char)> {
self.iterator.peek()
}
/// Get a reference to the scanner's line.
pub fn line(&self) -> &usize {
&self.line
}
/// Get a reference to the scanner's line start byte.
pub fn line_start_byte(&self) -> &usize {
&self.line_start_byte
}
fn num_literal(
&mut self,
other_char: char,
byte: usize,
) -> Result<Token, Option<Result<Token, ScanError>>> {
let mut number_literal = String::from(other_char);
'outer: while let Some((_, next_char)) = self.iterator.peek() {
if next_char.is_numeric() {
number_literal.push(other_char);
self.iterator.next(); // Collect integer part
} else if *next_char == '.' {
number_literal.push(other_char);
self.iterator.next(); // Collect the decimal
while let Some((_, next_next_char)) = self.iterator.peek() {
if next_next_char.is_numeric() {
number_literal.push(other_char);
self.iterator.next(); // Collect the fractional part
} else {
break 'outer;
}
}
} else {
break;
}
}
Ok(match number_literal.parse() {
Ok(num) => {
let number: f64 = num;
Token::Number(number)
}
Err(e) => {
return Err(Some(Err(ScanError::NumberLiteralParse {
parse_err: e,
number: number_literal,
line_index: self.line,
col_index: byte - self.line_start_byte,
})));
}
})
}
}
impl<'a> From<&'a String> for Scanner<'a> {
fn from(source: &'a String) -> Self {
Scanner {
iterator: source.chars().enumerate().peekable(),
line: 1,
line_start_byte: 0,
token_num: 0,
}
}
}
#[derive(Debug, Clone)]
pub enum ScanError {
UnexpectedChar {
char: String,
line_index: usize,
col_index: usize,
},
UnterminatedString {
line_str: String,
line_index: usize,
col_index: usize,
},
NumberLiteralParse {
parse_err: ParseFloatError,
number: String,
line_index: usize,
col_index: usize,
},
}