Function safe_write_text_file

src/agents/mod.rs:664–710

Write text to a file via atomic sibling rename. Mirrors [`safe_write_json_file`] for generated prompt/rule files that are plain text rather than structured JSON. The target is not opened for writing until the final rename, so a failed write leaves the original untouched.

(path: &Path, contents: &str, backup: Option<&Path>)

/// plain text rather than structured JSON. The target is not opened for writing
/// until the final rename, so a failed write leaves the original untouched.
pub fn safe_write_text_file(path: &Path, contents: &str, backup: Option<&Path>) -> Result<()> {
    static TEMP_COUNTER: AtomicU64 = AtomicU64::new(0);

    if let Some(parent) = path.parent() {
        std::fs::create_dir_all(parent).map_err(|e| TraceDecayError::Config {
            message: format!("cannot create directory {}: {e}", parent.display()),
        })?;
    }

    let file_name = path
        .file_name()
        .and_then(|name| name.to_str())
        .unwrap_or("file");
    let unique = TEMP_COUNTER.fetch_add(1, Ordering::Relaxed);
    let new_name = format!(".{file_name}.{}.{}.new", std::process::id(), unique);
    let new_path = path
        .parent()
        .map_or_else(|| PathBuf::from(&new_name), |parent| parent.join(&new_name));
    if let Err(e) = std::fs::write(&new_path, contents) {
        std::fs::remove_file(&new_path).ok();
        return Err(TraceDecayError::Config {
            message: format!("failed to write new text file {}: {e}", new_path.display()),
        });
    }

    if let Err(e) = std::fs::rename(&new_path, path) {
        std::fs::remove_file(&new_path).ok();
        let hint = if let Some(b) = backup {
            format!(
                "\n  Backup is at: {}\n  \
                 The original file was NOT modified.",
                b.display()
            )
        } else {
            "\n  The original file was NOT modified.".to_string()
        };
        return Err(TraceDecayError::Config {
            message: format!(
                "failed to rename {} → {}: {e}{hint}",
                new_path.display(),
                path.display()
            ),
        });
    }

    Ok(())
}

/// Write a JSON value to a file with pretty formatting.
/// Creates a backup, writes atomically, and restores on failure.