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//! Condition and goal parsing.
use crate::ast::{AtomicFormula, Condition};
use crate::error::ParseError;
use crate::lexer::TokenKind;
use super::cursor::Parser;
use super::expr::{is_numeric_start, parse_numeric_expr};
use super::terms::{parse_term, parse_typed_list_vars};
use super::utils::{parse_compare_op_from_str, parse_number_literal};
/// Parse a PDDL condition/goal description. Handles logical connectives, quantifiers, temporal
/// wrappers (`at start`/`at end`/`over all`), predicates (disambiguating `at` and `over` from
/// temporal keywords), numeric comparisons, equality, preferences, and PDDL3 trajectory constraints.
pub(super) fn parse_condition(p: &mut Parser) -> Result<Condition, ParseError> {
if p.at_lparen() {
p.expect_lparen()?;
let tok = p
.peek()
.ok_or_else(|| ParseError::new("unexpected end of input in condition", p.eof_span()))?;
match &tok.kind {
TokenKind::Symbol(s) => {
let s = s.clone();
match s.as_str() {
"and" => {
p.advance()?;
let mut conds = Vec::new();
while !p.at_rparen() {
conds.push(parse_condition(p)?);
}
p.expect_rparen()?;
return Ok(Condition::And(conds));
}
"or" => {
p.advance()?;
let mut conds = Vec::new();
while !p.at_rparen() {
conds.push(parse_condition(p)?);
}
p.expect_rparen()?;
return Ok(Condition::Or(conds));
}
"not" => {
p.advance()?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::Not(Box::new(inner)));
}
"imply" => {
p.advance()?;
let a = parse_condition(p)?;
let b = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::Imply(Box::new(a), Box::new(b)));
}
"forall" => {
p.advance()?;
p.expect_lparen()?;
let variables = parse_typed_list_vars(p)?;
p.expect_rparen()?;
let condition = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::Forall {
variables,
condition: Box::new(condition),
});
}
"exists" => {
p.advance()?;
p.expect_lparen()?;
let variables = parse_typed_list_vars(p)?;
p.expect_rparen()?;
let condition = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::Exists {
variables,
condition: Box::new(condition),
});
}
"preference" => {
p.advance()?;
// Optional name
let name = if !p.at_lparen() && !p.at_rparen() {
Some(p.expect_symbol()?)
} else {
None
};
let condition = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::Preference {
name,
condition: Box::new(condition),
});
}
"at" => {
p.advance()?;
let tok2 = p.peek().ok_or_else(|| {
ParseError::new("unexpected end after 'at'", p.eof_span())
})?;
if tok2.symbol_eq("start") {
p.advance()?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::AtStart(Box::new(inner)));
} else if tok2.symbol_eq("end") {
p.advance()?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::AtEnd(Box::new(inner)));
} else {
// `at` is a regular predicate name, e.g. (at ?truck ?loc)
let mut args = Vec::new();
while !p.at_rparen() {
args.push(parse_term(p)?);
}
p.expect_rparen()?;
return Ok(Condition::Predicate(AtomicFormula { name: s, args }));
}
}
"over" => {
p.advance()?;
let next = p.peek().ok_or_else(|| {
ParseError::new("unexpected end after 'over'", p.eof_span())
})?;
if next.symbol_eq("all") {
p.advance()?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::OverAll(Box::new(inner)));
} else {
// `over` is a regular predicate name
let mut args = Vec::new();
while !p.at_rparen() {
args.push(parse_term(p)?);
}
p.expect_rparen()?;
return Ok(Condition::Predicate(AtomicFormula { name: s, args }));
}
}
"always" => {
p.advance()?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::Always(Box::new(inner)));
}
"sometime" => {
p.advance()?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::Sometime(Box::new(inner)));
}
"at-most-once" => {
