# Observable Property - Suggested Improvements

## Priority 1: Core API Extensions

### 1.1 Atomic Operations

#### `modify_async` - Async version of modify
```rust
pub fn modify_async<F>(&self, f: F) -> Result<(), PropertyError>
where F: FnOnce(&mut T)
```
**Rationale:** Consistency with `set`/`set_async` pattern. Useful for non-blocking atomic modifications.

#### `swap` - Atomic value exchange
```rust
pub fn swap(&self, new_value: T) -> Result<T, PropertyError>
```
**Rationale:** Common pattern - update value and return old value in one operation.

#### `compare_and_set` - Conditional update (CAS)
```rust
pub fn compare_and_set(&self, expected: &T, new_value: T) -> Result<bool, PropertyError>
where T: PartialEq
```
**Rationale:** Essential for lock-free algorithms and optimistic concurrency control.

#### `update_if` - Conditional modification
```rust
pub fn update_if<F, P>(&self, predicate: P, updater: F) -> Result<bool, PropertyError>
where F: FnOnce(&mut T), P: FnOnce(&T) -> bool
```
**Rationale:** Atomically check condition and update if true.

### 1.2 Observability Methods

```rust
pub fn max_threads(&self) -> usize
pub fn max_observers(&self) -> usize
pub fn has_observers(&self) -> bool
```
**Rationale:** Better runtime introspection for debugging and monitoring.

### 1.3 Batch Operations

```rust
pub fn subscribe_batch(&self, observers: Vec<Observer<T>>) -> Result<Vec<ObserverId>, PropertyError>
pub fn unsubscribe_batch(&self, ids: Vec<ObserverId>) -> Result<Vec<bool>, PropertyError>
pub fn unsubscribe_all(&self) -> Result<usize, PropertyError>
```
**Rationale:** Performance optimization for bulk management.

---

## Priority 2: Performance Optimizations

### 2.1 Skip Unchanged Notifications

```rust
pub fn set_if_changed(&self, new_value: T) -> Result<bool, PropertyError>
where T: PartialEq
```
**Rationale:** Avoid unnecessary observer notifications when value hasn't actually changed.

### 2.2 Peek Without Cloning

```rust
pub fn peek<R, F>(&self, f: F) -> Result<R, PropertyError>
where F: FnOnce(&T) -> R
```
**Rationale:** Read value without expensive clone for large types.

### 2.3 Weak Observer References

```rust
pub fn subscribe_weak(&self, observer: Observer<T>) -> Result<ObserverId, PropertyError>
```
**Rationale:** Allow observers to be garbage collected, preventing memory leaks in some scenarios.

---

## Priority 3: Builder Pattern

```rust
pub struct ObservablePropertyBuilder<T> {
    initial_value: T,
    max_threads: usize,
    max_observers: usize,
}

impl<T> ObservablePropertyBuilder<T> {
    pub fn new(initial_value: T) -> Self
    pub fn max_threads(mut self, max_threads: usize) -> Self
    pub fn max_observers(mut self, max_observers: usize) -> Self
    pub fn build(self) -> ObservableProperty<T>
}
```

**Usage:**
```rust
let property = ObservablePropertyBuilder::new(42)
    .max_threads(8)
    .max_observers(5000)
    .build();
```

---

## Priority 4: Advanced Features

### 4.1 Value Transformation/Mapping

```rust
pub fn map<U, F>(&self, mapper: F) -> ObservableProperty<U>
where 
    U: Clone + Send + Sync + 'static,
    F: Fn(&T) -> U + Send + Sync + 'static
```
**Rationale:** Create derived properties that automatically update.

### 4.2 Debouncing/Throttling

```rust
pub fn subscribe_debounced(
    &self, 
    observer: Observer<T>,
    duration: Duration
) -> Result<ObserverId, PropertyError>

pub fn subscribe_throttled(
    &self,
    observer: Observer<T>, 
    duration: Duration
) -> Result<ObserverId, PropertyError>
```
**Rationale:** Rate-limit notifications for high-frequency properties.

### 4.3 History Tracking

```rust
pub fn with_history(initial_value: T, capacity: usize) -> Self
pub fn history(&self) -> Result<Vec<T>, PropertyError>
pub fn undo(&self) -> Result<(), PropertyError>
pub fn redo(&self) -> Result<(), PropertyError>
```
**Rationale:** Time-travel debugging and undo functionality.

### 4.4 Transaction Support

```rust
pub fn transaction<F, R>(&self, f: F) -> Result<R, PropertyError>
where F: FnOnce(&mut T) -> R
```
**Rationale:** Batch multiple changes, notify observers only once.

