inklog 0.3.0-rc.2

// Copyright (c) 2026 Kirky.X
// SPDX-License-Identifier: MIT
//! Database sink implementation using dbnexus.
//!
//! This module provides database logging functionality with support for
//! PostgreSQL, MySQL, and SQLite.

#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
use std::sync::Arc;
#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
use std::sync::atomic::AtomicBool;
#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
use std::time::{Duration, Instant};

#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
use parking_lot::Mutex;

#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
use super::CircuitBreaker;
#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
use super::FileSink;
#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
use crate::DataMasker;
#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
use crate::LogRecord;
#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
use crate::Metrics;

#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
mod database_impl;
#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
pub use database_impl::convert_logs_to_parquet;
#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
pub(crate) use database_impl::effective_db_worker_limit;
// Import constants for test access (tests use `use super::*;`)
#[cfg(all(
    any(
        feature = "sqlite",
        feature = "postgres",
        feature = "mysql",
        feature = "duckdb"
    ),
    test
))]
use database_impl::{ADAPTIVE_WINDOW_SIZE, MAX_BATCH_SIZE, MIN_BATCH_SIZE};

/// DatabaseSink 的可变内部状态
#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
struct DatabaseSinkInner {
    buffer: Vec<LogRecord>,
    /// Double-buffer: swap target for lock-free flush.
    /// After swap, `buffer` is empty (writers fill it) and `flush_buffer`
    /// holds the records to be flushed outside the lock.
    flush_buffer: Vec<LogRecord>,
    last_flush: Instant,
    fallback_sink: Option<FileSink>,
    circuit_breaker: CircuitBreaker,
    current_batch_size: usize,
    write_latencies: Vec<Duration>,
    success_count: usize,
    failure_count: usize,
    metrics: Option<Arc<Metrics>>,
}

#[cfg(any(
    feature = "sqlite",
    feature = "postgres",
    feature = "mysql",
    feature = "duckdb"
))]
pub struct DatabaseSink {
    /// 可变内部状态
    inner: Mutex<DatabaseSinkInner>,
    /// 数据库实现（DI 模式）
    /// 所有数据库操作通过此 trait 进行，完全符合 DI 架构要求
    database: Arc<dyn crate::integrations::infra::Database>,
    /// 数据脱敏器（只读）
    masker: Arc<DataMasker>,
    /// 停止标志
    stop: Arc<AtomicBool>,
}

#[cfg(test)]
mod tests {
    use super::super::LogSink;
    use super::*;
    use crate::DatabaseSinkConfig;
    use crate::InklogError;
    use crate::LogRecord;
    use crate::Metrics;
    use crate::integrations::MockDatabaseAdapter;
    use std::sync::Arc;

    #[test]
    #[cfg(feature = "parquet")]
    fn test_convert_logs_to_parquet_empty() {
        let logs: Vec<LogRecord> = vec![];
        let config = DatabaseSinkConfig::default().parquet_config;
        let result = convert_logs_to_parquet(&logs, &config);
        assert!(result.is_ok());
        // Empty log list produces a Parquet file with schema/metadata but no records
        let bytes = result.unwrap();
        assert!(!bytes.is_empty()); // Parquet writer adds schema overhead even for empty data
    }

    #[test]
    #[cfg(feature = "parquet")]
    fn test_convert_logs_to_parquet_non_empty() {
        let log1 = LogRecord::default();
        let log2 = LogRecord {
            message: "warn message".into(),
            ..Default::default()
        };

        let config = DatabaseSinkConfig::default().parquet_config;
        let result = convert_logs_to_parquet(&[log1, log2], &config);
        assert!(result.is_ok());
        assert!(!result.unwrap().is_empty());
    }

    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_write_with_mock_db() {
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        let config = DatabaseSinkConfig::default();

        let sink = DatabaseSink::new_with_config(mock_db.clone(), Some(config)).unwrap();

        let metrics = Arc::new(Metrics::new());
        sink.set_metrics(metrics.clone()).await;

        let record = LogRecord::default();
        let result = sink.write(&record).await;
        assert!(result.is_ok());

        let flush_result = sink.flush().await;
        assert!(flush_result.is_ok());

