qubit_function/consumers/

stateful_consumer.rs

/*******************************************************************************
 *
 *    Copyright (c) 2025 - 2026.
 *    Haixing Hu, Qubit Co. Ltd.
 *
 *    All rights reserved.
 *
 ******************************************************************************/
//! # Consumer Types
//!
//! Provides implementations of consumer interfaces for executing operations
//! that accept a single input parameter but return no result.
//!
//! It is similar to the `FnMut(&T)` trait in the standard library.
//!
//! This module provides a unified `Consumer` trait and three concrete
//! implementations based on different ownership models:
//!
//! - **`BoxStatefulConsumer<T>`**: Box-based single ownership implementation for
//!   one-time use scenarios
//! - **`ArcStatefulConsumer<T>`**: Thread-safe shared ownership implementation
//!   based on Arc<Mutex<>>
//! - **`RcStatefulConsumer<T>`**: Single-threaded shared ownership implementation
//!   based on Rc<RefCell<>>
//!
//! # Design Philosophy
//!
//! Consumer uses `FnMut(&T)` semantics, allowing modification of its own state
//! but not the input value.
//!
//! Suitable for statistics, accumulation, event handling, and other scenarios.
//!
//! # Author
//!
//! Haixing Hu
use std::cell::RefCell;
use std::rc::Rc;
use std::sync::Arc;

use parking_lot::Mutex;

use crate::consumers::consumer_once::BoxConsumerOnce;
use crate::consumers::macros::{
    impl_box_conditional_consumer,
    impl_box_consumer_methods,
    impl_conditional_consumer_clone,
    impl_conditional_consumer_conversions,
    impl_conditional_consumer_debug_display,
    impl_consumer_clone,
    impl_consumer_common_methods,
    impl_consumer_debug_display,
    impl_shared_conditional_consumer,
    impl_shared_consumer_methods,
};
use crate::macros::{
    impl_arc_conversions,
    impl_box_conversions,
    impl_closure_trait,
    impl_rc_conversions,
};
use crate::predicates::predicate::{
    ArcPredicate,
    BoxPredicate,
    Predicate,
    RcPredicate,
};

// ============================================================================
// 1. Consumer Trait - Unified Consumer Interface
// ============================================================================

/// Consumer trait - Unified consumer interface
///
/// Defines the core behavior of all consumer types. Similar to Java's
/// `Consumer<T>` interface, executes operations that accept a value but return
/// no result (side effects only).
///
/// It is similar to the `FnMut(&T)` trait in the standard library.
///
/// Consumer can modify its own state (such as accumulation, counting), but
/// should not modify the consumed value itself.
///
/// # Automatic Implementation
///
/// - All closures implementing `FnMut(&T)`
/// - `BoxStatefulConsumer<T>`, `ArcStatefulConsumer<T>`, `RcStatefulConsumer<T>`
///
/// # Features
///
/// - **Unified Interface**: All consumer types share the same `accept` method
///   signature
/// - **Automatic Implementation**: Closures automatically implement this trait
///   with zero overhead
/// - **Type Conversion**: Easy conversion between different ownership models
/// - **Generic Programming**: Write functions that work with any consumer type
///
/// # Examples
///
/// ```rust
/// use qubit_function::{Consumer, BoxStatefulConsumer, ArcStatefulConsumer};
/// use std::sync::{Arc, Mutex};
///
/// fn apply_consumer<C: StatefulConsumer<i32>>(consumer: &mut C, value: &i32) {
///     consumer.accept(value);
/// }
///
/// // Works with any consumer type
/// let log = Arc::new(Mutex::new(Vec::new()));
/// let l = log.clone();
/// let mut box_con = BoxStatefulConsumer::new(move |x: &i32| {
///     l.lock().unwrap().push(*x);
/// });
/// apply_consumer(&mut box_con, &5);
/// assert_eq!(*log.lock().unwrap(), vec![5]);
/// ```
///
/// # Author
///
/// Haixing Hu
pub trait StatefulConsumer<T> {
    /// Execute consumption operation
    ///
    /// Performs an operation on the given reference. The operation typically
    /// reads the input value or produces side effects, but does not modify the
    /// input value itself. Can modify the consumer's own state.
    ///
    /// # Parameters
    ///
    /// * `value` - Reference to the value to be consumed
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{Consumer, BoxStatefulConsumer};
    ///
    /// let mut consumer = BoxStatefulConsumer::new(|x: &i32| println!("{}", x));
    /// let value = 5;
    /// consumer.accept(&value);
    /// ```
    fn accept(&mut self, value: &T);

