qubit_function/tester/

arc_tester.rs

/*******************************************************************************
 *
 *    Copyright (c) 2025 - 2026 Haixing Hu.
 *
 *    SPDX-License-Identifier: Apache-2.0
 *
 *    Licensed under the Apache License, Version 2.0.
 *
 ******************************************************************************/
// qubit-style: allow explicit-imports
//! Defines the `ArcTester` public type.

use std::ops::Not;

use super::{
    Arc,
    BoxTester,
    Rc,
    RcTester,
    Tester,
};

// ============================================================================
// ArcTester: Thread-Safe Shared Ownership Implementation
// ============================================================================

/// Thread-safe shared ownership Tester implemented using `Arc`
///
/// `ArcTester` wraps a closure in `Arc<dyn Fn() -> bool + Send + Sync>`,
/// allowing the tester to be cloned and safely shared across threads.
///
/// # Characteristics
///
/// - **Shared ownership**: Can be cloned
/// - **Thread-safe**: Can be sent across threads
/// - **Lock-free overhead**: Uses `Fn` without needing `Mutex`
/// - **Borrowing combination**: `and()`/`or()` borrow `&self`
///
/// # Use Cases
///
/// - Multi-threaded testing scenarios
/// - Health checks shared across threads
/// - Test states requiring concurrent access
/// - Background monitoring tasks
///
/// # Examples
///
/// ```rust
/// use qubit_function::{ArcTester, Tester};
/// use std::sync::{Arc, atomic::{AtomicUsize, Ordering}};
/// use std::thread;
///
/// // Shared atomic counter
/// let counter = Arc::new(AtomicUsize::new(0));
/// let counter_clone = Arc::clone(&counter);
///
/// let shared = ArcTester::new(move || {
///     counter_clone.load(Ordering::Relaxed) <= 5
/// });
///
/// let clone = shared.clone();
/// let handle = thread::spawn(move || {
///     clone.test()
/// });
///
/// assert!(handle.join().expect("thread should not panic"));
/// counter.fetch_add(1, Ordering::Relaxed);
/// assert!(shared.test());
/// ```
///
pub struct ArcTester {
    pub(super) function: Arc<dyn Fn() -> bool + Send + Sync>,
}

impl ArcTester {
    /// Creates a new `ArcTester` from a closure
    ///
    /// # Type Parameters
    ///
    /// * `F` - Closure type implementing `Fn() -> bool + Send + Sync`
    ///
    /// # Parameters
    ///
    /// * `f` - The closure to wrap
    ///
    /// # Return Value
    ///
    /// A new `ArcTester` instance
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::ArcTester;
    ///
    /// let tester = ArcTester::new(|| true);
    /// ```
    #[inline]
    pub fn new<F>(f: F) -> Self
    where
        F: Fn() -> bool + Send + Sync + 'static,
    {
        ArcTester {
            function: Arc::new(f),
        }
    }

