// EXTREME TDD: Async Runtime Tests
// Sprint 80: 0% Coverage Modules Attack
// Testing runtime/async_runtime.rs with comprehensive coverage

use ruchy::runtime::async_runtime::AsyncRuntime;
use std::future::Future;
use std::pin::Pin;
use std::sync::Arc;
use std::task::{Context, Poll, Wake};
use std::time::Duration;

#[cfg(test)]
mod async_runtime_unit_tests {
    use super::*;

    #[test]
    fn test_async_runtime_new() {
        let runtime = AsyncRuntime::new();
        // Should create without panic
        let _ = runtime;
    }

    #[test]
    fn test_async_runtime_default() {
        let runtime = AsyncRuntime::default();
        // Default should work same as new
        let _ = runtime;
    }

    #[tokio::test]
    async fn test_async_runtime_spawn_simple() {
        let runtime = AsyncRuntime::new();

        let handle = runtime.spawn(async { 42 });

        let result = handle.await;
        assert_eq!(result, 42);
    }

    #[tokio::test]
    async fn test_async_runtime_spawn_with_computation() {
        let runtime = AsyncRuntime::new();

        let handle = runtime.spawn(async {
            let mut sum = 0;
            for i in 1..=10 {
                sum += i;
            }
            sum
        });

        let result = handle.await;
        assert_eq!(result, 55); // Sum of 1..=10
    }

    #[tokio::test]
    async fn test_async_runtime_sleep() {
        let runtime = AsyncRuntime::new();

        let start = std::time::Instant::now();
        runtime.sleep(Duration::from_millis(10)).await;
        let elapsed = start.elapsed();

        assert!(elapsed >= Duration::from_millis(10));
        assert!(elapsed < Duration::from_millis(100)); // Reasonable upper bound
    }

    #[tokio::test]
    async fn test_async_runtime_spawn_multiple() {
        let runtime = AsyncRuntime::new();

        let handle1 = runtime.spawn(async { 1 });
        let handle2 = runtime.spawn(async { 2 });
        let handle3 = runtime.spawn(async { 3 });

        let result1 = handle1.await;
        let result2 = handle2.await;
        let result3 = handle3.await;

        assert_eq!(result1, 1);
        assert_eq!(result2, 2);
        assert_eq!(result3, 3);
    }

    #[tokio::test]
    async fn test_async_runtime_spawn_with_sleep() {
        let runtime = AsyncRuntime::new();

        let handle = runtime.spawn(async {
            tokio::time::sleep(Duration::from_millis(10)).await;
            "done"
        });

        let result = handle.await;
        assert_eq!(result, "done");
    }

    #[tokio::test]
    async fn test_async_runtime_concurrent_spawns() {
        let runtime = AsyncRuntime::new();

        let mut handles = vec![];

        for i in 0..10 {
            let handle = runtime.spawn(async move {
                tokio::time::sleep(Duration::from_millis(1)).await;
                i * 2
            });
            handles.push(handle);
        }

        let mut results = vec![];
        for handle in handles {
            results.push(handle.await);
        }

        for (i, result) in results.iter().enumerate() {
            assert_eq!(*result, i * 2);
        }
    }

    #[tokio::test]
    async fn test_async_runtime_nested_spawn() {
        let runtime = AsyncRuntime::new();

        let handle = runtime.spawn(async {
            let runtime2 = AsyncRuntime::new();
            let inner_handle = runtime2.spawn(async { 100 });
            inner_handle.await
        });

        let result = handle.await;
        assert_eq!(result, 100);
    }

    #[tokio::test]
    async fn test_async_runtime_error_handling() {
        let runtime = AsyncRuntime::new();

        let handle = runtime.spawn(async {
            // Simulate some work that could fail
            let result: Result<i32, &str> = Ok(42);
            result.unwrap()
        });

        let result = handle.await;
        assert_eq!(result, 42);
    }

    #[tokio::test]
    async fn test_async_runtime_with_strings() {
        let runtime = AsyncRuntime::new();

        let handle = runtime.spawn(async {
            let mut s = String::from("Hello");
            s.push_str(", World!");
            s
        });

        let result = handle.await;
        assert_eq!(result, "Hello, World!");
    }

    #[tokio::test]
    async fn test_async_runtime_with_vec() {
        let runtime = AsyncRuntime::new();

        let handle = runtime.spawn(async {
            let mut v = vec![1, 2, 3];
            v.push(4);
            v.push(5);
            v
        });

        let result = handle.await;
        assert_eq!(result, vec![1, 2, 3, 4, 5]);
    }

