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use std::collections::HashMap;
use crate::lexer::{Token, TokenPos};
use crate::json::{*, self};
pub struct Parser {
/// Array of lexed tokens
tokens: Vec<TokenPos>,
/// Current token
pos: usize,
}
impl From<Vec<TokenPos>> for Parser {
fn from(tokens: Vec<TokenPos>) -> Self {
Self {
tokens,
pos: 0,
}
}
}
impl Parser {
#[inline]
fn curr(&self) -> Token {
self.tokens[self.pos].0.clone()
}
#[inline]
fn advance(&mut self, len: usize) {
self.pos += len;
}
fn expect(&mut self, expected: Token) -> json::Result<()> {
if self.curr() == expected {
self.pos += 1;
Ok(())
} else {
Err(JSONError::ParseError(format!("expected {:?}, found {:?}", expected, self.curr())))
}
}
/// Parse tokens in current
pub fn parse(&mut self) -> json::Result<JSONValue> {
let (line, column) = (self.tokens[self.pos].1, self.tokens[self.pos].2);
match self.curr().clone() {
Token::OpenBrace => {
// begin object
let mut ret: HashMap<String, JSONValue> = HashMap::new();
self.advance(1);
// catches the case of an empty object
if self.curr() == Token::CloseBrace {
return Ok(JSONValue::Object(ret))
}
// while last character is a comma
loop {
// expect a string literal as a key
let key = match self.curr().clone() {
// chops off the quotations
Token::StringLiteral(val) => val[1..val.len() - 1].to_owned(),
_ => return Err(JSONError::ParseError(format!("expected string literal at line {line}, column {column}"))),
};
self.advance(1);
// expect a colon
self.expect(Token::Colon)?;
// expect a JSONValue
let val = self.parse()?;
self.advance(1);
ret.insert(key, val);
if self.curr() == Token::CloseBrace {
break;
}
self.expect(Token::Comma)?;
}
Ok(JSONValue::Object(ret))
},
Token::CloseBrace => {
Err(JSONError::ParseError(format!("unexpected token `CloseBrace` at line {line}, column {column}")))
},
Token::OpenBracket => {
// begin array
let mut ret: Vec<JSONValue> = vec![];
// parse next token continuously, until the end of the array is reached
self.pos += 1;
// catch the case of an empty array
if self.curr() == Token::CloseBracket {
return Ok(JSONValue::Array(ret));
}
loop {
ret.push(self.parse()?);
// moves us off of value
self.pos += 1;
// if we're at the end of the array...
if self.curr() == Token::CloseBracket {
break;
}
self.expect(Token::Comma)?;
}
Ok(JSONValue::Array(ret))
},
Token::CloseBracket => {
Err(JSONError::ParseError(format!("unexpected token `CloseBracket` at line {line}, column {column}")))
},
Token::Colon => {
Err(JSONError::ParseError(format!("unexpected token `Colon` at line {line}, column {column}")))
},
Token::Comma => {
Err(JSONError::ParseError(format!("unexpected token `Comma` at line {line}, column {column}")))
},
Token::StringLiteral(val) => {
// begin string
// StringLiteral includes the '"' characters; filter those off
let trimmed = val[1..val.len() - 1].to_owned();
let t_iter: Vec<char> = trimmed.chars().collect();
let mut formatted: Vec<char> = vec![];
let mut i = 0;
while i < t_iter.len() {
if t_iter[i] == '\\' {
formatted.push(match t_iter[i+1] {
'"' => '"',
'\\' => '\\',
'/' => '/',
'b' => '\u{0008}',
'f' => '\u{000c}',
'n' => '\u{000a}',
'r' => '\u{000d}',
't' => '\u{0009}',
'u' => {
let chars: String = t_iter[i+2..i+6].iter().collect();
let num = u16::from_str_radix(&chars, 16)
.or(Err(JSONError::ValueError(format!("invalid hexadecimal code: {}", chars))))? as u32;
i += 4;
match char::from_u32(num) {
Some(v) => v,
None => return Err(JSONError::ValueError(format!("invalid utf16 hexadecimal code: {}", &chars)))
}
}
_ => return Err(JSONError::ValueError(format!("invalid escape char: {}", t_iter[i+1])))
});
i += 1;
} else {
formatted.push(t_iter[i]);
}
i += 1;
}
Ok(JSONValue::String(String::from_utf8(formatted.iter().map(|c| *c as u8).collect()).unwrap()))
},
Token::NumericLiteral(val) => {
// begin number
Ok(JSONValue::Number(val.parse().unwrap()))
},
Token::True => {
Ok(JSONValue::Bool(true))
},
Token::False => {
Ok(JSONValue::Bool(false))
},
Token::Null => {
Ok(JSONValue::Null)
}
Token::Unknown(text) => {
Err(JSONError::ParseError(format!("unexpected token `{text}` at line {line}, column {column}")))
}
}
}
}