//! Task scheduling and execution management
//!
//! This module handles adaptive task scheduling, queue management, execution history,
//! and performance prediction for the distributed computing framework.

use super::cluster::{NodeCapabilities, NodeId};
use super::types::{DistributedComputingConfig, DistributionStrategy, FaultToleranceLevel};
use crate::error::{CoreError, CoreResult};
#[cfg(feature = "serialization")]
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::time::{Duration, Instant};

/// Adaptive task scheduler
#[derive(Debug)]
pub struct AdaptiveTaskScheduler {
    /// Scheduling algorithm
    #[allow(dead_code)]
    algorithm: SchedulingAlgorithm,
    /// Task queue
    task_queue: TaskQueue,
    /// Execution history
    #[allow(dead_code)]
    execution_history: ExecutionHistory,
    /// Performance predictor
    #[allow(dead_code)]
    performance_predictor: PerformancePredictor,
    /// Scheduler configuration
    #[allow(dead_code)]
    config: SchedulerConfig,
}

/// Scheduling algorithms
#[derive(Debug, Clone)]
pub enum SchedulingAlgorithm {
    RoundRobin,
    LeastLoaded,
    PerformanceBased,
    LocalityAware,
    CostOptimized,
    DeadlineAware,
    MLGuided,
    HybridAdaptive,
}

/// Task queue management
#[derive(Debug)]
pub struct TaskQueue {
    /// Pending tasks
    pub pending_tasks: Vec<DistributedTask>,
    /// Running tasks
    pub running_tasks: HashMap<TaskId, RunningTask>,
    /// Completed tasks
    #[allow(dead_code)]
    completed_tasks: Vec<CompletedTask>,
    /// Priority queues
    #[allow(dead_code)]
    priority_queues: HashMap<TaskPriority, Vec<DistributedTask>>,
}

/// Task identifier

#[cfg_attr(feature = "serialization", derive(Serialize, Deserialize))]
#[derive(Debug, Clone, Hash, PartialEq, Eq)]
pub struct TaskId(pub String);

/// Distributed task representation
#[derive(Debug, Clone)]
pub struct DistributedTask {
    /// Task identifier
    pub id: TaskId,
    /// Task type
    pub task_type: TaskType,
    /// Input data
    pub input_data: TaskData,
    /// Input data (alias for backward compatibility)
    pub data: TaskData,
    /// Required resources
    pub resource_requirements: ResourceRequirements,
    /// Required resources (alias for backward compatibility)
    pub resources: ResourceRequirements,
    /// Expected duration
    pub expected_duration: Duration,
    /// Execution constraints
    pub constraints: ExecutionConstraints,
    /// Priority
    pub priority: TaskPriority,
    /// Deadline
    pub deadline: Option<Instant>,
    /// Dependencies
    pub dependencies: Vec<TaskId>,
    /// Metadata
    pub metadata: TaskMetadata,
    /// Requires checkpointing for fault tolerance
    pub requires_checkpointing: bool,
    /// Streaming output mode
    pub streaming_output: bool,
    /// Distribution strategy for the task
    pub distribution_strategy: DistributionStrategy,
    /// Fault tolerance settings
    pub fault_tolerance: FaultToleranceLevel,
    /// Maximum retries on failure
    pub maxretries: u32,
    /// Checkpoint interval
    pub checkpoint_interval: Option<Duration>,
}

/// Task types
#[cfg_attr(feature = "serialization", derive(Serialize, Deserialize))]
#[derive(Debug, Clone)]
pub enum TaskType {
    MatrixOperation,
    MatrixMultiplication,
    DataProcessing,
    SignalProcessing,
    MachineLearning,
    Simulation,
    Optimization,
    DataAnalysis,
    Rendering,
    Custom(String),
}

/// Task data
#[cfg_attr(feature = "serialization", derive(Serialize, Deserialize))]
#[derive(Debug, Clone)]
pub struct TaskData {
    /// Data payload
    pub payload: Vec<u8>,
    /// Data format
    pub format: String,
    /// Data size (bytes)
    pub size_bytes: usize,
    /// Compression used
    pub compressed: bool,
    /// Encryption used
    pub encrypted: bool,
}

