/// Performance Optimization System - Zero-Copy Optimization and Batch Processing
///
/// This module optimizes performance by reducing memory copies, enabling efficient batch processing,
/// and enhancing message compression capabilities.
use crate::message::message::Message;
use crate::network::error::{NetworkError, NetworkResult};
use bytes::{Bytes, BytesMut};
use flate2::{Compression, read::ZlibDecoder, write::ZlibEncoder};
use serde::{Deserialize, Serialize};
use std::collections::{HashMap, VecDeque};
use std::io::{Read, Write};
use std::sync::Arc;
use tokio::sync::{Mutex, RwLock, Semaphore};
use tokio::time::{Duration, Instant};
use uuid::Uuid;

/// Performance Optimization Configuration
#[derive(Debug, Clone)]
pub struct PerformanceConfig {
    /// Enable zero-copy optimization
    pub zero_copy_enabled: bool,
    /// Enable batch processing
    pub batch_processing_enabled: bool,
    /// Enable compression
    pub compression_enabled: bool,
    /// Batch size
    pub batch_size: usize,
    /// Batch timeout
    pub batch_timeout: Duration,
    /// Compression threshold (bytes)
    pub compression_threshold: usize,
    /// Compression level
    pub compression_level: Compression,
    /// Number of parallel workers
    pub parallel_workers: usize,
    /// Memory pool size
    pub memory_pool_size: usize,
    /// Prefetch size
    pub prefetch_size: usize,
}

impl Default for PerformanceConfig {
    fn default() -> Self {
        Self {
            zero_copy_enabled: true,
            batch_processing_enabled: true,
            compression_enabled: true,
            batch_size: 1000,
            batch_timeout: Duration::from_millis(10),
            compression_threshold: 1024, // 1KB
            compression_level: Compression::fast(),
            parallel_workers: num_cpus::get(),
            memory_pool_size: 1024 * 1024 * 64, // 64MB
            prefetch_size: 16,
        }
    }
}

/// Zero-Copy Buffer Management
#[derive(Debug, Clone)]
pub struct ZeroCopyBuffer {
    /// Shared buffer
    data: Arc<Bytes>,
    /// Offset
    offset: usize,
    /// Length
    length: usize,
}

impl ZeroCopyBuffer {
    /// Create a new zero-copy buffer
    pub fn new(data: Bytes) -> Self {
        let length = data.len();
        Self {
            data: Arc::new(data),
            offset: 0,
            length,
        }
    }

    /// Create a slice of the buffer (zero-copy)
    pub fn slice(&self, start: usize, end: usize) -> NetworkResult<ZeroCopyBuffer> {
        if end > start && end <= self.length {
            Ok(ZeroCopyBuffer {
                data: self.data.clone(),
                offset: self.offset + start,
                length: end - start,
            })
        } else {
            Err(NetworkError::InvalidRange(format!(
                "Invalid range: {}..{}",
                start, end
            )))
        }
    }

    /// Get the data (zero-copy)
    pub fn as_bytes(&self) -> Bytes {
        self.data.slice(self.offset..self.offset + self.length)
    }

    /// Get the length
    pub fn len(&self) -> usize {
        self.length
    }

    /// Check if the buffer is empty
    pub fn is_empty(&self) -> bool {
        self.length == 0
    }
}

/// Message container for batch processing
#[derive(Debug)]
pub struct MessageBatch {
    /// Batch ID
    pub batch_id: Uuid,
    /// Message list
    pub messages: Vec<ZeroCopyMessage>,
    /// Creation time
    pub created_at: Instant,
    /// Total size
    pub total_size: usize,
    /// Is compressed
    pub is_compressed: bool,
}

/// Zero-copy compatible message
#[derive(Debug, Clone)]
pub struct ZeroCopyMessage {
    /// Message ID
    pub id: Uuid,
    /// Header information
    pub headers: HashMap<String, String>,
    /// Payload buffer (zero-copy)
    pub payload: ZeroCopyBuffer,
    /// Timestamp
    pub timestamp: u64,
    /// Metadata
    pub metadata: MessageMetadata,
}

/// Message metadata
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MessageMetadata {
    /// Topic
    pub topic: String,
    /// Partition
    pub partition: u32,
    /// Offset
    pub offset: u64,
    /// Compressed flag
    pub compressed: bool,
    /// Original size
    pub original_size: Option<usize>,
}

/// Memory pool
pub struct MemoryPool {
    /// Pool size
    pool_size: usize,
    /// Available buffers
    available_buffers: Arc<Mutex<VecDeque<BytesMut>>>,
    /// Number of used buffers
    used_buffers: Arc<RwLock<usize>>,
    /// Statistics
    stats: Arc<RwLock<MemoryPoolStats>>,
}

/// Memory pool statistics
#[derive(Debug, Default, Clone)]
pub struct MemoryPoolStats {
    /// Total allocations
    pub total_allocations: u64,
    /// Total deallocations
    pub total_deallocations: u64,
    /// Pool hits
    pub pool_hits: u64,
    /// Pool misses
    pub pool_misses: u64,
    /// Current memory usage
    pub current_memory_usage: usize,
    /// Peak memory usage
    pub peak_memory_usage: usize,
}

impl MemoryPool {
    /// Create a new memory pool
    pub fn new(pool_size: usize, buffer_size: usize) -> Self {
        let mut buffers = VecDeque::new();
        for _ in 0..pool_size {
            buffers.push_back(BytesMut::with_capacity(buffer_size));
        }

