//! Task Management Module for CUDA Optimization Execution Engine
//!
//! This module provides comprehensive task management capabilities including
//! optimization task definitions, scheduling, prioritization, dependency management,
//! task lifecycle management, metadata tracking, and execution coordination.

use serde::{Deserialize, Serialize};
use std::collections::{BTreeSet, HashMap, HashSet, VecDeque};
use std::sync::{
    atomic::AtomicU64,
    Arc, Mutex, RwLock,
};
use std::time::{Duration, Instant, SystemTime};
use uuid::Uuid;

use super::config::ExecutionConfig;

/// Helper function for serde default Instant value
fn default_instant() -> Instant {
    Instant::now()
}

/// Comprehensive optimization task for execution
///
/// Represents a complete optimization task with all necessary metadata,
/// dependencies, constraints, and execution requirements.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct OptimizationTask {
    /// Unique task identifier
    pub id: TaskId,

    /// Task name for identification
    pub name: String,

    /// Task description
    pub description: String,

    /// Task type and category
    pub task_type: OptimizationTaskType,

    /// Task execution priority
    pub priority: TaskPriority,

    /// Optimization strategy configuration
    pub strategy: OptimizationStrategy,

    /// Resource requirements for execution
    pub resource_requirements: ResourceRequirements,

    /// Execution constraints and limitations
    pub constraints: Vec<ExecutionConstraint>,

    /// Task dependencies
    pub dependencies: TaskDependencies,

    /// Task metadata and tracking information
    pub metadata: TaskMetadata,

    /// Success criteria for task completion
    pub success_criteria: Vec<SuccessCriterion>,

    /// Failure handling configuration
    pub failure_handling: FailureHandlingConfig,

    /// Execution location preferences
    pub execution_location: ExecutionLocation,

    /// Task timeout configuration
    pub timeout_config: TimeoutConfig,

    /// Custom task parameters
    pub custom_parameters: HashMap<String, TaskParameter>,

    /// Task creation timestamp
    pub created_at: SystemTime,

    /// Task deadline (if any)
    pub deadline: Option<SystemTime>,

    /// Estimated execution duration
    pub estimated_duration: Option<Duration>,
}

/// Unique task identifier
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub struct TaskId(pub Uuid);

/// Types of optimization tasks
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum OptimizationTaskType {
    /// Memory allocation optimization
    MemoryAllocation {
        allocation_size: usize,
        pattern: AllocationPattern,
        constraints: Vec<AllocationConstraint>,
    },

    /// Memory deallocation optimization
    MemoryDeallocation {
        target_addresses: Vec<usize>,
        cleanup_level: CleanupLevel,
    },

    /// Memory compaction and defragmentation
    MemoryCompaction {
        target_fragmentation: f64,
        compaction_strategy: CompactionStrategy,
    },

    /// Cache optimization
    CacheOptimization {
        cache_level: CacheLevel,
        optimization_target: CacheOptimizationTarget,
    },

    /// Bandwidth optimization
    BandwidthOptimization {
        target_bandwidth: f64,
        optimization_scope: BandwidthScope,
    },

    /// Latency optimization
    LatencyOptimization {
        target_latency: Duration,
        latency_type: LatencyType,
    },

    /// Memory pool management
    MemoryPoolManagement {
        pool_operation: PoolOperation,
        pool_parameters: PoolParameters,
    },

    /// Resource balancing
    ResourceBalancing {
        balancing_target: BalancingTarget,
        balancing_strategy: BalancingStrategy,
    },

    /// Performance monitoring
    PerformanceMonitoring {
        monitoring_scope: MonitoringScope,
        metrics_collection: MetricsCollection,
    },

    /// System diagnostics
    SystemDiagnostics {
        diagnostic_level: DiagnosticLevel,
        diagnostic_scope: DiagnosticScope,
    },

    /// Custom optimization task
    Custom {
        task_name: String,
        task_configuration: HashMap<String, String>,
    },
}

/// Task execution priorities with detailed levels
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
pub enum TaskPriority {
    /// Critical priority - highest urgency
    Critical = 0,
    /// High priority - important tasks
    High = 1,
    /// Medium priority - standard tasks
    Medium = 2,
    /// Low priority - background tasks
    Low = 3,
    /// Idle priority - run only when system is idle
    Idle = 4,
}