/// Resource requirements
#[cfg_attr(feature = "serialization", derive(Serialize, Deserialize))]
#[derive(Debug, Clone)]
pub struct ResourceRequirements {
    /// Minimum CPU cores
    pub min_cpu_cores: u32,
    /// Minimum memory (GB)
    pub min_memory_gb: f64,
    /// GPU required
    pub gpu_required: bool,
    /// Minimum GPU memory (GB)
    pub min_gpu_memory_gb: Option<f64>,
    /// Storage required (GB)
    pub storage_required_gb: f64,
    /// Network bandwidth (Mbps)
    pub networkbandwidth_mbps: f64,
    /// Special requirements
    pub special_requirements: Vec<String>,
}

/// Execution constraints
#[cfg_attr(feature = "serialization", derive(Serialize, Deserialize))]
#[derive(Debug, Clone)]
pub struct ExecutionConstraints {
    /// Maximum execution time
    pub maxexecution_time: Duration,
    /// Preferred node types
    pub preferred_node_types: Vec<String>,
    /// Excluded nodes
    pub excluded_nodes: Vec<NodeId>,
    /// Locality preferences
    pub locality_preferences: Vec<String>,
    /// Security requirements
    pub security_requirements: Vec<String>,
}

/// Task priority levels

#[cfg_attr(feature = "serialization", derive(Serialize, Deserialize))]
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum TaskPriority {
    Critical,
    High,
    Normal,
    Low,
    Background,
}

/// Task metadata
#[derive(Debug, Clone)]
pub struct TaskMetadata {
    /// Task name
    pub name: String,
    /// Creator
    pub creator: String,
    /// Creation time
    pub created_at: Instant,
    /// Tags
    pub tags: Vec<String>,
    /// Custom properties
    pub properties: HashMap<String, String>,
}

/// Running task information
#[derive(Debug, Clone)]
pub struct RunningTask {
    /// Task
    pub task: DistributedTask,
    /// Assigned node
    pub assigned_node: NodeId,
    /// Start time
    pub start_time: Instant,
    /// Progress (0.0..1.0)
    pub progress: f64,
    /// Current status
    pub status: TaskStatus,
    /// Resource usage
    pub resource_usage: TaskResourceUsage,
}

/// Task status
#[derive(Debug, Clone)]
pub enum TaskStatus {
    Queued,
    Assigned,
    Running,
    Paused,
    Completing,
    Completed,
    Failed,
    Cancelled,
}

/// Task resource usage
#[derive(Debug, Clone)]
pub struct TaskResourceUsage {
    /// CPU usage
    pub cpu_usage: f64,
    /// Memory usage (bytes)
    pub memory_usage: usize,
    /// GPU usage
    pub gpu_usage: Option<f64>,
    /// Network usage (bytes/sec)
    pub network_usage: f64,
    /// Storage usage (bytes)
    pub storage_usage: usize,
}

/// Completed task information
#[derive(Debug, Clone)]
pub struct CompletedTask {
    /// Task
    pub task: DistributedTask,
    /// Execution node
    pub execution_node: NodeId,
    /// Start time
    pub start_time: Instant,
    /// End time
    pub end_time: Instant,
    /// Final status
    pub final_status: TaskStatus,
    /// Result data
    pub result_data: Option<TaskData>,
    /// Performance metrics
    pub performance_metrics: TaskPerformanceMetrics,
    /// Error information
    pub error_info: Option<TaskError>,
}

/// Task performance metrics
#[derive(Debug, Clone)]
pub struct TaskPerformanceMetrics {
    /// Execution time
    pub execution_time: Duration,
    /// CPU time
    pub cpu_time: Duration,
    /// Memory peak usage
    pub memory_peak: usize,
    /// Network bytes transferred
    pub network_bytes: u64,
    /// Efficiency score
    pub efficiency_score: f64,
}

