//! POSIX path helpers with Node `path.posix` semantics (normalize/join/basename/dirname).

pub fn normalize(path: &str) -> String {
    if path.is_empty() {
        return ".".into();
    }
    let absolute = path.starts_with('/');
    let trailing = path.ends_with('/');
    let mut parts: Vec<&str> = Vec::new();
    for segment in path.split('/') {
        match segment {
            "" | "." => {}
            ".." => {
                if parts.last().is_some_and(|p| *p != "..") {
                    parts.pop();
                } else if !absolute {
                    parts.push("..");
                }
            }
            other => parts.push(other),
        }
    }
    let mut out = parts.join("/");
    if out.is_empty() && !absolute {
        out = ".".into();
    }
    if !out.is_empty() && trailing {
        out.push('/');
    }
    if absolute {
        format!("/{out}")
    } else {
        out
    }
}

pub fn join(base: &str, name: &str) -> String {
    let joined = match (base.is_empty(), name.is_empty()) {
        (true, true) => return ".".into(),
        (true, false) => name.to_string(),
        (false, true) => base.to_string(),
        _ => format!("{base}/{name}"),
    };
    normalize(&joined)
}

pub fn basename(path: &str) -> String {
    path.trim_end_matches('/').rsplit('/').next().unwrap_or("").to_string()
}

/// Directory part of a normalized path (`/a/b` → `/a`, `/a` → `/`).
pub fn dirname(path: &str) -> String {
    let trimmed = path.trim_end_matches('/');
    if trimmed.is_empty() {
        return if path.starts_with('/') { "/".into() } else { ".".into() };
    }
    match trimmed.rfind('/') {
        Some(0) => "/".into(),
        Some(i) => {
            let parent = trimmed[..i].trim_end_matches('/');
            if parent.is_empty() { "/".into() } else { parent.to_string() }
        }
        None => ".".into(),
    }
}

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

    #[test]
    fn node_compatible() {
        assert_eq!(normalize("/a//b/../c/./d/"), "/a/c/d/");
        assert_eq!(normalize("/../.."), "/");
        assert_eq!(normalize("/"), "/");
        assert_eq!(join("/", "x"), "/x");
        assert_eq!(join("/a/b", "c"), "/a/b/c");
        assert_eq!(basename("/a/b/"), "b");
        assert_eq!(dirname("/a/b"), "/a");
        assert_eq!(dirname("/a"), "/");
        assert_eq!(dirname("/a//b"), "/a");
    }
}