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use nom::{combinator::map, IResult};

use crate::transaction::{transaction, Transaction};

/// A directive
///
/// A beancount file is made of directives.
///
/// By far the the most common directive is the [`Transaction`].
#[derive(Debug, Clone)]
#[non_exhaustive]
pub enum Directive<'a> {
    /// The transaction directive
    Transaction(Transaction<'a>),
}

impl<'a> Directive<'a> {
    /// Returns the [`Transaction`] reference if this directive is a transaction
    ///
    /// See also [`Directive::into_transaction`]
    #[must_use]
    pub fn as_transaction(&self) -> Option<&Transaction<'a>> {
        match self {
            Directive::Transaction(trx) => Some(trx),
        }
    }

    /// Convert into a [`Transaction`] if this directive is a transaction
    ///
    /// See also [`Directive::as_transaction`]
    #[must_use]
    pub fn into_transaction(self) -> Option<Transaction<'a>> {
        match self {
            Directive::Transaction(trx) => Some(trx),
        }
    }
}

pub(crate) fn directive(input: &str) -> IResult<&str, Directive<'_>> {
    map(transaction, Directive::Transaction)(input)
}

#[cfg(test)]
mod tests {
    use super::*;
    use rstest::rstest;

    #[test]
    fn transaction() {
        let input = r#"2022-09-10 txn "My transaction""#;
        let (_, directive) = directive(input).expect("should successfully parse directive");
        let transaction = directive
            .as_transaction()
            .expect("the directive should be a transaction");
        assert_eq!(transaction.narration(), Some("My transaction"));
    }

    #[rstest]
    fn invalid(
        #[values(
            "2022-09-11 txn that is incorrect",
            "2022-09-11 * that is incorrect",
            "2022-09-11 ! that is incorrect"
        )]
        input: &str,
    ) {
        assert!(matches!(directive(input), Err(nom::Err::Failure(_))));
    }

    #[rstest]
    fn not_matching(#[values(" ")] input: &str) {
        assert!(matches!(directive(input), Err(nom::Err::Error(_))));
    }
}