tnt 1.0.2

Simple runtime validated proofs in number theory
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use pest::{iterators::Pair, Parser};

use crate::{Formula, Term};

#[derive(Parser)]
#[grammar = "parsing\\tnt.pest"]
pub struct TntParser;

// fn print_parse_tree(text: &str, rule: Rule) -> Result<(), pest::error::Error<Rule>> {
//     let tree = TntParser::parse(rule, text)?;
//     println!("{:#?}", tree);
//     Ok(())
// }

pub fn string_to_formula(text: &str) -> Result<Formula, pest::error::Error<Rule>> {
    let mut tree = TntParser::parse(Rule::formula, text)?;
    Ok(build_formula_tree(tree.next().unwrap()))
}

pub fn string_to_term(text: &str) -> Result<Term, pest::error::Error<Rule>> {
    let mut tree = TntParser::parse(Rule::term, text)?;
    Ok(build_term_tree(tree.next().unwrap()))
}

pub fn build_term_tree(pair: Pair<Rule>) -> Term {
    match pair.as_rule() {
        Rule::zero => Term::Zero,
        Rule::variable => Term::var(pair.as_str()),
        Rule::multiplication => {
            let mut t = pair.into_inner();
            let lhs = t.next().unwrap();
            let rhs = t.next().unwrap();
            Term::prod(&build_term_tree(lhs), &build_term_tree(rhs))
        }
        Rule::addition => {
            let mut t = pair.into_inner();
            let lhs = t.next().unwrap();
            let rhs = t.next().unwrap();
            Term::sum(&build_term_tree(lhs), &build_term_tree(rhs))
        }
        Rule::successor => {
            let mut t = pair.into_inner();
            let term = t.next().unwrap();
            Term::succ(&build_term_tree(term))
        }
        _ => unreachable!("input to build_term_tree was not a term"),
    }
}

pub fn build_formula_tree(pair: Pair<Rule>) -> Formula {
    match pair.as_rule() {
        Rule::existential => {
            let mut t = pair.into_inner();
            let v = t.next().unwrap();
            let form = t.next().unwrap();
            Formula::exists(v.as_str().to_owned(), &build_formula_tree(form))
        }
        Rule::universal => {
            let mut t = pair.into_inner();
            let v = t.next().unwrap();
            let form = t.next().unwrap();
            Formula::forall(v.as_str().to_owned(), &build_formula_tree(form))
        }
        Rule::equality => {
            let mut t = pair.into_inner();
            let lhs = t.next().unwrap();
            let rhs = t.next().unwrap();
            Formula::eq(&build_term_tree(lhs), &build_term_tree(rhs))
        }
        Rule::and => {
            let mut t = pair.into_inner();
            let lhs = t.next().unwrap();
            let rhs = t.next().unwrap();
            Formula::and(&build_formula_tree(lhs), &build_formula_tree(rhs))
        }
        Rule::or => {
            let mut t = pair.into_inner();
            let lhs = t.next().unwrap();
            let rhs = t.next().unwrap();
            Formula::or(&build_formula_tree(lhs), &build_formula_tree(rhs))
        }
        Rule::implies => {
            let mut t = pair.into_inner();
            let lhs = t.next().unwrap();
            let rhs = t.next().unwrap();
            Formula::implies(&build_formula_tree(lhs), &build_formula_tree(rhs))
        }
        Rule::negation => {
            let mut t = pair.into_inner();
            let form = t.next().unwrap();
            Formula::not(&build_formula_tree(form))
        }
        _ => unreachable!("input to build_formula_tree was not a formula"),
    }
}

#[cfg(test)]
mod test_expressions {

    use super::*;

    #[test]
    fn test_addition() {
        let tnt = "(0+Sa)";
        let ast = string_to_term(tnt).unwrap();
        assert_eq!(tnt, format!("{}", &ast));
    }

    #[test]
    fn test_multiplication() {
        let tnt = "(x''*SSSSSS0)";
        let ast = string_to_term(tnt).unwrap();
        assert_eq!(tnt, format!("{}", &ast));
    }

    #[test]
    fn test_complex_arithmetic() {
        let tnt = "SS((b+S0)*Sa'')";
        let ast = string_to_term(tnt).unwrap();
        assert_eq!(tnt, format!("{}", &ast));
    }
}

#[cfg(test)]
mod test_formulas {

    use super::*;

    #[test]
    fn test_simple_equality() {
        let tnt = "S0=a''";
        let ast = string_to_formula(tnt).unwrap();
        assert_eq!(tnt, format!("{}", &ast));
    }

    #[test]
    fn test_compound_equality() {
        let tnt = "S0=(b+b)";
        let ast = string_to_formula(tnt).unwrap();
        assert_eq!(tnt, format!("{}", &ast));
    }

    #[test]
    fn test_quantification() {
        let tnt = "~~Ea':z=a";
        let ast = string_to_formula(tnt).unwrap();
        assert_eq!(tnt, format!("{}", &ast));
    }

    #[test]
    fn test_complex_formula() {
        let tnt = "Aa:Ab:(a*Sb)=((a*b)+a)";
        let ast = string_to_formula(tnt).unwrap();
        assert_eq!(tnt, format!("{}", &ast));
    }

    #[test]
    fn test_very_complex_formula() {
        let tnt = "Aa:[Ec:(a*c)=b>Ed:(d*SS0)=a]";
        let ast = string_to_formula(tnt).unwrap();
        assert_eq!(tnt, format!("{}", &ast));
    }
}