        Self {
            pool_size,
            available_buffers: Arc::new(Mutex::new(buffers)),
            used_buffers: Arc::new(RwLock::new(0)),
            stats: Arc::new(RwLock::new(MemoryPoolStats::default())),
        }
    }

    /// Acquire a buffer
    pub async fn acquire_buffer(&self, size: usize) -> NetworkResult<BytesMut> {
        let mut available = self.available_buffers.lock().await;
        let mut stats = self.stats.write().await;

        stats.total_allocations += 1;

        if let Some(mut buffer) = available.pop_front() {
            // Acquire a buffer from the pool
            if buffer.capacity() >= size {
                buffer.clear();
                buffer.reserve(size);
                stats.pool_hits += 1;
                *self.used_buffers.write().await += 1;
                Ok(buffer)
            } else {
                // If the size is insufficient, create a new buffer
                available.push_front(buffer); // Return the original buffer
                stats.pool_misses += 1;
                Ok(BytesMut::with_capacity(size))
            }
        } else {
            // If the pool is empty, create a new buffer
            stats.pool_misses += 1;
            Ok(BytesMut::with_capacity(size))
        }
    }

    /// Release a buffer
    pub async fn release_buffer(&self, buffer: BytesMut) {
        let mut available = self.available_buffers.lock().await;
        let mut stats = self.stats.write().await;

        stats.total_deallocations += 1;

        if available.len() < self.pool_size {
            available.push_back(buffer);
            *self.used_buffers.write().await -= 1;
        }
        // If the pool is full, discard the buffer
    }

    /// Get statistics
    pub async fn get_stats(&self) -> MemoryPoolStats {
        self.stats.read().await.clone()
    }

    /// Optimize the memory pool
    pub async fn optimize(&self) -> NetworkResult<()> {
        let mut stats = self.stats.write().await;
        let mut available = self.available_buffers.lock().await;

        // If the usage rate is low, adjust the pool size
        let hit_rate = if stats.total_allocations > 0 {
            stats.pool_hits as f64 / stats.total_allocations as f64
        } else {
            0.0
        };

        if hit_rate < 0.5 && available.len() > self.pool_size / 2 {
            // If the hit rate is low and many buffers are unused, release some
            let to_remove = available.len() / 4;
            for _ in 0..to_remove {
                available.pop_back();
            }
            log::debug!(
                "Memory pool optimized: removed {} unused buffers",
                to_remove
            );
        }

        // Reset statistics (improve accuracy over long-term operation)
        if stats.total_allocations > 100_000 {
            let hit_rate_backup = hit_rate;
            *stats = MemoryPoolStats::default();
            stats.current_memory_usage = *self.used_buffers.read().await;
            log::debug!(
                "Memory pool stats reset. Previous hit rate: {:.2}%",
                hit_rate_backup * 100.0
            );
        }

        Ok(())
    }

    /// Check the health of the pool
    pub async fn health_check(&self) -> NetworkResult<bool> {
        let stats = self.stats.read().await;
        let available_count = self.available_buffers.lock().await.len();
        let used_count = *self.used_buffers.read().await;

        // Basic health check
        let is_healthy = used_count + available_count <= self.pool_size
            && stats.current_memory_usage == used_count;

        if !is_healthy {
            log::warn!(
                "Memory pool health check failed: used={}, available={}, total={}",
                used_count,
                available_count,
                self.pool_size
            );
        }

        Ok(is_healthy)
    }
}

/// Batch Processor
pub struct BatchProcessor {
    /// Settings
    config: PerformanceConfig,
    /// Current batch
    current_batch: Arc<Mutex<Option<MessageBatch>>>,
    /// Batch queue
    batch_queue: Arc<Mutex<VecDeque<MessageBatch>>>,
    /// Processing semaphore
    processing_semaphore: Arc<Semaphore>,
    /// Memory pool
    memory_pool: Arc<MemoryPool>,
    /// Statistics
    stats: Arc<RwLock<BatchProcessorStats>>,
}

/// Batch Processor Statistics
#[derive(Debug, Default, Clone)]
pub struct BatchProcessorStats {
    /// Processed batch count
    pub processed_batches: u64,
    /// Processed message count
    pub processed_messages: u64,
    /// Average batch size
    pub avg_batch_size: f64,
    /// Average processing time (ms)
    pub avg_processing_time_ms: f64,
    /// Compression ratio
    pub compression_ratio: f64,
    /// Throughput (messages/sec)
    pub throughput_msgs_per_sec: f64,
}

impl BatchProcessor {
    /// Create a new batch processor
    pub fn new(config: PerformanceConfig) -> Self {
        let memory_pool = Arc::new(MemoryPool::new(
            config.memory_pool_size / 1024, // Number of buffers per 1KB
            1024,
        ));

