use std::collections::{HashMap, BTreeMap, VecDeque};
use std::sync::Arc;
use std::time::{Duration, Instant};
use serde::{Deserialize, Serialize};
use tokio::sync::{RwLock, Mutex};
use tracing::{info, instrument};
use uuid::Uuid;
use chrono::{DateTime, Utc};
use sha2::{Sha256, Digest};

use crate::{
    Result, EtlError, DataRecord, DataValue,
    state::StateManager, monitoring::EtlMetrics,
};

/// Configuration for incremental processing
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct IncrementalConfig {
    /// Change detection strategy
    pub change_detection: ChangeDetectionStrategy,
    /// Checkpoint configuration
    pub checkpoint_config: CheckpointConfig,
    /// Deduplication strategy
    pub deduplication: DeduplicationStrategy,
    /// State retention policy
    pub state_retention: StateRetentionPolicy,
    /// Batch processing configuration
    pub batch_config: BatchConfig,
    /// Memory management configuration
    pub memory_config: MemoryConfig,
    /// Parallel processing configuration
    pub parallelism: ParallelismConfig,
}

impl Default for IncrementalConfig {
    fn default() -> Self {
        Self {
            change_detection: ChangeDetectionStrategy::TimestampBased {
                column: "updated_at".to_string(),
                format: TimestampFormat::Iso8601,
            },
            checkpoint_config: CheckpointConfig::default(),
            deduplication: DeduplicationStrategy::Hash {
                hash_columns: vec!["id".to_string()],
                hash_algorithm: HashAlgorithm::Sha256,
            },
            state_retention: StateRetentionPolicy::TimeBased {
                retention_period: Duration::from_secs(7 * 24 * 3600), // 7 days
            },
            batch_config: BatchConfig::default(),
            memory_config: MemoryConfig::default(),
            parallelism: ParallelismConfig::default(),
        }
    }
}

/// Incremental processor for handling change data capture and delta processing
pub struct IncrementalProcessor {
    /// Configuration
    config: IncrementalConfig,
    /// State manager for persistence
    state_manager: Arc<StateManager>,
    /// Metrics collector
    metrics: Arc<EtlMetrics>,
    /// Change detector
    change_detector: Arc<ChangeDetector>,
    /// Checkpoint manager
    checkpoint_manager: Arc<CheckpointManager>,
    /// Deduplicator
    deduplicator: Arc<Deduplicator>,
    /// State tracker for incremental processing
    state_tracker: Arc<RwLock<StateTracker>>,
    /// Watermark manager
    watermark_manager: Arc<WatermarkManager>,
    /// Merge processor
    merge_processor: Arc<MergeProcessor>,
}

/// Strategies for detecting changes in data
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ChangeDetectionStrategy {
    /// Timestamp-based change detection
    TimestampBased {
        /// Column name containing timestamp
        column: String,
        /// Timestamp format
        format: TimestampFormat,
    },
    /// Version-based change detection
    VersionBased {
        /// Column name containing version
        column: String,
        /// Version comparison strategy
        comparison: VersionComparison,
    },
    /// Hash-based change detection
    HashBased {
        /// Columns to include in hash
        columns: Vec<String>,
        /// Hash algorithm to use
        algorithm: HashAlgorithm,
    },
    /// Log-based change detection (CDC)
    LogBased {
        /// Log source configuration
        log_source: LogSourceConfig,
    },
    /// Trigger-based change detection
    TriggerBased {
        /// Trigger configuration
        trigger_config: TriggerConfig,
    },
}

/// Timestamp format options
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum TimestampFormat {
    /// ISO 8601 format
    Iso8601,
    /// Unix timestamp (seconds)
    UnixSeconds,
    /// Unix timestamp (milliseconds)
    UnixMilliseconds,
    /// Custom format string
    Custom(String),
}

/// Version comparison strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum VersionComparison {
    /// Numeric comparison
    Numeric,
    /// Semantic versioning
    Semantic,
    /// String comparison
    Lexicographic,
}

/// Hash algorithms for change detection
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum HashAlgorithm {
    /// MD5 hash
    Md5,
    /// SHA-256 hash
    Sha256,
    /// SHA-512 hash
    Sha512,
    /// CRC32 checksum
    Crc32,
}

/// Log source configuration for CDC
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LogSourceConfig {
    /// Log source type
    pub source_type: LogSourceType,
    /// Connection configuration
    pub connection: LogConnectionConfig,
    /// Filter configuration
    pub filters: Vec<LogFilter>,
}

/// Types of log sources for CDC
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum LogSourceType {
    /// Database transaction log
    DatabaseLog {
        /// Database type
        db_type: DatabaseType,
    },
    /// Kafka changelog topic
    KafkaChangelog {
        /// Topic name
        topic: String,
    },
    /// File-based changelog
    FileChangelog {
        /// File pattern
        pattern: String,
    },
}

/// Database types for log-based CDC
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum DatabaseType {
    /// `PostgreSQL`
    PostgreSQL,
    /// `MySQL`
    MySQL,
    /// SQL Server
    SqlServer,
    /// Oracle
    Oracle,
    /// `MongoDB`
    MongoDB,
}

/// Connection configuration for log sources
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LogConnectionConfig {
    /// Connection string
    pub connection_string: String,
    /// Authentication configuration
    pub auth: Option<AuthConfig>,
    /// Connection pool configuration
    pub pool_config: Option<PoolConfig>,
}

/// Authentication configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AuthConfig {
    /// Username
    pub username: String,
    /// Password
    pub password: String,
    /// Additional authentication parameters
    pub params: HashMap<String, String>,
}

/// Connection pool configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PoolConfig {
    /// Maximum connections
    pub max_connections: u32,
    /// Minimum connections
    pub min_connections: u32,
    /// Connection timeout
    pub connection_timeout: Duration,
}

/// Log filter configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LogFilter {
    /// Filter type
    pub filter_type: LogFilterType,
    /// Filter expression
    pub expression: String,
}

/// Types of log filters
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum LogFilterType {
    /// Table/collection filter
    Table,
    /// Operation filter (INSERT, UPDATE, DELETE)
    Operation,
    /// Column filter
    Column,
    /// Custom filter
    Custom,
}

/// Trigger configuration for change detection
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TriggerConfig {
    /// Trigger source
    pub source: TriggerSource,
    /// Trigger conditions
    pub conditions: Vec<TriggerCondition>,
}

/// Trigger source types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum TriggerSource {
    /// Database trigger
    Database {
        /// Table name
        table: String,
        /// Trigger events
        events: Vec<TriggerEvent>,
    },
    /// File system watcher
    FileSystem {
        /// Path to watch
        path: String,
        /// File patterns
        patterns: Vec<String>,
    },
    /// External API webhook
    Webhook {
        /// Webhook endpoint
        endpoint: String,
    },
}

/// Database trigger events
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum TriggerEvent {
    /// Insert event
    Insert,
    /// Update event
    Update,
    /// Delete event
    Delete,
}

/// Trigger condition
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TriggerCondition {
    /// Column name
    pub column: String,
    /// Condition operator
    pub operator: ComparisonOperator,
    /// Value to compare against
    pub value: DataValue,
}

/// Comparison operators for conditions
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ComparisonOperator {
    /// Equal
    Eq,
    /// Not equal
    Ne,
    /// Greater than
    Gt,
    /// Greater than or equal
    Gte,
    /// Less than
    Lt,
    /// Less than or equal
    Lte,
    /// In list
    In,
    /// Not in list
    NotIn,
    /// Like pattern
    Like,
    /// Regex match
    Regex,
}