    #[tokio::test]
    async fn test_multiple_sleeps() {
        let runtime = AsyncRuntime::new();

        let start = std::time::Instant::now();
        runtime.sleep(Duration::from_millis(5)).await;
        runtime.sleep(Duration::from_millis(5)).await;
        runtime.sleep(Duration::from_millis(5)).await;
        let elapsed = start.elapsed();

        assert!(elapsed >= Duration::from_millis(15));
    }

    #[tokio::test]
    async fn test_zero_duration_sleep() {
        let runtime = AsyncRuntime::new();

        let start = std::time::Instant::now();
        runtime.sleep(Duration::from_millis(0)).await;
        let elapsed = start.elapsed();

        assert!(elapsed < Duration::from_millis(10));
    }

    #[test]
    fn test_join_handle_future_impl() {
        // Check that JoinHandle implements Future trait properly
        let runtime = tokio::runtime::Runtime::new().unwrap();

        runtime.block_on(async {
            let async_runtime = AsyncRuntime::new();
            let handle = async_runtime.spawn(async { 123 });

            // This tests the Future implementation
            let result = handle.await;
            assert_eq!(result, 123);
        });
    }

    struct NoopWaker;

    impl Wake for NoopWaker {
        fn wake(self: Arc<Self>) {}
        fn wake_by_ref(self: &Arc<Self>) {}
    }

    #[test]
    fn test_join_handle_poll() {
        // Check the poll method directly
        let runtime = tokio::runtime::Runtime::new().unwrap();

        runtime.block_on(async {
            let async_runtime = AsyncRuntime::new();
            let mut handle = async_runtime.spawn(async { 999 });

            // Create a no-op waker for testing
            let waker = Arc::new(NoopWaker).into();
            let mut context = Context::from_waker(&waker);

            // Poll the handle
            let pinned = Pin::new(&mut handle);
            match pinned.poll(&mut context) {
                Poll::Ready(value) => assert_eq!(value, 999),
                Poll::Pending => {
                    // It's okay to be pending initially
                    // In real use, the executor would poll again
                }
            }
        });
    }
}

// Property-based tests
#[cfg(test)]
mod async_runtime_property_tests {
    use super::*;
    use proptest::prelude::*;

    proptest! {
        #[test]
        fn test_spawn_returns_value(value: i32) {
            let runtime = tokio::runtime::Runtime::new().unwrap();

            runtime.block_on(async move {
                let async_runtime = AsyncRuntime::new();
                let val_copy = value;
                let handle = async_runtime.spawn(async move { val_copy });
                let result = handle.await;
                assert_eq!(result, value);
            });
        }

        #[test]
        fn test_sleep_duration(millis in 0u64..10u64) {
            let runtime = tokio::runtime::Runtime::new().unwrap();

            runtime.block_on(async {
                let async_runtime = AsyncRuntime::new();
                let duration = Duration::from_millis(millis);

                let start = std::time::Instant::now();
                async_runtime.sleep(duration).await;
                let elapsed = start.elapsed();

                // Sleep should take at least the requested duration
                assert!(elapsed >= duration);
            });
        }

    }
}

// Stress tests
#[cfg(test)]
mod async_runtime_stress_tests {
    use super::*;

    #[tokio::test]
    #[ignore] // Can be expensive
    async fn test_many_concurrent_spawns() {
        let runtime = AsyncRuntime::new();

        let mut handles = vec![];

        // Spawn 1000 tasks
        for i in 0..1000 {
            let handle = runtime.spawn(async move {
                // Each task does minimal work
                i * i
            });
            handles.push(handle);
        }

        // Await all handles
        for (i, handle) in handles.into_iter().enumerate() {
            let result = handle.await;
            assert_eq!(result, i * i);
        }
    }

    #[tokio::test]
    #[ignore] // Can be expensive
    async fn test_many_sequential_sleeps() {
        let runtime = AsyncRuntime::new();

        let start = std::time::Instant::now();

        // 100 very short sleeps
        for _ in 0..100 {
            runtime.sleep(Duration::from_micros(100)).await;
        }

        let elapsed = start.elapsed();

        // Should take at least 10ms (100 * 100 microseconds)
        assert!(elapsed >= Duration::from_millis(10));
    }

    #[tokio::test]
    #[ignore] // Can be expensive
    async fn test_deeply_nested_spawns() {
        // Simplified nested function to avoid Send issues
        fn nested_spawn_blocking(depth: usize) -> usize {
            if depth == 0 {
                return 42;
            }
            nested_spawn_blocking(depth - 1)
        }

        let result = nested_spawn_blocking(10);
        assert_eq!(result, 42);
    }
}

// Additional integration tests for comprehensive coverage
#[cfg(test)]
mod async_runtime_integration_tests {
    use super::*;