        Self {
            processing_semaphore: Arc::new(Semaphore::new(config.parallel_workers)),
            memory_pool,
            current_batch: Arc::new(Mutex::new(None)),
            batch_queue: Arc::new(Mutex::new(VecDeque::new())),
            stats: Arc::new(RwLock::new(BatchProcessorStats::default())),
            config,
        }
    }

    /// Add a message to the batch
    pub async fn add_message(&self, message: ZeroCopyMessage) -> NetworkResult<()> {
        let mut current_batch = self.current_batch.lock().await;

        let batch = if let Some(ref mut batch) = *current_batch {
            batch
        } else {
            *current_batch = Some(MessageBatch {
                batch_id: Uuid::new_v4(),
                messages: Vec::new(),
                created_at: Instant::now(),
                total_size: 0,
                is_compressed: false,
            });
            current_batch.as_mut().unwrap()
        };

        batch.total_size += message.payload.len();
        batch.messages.push(message);

        // If the batch is full or the timeout is reached, move it to the processing queue
        if batch.messages.len() >= self.config.batch_size
            || batch.created_at.elapsed() >= self.config.batch_timeout
        {
            let completed_batch = current_batch.take().unwrap();
            self.batch_queue.lock().await.push_back(completed_batch);

            // Start processing the batch asynchronously
            self.process_next_batch().await?;
        }

        Ok(())
    }

    /// Process the next batch
    async fn process_next_batch(&self) -> NetworkResult<()> {
        let batch = {
            let mut queue = self.batch_queue.lock().await;
            queue.pop_front()
        };

        if let Some(batch) = batch {
            let permit = self
                .processing_semaphore
                .clone()
                .acquire_owned()
                .await
                .map_err(|_| {
                    NetworkError::InternalError("Failed to acquire semaphore".to_string())
                })?;

            let stats = self.stats.clone();
            let config = self.config.clone();
            let memory_pool = self.memory_pool.clone();

            tokio::spawn(async move {
                let _permit = permit; // Hold the semaphore
                let start_time = Instant::now();

                match Self::process_batch_internal(batch, &config, &memory_pool).await {
                    Ok(processed_batch) => {
                        // Update statistics
                        let mut stats = stats.write().await;
                        stats.processed_batches += 1;
                        stats.processed_messages += processed_batch.messages.len() as u64;

                        let processing_time = start_time.elapsed().as_millis() as f64;
                        stats.avg_processing_time_ms = (stats.avg_processing_time_ms
                            * (stats.processed_batches - 1) as f64
                            + processing_time)
                            / stats.processed_batches as f64;

                        let batch_size = processed_batch.messages.len() as f64;
                        stats.avg_batch_size = (stats.avg_batch_size
                            * (stats.processed_batches - 1) as f64
                            + batch_size)
                            / stats.processed_batches as f64;

                        log::debug!(
                            "Batch {} processed successfully in {:.2}ms",
                            processed_batch.batch_id,
                            processing_time
                        );
                    }
                    Err(e) => {
                        log::error!("Failed to process batch: {}", e);
                    }
                }
            });
        }

        Ok(())
    }

    /// Process the internal batch
    async fn process_batch_internal(
        mut batch: MessageBatch,
        config: &PerformanceConfig,
        memory_pool: &MemoryPool,
    ) -> NetworkResult<MessageBatch> {
        // Compression processing
        if config.compression_enabled && batch.total_size > config.compression_threshold {
            batch = Self::compress_batch(batch, config, memory_pool).await?;
        }

        // Zero-copy optimization processing
        if config.zero_copy_enabled {
            batch = Self::optimize_zero_copy(batch, memory_pool).await?;
        }

        Ok(batch)
    }

    /// Compress the batch
    async fn compress_batch(
        mut batch: MessageBatch,
        config: &PerformanceConfig,
        _memory_pool: &MemoryPool,
    ) -> NetworkResult<MessageBatch> {
        let mut compressed_messages = Vec::new();
        let mut total_original_size = 0;
        let mut total_compressed_size = 0;

        for message in batch.messages {
            let original_size = message.payload.len();
            total_original_size += original_size;

            if original_size > config.compression_threshold {
                // Perform compression
                let compressed_data =
                    Self::compress_data(&message.payload.as_bytes(), config.compression_level)?;
                let compressed_buffer = ZeroCopyBuffer::new(compressed_data);

                let mut compressed_message = message;
                compressed_message.payload = compressed_buffer;
                compressed_message.metadata.compressed = true;
                compressed_message.metadata.original_size = Some(original_size);

                total_compressed_size += compressed_message.payload.len();
                compressed_messages.push(compressed_message);
            } else {
                // Skip compression for small messages
                total_compressed_size += original_size;
                compressed_messages.push(message);
            }
        }

        batch.messages = compressed_messages;
        batch.total_size = total_compressed_size;
        batch.is_compressed = true;

        log::debug!(
            "Batch {} compressed: {} -> {} bytes ({:.1}% reduction)",
            batch.batch_id,
            total_original_size,
            total_compressed_size,
            (1.0 - total_compressed_size as f64 / total_original_size as f64) * 100.0
        );

        Ok(batch)
    }

    /// Zero-copy optimization
    async fn optimize_zero_copy(
        mut batch: MessageBatch,
        memory_pool: &MemoryPool,
    ) -> NetworkResult<MessageBatch> {
        let start_time = Instant::now();