/// Configuration for checkpointing
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CheckpointConfig {
    /// Checkpoint strategy
    pub strategy: CheckpointStrategy,
    /// Checkpoint interval
    pub interval: Duration,
    /// Maximum checkpoint size
    pub max_size_bytes: usize,
    /// Checkpoint retention
    pub retention: CheckpointRetention,
    /// Compression configuration
    pub compression: Option<CompressionConfig>,
}

impl Default for CheckpointConfig {
    fn default() -> Self {
        Self {
            strategy: CheckpointStrategy::Periodic,
            interval: Duration::from_secs(300), // 5 minutes
            max_size_bytes: 100 * 1024 * 1024, // 100 MB
            retention: CheckpointRetention::Count(10),
            compression: Some(CompressionConfig {
                algorithm: CompressionAlgorithm::Gzip,
                level: 6,
            }),
        }
    }
}

/// Checkpoint strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum CheckpointStrategy {
    /// Periodic checkpointing
    Periodic,
    /// Size-based checkpointing
    SizeBased {
        /// Threshold size in bytes
        threshold_bytes: usize,
    },
    /// Count-based checkpointing
    CountBased {
        /// Record count threshold
        threshold_count: usize,
    },
    /// Time and size based
    Hybrid {
        /// Time threshold
        time_threshold: Duration,
        /// Size threshold
        size_threshold: usize,
    },
}

/// Checkpoint retention policies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum CheckpointRetention {
    /// Keep a specific number of checkpoints
    Count(usize),
    /// Keep checkpoints for a specific duration
    Time(Duration),
    /// Keep checkpoints based on size limit
    Size(usize),
}

/// Compression configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CompressionConfig {
    /// Compression algorithm
    pub algorithm: CompressionAlgorithm,
    /// Compression level
    pub level: u32,
}

/// Compression algorithms
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum CompressionAlgorithm {
    /// Gzip compression
    Gzip,
    /// LZ4 compression
    Lz4,
    /// Zstd compression
    Zstd,
    /// Snappy compression
    Snappy,
}

/// Deduplication strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum DeduplicationStrategy {
    /// Hash-based deduplication
    Hash {
        /// Columns to include in hash
        hash_columns: Vec<String>,
        /// Hash algorithm
        hash_algorithm: HashAlgorithm,
    },
    /// Key-based deduplication
    Key {
        /// Key columns
        key_columns: Vec<String>,
    },
    /// Bloom filter based deduplication
    BloomFilter {
        /// Expected number of elements
        expected_elements: usize,
        /// False positive probability
        false_positive_rate: f64,
    },
    /// No deduplication
    None,
}

/// State retention policies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum StateRetentionPolicy {
    /// Time-based retention
    TimeBased {
        /// Retention period
        retention_period: Duration,
    },
    /// Size-based retention
    SizeBased {
        /// Maximum state size in bytes
        max_size_bytes: usize,
    },
    /// Count-based retention
    CountBased {
        /// Maximum number of state entries
        max_count: usize,
    },
    /// No retention (keep forever)
    None,
}

/// Batch processing configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BatchConfig {
    /// Batch size (number of records)
    pub batch_size: usize,
    /// Maximum batch processing time
    pub max_batch_time: Duration,
    /// Batch timeout
    pub batch_timeout: Duration,
    /// Enable adaptive batching
    pub adaptive_batching: bool,
}

impl Default for BatchConfig {
    fn default() -> Self {
        Self {
            batch_size: 1000,
            max_batch_time: Duration::from_secs(30),
            batch_timeout: Duration::from_secs(60),
            adaptive_batching: true,
        }
    }
}

/// Memory management configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MemoryConfig {
    /// Maximum memory usage in bytes
    pub max_memory_bytes: usize,
    /// Memory pressure threshold (0.0 to 1.0)
    pub pressure_threshold: f64,
    /// Enable memory compaction
    pub enable_compaction: bool,
    /// Garbage collection interval
    pub gc_interval: Duration,
}

impl Default for MemoryConfig {
    fn default() -> Self {
        Self {
            max_memory_bytes: 1024 * 1024 * 1024, // 1 GB
            pressure_threshold: 0.8,
            enable_compaction: true,
            gc_interval: Duration::from_secs(60),
        }
    }
}

/// Parallelism configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ParallelismConfig {
    /// Number of parallel workers
    pub worker_count: usize,
    /// Work stealing enabled
    pub work_stealing: bool,
    /// Load balancing strategy
    pub load_balancing: LoadBalancingStrategy,
}

impl Default for ParallelismConfig {
    fn default() -> Self {
        Self {
            worker_count: num_cpus::get(),
            work_stealing: true,
            load_balancing: LoadBalancingStrategy::RoundRobin,
        }
    }
}

/// Load balancing strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum LoadBalancingStrategy {
    /// Round-robin assignment
    RoundRobin,
    /// Least connections
    LeastConnections,
    /// Hash-based assignment
    Hash {
        /// Hash key column
        key_column: String,
    },
    /// Random assignment
    Random,
}

/// Change detector for identifying data changes
#[derive(Debug)]
pub struct ChangeDetector {
    /// Detection strategy
    strategy: ChangeDetectionStrategy,
    /// State tracker
    state_tracker: Arc<RwLock<ChangeState>>,
}

/// State for tracking changes
#[derive(Debug)]
pub struct ChangeState {
    /// Last processed timestamps per source
    last_timestamps: HashMap<String, DateTime<Utc>>,
    /// Last processed versions per source
    last_versions: HashMap<String, String>,
    /// Hash signatures for change detection
    hash_signatures: HashMap<String, String>,
    /// Change log entries
    change_log: BTreeMap<DateTime<Utc>, ChangeEntry>,
}

/// Entry in the change log
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ChangeEntry {
    /// Change identifier
    pub change_id: String,
    /// Change type
    pub change_type: ChangeType,
    /// Source record identifier
    pub source_record_id: String,
    /// Change timestamp
    pub timestamp: DateTime<Utc>,
    /// Changed fields
    pub changed_fields: Vec<String>,
    /// Old values (for updates)
    pub old_values: Option<HashMap<String, DataValue>>,
    /// New values
    pub new_values: HashMap<String, DataValue>,
}

/// Types of changes
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ChangeType {
    /// Insert operation
    Insert,
    /// Update operation
    Update,
    /// Delete operation
    Delete,
    /// Upsert operation
    Upsert,
}

/// Checkpoint manager for state persistence
#[derive(Debug)]
pub struct CheckpointManager {
    /// Checkpoint configuration
    config: CheckpointConfig,
    /// State manager
    state_manager: Arc<StateManager>,
    /// Active checkpoints
    active_checkpoints: Arc<RwLock<HashMap<String, Checkpoint>>>,
}

/// Checkpoint representing a point-in-time state
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Checkpoint {
    /// Checkpoint identifier
    pub checkpoint_id: String,
    /// Checkpoint timestamp
    pub timestamp: DateTime<Utc>,
    /// Source watermarks at checkpoint time
    pub watermarks: HashMap<String, DateTime<Utc>>,
    /// Processing state snapshot
    pub state_snapshot: StateSnapshot,
    /// Checkpoint metadata
    pub metadata: CheckpointMetadata,
}

/// Snapshot of processing state
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct StateSnapshot {
    /// Processed record counts per source
    pub record_counts: HashMap<String, u64>,
    /// Bytes processed per source
    pub bytes_processed: HashMap<String, u64>,
    /// Last processed positions
    pub positions: HashMap<String, ProcessingPosition>,
    /// State checksums for validation
    pub checksums: HashMap<String, String>,
}

/// Processing position for resuming from checkpoint
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ProcessingPosition {
    /// Source identifier
    pub source_id: String,
    /// Position type
    pub position_type: PositionType,
    /// Position value
    pub position_value: String,
    /// Position timestamp
    pub timestamp: DateTime<Utc>,
}

/// Types of processing positions
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum PositionType {
    /// Timestamp-based position
    Timestamp,
    /// Sequence number position
    SequenceNumber,
    /// Log sequence number
    LogSequenceNumber,
    /// File offset position
    FileOffset,
    /// Custom position type
    Custom(String),
}

/// Checkpoint metadata
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CheckpointMetadata {
    /// Checkpoint size in bytes
    pub size_bytes: usize,
    /// Compression used
    pub compression: Option<CompressionAlgorithm>,
    /// Checksum for validation
    pub checksum: String,
    /// Creation duration
    pub creation_duration_ms: u64,
}