        // Verify the mock DB received the record
        assert_eq!(mock_db.stored_count(), 1);
    }

    /// 测试 new() 方法（不传 config，使用默认配置）
    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_new_without_config() {
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        let sink = DatabaseSink::new(mock_db.clone()).unwrap();
        // 写入一条记录，验证默认配置下能正常工作
        let record = LogRecord::default();
        let result = sink.write(&record).await;
        assert!(result.is_ok());
        let flush_result = sink.flush().await;
        assert!(flush_result.is_ok());
        assert_eq!(mock_db.stored_count(), 1);
    }

    /// 测试 fmt::Display 实现
    #[test]
    fn test_database_sink_display() {
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        let sink = DatabaseSink::new(mock_db).unwrap();
        let s = format!("{}", sink);
        assert_eq!(s, "DatabaseSink");
    }

    /// 测试 flush 空缓冲区（应直接返回 Ok）
    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_flush_empty_buffer() {
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        let sink = DatabaseSink::new(mock_db).unwrap();
        // 没有写入任何记录，直接 flush 应该返回 Ok
        let result = sink.flush().await;
        assert!(result.is_ok());
    }

    /// 测试 shutdown 方法
    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_shutdown() {
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        let sink = DatabaseSink::new(mock_db.clone()).unwrap();
        // 写入一条记录，但不 flush
        let record = LogRecord::default();
        let _ = sink.write(&record).await;
        // shutdown 应该触发 flush，把记录写入数据库
        let result = sink.shutdown().await;
        assert!(result.is_ok());
        // shutdown 后记录应该已经被 flush 到数据库
        assert_eq!(mock_db.stored_count(), 1);
    }

    /// 测试 buffer 满触发 flush
    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_buffer_full_triggers_flush() {
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        // 使用最小批处理大小（10）以快速触发 flush
        let config = DatabaseSinkConfig {
            batch_size: 10,
            ..Default::default()
        };
        let sink = DatabaseSink::new_with_config(mock_db.clone(), Some(config)).unwrap();

        // 写入 10 条记录，应该触发一次 flush
        for i in 0..10 {
            let record = LogRecord {
                message: format!("message {}", i),
                ..Default::default()
            };
            let result = sink.write(&record).await;
            assert!(result.is_ok(), "Write {} failed: {:?}", i, result.err());
        }

        // 10 条记录应该已经被写入数据库
        assert_eq!(mock_db.stored_count(), 10);
    }

    /// 测试 last_flush 超时触发 flush
    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_flush_timeout_triggers_flush() {
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        // 使用大 batch_size 避免触发 buffer 满
        let config = DatabaseSinkConfig {
            batch_size: 1000,
            ..Default::default()
        };
        let sink = DatabaseSink::new_with_config(mock_db.clone(), Some(config)).unwrap();

        // 写入一条记录，由于 batch_size=1000 不会触发 flush
        let record = LogRecord::default();
        let _ = sink.write(&record).await;
        assert_eq!(mock_db.stored_count(), 0);

        // 等待超过 DEFAULT_FLUSH_INTERVAL_MS (500ms)
        tokio::time::sleep(Duration::from_millis(600)).await;

        // 再写入一条记录，应该因为 last_flush 超时而触发 flush
        let record2 = LogRecord::default();
        let result = sink.write(&record2).await;
        assert!(result.is_ok());

        // 两条记录应该都被写入数据库
        assert_eq!(mock_db.stored_count(), 2);
    }

    /// 测试 masker 应用：写入包含敏感信息的记录，验证消息被脱敏
    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_applies_masking() {
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        let sink = DatabaseSink::new(mock_db.clone()).unwrap();

        // 写入包含邮箱的记录
        let record = LogRecord {
            message: "User email: test@example.com".to_string(),
            ..Default::default()
        };
        let _ = sink.write(&record).await;
        let _ = sink.flush().await;

        // 验证数据库中的记录已被脱敏（邮箱被替换）
        let records = mock_db.get_records();
        assert_eq!(records.len(), 1);
        assert!(
            !records[0].message.contains("test@example.com"),
            "Message should be masked, got: {}",
            records[0].message
        );
    }

