//! Comprehensive connection pool edge case tests
//!
//! These tests cover connection pooling behavior including:
//! - Pool exhaustion scenarios
//! - Connection timeouts
//! - Connection leaks and recovery
//! - Concurrent access patterns
//! - Connection lifecycle (max lifetime, idle timeout)
//! - Failure scenarios and recovery
//! - Transaction rollback and cleanup
//!
//! Requires a running PostgreSQL database:
//! ```bash
//! docker-compose up -d postgres
//! ```

use config::database::PoolConfig;
use database::{DatabaseError, DatabasePool};
use futures::stream::StreamExt;
use sqlx::Acquire;
use std::sync::Arc;
use std::time::Duration;
use tokio::time::{sleep, timeout};

/// Helper to create a test pool configuration
fn create_test_pool_config(max_connections: u32, min_connections: u32) -> PoolConfig {
    PoolConfig {
        max_connections,
        min_connections,
        acquire_timeout_secs: 5,
        idle_timeout_secs: 30,
        max_lifetime_secs: 60,
        test_before_acquire: true,
        database_url: "postgresql://foxhunt:foxhunt_dev_password@localhost:5432/foxhunt"
            .to_string(),
        health_check_enabled: false, // Disable for deterministic testing
        health_check_interval_secs: 60,
    }
}

/// Helper to create a pool for testing
async fn create_test_pool(
    max_connections: u32,
    min_connections: u32,
) -> Result<DatabasePool, DatabaseError> {
    let config = create_test_pool_config(max_connections, min_connections);
    DatabasePool::new(config).await
}

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

    #[tokio::test]
    async fn test_pool_exhaustion_with_small_pool() {
        let pool = create_test_pool(2, 1).await.expect("Pool creation failed");

        // Acquire all available connections
        let conn1 = pool.acquire().await.expect("First connection failed");
        let conn2 = pool.acquire().await.expect("Second connection failed");

        // Next request should timeout
        let result = timeout(Duration::from_millis(100), pool.acquire()).await;
        assert!(result.is_err(), "Should timeout when pool is exhausted");

        // Return one connection to pool
        drop(conn1);

        // Should now succeed
        let conn3 = pool.acquire().await;
        assert!(conn3.is_ok(), "Should succeed after connection returned");

        drop(conn2);
        drop(conn3);
        pool.close().await;
    }

    #[tokio::test]
    async fn test_pool_exhaustion_recovery() {
        let pool = create_test_pool(3, 1).await.expect("Pool creation failed");

        // Take all connections
        let tasks = futures::stream::FuturesUnordered::new();
        for _ in 0..3 {
            tasks.push(pool.acquire());
        }
        let conns: Vec<_> = tasks.collect::<Vec<_>>().await;

        assert_eq!(conns.len(), 3);
        assert!(conns.iter().all(|c| c.is_ok()));

        // Pool should be exhausted
        let result = timeout(Duration::from_millis(100), pool.acquire()).await;
        assert!(result.is_err());

        // Release all connections
        drop(conns);

        // Pool should recover immediately
        for _ in 0..3 {
            let conn = pool.acquire().await;
            assert!(
                conn.is_ok(),
                "Pool should recover after all connections returned"
            );
        }

        pool.close().await;
    }

    #[tokio::test]
    async fn test_minimum_pool_size_single_connection() {
        // Test with minimum possible pool size
        let pool = create_test_pool(1, 1).await.expect("Pool creation failed");

        let conn1 = pool.acquire().await.expect("Should get connection");

        // Second request should timeout
        let result = timeout(Duration::from_millis(100), pool.acquire()).await;
        assert!(
            result.is_err(),
            "Should timeout with single connection pool"
        );

        drop(conn1);

        // Should succeed after release
        let conn2 = pool.acquire().await;
        assert!(conn2.is_ok());

        drop(conn2);
        pool.close().await;
    }

    #[tokio::test]
    async fn test_large_pool_no_exhaustion() {
        // Test with large pool size
        let pool = create_test_pool(100, 10)
            .await
            .expect("Pool creation failed");

        // Take many connections without exhaustion
        let mut conns = Vec::new();
        for _ in 0..50 {
            let conn = pool.acquire().await.expect("Should not exhaust large pool");
            conns.push(conn);
        }

        // Should still have capacity
        let extra = pool.acquire().await;
        assert!(extra.is_ok(), "Large pool should still have capacity");

        drop(conns);
        drop(extra);
        pool.close().await;
    }
}

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

    #[tokio::test]
    async fn test_concurrent_connection_requests() {
        let pool = Arc::new(create_test_pool(10, 2).await.expect("Pool creation failed"));
        let mut handles = vec![];

