announcement/tests/no_receiver_tests.rs

//! Tests for announcing with no receivers - critical edge cases
//!
//! These tests verify that the announcement system handles gracefully:
//! - Announcing with 0 listeners
//! - Listeners created but dropped before announce
//! - Ensuring no memory leaks or panics

use announcement::Announcement;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Arc;
use std::thread;
use std::time::Instant;

/// Test: Announce with 0 listeners created at all
///
/// Verifies: Announce with 0 listeners created at all
/// Category: close
#[test]
fn test_announce_with_zero_listeners_created() {
    let (announcer, _announcement) = Announcement::<i32>::new();

    // No listeners created at all
    // Should succeed without panic
    announcer.announce(42).unwrap();
}

/// Test: Announce then drop announcement (no listeners exist)
///
/// Verifies: Announce then drop announcement (no listeners exist)
/// Category: close
#[test]
fn test_announce_then_drop_announcement_no_listeners() {
    let (announcer, announcement) = Announcement::<i32>::new();

    // Drop the announcement immediately
    drop(announcement);

    // Should still succeed
    announcer.announce(42).unwrap();
}

/// Test: Announce with listeners created but all dropped before announce
///
/// Verifies: Announce with listeners created but all dropped before announce
/// Category: close
#[test]
fn test_all_listeners_dropped_before_announce() {
    let (announcer, announcement) = Announcement::<String>::new();

    // Create listeners then immediately drop them
    {
        let _listener1 = announcement.listener();
        let _listener2 = announcement.listener();
        let _listener3 = announcement.listener();
        let _listener4 = announcement.listener();
        let _listener5 = announcement.listener();
        // All listeners dropped here
    }

    // Should still announce successfully
    announcer.announce("test".to_string()).unwrap();

    // Verify new listeners can still get the value
    let new_listener = announcement.listener();
    assert_eq!(new_listener.try_listen(), Some("test".to_string()));
}

/// Test: Announce with listeners created but all dropped after announce
///
/// Verifies: Announce with listeners created but all dropped after announce
/// Category: close
#[test]
fn test_all_listeners_dropped_after_announce() {
    let (announcer, announcement) = Announcement::<Vec<u8>>::new();

    let mut listeners = Vec::new();
    for _ in 0..10 {
        listeners.push(announcement.listener());
    }

    announcer.announce(vec![1, 2, 3]).unwrap();

    // Drop all listeners after announce
    drop(listeners);

    // New listener should still get the value
    let new_listener = announcement.listener();
    assert_eq!(new_listener.try_listen(), Some(vec![1, 2, 3]));
}

/// Test: Verify no memory leaks when value should be dropped
///
/// Verifies: no memory leaks when value should be dropped
/// Category: close
#[test]
fn test_no_memory_leak_value_dropped_with_last_reference() {
    static DROP_COUNT: AtomicUsize = AtomicUsize::new(0);

    #[derive(Clone, Debug)]
    struct DropTracker {
        _value: i32,
    }

    impl Drop for DropTracker {
        /// Test: No-receiver test: drop
        ///
        /// Verifies: Verifies drop
        /// Category: no-receiver
        fn drop(&mut self) {
            DROP_COUNT.fetch_add(1, Ordering::SeqCst);
        }
    }

    DROP_COUNT.store(0, Ordering::SeqCst);

    // Test 1: No listeners at all
    {
        let (announcer, announcement) = Announcement::new();
        let tracker = DropTracker { _value: 1 };
        announcer.announce(tracker).unwrap();
        drop(announcement);
    }

    let drops_after_no_listeners = DROP_COUNT.load(Ordering::SeqCst);
    assert!(
        drops_after_no_listeners >= 1,
        "DropTracker should be dropped when no references exist"
    );

    DROP_COUNT.store(0, Ordering::SeqCst);

    // Test 2: Listeners created and dropped
    {
        let (announcer, announcement) = Announcement::new();
        let tracker = DropTracker { _value: 2 };

        let listener1 = announcement.listener();
        let listener2 = announcement.listener();

        announcer.announce(tracker).unwrap();

        // Get values to ensure clones are made
        let _val1 = listener1.try_listen();
        let _val2 = listener2.try_listen();

        // Drop everything
        drop(listener1);
        drop(listener2);
        drop(announcement);
        drop(_val1);
        drop(_val2);
    }

    let drops_after_listeners = DROP_COUNT.load(Ordering::SeqCst);
    assert!(
        drops_after_listeners >= 1,
        "All DropTracker instances should be dropped"
    );
}

/// Test: Multiple announcements to nobody in a loop (stress test)
///
/// Verifies: Multiple announcements to nobody in a loop (stress test)
/// Category: close
#[test]
fn test_multiple_announcements_to_nobody_stress() {
    for i in 0..1000 {
        let (announcer, _announcement) = Announcement::<i32>::new();
        announcer.announce(i).unwrap();
    }
}

/// Test: Large data announced with no listeners (memory stress)
///
/// Verifies: Large data announced with no listeners (memory stress)
/// Category: close
#[test]
fn test_announce_large_data_no_listeners() {
    let (announcer, _announcement) = Announcement::<Vec<u8>>::new();