/// Deduplicator for removing duplicate records
#[derive(Debug)]
pub struct Deduplicator {
    /// Deduplication strategy
    strategy: DeduplicationStrategy,
    /// Deduplication cache
    cache: Arc<RwLock<DeduplicationCache>>,
}

/// Cache for deduplication
#[derive(Debug)]
pub struct DeduplicationCache {
    /// Hash-based cache
    hash_cache: HashMap<String, CacheEntry>,
    /// Key-based cache
    key_cache: HashMap<String, CacheEntry>,
    /// Bloom filter for approximate deduplication
    bloom_filter: Option<BloomFilter>,
}

/// Cache entry for deduplication
#[derive(Debug, Clone)]
pub struct CacheEntry {
    /// Record hash or key
    pub identifier: String,
    /// First seen timestamp
    pub first_seen: DateTime<Utc>,
    /// Last seen timestamp
    pub last_seen: DateTime<Utc>,
    /// Occurrence count
    pub count: u64,
}

/// Bloom filter for approximate deduplication
#[derive(Debug)]
pub struct BloomFilter {
    /// Bit array
    bits: Vec<bool>,
    /// Hash functions count
    hash_functions: usize,
    /// Expected elements
    expected_elements: usize,
    /// Current element count
    current_count: usize,
}

/// State tracker for incremental processing
#[derive(Debug)]
pub struct StateTracker {
    /// Processing state per source
    source_states: HashMap<String, SourceState>,
    /// Global processing statistics
    global_stats: ProcessingStats,
    /// Error tracking
    error_tracker: ErrorTracker,
}

/// State for individual data source
#[derive(Debug)]
pub struct SourceState {
    /// Source identifier
    pub source_id: String,
    /// Last processing watermark
    pub watermark: Option<DateTime<Utc>>,
    /// Records processed count
    pub records_processed: u64,
    /// Bytes processed count
    pub bytes_processed: u64,
    /// Last error encountered
    pub last_error: Option<ProcessingError>,
    /// Processing lag metrics
    pub lag_metrics: LagMetrics,
}

/// Processing statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ProcessingStats {
    /// Total records processed
    pub total_records: u64,
    /// Total bytes processed
    pub total_bytes: u64,
    /// Processing start time
    pub start_time: DateTime<Utc>,
    /// Last processing time
    pub last_processing_time: Option<DateTime<Utc>>,
    /// Processing rate (records per second)
    pub processing_rate: f64,
    /// Throughput (bytes per second)
    pub throughput: f64,
}

/// Error tracking for processing issues
#[derive(Debug)]
pub struct ErrorTracker {
    /// Error history
    pub error_history: VecDeque<ProcessingError>,
    /// Error counts by type
    pub error_counts: HashMap<String, u64>,
    /// Last error time
    pub last_error_time: Option<DateTime<Utc>>,
}

/// Processing error information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ProcessingError {
    /// Error identifier
    pub error_id: String,
    /// Error type
    pub error_type: String,
    /// Error message
    pub message: String,
    /// Error timestamp
    pub timestamp: DateTime<Utc>,
    /// Source that caused the error
    pub source_id: Option<String>,
    /// Record that caused the error
    pub record_id: Option<String>,
    /// Stack trace
    pub stack_trace: Option<String>,
}

/// Lag metrics for processing delay tracking
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LagMetrics {
    /// Current lag in milliseconds
    pub current_lag_ms: u64,
    /// Average lag in milliseconds
    pub average_lag_ms: f64,
    /// Maximum lag seen
    pub max_lag_ms: u64,
    /// Lag trend (increasing/decreasing)
    pub trend: LagTrend,
}

/// Lag trend indicators
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum LagTrend {
    /// Lag is increasing
    Increasing,
    /// Lag is decreasing
    Decreasing,
    /// Lag is stable
    Stable,
}

/// Watermark manager for incremental processing
#[derive(Debug)]
pub struct WatermarkManager {
    /// Watermarks per source
    source_watermarks: Arc<RwLock<HashMap<String, DateTime<Utc>>>>,
    /// Global watermark
    global_watermark: Arc<RwLock<Option<DateTime<Utc>>>>,
    /// Watermark update listeners
    listeners: Arc<Mutex<Vec<tokio::sync::mpsc::UnboundedSender<WatermarkUpdate>>>>,
}

/// Watermark update notification
#[derive(Debug, Clone)]
pub struct WatermarkUpdate {
    /// Source identifier
    pub source_id: String,
    /// New watermark
    pub watermark: DateTime<Utc>,
    /// Update timestamp
    pub update_time: DateTime<Utc>,
}

/// Merge processor for combining incremental changes
#[derive(Debug)]
pub struct MergeProcessor {
    /// Merge strategies by table/collection
    strategies: HashMap<String, MergeStrategy>,
    /// Conflict resolution rules
    conflict_rules: Vec<ConflictResolutionRule>,
}

/// Strategies for merging data
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum MergeStrategy {
    /// Append new records only
    Append,
    /// Update existing records, insert new ones
    Upsert {
        /// Key columns for matching
        key_columns: Vec<String>,
    },
    /// Overwrite entire dataset
    Overwrite,
    /// Merge with conflict resolution
    Merge {
        /// Key columns for matching
        key_columns: Vec<String>,
        /// Conflict resolution strategy
        conflict_resolution: ConflictResolution,
    },
    /// Time-based merge (keep latest)
    TimeBased {
        /// Timestamp column
        timestamp_column: String,
    },
}

/// Conflict resolution strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ConflictResolution {
    /// Keep source value (incoming data wins)
    Source,
    /// Keep target value (existing data wins)
    Target,
    /// Use last writer wins
    LastWriter,
    /// Use timestamp-based resolution
    Timestamp {
        /// Timestamp column
        column: String,
    },
    /// Custom resolution logic
    Custom(String),
}

/// Rule for resolving conflicts during merge
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ConflictResolutionRule {
    /// Rule identifier
    pub rule_id: String,
    /// Table/collection pattern
    pub table_pattern: String,
    /// Column pattern
    pub column_pattern: Option<String>,
    /// Resolution strategy
    pub resolution: ConflictResolution,
    /// Rule priority (higher numbers take precedence)
    pub priority: i32,
}

impl IncrementalProcessor {
    /// Create a new incremental processor
    pub async fn new(
        config: IncrementalConfig,
        state_manager: Arc<StateManager>,
        metrics: Arc<EtlMetrics>,
    ) -> Result<Self> {
        let change_detector = Arc::new(ChangeDetector::new(config.change_detection.clone()).await?);
        let checkpoint_manager = Arc::new(CheckpointManager::new(
            config.checkpoint_config.clone(),
            state_manager.clone(),
        ));
        let deduplicator = Arc::new(Deduplicator::new(config.deduplication.clone()).await?);
        let state_tracker = Arc::new(RwLock::new(StateTracker::new()));
        let watermark_manager = Arc::new(WatermarkManager::new());
        let merge_processor = Arc::new(MergeProcessor::new());
        
        Ok(Self {
            config,
            state_manager,
            metrics,
            change_detector,
            checkpoint_manager,
            deduplicator,
            state_tracker,
            watermark_manager,
            merge_processor,
        })
    }
    
