Create SafeBox Playground in :app module with Dispatcher Toggle and Text Persistence

[harrytmthy]

Background

This playground serves both contributors and users:

• Helps newcomers understand SafeBox's threading behavior.
• Verifies lifecycle correctness and OnSharedPreferenceChangeListener support.
• Aids in debugging performance, concurrency, and cryptographic internals.
• Lays the groundwork for future observability features.

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Goal

Introduce a minimal Jetpack Compose-based :app module that serves as an interactive SafeBox Playground:

UI Features

• Key input field

• Value input field

• Switch: Toggles between Apply/Commit Mode.

• Buttons:

  • Validate Key: Calls safeBox.contains(key) and shows a snackbar with the result.
  • Get: Calls safeBox.getString(...) then updates Value field with result (default: null).
  • Put: Starts safeBox.edit() (if needed) then calls editor.putString(key, value).
  • Clear: Starts safeBox.edit() (if needed) then calls editor.clear().
  • Apply / Commit: Triggers apply/commit towards the staged changes. Shows a snackbar if no edits are staged.

• Dispatcher Toggle:
  Choose coroutine context for safeBox.getString(...) between Main, IO, or Default.

• Staged Changes View:
  Displays all pending (uncommitted) key-value pairs.

• Committed Entries View:
  Displays current key-value pairs from safeBox.getAll(), auto-updated via OnSharedPreferenceChangeListener.

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MVP Scope

• Built with Jetpack Compose (preferred for future UI benchmarking).
• Clean, unidirectional architecture with MVVM/MVI.
• No Gradle script changes unless necessary.
• No metrics/benchmarking tools for now.
• No DI or Hilt/Koin setup required.

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Future Ideas (Not part of MVP)

• Add Choreographer-based frame skip detection.
• Visualize read/write durations.
• Monitor CipherPool size and idle lifespan.
• Simulate race conditions for educational purposes.