    // Announce 10MB of data with no listeners
    let large_data = vec![0u8; 10 * 1024 * 1024];
    announcer.announce(large_data).unwrap();
}

/// Test: Arc-wrapped data with no listeners
///
/// Verifies: Arc-wrapped data with no listeners
/// Category: close
#[test]
fn test_announce_arc_data_no_listeners() {
    let (announcer, _announcement) = Announcement::<Arc<String>>::new();

    let data = Arc::new("shared data".to_string());
    let initial_count = Arc::strong_count(&data);

    announcer.announce(data.clone()).unwrap();

    // After announce with no listeners, Arc count should only increase by 1 (stored in OnceLock)
    assert_eq!(Arc::strong_count(&data), initial_count + 1);
}

/// Test: Announcement dropped before announcer with no listeners
///
/// Verifies: Announcement dropped before announcer with no listeners
/// Category: close
#[test]
fn test_announcement_dropped_before_announcer_no_listeners() {
    let (announcer, announcement) = Announcement::<i32>::new();

    // Drop announcement first
    drop(announcement);

    // Announce should still succeed
    announcer.announce(42).unwrap();
}

/// Test: Rapid creation and dropping of empty announcements
///
/// Verifies: Rapid creation and dropping of empty announcements
/// Category: close
#[test]
fn test_rapid_empty_announcement_creation() {
    for _ in 0..10000 {
        let (_announcer, announcement) = Announcement::<()>::new();
        drop(announcement);
    }
}

/// Test: Threaded announce with no listeners
///
/// Verifies: Threaded announce with no listeners
/// Category: close
#[test]
fn test_threaded_announce_no_listeners() {
    let (announcer, announcement) = Announcement::<i32>::new();

    let handle = thread::spawn(move || {
        announcer.announce(42).unwrap();
    });

    // No listeners created
    handle.join().unwrap();

    // New listener after announce in different thread
    let listener = announcement.listener();
    assert_eq!(listener.try_listen(), Some(42));
}

/// Test: Many announcements with no listeners in parallel
///
/// Verifies: Many announcements with no listeners in parallel
/// Category: close
#[test]
fn test_parallel_announcements_no_listeners() {
    let mut handles = vec![];

    for i in 0..100 {
        handles.push(thread::spawn(move || {
            let (announcer, _announcement) = Announcement::<i32>::new();
            announcer.announce(i).unwrap();
        }));
    }

    for handle in handles {
        handle.join().unwrap();
    }
}

/// Test: Create and drop listeners in a tight loop, then announce
///
/// Verifies: Create and drop listeners in a tight loop, then announce
/// Category: close
#[test]
fn test_listener_churn_before_announce() {
    let (announcer, announcement) = Announcement::<i32>::new();

    // Create and immediately drop 100,000 listeners
    for _ in 0..100_000 {
        drop(announcement.listener());
    }

    // Should still work fine
    announcer.announce(42).unwrap();

    // New listener should get value
    let listener = announcement.listener();
    assert_eq!(listener.try_listen(), Some(42));
}

/// Test: Listeners created in threads, all dropped before announce
///
/// Verifies: Listeners created in threads, all dropped before announce
/// Category: close
#[test]
fn test_threaded_listeners_all_dropped() {
    let (announcer, announcement) = Announcement::<String>::new();

    let mut handles = vec![];

    // Create listeners in 10 threads
    for _ in 0..10 {
        let ann = announcement.clone();
        handles.push(thread::spawn(move || {
            // Create 100 listeners and immediately drop them
            for _ in 0..100 {
                drop(ann.listener());
            }
        }));
    }

    // Wait for all threads to finish
    for handle in handles {
        handle.join().unwrap();
    }

    // Announce after all listeners are gone
    announcer.announce("all dropped".to_string()).unwrap();

    // New listener should work
    let listener = announcement.listener();
    assert_eq!(listener.try_listen(), Some("all dropped".to_string()));
}

/// Test: Close test: zero overhead no listeners
///
/// Verifies: zero overhead no listeners
/// Category: close
#[test]
fn test_zero_overhead_no_listeners() {
    // Warm up
    for _ in 0..10 {
        let (announcer, _) = Announcement::<i32>::new();
        announcer.announce(42).unwrap();
    }

    // Measure time for 1000 announcements with no listeners
    let start = Instant::now();
    for i in 0..1000 {
        let (announcer, _) = Announcement::<i32>::new();
        announcer.announce(i).unwrap();
    }
    let duration = start.elapsed();

    // Should be very fast (sub-millisecond for 1000 announcements)
    assert!(
        duration.as_millis() < 10,
        "Announcing to no listeners should be nearly zero overhead"
    );
}

/// Test: Create 1M listeners, drop them all, then announce
///
/// Verifies: Create 1M listeners, drop them all, then announce
/// Category: close
#[test]
fn test_value_dropped_when_announcement_dropped() {
    static DROP_COUNT: AtomicUsize = AtomicUsize::new(0);