        // Spawn 50 concurrent tasks requesting connections
        for i in 0..50 {
            let pool_clone = pool.clone();
            let handle = tokio::spawn(async move {
                let _conn = pool_clone
                    .acquire()
                    .await
                    .expect(&format!("Task {} failed to acquire connection", i));

                // Hold connection briefly
                sleep(Duration::from_millis(10)).await;
            });
            handles.push(handle);
        }

        // All tasks should complete successfully
        for handle in handles {
            handle.await.expect("Task should complete");
        }

        pool.close().await;
    }

    #[tokio::test]
    async fn test_high_concurrency_stress() {
        let pool = Arc::new(create_test_pool(20, 5).await.expect("Pool creation failed"));
        let mut handles = vec![];

        // Spawn 200 tasks with high contention
        for i in 0..200 {
            let pool_clone = pool.clone();
            let handle = tokio::spawn(async move {
                let _conn = pool_clone
                    .acquire()
                    .await
                    .expect(&format!("Task {} failed to acquire", i));

                // Very brief hold time to create high turnover
                sleep(Duration::from_millis(1)).await;
            });
            handles.push(handle);
        }

        for handle in handles {
            handle.await.expect("High concurrency task should complete");
        }

        pool.close().await;
    }

    #[tokio::test]
    async fn test_concurrent_with_timeouts() {
        let pool = Arc::new(create_test_pool(5, 1).await.expect("Pool creation failed"));
        let mut handles = vec![];

        // Spawn more tasks than pool capacity
        for i in 0..15 {
            let pool_clone = pool.clone();
            let handle = tokio::spawn(async move {
                // Some tasks will timeout, others succeed
                let result = timeout(Duration::from_millis(500), pool_clone.acquire()).await;

                if result.is_ok() && result.unwrap().is_ok() {
                    sleep(Duration::from_millis(100)).await;
                }

                // Don't panic on timeout - it's expected
                i
            });
            handles.push(handle);
        }

        // Count successful vs timed out
        let mut succeeded = 0;
        for handle in handles {
            let _ = handle.await.expect("Task should complete");
            succeeded += 1;
        }

        assert_eq!(succeeded, 15, "All tasks should complete");
        pool.close().await;
    }

    #[tokio::test]
    async fn test_sequential_vs_concurrent_performance() {
        let pool = create_test_pool(10, 2).await.expect("Pool creation failed");

        // Sequential acquisitions
        let sequential_start = std::time::Instant::now();
        for _ in 0..20 {
            let _conn = pool.acquire().await.expect("Sequential acquire failed");
            sleep(Duration::from_millis(5)).await;
        }
        let sequential_duration = sequential_start.elapsed();

        // Reset pool stats
        pool.reset_stats().await;

        // Concurrent acquisitions
        let pool = Arc::new(pool);
        let concurrent_start = std::time::Instant::now();

        let handles: Vec<_> = (0..20)
            .map(|_| {
                let pool_clone = pool.clone();
                tokio::spawn(async move {
                    let _conn = pool_clone
                        .acquire()
                        .await
                        .expect("Concurrent acquire failed");
                    sleep(Duration::from_millis(5)).await;
                })
            })
            .collect();

        for handle in handles {
            handle.await.expect("Concurrent task failed");
        }
        let concurrent_duration = concurrent_start.elapsed();

        // Concurrent should be faster (or at least not much slower)
        assert!(
            concurrent_duration < sequential_duration * 2,
            "Concurrent should be reasonably efficient"
        );

        pool.close().await;
    }
}

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

    #[tokio::test]
    async fn test_acquire_timeout_honored() {
        // Create pool with very short timeout
        let mut config = create_test_pool_config(2, 1);
        config.acquire_timeout_secs = 1; // 1 second timeout

        let pool = DatabasePool::new(config)
            .await
            .expect("Pool creation failed");

        // Take all connections
        let _conn1 = pool.acquire().await.expect("First acquire failed");
        let _conn2 = pool.acquire().await.expect("Second acquire failed");

