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use super::types::Rule;
use crate::camxes::peg::grammar::{MemoMap, Peg};
use crate::camxes::peg::parsing::{get_furthest_error_pos, get_furthest_pos, limit_error_pos, set_furthest_error_pos, set_furthest_pos, update_furthest_error_pos, update_furthest_pos, ErrorKind, ParseError, ParseNode, ParseResult, Span};
use log::{debug, log_enabled, Level};
use std::sync::Arc;
/// Helper: merge two error positions, keeping the furthest (Pappy's joinErrors).
fn join_error_pos(pos1: usize, pos2: usize) -> usize {
pos1.max(limit_error_pos(pos2))
}
impl Rule {
pub fn parse(&self, peg: &Peg, input: &str, position: usize, depth: usize, memo: &mut MemoMap) -> ParseResult {
match self {
Rule::Empty => ParseResult(1, position, position, Arc::new(Ok(vec![]))),
Rule::Any => {
if position < input.len() {
let new_pos = position + 1;
update_furthest_pos(new_pos);
ParseResult(
1,
new_pos,
position, // error_pos: no error, use current position
Arc::new(Ok(vec![ParseNode::Terminal {
span: Span(position, new_pos),
}])),
)
} else {
update_furthest_error_pos(position);
ParseResult(
1,
position,
limit_error_pos(position), // error_pos: failed at current position
Arc::new(Err(ParseError {
position,
rule_name: self.error_description(),
error: ErrorKind::UnexpectedEndOfInput,
cause: None,
})),
)
}
}
Rule::Literal(pattern) => {
// Fast path: single-byte literal
let matched = if pattern.len() == 1 {
position < input.len() && input.as_bytes()[position] == pattern.as_bytes()[0]
} else {
input[position..].starts_with(pattern)
};
if matched {
let len = pattern.len();
let new_pos = position + len;
update_furthest_pos(new_pos);
ParseResult(
1,
new_pos,
position, // error_pos: no error
Arc::new(Ok(vec![ParseNode::Terminal {
span: Span(position, new_pos),
}])),
)
} else {
update_furthest_error_pos(position);
ParseResult(
1,
position,
limit_error_pos(position), // error_pos: failed at current position
Arc::new(Err(ParseError {
position,
rule_name: self.error_description(),
error: ErrorKind::ExpressionDoesNotMatch,
cause: None,
})),
)
}
}
Rule::NonTerminal(name) => {
let key = (name.clone(), position);
if let Some(cached_result) = memo.get(&key) {
if log_enabled!(Level::Debug) {
debug!(
"{}cache hit {name} @ {position} -> {}",
"│".repeat(depth),
cached_result.1
);
}
return cached_result.clone();
}
if log_enabled!(Level::Debug) {
debug!("{}parsing {name} @ {position}", "│".repeat(depth));
}
let rule = match peg.rules.get(name) {
Some(r) => r,
None => {
let err = ParseError {
position,
rule_name: self.error_description(),
error: ErrorKind::NonTerminalDoesNotExist(name.clone()),
cause: None,
};
let res = ParseResult(1, position, position, Arc::new(Err(err)));
memo.insert(key, res.clone());
return res;
}
};
let result = match rule.parse(peg, input, position, depth + 1, memo) {
ParseResult(cost, new_pos, err_pos, ref payload) => match payload.as_ref() {
Ok(matches) => ParseResult(
cost,
new_pos,
err_pos, // propagate error position from inner parse
Arc::new(Ok(vec![ParseNode::NonTerminal {
name: name.clone(),
span: Span(position, new_pos),
children: matches.clone(),
}])),
),
Err(inner) => ParseResult(
cost,
position,
err_pos, // propagate error position from inner parse
Arc::new(Err(ParseError {
position: limit_error_pos(position),
rule_name: self.error_description(),
error: ErrorKind::NonTerminalDoesNotMatch,
cause: Some(Box::new(inner.clone())),
})),
),
},
};
if log_enabled!(Level::Debug) {
debug!(
"{}└{} {} @ {} -> {}",
"│".repeat(depth),
if result.3.is_ok() { "ok" } else { "err" },
name,
position,
result.1
);
}
memo.insert(key, result.clone());
result
}
Rule::Choice(choices) => {
let mut furthest_err = position;
for choice in choices {
let res = choice.parse(peg, input, position, depth, memo);
furthest_err = join_error_pos(furthest_err, res.2);
if res.3.is_ok() {
// Success: return with merged error position
return ParseResult(1, res.1, furthest_err, res.3);
}
}
// All choices failed: return error with furthest position
ParseResult(
1,
position,
furthest_err,
Arc::new(Err(ParseError {
position: furthest_err,
rule_name: self.error_description(),
error: ErrorKind::ExpressionDoesNotMatch,
cause: None,
})),
)
}
Rule::Sequence(sequence) => {
let mut captures = Vec::with_capacity(sequence.len());
let mut pos = position;
let mut furthest_err = position;
for expr in sequence {
let res = expr.parse(peg, input, pos, depth, memo);
furthest_err = join_error_pos(furthest_err, res.2);
match res.3.as_ref() {
Ok(m) => {
pos = res.1;
captures.extend(m.iter().cloned());
}
Err(e) => {
return ParseResult(1, position, furthest_err, Arc::new(Err(e.clone())));
}
}
}
ParseResult(1, pos, furthest_err, Arc::new(Ok(captures)))
}
Rule::ZeroOrMore(expr) => {
let mut captures = Vec::with_capacity(8);
let mut pos = position;
let mut furthest_err = position;
loop {
let res = expr.parse(peg, input, pos, depth, memo);
furthest_err = join_error_pos(furthest_err, res.2);
match res.3.as_ref() {
Ok(m) => {
// Prevent infinite loop on zero-width matches
if res.1 == pos {
break;
}
pos = res.1;
captures.extend(m.iter().cloned());
}
Err(_) => break,
}
}
ParseResult(1, pos, furthest_err, Arc::new(Ok(captures)))
}
Rule::OneOrMore(expr) => Rule::Sequence(vec![
Rule::Group(expr.clone()),
Rule::ZeroOrMore(expr.clone()),
])
.parse(peg, input, position, depth, memo),
Rule::Optional(expr) => {
let res = expr.parse(peg, input, position, depth, memo);
if res.3.is_ok() {
ParseResult(1, res.1, res.2, res.3)
} else {
// Optional always succeeds; propagate error position from failed attempt
ParseResult(1, position, res.2, Arc::new(Ok(vec![])))
}
}
Rule::And(expr) => {
// Lookahead &(e): succeeds without consuming input.