    #[derive(Clone, Debug)]
    struct ValueDropTracker {
        _data: Vec<u8>,
    }

    impl Drop for ValueDropTracker {
        /// Test: No-receiver test: drop
        ///
        /// Verifies: Verifies drop
        /// Category: no-receiver
        fn drop(&mut self) {
            DROP_COUNT.fetch_add(1, Ordering::SeqCst);
        }
    }

    DROP_COUNT.store(0, Ordering::SeqCst);

    {
        let (announcer, announcement) = Announcement::new();
        let tracker = ValueDropTracker {
            _data: vec![1, 2, 3],
        };

        announcer.announce(tracker).unwrap();

        // No listeners, drop announcement
        drop(announcement);
    }

    // Value should be dropped
    let drops = DROP_COUNT.load(Ordering::SeqCst);
    assert!(
        drops >= 1,
        "Value should be dropped when announcement is dropped with no references"
    );
}

/// Test: Complex scenario - mixed listener lifecycle with no final listeners
///
/// Verifies: Complex scenario - mixed listener lifecycle with no final listeners
/// Category: close
#[test]
fn test_complex_no_listener_scenario() {
    use std::collections::HashMap;

    let (announcer, announcement) = Announcement::<HashMap<String, Vec<i32>>>::new();

    // Phase 1: Create some listeners
    let listeners: Vec<_> = (0..5).map(|_| announcement.listener()).collect();

    // Phase 2: Drop half of them
    drop(listeners);

    // Phase 3: Create more and drop immediately
    for _ in 0..10 {
        drop(announcement.listener());
    }

    // Phase 4: Create listeners in a thread that exits immediately
    let ann = announcement.clone();
    thread::spawn(move || {
        let _l1 = ann.listener();
        let _l2 = ann.listener();
        // Thread exits, dropping listeners
    })
    .join()
    .unwrap();

    // Phase 5: Announce with no active listeners
    let mut data = HashMap::new();
    data.insert("key".to_string(), vec![1, 2, 3]);
    announcer.announce(data.clone()).unwrap();

    // Phase 6: Verify new listener still works
    let final_listener = announcement.listener();
    assert_eq!(final_listener.try_listen(), Some(data));
}

/// Test: Announcer with custom Drop impl and no listeners
///
/// Verifies: Announcer with custom Drop impl and no listeners
/// Category: close
#[test]
fn test_custom_drop_type_no_listeners() {
    static CUSTOM_DROP: AtomicUsize = AtomicUsize::new(0);

    #[derive(Clone, Debug)]
    struct CustomDrop {
        id: usize,
    }

    impl Drop for CustomDrop {
        /// Test: No-receiver test: drop
        ///
        /// Verifies: Verifies drop
        /// Category: no-receiver
        fn drop(&mut self) {
            CUSTOM_DROP.fetch_add(self.id, Ordering::SeqCst);
        }
    }

    CUSTOM_DROP.store(0, Ordering::SeqCst);

    {
        let (announcer, announcement) = Announcement::new();
        let custom = CustomDrop { id: 100 };

        announcer.announce(custom).unwrap();
        drop(announcement);
    }

    // Should have been dropped (at least the original + the clone in OnceLock)
    assert!(
        CUSTOM_DROP.load(Ordering::SeqCst) >= 100,
        "CustomDrop should be dropped at least once"
    );
}

/// Test: Close test: announce no listeners no blocking
///
/// Verifies: announce no listeners no blocking
/// Category: close
#[test]
fn test_announce_no_listeners_no_blocking() {
    let (announcer, _announcement) = Announcement::<String>::new();

    let start = Instant::now();
    announcer.announce("immediate".to_string()).unwrap();
    let elapsed = start.elapsed();

    // Should complete in microseconds
    assert!(
        elapsed.as_micros() < 1000,
        "Announce should not block when there are no listeners"
    );
}

/// Test: Close test: async no listeners
///
/// Verifies: async no listeners
/// Category: close

#[tokio::test]
async fn test_async_no_listeners() {
    let (announcer, _announcement) = Announcement::<i32>::new();

    // Announce with no async listeners
    announcer.announce(42).unwrap();
}

/// Test: Memory safety with no listeners and large recursive structure
///
/// Verifies: Memory safety with no listeners and large recursive structure
/// Category: close
#[test]
fn test_recursive_structure_no_listeners() {
    #[derive(Clone, Debug)]
    #[allow(dead_code)]
    enum Tree {
        Leaf(i32),
        Node(Box<Tree>, Box<Tree>),
    }

    fn create_deep_tree(depth: usize) -> Tree {
        if depth == 0 {
            Tree::Leaf(42)
        } else {
            Tree::Node(
                Box::new(create_deep_tree(depth - 1)),
                Box::new(create_deep_tree(depth - 1)),
            )
        }
    }

    let (announcer, _announcement) = Announcement::new();

    // Create a tree with depth 10 (1024 leaf nodes)
    let tree = create_deep_tree(10);

    // Announce with no listeners - should handle the recursive structure properly
    announcer.announce(tree).unwrap();
}