        // Next acquire should timeout within ~1 second
        let start = std::time::Instant::now();
        let result = pool.acquire().await;
        let elapsed = start.elapsed();

        assert!(result.is_err(), "Should timeout");
        assert!(
            elapsed < Duration::from_secs(2),
            "Timeout should be honored"
        );

        pool.close().await;
    }

    #[tokio::test]
    async fn test_zero_timeout_immediate_failure() {
        // Very short timeout for immediate failure
        let mut config = create_test_pool_config(1, 1);
        config.acquire_timeout_secs = 1;

        let pool = DatabasePool::new(config)
            .await
            .expect("Pool creation failed");

        let _conn = pool.acquire().await.expect("First acquire failed");

        // Should fail almost immediately
        let start = std::time::Instant::now();
        let result = timeout(Duration::from_millis(100), pool.acquire()).await;
        let elapsed = start.elapsed();

        assert!(result.is_err() || result.unwrap().is_err());
        assert!(elapsed < Duration::from_millis(200), "Should fail quickly");

        pool.close().await;
    }

    #[tokio::test]
    async fn test_long_timeout_eventually_succeeds() {
        let mut config = create_test_pool_config(2, 1);
        config.acquire_timeout_secs = 10; // Long timeout

        let pool = Arc::new(
            DatabasePool::new(config)
                .await
                .expect("Pool creation failed"),
        );

        // Take all connections
        let conn1 = pool.acquire().await.expect("First acquire failed");
        let conn2 = pool.acquire().await.expect("Second acquire failed");

        // Spawn task that will release connection after delay
        tokio::spawn(async move {
            let _c1 = conn1;
            let _c2 = conn2;
            sleep(Duration::from_millis(500)).await;
            // Connections dropped here
        });

        // Should succeed once connection is released
        let result = pool.acquire().await;
        assert!(result.is_ok(), "Should succeed with long timeout");

        pool.close().await;
    }
}

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

    #[tokio::test]
    async fn test_connection_max_lifetime() {
        let mut config = create_test_pool_config(5, 2);
        config.max_lifetime_secs = 2; // Very short lifetime
        config.idle_timeout_secs = 10; // Longer idle timeout

        let pool = DatabasePool::new(config)
            .await
            .expect("Pool creation failed");

        // Acquire and use a connection
        let conn = pool.acquire().await.expect("Acquire failed");
        drop(conn);

        // Wait for connection to exceed max lifetime
        sleep(Duration::from_secs(3)).await;

        // Acquire again - should get a fresh connection
        let conn2 = pool.acquire().await.expect("Should get fresh connection");
        drop(conn2);

        pool.close().await;
    }

    #[tokio::test]
    async fn test_connection_idle_timeout() {
        let mut config = create_test_pool_config(10, 2);
        config.idle_timeout_secs = 2; // Short idle timeout
        config.max_lifetime_secs = 60; // Long max lifetime

        let pool = DatabasePool::new(config)
            .await
            .expect("Pool creation failed");

        // Create connections
        let tasks = futures::stream::FuturesUnordered::new();
        for _ in 0..5 {
            tasks.push(pool.acquire());
        }
        let conns: Vec<_> = tasks.collect::<Vec<_>>().await;

        // Release all connections
        drop(conns);

        // Wait for idle timeout
        sleep(Duration::from_secs(3)).await;

        // Pool should have cleaned up idle connections
        let idle_count = pool.num_idle();
        assert!(
            idle_count >= 2,
            "Should maintain minimum connections: {}",
            idle_count
        );

        pool.close().await;
    }

    #[tokio::test]
    async fn test_pool_maintains_minimum_connections() {
        let config = create_test_pool_config(10, 5);
        let pool = DatabasePool::new(config)
            .await
            .expect("Pool creation failed");

        // Wait for pool to initialize
        sleep(Duration::from_millis(500)).await;

        // Check pool size is at least minimum
        let size = pool.size();
        assert!(
            size >= 5,
            "Pool should maintain minimum connections, got {}",
            size
        );

        pool.close().await;
    }

    #[tokio::test]
    async fn test_connection_recreation_after_expiry() {
        let mut config = create_test_pool_config(3, 1);
        config.max_lifetime_secs = 1;

        let pool = DatabasePool::new(config)
            .await
            .expect("Pool creation failed");

        let initial_size = pool.size();

        // Use connections
        for _ in 0..5 {
            let _conn = pool.acquire().await.expect("Acquire failed");
            sleep(Duration::from_millis(100)).await;
        }

        // Wait for connections to expire
        sleep(Duration::from_secs(2)).await;

