qubit-function 0.16.0

// =============================================================================
//    Copyright (c) 2025 - 2026 Haixing Hu.
//
//    SPDX-License-Identifier: Apache-2.0
//
//    Licensed under the Apache License, Version 2.0.
// =============================================================================
//! Defines the `ArcConditionalStatefulMutatingFunction` public type.

use {
    crate::ArcPredicate,
    crate::ArcStatefulMutatingFunction,
    crate::Predicate,
    crate::StatefulMutatingFunction,
    crate::functions::macros::impl_conditional_function_clone,
    crate::functions::macros::impl_conditional_function_debug_display,
    crate::functions::macros::impl_shared_conditional_function,
};

// ============================================================================
// ArcConditionalStatefulMutatingFunction - Arc-based Conditional Stateful
// Mutating Function
// ============================================================================

/// ArcConditionalStatefulMutatingFunction struct
///
/// A thread-safe conditional function that only executes when a predicate is
/// satisfied. Uses `ArcStatefulMutatingFunction` and `ArcPredicate` for shared
/// ownership across threads.
///
/// This type is typically created by calling
/// `ArcStatefulMutatingFunction::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 transforms when predicate returns `true`
/// - **Chainable**: Can add `or_else` branch to create if-then-else logic
///
/// # Examples
///
/// ```rust
/// use qubit_function::{StatefulMutatingFunction, ArcStatefulMutatingFunction};
///
/// let double = ArcStatefulMutatingFunction::new(|x: &mut i32| {
///     *x *= 2;
///     *x
/// });
/// let identity = ArcStatefulMutatingFunction::<i32, i32>::identity();
/// let mut conditional = double.when(|x: &i32| *x > 0).or_else(identity);
///
/// let mut conditional_clone = conditional.clone();
///
/// let mut positive = 5;
/// let mut negative = -5;
/// assert_eq!(conditional.apply(&mut positive), 10);
/// assert_eq!(conditional_clone.apply(&mut negative), -5);
/// ```
///
/// # Locking and reentrancy
///
/// When the wrapped stateful callback executes, the underlying
/// `parking_lot::Mutex` remains locked until that callback returns.
/// Synchronous re-entry through the same shared state deadlocks. The mutex is
/// not poisoned after a panic, and mutations completed before a panic are not
/// rolled back.
#[must_use = "callback wrappers do nothing unless stored or invoked"]
pub struct ArcConditionalStatefulMutatingFunction<T, R> {
    /// The wrapped callback implementation.
    pub(super) function: ArcStatefulMutatingFunction<T, R>,
    /// The predicate controlling conditional execution.
    pub(super) predicate: ArcPredicate<T>,
}

// Use macro to generate conditional function implementations
impl_shared_conditional_function!(
    ArcConditionalStatefulMutatingFunction<T, R>,
    ArcStatefulMutatingFunction,
    StatefulMutatingFunction,
    callback_bounds = (Send + 'static)
);

// Use macro to generate conditional function clone implementations
impl_conditional_function_clone!(ArcConditionalStatefulMutatingFunction<T, R>);

// Use macro to generate conditional function debug and display implementations
impl_conditional_function_debug_display!(ArcConditionalStatefulMutatingFunction<T, R>);