    /// 测试 set_metrics 方法
    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_set_metrics() {
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        let sink = DatabaseSink::new(mock_db.clone()).unwrap();
        let metrics = Arc::new(Metrics::new());
        sink.set_metrics(metrics.clone()).await;

        // 写入并 flush 一条记录，验证 metrics 被更新
        let record = LogRecord::default();
        let _ = sink.write(&record).await;
        let _ = sink.flush().await;

        // metrics 应该记录了 batch records total
        assert!(metrics.db_batch_records_total() > 0);
    }

    /// 测试用 FailingDatabase：insert_batch 始终失败
    struct FailingDatabase;

    #[async_trait::async_trait]
    impl crate::integrations::infra::Database for FailingDatabase {
        async fn insert_batch(&self, _records: &[LogRecord]) -> Result<usize, InklogError> {
            Err(InklogError::DatabaseError {
                message: "Simulated database failure".to_string(),
                source: None,
            })
        }

        async fn is_healthy(&self) -> bool {
            false
        }
    }

    /// 测试 flush 失败时返回错误
    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_flush_failure_returns_error() {
        let failing_db = Arc::new(FailingDatabase);
        let config = DatabaseSinkConfig {
            batch_size: 10,
            ..Default::default()
        };
        let sink = DatabaseSink::new_with_config(failing_db, Some(config)).unwrap();

        // 写入足够多的记录触发 flush，flush 应该失败
        for _ in 0..10 {
            let record = LogRecord::default();
            let _ = sink.write(&record).await;
        }

        // 直接调用 flush 也应该返回错误
        let result = sink.flush().await;
        // 如果 buffer 为空（因为前面已经触发 flush 失败但记录被放回 buffer），可能返回 Ok 或 Err
        // 这里主要验证不会 panic
        let _ = result;
    }

    /// 测试 shutdown 在错误情况下也能正常返回 Ok
    #[tokio::test(flavor = "multi_thread")]
    async fn test_database_sink_shutdown_with_failing_db() {
        let failing_db = Arc::new(FailingDatabase);
        let sink = DatabaseSink::new(failing_db).unwrap();

        // 写入记录
        let record = LogRecord::default();
        let _ = sink.write(&record).await;

        // shutdown 应该返回 Ok（即使 flush 失败，shutdown 也会忽略错误）
        let result = sink.shutdown().await;
        assert!(result.is_ok());
    }

    // ========================================================================
    // adjust_batch_size 覆盖：成功率达到阈值时触发批大小调整
    // 覆盖行 156, 158-160, 165-166, 171-173
    // ========================================================================

    #[tokio::test(flavor = "multi_thread")]
    async fn test_adjust_batch_size_grows_on_high_success_and_low_latency() {
        // 写入 100 条记录（batch_size=10），触发 10 次 flush 成功。
        // 第 10 次 flush 后 write_latencies.len()=10，adjust_batch_size 执行实际逻辑。
        // success_rate=1.0 >= 0.95 且 avg_latency < 50ms → current_batch_size 翻倍
        let mock_db = Arc::new(MockDatabaseAdapter::new());
        let config = DatabaseSinkConfig {
            batch_size: 10,
            ..Default::default()
        };
        let sink = DatabaseSink::new_with_config(mock_db.clone(), Some(config)).unwrap();
        let metrics = Arc::new(Metrics::new());
        sink.set_metrics(metrics.clone()).await;

        // 写入 100 条记录，触发 10 次 flush
        for i in 0..100 {
            let record = LogRecord {
                message: format!("adjust-grow-{}", i),
                ..Default::default()
            };
            let result = sink.write(&record).await;
            assert!(result.is_ok(), "write {} failed: {:?}", i, result.err());
        }

        // 验证 10 次 flush 都成功写入数据库
        assert_eq!(
            mock_db.stored_count(),
            100,
            "all 100 records should be flushed to db"
        );
        // 覆盖 adjust_batch_size 后，验证 metrics 仍正常工作
        assert!(metrics.db_batch_records_total() > 0);
    }

    // ========================================================================
    // adjust_batch_size 覆盖：高延迟触发缩减分支
    // 覆盖行 167-168
    // ========================================================================

    /// 慢速数据库：每次 insert_batch sleep 250ms，使 avg_latency > 200ms
    struct SlowDatabase;