    /// Convert to BoxStatefulConsumer
    ///
    /// **⚠️ Consumes `self`**: The original consumer will be unavailable after
    /// calling this method.
    ///
    /// Converts the current consumer to `BoxStatefulConsumer<T>`.
    ///
    /// # Ownership
    ///
    /// This method **consumes** the consumer (takes ownership of `self`).
    /// After calling this method, the original consumer is no longer available.
    ///
    /// **Tip**: For cloneable consumers ([`ArcStatefulConsumer`], [`RcStatefulConsumer`]),
    /// if you need to preserve the original object, you can call `.clone()`
    /// first.
    ///
    /// # Return Value
    ///
    /// Returns the wrapped `BoxStatefulConsumer<T>`
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::Consumer;
    /// use std::sync::{Arc, Mutex};
    ///
    /// let log = Arc::new(Mutex::new(Vec::new()));
    /// let l = log.clone();
    /// let closure = move |x: &i32| {
    ///     l.lock().unwrap().push(*x);
    /// };
    /// let mut box_consumer = closure.into_box();
    /// box_consumer.accept(&5);
    /// assert_eq!(*log.lock().unwrap(), vec![5]);
    /// ```
    fn into_box(self) -> BoxStatefulConsumer<T>
    where
        Self: Sized + 'static,
        T: 'static,
    {
        let mut consumer = self;
        BoxStatefulConsumer::new(move |t| consumer.accept(t))
    }

    /// Convert to RcStatefulConsumer
    ///
    /// **⚠️ Consumes `self`**: The original consumer will be unavailable after
    /// calling this method.
    ///
    /// # Return Value
    ///
    /// Returns the wrapped `RcStatefulConsumer<T>`
    fn into_rc(self) -> RcStatefulConsumer<T>
    where
        Self: Sized + 'static,
        T: 'static,
    {
        let mut consumer = self;
        RcStatefulConsumer::new(move |t| consumer.accept(t))
    }

    /// Convert to ArcStatefulConsumer
    ///
    /// **⚠️ Consumes `self`**: The original consumer will be unavailable after
    /// calling this method.
    ///
    /// # Return Value
    ///
    /// Returns the wrapped `ArcStatefulConsumer<T>`
    fn into_arc(self) -> ArcStatefulConsumer<T>
    where
        Self: Sized + Send + 'static,
        T: 'static,
    {
        let mut consumer = self;
        ArcStatefulConsumer::new(move |t| consumer.accept(t))
    }

    /// Convert to closure
    ///
    /// **⚠️ Consumes `self`**: The original consumer will be unavailable after
    /// calling this method.
    ///
    /// Converts the consumer to a closure that can be used directly in standard
    /// library functions requiring `FnMut`.
    ///
    /// # Return Value
    ///
    /// Returns a closure implementing `FnMut(&T)`
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{Consumer, BoxStatefulConsumer};
    /// use std::sync::{Arc, Mutex};
    ///
    /// let log = Arc::new(Mutex::new(Vec::new()));
    /// let l = log.clone();
    /// let consumer = BoxStatefulConsumer::new(move |x: &i32| {
    ///     l.lock().unwrap().push(*x);
    /// });
    /// let mut func = consumer.into_fn();
    /// func(&5);
    /// assert_eq!(*log.lock().unwrap(), vec![5]);
    /// ```
    fn into_fn(self) -> impl FnMut(&T)
    where
        Self: Sized + 'static,
    {
        let mut consumer = self;
        move |t| consumer.accept(t)
    }

    /// Convert to ConsumerOnce
    ///
    /// **⚠️ Consumes `self`**: The original consumer will be unavailable after calling this method.
    ///
    /// Converts a reusable stateful consumer to a one-time consumer that consumes itself on use.
    /// This enables passing `StatefulConsumer` to functions that require `ConsumerOnce`.
    ///
    /// # Returns
    ///
    /// Returns a `BoxConsumerOnce<T>`
    ///
    /// # Examples
    ///
    /// ```rust
    ///
    /// fn takes_once<C: ConsumerOnce<i32>>(consumer: C, value: &i32) {
    ///     consumer.accept(value);
    /// }
    ///
    /// let consumer = BoxStatefulConsumer::new(|x: &i32| println!("{}", x));
    /// takes_once(consumer.into_once(), &5);
    /// ```
    fn into_once(self) -> BoxConsumerOnce<T>
    where
        Self: Sized + 'static,
        T: 'static,
    {
        BoxConsumerOnce::new(move |t| {
            let mut consumer = self;
            consumer.accept(t);
        })
    }

    /// Convert to BoxStatefulConsumer
    ///
    /// **⚠️ Requires Clone**: The original consumer must implement Clone.
    ///
    /// Converts the current consumer to `BoxStatefulConsumer<T>` by cloning it first.
    ///
    /// # Ownership
    ///
    /// This method does **not consume** the consumer. It clones the consumer and
    /// then converts the clone to `BoxStatefulConsumer<T>`. The original consumer remains
    /// available after calling this method.
    ///
    /// # Return Value
    ///
    /// Returns the wrapped `BoxStatefulConsumer<T>` from the clone
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{Consumer, ArcStatefulConsumer};
    /// use std::sync::{Arc, Mutex};
    ///
    /// let log = Arc::new(Mutex::new(Vec::new()));
    /// let l = log.clone();
    /// let consumer = ArcStatefulConsumer::new(move |x: &i32| {
    ///     l.lock().unwrap().push(*x);
    /// });
    /// let mut box_consumer = consumer.to_box();
    /// box_consumer.accept(&5);
    /// assert_eq!(*log.lock().unwrap(), vec![5]);
    /// // Original consumer still usable
    /// consumer.accept(&3);
    /// assert_eq!(*log.lock().unwrap(), vec![5, 3]);
    /// ```
    fn to_box(&self) -> BoxStatefulConsumer<T>
    where
        Self: Sized + Clone + 'static,
        T: 'static,
    {
        self.clone().into_box()
    }