/// Optimization strategy configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct OptimizationStrategy {
    /// Strategy name and identifier
    pub name: String,

    /// Strategy implementation type
    pub implementation: StrategyImplementation,

    /// Strategy parameters and configuration
    pub parameters: HashMap<String, StrategyParameter>,

    /// Strategy composition for hybrid approaches
    pub composition: Option<StrategyComposition>,

    /// Strategy constraints and limitations
    pub constraints: Vec<StrategyConstraint>,

    /// Safety level for strategy execution
    pub safety_level: SafetyLevel,

    /// Expected performance improvement
    pub expected_improvement: f64,

    /// Strategy validation requirements
    pub validation_requirements: ValidationRequirements,
}

/// Strategy implementation types
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum StrategyImplementation {
    /// Built-in implementation
    Builtin(String),
    /// Plugin-based implementation
    Plugin(PluginInfo),
    /// Script-based implementation
    Script(ScriptInfo),
    /// Machine learning-based implementation
    MachineLearning(MLModelInfo),
    /// Hybrid implementation combining multiple approaches
    Hybrid(Vec<StrategyImplementation>),
    /// Custom implementation
    Custom(CustomImplementationInfo),
}

/// Strategy composition for combining multiple strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct StrategyComposition {
    /// Composition type
    pub composition_type: CompositionType,
    /// Individual strategies to combine
    pub strategies: Vec<OptimizationStrategy>,
    /// Composition weights for each strategy
    pub weights: Vec<f64>,
    /// Combination logic
    pub combination_logic: CombinationLogic,
}

/// Strategy composition types
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum CompositionType {
    /// Sequential execution of strategies
    Sequential,
    /// Parallel execution of strategies
    Parallel,
    /// Weighted combination of strategies
    Weighted,
    /// Adaptive selection based on conditions
    Adaptive,
    /// Voting-based combination
    Voting,
}

/// Strategy constraint types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum StrategyConstraint {
    /// Maximum execution time allowed
    MaxExecutionTime(Duration),
    /// Maximum memory usage allowed
    MaxMemoryUsage(usize),
    /// Required hardware capabilities
    RequiredHardware(Vec<HardwareRequirement>),
    /// Safety constraints
    SafetyConstraints(Vec<SafetyConstraint>),
    /// Performance constraints
    PerformanceConstraints(PerformanceConstraint),
    /// Custom constraint
    Custom(String, String),
}

/// Safety levels for strategy execution
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum SafetyLevel {
    /// No safety checks - maximum performance
    None,
    /// Basic safety checks
    Basic,
    /// Standard safety validation
    Standard,
    /// High safety with extensive validation
    High,
    /// Maximum safety with all checks enabled
    Maximum,
}

/// Success criteria for optimization strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SuccessCriterion {
    /// Criterion name and description
    pub name: String,
    pub description: String,

    /// Metric to evaluate
    pub metric: String,

    /// Target value for the metric
    pub target_value: f64,

    /// Comparison operator for evaluation
    pub operator: ComparisonOperator,

    /// Weight of this criterion in overall success evaluation
    pub weight: f64,

    /// Whether this criterion is mandatory
    pub mandatory: bool,

    /// Tolerance for the target value
    pub tolerance: f64,
}

/// Comparison operators for success criteria
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum ComparisonOperator {
    /// Equal to target value
    Equal,
    /// Not equal to target value
    NotEqual,
    /// Less than target value
    LessThan,
    /// Less than or equal to target value
    LessThanOrEqual,
    /// Greater than target value
    GreaterThan,
    /// Greater than or equal to target value
    GreaterThanOrEqual,
    /// Within range of target value
    Within,
    /// Outside range of target value
    Outside,
}

/// Resource requirements for task execution
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ResourceRequirements {
    /// CPU requirements
    pub cpu_requirements: CpuRequirements,

    /// Memory requirements
    pub memory_requirements: MemoryRequirements,

    /// GPU requirements
    pub gpu_requirements: GpuRequirements,

    /// Storage requirements
    pub storage_requirements: StorageRequirements,

    /// Network requirements
    pub network_requirements: NetworkRequirements,

    /// Specialized hardware requirements
    pub hardware_requirements: Vec<HardwareRequirement>,

    /// Resource allocation preferences
    pub allocation_preferences: AllocationPreferences,

