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 `RcConditionalMutatingFunction` public type.

use {
    crate::MutatingFunction,
    crate::Predicate,
    crate::RcMutatingFunction,
    crate::RcPredicate,
    crate::functions::macros::impl_conditional_function_clone,
    crate::functions::macros::impl_conditional_function_debug_display,
    crate::functions::macros::impl_shared_conditional_function,
};

// ============================================================================
// RcConditionalMutatingFunction - Rc-based Conditional Mutating Function
// ============================================================================

/// RcConditionalMutatingFunction struct
///
/// A single-threaded conditional function that only executes when a
/// predicate is satisfied. Uses `RcMutatingFunction` and `RcPredicate` for
/// shared ownership within a single thread.
///
/// This type is typically created by calling `RcMutatingFunction::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 transforms when predicate returns `true`
/// - **Ownership Cost**: `Rc` uses non-atomic reference counting; `Arc` uses
///   atomic reference counting, and neither wrapper locks callback invocation
///
/// # Examples
///
/// ```rust
/// use qubit_function::{MutatingFunction, RcMutatingFunction};
///
/// let double = RcMutatingFunction::new(|x: &mut i32| *x * 2);
/// let identity = RcMutatingFunction::<i32, i32>::identity();
/// let conditional = double.when(|x: &i32| *x > 0).or_else(identity);
///
/// let conditional_clone = conditional.clone();
///
/// let mut positive = 5;
/// assert_eq!(conditional.apply(&mut positive), 10);
/// let mut negative = -5;
/// assert_eq!(conditional_clone.apply(&mut negative), -5);
/// ```
#[must_use = "callback wrappers do nothing unless stored or invoked"]
pub struct RcConditionalMutatingFunction<T, R> {
    /// The wrapped callback implementation.
    pub(super) function: RcMutatingFunction<T, R>,
    /// The predicate controlling conditional execution.
    pub(super) predicate: RcPredicate<T>,
}

// Use macro to generate conditional function implementations
impl_shared_conditional_function!(
    RcConditionalMutatingFunction<T, R>,
    RcMutatingFunction,
    MutatingFunction,
    callback_bounds = ('static)
);

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

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