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.
// =============================================================================
//! # Shared Conditional Consumer Macro
//!
//! Generates `and_then` and `or_else` for shared Arc/Rc conditional consumers.
//! Generated methods borrow `&self` and return a wrapper from the same
//! ownership and statefulness family.
//!
//! # Parameters
//!
//! * `$struct_name<$generics>` - Conditional wrapper type.
//! * `$consumer_type` - Result wrapper type, such as `ArcConsumer`.
//! * `$consumer_trait` - Semantic trait accepted for the additional callback,
//!   such as `Consumer`.
//! * `$callback_bounds` - Storage capabilities required for the additional
//!   callback.
//!
//! # Capability policy
//!
//! | Wrapper family | `callback_bounds` |
//! |----------------|-------------------|
//! | Arc stateless | `Send + Sync + 'static` |
//! | Arc stateful | `Send + 'static` |
//! | Rc stateless/stateful | `'static` |

/// Generates `and_then` and `or_else` for shared Arc/Rc conditional consumers.
///
/// Invoke this macro at module scope. The selected callback bounds reflect
/// how the result wrapper stores its callback: stateless Arc wrappers call
/// through a shared reference and require `Sync`; stateful Arc wrappers call
/// under an outer mutex and require only `Send`.
///
/// # Capability policy
///
/// | Wrapper family | `callback_bounds` |
/// |----------------|-------------------|
/// | Arc stateless | `Send + Sync + 'static` |
/// | Arc stateful | `Send + 'static` |
/// | Rc stateless/stateful | `'static` |
macro_rules! impl_shared_conditional_consumer {
    (@let_consumer Consumer, $name:ident, $value:expr) => {
        let $name = $value;
    };

    (@let_consumer StatefulConsumer, $name:ident, $value:expr) => {
        let mut $name = $value;
    };

    (@let_consumer BiConsumer, $name:ident, $value:expr) => {
        let $name = $value;
    };

    (@let_consumer StatefulBiConsumer, $name:ident, $value:expr) => {
        let mut $name = $value;
    };

    // Single generic parameter - Consumer types
    (
        $struct_name:ident < $t:ident >,
        $consumer_type:ident,
        $consumer_trait:ident,
        callback_bounds = ($($callback_bounds:tt)+)
    ) => {
        impl<$t> $struct_name<$t> {
            /// Chains another consumer in sequence
            ///
            /// Combines the current conditional consumer with another consumer
            /// into a new consumer that implements the following semantics:
            ///
            /// When the returned consumer is called with an argument:
            /// 1. First, it checks the predicate of this conditional consumer
            /// 2. If the predicate is satisfied, it executes the internal
            ///    consumer of this conditional consumer
            /// 3. Then, **regardless of whether the predicate was satisfied**,
            ///    it unconditionally executes the `next` consumer
            ///
            /// In other words, this creates a consumer that conditionally
            /// executes the first action (based on the predicate), and then
            /// always executes the second action.
            ///
            /// # Parameters
            ///
            /// * `next` - The next consumer to execute (always executed)
            ///
            /// # Returns
            ///
            /// Returns a new combined consumer
            ///
            /// # Examples
            ///
            /// ```rust
            /// use std::sync::atomic::{AtomicI32, Ordering};
            /// use qubit_function::{Consumer, ArcConsumer};
            ///
/// let result = std::sync::Arc::new(AtomicI32::new(0));
/// let result1 = std::sync::Arc::clone(&result);
/// let consumer = ArcConsumer::new(move |x: &i32| {
///     result1.fetch_add(*x, Ordering::SeqCst);
/// });
            ///
/// let consumer2 = consumer.when(|x: &i32| *x > 0);
            ///
/// let result2 = std::sync::Arc::clone(&result);
/// let chained = consumer2.and_then(ArcConsumer::new(move |x: &i32| {
///     result2.fetch_add(2 * (*x), Ordering::SeqCst);
/// }));
            ///
            /// chained.accept(&5);  // result = 5 + (2*5) = 15
            /// result.store(0, Ordering::SeqCst);  // reset
            /// chained.accept(&-5); // result = 0 + (2*-5) = -10 (not -15!)
            /// assert_eq!(result.load(Ordering::SeqCst), -10);
            /// ```
            pub fn and_then<C>(&self, next: C) -> $consumer_type<$t>
            where
                $t: 'static,
                C: $consumer_trait<$t> + $($callback_bounds)+,
            {
                let first_predicate = self.predicate.clone();
                impl_shared_conditional_consumer!(@let_consumer $consumer_trait, first_consumer, self.consumer.clone());
                impl_shared_conditional_consumer!(@let_consumer $consumer_trait, next, next);
                $consumer_type::new(move |t: &$t| {
                    if first_predicate.test(t) {
                        first_consumer.accept(t);
                    }
                    next.accept(t);
                })
            }