    /// Convert to RcStatefulConsumer
    ///
    /// **⚠️ Requires Clone**: The original consumer must implement Clone.
    ///
    /// Converts the current consumer to `RcStatefulConsumer<T>` by cloning it first.
    ///
    /// # Ownership
    ///
    /// This method does **not consume** the consumer. It clones the consumer and
    /// then converts the clone to `RcStatefulConsumer<T>`. The original consumer remains
    /// available after calling this method.
    ///
    /// # Return Value
    ///
    /// Returns the wrapped `RcStatefulConsumer<T>` from the clone
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{Consumer, ArcStatefulConsumer};
    /// use std::sync::{Arc, Mutex};
    ///
    /// let log = Arc::new(Mutex::new(Vec::new()));
    /// let l = log.clone();
    /// let consumer = ArcStatefulConsumer::new(move |x: &i32| {
    ///     l.lock().unwrap().push(*x);
    /// });
    /// let mut rc_consumer = consumer.to_rc();
    /// rc_consumer.accept(&5);
    /// assert_eq!(*log.lock().unwrap(), vec![5]);
    /// // Original consumer still usable
    /// consumer.accept(&3);
    /// assert_eq!(*log.lock().unwrap(), vec![5, 3]);
    /// ```
    fn to_rc(&self) -> RcStatefulConsumer<T>
    where
        Self: Sized + Clone + 'static,
        T: 'static,
    {
        self.clone().into_rc()
    }

    /// Convert to ArcStatefulConsumer
    ///
    /// **⚠️ Requires Clone + Send**: The original consumer must implement
    /// Clone + Send.
    ///
    /// Converts the current consumer to `ArcStatefulConsumer<T>` by cloning it first.
    ///
    /// # Ownership
    ///
    /// This method does **not consume** the consumer. It clones the consumer and
    /// then converts the clone to `ArcStatefulConsumer<T>`. The original consumer remains
    /// available after calling this method.
    ///
    /// # Return Value
    ///
    /// Returns the wrapped `ArcStatefulConsumer<T>` from the clone
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{Consumer, RcStatefulConsumer};
    /// use std::rc::Rc;
    /// use std::cell::RefCell;
    ///
    /// let log = Rc::new(RefCell::new(Vec::new()));
    /// let l = log.clone();
    /// let consumer = RcStatefulConsumer::new(move |x: &i32| {
    ///     l.borrow_mut().push(*x);
    /// });
    /// let mut arc_consumer = consumer.to_arc();
    /// arc_consumer.accept(&5);
    /// assert_eq!(*log.borrow(), vec![5]);
    /// // Original consumer still usable
    /// consumer.accept(&3);
    /// assert_eq!(*log.borrow(), vec![5, 3]);
    /// ```
    fn to_arc(&self) -> ArcStatefulConsumer<T>
    where
        Self: Sized + Clone + Send + 'static,
        T: 'static,
    {
        self.clone().into_arc()
    }

    /// Convert to closure
    ///
    /// **⚠️ Requires Clone**: The original consumer must implement Clone.
    ///
    /// Converts the consumer to a closure that can be used directly in standard
    /// library functions requiring `FnMut`.
    ///
    /// # Ownership
    ///
    /// This method does **not consume** the consumer. It clones the consumer and
    /// then converts the clone to a closure. The original consumer remains
    /// available after calling this method.
    ///
    /// # Return Value
    ///
    /// Returns a closure implementing `FnMut(&T)` from the clone
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{Consumer, BoxStatefulConsumer};
    /// use std::sync::{Arc, Mutex};
    ///
    /// let log = Arc::new(Mutex::new(Vec::new()));
    /// let l = log.clone();
    /// let consumer = BoxStatefulConsumer::new(move |x: &i32| {
    ///     l.lock().unwrap().push(*x);
    /// });
    /// let mut func = consumer.to_fn();
    /// func(&5);
    /// assert_eq!(*log.lock().unwrap(), vec![5]);
    /// // Original consumer still usable
    /// consumer.accept(&3);
    /// assert_eq!(*log.lock().unwrap(), vec![5, 3]);
    /// ```
    fn to_fn(&self) -> impl FnMut(&T)
    where
        Self: Sized + Clone + 'static,
    {
        self.clone().into_fn()
    }