    /// Resource sharing configuration
    pub sharing_configuration: SharingConfiguration,
}

/// CPU resource requirements
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CpuRequirements {
    /// Minimum number of CPU cores required
    pub min_cores: usize,
    /// Preferred number of CPU cores
    pub preferred_cores: usize,
    /// Maximum number of CPU cores that can be utilized
    pub max_cores: usize,
    /// CPU architecture requirements
    pub architecture_requirements: Vec<String>,
    /// Minimum CPU frequency in GHz
    pub min_frequency_ghz: f64,
    /// CPU features required (e.g., AVX, SSE)
    pub required_features: Vec<String>,
    /// CPU affinity preferences
    pub affinity_preferences: AffinityPreferences,
    /// NUMA awareness requirements
    pub numa_requirements: NumaRequirements,
}

/// Memory resource requirements
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MemoryRequirements {
    /// Minimum memory required in bytes
    pub min_memory_bytes: usize,
    /// Preferred memory size in bytes
    pub preferred_memory_bytes: usize,
    /// Maximum memory that can be utilized in bytes
    pub max_memory_bytes: usize,
    /// Memory type requirements
    pub memory_type: MemoryType,
    /// Memory access pattern
    pub access_pattern: MemoryAccessPattern,
    /// Memory alignment requirements
    pub alignment_requirements: AlignmentRequirements,
    /// Memory locality preferences
    pub locality_preferences: LocalityPreferences,
}

/// GPU resource requirements
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct GpuRequirements {
    /// Number of GPUs required
    pub gpu_count: usize,
    /// Minimum compute capability required
    pub min_compute_capability: (u32, u32),
    /// Minimum GPU memory in bytes
    pub min_gpu_memory_bytes: usize,
    /// GPU architecture preferences
    pub architecture_preferences: Vec<String>,
    /// GPU features required
    pub required_features: Vec<String>,
    /// Multi-GPU coordination requirements
    pub multi_gpu_requirements: MultiGpuRequirements,
}

/// Execution constraints and limitations
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ExecutionConstraint {
    /// Time-based constraints
    TimeConstraint {
        constraint_type: TimeConstraintType,
        time_value: Duration,
        enforcement_level: ConstraintEnforcementLevel,
    },

    /// Resource-based constraints
    ResourceConstraint {
        resource_type: ResourceType,
        constraint_operator: ConstraintOperator,
        threshold_value: f64,
        enforcement_level: ConstraintEnforcementLevel,
    },

    /// Location-based constraints
    LocationConstraint {
        allowed_locations: Vec<String>,
        forbidden_locations: Vec<String>,
        location_preferences: LocationPreferences,
    },

    /// Security-based constraints
    SecurityConstraint {
        security_level: SecurityLevel,
        access_restrictions: Vec<AccessRestriction>,
        encryption_requirements: EncryptionRequirements,
    },

    /// Dependency-based constraints
    DependencyConstraint {
        dependency_type: DependencyType,
        dependency_targets: Vec<TaskId>,
        satisfaction_condition: SatisfactionCondition,
    },

    /// Performance-based constraints
    PerformanceConstraint {
        performance_metric: String,
        constraint_operator: ConstraintOperator,
        target_value: f64,
        measurement_window: Duration,
    },

    /// Custom constraint
    CustomConstraint {
        name: String,
        description: String,
        validation_logic: String,
        parameters: HashMap<String, String>,
    },
}

/// Task dependencies and relationships
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TaskDependencies {
    /// Tasks that must complete before this task can start
    pub prerequisite_tasks: Vec<TaskId>,

    /// Tasks that cannot run concurrently with this task
    pub conflicting_tasks: Vec<TaskId>,

    /// Tasks that should run after this task completes
    pub successor_tasks: Vec<TaskId>,

    /// Resource dependencies
    pub resource_dependencies: Vec<ResourceDependency>,

    /// Data dependencies
    pub data_dependencies: Vec<DataDependency>,

    /// Conditional dependencies
    pub conditional_dependencies: Vec<ConditionalDependency>,

    /// Dependency resolution strategy
    pub resolution_strategy: DependencyResolutionStrategy,
}

/// Task metadata and tracking information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TaskMetadata {
    /// Task creator/owner information
    pub creator: CreatorInfo,