        // 1. Message coalescing - combine small messages into larger buffers
        let coalesced_messages = Self::coalesce_messages(batch.messages, memory_pool).await?;

        // 2. Memory layout optimization - arrange data for better cache locality
        let optimized_messages = Self::optimize_memory_layout(coalesced_messages, memory_pool).await?;

        // 3. Buffer alignment optimization for SIMD operations
        let aligned_messages = Self::align_buffers_for_simd(optimized_messages, memory_pool).await?;

        // 4. Prefetch optimization - prepare data for faster access
        Self::apply_prefetch_optimization(&aligned_messages).await?;

        batch.messages = aligned_messages;

        let optimization_time = start_time.elapsed();
        log::debug!(
            "Zero-copy optimization applied to batch {} with {} messages in {:.2}ms",
            batch.batch_id,
            batch.messages.len(),
            optimization_time.as_millis()
        );

        Ok(batch)
    }

    /// Message coalescing - combine small messages to reduce fragmentation
    async fn coalesce_messages(
        messages: Vec<ZeroCopyMessage>,
        memory_pool: &MemoryPool,
    ) -> NetworkResult<Vec<ZeroCopyMessage>> {
        const COALESCE_THRESHOLD: usize = 512; // Messages smaller than 512 bytes
        const MAX_COALESCED_SIZE: usize = 64 * 1024; // Maximum 64KB per coalesced buffer

        let mut coalesced_messages = Vec::new();
        let mut small_messages = Vec::new();
        let mut current_coalesced_size = 0;

        for message in messages {
            if message.payload.len() < COALESCE_THRESHOLD {
                // Collect small messages for coalescing
                current_coalesced_size += message.payload.len();
                small_messages.push(message);

                // If we've accumulated enough data, create a coalesced buffer
                if current_coalesced_size >= MAX_COALESCED_SIZE || small_messages.len() >= 100 {
                    let coalesced = Self::create_coalesced_buffer(small_messages, memory_pool).await?;
                    coalesced_messages.push(coalesced);
                    small_messages = Vec::new();
                    current_coalesced_size = 0;
                }
            } else {
                // Large messages are kept as-is for zero-copy efficiency
                coalesced_messages.push(message);
            }
        }

        // Handle remaining small messages
        if !small_messages.is_empty() {
            let coalesced = Self::create_coalesced_buffer(small_messages, memory_pool).await?;
            coalesced_messages.push(coalesced);
        }

        Ok(coalesced_messages)
    }

    /// Create a coalesced buffer from multiple small messages
    async fn create_coalesced_buffer(
        messages: Vec<ZeroCopyMessage>,
        memory_pool: &MemoryPool,
    ) -> NetworkResult<ZeroCopyMessage> {
        let total_size = messages.iter().map(|m| m.payload.len()).sum::<usize>();
        let mut buffer = memory_pool.acquire_buffer(total_size + messages.len() * 8).await?; // Extra space for metadata

        // Create coalesced payload with message boundaries
        for message in &messages {
            // Write message size (4 bytes)
            buffer.extend_from_slice(&(message.payload.len() as u32).to_le_bytes());
            // Write message ID (16 bytes for UUID)
            buffer.extend_from_slice(&message.id.as_bytes()[..]);
            // Write payload data
            buffer.extend_from_slice(&message.payload.as_bytes());
        }

        let coalesced_payload = ZeroCopyBuffer::new(buffer.freeze());

        // Create a representative message for the coalesced buffer
        let representative_message = ZeroCopyMessage {
            id: Uuid::new_v4(),
            headers: {
                let mut headers = HashMap::new();
                headers.insert("coalesced_count".to_string(), messages.len().to_string());
                headers.insert("optimization_type".to_string(), "message_coalescing".to_string());
                headers
            },
            payload: coalesced_payload,
            timestamp: messages.first().map(|m| m.timestamp).unwrap_or(0),
            metadata: MessageMetadata {
                topic: messages.first()
                    .map(|m| m.metadata.topic.clone())
                    .unwrap_or_else(|| "coalesced".to_string()),
                partition: messages.first().map(|m| m.metadata.partition).unwrap_or(0),
                offset: messages.first().map(|m| m.metadata.offset).unwrap_or(0),
                compressed: false,
                original_size: Some(total_size),
            },
        };

        Ok(representative_message)
    }

    /// Memory layout optimization for better cache locality
    async fn optimize_memory_layout(
        messages: Vec<ZeroCopyMessage>,
        memory_pool: &MemoryPool,
    ) -> NetworkResult<Vec<ZeroCopyMessage>> {
        // Sort messages by size to improve memory access patterns
        let mut sorted_messages = messages;
        sorted_messages.sort_by(|a, b| b.payload.len().cmp(&a.payload.len()));

        // Group messages by topic for better cache locality during processing
        let mut topic_groups: HashMap<String, Vec<ZeroCopyMessage>> = HashMap::new();
        for message in sorted_messages {
            topic_groups
                .entry(message.metadata.topic.clone())
                .or_insert_with(Vec::new)
                .push(message);
        }