    /// Convert to ConsumerOnce without consuming self
    ///
    /// **⚠️ Requires Clone**: This method requires `Self` to implement `Clone`.
    /// Clones the current consumer and converts the clone to a one-time consumer.
    ///
    /// # Returns
    ///
    /// Returns a `BoxConsumerOnce<T>`
    ///
    /// # Examples
    ///
    /// ```rust
    ///
    /// fn takes_once<C: ConsumerOnce<i32>>(consumer: C, value: &i32) {
    ///     consumer.accept(value);
    /// }
    ///
    /// let consumer = BoxStatefulConsumer::new(|x: &i32| println!("{}", x));
    /// takes_once(consumer.to_once(), &5);
    /// ```
    fn to_once(&self) -> BoxConsumerOnce<T>
    where
        Self: Clone + 'static,
        T: 'static,
    {
        self.clone().into_once()
    }
}

// ============================================================================
// 2. BoxStatefulConsumer - Single Ownership Implementation
// ============================================================================

/// BoxStatefulConsumer struct
///
/// Consumer implementation based on `Box<dyn FnMut(&T)>` for single ownership
/// scenarios. When sharing is not needed, this is the simplest and most
/// efficient consumer type.
///
/// # Features
///
/// - **Single Ownership**: Not cloneable, transfers ownership when used
/// - **Zero Overhead**: No reference counting or lock overhead
/// - **Mutable State**: Can modify captured environment through `FnMut`
/// - **Builder Pattern**: Method chaining naturally consumes `self`
///
/// # Use Cases
///
/// Choose `BoxStatefulConsumer` when:
/// - Consumer is used only once or in a linear flow
/// - Building pipelines where ownership flows naturally
/// - No need to share consumers across contexts
/// - Performance critical and cannot accept sharing overhead
///
/// # Performance
///
/// `BoxStatefulConsumer` has the best performance among the three consumer types:
/// - No reference counting overhead
/// - No lock acquisition or runtime borrowing checks
/// - Direct function calls through vtable
/// - Minimal memory footprint (single pointer)
///
/// # Examples
///
/// ```rust
/// use qubit_function::{Consumer, BoxStatefulConsumer};
/// use std::sync::{Arc, Mutex};
///
/// let log = Arc::new(Mutex::new(Vec::new()));
/// let l = log.clone();
/// let mut consumer = BoxStatefulConsumer::new(move |x: &i32| {
///     l.lock().unwrap().push(*x);
/// });
/// consumer.accept(&5);
/// assert_eq!(*log.lock().unwrap(), vec![5]);
/// ```
///
/// # Author
///
/// Haixing Hu
pub struct BoxStatefulConsumer<T> {
    function: Box<dyn FnMut(&T)>,
    name: Option<String>,
}

impl<T> BoxStatefulConsumer<T> {
    // Generates: new(), new_with_name(), name(), set_name(), noop()
    impl_consumer_common_methods!(BoxStatefulConsumer<T>, (FnMut(&T) + 'static), |f| Box::new(
        f
    ));

    // Generates: when() and and_then() methods that consume self
    impl_box_consumer_methods!(
        BoxStatefulConsumer<T>,
        BoxConditionalStatefulConsumer,
        StatefulConsumer
    );
}

impl<T> StatefulConsumer<T> for BoxStatefulConsumer<T> {
    fn accept(&mut self, value: &T) {
        (self.function)(value)
    }

    // Generates: into_box(), into_rc(), into_fn(), into_once()
    impl_box_conversions!(
        BoxStatefulConsumer<T>,
        RcStatefulConsumer,
        FnMut(&T),
        BoxConsumerOnce
    );
}

// Use macro to generate Debug and Display implementations
impl_consumer_debug_display!(BoxStatefulConsumer<T>);

// ============================================================================
// 3. RcStatefulConsumer - Single-Threaded Shared Ownership Implementation
// ============================================================================

/// RcStatefulConsumer struct
///
/// Consumer implementation based on `Rc<RefCell<dyn FnMut(&T)>>` for
/// single-threaded shared ownership scenarios. This consumer provides the
/// benefits of shared ownership without the overhead of thread safety.
///
/// # Features
///
/// - **Shared Ownership**: Cloneable through `Rc`, allowing multiple owners
/// - **Single-Threaded**: Not thread-safe, cannot be sent across threads
/// - **Interior Mutability**: Uses `RefCell` for runtime borrowing checks
/// - **No Lock Overhead**: More efficient than `ArcStatefulConsumer` for single-threaded
///   use
/// - **Non-Consuming API**: `and_then` borrows `&self`, original object remains
///   usable
///
/// # Use Cases
///
/// Choose `RcStatefulConsumer` when:
/// - Need to share consumers within a single thread
/// - Thread safety is not needed
/// - Performance is important (avoid lock overhead)
/// - UI event handling in single-threaded frameworks
/// - Building complex single-threaded state machines
///
/// # Performance Considerations
///
/// `RcStatefulConsumer` performs better than `ArcStatefulConsumer` in single-threaded scenarios:
/// - **Non-Atomic Counting**: clone/drop is cheaper than `Arc`
/// - **No Lock Overhead**: `RefCell` uses runtime checks, no locks
/// - **Better Cache Locality**: No atomic operations means better CPU cache
///   behavior
///
/// But still has slight overhead compared to `BoxStatefulConsumer`:
/// - **Reference Counting**: Non-atomic but still exists
/// - **Runtime Borrowing Checks**: `RefCell` checks at runtime
///
/// # Safety
///
/// `RcStatefulConsumer` is not thread-safe and does not implement `Send` or `Sync`.
/// Attempting to send it to another thread will result in a compilation error.
/// For thread-safe sharing, use `ArcStatefulConsumer` instead.
///
/// # Examples
///
/// ```rust
/// use qubit_function::{Consumer, RcStatefulConsumer};
/// use std::rc::Rc;
/// use std::cell::RefCell;
///
/// let log = Rc::new(RefCell::new(Vec::new()));
/// let l = log.clone();
/// let mut consumer = RcStatefulConsumer::new(move |x: &i32| {
///     l.borrow_mut().push(*x * 2);
/// });
/// let mut clone = consumer.clone();
///
/// consumer.accept(&5);
/// assert_eq!(*log.borrow(), vec![10]);
/// ```
///
/// # Author
///
/// Haixing Hu
pub struct RcStatefulConsumer<T> {
    function: Rc<RefCell<dyn FnMut(&T)>>,
    name: Option<String>,
}

