qubit-function 0.16.0

Functional programming traits and Box/Rc/Arc adapters for Rust, inspired by Java functional interfaces
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// =============================================================================
//    Copyright (c) 2025 - 2026 Haixing Hu.
//
//    SPDX-License-Identifier: Apache-2.0
//
//    Licensed under the Apache License, Version 2.0.
// =============================================================================
//! Defines the `ArcConsumer` public type.

use {
    crate::ArcConditionalConsumer,
    crate::Predicate,
};
use {
    crate::Consumer,
    crate::consumers::macros::impl_consumer_clone,
    crate::consumers::macros::impl_consumer_common_methods,
    crate::consumers::macros::impl_consumer_debug_display,
    crate::consumers::macros::impl_shared_consumer_methods,
    std::sync::Arc,
};

// ============================================================================
// 4. ArcConsumer - Thread-safe Shared Ownership Implementation
// ============================================================================

/// ArcConsumer struct
///
/// Non-mutating consumer implementation based on `Arc<dyn Fn(&T) + Send +
/// Sync>`, for thread-safe shared ownership scenarios. The wrapper does not
/// need `Mutex` because it only invokes a shared `Fn`.
///
/// # Features
///
/// - **Shared Ownership**: Cloneable through `Arc`, allows multiple owners
/// - **Thread Safe**: Implements `Send + Sync`, can be safely used concurrently
/// - **Lock-free Wrapper**: No Mutex protection needed by the wrapper
/// - **Non-consuming API**: `and_then` borrows `&self`, original object remains
///   usable
///
/// # Use Cases
///
/// Choose `ArcConsumer` when:
/// - Need to share non-mutating consumer across multiple threads
/// - Pure observation operations, such as logging, monitoring, notifications
/// - Need high-concurrency reads with no lock overhead
///
/// # Performance Advantages
///
/// Compared to `ArcStatefulConsumer`, `ArcConsumer` has no Mutex lock overhead,
/// performing better in high-concurrency observation scenarios.
///
/// # Examples
///
/// ```rust
/// use qubit_function::{Consumer, ArcConsumer};
///
/// let consumer = ArcConsumer::new(|x: &i32| {
///     println!("Observed: {}", x);
/// });
/// let clone = consumer.clone();
///
/// consumer.accept(&5);
/// clone.accept(&10);
/// ```
#[must_use = "callback wrappers do nothing unless stored or invoked"]
pub struct ArcConsumer<T> {
    /// The wrapped callback implementation.
    pub(super) function: Arc<dyn Fn(&T) + Send + Sync>,
    /// Diagnostic metadata associated with this callback.
    pub(super) metadata: crate::internal::CallbackMetadata,
}

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

    // Generates: when() and and_then() methods that borrow &self (Arc can
    // clone)
    impl_shared_consumer_methods!(
        ArcConsumer<T>,
        ArcConditionalConsumer,
        ArcPredicate,
        Consumer,
        predicate_bounds = (Send + Sync + 'static),
        chained_bounds = (Send + Sync + 'static)
    );
}

impl<T> Consumer<T> for ArcConsumer<T> {
    #[inline(always)]
    fn accept(&self, value: &T) {
        (self.function)(value)
    }
}

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

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