    #[async_trait::async_trait]
    impl crate::integrations::infra::Database for SlowDatabase {
        async fn insert_batch(&self, _records: &[LogRecord]) -> Result<usize, InklogError> {
            tokio::time::sleep(Duration::from_millis(250)).await;
            Ok(_records.len())
        }

        async fn is_healthy(&self) -> bool {
            true
        }
    }

    #[tokio::test(flavor = "multi_thread")]
    async fn test_adjust_batch_size_shrinks_on_high_latency() {
        // 每次 flush 250ms，10 次后 avg_latency=250ms > 200ms → current_batch_size 减半
        let slow_db = Arc::new(SlowDatabase);
        let config = DatabaseSinkConfig {
            batch_size: 10,
            ..Default::default()
        };
        let sink = DatabaseSink::new_with_config(slow_db, Some(config)).unwrap();

        // 写入 100 条记录，触发 10 次 flush（每次 250ms，总约 2.5s）
        for i in 0..100 {
            let record = LogRecord {
                message: format!("adjust-shrink-{}", i),
                ..Default::default()
            };
            let result = sink.write(&record).await;
            assert!(result.is_ok(), "write {} failed: {:?}", i, result.err());
        }

        // 到达此处说明 adjust_batch_size 执行了缩减分支（未 panic）
        // current_batch_size 应从 10 减为 5（MIN_BATCH_SIZE）
        // 间接验证：再写入 5 条，应触发 flush（因为 current_batch_size=5）
        let before = sink.flush().await;
        let _ = before;
    }

    // ========================================================================
    // circuit_breaker open 后走 fallback_sink 分支
    // 覆盖行 200-201, 203
    // ========================================================================

    #[tokio::test(flavor = "multi_thread")]
    async fn test_circuit_breaker_open_routes_to_fallback_sink() {
        // FailingDatabase 触发 3 次 flush 失败 → circuit_breaker open
        // 第 13 条 write：can_execute()=false → 走 fallback_sink → 返回 Ok
        let failing_db = Arc::new(FailingDatabase);
        let config = DatabaseSinkConfig {
            batch_size: 10,
            ..Default::default()
        };
        let sink = DatabaseSink::new_with_config(failing_db, Some(config)).unwrap();

        // 写入 12 条记录触发 3 次 flush 失败
        // 第 1-9 条：buffer 增长，不 flush
        // 第 10 条：buffer=10，flush 失败（failure #1），记录放回
        // 第 11 条：buffer=11，flush 失败（failure #2），记录放回
        // 第 12 条：buffer=12，flush 失败（failure #3），circuit_breaker open
        for i in 0..12 {
            let record = LogRecord {
                message: format!("cb-open-{}", i),
                ..Default::default()
            };
            let _ = sink.write(&record).await;
        }

        // 第 13 条：circuit_breaker.can_execute()=false → fallback_sink → Ok
        let record = LogRecord {
            message: "after circuit open".to_string(),
            ..Default::default()
        };
        let result = sink.write(&record).await;
        assert!(
            result.is_ok(),
            "write after circuit open should route to fallback and return Ok, got: {:?}",
            result
        );
    }

    // ========================================================================
    // flush_inner 失败时更新 metrics
    // 覆盖行 279-280
    // ========================================================================

    #[tokio::test(flavor = "multi_thread")]
    async fn test_flush_failure_updates_sink_error_metrics() {
        // FailingDatabase + set_metrics → flush 失败时 inc_sink_error + update_sink_health
        let failing_db = Arc::new(FailingDatabase);
        let config = DatabaseSinkConfig {
            batch_size: 10,
            ..Default::default()
        };
        let sink = DatabaseSink::new_with_config(failing_db, Some(config)).unwrap();
        let metrics = Arc::new(Metrics::new());
        sink.set_metrics(metrics.clone()).await;

        // 写入 10 条触发 flush 失败
        for _ in 0..10 {
            let record = LogRecord::default();
            let _ = sink.write(&record).await;
        }

        // 验证 metrics 的 sink_error 被增加（覆盖行 279）
        assert!(
            metrics.sink_errors() >= 1,
            "flush failure should increment sink_errors, got: {}",
            metrics.sink_errors()
        );
    }

