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use crate::lexer::Token;
pub struct Parser {
tokens: Vec<Token>,
pos: usize,
}
impl Parser {
pub fn new(tokens: Vec<Token>) -> Self {
Self { tokens, pos: 0 }
}
fn current(&self) -> Token {
self.tokens
.get(self.pos)
.cloned()
.unwrap_or(Token::Eof)
}
fn peek(&self) -> Token {
self.tokens
.get(self.pos + 1)
.cloned()
.unwrap_or(Token::Eof)
}
fn advance(&mut self) {
if self.pos < self.tokens.len() {
self.pos += 1;
}
}
fn expect(&mut self, expected: Token) -> hyperkitty_core::Result<()> {
if std::mem::discriminant(&self.current()) == std::mem::discriminant(&expected) {
self.advance();
Ok(())
} else {
Err(hyperkitty_core::Error::SyntaxError(
format!("Expected {:?}, got {:?}", expected, self.current())
))
}
}
pub fn parse(&mut self) -> hyperkitty_core::Result<ConstraintProgram> {
let mut program = ConstraintProgram::new();
while self.current() != Token::Eof {
let constraint = self.parse_constraint()?;
program.add_constraint(constraint);
}
Ok(program)
}
fn parse_constraint(&mut self) -> hyperkitty_core::Result<Constraint> {
self.expect(Token::Validity)?;
// Parse name: identifier in parentheses
self.expect(Token::LParen)?;
let name = match self.current() {
Token::Ident(s) => {
let n = s.clone();
self.advance();
n
}
_ => return Err(hyperkitty_core::Error::SyntaxError("Expected constraint name".to_string())),
};
self.expect(Token::RParen)?;
// Parse parameter: usually a variable name or message
let param = match self.current() {
Token::Ident(s) => {
let p = s.clone();
self.advance();
p
}
Token::String(s) => {
let p = s.clone();
self.advance();
p
}
_ => {
return Err(hyperkitty_core::Error::SyntaxError("Expected constraint parameter".to_string()));
}
};
// Parse body: { require ...; otherwise ... }
self.expect(Token::LBrace)?;
let mut constraint = Constraint::new(name, param, OtherwiseAction::Reject);
// Parse require statements
while self.current() != Token::Otherwise && self.current() != Token::RBrace {
self.expect(Token::Require)?;
let req = self.parse_requirement()?;
constraint.add_requirement(req);
self.expect(Token::Semicolon)?;
}
// Parse otherwise clause
if self.current() == Token::Otherwise {
self.advance();
let action = match self.current() {
Token::Reject => {
self.advance();
OtherwiseAction::Reject
}
Token::Accept => {
self.advance();
OtherwiseAction::Accept
}
_ => return Err(hyperkitty_core::Error::SyntaxError(
"Expected 'reject' or 'accept' after 'otherwise'".to_string()
)),
};
constraint.otherwise = action;
self.expect(Token::Semicolon)?;
}
self.expect(Token::RBrace)?;
Ok(constraint)
}
fn parse_requirement(&mut self) -> hyperkitty_core::Result<Requirement> {
match self.current() {
Token::Ident(s) => {
let name = s.clone();
self.advance();
// Check if this is a check() call or simple predicate
if self.current() == Token::LParen {
self.advance();
self.expect(Token::RParen)?;
Ok(Requirement::Check(name))
} else {
Ok(Requirement::Predicate(name))
}
}
_ => Err(hyperkitty_core::Error::SyntaxError(
"Expected requirement predicate or check".to_string()
)),
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::lexer::Lexer;
fn lex(source: &str) -> hyperkitty_core::Result<Vec<Token>> {
let mut lexer = Lexer::new(source);
lexer.tokenize()
}
#[test]
fn test_parse_simple_constraint() -> hyperkitty_core::Result<()> {
let source = r#"validity(V1) msg { require always_true(); otherwise reject; }"#;
let tokens = lex(source)?;
let mut parser = Parser::new(tokens);
let program = parser.parse()?;
assert_eq!(program.constraints.len(), 1);
assert_eq!(program.constraints[0].name, "V1");
Ok(())
}
#[test]
fn test_parse_multiple_constraints() -> hyperkitty_core::Result<()> {
let source = r#"
validity(V1) msg1 { require p1(); otherwise reject; }
validity(V2) msg2 { require p2(); otherwise accept; }
"#;
let tokens = lex(source)?;
let mut parser = Parser::new(tokens);
let program = parser.parse()?;
assert_eq!(program.constraints.len(), 2);
assert_eq!(program.constraints[0].otherwise, OtherwiseAction::Reject);
assert_eq!(program.constraints[1].otherwise, OtherwiseAction::Accept);
Ok(())
}
#[test]
fn test_parse_multiple_requirements() -> hyperkitty_core::Result<()> {
let source = r#"validity(V) msg {
require p1();
require p2();
require p3();
otherwise reject;
}"#;
let tokens = lex(source)?;
let mut parser = Parser::new(tokens);
let program = parser.parse()?;
assert_eq!(program.constraints[0].requires.len(), 3);
Ok(())
}
#[test]
fn test_parse_string_parameter() -> hyperkitty_core::Result<()> {
let source = r#"validity(V) "error message" { require p(); otherwise reject; }"#;
let tokens = lex(source)?;
let mut parser = Parser::new(tokens);
let program = parser.parse()?;
assert_eq!(program.constraints[0].param, "error message");
Ok(())
}
#[test]
fn test_parse_requirement_variations() -> hyperkitty_core::Result<()> {
let source = r#"validity(V) msg {
require check1();
require check2();
otherwise reject;
}"#;
let tokens = lex(source)?;
let mut parser = Parser::new(tokens);
let program = parser.parse()?;
let reqs = &program.constraints[0].requires;
assert_eq!(reqs.len(), 2);
match &reqs[0] {
Requirement::Check(name) => assert_eq!(name, "check1"),
_ => panic!("Expected Check requirement"),
}
Ok(())
}
}
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