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use crate::peg::grammar::PEG;
use crate::peg::parsing::{Capture, ParserError, ParserErrorCode, ParserOutput, Token};
use log::debug;
use std::collections::HashSet;
use std::fmt::{Display, Formatter};
use std::rc::Rc;
// might need inner structs
#[derive(Clone, Debug)]
pub enum Expression {
Empty,
Any,
Literal(String),
NonTerminal(String), // references a rule
Range(String, String),
Class(HashSet<String>),
Group(Rc<Box<Expression>>),
ZeroOrMore(Rc<Box<Expression>>),
OneOrMore(Rc<Box<Expression>>),
Optional(Rc<Box<Expression>>),
And(Rc<Box<Expression>>),
Not(Rc<Box<Expression>>),
Choice(Vec<Expression>), // generalizing it to any number of choices
Sequence(Vec<Expression>), // generalizing it to any number of sequences
}
impl Expression {
pub fn into_rc_box(self) -> Rc<Box<Expression>> {
Rc::new(Box::new(self))
}
pub fn make_class(symbols: &[&str]) -> Expression {
let mut class: HashSet<String> = Default::default();
for s in symbols.iter().map(|c| c.to_string()) {
class.insert(s);
}
Expression::Class(class)
}
pub fn parse(&self, peg: &PEG, input: &str, cursor: usize, depth: usize) -> ParserOutput {
match self {
Expression::Empty => ParserOutput(1, cursor, Ok(vec![])),
Expression::Any => {
if cursor < input.len() {
ParserOutput(
1,
cursor + 1,
Ok(vec![Token::Terminal(Capture(cursor, cursor + 1))]),
)
} else {
ParserOutput(
1,
cursor,
Err(ParserError {
position: cursor,
expression: self.clone(),
error: ParserErrorCode::UnexpectedEndOfInput,
cause: None,
}),
)
}
}
Expression::Literal(pattern) => {
let input = &input[cursor..];
let len = pattern.len();
if input.starts_with(pattern) {
ParserOutput(
len as u32,
cursor + len,
Ok(vec![Token::Terminal(Capture(cursor, cursor + len))]),
)
} else {
// eh, not quite what I wrote above, but close enough (cost is potentially too large)...
ParserOutput(
len as u32,
cursor,
Err(ParserError {
position: cursor,
expression: self.clone(),
error: ParserErrorCode::ExpressionDoesNotMatch,
cause: None,
}),
)
}
}
Expression::NonTerminal(nt) => {
let rule = peg
.rules
.get(nt)
.expect(format!("Encountered unknown NonTerminal symbol: {}", nt).as_str());
debug!("{}parsing {nt} @ {cursor}: {rule}", "│".repeat(depth));
let ParserOutput(cost, new_cursor, res) = rule.parse(peg, input, cursor, depth + 1);
let res = match res {
Ok(matches) => ParserOutput(
cost,
new_cursor,
Ok(vec![Token::NonTerminal(
nt.clone(),
Capture(cursor, new_cursor),
matches,
)]),
),
Err(inner) => ParserOutput(
cost,
cursor,
Err(ParserError {
position: cursor,
expression: self.clone(),
error: ParserErrorCode::NonTerminalDoesNotMatch,
cause: Some(Box::from(inner)),
}),
),
};
debug!(
"{}â””{} parsing {nt} @ {cursor} advanced to {new_cursor}",
"│".repeat(depth),
if res.2.is_ok() { "success" } else { "failure" }
);
res
}
Expression::Range(from, to) => {
// test this!
if (from.as_str()..to.as_str()).contains(&&input[cursor..]) {
// per paper this should have been desugared into a choice and the cost would depend on
// the ordering in the choice, but this can be done in constant time...