        // Acquire new connections - should recreate
        let _conn = pool.acquire().await.expect("Should recreate connection");

        let final_size = pool.size();
        assert!(
            final_size >= 1,
            "Pool should recreate connections: initial={}, final={}",
            initial_size,
            final_size
        );

        pool.close().await;
    }
}

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

    #[tokio::test]
    async fn test_invalid_connection_string() {
        let mut config = create_test_pool_config(5, 2);
        config.database_url = "postgresql://invalid:invalid@nonexistent:9999/invalid".to_string();

        let result = DatabasePool::new(config).await;
        assert!(
            result.is_err(),
            "Should fail with invalid connection string"
        );
    }

    #[tokio::test]
    async fn test_connection_validation_before_acquire() {
        let mut config = create_test_pool_config(5, 2);
        config.test_before_acquire = true;

        let pool = DatabasePool::new(config)
            .await
            .expect("Pool creation failed");

        // Acquire connection with validation
        let mut conn = pool
            .acquire()
            .await
            .expect("Acquire with validation failed");

        // Connection should be valid
        let result = sqlx::query("SELECT 1").fetch_one(&mut *conn).await;
        assert!(result.is_ok(), "Connection should be valid");

        pool.close().await;
    }

    #[tokio::test]
    async fn test_pool_recovery_after_close() {
        let pool = create_test_pool(5, 2).await.expect("Pool creation failed");

        // Close the pool
        pool.close().await;
        assert!(pool.is_closed());

        // Attempts to acquire should fail
        let result = timeout(Duration::from_millis(100), pool.acquire()).await;
        assert!(
            result.is_err() || result.unwrap().is_err(),
            "Acquire should fail on closed pool"
        );
    }

    #[tokio::test]
    async fn test_graceful_pool_shutdown() {
        let pool = create_test_pool(5, 2).await.expect("Pool creation failed");

        // Acquire some connections
        let tasks = futures::stream::FuturesUnordered::new();
        for _ in 0..3 {
            tasks.push(pool.acquire());
        }
        let conns: Vec<_> = tasks.collect::<Vec<_>>().await;

        // Close pool
        pool.close().await;

        // Existing connections should still work
        for conn in conns {
            if let Ok(mut c) = conn {
                let result = sqlx::query("SELECT 1").fetch_one(&mut *c).await;
                assert!(result.is_ok(), "Existing connection should still work");
            }
        }
    }

    #[tokio::test]
    async fn test_pool_health_check() {
        let pool = create_test_pool(5, 2).await.expect("Pool creation failed");

        let health = pool.health_check().await.expect("Health check failed");
        assert!(health, "Pool should be healthy");

        pool.close().await;

        // Health check on closed pool
        let health_after_close = pool.health_check().await;
        assert!(
            !health_after_close.unwrap_or(false),
            "Closed pool should be unhealthy"
        );
    }
}

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

    #[tokio::test]
    async fn test_transaction_connection_returned_on_commit() {
        let pool = create_test_pool(3, 1).await.expect("Pool creation failed");

        let initial_idle = pool.num_idle();

        {
            let mut conn = pool.acquire().await.expect("Acquire failed");
            let mut tx = conn.begin().await.expect("Begin transaction failed");

            sqlx::query("SELECT 1")
                .execute(&mut *tx)
                .await
                .expect("Query failed");

            tx.commit().await.expect("Commit failed");
        } // Connection dropped here

        // Wait for connection to return to pool
        sleep(Duration::from_millis(100)).await;

        let final_idle = pool.num_idle();
        assert!(
            final_idle >= initial_idle,
            "Connection should return to pool after commit"
        );

        pool.close().await;
    }

    #[tokio::test]
    async fn test_transaction_connection_returned_on_rollback() {
        let pool = create_test_pool(3, 1).await.expect("Pool creation failed");

        let initial_idle = pool.num_idle();

        {
            let mut conn = pool.acquire().await.expect("Acquire failed");
            let mut tx = conn.begin().await.expect("Begin transaction failed");

            sqlx::query("SELECT 1")
                .execute(&mut *tx)
                .await
                .expect("Query failed");

            tx.rollback().await.expect("Rollback failed");
        } // Connection dropped here

        // Wait for connection to return to pool
        sleep(Duration::from_millis(100)).await;

        let final_idle = pool.num_idle();
        assert!(
            final_idle >= initial_idle,
            "Connection should return to pool after rollback"
        );

        pool.close().await;
    }

    #[tokio::test]
    async fn test_failed_transaction_cleanup() {
        let pool = create_test_pool(3, 1).await.expect("Pool creation failed");

        let initial_idle = pool.num_idle();

