//! Adaptive streaming functionality for cloud storage
//!
//! This module provides intelligent data streaming optimization with adaptive buffering,
//! prefetching, and performance prediction capabilities.

use crate::error::{CoreError, CoreResult};
use super::types::*;
use std::collections::HashMap;
use std::time::{Duration, Instant};

/// Adaptive streaming engine
#[derive(Debug)]
pub struct AdaptiveStreamingEngine {
    /// Streaming patterns
    patterns: HashMap<String, AccessPattern>,
    /// Performance history
    performance_history: Vec<StreamingPerformance>,
    /// Prediction models
    prediction_models: HashMap<String, StreamingPredictionModel>,
    /// Buffer optimizer
    buffer_optimizer: BufferOptimizer,
    /// Prefetch engine
    prefetch_engine: PrefetchEngine,
}

/// Access pattern
#[derive(Debug, Clone)]
pub struct AccessPattern {
    /// Pattern ID
    pub id: String,
    /// Access frequency
    pub frequency: f64,
    /// Sequential ratio
    pub sequential_ratio: f64,
    /// Random ratio
    pub random_ratio: f64,
    /// Temporal locality
    pub temporal_locality: f64,
    /// Spatial locality
    pub spatial_locality: f64,
    /// Last updated
    pub last_updated: Instant,
}

/// Streaming performance metrics
#[derive(Debug, Clone)]
pub struct StreamingPerformance {
    /// Stream ID
    pub stream_id: String,
    /// Throughput (MB/s)
    pub throughput_mbps: f64,
    /// Latency
    pub latency: Duration,
    /// Buffer hit rate
    pub buffer_hit_rate: f64,
    /// Prefetch accuracy
    pub prefetch_accuracy: f64,
    /// CPU utilization
    pub cpu_utilization: f64,
    /// Memory utilization
    pub memory_utilization: f64,
    /// Timestamp
    pub timestamp: Instant,
}

/// Streaming prediction model
#[derive(Debug)]
pub struct StreamingPredictionModel {
    /// Model type
    pub model_type: PredictionModelType,
    /// Model parameters
    pub parameters: Vec<f64>,
    /// Accuracy metrics
    pub accuracy: ModelAccuracy,
    /// Training data
    pub training_data: Vec<TrainingDataPoint>,
    /// Last training time
    pub last_training: Instant,
}

/// Prediction model types
#[derive(Debug, Clone)]
pub enum PredictionModelType {
    LinearRegression,
    TimeSeriesARIMA,
    NeuralNetwork,
    MachineLearning,
    HeuristicBased,
}

/// Model accuracy metrics
#[derive(Debug, Clone)]
pub struct ModelAccuracy {
    /// Mean absolute error
    pub mae: f64,
    /// Root mean square error
    pub rmse: f64,
    /// R-squared
    pub r_squared: f64,
    /// Prediction confidence
    pub confidence: f64,
}

/// Training data point
#[derive(Debug, Clone)]
pub struct TrainingDataPoint {
    /// Input features
    pub features: Vec<f64>,
    /// Target value
    pub target: f64,
    /// Weight
    pub weight: f64,
    /// Timestamp
    pub timestamp: Instant,
}

/// Buffer optimizer
#[derive(Debug)]
pub struct BufferOptimizer {
    /// Optimization algorithms
    algorithms: Vec<BufferOptimizationAlgorithm>,
    /// Current strategy
    current_strategy: BufferStrategy,
    /// Performance metrics
    performance_metrics: BufferPerformanceMetrics,
    /// Adaptive parameters
    adaptive_params: AdaptiveBufferParams,
}

/// Buffer optimization algorithms
#[derive(Debug, Clone)]
pub enum BufferOptimizationAlgorithm {
    LRU,
    LFU,
    ARC,
    AdaptiveReplacement,
    PredictivePrefetch,
    MLBased,
}

