/// Add a Verse to a Poem
///
/// Takes the current word stack, and pushes it onto the stanza. Then, takes
/// the stanza, meter, and some metadata details to create a Verse. That Verse
/// then gets added to the Poem.
///
/// # Arguments
/// * `$word` - The word stack, used to hold chars dilineated via whitespace
/// * `$stanza` - The stanza stack, used to hold words when they are popped off
///               the word stack
/// * `$cprev` - Indicates this is the second half of a couplet (normally this
///              is just Verse::couplet(prev), but we may need to set it in
///              case of Meter::Read), since this basically just tells the
///              shell to use `$out` in the `task!` macro
/// * `$prev` - The previous verse (or none if there is no previous verse)
/// * `$verses` - The list of verses that make up the poem
/// * `$meter` - The meter corresponding to the verse
#[macro_export]
macro_rules! push {
    ($word:expr, $stanza:expr, $cprev:expr, $prev:expr, $verses:expr, $meter:expr) => {
        // If there are chars on the word stack, push that word onto the stanza
        if !$word.is_empty() {
            $stanza.push($word.iter().collect());
        }

        // Check if the last verse was a meter of Read, Write, or
        // Addendum, and throw an error if it is
        if Verse::rw($prev) && $stanza.is_empty() {
            let rw = match $prev.unwrap().meter {
                Meter::Read => "read",
                Meter::Write => "write",
                Meter::Addendum => "append",
                _ => "",
            };
            eprintln!("dwvsh: parse error: no {} file(s) specified", rw);
            return None;
        }

        // A meter indicates the end of a verse
        if !$stanza.is_empty() {
            $verses.push(Verse::new(
                Stanza::new($stanza.clone()),
                $meter,
                $cprev,
                Verse::rw($prev),
            ));
        }

        // Clear the stacks
        $stanza.clear();
        $word.clear();
    };
}

/// Add a Verse to a Poem, but allow looking ahead by one char
///
/// This works the exact same as [[push]], except that it doesn't take
/// `$cprev` (since there is no need to set it manually right now), and it
/// takes `$ahead`, which is the next character to look for in the pattern,
/// along with `$aheadm`, which is the corresponding Meter if that `$ahead` is
/// found.
///
/// # Examples
/// ```
/// push1!(word, stanza, prev, verses, Meter::Quiet, '&', Meter::And);
/// push1!(word, stanza, prev, verses, Meter::Write, '>', Meter::Addendum);
/// ```
#[macro_export]
macro_rules! push1 {
    ($word:expr, $stanza:expr, $chars:expr, $prev:expr, $verses: expr, $meter:expr, $ahead:expr, $aheadm:expr) => {
        // If there are chars on the word stack, push that word
        // onto the stanza
        if !$word.is_empty() {
            $stanza.push($word.iter().collect());
        }

        // Check if the last verse was a meter of Read, Write, or
        // Addendum, and throw an error if it is
        if Verse::rw($prev) && $stanza.is_empty() {
            let rw = match $prev.unwrap().meter {
                Meter::Read => "read",
                Meter::Write => "write",
                Meter::Addendum => "append",
                _ => "",
            };
            eprintln!("dwvsh: parse error: no {} file(s) specified", rw);
            return None;
        }

        // Need to peek at the next character, since '>' can mean
        // Meter::Write, or '>>' can mean Meter::Addendum
        match $chars.clone().peekable().peek() {
            // Indicated Meter::Addendum
            Some(c) if c == &$ahead => {
                // Pop the next character from the input string
                // (since we know what it is)
                $chars.next();

                // A meter indicates the end of a verse
                $verses.push(Verse::new(
                    Stanza::new($stanza.clone()),
                    $aheadm,
                    Verse::couplet($prev),
                    Verse::rw($prev),
                ));
            }

            // Indicates Meter::Write
            Some(_) => {
                // A meter indicates the end of a verse
                $verses.push(Verse::new(
                    Stanza::new($stanza.clone()),
                    $meter,
                    Verse::couplet($prev),
                    Verse::rw($prev),
                ));
            }

            // Indicated the end of the input
            None => {
                // A meter indicates the end of a verse
                $verses.push(Verse::new(
                    Stanza::new($stanza.clone()),
                    $meter,
                    Verse::couplet($prev),
                    Verse::rw($prev),
                ));
            }
        }

        // Clear the stacks
        $stanza.clear();
        $word.clear();
    };
}