ParserOutput(
1,
cursor + 1,
Ok(vec![Token::Terminal(Capture(cursor, cursor + 1))]),
)
} else {
ParserOutput(
1,
cursor,
Err(ParserError {
position: cursor,
expression: self.clone(),
error: ParserErrorCode::ExpressionDoesNotMatch,
cause: None,
}),
)
}
}
Expression::Class(class) => {
let input = &input[cursor..];
let mut cost = 1;
for symbol in class {
cost += symbol.len();
if input.starts_with(symbol) {
return ParserOutput(
cost as u32,
cursor + symbol.len(),
Ok(vec![Token::Terminal(Capture(
cursor,
cursor + symbol.len(),
))]),
);
}
}
ParserOutput(
cost as u32,
cursor,
Err(ParserError {
position: cursor,
expression: self.clone(),
error: ParserErrorCode::ExpressionDoesNotMatch,
cause: None,
}),
)
}
Expression::Group(expression) => {
let ParserOutput(cost, cursor, res) = expression.parse(peg, input, cursor, depth);
ParserOutput(cost + 1, cursor, res)
}
Expression::ZeroOrMore(expression) => {
let mut captures = vec![];
let mut new_cursor = cursor;
let mut running_cost = 1;
loop {
let ParserOutput(cost, downstream_cursor, res) =
expression.parse(peg, input, new_cursor, depth);
running_cost += cost;
match res {
Ok(mut matches) => {
new_cursor = downstream_cursor;
captures.append(&mut matches);
}
Err(_) => {
break ParserOutput(running_cost, new_cursor, Ok(captures));
}
}
}
}
Expression::OneOrMore(expression) => {
let desugared = Expression::Sequence(vec![
Expression::Group(expression.clone()),
Expression::ZeroOrMore(expression.clone()),
]);
desugared.parse(peg, input, cursor, depth)
}
Expression::Optional(expression) => {
let ParserOutput(cost, cursor, res) = expression.parse(peg, input, cursor, depth);
match res {
Ok(matches) => ParserOutput(cost + 1, cursor, Ok(matches)),
Err(_) => ParserOutput(cost + 1, cursor, Ok(vec![])),
}
}
Expression::And(peek) => {
let ParserOutput(cost, _, res) = peek.parse(peg, input, cursor, depth);
match res {
Ok(_) => ParserOutput(cost + 1, cursor, Ok(vec![])),
Err(inner) => ParserOutput(
cost + 1,
cursor,
Err(ParserError {
position: cursor,
expression: self.clone(),
error: ParserErrorCode::ExpressionDoesNotMatch,
cause: Some(Box::from(inner)),
}),
),
}
}
Expression::Not(peek) => {
let ParserOutput(cost, _, res) = peek.parse(peg, input, cursor, depth);
match res {
Ok(inner) => ParserOutput(
cost + 1,
cursor,
Err(ParserError {
position: cursor,
expression: self.clone(),
error: ParserErrorCode::NotDidMatch(inner),
cause: None,
}),
),
Err(_) => ParserOutput(cost + 1, cursor, Ok(vec![])),
}
}
Expression::Choice(choices) => {
let mut running_cost = 1;
for expression in choices {
let ParserOutput(cost, cursor, res) =
expression.parse(peg, input, cursor, depth);
running_cost += cost;
if let Ok(res) = res {
return ParserOutput(running_cost, cursor, Ok(res));
}
}
ParserOutput(
running_cost,
cursor,
Err(ParserError {
position: cursor,
expression: self.clone(),
error: ParserErrorCode::ExpressionDoesNotMatch,
cause: None,
}),
)
}
Expression::Sequence(sequence) => {
let mut running_cost = 1;
let mut captures: Vec<Token> = vec![];
let mut new_cursor = cursor;
for expression in sequence {
let ParserOutput(cost, cursor, res) =
expression.parse(peg, input, new_cursor, depth);
running_cost += cost;
match res {
Ok(mut res) => {
captures.append(&mut res);
new_cursor = cursor;
}
Err(inner) => {
return ParserOutput(
running_cost,
cursor,
Err(ParserError {
position: cursor,
expression: self.clone(),
error: ParserErrorCode::ExpressionDoesNotMatch,
cause: Some(Box::from(inner)),
}),
);
}
}
}
ParserOutput(running_cost, new_cursor, Ok(captures))
}
}
}
}
fn escape_literal(literal: &String) -> String {
literal
.replace("\\", "\\\\")
.replace("\\\\0", "\\0")
.replace("\\\\1", "\\1")
.replace("\\\\2", "\\2")
.replace("\\\\3", "\\3")
.replace("\\\\4", "\\4")
.replace("\\\\5", "\\5")
.replace("\\\\6", "\\6")
.replace("\\\\7", "\\7")
.replace("\\\\8", "\\8")
.replace("\\\\9", "\\9")
.replace("\r", "\\r")
.replace("\t", "\\t")
.replace("\n", "\\n")
}
impl Display for Expression {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
match self {
Expression::Empty => write!(f, "()"),
Expression::Any => write!(f, "."),
Expression::Literal(literal) => {
write!(f, "'{}'", escape_literal(literal).replace("'", "\\'"))
}
Expression::NonTerminal(token) => write!(f, "{}", token),
Expression::Range(a, b) => write!(f, "[{}-{}]", a, b), // there is no way to output [az-x] atm, just a way to parse it
Expression::Class(class) => {
write!(
f,
"[{}]",
class
.iter()
.map(|c| escape_literal(c).replace("[", "\\[").replace("]", "\\]"))
.collect::<Vec<_>>()
.join("")
)
}
Expression::Group(group) => write!(f, "({})", group),
Expression::ZeroOrMore(inner) => write!(f, "{}*", inner),
Expression::OneOrMore(inner) => write!(f, "{}+", inner),
Expression::Optional(inner) => write!(f, "{}?", inner),
Expression::And(inner) => write!(f, "&{}", inner),
Expression::Not(inner) => write!(f, "!{}", inner),
Expression::Choice(choices) => {
if choices.len() > 1 {
write!(
f,
"({})",
choices
.iter()
.map(|c| format!("{}", c))
.collect::<Vec<_>>()
.join(" / ")
)
} else {
write!(
f,
"{}",
choices
.iter()
.map(|c| format!("{}", c))
.collect::<Vec<_>>()
.join(" / ")
)
}
}
Expression::Sequence(sequence) => {
if sequence.len() > 1 {
write!(
f,
"({})",
sequence
.iter()
.map(|c| format!("{}", c))
.collect::<Vec<_>>()
.join(" ")
)
} else {
write!(
f,
"{}",
sequence
.iter()
.map(|c| format!("{}", c))
.collect::<Vec<_>>()
.join(" ")
)
}
}
}
}
}