impl<T> RcStatefulConsumer<T> {
    // Generates: new(), new_with_name(), name(), set_name(), noop()
    impl_consumer_common_methods!(RcStatefulConsumer<T>, (FnMut(&T) + 'static), |f| Rc::new(
        RefCell::new(f)
    ));

    // Generates: when() and and_then() methods that borrow &self (Rc can clone)
    impl_shared_consumer_methods!(
        RcStatefulConsumer<T>,
        RcConditionalStatefulConsumer,
        into_rc,
        StatefulConsumer,
        'static
    );
}

impl<T> StatefulConsumer<T> for RcStatefulConsumer<T> {
    fn accept(&mut self, value: &T) {
        (self.function.borrow_mut())(value)
    }

    // Use macro to implement conversion methods
    impl_rc_conversions!(
        RcStatefulConsumer<T>,
        BoxStatefulConsumer,
        BoxConsumerOnce,
        FnMut(t: &T)
    );
}

// Use macro to generate Clone implementation
impl_consumer_clone!(RcStatefulConsumer<T>);

// Use macro to generate Debug and Display implementations
impl_consumer_debug_display!(RcStatefulConsumer<T>);

// ============================================================================
// 4. ArcStatefulConsumer - Thread-Safe Shared Ownership Implementation
// ============================================================================

/// ArcStatefulConsumer struct
///
/// Consumer implementation based on `Arc<Mutex<dyn FnMut(&T) + Send>>` for
/// thread-safe shared ownership scenarios. This consumer can be safely cloned
/// and shared across multiple threads.
///
/// # Features
///
/// - **Shared Ownership**: Cloneable through `Arc`, allowing multiple owners
/// - **Thread Safety**: Implements `Send + Sync`, safe for concurrent use
/// - **Interior Mutability**: Uses `Mutex` for safe mutable access
/// - **Non-Consuming API**: `and_then` borrows `&self`, original object remains
///   usable
/// - **Cross-Thread Sharing**: Can be sent to other threads and used
///
/// # Use Cases
///
/// Choose `ArcStatefulConsumer` when:
/// - Need to share consumers across multiple threads
/// - Concurrent task processing (e.g., thread pools)
/// - Using the same consumer in multiple places simultaneously
/// - Need thread safety (Send + Sync)
///
/// # Performance Considerations
///
/// `ArcStatefulConsumer` has some performance overhead compared to `BoxStatefulConsumer`:
/// - **Reference Counting**: Atomic operations on clone/drop
/// - **Mutex Locking**: Each `accept` call requires lock acquisition
/// - **Lock Contention**: High concurrency may cause contention
///
/// These overheads are necessary for safe concurrent access. If thread safety
/// is not needed, consider using `RcStatefulConsumer` for less single-threaded sharing
/// overhead.
///
/// # Examples
///
/// ```rust
/// use qubit_function::{Consumer, ArcStatefulConsumer};
/// use std::sync::{Arc, Mutex};
///
/// let log = Arc::new(Mutex::new(Vec::new()));
/// let l = log.clone();
/// let mut consumer = ArcStatefulConsumer::new(move |x: &i32| {
///     l.lock().unwrap().push(*x * 2);
/// });
/// let mut clone = consumer.clone();
///
/// consumer.accept(&5);
/// assert_eq!(*log.lock().unwrap(), vec![10]);
/// ```
///
/// # Author
///
/// Haixing Hu
pub struct ArcStatefulConsumer<T> {
    function: Arc<Mutex<dyn FnMut(&T) + Send>>,
    name: Option<String>,
}

impl<T> ArcStatefulConsumer<T> {
    // Generates: new(), new_with_name(), name(), set_name(), noop()
    impl_consumer_common_methods!(ArcStatefulConsumer<T>, (FnMut(&T) + Send + 'static), |f| {
        Arc::new(Mutex::new(f))
    });

