use std::path::{Path, PathBuf};

/// Resolves a (possibly relative) tool-supplied path against `cwd`.
pub fn resolve(cwd: &Path, file_path: &str) -> PathBuf {
    let path = Path::new(file_path);
    if path.is_absolute() {
        path.to_path_buf()
    } else {
        cwd.join(path)
    }
}

/// Slash-separated path relative to `cwd`, used as the permission pattern — falls back to
/// the absolute path (still slash-separated) when `path` isn't under `cwd`.
pub fn relative_pattern(cwd: &Path, path: &Path) -> String {
    let rel = path.strip_prefix(cwd).unwrap_or(path);
    rel.to_string_lossy().replace('\\', "/")
}

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

    #[test]
    fn resolve_joins_relative_paths_to_cwd() {
        let cwd = Path::new("/home/user/project");
        assert_eq!(
            resolve(cwd, "src/main.rs"),
            PathBuf::from("/home/user/project/src/main.rs")
        );
    }

    #[test]
    fn resolve_leaves_absolute_paths_untouched() {
        let cwd = Path::new("/home/user/project");
        assert_eq!(resolve(cwd, "/etc/hosts"), PathBuf::from("/etc/hosts"));
    }

    #[test]
    fn relative_pattern_strips_cwd_prefix() {
        let cwd = Path::new("/home/user/project");
        let path = Path::new("/home/user/project/src/main.rs");
        assert_eq!(relative_pattern(cwd, path), "src/main.rs");
    }

    #[test]
    fn relative_pattern_falls_back_to_absolute_outside_cwd() {
        let cwd = Path::new("/home/user/project");
        let path = Path::new("/etc/hosts");
        assert_eq!(relative_pattern(cwd, path), "/etc/hosts");
    }
}