        {
            let mut conn = pool.acquire().await.expect("Acquire failed");
            let mut tx = conn.begin().await.expect("Begin transaction failed");

            // Execute invalid query to cause failure
            let _ = sqlx::query("SELECT * FROM nonexistent_table_xyz")
                .execute(&mut *tx)
                .await;

            // Transaction will be rolled back on drop
        } // Connection dropped here

        // Wait for cleanup
        sleep(Duration::from_millis(100)).await;

        // Connection should still return to pool despite failed transaction
        let final_idle = pool.num_idle();
        assert!(
            final_idle >= initial_idle,
            "Connection should return even after failed transaction"
        );

        pool.close().await;
    }
}

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

    #[tokio::test]
    async fn test_pool_stats_acquisition_tracking() {
        let pool = create_test_pool(5, 2).await.expect("Pool creation failed");

        pool.reset_stats().await;

        // Perform acquisitions
        for _ in 0..10 {
            let _conn = pool.acquire().await.expect("Acquire failed");
        }

        let stats = pool.stats().await;
        assert_eq!(
            stats.total_acquisitions, 10,
            "Should track total acquisitions"
        );

        pool.close().await;
    }

    #[tokio::test]
    async fn test_pool_stats_failed_acquisitions() {
        let pool = create_test_pool(2, 1).await.expect("Pool creation failed");

        pool.reset_stats().await;

        // Take all connections
        let _conn1 = pool.acquire().await.expect("First acquire failed");
        let _conn2 = pool.acquire().await.expect("Second acquire failed");

        // Try to acquire more (will timeout and fail)
        for _ in 0..3 {
            let _ = timeout(Duration::from_millis(50), pool.acquire()).await;
        }

        let stats = pool.stats().await;
        assert!(
            stats.total_acquisitions >= 5,
            "Should track all acquisition attempts"
        );

        pool.close().await;
    }

    #[tokio::test]
    async fn test_pool_stats_reset() {
        let pool = create_test_pool(5, 2).await.expect("Pool creation failed");

        // Perform some operations
        for _ in 0..5 {
            let _conn = pool.acquire().await.expect("Acquire failed");
        }

        let stats_before = pool.stats().await;
        assert!(stats_before.total_acquisitions > 0);

        // Reset stats
        pool.reset_stats().await;

        let stats_after = pool.stats().await;
        assert_eq!(stats_after.total_acquisitions, 0, "Stats should be reset");

        pool.close().await;
    }

    #[tokio::test]
    async fn test_pool_size_metrics() {
        let pool = create_test_pool(10, 3).await.expect("Pool creation failed");

        // Wait for minimum connections to be established
        sleep(Duration::from_millis(500)).await;

        let size = pool.size();
        let idle = pool.num_idle();

        assert!(size >= 3, "Pool size should be at least minimum: {}", size);
        assert!(idle <= size as usize, "Idle cannot exceed total size");

        // Acquire connections
        let tasks = futures::stream::FuturesUnordered::new();
        for _ in 0..5 {
            tasks.push(pool.acquire());
        }
        let conns: Vec<_> = tasks.collect::<Vec<_>>().await;

        let idle_after = pool.num_idle();

        assert!(
            idle_after < idle,
            "Idle connections should decrease after acquisitions"
        );

        drop(conns);
        pool.close().await;
    }
}

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

    #[tokio::test]
    async fn test_invalid_min_max_configuration() {
        let mut config = create_test_pool_config(5, 10);
        config.min_connections = 10; // Min > Max
        config.max_connections = 5;

        let result = DatabasePool::new(config).await;
        assert!(result.is_err(), "Should reject min > max configuration");
    }

    #[tokio::test]
    async fn test_zero_max_connections() {
        let mut config = create_test_pool_config(0, 0);
        config.max_connections = 0;

        let result = DatabasePool::new(config).await;
        assert!(result.is_err(), "Should reject zero max connections");
    }

    #[tokio::test]
    async fn test_invalid_database_url() {
        let mut config = create_test_pool_config(5, 2);
        config.database_url = "not-a-valid-url".to_string();

        let result = DatabasePool::new(config).await;
        assert!(result.is_err(), "Should reject invalid database URL");
    }

    #[tokio::test]
    async fn test_min_equals_max_configuration() {
        let pool = create_test_pool(5, 5).await.expect("Pool creation failed");

        sleep(Duration::from_millis(500)).await;

        let size = pool.size();
        assert_eq!(size, 5, "Pool should maintain fixed size when min=max");

        pool.close().await;
    }
}