// Lookaheads are speculative - error positions from inside should not propagate.
// Save and restore both FURTHEST_POS and the error_position.
let saved_furthest = get_furthest_pos();
let saved_furthest_error = get_furthest_error_pos();
let res = expr.parse(peg, input, position, depth, memo);
set_furthest_pos(saved_furthest);
set_furthest_error_pos(saved_furthest_error);
// Use saved_furthest as error_pos (don't propagate inner error_pos)
if res.3.is_ok() {
ParseResult(1, position, saved_furthest, Arc::new(Ok(vec![])))
} else {
let e = res.3.as_ref().clone().err().unwrap();
ParseResult(1, position, saved_furthest, Arc::new(Err(e)))
}
}
Rule::Not(expr) => {
// Lookahead !(e): succeeds without consuming input when inner fails.
// Lookaheads are speculative - error positions from inside should not propagate.
// Save and restore both FURTHEST_POS and the error_position.
let saved_furthest = get_furthest_pos();
let saved_furthest_error = get_furthest_error_pos();
let res = expr.parse(peg, input, position, depth, memo);
set_furthest_pos(saved_furthest);
set_furthest_error_pos(saved_furthest_error);
// Use saved_furthest as error_pos (don't propagate inner error_pos)
match res.3.as_ref() {
Ok(m) => {
// Inner succeeded → Not fails
ParseResult(
1,
position,
saved_furthest,
Arc::new(Err(ParseError {
position: limit_error_pos(position),
rule_name: self.error_description(),
error: ErrorKind::NotDidMatch(m.clone()),
cause: None,
})),
)
}
Err(_) => {
// Inner failed → Not succeeds
ParseResult(1, position, saved_furthest, Arc::new(Ok(vec![])))
}
}
}
Rule::Group(expr) => expr.parse(peg, input, position, depth, memo),
Rule::Range(start, end) => {
if position < input.len() {
let c = input[position..].chars().next().unwrap();
if start.chars().next().unwrap() <= c && c <= end.chars().next().unwrap() {
let new_pos = position + 1;
update_furthest_pos(new_pos);
ParseResult(
1,
new_pos,
position, // no error
Arc::new(Ok(vec![ParseNode::Terminal {
span: Span(position, new_pos),
}])),
)
} else {
update_furthest_error_pos(position);
ParseResult(
1,
position,
limit_error_pos(position), // error at current position
Arc::new(Err(ParseError {
position: limit_error_pos(position),
rule_name: self.error_description(),
error: ErrorKind::ExpressionDoesNotMatch,
cause: None,
})),
)
}
} else {
update_furthest_error_pos(position);
ParseResult(
1,
position,
limit_error_pos(position), // error at current position
Arc::new(Err(ParseError {
position: limit_error_pos(position),
rule_name: self.error_description(),
error: ErrorKind::ExpressionDoesNotMatch,
cause: None,
})),
)
}
}
Rule::Class(symbols) => {
// Longest match first: sort by length descending
let mut syms: Vec<&String> = symbols.iter().collect();
syms.sort_by_key(|b| std::cmp::Reverse(b.len()));
let matched = syms
.into_iter()
.find(|s| input[position..].starts_with(s.as_str()));
if let Some(symbol) = matched {
let len = symbol.len();
let new_pos = position + len;
update_furthest_pos(new_pos);
ParseResult(
1,
new_pos,
position, // no error
Arc::new(Ok(vec![ParseNode::Terminal {
span: Span(position, new_pos),
}])),
)
} else {
update_furthest_error_pos(position);
ParseResult(
1,
position,
limit_error_pos(position), // error at current position
Arc::new(Err(ParseError {
position: limit_error_pos(position),
rule_name: self.error_description(),
error: ErrorKind::ExpressionDoesNotMatch,
cause: None,
})),
)
}
}
}
}
}