use std::path::{Path, PathBuf};
use std::sync::atomic::{AtomicU64, Ordering};

/// A uniquely-named directory under the system temp dir removed when dropped
#[derive(Debug)]
pub struct ScratchDir(PathBuf);

impl ScratchDir {
    /// `tag` only makes a leaked directory identifiable if the destructor is
    /// skipped
    #[must_use]
    pub fn new(tag: &str) -> Self {
        static COUNTER: AtomicU64 = AtomicU64::new(0);
        let n = COUNTER.fetch_add(1, Ordering::Relaxed);

        let path = std::env::temp_dir().join(format!("oneclient-{tag}-{}-{n}", std::process::id()));
        std::fs::create_dir_all(&path)
            .unwrap_or_else(|e| panic!("failed to create scratch dir {}: {e}", path.display()));

        Self(path)
    }

    #[must_use]
    pub fn path(&self) -> &Path {
        &self.0
    }

    #[must_use]
    pub fn join(&self, name: impl AsRef<Path>) -> PathBuf {
        self.0.join(name)
    }
}

impl AsRef<Path> for ScratchDir {
    fn as_ref(&self) -> &Path {
        &self.0
    }
}

impl Drop for ScratchDir {
    fn drop(&mut self) {
        let _ = std::fs::remove_dir_all(&self.0);
    }
}