    /// Combines this tester with another tester using logical AND
    ///
    /// Returns a new `ArcTester` that returns `true` only when both tests
    /// pass. Borrows `&self`, so the original tester remains available.
    ///
    /// # Parameters
    ///
    /// * `next` - The tester to combine with
    ///
    /// # Return Value
    ///
    /// A new `ArcTester` representing logical AND
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{ArcTester, Tester};
    /// use std::sync::{Arc, atomic::{AtomicUsize, AtomicBool, Ordering}};
    /// use std::thread;
    ///
    /// // Simulate database connection pool status
    /// let active_connections = Arc::new(AtomicUsize::new(0));
    /// let is_pool_healthy = Arc::new(AtomicBool::new(true));
    /// let max_connections = 50;
    ///
    /// let conn_clone = Arc::clone(&active_connections);
    /// let health_clone = Arc::clone(&is_pool_healthy);
    ///
    /// // Connection pool health check
    /// let pool_healthy = ArcTester::new(move || {
    ///     health_clone.load(Ordering::Relaxed)
    /// });
    ///
    /// // Connection count check
    /// let conn_ok = ArcTester::new(move || {
    ///     conn_clone.load(Ordering::Relaxed) < max_connections
    /// });
    ///
    /// // Combined check: pool healthy and connection count not exceeded
    /// let pool_ready = pool_healthy.and(&conn_ok);
    ///
    /// // Multi-threaded test
    /// let pool_ready_clone = pool_ready.clone();
    /// let handle = thread::spawn(move || {
    ///     pool_ready_clone.test()
    /// });
    ///
    /// // Initial state should pass
    /// assert!(handle.join().expect("thread should not panic"));
    /// assert!(pool_ready.test());
    ///
    /// // Connection count exceeded
    /// active_connections.store(60, Ordering::Relaxed);
    /// assert!(!pool_ready.test());
    ///
    /// // Connection pool unhealthy
    /// is_pool_healthy.store(false, Ordering::Relaxed);
    /// assert!(!pool_ready.test());
    /// ```
    #[inline]
    pub fn and(&self, next: &ArcTester) -> ArcTester {
        let self_fn = Arc::clone(&self.function);
        let next_fn = Arc::clone(&next.function);
        ArcTester {
            function: Arc::new(move || self_fn() && next_fn()),
        }
    }

    /// Combines this tester with another tester using logical OR
    ///
    /// Returns a new `ArcTester` that returns `true` if either test passes.
    /// Borrows `&self`, so the original tester remains available.
    ///
    /// # Parameters
    ///
    /// * `next` - The tester to combine with
    ///
    /// # Return Value
    ///
    /// A new `ArcTester` representing logical OR
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{ArcTester, Tester};
    /// use std::sync::{Arc, atomic::{AtomicUsize, AtomicBool, Ordering}};
    /// use std::thread;
    ///
    /// // Simulate load balancer status
    /// let server_load = Arc::new(AtomicUsize::new(0));
    /// let is_server_healthy = Arc::new(AtomicBool::new(true));
    /// let max_load = 80;
    /// let emergency_mode = Arc::new(AtomicBool::new(false));
    ///
    /// let load_clone = Arc::clone(&server_load);
    /// let health_clone = Arc::clone(&is_server_healthy);
    /// let emergency_clone = Arc::clone(&emergency_mode);
    ///
    /// // Server low load
    /// let low_load = ArcTester::new(move || {
    ///     load_clone.load(Ordering::Relaxed) < max_load
    /// });
    ///
    /// // Emergency mode check
    /// let emergency_check = ArcTester::new(move || {
    ///     emergency_clone.load(Ordering::Relaxed)
    /// });
    ///
    /// // Server health check
    /// let server_healthy = ArcTester::new(move || {
    ///     health_clone.load(Ordering::Relaxed)
    /// });
    ///
    /// // Emergency mode or server healthy
    /// let can_handle_requests = emergency_check.or(&server_healthy);
    ///
    /// // Combined condition: low load or can handle requests
    /// let should_route_here = low_load.or(&can_handle_requests);
    ///
    /// // Multi-threaded test
    /// let router_clone = should_route_here.clone();
    /// let handle = thread::spawn(move || {
    ///     router_clone.test()
    /// });
    ///
    /// // Initial state: low load and healthy
    /// assert!(handle.join().expect("thread should not panic"));
    /// assert!(should_route_here.test());
    ///
    /// // High load but server healthy
    /// server_load.store(90, Ordering::Relaxed);
    /// assert!(should_route_here.test()); // still healthy
    ///
    /// // Server unhealthy but emergency mode
    /// is_server_healthy.store(false, Ordering::Relaxed);
    /// emergency_mode.store(true, Ordering::Relaxed);
    /// assert!(should_route_here.test()); // emergency mode
    ///
    /// // Unhealthy and not emergency mode
    /// emergency_mode.store(false, Ordering::Relaxed);
    /// assert!(!should_route_here.test());
    /// ```
    #[inline]
    pub fn or(&self, next: &ArcTester) -> ArcTester {
        let self_fn = Arc::clone(&self.function);
        let next_fn = Arc::clone(&next.function);
        ArcTester {
            function: Arc::new(move || self_fn() || next_fn()),
        }
    }

