// SPDX-FileCopyrightText: 2025 Tomasz Kramkowski <tomasz@kramkow.ski>
// SPDX-License-Identifier: GPL-3.0-or-later

pub fn topic_match(filter: &str, topic: &str) -> bool {
    // TODO: Should probably just be a panic or prevented using types
    if filter.is_empty() || topic.is_empty() {
        return false;
    }
    if topic.starts_with('$') && (filter.starts_with('+') || filter.starts_with('#')) {
        return false;
    }

    // zip_longest would be nice
    let mut topic = topic.split('/');
    let mut filter = filter.split('/');
    loop {
        let topic_level = topic.next();
        return match filter.next() {
            Some("#") => filter.next().is_none(),
            Some("+") => {
                if topic_level.is_none() {
                    false
                } else {
                    continue;
                }
            }
            Some(filter_level) => match topic_level {
                Some(topic_level) if topic_level == filter_level => {
                    continue;
                }
                _ => false,
            },
            None => topic_level.is_none(),
        };
    }
}

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

    #[test]
    fn topic_match_basic() {
        assert!(topic_match("foo/bar/baz", "foo/bar/baz"));
        assert!(!topic_match("foo/bar/baz", "foo/bar/qux"));
        assert!(!topic_match("foo/bar", "foo/bar/baz"));
        assert!(!topic_match("foo/bar/baz", "foo/bar"));
    }

    #[test]
    fn topic_match_wildcard_hash() {
        assert!(topic_match("foo/bar/baz/#", "foo/bar/baz"));
        assert!(topic_match("foo/bar/baz/#", "foo/bar/baz/qux"));
        assert!(topic_match("foo/bar/baz/#", "foo/bar/baz/qux/quux"));
        assert!(topic_match("#", "foo/bar/baz"));
        assert!(topic_match("#", "foo"));
        assert!(topic_match("#", "/"));
        assert!(topic_match("#", "/foo"));
        assert!(!topic_match("foo/bar/#", "foo/baz/bar"));
        assert!(!topic_match("foo/bar/#", "foo"));
    }

    #[test]
    fn topic_match_wildcard_plus() {
        assert!(topic_match("foo/bar/+", "foo/bar/baz"));
        assert!(topic_match("foo/bar/+", "foo/bar/qux"));
        assert!(!topic_match("foo/bar/+", "foo/bar/baz/qux"));
        assert!(topic_match("foo/+", "foo/"));
        assert!(!topic_match("foo/+", "foo"));
        assert!(topic_match("+", "foo"));
        assert!(topic_match("+/bar/#", "foo/bar/baz/qux"));
        assert!(topic_match("+/bar/#", "qux/bar"));
        assert!(topic_match("foo/+/baz", "foo/bar/baz"));
        assert!(topic_match("foo/+/baz", "foo/qux/baz"));
        assert!(!topic_match("foo/+/baz", "foo/bar/qux"));
        assert!(topic_match("+/+", "/foo"));
        assert!(topic_match("/+", "/foo"));
        assert!(!topic_match("+", "/foo"));
    }

    #[test]
    fn topic_match_dollar() {
        assert!(!topic_match("#", "$foo/bar"));
        assert!(!topic_match("+/bar/baz", "$foo/bar/baz"));
        assert!(topic_match("$foo/#", "$foo/bar"));
        assert!(topic_match("$foo/#", "$foo/bar/baz"));
        assert!(topic_match("$foo/#", "$foo"));
        assert!(topic_match("$foo/bar/+", "$foo/bar/baz"));
        assert!(!topic_match("$foo/#", "foo/bar"));
    }

    #[test]
    fn topic_match_edge_cases() {
        assert!(!topic_match("foo", "FOO"));
        assert!(topic_match("foo bar", "foo bar"));
        assert!(!topic_match("foo bar", "foo  bar"));
        assert!(!topic_match("foo  bar", "foo bar"));
        assert!(!topic_match("/foo", "foo"));
        assert!(!topic_match("foo", "/foo"));
        assert!(topic_match("foo//bar", "foo//bar"));
        assert!(!topic_match("foo/bar", "foo//bar"));
        assert!(!topic_match("foo//bar", "foo/bar"));
        assert!(!topic_match("foo//baz", "foo/bar/baz"));
        assert!(!topic_match("foo/bar/baz", "foo//baz"));
        assert!(topic_match("foo/+/baz", "foo//baz"));
        assert!(topic_match("/", "/"));
        assert!(!topic_match("/", "foo"));
        assert!(!topic_match("foo", "/"));
        assert!(!topic_match("", ""));
        assert!(!topic_match("+", ""));
        assert!(!topic_match("#", ""));
        assert!(!topic_match("foo/#/baz", "foo/bar/baz"));
    }
}