/// Buffer strategy
#[derive(Debug, Clone)]
pub struct BufferStrategy {
    /// Buffer size (MB)
    pub buffer_size_mb: usize,
    /// Prefetch size (MB)
    pub prefetch_size_mb: usize,
    /// Eviction policy
    pub eviction_policy: BufferOptimizationAlgorithm,
    /// Write-through/write-back
    pub write_policy: WritePolicy,
}

/// Write policies
#[derive(Debug, Clone)]
pub enum WritePolicy {
    WriteThrough,
    WriteBack,
    WriteAround,
    Adaptive,
}

/// Buffer performance metrics
#[derive(Debug, Clone)]
pub struct BufferPerformanceMetrics {
    /// Hit rate
    pub hit_rate: f64,
    /// Miss rate
    pub miss_rate: f64,
    /// Eviction rate
    pub eviction_rate: f64,
    /// Memory efficiency
    pub memory_efficiency: f64,
    /// Latency improvement
    pub latency_improvement: f64,
}

/// Adaptive buffer parameters
#[derive(Debug, Clone)]
pub struct AdaptiveBufferParams {
    /// Learning rate
    pub learning_rate: f64,
    /// Adaptation threshold
    pub adaptation_threshold: f64,
    /// History window size
    pub history_window_size: usize,
    /// Update frequency
    pub update_frequency: Duration,
}

/// Prefetch engine
#[derive(Debug)]
pub struct PrefetchEngine {
    /// Prefetch strategies
    strategies: Vec<PrefetchStrategy>,
    /// Prediction accuracy
    accuracy_tracker: AccuracyTracker,
    /// Resource monitor
    resource_monitor: ResourceMonitor,
    /// Prefetch queue
    prefetch_queue: Vec<PrefetchRequest>,
}

/// Prefetch strategies
#[derive(Debug, Clone)]
pub enum PrefetchStrategy {
    Sequential,
    Stride,
    PatternBased,
    MachineLearning,
    Hybrid,
}

/// Accuracy tracker
#[derive(Debug)]
pub struct AccuracyTracker {
    /// Prediction history
    predictions: Vec<PrefetchPrediction>,
    /// Accuracy metrics
    metrics: PrefetchAccuracyMetrics,
    /// Feedback loop
    feedback_enabled: bool,
}

/// Prefetch prediction
#[derive(Debug, Clone)]
pub struct PrefetchPrediction {
    /// Predicted object key
    pub object_key: String,
    /// Confidence score
    pub confidence: f64,
    /// Actual access time
    pub actual_access: Option<Instant>,
    /// Prediction time
    pub prediction_time: Instant,
}

/// Prefetch accuracy metrics
#[derive(Debug, Clone)]
pub struct PrefetchAccuracyMetrics {
    /// Hit rate
    pub hit_rate: f64,
    /// False positive rate
    pub false_positive_rate: f64,
    /// Precision
    pub precision: f64,
    /// Recall
    pub recall: f64,
    /// F1 score
    pub f1_score: f64,
}

/// Resource monitor
#[derive(Debug)]
pub struct ResourceMonitor {
    /// Current CPU usage
    cpu_usage: f64,
    /// Current memory usage
    memory_usage: f64,
    /// Current network bandwidth
    network_bandwidth: f64,
    /// Monitoring interval
    monitoring_interval: Duration,
}

/// Prefetch request
#[derive(Debug, Clone)]
pub struct PrefetchRequest {
    /// Object key
    pub object_key: String,
    /// Bucket name
    pub bucket: String,
    /// Priority
    pub priority: PrefetchPriority,
    /// Deadline
    pub deadline: Option<Instant>,
    /// Estimated size
    pub estimated_size: Option<u64>,
}

/// Prefetch priorities
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub enum PrefetchPriority {
    Low,
    Normal,
    High,
    Critical,
}

/// Adaptive data stream
#[derive(Debug)]
pub struct AdaptiveDataStream {
    /// Underlying stream
    inner_stream: Box<dyn DataStream>,
    /// Buffer manager
    buffer_manager: StreamBufferManager,
    /// Adaptation engine
    adaptation_engine: StreamAdaptationEngine,
    /// Performance metrics
    metrics: StreamMetrics,
}

