Provides string manipulation utilities (trim, word_expand, word_wrap, basename) and XDG directory helpers. These are isolated, reusable functions that could be extracted to a utility library with minimal changes. The word_expand function handles environment variable expansion safely, and word_wrap implements proper text wrapping logic.

Implements a file change monitor using inotify on Linux. It's self-contained, handles edge cases (file deletion, moves), and could be reused in any project needing file monitoring with minimal modification. Properly cleans up resources and handles errors.

A lightweight event bus implementation with support for first/last/default position subscribers. It's completely isolated, uses std::function for callbacks, and could be dropped into any C++ project. The implementation is clean and handles subscription lifecycle properly.

Handles downloading and detecting playlist formats (M3U, PLS, ASX, etc.) and direct streams. It uses a strategy pattern with decoder plugins. While it depends on some internal types, the core logic for detecting direct streams and trying multiple decoders is reusable. The curl_write_callback shows good handling of size limits.

Abstracts notification functionality with platform-specific implementations (Linux via libnotify, Darwin via terminal-notifier). The interface is clean and the implementations are isolated. This pattern could be reused for any cross-platform notification need.