    /// Combines this tester with another tester using logical NAND
    ///
    /// Returns a new `ArcTester` that returns `true` unless both tests pass.
    /// Borrows `&self`, so the original tester remains available.
    ///
    /// # Parameters
    ///
    /// * `next` - The tester to combine with
    ///
    /// # Return Value
    ///
    /// A new `ArcTester` representing logical NAND
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{ArcTester, Tester};
    /// use std::sync::{Arc, atomic::{AtomicBool, Ordering}};
    /// use std::thread;
    ///
    /// let flag1 = Arc::new(AtomicBool::new(true));
    /// let flag2 = Arc::new(AtomicBool::new(true));
    ///
    /// let flag1_clone = Arc::clone(&flag1);
    /// let flag2_clone = Arc::clone(&flag2);
    ///
    /// let tester1 = ArcTester::new(move || {
    ///     flag1_clone.load(Ordering::Relaxed)
    /// });
    ///
    /// let tester2 = ArcTester::new(move || {
    ///     flag2_clone.load(Ordering::Relaxed)
    /// });
    ///
    /// let nand = tester1.nand(&tester2);
    ///
    /// // Both true returns false
    /// assert!(!nand.test());
    ///
    /// // At least one false returns true
    /// flag1.store(false, Ordering::Relaxed);
    /// assert!(nand.test());
    ///
    /// // Original tester still available
    /// assert!(!tester1.test());
    /// assert!(tester2.test());
    /// ```
    #[inline]
    pub fn nand(&self, next: &ArcTester) -> ArcTester {
        let self_fn = Arc::clone(&self.function);
        let next_fn = Arc::clone(&next.function);
        ArcTester {
            function: Arc::new(move || !(self_fn() && next_fn())),
        }
    }

    /// Combines this tester with another tester using logical XOR
    ///
    /// Returns a new `ArcTester` that returns `true` if exactly one test
    /// passes. Borrows `&self`, so the original tester remains available.
    ///
    /// # Parameters
    ///
    /// * `next` - The tester to combine with
    ///
    /// # Return Value
    ///
    /// A new `ArcTester` representing logical XOR
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{ArcTester, Tester};
    /// use std::sync::{Arc, atomic::{AtomicBool, Ordering}};
    /// use std::thread;
    ///
    /// let flag1 = Arc::new(AtomicBool::new(true));
    /// let flag2 = Arc::new(AtomicBool::new(false));
    ///
    /// let flag1_clone = Arc::clone(&flag1);
    /// let flag2_clone = Arc::clone(&flag2);
    ///
    /// let tester1 = ArcTester::new(move || {
    ///     flag1_clone.load(Ordering::Relaxed)
    /// });
    ///
    /// let tester2 = ArcTester::new(move || {
    ///     flag2_clone.load(Ordering::Relaxed)
    /// });
    ///
    /// let xor = tester1.xor(&tester2);
    ///
    /// // One true one false returns true
    /// assert!(xor.test());
    ///
    /// // Both true returns false
    /// flag2.store(true, Ordering::Relaxed);
    /// assert!(!xor.test());
    ///
    /// // Both false returns false
    /// flag1.store(false, Ordering::Relaxed);
    /// flag2.store(false, Ordering::Relaxed);
    /// assert!(!xor.test());
    ///
    /// // Original tester still available
    /// assert!(!tester1.test());
    /// assert!(!tester2.test());
    /// ```
    #[inline]
    pub fn xor(&self, next: &ArcTester) -> ArcTester {
        let self_fn = Arc::clone(&self.function);
        let next_fn = Arc::clone(&next.function);
        ArcTester {
            function: Arc::new(move || self_fn() ^ next_fn()),
        }
    }