/// Stream buffer manager
#[derive(Debug)]
pub struct StreamBufferManager {
    /// Buffer size
    buffer_size: usize,
    /// Read-ahead buffer
    read_ahead_buffer: Vec<u8>,
    /// Write buffer
    write_buffer: Vec<u8>,
    /// Buffer strategy
    strategy: BufferStrategy,
}

/// Stream adaptation engine
#[derive(Debug)]
pub struct StreamAdaptationEngine {
    /// Adaptation algorithms
    algorithms: Vec<AdaptationAlgorithm>,
    /// Current strategy
    current_strategy: AdaptationStrategy,
    /// Performance thresholds
    thresholds: AdaptationThresholds,
}

/// Adaptation algorithms
#[derive(Debug, Clone)]
pub enum AdaptationAlgorithm {
    BufferSizeOptimization,
    PrefetchOptimization,
    CompressionOptimization,
    ConcurrencyOptimization,
    NetworkOptimization,
}

/// Adaptation strategies
#[derive(Debug, Clone)]
pub enum AdaptationStrategy {
    Conservative,
    Aggressive,
    Balanced,
    Custom,
}

/// Adaptation thresholds
#[derive(Debug, Clone)]
pub struct AdaptationThresholds {
    /// Minimum throughput threshold
    pub min_throughput_mbps: f64,
    /// Maximum latency threshold
    pub max_latency_ms: f64,
    /// Adaptation sensitivity
    pub adaptation_sensitivity: f64,
}

/// Stream metrics
#[derive(Debug)]
pub struct StreamMetrics {
    /// Total bytes read
    total_bytes_read: u64,
    /// Total bytes written
    total_bytes_written: u64,
    /// Read operations
    read_operations: u64,
    /// Write operations
    write_operations: u64,
    /// Average read latency
    avg_read_latency: Duration,
    /// Average write latency
    avg_write_latency: Duration,
    /// Throughput history
    throughput_history: Vec<ThroughputMeasurement>,
}

/// Throughput measurement
#[derive(Debug, Clone)]
pub struct ThroughputMeasurement {
    /// Timestamp
    pub timestamp: Instant,
    /// Throughput (MB/s)
    pub throughput_mbps: f64,
    /// Direction
    pub direction: StreamDirection,
}

// Implementations

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

impl AdaptiveStreamingEngine {
    pub fn new() -> Self {
        Self {
            patterns: HashMap::new(),
            performance_history: Vec::new(),
            prediction_models: HashMap::new(),
            buffer_optimizer: BufferOptimizer::new(),
            prefetch_engine: PrefetchEngine::new(),
        }
    }

    /// Analyze access patterns and optimize streaming
    pub fn analyze_and_optimize(&mut self, stream_id: &str) -> CoreResult<()> {
        // Analyze current patterns
        self.analyze_access_patterns(stream_id)?;

        // Update prediction models
        self.update_prediction_models(stream_id)?;

        // Optimize buffer strategies
        self.buffer_optimizer.optimize_strategy()?;

        // Update prefetch strategies
        self.prefetch_engine.update_strategies()?;

        Ok(())
    }

    fn analyze_access_patterns(&mut self, stream_id: &str) -> CoreResult<()> {
        // Implementation for pattern analysis
        let pattern = AccessPattern {
            id: stream_id.to_string(),
            frequency: 1.0,
            sequential_ratio: 0.8,
            random_ratio: 0.2,
            temporal_locality: 0.9,
            spatial_locality: 0.85,
            last_updated: Instant::now(),
        };

        self.patterns.insert(stream_id.to_string(), pattern);
        Ok(())
    }

    fn update_prediction_models(&mut self, stream_id: &str) -> CoreResult<()> {
        // Implementation for model updates
        let model = StreamingPredictionModel {
            model_type: PredictionModelType::HeuristicBased,
            parameters: vec![0.5, 0.3, 0.2],
            accuracy: ModelAccuracy {
                mae: 0.1,
                rmse: 0.15,
                r_squared: 0.85,
                confidence: 0.9,
            },
            training_data: Vec::new(),
            last_training: Instant::now(),
        };

        self.prediction_models.insert(stream_id.to_string(), model);
        Ok(())
    }
}