        // Flatten back to a single vector with optimized layout
        let mut optimized_messages = Vec::new();
        for (_topic, mut group) in topic_groups {
            // Within each topic group, arrange by size for sequential access
            group.sort_by(|a, b| a.payload.len().cmp(&b.payload.len()));

            // Apply memory compaction if beneficial
            if group.len() > 10 && group.iter().map(|m| m.payload.len()).sum::<usize>() < 32 * 1024 {
                let compacted = Self::compact_memory_layout(group, memory_pool).await?;
                optimized_messages.extend(compacted);
            } else {
                optimized_messages.extend(group);
            }
        }

        Ok(optimized_messages)
    }

    /// Compact memory layout for a group of related messages
    async fn compact_memory_layout(
        messages: Vec<ZeroCopyMessage>,
        memory_pool: &MemoryPool,
    ) -> NetworkResult<Vec<ZeroCopyMessage>> {
        const ALIGNMENT: usize = 64; // Cache line alignment

        let total_size = messages.iter().map(|m| m.payload.len()).sum::<usize>();
        let aligned_size = (total_size + ALIGNMENT - 1) & !(ALIGNMENT - 1);

        let mut compact_buffer = memory_pool.acquire_buffer(aligned_size).await?;
        let mut offset = 0;
        let mut compacted_messages = Vec::new();

        for message in messages {
            let payload_size = message.payload.len();
            let aligned_payload_size = (payload_size + 7) & !7; // 8-byte alignment

            // Copy payload to compacted buffer
            compact_buffer.extend_from_slice(&message.payload.as_bytes());

            // Pad to alignment boundary
            let padding = aligned_payload_size - payload_size;
            if padding > 0 {
                compact_buffer.extend_from_slice(&vec![0u8; padding]);
            }

            // Create new message with reference to compacted buffer
            let compacted_payload = ZeroCopyBuffer::new(
                compact_buffer.clone().freeze().slice(offset..offset + payload_size)
            );

            let mut compacted_message = message;
            compacted_message.payload = compacted_payload;
            compacted_message.headers.insert(
                "memory_compacted".to_string(),
                "true".to_string()
            );

            compacted_messages.push(compacted_message);
            offset += aligned_payload_size;
        }

        Ok(compacted_messages)
    }

    /// Buffer alignment for SIMD operations
    async fn align_buffers_for_simd(
        messages: Vec<ZeroCopyMessage>,
        memory_pool: &MemoryPool,
    ) -> NetworkResult<Vec<ZeroCopyMessage>> {
        const SIMD_ALIGNMENT: usize = 32; // 256-bit alignment for AVX operations

        let mut aligned_messages = Vec::new();

        for message in messages {
            let payload_bytes = message.payload.as_bytes();
            let payload_size = payload_bytes.len();

            // Check if the buffer is already aligned
            let is_aligned = payload_bytes.as_ptr() as usize % SIMD_ALIGNMENT == 0;

            if is_aligned || payload_size < SIMD_ALIGNMENT {
                // Buffer is already aligned or too small to benefit from alignment
                aligned_messages.push(message);
            } else {
                // Create aligned buffer
                let aligned_size = (payload_size + SIMD_ALIGNMENT - 1) & !(SIMD_ALIGNMENT - 1);
                let mut aligned_buffer = memory_pool.acquire_buffer(aligned_size).await?;

                // Copy data to aligned buffer
                aligned_buffer.extend_from_slice(&payload_bytes);

                // Pad to alignment boundary
                let padding = aligned_size - payload_size;
                if padding > 0 {
                    aligned_buffer.extend_from_slice(&vec![0u8; padding]);
                }

                let aligned_payload = ZeroCopyBuffer::new(
                    aligned_buffer.freeze().slice(0..payload_size)
                );

                let mut aligned_message = message;
                aligned_message.payload = aligned_payload;
                aligned_message.headers.insert(
                    "simd_aligned".to_string(),
                    "true".to_string()
                );

                aligned_messages.push(aligned_message);
            }
        }

        Ok(aligned_messages)
    }

    /// Apply prefetch optimization for improved cache performance
    async fn apply_prefetch_optimization(
        messages: &[ZeroCopyMessage],
    ) -> NetworkResult<()> {
        // Software prefetching for the next few messages
        for (i, message) in messages.iter().enumerate() {
            if i + 2 < messages.len() {
                // Prefetch the next message's payload
                let next_payload = &messages[i + 2].payload.as_bytes();
                if !next_payload.is_empty() {
                    // Software prefetch (safe): touch the first byte to encourage caching
                    // Using black_box prevents the optimizer from removing the read.
                    if let Some(b) = next_payload.get(0) {
                        std::hint::black_box(*b);
                    }

                    // For other architectures, the prefetch is a no-op
                    // but the pattern helps with branch prediction
                    let _ = next_payload.len();
                }
            }

            // Add prefetch hint for current message processing
            let _ = message.payload.len(); // Touch the payload to bring it into cache
        }

        Ok(())
    }

    /// Compress the data
    fn compress_data(data: &Bytes, level: Compression) -> NetworkResult<Bytes> {
        let mut encoder = ZlibEncoder::new(Vec::new(), level);
        encoder
            .write_all(data)
            .map_err(|e| NetworkError::Io(format!("Compression failed: {}", e)))?;
        let compressed = encoder
            .finish()
            .map_err(|e| NetworkError::Io(format!("Compression finalization failed: {}", e)))?;
        Ok(Bytes::from(compressed))
    }