    // Generates: when() and and_then() methods that borrow &self (Arc can clone)
    impl_shared_consumer_methods!(
        ArcStatefulConsumer<T>,
        ArcConditionalStatefulConsumer,
        into_arc,
        StatefulConsumer,
        Send + Sync + 'static
    );
}

impl<T> StatefulConsumer<T> for ArcStatefulConsumer<T> {
    fn accept(&mut self, value: &T) {
        (self.function.lock())(value)
    }

    // Use macro to implement conversion methods
    impl_arc_conversions!(
        ArcStatefulConsumer<T>,
        BoxStatefulConsumer,
        RcStatefulConsumer,
        BoxConsumerOnce,
        FnMut(t: &T)
    );
}

// Use macro to generate Clone implementation
impl_consumer_clone!(ArcStatefulConsumer<T>);

// Use macro to generate Debug and Display implementations
impl_consumer_debug_display!(ArcStatefulConsumer<T>);

// ============================================================================
// 5. Implement Consumer trait for closures
// ============================================================================

// Implement Consumer for all FnMut(&T)
impl_closure_trait!(
    StatefulConsumer<T>,
    accept,
    BoxConsumerOnce,
    FnMut(value: &T)
);

// ============================================================================
// 6. Extension methods for closures
// ============================================================================

/// Extension trait providing consumer composition methods for closures
///
/// Provides `and_then` and other composition methods for all closures
/// implementing `FnMut(&T)`, allowing direct method chaining on closures
/// without explicit wrapper types.
///
/// # Design Philosophy
///
/// This trait allows closures to be naturally composed using method syntax,
/// similar to iterator combinators. Composition methods consume the closure and
/// return `BoxStatefulConsumer<T>`, which can continue chaining.
///
/// # Features
///
/// - **Natural Syntax**: Direct method chaining on closures
/// - **Returns BoxStatefulConsumer**: Composition results in `BoxStatefulConsumer<T>`, can
///   continue chaining
/// - **Zero Cost**: No overhead when composing closures
/// - **Automatic Implementation**: All `FnMut(&T)` closures automatically get
///   these methods
///
/// # Examples
///
/// ```rust
/// use qubit_function::{Consumer, FnStatefulConsumerOps};
/// use std::sync::{Arc, Mutex};
///
/// let log = Arc::new(Mutex::new(Vec::new()));
/// let l1 = log.clone();
/// let l2 = log.clone();
/// let mut chained = (move |x: &i32| {
///     l1.lock().unwrap().push(*x * 2);
/// }).and_then(move |x: &i32| {
///     l2.lock().unwrap().push(*x + 10);
/// });
/// chained.accept(&5);
/// assert_eq!(*log.lock().unwrap(), vec![10, 15]);
/// // (5 * 2), (5 + 10)
/// ```
///
/// # Author
///
/// Haixing Hu
pub trait FnStatefulConsumerOps<T>: FnMut(&T) + Sized {
    /// Sequentially chain another consumer
    ///
    /// Returns a new consumer that executes the current operation first, then the
    /// next operation. Consumes the current closure and returns `BoxStatefulConsumer<T>`.
    ///
    /// # Type Parameters
    ///
    /// * `C` - Type of the next consumer
    ///
    /// # Parameters
    ///
    /// * `next` - Consumer to execute after the current operation. **Note: This
    ///   parameter is passed by value and will transfer ownership.** If you need
    ///   to preserve the original consumer, clone it first (if it implements
    ///   `Clone`). Can be:
    ///   - A closure: `|x: &T|`
    ///   - A `BoxStatefulConsumer<T>`
    ///   - An `RcStatefulConsumer<T>`
    ///   - An `ArcStatefulConsumer<T>`
    ///   - Any type implementing `Consumer<T>`
    ///
    /// # Return Value
    ///
    /// Returns a combined `BoxStatefulConsumer<T>`
    ///
    /// # Examples
    ///
    /// ## Direct value passing (ownership transfer)
    ///
    /// ```rust
    /// use qubit_function::{Consumer, FnStatefulConsumerOps, BoxStatefulConsumer};
    /// use std::sync::{Arc, Mutex};
    ///
    /// let log = Arc::new(Mutex::new(Vec::new()));
    /// let l1 = log.clone();
    /// let l2 = log.clone();
    /// let second = BoxStatefulConsumer::new(move |x: &i32| {
    ///     l2.lock().unwrap().push(*x + 10);
    /// });
    ///
    /// // second is moved here
    /// let mut chained = (move |x: &i32| {
    ///     l1.lock().unwrap().push(*x * 2);
    /// }).and_then(second);
    ///
    /// chained.accept(&5);
    /// assert_eq!(*log.lock().unwrap(), vec![10, 15]);
    /// // second.accept(&3); // Would not compile - moved
    /// ```
    ///
    /// ## Preserving original with clone
    ///
    /// ```rust
    /// use qubit_function::{Consumer, FnStatefulConsumerOps, BoxStatefulConsumer};
    /// use std::sync::{Arc, Mutex};
    ///
    /// let log = Arc::new(Mutex::new(Vec::new()));
    /// let l1 = log.clone();
    /// let l2 = log.clone();
    /// let second = BoxStatefulConsumer::new(move |x: &i32| {
    ///     l2.lock().unwrap().push(*x + 10);
    /// });
    ///
    /// // Clone to preserve original
    /// let mut chained = (move |x: &i32| {
    ///     l1.lock().unwrap().push(*x * 2);
    /// }).and_then(second.clone());
    ///
    /// chained.accept(&5);
    /// assert_eq!(*log.lock().unwrap(), vec![10, 15]);
    ///
    /// // Original still usable
    /// second.accept(&3);
    /// assert_eq!(*log.lock().unwrap(), vec![10, 15, 13]);
    /// ```
    fn and_then<C>(self, next: C) -> BoxStatefulConsumer<T>
    where
        Self: 'static,
        C: StatefulConsumer<T> + 'static,
        T: 'static,
    {
        let mut first = self;
        let mut second = next;
        BoxStatefulConsumer::new(move |t| {
            first(t);
            second.accept(t);
        })
    }
}