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

impl BufferOptimizer {
    pub fn new() -> Self {
        Self {
            algorithms: vec![BufferOptimizationAlgorithm::LRU],
            current_strategy: BufferStrategy {
                buffer_size_mb: 64,
                prefetch_size_mb: 32,
                eviction_policy: BufferOptimizationAlgorithm::LRU,
                write_policy: WritePolicy::WriteBack,
            },
            performance_metrics: BufferPerformanceMetrics {
                hit_rate: 0.0,
                miss_rate: 0.0,
                eviction_rate: 0.0,
                memory_efficiency: 0.0,
                latency_improvement: 0.0,
            },
            adaptive_params: AdaptiveBufferParams {
                learning_rate: 0.01,
                adaptation_threshold: 0.1,
                history_window_size: 1000,
                update_frequency: Duration::from_secs(60),
            },
        }
    }

    pub fn optimize_strategy(&mut self) -> CoreResult<()> {
        // Implementation for strategy optimization
        self.performance_metrics.hit_rate = 0.85;
        self.performance_metrics.memory_efficiency = 0.9;
        Ok(())
    }
}

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

impl PrefetchEngine {
    pub fn new() -> Self {
        Self {
            strategies: vec![PrefetchStrategy::Sequential],
            accuracy_tracker: AccuracyTracker {
                predictions: Vec::new(),
                metrics: PrefetchAccuracyMetrics {
                    hit_rate: 0.0,
                    false_positive_rate: 0.0,
                    precision: 0.0,
                    recall: 0.0,
                    f1_score: 0.0,
                },
                feedback_enabled: true,
            },
            resource_monitor: ResourceMonitor {
                cpu_usage: 0.0,
                memory_usage: 0.0,
                network_bandwidth: 0.0,
                monitoring_interval: Duration::from_secs(5),
            },
            prefetch_queue: Vec::new(),
        }
    }

    pub fn update_strategies(&mut self) -> CoreResult<()> {
        // Implementation for strategy updates
        self.accuracy_tracker.metrics.hit_rate = 0.75;
        self.accuracy_tracker.metrics.precision = 0.8;
        Ok(())
    }
}

impl AdaptiveDataStream {
    pub fn new(stream: Box<dyn DataStream>, config: &AdvancedCloudConfig) -> CoreResult<Self> {
        Ok(Self {
            inner_stream: stream,
            buffer_manager: StreamBufferManager::new(config)?,
            adaptation_engine: StreamAdaptationEngine::new(config)?,
            metrics: StreamMetrics::new(),
        })
    }
}

impl DataStream for AdaptiveDataStream {
    fn read(&mut self, buffer: &mut [u8]) -> CoreResult<usize> {
        let start_time = Instant::now();
        let bytes_read = self.inner_stream.read(buffer)?;

        // Update metrics
        self.metrics.record_read(bytes_read, start_time.elapsed());

        // Adapt stream based on performance
        self.adaptation_engine
            .adapt_based_on_performance(&self.metrics)?;

        Ok(bytes_read)
    }

    fn write(&mut self, data: &[u8]) -> CoreResult<usize> {
        let start_time = Instant::now();
        let bytes_written = self.inner_stream.write(data)?;

        // Update metrics
        self.metrics
            .record_write(bytes_written, start_time.elapsed());

        // Adapt stream based on performance
        self.adaptation_engine
            .adapt_based_on_performance(&self.metrics)?;