---

## Priority 5: Async/Await Support

### 5.1 Tokio Integration

```rust
#[cfg(feature = "tokio")]
pub async fn set_tokio(&self, new_value: T) -> Result<(), PropertyError>

#[cfg(feature = "tokio")]
pub async fn subscribe_tokio(&self, observer: Observer<T>) -> Result<ObserverId, PropertyError>
```

### 5.2 Future-based Notifications

```rust
pub fn next_change(&self) -> impl Future<Output = (T, T)>
pub fn wait_for<F>(&self, predicate: F) -> impl Future<Output = T>
where F: Fn(&T) -> bool
```

---

## Priority 6: Observability & Debugging

### 6.1 Named Observers

```rust
pub fn subscribe_named(
    &self, 
    name: &str,
    observer: Observer<T>
) -> Result<ObserverId, PropertyError>

pub fn observer_names(&self) -> Vec<String>
```

### 6.2 Metrics Collection

```rust
pub struct PropertyMetrics {
    pub total_changes: usize,
    pub total_notifications: usize,
    pub observer_count: usize,
    pub avg_notification_time: Duration,
}

pub fn metrics(&self) -> Result<PropertyMetrics, PropertyError>
```

### 6.3 Change Logging

```rust
pub fn enable_change_log(&self, capacity: usize)
pub fn change_log(&self) -> Vec<(Instant, T, T)>
```

---

## Priority 7: Quality of Life

### 7.1 Convenient Constructors

```rust
impl<T: Default + Clone + Send + Sync + 'static> ObservableProperty<T> {
    pub fn default() -> Self
}

impl<T: Clone + Send + Sync + 'static> From<T> for ObservableProperty<T> {
    fn from(value: T) -> Self
}
```

### 7.2 Macros for Observer Creation

```rust
#[macro_export]
macro_rules! observe {
    ($prop:expr, |$old:ident, $new:ident| $body:expr) => {
        $prop.subscribe(Arc::new(|$old, $new| $body))
    };
}
```

**Usage:**
```rust
observe!(property, |old, new| {
    println!("Changed: {} -> {}", old, new);
})?;
```

---

## Priority 8: Optional Features (Cargo Features)

### 8.1 Serde Support

```toml
[features]
serde = ["dep:serde"]

[dependencies]
serde = { version = "1.0", optional = true }
```

```rust
#[cfg(feature = "serde")]
impl<T: Serialize + Deserialize> Serialize for ObservableProperty<T> {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where S: Serializer
}
```

### 8.2 Tokio Support

```toml
[features]
tokio = ["dep:tokio"]
```

### 8.3 Tracing Support

```toml
[features]
tracing = ["dep:tracing"]
```

---

## Documentation Improvements

1. **Benchmarks:** Add performance benchmarks comparing sync vs async notifications
2. **Cookbook:** Add common patterns (e.g., UI binding, state management, caching)
3. **Migration Guide:** From other observer patterns/libraries
4. **Architecture Diagram:** Visual explanation of thread model
5. **Performance Guide:** When to use sync vs async, thread pool sizing
6. **Examples:** More real-world scenarios (game state, configuration management, etc.)

---

## Testing Status

### ✅ Completed (v0.4.2)
- **Exhaustive unit test coverage**: 128 comprehensive unit tests covering all features
- **Complete documentation tests**: 107 doc tests ensuring all examples work correctly
- **100% feature coverage**: All public APIs tested with both happy paths and error conditions
- **Edge case testing**: Lock poisoning, observer panics, concurrent access, resource limits
- **Error condition testing**: Invalid inputs, boundary conditions, failure scenarios

### Future Testing Improvements

1. **Property-based testing** with `proptest` or `quickcheck` for randomized input testing
2. **Stress tests** for high-load scenarios with thousands of observers
3. **Benchmark suite** with `criterion` for performance regression detection
4. **Fuzz testing** for discovering edge cases
5. **Memory leak tests** with `valgrind`/`miri` for memory safety verification

---

## Implementation Priority

### Phase 1 (Core Extensions - Week 1)
- ✅ `modify_async`
- ✅ `swap`
- ✅ `compare_and_set` 
- ✅ Observability methods (max_threads, max_observers, has_observers)
- ✅ Builder pattern

### Phase 2 (Performance - Week 2)
- `set_if_changed`
- `peek`
- Batch operations
- Skip-notification optimization

### Phase 3 (Advanced - Week 3-4)
- `map` for derived properties
- Debouncing/throttling
- Transaction support
- History tracking

### Phase 4 (Async - Week 5)
- Tokio integration
- Future-based APIs
- Async iterators for changes

### Phase 5 (Polish - Week 6)
- Metrics and observability
- Macros for convenience
- Serde support
- Documentation improvements

---

## Breaking Changes to Consider

### Version 1.0 Considerations

1. **Error enum cleanup:** Remove unused error variants with graceful degradation
2. **API simplification:** Remove redundant methods
3. **Naming consistency:** Ensure all method names follow clear patterns
4. **Default behavior:** Consider making RAII subscriptions the default

---

## Community Suggestions

File issues on GitHub for:
- Feature requests from users
- Performance comparisons with other libraries
- Use case documentation
- Integration examples (web frameworks, game engines, etc.)