    /// Detect changes since last checkpoint
    #[instrument(skip(self))]
    pub async fn detect_changes(
        &self,
        source: &str,
        checkpoint: Option<Checkpoint>,
    ) -> Result<ChangeSet> {
        info!("Detecting changes for source: {}", source);
        
        let start_position = if let Some(ref cp) = checkpoint {
            cp.state_snapshot.positions.get(source).cloned()
        } else {
            None
        };
        
        self.change_detector.detect_changes(source, start_position).await
    }
    
    /// Process incremental changes
    #[instrument(skip(self, changes))]
    pub async fn process_changes(&self, changes: ChangeSet) -> Result<ProcessedChanges> {
        let mut processed = ProcessedChanges {
            change_set_id: changes.change_set_id.clone(),
            processed_count: 0,
            skipped_count: 0,
            error_count: 0,
            processing_time: Instant::now(),
            records: Vec::new(),
            errors: Vec::new(),
        };
        
        for change_batch in &changes.batches {
            let batch_result = self.process_change_batch(change_batch.clone()).await?;
            processed.processed_count += batch_result.processed_count;
            processed.skipped_count += batch_result.skipped_count;
            processed.error_count += batch_result.error_count;
            processed.records.extend(batch_result.records);
            processed.errors.extend(batch_result.errors);
        }
        
        // Update watermarks
        self.update_watermarks(&changes).await?;
        
        Ok(processed)
    }
    
    /// Process a single batch of changes
    async fn process_change_batch(&self, batch: ChangeBatch) -> Result<ProcessedChanges> {
        let mut result = ProcessedChanges {
            change_set_id: batch.batch_id.clone(),
            processed_count: 0,
            skipped_count: 0,
            error_count: 0,
            processing_time: Instant::now(),
            records: Vec::new(),
            errors: Vec::new(),
        };
        
        for change in batch.changes {
            match self.process_single_change(change).await {
                Ok(record) => {
                    result.records.push(record);
                    result.processed_count += 1;
                }
                Err(e) => {
                    result.errors.push(ProcessingError {
                        error_id: Uuid::new_v4().to_string(),
                        error_type: "processing_error".to_string(),
                        message: e.to_string(),
                        timestamp: Utc::now(),
                        source_id: Some(batch.source_id.clone()),
                        record_id: None,
                        stack_trace: None,
                    });
                    result.error_count += 1;
                }
            }
        }
        
        Ok(result)
    }
    
    /// Process a single change entry
    async fn process_single_change(&self, change: ChangeEntry) -> Result<DataRecord> {
        // Apply deduplication
        if !self.deduplicator.should_process(&change).await? {
            return Err(EtlError::IncrementalProcessing("Record is duplicate".to_string()));
        }
        
        // Convert change to data record
        let record = DataRecord {
            id: Uuid::new_v4(),
            event_time: change.timestamp,
            process_time: Utc::now(),
            partition_key: Some(change.source_record_id.clone()),
            data: crate::DataPayload::Structured(change.new_values),
            metadata: crate::RecordMetadata {
                source: "incremental_processor".to_string(),
                lineage: Vec::new(),
                quality_scores: None,
                attributes: HashMap::new(),
                schema_version: None,
                checksum: None,
            },
        };
        
        Ok(record)
    }
    
    /// Update watermarks based on processed changes
    async fn update_watermarks(&self, changes: &ChangeSet) -> Result<()> {
        for batch in &changes.batches {
            if let Some(max_timestamp) = batch.max_timestamp {
                self.watermark_manager.update_watermark(&batch.source_id, max_timestamp).await?;
            }
        }
        Ok(())
    }
    
    /// Create a checkpoint of current processing state
    #[instrument(skip(self))]
    pub async fn create_checkpoint(&self, checkpoint_id: &str) -> Result<Checkpoint> {
        info!("Creating checkpoint: {}", checkpoint_id);
        let start_time = Instant::now();

        let watermarks = self.watermark_manager.get_all_watermarks().await;
        let state_tracker = self.state_tracker.read().await;

        let positions: HashMap<String, ProcessingPosition> = state_tracker
            .source_states
            .iter()
            .map(|(source_id, state)| {
                (
                    source_id.clone(),
                    ProcessingPosition {
                        source_id: source_id.clone(),
                        position_type: PositionType::Timestamp,
                        position_value: state.watermark
                            .unwrap_or_else(Utc::now)
                            .to_rfc3339(),
                        timestamp: Utc::now(),
                    }
                )
            })
            .collect();

        let record_counts: HashMap<String, u64> = state_tracker
            .source_states
            .iter()
            .map(|(source_id, state)| (source_id.clone(), state.records_processed))
            .collect();

        let bytes_processed: HashMap<String, u64> = state_tracker
            .source_states
            .iter()
            .map(|(source_id, state)| (source_id.clone(), state.bytes_processed))
            .collect();

        // Calculate checksums for each source state
        let checksums: HashMap<String, String> = state_tracker
            .source_states
            .iter()
            .map(|(source_id, state)| {
                let mut hasher = Sha256::new();
                hasher.update(source_id.as_bytes());
                hasher.update(state.records_processed.to_le_bytes());
                if let Some(watermark) = state.watermark {
                    hasher.update(watermark.to_rfc3339().as_bytes());
                }
                hasher.update(state.bytes_processed.to_le_bytes());
                let hash = format!("{:x}", hasher.finalize());
                (source_id.clone(), hash)
            })
            .collect();

        let state_snapshot = StateSnapshot {
            record_counts,
            bytes_processed,
            positions,
            checksums,
        };

        // Calculate checkpoint size by serializing it
        let snapshot_bytes = serde_json::to_vec(&state_snapshot)
            .map_err(EtlError::Serde)?;
        let watermarks_bytes = serde_json::to_vec(&watermarks)
            .map_err(EtlError::Serde)?;
        let total_size = snapshot_bytes.len() + watermarks_bytes.len() + checkpoint_id.len();

        // Calculate checkpoint checksum
        let mut checkpoint_hasher = Sha256::new();
        checkpoint_hasher.update(checkpoint_id.as_bytes());
        checkpoint_hasher.update(&snapshot_bytes);
        checkpoint_hasher.update(&watermarks_bytes);
        let checkpoint_checksum = format!("{:x}", checkpoint_hasher.finalize());

        let creation_duration = start_time.elapsed();

        let checkpoint = Checkpoint {
            checkpoint_id: checkpoint_id.to_string(),
            timestamp: Utc::now(),
            watermarks,
            state_snapshot,
            metadata: CheckpointMetadata {
                size_bytes: total_size,
                compression: self.config.checkpoint_config.compression.as_ref().map(|c| c.algorithm.clone()),
                checksum: checkpoint_checksum,
                creation_duration_ms: creation_duration.as_millis() as u64,
            },
        };

        // Persist checkpoint
        self.checkpoint_manager.save_checkpoint(&checkpoint).await?;

        Ok(checkpoint)
    }
    
    /// Load a checkpoint and restore processing state
    #[instrument(skip(self))]
    pub async fn load_checkpoint(&self, checkpoint_id: &str) -> Result<Checkpoint> {
        info!("Loading checkpoint: {}", checkpoint_id);
        
        let checkpoint = self.checkpoint_manager.load_checkpoint(checkpoint_id).await?;
        
        // Restore watermarks
        for (source_id, watermark) in &checkpoint.watermarks {
            self.watermark_manager.update_watermark(source_id, *watermark).await?;
        }
        
        // Restore state tracker
        {
            let mut state_tracker = self.state_tracker.write().await;
            for (source_id, position) in &checkpoint.state_snapshot.positions {
                let record_count = checkpoint.state_snapshot.record_counts
                    .get(source_id)
                    .copied()
                    .unwrap_or(0);

                let bytes_count = checkpoint.state_snapshot.bytes_processed
                    .get(source_id)
                    .copied()
                    .unwrap_or(0);

                state_tracker.source_states.insert(
                    source_id.clone(),
                    SourceState {
                        source_id: source_id.clone(),
                        watermark: Some(position.timestamp),
                        records_processed: record_count,
                        bytes_processed: bytes_count,
                        last_error: None,
                        lag_metrics: LagMetrics {
                            current_lag_ms: 0,
                            average_lag_ms: 0.0,
                            max_lag_ms: 0,
                            trend: LagTrend::Stable,
                        },
                    }
                );
            }
        }
        
        info!("Checkpoint loaded successfully: {}", checkpoint_id);
        Ok(checkpoint)
    }
    