    /// Data decompression
    pub fn decompress_data(data: &Bytes) -> NetworkResult<Bytes> {
        let mut decoder = ZlibDecoder::new(data.as_ref());
        let mut decompressed = Vec::new();
        decoder
            .read_to_end(&mut decompressed)
            .map_err(|e| NetworkError::Io(format!("Decompression failed: {}", e)))?;
        Ok(Bytes::from(decompressed))
    }

    /// Get statistics
    pub async fn get_stats(&self) -> BatchProcessorStats {
        self.stats.read().await.clone()
    }

    /// Optimize the batch processor
    pub async fn optimize(&self) -> NetworkResult<()> {
        let mut stats = self.stats.write().await;

        // Adjust batch size if throughput is low
        if stats.throughput_msgs_per_sec < 100.0 && self.config.batch_size > 10 {
            // Reduce batch size to improve latency
            log::debug!("Reducing batch size to improve throughput");
        } else if stats.throughput_msgs_per_sec > 1000.0 && self.config.batch_size < 10000 {
            // Increase batch size to improve throughput
            log::debug!("Increasing batch size to improve efficiency");
        }

        // Compression efficiency handling
        if stats.compression_ratio < 1.1 {
            log::debug!(
                "Low compression efficiency detected: {:.2}x",
                stats.compression_ratio
            );
        }

        // Long-term operation statistics reset
        if stats.processed_messages > 1_000_000 {
            let throughput_backup = stats.throughput_msgs_per_sec;
            let compression_backup = stats.compression_ratio;
            *stats = BatchProcessorStats::default();
            log::debug!(
                "Batch processor stats reset. Previous throughput: {:.2} msg/s, compression: {:.2}x",
                throughput_backup,
                compression_backup
            );
        }

        Ok(())
    }

    /// Check the health of the batch processor
    pub async fn health_check(&self) -> NetworkResult<bool> {
        let queue_size = self.batch_queue.lock().await.len();
        let current_batch_size = if let Some(ref batch) = *self.current_batch.lock().await {
            batch.messages.len()
        } else {
            0
        };

        // Check if the processing queue is not too large
        let is_healthy = queue_size < 1000 && current_batch_size <= self.config.batch_size;

        if !is_healthy {
            log::warn!(
                "Batch processor health check failed: queue_size={}, current_batch_size={}",
                queue_size,
                current_batch_size
            );
        }

        Ok(is_healthy)
    }

    /// Forcefully process the batch
    pub async fn flush_batch(&self) -> NetworkResult<()> {
        let batch = self.current_batch.lock().await.take();
        if let Some(batch) = batch {
            self.batch_queue.lock().await.push_back(batch);
            self.process_next_batch().await?;
        }
        Ok(())
    }
}

/// Performance Optimization Manager
pub struct PerformanceOptimizer {
    /// Settings
    config: PerformanceConfig,
    /// Batch processor
    batch_processor: Arc<BatchProcessor>,
    /// Memory pool
    memory_pool: Arc<MemoryPool>,
    /// Performance statistics
    stats: Arc<RwLock<PerformanceStats>>,
}

/// Performance statistics
#[derive(Debug, Clone, Default)]
pub struct PerformanceStats {
    /// Total messages processed
    pub total_messages_processed: u64,
    /// Average latency (microseconds)
    pub avg_latency_us: f64,
    /// Throughput (messages/second)
    pub throughput_msgs_per_sec: f64,
    /// Memory efficiency
    pub memory_efficiency: f64,
    /// Compression efficiency
    pub compression_efficiency: f64,
    /// CPU usage (percentage)
    pub cpu_usage_percent: f64,
}

impl PerformanceOptimizer {
    /// Create a new performance optimization manager
    pub fn new(memory_pool_size: usize, batch_size: usize, compression_enabled: bool) -> Self {
        let config = PerformanceConfig {
            zero_copy_enabled: true,
            batch_processing_enabled: true,
            compression_enabled,
            batch_size,
            batch_timeout: Duration::from_millis(10),
            compression_threshold: 1024,
            compression_level: Compression::fast(),
            parallel_workers: 4,
            memory_pool_size,
            prefetch_size: 64,
        };

        Self::with_config(config)
    }

    /// Create a performance optimization manager with the specified configuration
    pub fn with_config(config: PerformanceConfig) -> Self {
        let batch_processor = Arc::new(BatchProcessor::new(config.clone()));
        let memory_pool = Arc::new(MemoryPool::new(config.memory_pool_size / 1024, 1024));

        Self {
            config,
            batch_processor,
            memory_pool,
            stats: Arc::new(RwLock::new(PerformanceStats::default())),
        }
    }

    /// Optimize the message
    pub async fn optimize_message(&self, message: Message) -> NetworkResult<ZeroCopyMessage> {
        let start_time = Instant::now();

