mod tests;

use crate::ast::{Node, Token};

fn compute(operator: Token, lhs: bool, rhs: bool) -> bool {
    match operator {
        Token::Negation => !lhs,
        Token::Conjunction => lhs & rhs,
        Token::Disjunction => lhs | rhs,
        Token::ExclusiveDisjunction => lhs ^ rhs,
        Token::MaterialCondition => !(lhs && !rhs),
        Token::LogicalEquivalence => lhs == rhs,
    }
}

fn evaluate(tree: Node<bool>) -> bool {
    match tree {
        Node::Unary { operator, operand } => compute(operator, evaluate(*operand), false),
        Node::Binary { operator, lhs, rhs } => compute(operator, evaluate(*lhs), evaluate(*rhs)),
        Node::Leaf(b) => b,
    }
}

pub fn eval_formula(formula: &str) -> bool {
    let tree = Node::<bool>::parse_formula(formula);
    evaluate(tree)
}