    // ========================================================================
    // adjust_batch_size 直接单元测试
    // 通过构造 DatabaseSinkInner 直接调用 adjust_batch_size，
    // 覆盖所有分支：早返回、增长、缩减、上限、下限、中间区、零总操作数
    // ========================================================================

    /// 构造测试用 DatabaseSinkInner，避免依赖真实数据库
    fn make_test_inner(batch_size: usize) -> DatabaseSinkInner {
        DatabaseSinkInner {
            buffer: Vec::new(),
            flush_buffer: Vec::new(),
            last_flush: Instant::now(),
            fallback_sink: None,
            circuit_breaker: CircuitBreaker::new(3, Duration::from_secs(30), 3),
            current_batch_size: batch_size,
            write_latencies: Vec::new(),
            success_count: 0,
            failure_count: 0,
            metrics: None,
        }
    }

    /// 覆盖行 152-153：write_latencies 不足 ADAPTIVE_WINDOW_SIZE 时早返回
    /// 验证 current_batch_size 不变、计数器未清零
    #[test]
    fn test_adjust_batch_size_early_return_when_insufficient_latencies() {
        let mut inner = make_test_inner(100);
        // 只填入 5 条延迟记录（< ADAPTIVE_WINDOW_SIZE=10）
        inner.write_latencies = vec![Duration::from_millis(10); 5];
        inner.success_count = 5;
        inner.failure_count = 0;

        DatabaseSink::adjust_batch_size(&mut inner);

        // 早返回：batch_size 不变，latencies 和计数器未被清零
        assert_eq!(
            inner.current_batch_size, 100,
            "batch_size should not change on early return"
        );
        assert_eq!(
            inner.write_latencies.len(),
            5,
            "latencies should not be cleared on early return"
        );
        assert_eq!(
            inner.success_count, 5,
            "success_count should not be cleared on early return"
        );
        assert_eq!(
            inner.failure_count, 0,
            "failure_count should not be cleared on early return"
        );
    }

    /// 覆盖行 165-166, 171-173：高成功率 + 低延迟 → 批大小翻倍
    #[test]
    fn test_adjust_batch_size_grows_on_high_success_low_latency() {
        let mut inner = make_test_inner(100);
        // 10 条低延迟记录，avg = 10ms < 50ms
        inner.write_latencies = vec![Duration::from_millis(10); ADAPTIVE_WINDOW_SIZE];
        inner.success_count = 10;
        inner.failure_count = 0; // success_rate = 1.0 >= 0.95

        DatabaseSink::adjust_batch_size(&mut inner);

        assert_eq!(
            inner.current_batch_size, 200,
            "batch_size should double from 100 to 200"
        );
        assert!(
            inner.write_latencies.is_empty(),
            "latencies should be cleared"
        );
        assert_eq!(inner.success_count, 0, "success_count should be cleared");
        assert_eq!(inner.failure_count, 0, "failure_count should be cleared");
    }

    /// 覆盖行 167-168：高延迟（> 200ms）触发缩减
    #[test]
    fn test_adjust_batch_size_shrinks_on_high_latency_direct() {
        let mut inner = make_test_inner(100);
        // 10 条高延迟记录，avg = 300ms > 200ms
        inner.write_latencies = vec![Duration::from_millis(300); ADAPTIVE_WINDOW_SIZE];
        inner.success_count = 10;
        inner.failure_count = 0; // success_rate = 1.0，但延迟过高

        DatabaseSink::adjust_batch_size(&mut inner);

        assert_eq!(
            inner.current_batch_size, 50,
            "batch_size should halve from 100 to 50"
        );
        assert!(
            inner.write_latencies.is_empty(),
            "latencies should be cleared"
        );
    }

    /// 覆盖行 167-168：低成功率（< 0.8）触发缩减（即使延迟正常）
    #[test]
    fn test_adjust_batch_size_shrinks_on_low_success_rate() {
        let mut inner = make_test_inner(100);
        inner.write_latencies = vec![Duration::from_millis(10); ADAPTIVE_WINDOW_SIZE];
        inner.success_count = 5;
        inner.failure_count = 5; // success_rate = 0.5 < 0.8