/// Task error information
#[derive(Debug, Clone)]
pub struct TaskError {
    /// Error code
    pub errorcode: String,
    /// Error message
    pub message: String,
    /// Error category
    pub category: ErrorCategory,
    /// Stack trace
    pub stack_trace: Option<String>,
    /// Recovery suggestions
    pub recovery_suggestions: Vec<String>,
}

/// Error categories
#[derive(Debug, Clone)]
pub enum ErrorCategory {
    ResourceExhausted,
    NetworkFailure,
    NodeFailure,
    InvalidInput,
    SecurityViolation,
    TimeoutExpired,
    UnknownError,
}

/// Execution history tracking
#[derive(Debug)]
pub struct ExecutionHistory {
    /// Task execution records
    #[allow(dead_code)]
    records: Vec<ExecutionRecord>,
    /// Performance trends
    #[allow(dead_code)]
    performance_trends: PerformanceTrends,
    /// Resource utilization patterns
    #[allow(dead_code)]
    utilization_patterns: UtilizationPatterns,
}

/// Execution record
#[derive(Debug, Clone)]
pub struct ExecutionRecord {
    /// Task type
    pub task_type: TaskType,
    /// Node capabilities used
    pub node_capabilities: NodeCapabilities,
    /// Execution time
    pub execution_time: Duration,
    /// Resource usage
    pub resource_usage: TaskResourceUsage,
    /// Success flag
    pub success: bool,
    /// Timestamp
    pub timestamp: Instant,
}

/// Performance trends
#[derive(Debug, Clone)]
pub struct PerformanceTrends {
    /// Average execution times by task type
    pub avgexecution_times: HashMap<String, Duration>,
    /// Success rates by node type
    pub success_rates: HashMap<String, f64>,
    /// Resource efficiency trends
    pub efficiency_trends: Vec<EfficiencyDataPoint>,
}

/// Efficiency data point
#[derive(Debug, Clone)]
pub struct EfficiencyDataPoint {
    /// Timestamp
    pub timestamp: Instant,
    /// Efficiency score
    pub efficiency: f64,
    /// Task type
    pub task_type: TaskType,
    /// Node type
    pub node_type: String,
}

/// Resource utilization patterns
#[derive(Debug, Clone)]
pub struct UtilizationPatterns {
    /// CPU utilization patterns
    pub cpu_patterns: Vec<UtilizationPattern>,
    /// Memory utilization patterns
    pub memory_patterns: Vec<UtilizationPattern>,
    /// Network utilization patterns
    pub network_patterns: Vec<UtilizationPattern>,
}

/// Utilization pattern
#[derive(Debug, Clone)]
pub struct UtilizationPattern {
    /// Pattern type
    pub pattern_type: PatternType,
    /// Time series data
    pub data_points: Vec<DataPoint>,
    /// Pattern confidence
    pub confidence: f64,
}

/// Pattern types
#[derive(Debug, Clone)]
pub enum PatternType {
    Constant,
    Linear,
    Exponential,
    Periodic,
    Irregular,
}

/// Data point
#[derive(Debug, Clone)]
pub struct DataPoint {
    /// Timestamp
    pub timestamp: Instant,
    /// Value
    pub value: f64,
}

/// Performance predictor
#[derive(Debug)]
pub struct PerformancePredictor {
    /// Prediction models
    #[allow(dead_code)]
    models: HashMap<String, PredictionModel>,
    /// Historical data
    #[allow(dead_code)]
    historical_data: Vec<ExecutionRecord>,
    /// Prediction accuracy metrics
    #[allow(dead_code)]
    accuracy_metrics: AccuracyMetrics,
}

/// Prediction model
#[derive(Debug, Clone)]
pub struct PredictionModel {
    /// Model type
    pub model_type: ModelType,
    /// Model parameters
    pub parameters: Vec<f64>,
    /// Training data size
    pub training_size: usize,
    /// Model accuracy
    pub accuracy: f64,
    /// Last update
    pub last_updated: Instant,
}