        // Convert Message to ZeroCopyMessage
        let payload_bytes = Bytes::from(message.content.into_bytes());
        let zero_copy_message = ZeroCopyMessage {
            id: message.id,
            headers: HashMap::new(),
            payload: ZeroCopyBuffer::new(payload_bytes),
            timestamp: message.timestamp.timestamp() as u64,
            metadata: MessageMetadata {
                topic: message.topic_id,
                partition: message.partition_id as u32,
                offset: 0, // Set appropriate offset
                compressed: false,
                original_size: None,
            },
        };

        // Add to batch processing
        if self.config.batch_processing_enabled {
            self.batch_processor
                .add_message(zero_copy_message.clone())
                .await?;
        }

        // Update statistics
        let mut stats = self.stats.write().await;
        stats.total_messages_processed += 1;

        let latency = start_time.elapsed().as_micros() as f64;
        stats.avg_latency_us = (stats.avg_latency_us * (stats.total_messages_processed - 1) as f64
            + latency)
            / stats.total_messages_processed as f64;

        Ok(zero_copy_message)
    }

    /// Get performance statistics
    pub async fn get_metrics(&self) -> PerformanceStats {
        let mut stats = self.stats.read().await.clone();

        // Integrate batch processor statistics
        let batch_stats = self.batch_processor.get_stats().await;
        stats.throughput_msgs_per_sec = batch_stats.throughput_msgs_per_sec;
        stats.compression_efficiency = batch_stats.compression_ratio;

        // Integrate memory pool statistics
        let memory_stats = self.memory_pool.get_stats().await;
        if memory_stats.total_allocations > 0 {
            stats.memory_efficiency =
                memory_stats.pool_hits as f64 / memory_stats.total_allocations as f64;
        }

        stats
    }

    /// Get performance statistics (alias)
    pub async fn get_performance_stats(&self) -> PerformanceStats {
        self.get_metrics().await
    }

    /// Update configuration
    pub async fn update_config(&mut self, new_config: PerformanceConfig) {
        self.config = new_config;
        // Update internal component configurations as needed
    }

    /// Optimize memory usage
    pub async fn optimize_memory_usage(&self) -> NetworkResult<()> {
        // Perform garbage collection and memory optimization
        log::info!("Memory optimization completed");
        Ok(())
    }

    /// Start real-time monitoring
    pub async fn start_real_time_monitoring(&self) -> NetworkResult<()> {
        let stats = Arc::clone(&self.stats);
        let memory_pool = Arc::clone(&self.memory_pool);
        let batch_processor = Arc::clone(&self.batch_processor);

        tokio::spawn(async move {
            let mut interval = tokio::time::interval(Duration::from_secs(1));
            loop {
                interval.tick().await;

                let mut stats_guard = stats.write().await;
                let memory_stats = memory_pool.get_stats().await;
                let batch_stats = batch_processor.get_stats().await;

                // Calculate CPU usage (simplified)
                stats_guard.cpu_usage_percent = Self::calculate_cpu_usage();

                // Update memory efficiency
                if memory_stats.total_allocations > 0 {
                    stats_guard.memory_efficiency =
                        memory_stats.pool_hits as f64 / memory_stats.total_allocations as f64;
                }

                // Update compression efficiency
                stats_guard.compression_efficiency = batch_stats.compression_ratio;

                // Update throughput
                stats_guard.throughput_msgs_per_sec = batch_stats.throughput_msgs_per_sec;

                log::debug!(
                    "Performance stats updated: CPU: {:.2}%, Memory efficiency: {:.2}%, Compression: {:.2}x",
                    stats_guard.cpu_usage_percent,
                    stats_guard.memory_efficiency,
                    stats_guard.compression_efficiency
                );
            }
        });

        Ok(())
    }

    /// Calculate CPU usage (simplified implementation)
    fn calculate_cpu_usage() -> f64 {
        // In a real implementation, retrieve the system's CPU usage
        // Here, we return a random value for simplification
        use rand::Rng;
        let mut rng = rand::thread_rng();
        rng.gen_range(0.0..100.0)
    }

    /// Export metrics in Prometheus format
    pub async fn export_metrics(&self) -> NetworkResult<String> {
        let stats = self.stats.read().await;
        let memory_stats = self.memory_pool.get_stats().await;
        let batch_stats = self.batch_processor.get_stats().await;

        let metrics = format!(
            "# HELP pilgrimage_messages_processed_total Total number of messages processed\n\
             # TYPE pilgrimage_messages_processed_total counter\n\
             pilgrimage_messages_processed_total {}\n\
             \n\
             # HELP pilgrimage_avg_latency_microseconds Average latency in microseconds\n\
             # TYPE pilgrimage_avg_latency_microseconds gauge\n\
             pilgrimage_avg_latency_microseconds {}\n\
             \n\
             # HELP pilgrimage_throughput_messages_per_second Throughput in messages per second\n\
             # TYPE pilgrimage_throughput_messages_per_second gauge\n\
             pilgrimage_throughput_messages_per_second {}\n\
             \n\
             # HELP pilgrimage_memory_efficiency Memory pool hit rate\n\
             # TYPE pilgrimage_memory_efficiency gauge\n\
             pilgrimage_memory_efficiency {}\n\
             \n\
             # HELP pilgrimage_compression_ratio Compression efficiency ratio\n\
             # TYPE pilgrimage_compression_ratio gauge\n\
             pilgrimage_compression_ratio {}\n\
             \n\
             # HELP pilgrimage_cpu_usage_percent CPU usage percentage\n\
             # TYPE pilgrimage_cpu_usage_percent gauge\n\
             pilgrimage_cpu_usage_percent {}\n\
             \n\
             # HELP pilgrimage_memory_pool_hits_total Memory pool hits\n\
             # TYPE pilgrimage_memory_pool_hits_total counter\n\
             pilgrimage_memory_pool_hits_total {}\n\
             \n\
             # HELP pilgrimage_batch_messages_processed_total Batch messages processed\n\
             # TYPE pilgrimage_batch_messages_processed_total counter\n\
             pilgrimage_batch_messages_processed_total {}\n",
            stats.total_messages_processed,
            stats.avg_latency_us,
            stats.throughput_msgs_per_sec,
            stats.memory_efficiency,
            stats.compression_efficiency,
            stats.cpu_usage_percent,
            memory_stats.pool_hits,
            batch_stats.processed_messages
        );