    /// Apply merge strategy to integrate incremental changes
    #[instrument(skip(self, changes))]
    pub async fn merge_changes(
        &self,
        target: &str,
        changes: ProcessedChanges,
        strategy: MergeStrategy,
    ) -> Result<MergeResult> {
        self.merge_processor.merge(target, changes, strategy).await
    }
}

/// Set of changes detected from a source
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ChangeSet {
    /// Change set identifier
    pub change_set_id: String,
    /// Source identifier
    pub source_id: String,
    /// Detection timestamp
    pub detection_time: DateTime<Utc>,
    /// Time range of changes
    pub time_range: (DateTime<Utc>, DateTime<Utc>),
    /// Total number of changes
    pub total_changes: usize,
    /// Changes grouped into batches
    pub batches: Vec<ChangeBatch>,
}

/// Batch of changes for processing
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ChangeBatch {
    /// Batch identifier
    pub batch_id: String,
    /// Source identifier
    pub source_id: String,
    /// Changes in this batch
    pub changes: Vec<ChangeEntry>,
    /// Batch sequence number
    pub sequence: u64,
    /// Maximum timestamp in batch
    pub max_timestamp: Option<DateTime<Utc>>,
    /// Minimum timestamp in batch
    pub min_timestamp: Option<DateTime<Utc>>,
}

/// Result of processing changes
#[derive(Debug)]
pub struct ProcessedChanges {
    /// Change set identifier
    pub change_set_id: String,
    /// Number of successfully processed records
    pub processed_count: u64,
    /// Number of skipped records
    pub skipped_count: u64,
    /// Number of error records
    pub error_count: u64,
    /// Processing start time
    pub processing_time: Instant,
    /// Processed records
    pub records: Vec<DataRecord>,
    /// Processing errors
    pub errors: Vec<ProcessingError>,
}

/// Result of merge operation
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MergeResult {
    /// Target identifier
    pub target: String,
    /// Merge strategy used
    pub strategy: MergeStrategy,
    /// Number of records inserted
    pub inserted_count: u64,
    /// Number of records updated
    pub updated_count: u64,
    /// Number of records deleted
    pub deleted_count: u64,
    /// Number of conflicts resolved
    pub conflicts_resolved: u64,
    /// Merge duration
    pub duration_ms: u64,
    /// Merge errors
    pub errors: Vec<String>,
}

// Implementation stubs for the various components
impl ChangeDetector {
    pub async fn new(strategy: ChangeDetectionStrategy) -> Result<Self> {
        Ok(Self {
            strategy,
            state_tracker: Arc::new(RwLock::new(ChangeState {
                last_timestamps: HashMap::new(),
                last_versions: HashMap::new(),
                hash_signatures: HashMap::new(),
                change_log: BTreeMap::new(),
            })),
        })
    }

    pub async fn detect_changes(&self, source: &str, position: Option<ProcessingPosition>) -> Result<ChangeSet> {
        let detection_start = Utc::now();
        let mut changes = Vec::new();

        // Get the starting position for change detection
        let start_position = position.unwrap_or_else(|| ProcessingPosition {
            source_id: source.to_string(),
            position_type: PositionType::Timestamp,
            position_value: Utc::now().to_rfc3339(),
            timestamp: Utc::now(),
        });

        // Perform change detection based on strategy
        match &self.strategy {
            ChangeDetectionStrategy::TimestampBased { column, format } => {
                changes = self.detect_timestamp_changes(source, column, format, &start_position).await?;
            },
            ChangeDetectionStrategy::HashBased { columns, algorithm } => {
                changes = self.detect_hash_changes(source, columns, algorithm, &start_position).await?;
            },
            ChangeDetectionStrategy::VersionBased { column, comparison } => {
                changes = self.detect_version_changes(source, column, comparison, &start_position).await?;
            },
            ChangeDetectionStrategy::LogBased { log_source } => {
                changes = self.detect_log_changes(source, log_source, &start_position).await?;
            },
            ChangeDetectionStrategy::TriggerBased { trigger_config } => {
                changes = self.detect_trigger_changes(source, trigger_config, &start_position).await?;
            },
        }

        // Group changes into batches
        let batches = self.group_changes_into_batches(changes, 1000).await?;
        let total_changes = batches.iter().map(|b| b.changes.len()).sum();

        // Update state tracker
        self.update_detection_state(source, &batches).await?;

        // Calculate time range
        let min_time = batches.iter()
            .filter_map(|b| b.min_timestamp)
            .min()
            .unwrap_or(detection_start);
        let max_time = batches.iter()
            .filter_map(|b| b.max_timestamp)
            .max()
            .unwrap_or(detection_start);

        Ok(ChangeSet {
            change_set_id: Uuid::new_v4().to_string(),
            source_id: source.to_string(),
            detection_time: detection_start,
            time_range: (min_time, max_time),
            total_changes,
            batches,
        })
    }

    /// Detect changes based on timestamp comparison
    async fn detect_timestamp_changes(
        &self,
        source: &str,
        column: &str,
        format: &TimestampFormat,
        start_position: &ProcessingPosition,
    ) -> Result<Vec<ChangeEntry>> {
        let mut changes = Vec::new();

        // Get the last processed timestamp for this source
        let state = self.state_tracker.read().await;
        let last_timestamp = state.last_timestamps.get(source)
            .copied()
            .unwrap_or_else(|| {
                // Parse start position timestamp
                DateTime::parse_from_rfc3339(&start_position.position_value).map_or_else(|_| Utc::now(), |dt| dt.with_timezone(&Utc))
            });
        drop(state);

        // Simulate querying data source for records modified after last_timestamp
        // In a real implementation, this would query the actual data source
        let new_records = self.simulate_timestamp_query(source, column, format, last_timestamp).await?;

        // Convert records to change entries
        for record in new_records {
            let change_id = Uuid::new_v4().to_string();
            let change_type = if record.contains_key("_operation") {
                match record.get("_operation").and_then(super::DataValue::as_string) {
                    Some(op) if op == "INSERT" => ChangeType::Insert,
                    Some(op) if op == "UPDATE" => ChangeType::Update,
                    Some(op) if op == "DELETE" => ChangeType::Delete,
                    _ => ChangeType::Upsert,
                }
            } else {
                ChangeType::Upsert
            };

            let timestamp = record.get(column)
                .and_then(|v| match v {
                    DataValue::Timestamp(dt) => Some(*dt),
                    DataValue::String(s) => DateTime::parse_from_rfc3339(s).ok().map(|dt| dt.with_timezone(&Utc)),
                    _ => None,
                })
                .unwrap_or_else(Utc::now);

            changes.push(ChangeEntry {
                change_id,
                change_type,
                source_record_id: record.get("id")
                    .and_then(super::DataValue::as_string)
                    .unwrap_or_else(|| Uuid::new_v4().to_string()),
                timestamp,
                changed_fields: record.keys().cloned().collect(),
                old_values: None, // Would be populated for updates
                new_values: record,
            });
        }

        Ok(changes)
    }

    /// Detect changes based on hash comparison
    async fn detect_hash_changes(
        &self,
        source: &str,
        columns: &[String],
        algorithm: &HashAlgorithm,
        _start_position: &ProcessingPosition,
    ) -> Result<Vec<ChangeEntry>> {
        let mut changes = Vec::new();

        // Get current hash signatures
        let state = self.state_tracker.read().await;
        let existing_signatures = state.hash_signatures.clone();
        drop(state);

        // Simulate querying current data and calculating hashes
        let current_records = self.simulate_hash_query(source, columns).await?;

        for record in current_records {
            let record_id = record.get("id")
                .and_then(super::DataValue::as_string)
                .unwrap_or_else(|| Uuid::new_v4().to_string());

            // Calculate hash for specified columns
            let hash_value = self.calculate_record_hash(&record, columns, algorithm);
            let signature_key = format!("{source}:{record_id}");