            /// Adds an else branch
            ///
            /// Executes the original consumer when the condition is satisfied, otherwise
            /// executes else_consumer.
            ///
            /// # Parameters
            ///
            /// * `else_consumer` - The consumer for the else branch
            ///
            /// # Returns
            ///
            /// Returns a new consumer with if-then-else logic
            pub fn or_else<C>(&self, else_consumer: C) -> $consumer_type<$t>
            where
                $t: 'static,
                C: $consumer_trait<$t> + $($callback_bounds)+,
            {
                let predicate = self.predicate.clone();
                impl_shared_conditional_consumer!(@let_consumer $consumer_trait, then_consumer, self.consumer.clone());
                impl_shared_conditional_consumer!(@let_consumer $consumer_trait, else_consumer, else_consumer);
                $consumer_type::new(move |t: &$t| {
                    if predicate.test(t) {
                        then_consumer.accept(t);
                    } else {
                        else_consumer.accept(t);
                    }
                })
            }
        }
    };

    // Two generic parameters - BiConsumer types
    (
        $struct_name:ident < $t:ident, $u:ident >,
        $consumer_type:ident,
        $consumer_trait:ident,
        callback_bounds = ($($callback_bounds:tt)+)
    ) => {
        impl<$t, $u> $struct_name<$t, $u> {
            /// Chains another bi-consumer in sequence
            ///
            /// Combines the current conditional bi-consumer with another
            /// bi-consumer into a new bi-consumer that implements the
            /// following semantics:
            ///
            /// When the returned bi-consumer is called with two arguments:
            /// 1. First, it checks the predicate of this conditional
            ///    bi-consumer
            /// 2. If the predicate is satisfied, it executes the internal
            ///    bi-consumer of this conditional bi-consumer
            /// 3. Then, **regardless of whether the predicate was
            ///    satisfied**, it unconditionally executes the `next`
            ///    bi-consumer
            ///
            /// In other words, this creates a bi-consumer that conditionally
            /// executes the first action (based on the predicate), and then
            /// always executes the second action.
            ///
            /// # Parameters
            ///
            /// * `next` - The next bi-consumer to execute (always executed)
            ///
            /// # Returns
            ///
            /// Returns a new combined bi-consumer
            ///
            /// # Examples
            ///
            /// ```rust
/// use std::sync::atomic::{AtomicI32, Ordering};
/// use std::sync::Arc;
/// use qubit_function::{BiConsumer, ArcBiConsumer};
///
/// let result = Arc::new(AtomicI32::new(0));
/// let result1 = std::sync::Arc::clone(&result);
/// let consumer = ArcBiConsumer::new(move |x: &i32, y: &i32| {
///     result1.fetch_add(*x + *y, Ordering::SeqCst);
/// });
            ///
/// let consumer2 = consumer.when(|x: &i32, y: &i32| *x > 0 && *y > 0);
/// let result2 = std::sync::Arc::clone(&result);
/// let chained = consumer2.and_then(ArcBiConsumer::new(move |x: &i32, y: &i32| {
///     result2.fetch_add(2 * (*x + *y), Ordering::SeqCst);
/// }));
            ///
            /// chained.accept(&5, &3);  // result = (5+3) + 2*(5+3) = 24
            /// result.store(0, Ordering::SeqCst);  // reset
            /// chained.accept(&-5, &3); // result = 0 + 2*(-5+3) = -4 (not -8!)
            /// assert_eq!(result.load(Ordering::SeqCst), -4);
            /// ```
            pub fn and_then<C>(&self, next: C) -> $consumer_type<$t, $u>
            where
                $t: 'static,
                $u: 'static,
                C: $consumer_trait<$t, $u> + $($callback_bounds)+,
            {
                let first_predicate = self.predicate.clone();
                impl_shared_conditional_consumer!(@let_consumer $consumer_trait, first_consumer, self.consumer.clone());
                impl_shared_conditional_consumer!(@let_consumer $consumer_trait, next, next);
                $consumer_type::new(move |t: &$t, u: &$u| {
                    if first_predicate.test(t, u) {
                        first_consumer.accept(t, u);
                    }
                    next.accept(t, u);
                })
            }

            /// Adds an else branch
            ///
            /// Executes the original bi-consumer when the condition is satisfied, otherwise
            /// executes else_consumer.
            ///
            /// # Parameters
            ///
            /// * `else_consumer` - The bi-consumer for the else branch
            ///
            /// # Returns
            ///
            /// Returns a new bi-consumer with if-then-else logic
            pub fn or_else<C>(&self, else_consumer: C) -> $consumer_type<$t, $u>
            where
                $t: 'static,
                $u: 'static,
                C: $consumer_trait<$t, $u> + $($callback_bounds)+,
            {
                let predicate = self.predicate.clone();
                impl_shared_conditional_consumer!(@let_consumer $consumer_trait, then_consumer, self.consumer.clone());
                impl_shared_conditional_consumer!(@let_consumer $consumer_trait, else_consumer, else_consumer);
                $consumer_type::new(move |t: &$t, u: &$u| {
                    if predicate.test(t, u) {
                        then_consumer.accept(t, u);
                    } else {
                        else_consumer.accept(t, u);
                    }
                })
            }
        }
    };
}

pub(crate) use impl_shared_conditional_consumer;