//! Reading the Erlang cookie from a file.

use std::io;
use std::path::Path;

/// The cookie file autoconnect reads when none is named on the command line.
pub const DEFAULT_COOKIE_FILE: &str = ".erlang.cookie";

/// Reads a cookie from `path`, trimming the surrounding whitespace Erlang's own
/// cookie files carry.
///
/// # Errors
/// Returns an error if the file cannot be read, or holds nothing but whitespace.
pub fn read_cookie(path: &Path) -> io::Result<String> {
    let contents = std::fs::read_to_string(path)?;
    let cookie = contents.trim();

    if cookie.is_empty() {
        return Err(io::Error::new(
            io::ErrorKind::InvalidData,
            format!("cookie file '{}' is empty", path.display()),
        ));
    }

    Ok(cookie.to_string())
}

#[cfg(test)]
#[allow(clippy::unwrap_used, clippy::expect_used)]
mod tests {
    use super::*;
    use std::io::Write;

    fn cookie_file(contents: &str) -> tempfile::NamedTempFile {
        let mut file = tempfile::NamedTempFile::new().unwrap();
        file.write_all(contents.as_bytes()).unwrap();
        file.flush().unwrap();
        file
    }

    #[test]
    fn reads_a_cookie() {
        let file = cookie_file("SECRETCOOKIE");
        assert_eq!(read_cookie(file.path()).unwrap(), "SECRETCOOKIE");
    }

    #[test]
    fn trims_surrounding_whitespace() {
        let file = cookie_file("  SECRETCOOKIE\n");
        assert_eq!(read_cookie(file.path()).unwrap(), "SECRETCOOKIE");
    }

    #[test]
    fn rejects_a_whitespace_only_cookie() {
        let file = cookie_file("\n  \n");
        let err = read_cookie(file.path()).unwrap_err();
        assert_eq!(err.kind(), io::ErrorKind::InvalidData);
    }

    #[test]
    fn reports_a_missing_file() {
        let err = read_cookie(Path::new("/nonexistent/.erlang.cookie")).unwrap_err();
        assert_eq!(err.kind(), io::ErrorKind::NotFound);
    }
}