    /// Combines this tester with another tester using logical NOR
    ///
    /// Returns a new `ArcTester` that returns `true` only when both tests
    /// fail. Borrows `&self`, so the original tester remains available.
    ///
    /// # Parameters
    ///
    /// * `next` - The tester to combine with
    ///
    /// # Return Value
    ///
    /// A new `ArcTester` representing logical NOR
    ///
    /// # Examples
    ///
    /// ```rust
    /// use qubit_function::{ArcTester, Tester};
    /// use std::sync::{Arc, atomic::{AtomicBool, Ordering}};
    /// use std::thread;
    ///
    /// let flag1 = Arc::new(AtomicBool::new(false));
    /// let flag2 = Arc::new(AtomicBool::new(false));
    ///
    /// let flag1_clone = Arc::clone(&flag1);
    /// let flag2_clone = Arc::clone(&flag2);
    ///
    /// let tester1 = ArcTester::new(move || {
    ///     flag1_clone.load(Ordering::Relaxed)
    /// });
    ///
    /// let tester2 = ArcTester::new(move || {
    ///     flag2_clone.load(Ordering::Relaxed)
    /// });
    ///
    /// let nor = tester1.nor(&tester2);
    ///
    /// // Both false returns true
    /// assert!(nor.test());
    ///
    /// // At least one true returns false
    /// flag1.store(true, Ordering::Relaxed);
    /// assert!(!nor.test());
    ///
    /// // Original tester still available
    /// assert!(tester1.test());
    /// assert!(!tester2.test());
    /// ```
    #[inline]
    pub fn nor(&self, next: &ArcTester) -> ArcTester {
        let self_fn = Arc::clone(&self.function);
        let next_fn = Arc::clone(&next.function);
        ArcTester {
            function: Arc::new(move || !(self_fn() || next_fn())),
        }
    }
}

impl Not for ArcTester {
    type Output = ArcTester;

    #[inline]
    fn not(self) -> Self::Output {
        let func = self.function;
        ArcTester {
            function: Arc::new(move || !func()),
        }
    }
}

impl Not for &ArcTester {
    type Output = ArcTester;

    #[inline]
    fn not(self) -> Self::Output {
        let func = Arc::clone(&self.function);
        ArcTester {
            function: Arc::new(move || !func()),
        }
    }
}

impl Tester for ArcTester {
    #[inline]
    fn test(&self) -> bool {
        (self.function)()
    }

    #[inline]
    fn into_box(self) -> BoxTester {
        let func = self.function;
        BoxTester {
            function: Box::new(move || func()),
        }
    }

    #[inline]
    fn into_rc(self) -> RcTester {
        let func = self.function;
        RcTester {
            function: Rc::new(move || func()),
        }
    }

    #[inline]
    fn into_arc(self) -> ArcTester {
        self
    }

    #[inline]
    fn into_fn(self) -> impl Fn() -> bool {
        move || (self.function)()
    }

    #[inline]
    fn to_box(&self) -> BoxTester {
        let self_fn = self.function.clone();
        BoxTester {
            function: Box::new(move || self_fn()),
        }
    }

    #[inline]
    fn to_rc(&self) -> RcTester {
        let self_fn = self.function.clone();
        RcTester {
            function: Rc::new(move || self_fn()),
        }
    }

    #[inline]
    fn to_arc(&self) -> ArcTester {
        self.clone()
    }

    #[inline]
    fn to_fn(&self) -> impl Fn() -> bool {
        let self_fn = self.function.clone();
        move || self_fn()
    }
}

impl Clone for ArcTester {
    /// Creates a clone of this `ArcTester`.
    ///
    /// The cloned instance shares the same underlying function with
    /// the original, allowing multiple references to the same test
    /// logic.
    #[inline]
    fn clone(&self) -> Self {
        Self {
            function: Arc::clone(&self.function),
        }
    }
}