            // Check if hash has changed
            let has_changed = existing_signatures.get(&signature_key) != Some(&hash_value);

            if has_changed {
                changes.push(ChangeEntry {
                    change_id: Uuid::new_v4().to_string(),
                    change_type: if existing_signatures.contains_key(&signature_key) {
                        ChangeType::Update
                    } else {
                        ChangeType::Insert
                    },
                    source_record_id: record_id,
                    timestamp: Utc::now(),
                    changed_fields: columns.to_vec(),
                    old_values: None,
                    new_values: record,
                });
            }
        }

        Ok(changes)
    }

    /// Detect changes based on version comparison
    async fn detect_version_changes(
        &self,
        source: &str,
        column: &str,
        comparison: &VersionComparison,
        _start_position: &ProcessingPosition,
    ) -> Result<Vec<ChangeEntry>> {
        let mut changes = Vec::new();

        // Get last processed versions
        let state = self.state_tracker.read().await;
        let last_versions = state.last_versions.clone();
        drop(state);

        // Simulate querying for version changes
        let records = self.simulate_version_query(source, column).await?;

        for record in records {
            let record_id = record.get("id")
                .and_then(super::DataValue::as_string)
                .unwrap_or_else(|| Uuid::new_v4().to_string());

            let current_version = record.get(column)
                .and_then(super::DataValue::as_string)
                .unwrap_or_else(|| "0".to_string());

            let version_key = format!("{source}:{record_id}");
            let last_version = last_versions.get(&version_key);

            let has_changed = match (last_version, comparison) {
                (Some(last), VersionComparison::Numeric) => {
                    let last_num: f64 = last.parse().unwrap_or(0.0);
                    let current_num: f64 = current_version.parse().unwrap_or(0.0);
                    current_num > last_num
                },
                (Some(last), VersionComparison::Lexicographic) => {
                    current_version > *last
                },
                (Some(last), VersionComparison::Semantic) => {
                    self.compare_semantic_versions(&current_version, last) > 0
                },
                (None, _) => true, // New record
            };

            if has_changed {
                changes.push(ChangeEntry {
                    change_id: Uuid::new_v4().to_string(),
                    change_type: if last_version.is_some() {
                        ChangeType::Update
                    } else {
                        ChangeType::Insert
                    },
                    source_record_id: record_id,
                    timestamp: Utc::now(),
                    changed_fields: record.keys().cloned().collect(),
                    old_values: None,
                    new_values: record,
                });
            }
        }

        Ok(changes)
    }

    /// Detect changes from log-based sources (CDC)
    async fn detect_log_changes(
        &self,
        _source: &str,
        log_source: &LogSourceConfig,
        _start_position: &ProcessingPosition,
    ) -> Result<Vec<ChangeEntry>> {
        let mut changes = Vec::new();

        // Simulate reading from CDC log source
        match &log_source.source_type {
            LogSourceType::DatabaseLog { db_type } => {
                changes = self.read_database_log(db_type, log_source).await?;
            },
            LogSourceType::KafkaChangelog { topic } => {
                changes = self.read_kafka_changelog(topic, log_source).await?;
            },
            LogSourceType::FileChangelog { pattern } => {
                changes = self.read_file_changelog(pattern, log_source).await?;
            },
        }

        Ok(changes)
    }

    /// Detect changes from trigger-based sources
    async fn detect_trigger_changes(
        &self,
        _source: &str,
        _trigger_config: &TriggerConfig,
        _start_position: &ProcessingPosition,
    ) -> Result<Vec<ChangeEntry>> {
        // Simplified implementation - would integrate with trigger systems
        Ok(vec![])
    }

    // Helper methods for simulating data source queries
    async fn simulate_timestamp_query(
        &self,
        _source: &str,
        _column: &str,
        _format: &TimestampFormat,
        _after: DateTime<Utc>,
    ) -> Result<Vec<HashMap<String, DataValue>>> {
        // Simulate returning some changed records
        let mut records = Vec::new();
        let now = Utc::now();

        for i in 0..5 {
            let mut record = HashMap::new();
            record.insert("id".to_string(), DataValue::String(format!("record_{i}")));
            record.insert("updated_at".to_string(), DataValue::Timestamp(now));
            record.insert("data".to_string(), DataValue::String(format!("data_value_{i}")));
            records.push(record);
        }

        Ok(records)
    }

    async fn simulate_hash_query(
        &self,
        _source: &str,
        _columns: &[String],
    ) -> Result<Vec<HashMap<String, DataValue>>> {
        // Simulate returning current records for hash comparison
        let mut records = Vec::new();

        for i in 0..3 {
            let mut record = HashMap::new();
            record.insert("id".to_string(), DataValue::String(format!("record_{i}")));
            record.insert("name".to_string(), DataValue::String(format!("name_{i}")));
            record.insert("value".to_string(), DataValue::Int(i64::from(i) * 10));
            records.push(record);
        }

        Ok(records)
    }

    async fn simulate_version_query(
        &self,
        _source: &str,
        _column: &str,
    ) -> Result<Vec<HashMap<String, DataValue>>> {
        // Simulate returning records with version information
        let mut records = Vec::new();

        for i in 0..3 {
            let mut record = HashMap::new();
            record.insert("id".to_string(), DataValue::String(format!("record_{i}")));
            record.insert("version".to_string(), DataValue::String(format!("1.{i}.0")));
            record.insert("data".to_string(), DataValue::String(format!("versioned_data_{i}")));
            records.push(record);
        }

        Ok(records)
    }

    /// Calculate hash for a record using specified algorithm
    fn calculate_record_hash(
        &self,
        record: &HashMap<String, DataValue>,
        columns: &[String],
        algorithm: &HashAlgorithm,
    ) -> String {
        use sha2::{Sha256, Digest};

        // Extract values for specified columns in deterministic order
        let mut values = Vec::new();
        for column in columns {
            if let Some(value) = record.get(column) {
                values.push(serde_json::to_string(value).unwrap_or_default());
            }
        }

        let combined = values.join("|");

        match algorithm {
            HashAlgorithm::Sha256 => {
                let mut hasher = Sha256::new();
                hasher.update(combined.as_bytes());
                format!("{:x}", hasher.finalize())
            },
            HashAlgorithm::Md5 => {
                // Simplified - would use actual MD5
                format!("md5_{}", combined.len())
            },
            HashAlgorithm::Sha512 => {
                // Simplified - would use actual SHA-512
                format!("sha512_{}", combined.len())
            },
            HashAlgorithm::Crc32 => {
                // Simplified - would use actual CRC32
                format!("crc32_{}", combined.len())
            },
        }
    }

    /// Compare semantic versions
    fn compare_semantic_versions(&self, version1: &str, version2: &str) -> i32 {
        let parse_version = |v: &str| -> Vec<u32> {
            v.split('.')
                .map(|part| part.parse().unwrap_or(0))
                .collect()
        };

        let v1 = parse_version(version1);
        let v2 = parse_version(version2);

        for i in 0..std::cmp::max(v1.len(), v2.len()) {
            let part1 = v1.get(i).unwrap_or(&0);
            let part2 = v2.get(i).unwrap_or(&0);

            match part1.cmp(part2) {
                std::cmp::Ordering::Greater => return 1,
                std::cmp::Ordering::Less => return -1,
                std::cmp::Ordering::Equal => continue,
            }
        }

        0
    }

    /// Group changes into processing batches
    async fn group_changes_into_batches(
        &self,
        changes: Vec<ChangeEntry>,
        batch_size: usize,
    ) -> Result<Vec<ChangeBatch>> {
        let mut batches = Vec::new();
        let mut current_batch = Vec::new();
        let mut sequence = 0u64;

        for change in changes {
            current_batch.push(change);

            if current_batch.len() >= batch_size {
                let min_timestamp = current_batch.iter().map(|c| c.timestamp).min();
                let max_timestamp = current_batch.iter().map(|c| c.timestamp).max();

                batches.push(ChangeBatch {
                    batch_id: Uuid::new_v4().to_string(),
                    source_id: current_batch[0].source_record_id.clone(),
                    changes: current_batch.clone(),
                    sequence,
                    min_timestamp,
                    max_timestamp,
                });

                current_batch.clear();
                sequence += 1;
            }
        }

        // Handle remaining changes
        if !current_batch.is_empty() {
            let min_timestamp = current_batch.iter().map(|c| c.timestamp).min();
            let max_timestamp = current_batch.iter().map(|c| c.timestamp).max();

            batches.push(ChangeBatch {
                batch_id: Uuid::new_v4().to_string(),
                source_id: current_batch[0].source_record_id.clone(),
                changes: current_batch,
                sequence,
                min_timestamp,
                max_timestamp,
            });
        }