/// Implement FnStatefulConsumerOps for all closure types
impl<T, F> FnStatefulConsumerOps<T> for F where F: FnMut(&T) {}

// ============================================================================
// 7. BoxConditionalStatefulConsumer - Box-based Conditional Consumer
// ============================================================================

/// BoxConditionalStatefulConsumer struct
///
/// A conditional consumer that only executes when a predicate is satisfied.
/// Uses `BoxStatefulConsumer` and `BoxPredicate` for single ownership semantics.
///
/// This type is typically created by calling `BoxStatefulConsumer::when()` and is
/// designed to work with the `or_else()` method to create if-then-else logic.
///
/// # Features
///
/// - **Single Ownership**: Not cloneable, consumes `self` on use
/// - **Conditional Execution**: Only consumes when predicate returns `true`
/// - **Chainable**: Can add `or_else` branch to create if-then-else logic
/// - **Implements Consumer**: Can be used anywhere a `Consumer` is expected
///
/// # Examples
///
/// ## Basic Conditional Execution
///
/// ```rust
/// use qubit_function::{Consumer, BoxStatefulConsumer};
/// use std::sync::{Arc, Mutex};
///
/// let log = Arc::new(Mutex::new(Vec::new()));
/// let l = log.clone();
/// let consumer = BoxStatefulConsumer::new(move |x: &i32| {
///     l.lock().unwrap().push(*x);
/// });
/// let mut conditional = consumer.when(|x: &i32| *x > 0);
///
/// conditional.accept(&5);
/// assert_eq!(*log.lock().unwrap(), vec![5]); // Executed
///
/// conditional.accept(&-5);
/// assert_eq!(*log.lock().unwrap(), vec![5]); // Not executed
/// ```
///
/// ## With or_else Branch
///
/// ```rust
/// use qubit_function::{Consumer, BoxStatefulConsumer};
/// use std::sync::{Arc, Mutex};
///
/// let log = Arc::new(Mutex::new(Vec::new()));
/// let l1 = log.clone();
/// let l2 = log.clone();
/// let mut consumer = BoxStatefulConsumer::new(move |x: &i32| {
///     l1.lock().unwrap().push(*x);
/// })
/// .when(|x: &i32| *x > 0)
/// .or_else(move |x: &i32| {
///     l2.lock().unwrap().push(-*x);
/// });
///
/// consumer.accept(&5);
/// assert_eq!(*log.lock().unwrap(), vec![5]); // when branch executed
///
/// consumer.accept(&-5);
/// assert_eq!(*log.lock().unwrap(), vec![5, 5]); // or_else branch executed
/// ```
///
/// # Author
///
/// Haixing Hu
pub struct BoxConditionalStatefulConsumer<T> {
    consumer: BoxStatefulConsumer<T>,
    predicate: BoxPredicate<T>,
}

// Use macro to generate and_then and or_else methods
impl_box_conditional_consumer!(
    BoxConditionalStatefulConsumer<T>,
    BoxStatefulConsumer,
    StatefulConsumer
);

impl<T> StatefulConsumer<T> for BoxConditionalStatefulConsumer<T> {
    fn accept(&mut self, value: &T) {
        if self.predicate.test(value) {
            self.consumer.accept(value);
        }
    }

    // Generates: into_box(), into_rc(), into_fn()
    impl_conditional_consumer_conversions!(BoxStatefulConsumer<T>, RcStatefulConsumer, FnMut);
}

// Use macro to generate Debug and Display implementations
impl_conditional_consumer_debug_display!(BoxConditionalStatefulConsumer<T>);

// ============================================================================
// 8. ArcConditionalStatefulConsumer - Arc-based Conditional Consumer
// ============================================================================