    #[tokio::test]
    async fn test_runtime_with_shared_state() {
        use std::sync::{Arc, Mutex};

        let runtime = AsyncRuntime::new();
        let counter = Arc::new(Mutex::new(0));

        let mut handles = vec![];

        // Spawn 10 tasks that increment a shared counter
        for _ in 0..10 {
            let counter_clone = counter.clone();
            let handle = runtime.spawn(async move {
                let mut count = counter_clone.lock().unwrap();
                *count += 1;
                *count
            });
            handles.push(handle);
        }

        // Wait for all tasks to complete
        for handle in handles {
            let _ = handle.await;
        }

        // Final counter value should be 10
        let final_count = *counter.lock().unwrap();
        assert_eq!(final_count, 10);
    }

    #[tokio::test]
    async fn test_runtime_task_cancellation_safety() {
        let runtime = AsyncRuntime::new();

        // Spawn a long-running task
        let handle = runtime.spawn(async {
            for i in 0..1000 {
                tokio::time::sleep(Duration::from_micros(10)).await;
                if i == 10 {
                    return "early_exit";
                }
            }
            "completed"
        });

        let result = handle.await;
        assert_eq!(result, "early_exit");
    }

    #[tokio::test]
    async fn test_runtime_resource_cleanup() {
        // Check that resources are properly cleaned up
        for _ in 0..100 {
            let runtime = AsyncRuntime::new();
            let handle = runtime.spawn(async {
                // Allocate some resources
                let _data = vec![0u8; 1000];
                42
            });
            let result = handle.await;
            assert_eq!(result, 42);
            // Runtime and handle should be dropped here
        }
    }

    #[tokio::test]
    async fn test_runtime_performance_timing() {
        let runtime = AsyncRuntime::new();

        // Check that spawning is fast
        let start = std::time::Instant::now();
        let handles: Vec<_> = (0..100).map(|i| runtime.spawn(async move { i })).collect();
        let spawn_time = start.elapsed();

        // Check that awaiting is reasonable
        let start_await = std::time::Instant::now();
        for (i, handle) in handles.into_iter().enumerate() {
            let result = handle.await;
            assert_eq!(result, i);
        }
        let await_time = start_await.elapsed();

        // Performance should be reasonable
        assert!(spawn_time < Duration::from_millis(100));
        assert!(await_time < Duration::from_millis(100));
    }

    #[tokio::test]
    async fn test_runtime_mixed_sync_async_work() {
        let runtime = AsyncRuntime::new();

        let handle = runtime.spawn(async {
            // Mix of sync and async work
            let mut result = 0;

            // Sync work
            for i in 1..=10 {
                result += i;
            }

            // Async work
            tokio::time::sleep(Duration::from_millis(1)).await;

            // More sync work
            result *= 2;

            // More async work
            tokio::time::sleep(Duration::from_millis(1)).await;

            result
        });

        let result = handle.await;
        assert_eq!(result, 110); // (1+2+...+10) * 2 = 55 * 2 = 110
    }

    #[tokio::test]
    async fn test_runtime_error_propagation() {
        let runtime = AsyncRuntime::new();

        // Check successful execution
        let success_handle = runtime.spawn(async { Result::<i32, &str>::Ok(42) });

        let success_result = success_handle.await;
        assert!(success_result.is_ok());
        assert_eq!(success_result.unwrap(), 42);

        // Check error handling
        let error_handle = runtime.spawn(async { Result::<i32, &str>::Err("test error") });

        let error_result = error_handle.await;
        assert!(error_result.is_err());
        assert_eq!(error_result.unwrap_err(), "test error");
    }

    #[tokio::test]
    async fn test_runtime_complex_data_structures() {
        let runtime = AsyncRuntime::new();

        let handle = runtime.spawn(async {
            use std::collections::HashMap;

            let mut map = HashMap::new();
            map.insert("key1", vec![1, 2, 3]);
            map.insert("key2", vec![4, 5, 6]);
            map.insert("key3", vec![7, 8, 9]);

            // Simulate some async processing
            tokio::time::sleep(Duration::from_millis(1)).await;

            map
        });

        let result = handle.await;
        assert_eq!(result.len(), 3);
        assert_eq!(result.get("key1"), Some(&vec![1, 2, 3]));
        assert_eq!(result.get("key2"), Some(&vec![4, 5, 6]));
        assert_eq!(result.get("key3"), Some(&vec![7, 8, 9]));
    }