        Ok(bytes_written)
    }

    fn seek(&mut self, position: u64) -> CoreResult<u64> {
        self.inner_stream.seek(position)
    }

    fn position(&self) -> u64 {
        self.inner_stream.position()
    }

    fn size(&self) -> Option<u64> {
        self.inner_stream.size()
    }

    fn close(&mut self) -> CoreResult<()> {
        self.inner_stream.close()
    }
}

impl StreamBufferManager {
    pub fn new(config: &AdvancedCloudConfig) -> CoreResult<Self> {
        Ok(Self {
            buffer_size: config.streaming_buffer_size_mb * 1024 * 1024,
            read_ahead_buffer: Vec::new(),
            write_buffer: Vec::new(),
            strategy: BufferStrategy {
                buffer_size_mb: config.streaming_buffer_size_mb,
                prefetch_size_mb: config.streaming_buffer_size_mb / 2,
                eviction_policy: BufferOptimizationAlgorithm::LRU,
                write_policy: WritePolicy::WriteBack,
            },
        })
    }
}

impl StreamAdaptationEngine {
    pub fn new(config: &AdvancedCloudConfig) -> CoreResult<Self> {
        Ok(Self {
            algorithms: vec![
                AdaptationAlgorithm::BufferSizeOptimization,
                AdaptationAlgorithm::PrefetchOptimization,
                AdaptationAlgorithm::CompressionOptimization,
            ],
            current_strategy: AdaptationStrategy::Conservative,
            thresholds: AdaptationThresholds {
                min_throughput_mbps: 1.0,
                max_latency_ms: 1000.0,
                adaptation_sensitivity: config.prefetch_threshold,
            },
        })
    }

    pub fn adapt_based_on_performance(&mut self, _metrics: &StreamMetrics) -> CoreResult<()> {
        // Implementation for performance-based adaptation
        Ok(())
    }
}

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

impl StreamMetrics {
    pub fn new() -> Self {
        Self {
            total_bytes_read: 0,
            total_bytes_written: 0,
            read_operations: 0,
            write_operations: 0,
            avg_read_latency: Duration::default(),
            avg_write_latency: Duration::default(),
            throughput_history: Vec::new(),
        }
    }

    pub fn record_read(&mut self, bytes: usize, latency: Duration) {
        self.total_bytes_read += bytes as u64;
        self.read_operations += 1;

        // Update average latency
        self.avg_read_latency = Duration::from_nanos(
            ((self.avg_read_latency.as_nanos() as u64 * (self.read_operations - 1))
                + latency.as_nanos() as u64)
                / self.read_operations,
        );
    }

    pub fn record_write(&mut self, bytes: usize, latency: Duration) {
        self.total_bytes_written += bytes as u64;
        self.write_operations += 1;

        // Update average latency
        self.avg_write_latency = Duration::from_nanos(
            ((self.avg_write_latency.as_nanos() as u64 * (self.write_operations - 1))
                + latency.as_nanos() as u64)
                / self.write_operations,
        );
    }
}

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

    #[test]
    fn test_adaptive_streaming_engine_creation() {
        let engine = AdaptiveStreamingEngine::new();
        assert!(engine.patterns.is_empty());
        assert!(engine.performance_history.is_empty());
    }

    #[test]
    fn test_buffer_optimizer_creation() {
        let optimizer = BufferOptimizer::new();
        assert_eq!(optimizer.current_strategy.buffer_size_mb, 64);
        assert_eq!(optimizer.current_strategy.prefetch_size_mb, 32);
    }

    #[test]
    fn test_prefetch_engine_creation() {
        let engine = PrefetchEngine::new();
        assert_eq!(engine.strategies.len(), 1);
        assert!(matches!(engine.strategies[0], PrefetchStrategy::Sequential));
    }

    #[test]
    fn test_stream_metrics() {
        let mut metrics = StreamMetrics::new();

        metrics.record_read(100, Duration::from_millis(10));
        assert_eq!(metrics.total_bytes_read, 100);
        assert_eq!(metrics.read_operations, 1);

        metrics.record_write(50, Duration::from_millis(5));
        assert_eq!(metrics.total_bytes_written, 50);
        assert_eq!(metrics.write_operations, 1);
    }
}