Agent-based state management for WebSocket connection configuration and status.

This module provides centralized state management for socket connections, including configuration parameters, connection status, and custom state values. All state is stored in an Agent process for concurrent access and updates.

The state is managed by the Phoenix.SocketClient.State struct.

Shared State Limitation

This module uses an Agent as shared mutable state that is read and written to by multiple processes (the Socket GenServer, Channel GenServers, and external callers). While Agent serializes individual get and update calls, it does not provide compound read-then-write atomicity across callers. This means concurrent operations that depend on reading the current state and then updating it can race with each other.

Future Refactoring Direction

A more robust approach would be to replace this Agent with a dedicated GenServer that owns and mediates all state access. A GenServer would allow:

• Compound read-modify-write operations handled atomically in handle_call
• Explicit control over which operations are synchronous vs asynchronous
• Better visibility into state access patterns via callbacks
• Easier addition of validation or side effects on state transitions

See GitHub issue #31 for discussion.