p.advance()?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::AtMostOnce(Box::new(inner)));
}
"within" => {
p.advance()?;
let t = parse_number_literal(p)?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::Within(t, Box::new(inner)));
}
"sometime-before" => {
p.advance()?;
let a = parse_condition(p)?;
let b = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::SometimeBefore(Box::new(a), Box::new(b)));
}
"sometime-after" => {
p.advance()?;
let a = parse_condition(p)?;
let b = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::SometimeAfter(Box::new(a), Box::new(b)));
}
"always-within" => {
p.advance()?;
let t = parse_number_literal(p)?;
let a = parse_condition(p)?;
let b = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::AlwaysWithin(t, Box::new(a), Box::new(b)));
}
"hold-during" => {
p.advance()?;
let t1 = parse_number_literal(p)?;
let t2 = parse_number_literal(p)?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::HoldDuring(t1, t2, Box::new(inner)));
}
"hold-after" => {
p.advance()?;
let t = parse_number_literal(p)?;
let inner = parse_condition(p)?;
p.expect_rparen()?;
return Ok(Condition::HoldAfter(t, Box::new(inner)));
}
"=" => {
p.advance()?;
// Could be equality of terms or numeric comparison
// Peek ahead: if next is '(' or a number, it's numeric
if is_numeric_start(p) {
let left = parse_numeric_expr(p)?;
let right = parse_numeric_expr(p)?;
p.expect_rparen()?;
return Ok(Condition::NumericComparison {
op: crate::ast::CompareOp::Eq,
left,
right,
});
}
let a = parse_term(p)?;
let b = parse_term(p)?;
p.expect_rparen()?;
return Ok(Condition::Equals(a, b));
}
"<" | "<=" | ">" | ">=" => {
let op = parse_compare_op_from_str(&s);
p.advance()?;
let left = parse_numeric_expr(p)?;
let right = parse_numeric_expr(p)?;
p.expect_rparen()?;
return Ok(Condition::NumericComparison { op, left, right });
}
_ => {
// Predicate application: (name term*)
p.advance()?;
let mut args = Vec::new();
while !p.at_rparen() {
args.push(parse_term(p)?);
}
p.expect_rparen()?;
return Ok(Condition::Predicate(AtomicFormula { name: s, args }));
}
}
}
_ => {
return Err(ParseError::new(
format!("unexpected token in condition: {:?}", tok.kind),
tok.span,
));
}
}
}
Err(ParseError::new(
"expected condition (must start with '(')",
p.current_span(),
))
}
#[cfg(test)]
mod tests {
use super::*;
use crate::ast::{CompareOp, Term};
use crate::lexer::tokenize;
fn parse(input: &str) -> Result<Condition, ParseError> {
let tokens = tokenize(input)?;
let mut parser = Parser::new(&tokens);
parse_condition(&mut parser)
}
#[test]
fn parses_named_preference_and_temporal_conditions() {
let condition =
parse("(and (preference prefer-ready (ready a)) (at end (done a)))").unwrap();
let Condition::And(conditions) = condition else {
return;
};
assert!(matches!(
&conditions[0],
Condition::Preference {
name: Some(name),
..
} if name == "prefer-ready"
));
assert!(matches!(&conditions[1], Condition::AtEnd(_)));
}
#[test]
fn parses_all_numeric_comparison_operators() {
for (input, expected) in [
("(< (cost) 5)", CompareOp::Lt),
("(<= (cost) 5)", CompareOp::Lte),
("(> (cost) 5)", CompareOp::Gt),
("(>= (cost) 5)", CompareOp::Gte),
] {
let condition = parse(input).unwrap();
assert!(matches!(
condition,
Condition::NumericComparison { op, .. } if op == expected
));
}
}
#[test]
fn parses_term_equality_with_variables() {
let condition = parse("(= ?x target)").unwrap();
assert!(matches!(
condition,
Condition::Equals(Term::Variable(variable), Term::Name(name))
if variable == "?x" && name == "target"
));
}
#[test]
fn reports_condition_edge_errors() {
for input in [
"(",
"(and (ready a)",
"(preference name)",
"(at",
"(over",
"(<=)",
"(ready 1)",
"ready",
] {
assert!(parse(input).is_err(), "{input}");
}
}
}