/// ArcConditionalStatefulConsumer struct
///
/// A thread-safe conditional consumer that only executes when a predicate is
/// satisfied. Uses `ArcStatefulConsumer` and `ArcPredicate` for shared ownership across
/// threads.
///
/// This type is typically created by calling `ArcStatefulConsumer::when()` and is
/// designed to work with the `or_else()` method to create if-then-else logic.
///
/// # Features
///
/// - **Shared Ownership**: Cloneable via `Arc`, multiple owners allowed
/// - **Thread-Safe**: Implements `Send + Sync`, safe for concurrent use
/// - **Conditional Execution**: Only consumes when predicate returns `true`
/// - **Chainable**: Can add `or_else` branch to create if-then-else logic
///
/// # Examples
///
/// ```rust
/// use qubit_function::{Consumer, ArcStatefulConsumer};
/// use std::sync::{Arc, Mutex};
///
/// let log = Arc::new(Mutex::new(Vec::new()));
/// let l = log.clone();
/// let conditional = ArcStatefulConsumer::new(move |x: &i32| {
///     l.lock().unwrap().push(*x);
/// })
/// .when(|x: &i32| *x > 0);
///
/// let conditional_clone = conditional.clone();
///
/// let mut value = 5;
/// let mut m = conditional;
/// m.accept(&value);
/// assert_eq!(*log.lock().unwrap(), vec![5]);
/// ```
///
/// # Author
///
/// Haixing Hu
pub struct ArcConditionalStatefulConsumer<T> {
    consumer: ArcStatefulConsumer<T>,
    predicate: ArcPredicate<T>,
}

// Use macro to generate and_then and or_else methods
impl_shared_conditional_consumer!(
    ArcConditionalStatefulConsumer<T>,
    ArcStatefulConsumer,
    StatefulConsumer,
    into_arc,
    Send + Sync + 'static
);

impl<T> StatefulConsumer<T> for ArcConditionalStatefulConsumer<T> {
    fn accept(&mut self, value: &T) {
        if self.predicate.test(value) {
            self.consumer.accept(value);
        }
    }

    // Generates: into_box(), into_rc(), into_fn()
    impl_conditional_consumer_conversions!(BoxStatefulConsumer<T>, RcStatefulConsumer, FnMut);
}

// Use macro to generate Clone implementation
impl_conditional_consumer_clone!(ArcConditionalStatefulConsumer<T>);

// Use macro to generate Debug and Display implementations
impl_conditional_consumer_debug_display!(ArcConditionalStatefulConsumer<T>);

// ============================================================================
// 9. RcConditionalStatefulConsumer - Rc-based Conditional Consumer
// ============================================================================

/// RcConditionalStatefulConsumer struct
///
/// A single-threaded conditional consumer that only executes when a predicate is
/// satisfied. Uses `RcStatefulConsumer` and `RcPredicate` for shared ownership within a
/// single thread.
///
/// This type is typically created by calling `RcStatefulConsumer::when()` and is
/// designed to work with the `or_else()` method to create if-then-else logic.
///
/// # Features
///
/// - **Shared Ownership**: Cloneable via `Rc`, multiple owners allowed
/// - **Single-Threaded**: Not thread-safe, cannot be sent across threads
/// - **Conditional Execution**: Only consumes when predicate returns `true`
/// - **No Lock Overhead**: More efficient than `ArcConditionalStatefulConsumer`
///
/// # Examples
///
/// ```rust
/// use qubit_function::{Consumer, RcStatefulConsumer};
/// use std::rc::Rc;
/// use std::cell::RefCell;
///
/// let log = Rc::new(RefCell::new(Vec::new()));
/// let l = log.clone();
/// let conditional = RcStatefulConsumer::new(move |x: &i32| {
///     l.borrow_mut().push(*x);
/// })
/// .when(|x: &i32| *x > 0);
///
/// let conditional_clone = conditional.clone();
///
/// let mut value = 5;
/// let mut m = conditional;
/// m.accept(&value);
/// assert_eq!(*log.borrow(), vec![5]);
/// ```
///
/// # Author
///
/// Haixing Hu
pub struct RcConditionalStatefulConsumer<T> {
    consumer: RcStatefulConsumer<T>,
    predicate: RcPredicate<T>,
}

// Use macro to generate and_then and or_else methods
impl_shared_conditional_consumer!(
    RcConditionalStatefulConsumer<T>,
    RcStatefulConsumer,
    StatefulConsumer,
    into_rc,
    'static
);

impl<T> StatefulConsumer<T> for RcConditionalStatefulConsumer<T> {
    fn accept(&mut self, value: &T) {
        if self.predicate.test(value) {
            self.consumer.accept(value);
        }
    }

    // Generates: into_box(), into_rc(), into_fn()
    impl_conditional_consumer_conversions!(BoxStatefulConsumer<T>, RcStatefulConsumer, FnMut);
}

// Use macro to generate Clone implementation
impl_conditional_consumer_clone!(RcConditionalStatefulConsumer<T>);

// Use macro to generate Debug and Display implementations
impl_conditional_consumer_debug_display!(RcConditionalStatefulConsumer<T>);