qubit-function 0.18.2

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

use std::ops::Not;

use super::ALWAYS_FALSE_NAME;
use super::ALWAYS_TRUE_NAME;
use crate::StatefulPredicate;
use crate::predicates::macros::impl_predicate_common_methods;
use crate::predicates::macros::impl_predicate_debug_display;

/// A Box-based stateful predicate with single ownership.
///
/// This type stores a `Box<dyn FnMut(&T) -> bool>`, so each call may update
/// the predicate's internal state. Composition methods consume `self`,
/// matching the single-ownership model.
///
/// # Type Parameters
///
/// * `T` - The type of the value borrowed by the callback.
///
/// # Examples
///
/// ```
/// use qubit_function::BoxStatefulPredicate;
/// use qubit_function::StatefulPredicate;
///
/// let mut predicate = BoxStatefulPredicate::new(|value: &i32| *value > 0);
/// assert!(predicate.test(&5));
/// assert!(!predicate.test(&-3));
/// ```
#[must_use = "callback wrappers do nothing unless stored or invoked"]
pub struct BoxStatefulPredicate<T> {
    /// The wrapped callback implementation.
    pub(super) function: Box<dyn FnMut(&T) -> bool>,
    /// Diagnostic metadata associated with this callback.
    pub(super) metadata: crate::internal::CallbackMetadata,
}

impl<T> BoxStatefulPredicate<T> {
    // Generates: new(), new_with_name(), name(), set_name(), always_true(),
    // always_false()
    impl_predicate_common_methods!(BoxStatefulPredicate<T>, (FnMut(&T) -> bool + 'static), |f| Box::new(f));

    /// Returns a predicate representing logical AND with another predicate.
    ///
    /// This method consumes `self` and evaluates `other` only when this
    /// predicate returns `true`.
    ///
    /// # Parameters
    ///
    /// * `other` - The other predicate to combine with.
    ///
    /// # Returns
    ///
    /// A new `BoxStatefulPredicate` representing logical AND.
    #[inline]
    pub fn and<P>(mut self, mut other: P) -> BoxStatefulPredicate<T>
    where
        P: StatefulPredicate<T> + 'static,
        T: 'static,
    {
        BoxStatefulPredicate::new(move |value: &T| self.test(value) && other.test(value))
    }

    /// Returns a predicate representing logical OR with another predicate.
    ///
    /// This method consumes `self` and evaluates `other` only when this
    /// predicate returns `false`.
    ///
    /// # Parameters
    ///
    /// * `other` - The other predicate to combine with.
    ///
    /// # Returns
    ///
    /// A new `BoxStatefulPredicate` representing logical OR.
    #[inline]
    pub fn or<P>(mut self, mut other: P) -> BoxStatefulPredicate<T>
    where
        P: StatefulPredicate<T> + 'static,
        T: 'static,
    {
        BoxStatefulPredicate::new(move |value: &T| self.test(value) || other.test(value))
    }

    /// Returns a predicate representing logical NAND with another predicate.
    ///
    /// NAND returns `true` unless both predicates return `true`.
    ///
    /// # Parameters
    ///
    /// * `other` - The other predicate to combine with.
    ///
    /// # Returns
    ///
    /// A new `BoxStatefulPredicate` representing logical NAND.
    #[inline]
    pub fn nand<P>(mut self, mut other: P) -> BoxStatefulPredicate<T>
    where
        P: StatefulPredicate<T> + 'static,
        T: 'static,
    {
        BoxStatefulPredicate::new(move |value: &T| !(self.test(value) && other.test(value)))
    }

    /// Returns a predicate representing logical XOR with another predicate.
    ///
    /// XOR evaluates both predicates and returns `true` when exactly one
    /// predicate returns `true`.
    ///
    /// # Parameters
    ///
    /// * `other` - The other predicate to combine with.
    ///
    /// # Returns
    ///
    /// A new `BoxStatefulPredicate` representing logical XOR.
    #[inline]
    pub fn xor<P>(mut self, mut other: P) -> BoxStatefulPredicate<T>
    where
        P: StatefulPredicate<T> + 'static,
        T: 'static,
    {
        BoxStatefulPredicate::new(move |value: &T| self.test(value) ^ other.test(value))
    }

    /// Returns a predicate representing logical NOR with another predicate.
    ///
    /// NOR returns `true` only when both predicates return `false`.
    ///
    /// # Parameters
    ///
    /// * `other` - The other predicate to combine with.
    ///
    /// # Returns
    ///
    /// A new `BoxStatefulPredicate` representing logical NOR.
    #[inline]
    pub fn nor<P>(mut self, mut other: P) -> BoxStatefulPredicate<T>
    where
        P: StatefulPredicate<T> + 'static,
        T: 'static,
    {
        BoxStatefulPredicate::new(move |value: &T| !(self.test(value) || other.test(value)))
    }
}

impl<T> Not for BoxStatefulPredicate<T>
where
    T: 'static,
{
    type Output = BoxStatefulPredicate<T>;

    fn not(self) -> Self::Output {
        let metadata = self.metadata;
        let mut function = self.function;
        BoxStatefulPredicate::new_with_metadata(move |value: &T| !function(value), metadata)
    }
}

// Generates: impl Debug for BoxStatefulPredicate<T> and impl Display for
// BoxStatefulPredicate<T>
impl_predicate_debug_display!(BoxStatefulPredicate<T>);

// Implements StatefulPredicate trait for BoxStatefulPredicate<T>
impl<T> StatefulPredicate<T> for BoxStatefulPredicate<T> {
    #[inline(always)]
    fn test(&mut self, value: &T) -> bool {
        (self.function)(value)
    }
}