# Actor System Implementation Status

## Current State (v3.58.0)

### ✅ What Works

#### Parser Support (Complete)
- Actor definitions with state fields
- Receive blocks with pattern matching
- Message handlers with parameters
- Spawn expressions
- Send operations (`.send()` method)
- Ask operations (`.ask()` method)

#### Runtime Implementation (Major Progress)
- Actor definitions are recognized as a type
- Spawn syntax creates real actor instances with runtime IDs
- Send operations enqueue messages in actor mailboxes
- State persistence for basic field updates (count increment)
- Message processing for simple handlers
- **NEW: Concurrent actor execution in separate threads**
- **NEW: Supervision trees with error recovery**
- **NEW: Restart strategies (OneForOne, AllForOne, RestForOne)**
- **NEW: Actor lifecycle management (Starting, Running, Stopping, Failed, Restarting)**
- **NEW: System messages for lifecycle control**

### ❌ What Doesn't Work

#### Runtime Limitations
1. **Limited Message Passing**: Basic message queuing works, complex handlers still need interpreter integration
2. ~~**No Concurrency**: Actors run synchronously in the same thread~~ **FIXED in v3.58.0**
3. **Partial State Persistence**: Simple field updates work (integers), complex types pending
4. ~~**No Mailbox**: Messages aren't stored or processed in order~~ **FIXED in v3.57.0**
5. ~~**No Supervision**: No supervisor trees or error recovery~~ **FIXED in v3.58.0**

## Test Coverage

### Current Status
- **Parser tests**: 15/17 passing (88.2%)
- **Runtime tests**: Actor state modification working
- **Concurrent tests**: All passing (creation, messaging, lifecycle)
- **Overall actor coverage**: ~85%
- **Key achievements**:
  - Basic message passing and state persistence functional
  - Concurrent execution with thread isolation
  - Supervision trees with restart strategies

### Failing Tests Categories
1. **State modification tests**: Require persistent mutable state
2. **Message ordering tests**: Need proper message queue
3. **Concurrent execution tests**: Need threading/async runtime
4. **Supervision tests**: Need error handling infrastructure

## Architectural Requirements

To complete the actor system, we need:

### 1. Message Queue Infrastructure
```rust
struct ActorMailbox {
    messages: VecDeque<Message>,
    capacity: usize,
}
```

### 2. Actor Runtime
```rust
struct ActorRuntime {
    actors: HashMap<ActorId, ActorState>,
    scheduler: MessageScheduler,
}
```

### 3. State Management
- Similar to mutable self issue in classes
- Need to track and update actor state after message processing
- Requires architectural refactoring

## Comparison with Classes

Both actors and classes suffer from the same core issue:
- **Classes**: Methods with `&mut self` don't persist changes
- **Actors**: Message handlers that modify state don't persist changes

The root cause is the same: we clone state for processing but never update the original.

## Recommendation

The actor system requires significant architectural work similar to fixing mutable self in classes. These should be addressed together in a dedicated refactoring sprint focusing on:

1. Reference tracking for mutable objects
2. State persistence after mutations
3. Proper isolation and concurrency primitives

## Usage Warning

While actor syntax is parsed correctly, the runtime behavior is incomplete. Users should not rely on actors for:
- Concurrent processing
- Message ordering guarantees
- State persistence
- Error isolation

The current implementation is suitable only for:
- Syntax validation
- Basic structural testing
- Future development foundation