        Ok(batches)
    }

    /// Update detection state after processing changes
    async fn update_detection_state(&self, source: &str, batches: &[ChangeBatch]) -> Result<()> {
        let mut state = self.state_tracker.write().await;

        // Update last processed timestamp
        if let Some(latest_timestamp) = batches.iter()
            .filter_map(|b| b.max_timestamp)
            .max() {
            state.last_timestamps.insert(source.to_string(), latest_timestamp);
        }

        // Update version tracking
        for batch in batches {
            for change in &batch.changes {
                if let Some(version) = change.new_values.get("version")
                    .and_then(super::DataValue::as_string) {
                    let key = format!("{}:{}", source, change.source_record_id);
                    state.last_versions.insert(key, version);
                }

                // Log change entry
                state.change_log.insert(change.timestamp, change.clone());
            }
        }

        // Cleanup old entries (keep last 1000)
        while state.change_log.len() > 1000 {
            if let Some(oldest_key) = state.change_log.keys().next().copied() {
                state.change_log.remove(&oldest_key);
            }
        }

        Ok(())
    }

    // CDC source reading methods (simplified implementations)
    async fn read_database_log(
        &self,
        _db_type: &DatabaseType,
        _config: &LogSourceConfig,
    ) -> Result<Vec<ChangeEntry>> {
        // Simulate reading from database transaction log
        Ok(vec![])
    }

    async fn read_kafka_changelog(
        &self,
        _topic: &str,
        _config: &LogSourceConfig,
    ) -> Result<Vec<ChangeEntry>> {
        // Simulate reading from Kafka changelog topic
        Ok(vec![])
    }

    async fn read_file_changelog(
        &self,
        _pattern: &str,
        _config: &LogSourceConfig,
    ) -> Result<Vec<ChangeEntry>> {
        // Simulate reading from file-based changelog
        Ok(vec![])
    }
}

impl CheckpointManager {
    #[must_use] 
    pub fn new(config: CheckpointConfig, state_manager: Arc<StateManager>) -> Self {
        Self {
            config,
            state_manager,
            active_checkpoints: Arc::new(RwLock::new(HashMap::new())),
        }
    }
    
    pub async fn save_checkpoint(&self, _checkpoint: &Checkpoint) -> Result<()> {
        // Implementation would save checkpoint to persistent storage
        Ok(())
    }
    
    pub async fn load_checkpoint(&self, _checkpoint_id: &str) -> Result<Checkpoint> {
        // Implementation would load checkpoint from persistent storage
        Err(EtlError::Other("Checkpoint not found".to_string()))
    }
}

impl Deduplicator {
    pub async fn new(strategy: DeduplicationStrategy) -> Result<Self> {
        let bloom_filter = match &strategy {
            DeduplicationStrategy::BloomFilter { expected_elements, false_positive_rate } => {
                Some(BloomFilter::new(*expected_elements, *false_positive_rate))
            },
            _ => None,
        };

        Ok(Self {
            strategy,
            cache: Arc::new(RwLock::new(DeduplicationCache {
                hash_cache: HashMap::new(),
                key_cache: HashMap::new(),
                bloom_filter,
            })),
        })
    }

    pub async fn should_process(&self, change: &ChangeEntry) -> Result<bool> {
        match &self.strategy {
            DeduplicationStrategy::Hash { hash_columns, hash_algorithm } => {
                self.check_hash_deduplication(change, hash_columns, hash_algorithm).await
            },
            DeduplicationStrategy::Key { key_columns } => {
                self.check_key_deduplication(change, key_columns).await
            },
            DeduplicationStrategy::BloomFilter { .. } => {
                self.check_bloom_filter_deduplication(change).await
            },
            DeduplicationStrategy::None => Ok(true),
        }
    }

    /// Check hash-based deduplication
    async fn check_hash_deduplication(
        &self,
        change: &ChangeEntry,
        hash_columns: &[String],
        hash_algorithm: &HashAlgorithm,
    ) -> Result<bool> {
        let hash_value = self.calculate_change_hash(change, hash_columns, hash_algorithm);
        let mut cache = self.cache.write().await;

        let identifier = format!("{}:{}", change.source_record_id, hash_value);
        let current_time = Utc::now();

        if let Some(entry) = cache.hash_cache.get_mut(&identifier) {
            // Found duplicate
            entry.last_seen = current_time;
            entry.count += 1;
            Ok(false) // Don't process duplicate
        } else {
            // New entry
            cache.hash_cache.insert(identifier, CacheEntry {
                identifier: hash_value,
                first_seen: current_time,
                last_seen: current_time,
                count: 1,
            });
            Ok(true) // Process new entry
        }
    }

    /// Check key-based deduplication
    async fn check_key_deduplication(
        &self,
        change: &ChangeEntry,
        key_columns: &[String],
    ) -> Result<bool> {
        let key_value = self.extract_key_value(change, key_columns);
        let mut cache = self.cache.write().await;

        let current_time = Utc::now();

        if let Some(entry) = cache.key_cache.get_mut(&key_value) {
            // Check if this is truly a duplicate or an update
            // For updates, we should process if the content has changed
            if let ChangeType::Update = change.change_type {
                entry.last_seen = current_time;
                entry.count += 1;
                Ok(true) // Process updates
            } else {
                entry.last_seen = current_time;
                entry.count += 1;
                Ok(false) // Don't process duplicates
            }
        } else {
            // New entry
            cache.key_cache.insert(key_value.clone(), CacheEntry {
                identifier: key_value,
                first_seen: current_time,
                last_seen: current_time,
                count: 1,
            });
            Ok(true) // Process new entry
        }
    }

    /// Check bloom filter-based deduplication
    async fn check_bloom_filter_deduplication(&self, change: &ChangeEntry) -> Result<bool> {
        let mut cache = self.cache.write().await;

        if let Some(ref mut bloom_filter) = cache.bloom_filter {
            let identifier = format!("{}:{}", change.source_record_id, change.timestamp.timestamp());

            if bloom_filter.contains(&identifier) {
                // Possibly seen before (false positives possible)
                // For critical applications, combine with exact cache
                Ok(false)
            } else {
                // Definitely not seen before
                bloom_filter.insert(&identifier);
                Ok(true)
            }
        } else {
            // No bloom filter configured
            Ok(true)
        }
    }

    /// Calculate hash for change entry
    fn calculate_change_hash(
        &self,
        change: &ChangeEntry,
        hash_columns: &[String],
        algorithm: &HashAlgorithm,
    ) -> String {
        use sha2::{Sha256, Digest};

        // Create deterministic representation of the change
        let mut values = Vec::new();

        // Include change metadata
        values.push(change.source_record_id.clone());
        values.push(change.change_type.to_string());

        // Include specified columns
        for column in hash_columns {
            if let Some(value) = change.new_values.get(column) {
                values.push(serde_json::to_string(value).unwrap_or_default());
            }
        }

        let combined = values.join("|");

        match algorithm {
            HashAlgorithm::Sha256 => {
                let mut hasher = Sha256::new();
                hasher.update(combined.as_bytes());
                format!("{:x}", hasher.finalize())
            },
            HashAlgorithm::Md5 => {
                // Simplified MD5 implementation
                format!("md5_{:x}", self.simple_hash(&combined))
            },
            HashAlgorithm::Sha512 => {
                // Simplified SHA-512 implementation
                format!("sha512_{:x}", self.simple_hash(&combined))
            },
            HashAlgorithm::Crc32 => {
                // Simplified CRC32 implementation
                format!("crc32_{:x}", self.simple_hash(&combined))
            },
        }
    }

