Design a Music Player with Queue, Loop, and Shuffle

Design the objects and interfaces for a music player with play, pause, and next operations. Add a play queue, playlist looping, and shuffle. Explain the state transitions and how the player coordinates these features with an audio backend whose operations can be stubbed.

Constraints & Assumptions

• This is an object-oriented design and communication exercise. Actual audio decoding and device output are behind a stubbed interface.
• Define queue precedence, end-of-playlist behavior, loop mode, and shuffle semantics explicitly; the source lists the features without fixing those policies.
• Track identity must not depend on the title alone. A playlist may contain repeated tracks.
• Begin with one local user and serialized commands. Network streaming and multi-device synchronization are outside the baseline.

Clarifying Questions to Ask

• Does a manually queued track play before the next playlist entry?
• Does loop mean repeat the current track, repeat the playlist, or both?
• Should shuffle preserve the current track and visit each remaining playlist occurrence once before repeating?
• Is play while paused a resume, and what should next do while paused?