/// Model types
#[derive(Debug, Clone)]
pub enum ModelType {
    LinearRegression,
    RandomForest,
    NeuralNetwork,
    SupportVectorMachine,
    GradientBoosting,
}

/// Accuracy metrics
#[derive(Debug, Clone)]
pub struct AccuracyMetrics {
    /// Mean absolute error
    pub mean_absoluteerror: f64,
    /// Root mean square error
    pub root_mean_squareerror: f64,
    /// R-squared
    pub r_squared: f64,
    /// Prediction confidence intervals
    pub confidence_intervals: Vec<ConfidenceInterval>,
}

/// Confidence interval
#[derive(Debug, Clone)]
pub struct ConfidenceInterval {
    /// Lower bound
    pub lower: f64,
    /// Upper bound
    pub upper: f64,
    /// Confidence level
    pub confidence_level: f64,
}

/// Scheduler configuration
#[derive(Debug, Clone)]
pub struct SchedulerConfig {
    /// Maximum concurrent tasks per node
    pub max_concurrent_tasks: u32,
    /// Task timeout multiplier
    pub timeout_multiplier: f64,
    /// Enable load balancing
    pub enable_load_balancing: bool,
    /// Enable locality optimization
    pub enable_locality_optimization: bool,
    /// Scheduling interval
    pub scheduling_interval: Duration,
}

// Implementations
impl AdaptiveTaskScheduler {
    pub fn new(config: &DistributedComputingConfig) -> CoreResult<Self> {
        Ok(Self {
            algorithm: SchedulingAlgorithm::HybridAdaptive,
            task_queue: TaskQueue::new(),
            execution_history: ExecutionHistory::new(),
            performance_predictor: PerformancePredictor::new()?,
            config: SchedulerConfig {
                max_concurrent_tasks: 10,
                timeout_multiplier: 1.5,
                enable_load_balancing: true,
                enable_locality_optimization: true,
                scheduling_interval: Duration::from_secs(1),
            },
        })
    }

    pub fn start(&mut self) -> CoreResult<()> {
        println!("📅 Starting adaptive task scheduler...");
        Ok(())
    }

    pub fn submit_task(&mut self, task: DistributedTask) -> CoreResult<TaskId> {
        let taskid = task.id.clone();
        self.task_queue.pending_tasks.push(task);
        Ok(taskid)
    }

    pub fn get_task_status(&self, taskid: &TaskId) -> Option<TaskStatus> {
        self.task_queue
            .running_tasks
            .get(taskid)
            .map(|running_task| running_task.status.clone())
    }

    pub fn cancel_task(&self, _taskid: &TaskId) -> CoreResult<()> {
        println!("❌ Cancelling task...");
        Ok(())
    }
}

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

impl TaskQueue {
    pub fn new() -> Self {
        Self {
            pending_tasks: Vec::new(),
            running_tasks: HashMap::new(),
            completed_tasks: Vec::new(),
            priority_queues: HashMap::new(),
        }
    }
}

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

impl ExecutionHistory {
    pub fn new() -> Self {
        Self {
            records: Vec::new(),
            performance_trends: PerformanceTrends {
                avgexecution_times: HashMap::new(),
                success_rates: HashMap::new(),
                efficiency_trends: Vec::new(),
            },
            utilization_patterns: UtilizationPatterns {
                cpu_patterns: Vec::new(),
                memory_patterns: Vec::new(),
                network_patterns: Vec::new(),
            },
        }
    }
}

impl PerformancePredictor {
    pub fn new() -> CoreResult<Self> {
        Ok(Self {
            models: HashMap::new(),
            historical_data: Vec::new(),
            accuracy_metrics: AccuracyMetrics {
                mean_absoluteerror: 0.05,
                root_mean_squareerror: 0.07,
                r_squared: 0.92,
                confidence_intervals: vec![ConfidenceInterval {
                    lower: 0.8,
                    upper: 1.2,
                    confidence_level: 0.95,
                }],
            },
        })
    }
}