    /// Extract key value from change entry
    fn extract_key_value(&self, change: &ChangeEntry, key_columns: &[String]) -> String {
        let mut key_parts = Vec::new();

        for column in key_columns {
            if let Some(value) = change.new_values.get(column) {
                key_parts.push(serde_json::to_string(value).unwrap_or_default());
            } else {
                key_parts.push("NULL".to_string());
            }
        }

        key_parts.join(":")
    }

    /// Simple hash function for fallback implementations
    fn simple_hash(&self, input: &str) -> u64 {
        use std::collections::hash_map::DefaultHasher;
        use std::hash::{Hash, Hasher};

        let mut hasher = DefaultHasher::new();
        input.hash(&mut hasher);
        hasher.finish()
    }

    /// Clean up old cache entries to prevent memory leaks
    pub async fn cleanup_cache(&self, retention_period: Duration) -> Result<()> {
        let mut cache = self.cache.write().await;
        let cutoff_time = Utc::now() - retention_period;

        // Clean hash cache
        cache.hash_cache.retain(|_, entry| entry.last_seen > cutoff_time);

        // Clean key cache
        cache.key_cache.retain(|_, entry| entry.last_seen > cutoff_time);

        Ok(())
    }

    /// Get deduplication statistics
    pub async fn get_statistics(&self) -> DeduplicationStatistics {
        let cache = self.cache.read().await;

        let hash_entries = cache.hash_cache.len();
        let key_entries = cache.key_cache.len();
        let total_hash_hits = cache.hash_cache.values().map(|e| e.count).sum::<u64>();
        let total_key_hits = cache.key_cache.values().map(|e| e.count).sum::<u64>();

        DeduplicationStatistics {
            hash_cache_entries: hash_entries,
            key_cache_entries: key_entries,
            total_hash_duplicates: total_hash_hits,
            total_key_duplicates: total_key_hits,
            bloom_filter_entries: cache.bloom_filter.as_ref()
                .map_or(0, |bf| bf.current_count),
        }
    }
}

/// Statistics for deduplication operations
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DeduplicationStatistics {
    /// Number of entries in hash cache
    pub hash_cache_entries: usize,
    /// Number of entries in key cache
    pub key_cache_entries: usize,
    /// Total duplicate hits in hash cache
    pub total_hash_duplicates: u64,
    /// Total duplicate hits in key cache
    pub total_key_duplicates: u64,
    /// Number of entries in bloom filter
    pub bloom_filter_entries: usize,
}

impl ChangeType {
    fn to_string(&self) -> String {
        match self {
            Self::Insert => "INSERT".to_string(),
            Self::Update => "UPDATE".to_string(),
            Self::Delete => "DELETE".to_string(),
            Self::Upsert => "UPSERT".to_string(),
        }
    }
}

impl BloomFilter {
    /// Create a new bloom filter
    #[must_use] 
    pub fn new(expected_elements: usize, false_positive_rate: f64) -> Self {
        let bit_array_size = Self::calculate_bit_array_size(expected_elements, false_positive_rate);
        let hash_functions = Self::calculate_hash_functions(bit_array_size, expected_elements);

        Self {
            bits: vec![false; bit_array_size],
            hash_functions,
            expected_elements,
            current_count: 0,
        }
    }

    /// Calculate optimal bit array size
    fn calculate_bit_array_size(expected_elements: usize, false_positive_rate: f64) -> usize {
        let m = -(expected_elements as f64 * false_positive_rate.ln()) / (2.0_f64.ln().powi(2));
        m.ceil() as usize
    }

    /// Calculate optimal number of hash functions
    fn calculate_hash_functions(bit_array_size: usize, expected_elements: usize) -> usize {
        let k = (bit_array_size as f64 / expected_elements as f64) * 2.0_f64.ln();
        (k.ceil() as usize).max(1)
    }

    /// Insert an element into the bloom filter
    pub fn insert(&mut self, element: &str) {
        let hashes = self.hash_element(element);

        for &hash_value in &hashes {
            let index = hash_value % self.bits.len();
            self.bits[index] = true;
        }

        self.current_count += 1;
    }

    /// Check if an element might be in the filter
    #[must_use] 
    pub fn contains(&self, element: &str) -> bool {
        let hashes = self.hash_element(element);

        for &hash_value in &hashes {
            let index = hash_value % self.bits.len();
            if !self.bits[index] {
                return false; // Definitely not in set
            }
        }

        true // Might be in set (or false positive)
    }

    /// Generate multiple hash values for an element
    fn hash_element(&self, element: &str) -> Vec<usize> {
        use std::collections::hash_map::DefaultHasher;
        use std::hash::{Hash, Hasher};

        let mut hashes = Vec::with_capacity(self.hash_functions);

        // Use multiple hash functions based on a single hash with different salts
        let mut hasher = DefaultHasher::new();
        element.hash(&mut hasher);
        let primary_hash = hasher.finish();

        for i in 0..self.hash_functions {
            let hash = primary_hash.wrapping_add(i as u64 * 0x9E3779B9);
            hashes.push(hash as usize);
        }

        hashes
    }

    /// Get current false positive probability
    #[must_use] 
    pub fn current_false_positive_rate(&self) -> f64 {
        if self.current_count == 0 {
            return 0.0;
        }

        let filled_bits = self.bits.iter().filter(|&&bit| bit).count();
        let probability = filled_bits as f64 / self.bits.len() as f64;
        probability.powi(self.hash_functions as i32)
    }

    /// Clear the bloom filter
    pub fn clear(&mut self) {
        self.bits.fill(false);
        self.current_count = 0;
    }
}

impl StateTracker {
    #[must_use] 
    pub fn new() -> Self {
        Self {
            source_states: HashMap::new(),
            global_stats: ProcessingStats {
                total_records: 0,
                total_bytes: 0,
                start_time: Utc::now(),
                last_processing_time: None,
                processing_rate: 0.0,
                throughput: 0.0,
            },
            error_tracker: ErrorTracker {
                error_history: VecDeque::new(),
                error_counts: HashMap::new(),
                last_error_time: None,
            },
        }
    }
}

impl WatermarkManager {
    #[must_use] 
    pub fn new() -> Self {
        Self {
            source_watermarks: Arc::new(RwLock::new(HashMap::new())),
            global_watermark: Arc::new(RwLock::new(None)),
            listeners: Arc::new(Mutex::new(Vec::new())),
        }
    }
    
    pub async fn update_watermark(&self, source_id: &str, watermark: DateTime<Utc>) -> Result<()> {
        let mut watermarks = self.source_watermarks.write().await;
        watermarks.insert(source_id.to_string(), watermark);
        Ok(())
    }
    
    pub async fn get_all_watermarks(&self) -> HashMap<String, DateTime<Utc>> {
        self.source_watermarks.read().await.clone()
    }
}

impl MergeProcessor {
    #[must_use] 
    pub fn new() -> Self {
        Self {
            strategies: HashMap::new(),
            conflict_rules: Vec::new(),
        }
    }
    
    pub async fn merge(
        &self,
        _target: &str,
        _changes: ProcessedChanges,
        strategy: MergeStrategy,
    ) -> Result<MergeResult> {
        // Simplified implementation - would contain actual merge logic
        Ok(MergeResult {
            target: _target.to_string(),
            strategy,
            inserted_count: 0,
            updated_count: 0,
            deleted_count: 0,
            conflicts_resolved: 0,
            duration_ms: 0,
            errors: Vec::new(),
        })
    }
}

impl Default for StateTracker {
    fn default() -> Self {
        Self::new()
    }
}

impl Default for WatermarkManager {
    fn default() -> Self {
        Self::new()
    }
}

impl Default for MergeProcessor {
    fn default() -> Self {
        Self::new()
    }
}