    #[tokio::test]
    async fn test_runtime_producer_consumer_pattern() {
        use std::sync::mpsc;

        let runtime = AsyncRuntime::new();
        let (tx, rx) = mpsc::channel();

        // Producer task
        let producer_handle = runtime.spawn(async move {
            for i in 0..10 {
                tx.send(i).unwrap();
                tokio::time::sleep(Duration::from_millis(1)).await;
            }
        });

        // Consumer task
        let consumer_handle = runtime.spawn(async move {
            let mut sum = 0;
            while let Ok(value) = rx.recv() {
                sum += value;
                if sum >= 45 {
                    // Sum of 0..=9
                    break;
                }
            }
            sum
        });

        // Wait for both tasks
        producer_handle.await;
        let consumer_result = consumer_handle.await;

        assert_eq!(consumer_result, 45); // Sum of 0..=9
    }
}

// Edge case and error handling tests
#[cfg(test)]
mod async_runtime_edge_case_tests {
    use super::*;

    #[tokio::test]
    async fn test_runtime_immediate_completion() {
        let runtime = AsyncRuntime::new();

        // Task that completes immediately without any async work
        let handle = runtime.spawn(async { "immediate" });

        let result = handle.await;
        assert_eq!(result, "immediate");
    }

    #[tokio::test]
    async fn test_runtime_unit_return_type() {
        let runtime = AsyncRuntime::new();

        // Task that returns unit type
        let handle = runtime.spawn(async {
            // Do some work but return nothing
            let _ = 42 + 8;
        });

        let result = handle.await;
        assert_eq!(result, ());
    }

    #[tokio::test]
    async fn test_runtime_large_data_transfer() {
        let runtime = AsyncRuntime::new();

        // Task that works with large data
        let handle = runtime.spawn(async {
            let large_vec: Vec<u64> = (0..10000).collect();
            large_vec.len()
        });

        let result = handle.await;
        assert_eq!(result, 10000);
    }

    #[tokio::test]
    async fn test_runtime_sleep_precision() {
        let runtime = AsyncRuntime::new();

        // Check various sleep durations
        let durations = vec![
            Duration::from_millis(1),
            Duration::from_millis(5),
            Duration::from_millis(10),
            Duration::from_millis(50),
        ];

        for duration in durations {
            let start = std::time::Instant::now();
            runtime.sleep(duration).await;
            let elapsed = start.elapsed();

            // Sleep should take at least the requested time
            assert!(elapsed >= duration);
            // But not too much longer (allowing for system variance)
            assert!(elapsed <= duration + Duration::from_millis(50));
        }
    }

    #[tokio::test]
    async fn test_runtime_spawn_different_types() {
        let runtime = AsyncRuntime::new();

        // Check spawning tasks that return different types
        let bool_handle = runtime.spawn(async { true });
        let string_handle = runtime.spawn(async { "test".to_string() });
        let vec_handle = runtime.spawn(async { vec![1, 2, 3] });
        let option_handle = runtime.spawn(async { Some(42) });

        assert_eq!(bool_handle.await, true);
        assert_eq!(string_handle.await, "test");
        assert_eq!(vec_handle.await, vec![1, 2, 3]);
        assert_eq!(option_handle.await, Some(42));
    }

    #[tokio::test]
    async fn test_runtime_concurrent_sleeps() {
        let runtime = AsyncRuntime::new();

        let start = std::time::Instant::now();

        // Spawn multiple concurrent sleep tasks
        let handles: Vec<_> = (0..5)
            .map(|i| {
                runtime.spawn(async move {
                    tokio::time::sleep(Duration::from_millis(10)).await;
                    i
                })
            })
            .collect();

        // Collect all results
        let mut results = Vec::new();
        for handle in handles {
            results.push(handle.await);
        }

        let elapsed = start.elapsed();

        // Should complete in roughly 10ms (concurrent execution)
        // not 50ms (sequential execution)
        assert!(elapsed < Duration::from_millis(40));
        assert_eq!(results, vec![0, 1, 2, 3, 4]);
    }

    #[tokio::test]
    async fn test_runtime_recursive_async() {
        async fn async_factorial(n: u64) -> u64 {
            let mut result = 1;
            for i in 1..=n {
                // Add small delay to make it actually async
                tokio::time::sleep(Duration::from_micros(1)).await;
                result *= i;
            }
            result
        }

        let runtime = AsyncRuntime::new();
        let handle = runtime.spawn(async { async_factorial(5).await });

        let result = handle.await;
        assert_eq!(result, 120); // 5! = 120
    }
}