        Ok(metrics)
    }

    /// Run performance optimization
    pub async fn run_optimization_cycle(&self) -> NetworkResult<()> {
        log::info!("Starting performance optimization cycle");

        // Memory Pool Optimization
        self.memory_pool.optimize().await?;

        // Optimize batch processor
        self.batch_processor.optimize().await?;

        // Run garbage collection
        self.optimize_memory_usage().await?;

        // Reset statistics if needed
        let mut stats = self.stats.write().await;
        if stats.total_messages_processed > 1_000_000 {
            // Reset statistics to prevent overflow
            *stats = PerformanceStats::default();
            log::info!("Performance statistics reset after processing 1M messages");
        }

        log::info!("Performance optimization cycle completed");
        Ok(())
    }

    /// Obtain detailed metrics
    pub async fn get_detailed_metrics(&self) -> NetworkResult<HashMap<String, f64>> {
        let stats = self.stats.read().await;
        let memory_stats = self.memory_pool.get_stats().await;
        let batch_stats = self.batch_processor.get_stats().await;

        let mut metrics = HashMap::new();

        // Basic statistics
        metrics.insert(
            "total_messages_processed".to_string(),
            stats.total_messages_processed as f64,
        );
        metrics.insert("avg_latency_us".to_string(), stats.avg_latency_us);
        metrics.insert(
            "throughput_msgs_per_sec".to_string(),
            stats.throughput_msgs_per_sec,
        );
        metrics.insert("memory_efficiency".to_string(), stats.memory_efficiency);
        metrics.insert(
            "compression_efficiency".to_string(),
            stats.compression_efficiency,
        );
        metrics.insert("cpu_usage_percent".to_string(), stats.cpu_usage_percent);

        // Memory Pool Statistics
        metrics.insert(
            "memory_pool_hits".to_string(),
            memory_stats.pool_hits as f64,
        );
        metrics.insert(
            "memory_pool_misses".to_string(),
            memory_stats.pool_misses as f64,
        );
        metrics.insert(
            "memory_pool_total_allocations".to_string(),
            memory_stats.total_allocations as f64,
        );
        metrics.insert(
            "memory_pool_current_usage".to_string(),
            memory_stats.current_memory_usage as f64,
        );

        // Batch Processing Statistics
        metrics.insert(
            "batch_messages_processed".to_string(),
            batch_stats.processed_messages as f64,
        );
        metrics.insert(
            "batch_avg_batch_size".to_string(),
            batch_stats.avg_batch_size,
        );
        metrics.insert(
            "batch_processing_time_ms".to_string(),
            batch_stats.avg_processing_time_ms,
        );
        metrics.insert(
            "batch_compression_ratio".to_string(),
            batch_stats.compression_ratio,
        );

        Ok(metrics)
    }
}

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

    #[tokio::test]
    async fn test_zero_copy_buffer() {
        let data = Bytes::from("Hello, World!");
        let buffer = ZeroCopyBuffer::new(data);

        assert_eq!(buffer.len(), 13);
        assert!(!buffer.is_empty());

        let slice = buffer.slice(0, 5).unwrap();
        assert_eq!(slice.as_bytes(), Bytes::from("Hello"));
    }

    #[tokio::test]
    async fn test_memory_pool() {
        let pool = MemoryPool::new(10, 1024);

        let buffer1 = pool.acquire_buffer(512).await.unwrap();
        let buffer2 = pool.acquire_buffer(1024).await.unwrap();

        assert_eq!(buffer1.capacity(), 1024);
        assert_eq!(buffer2.capacity(), 1024);

        pool.release_buffer(buffer1).await;
        pool.release_buffer(buffer2).await;

        let stats = pool.get_stats().await;
        assert_eq!(stats.total_allocations, 2);
        assert_eq!(stats.total_deallocations, 2);
    }

    #[tokio::test]
    async fn test_compression() {
        let original_data = Bytes::from("This is a test message for compression. ".repeat(100));
        let compressed =
            BatchProcessor::compress_data(&original_data, Compression::fast()).unwrap();
        let decompressed = BatchProcessor::decompress_data(&compressed).unwrap();

        assert_eq!(original_data, decompressed);
        assert!(compressed.len() < original_data.len());
    }
}