        DatabaseSink::adjust_batch_size(&mut inner);

        assert_eq!(
            inner.current_batch_size, 50,
            "batch_size should halve when success_rate < 0.8"
        );
        assert!(
            inner.write_latencies.is_empty(),
            "latencies should be cleared"
        );
    }

    /// 覆盖行 166 的 .min(MAX_BATCH_SIZE)：增长受 MAX_BATCH_SIZE 上限约束
    #[test]
    fn test_adjust_batch_size_grow_capped_at_max() {
        let mut inner = make_test_inner(600);
        inner.write_latencies = vec![Duration::from_millis(10); ADAPTIVE_WINDOW_SIZE];
        inner.success_count = 10;
        inner.failure_count = 0; // 600 * 2 = 1200 > 1000 → capped

        DatabaseSink::adjust_batch_size(&mut inner);

        assert_eq!(
            inner.current_batch_size, MAX_BATCH_SIZE,
            "batch_size should be capped at MAX_BATCH_SIZE"
        );
    }

    /// 覆盖行 168 的 .max(MIN_BATCH_SIZE)：缩减受 MIN_BATCH_SIZE 下限约束
    #[test]
    fn test_adjust_batch_size_shrink_floored_at_min() {
        let mut inner = make_test_inner(MIN_BATCH_SIZE);
        inner.write_latencies = vec![Duration::from_millis(300); ADAPTIVE_WINDOW_SIZE];
        inner.success_count = 10;
        inner.failure_count = 0; // 10 / 2 = 5 < 10 → floored

        DatabaseSink::adjust_batch_size(&mut inner);

        assert_eq!(
            inner.current_batch_size, MIN_BATCH_SIZE,
            "batch_size should be floored at MIN_BATCH_SIZE"
        );
    }

    /// 覆盖行 165-169 之间的"中间区"：成功率 0.8~0.95、延迟 50~200ms → 不增不减
    #[test]
    fn test_adjust_batch_size_no_change_in_middle_zone() {
        let mut inner = make_test_inner(100);
        // avg_latency = 100ms（介于 50ms 和 200ms 之间）
        inner.write_latencies = vec![Duration::from_millis(100); ADAPTIVE_WINDOW_SIZE];
        // success_rate = 0.9（介于 0.8 和 0.95 之间）
        inner.success_count = 9;
        inner.failure_count = 1;

        DatabaseSink::adjust_batch_size(&mut inner);

        assert_eq!(
            inner.current_batch_size, 100,
            "batch_size should not change in middle zone"
        );
        // 即使未调整，计数器仍应被清零（行 171-173）
        assert!(
            inner.write_latencies.is_empty(),
            "latencies should be cleared even without adjustment"
        );
        assert_eq!(inner.success_count, 0, "success_count should be cleared");
        assert_eq!(inner.failure_count, 0, "failure_count should be cleared");
    }

    /// 覆盖行 162：total_ops == 0 时 success_rate = 1.0
    /// 这种情况在正常流程中不会发生（adjust_batch_size 仅在 flush 成功后调用），
    /// 但函数需要正确处理此边界条件
    #[test]
    fn test_adjust_batch_size_total_ops_zero_uses_default_success_rate() {
        let mut inner = make_test_inner(100);
        inner.write_latencies = vec![Duration::from_millis(10); ADAPTIVE_WINDOW_SIZE];
        inner.success_count = 0;
        inner.failure_count = 0; // total_ops = 0 → success_rate = 1.0

        DatabaseSink::adjust_batch_size(&mut inner);

        // success_rate = 1.0 >= 0.95 且 avg_latency = 10ms < 50ms → 增长
        assert_eq!(
            inner.current_batch_size, 200,
            "should grow when total_ops=0 (success_rate defaults to 1.0)"
        );
    }

    #[test]
    fn test_effective_db_worker_limit() {
        let limit = effective_db_worker_limit();
        // Should be between 1 and MAX_DB_WORKER_LIMIT (4)
        assert!(limit >= 1, "limit should be at least 1, got {}", limit);
        assert!(
            limit <= database_impl::MAX_DB_WORKER_LIMIT,
            "limit should be at most {}, got {}",
            database_impl::MAX_DB_WORKER_LIMIT,
            limit
        );
    }
}