    /// Task category and classification
    pub category: TaskCategory,

    /// Task tags for organization
    pub tags: HashSet<String>,

    /// Task version and revision
    pub version: TaskVersion,

    /// Execution history and statistics
    pub execution_history: ExecutionHistory,

    /// Performance metrics
    pub performance_metrics: PerformanceMetrics,

    /// Quality assurance information
    pub quality_assurance: QualityAssuranceInfo,

    /// Monitoring and observability settings
    pub monitoring_settings: MonitoringSettings,

    /// Custom metadata fields
    pub custom_metadata: HashMap<String, MetadataValue>,
}

/// Task execution location specifications
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ExecutionLocation {
    /// Preferred execution locations
    pub preferred_locations: Vec<LocationSpecification>,

    /// Allowed execution locations
    pub allowed_locations: Vec<LocationSpecification>,

    /// Forbidden execution locations
    pub forbidden_locations: Vec<LocationSpecification>,

    /// Location selection strategy
    pub selection_strategy: LocationSelectionStrategy,

    /// Failover configuration for location unavailability
    pub failover_configuration: LocationFailoverConfig,
}

/// Hardware requirement specification
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HardwareRequirement {
    /// Hardware type and category
    pub hardware_type: HardwareType,

    /// Specific hardware model requirements
    pub model_requirements: Vec<String>,

    /// Hardware capability requirements
    pub capability_requirements: Vec<CapabilityRequirement>,

    /// Performance requirements
    pub performance_requirements: HardwarePerformanceRequirement,

    /// Availability requirements
    pub availability_requirements: AvailabilityRequirement,
}

/// Hardware types for specialized requirements
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum HardwareType {
    /// CPU processing unit
    CPU,
    /// Graphics processing unit
    GPU,
    /// Memory subsystem
    Memory,
    /// Storage subsystem
    Storage,
    /// Network interface
    Network,
    /// Specialized accelerator
    Accelerator,
    /// Field-programmable gate array
    FPGA,
    /// Application-specific integrated circuit
    ASIC,
    /// Quantum processing unit
    QPU,
    /// Custom hardware type
    Custom(String),
}

/// Task failure handling configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FailureHandlingConfig {
    /// Failure detection configuration
    pub detection: FailureDetectionConfig,

    /// Retry configuration for failed tasks
    pub retry: TaskRetryConfig,

    /// Recovery strategies
    pub recovery: FailureRecoveryConfig,

    /// Notification and alerting
    pub notification: FailureNotificationConfig,

    /// Rollback configuration
    pub rollback: RollbackConfig,

    /// Failure analysis and reporting
    pub analysis: FailureAnalysisConfig,
}

/// Task timeout configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TimeoutConfig {
    /// Overall task timeout
    pub overall_timeout: Duration,

    /// Individual operation timeouts
    pub operation_timeouts: HashMap<String, Duration>,

    /// Timeout handling strategy
    pub handling_strategy: TimeoutHandlingStrategy,

    /// Grace period before forced termination
    pub grace_period: Duration,

    /// Escalation configuration
    pub escalation: TimeoutEscalationConfig,
}

/// Custom task parameter
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum TaskParameter {
    /// String parameter
    String(String),
    /// Integer parameter
    Integer(i64),
    /// Floating-point parameter
    Float(f64),
    /// Boolean parameter
    Boolean(bool),
    /// Array of strings
    StringArray(Vec<String>),
    /// Array of integers
    IntegerArray(Vec<i64>),
    /// Array of floats
    FloatArray(Vec<f64>),
    /// Nested parameters
    Nested(HashMap<String, TaskParameter>),
    /// Binary data
    Binary(Vec<u8>),
}

/// Task manager for comprehensive task lifecycle management
#[derive(Debug)]
pub struct TaskManager {
    /// All registered tasks
    tasks: Arc<RwLock<HashMap<TaskId, OptimizationTask>>>,

    /// Task scheduling queue
    scheduling_queue: Arc<Mutex<TaskSchedulingQueue>>,

    /// Active tasks currently being executed
    active_tasks: Arc<RwLock<HashMap<TaskId, ActiveTaskInfo>>>,

    /// Completed tasks archive
    completed_tasks: Arc<RwLock<HashMap<TaskId, CompletedTaskInfo>>>,

    /// Failed tasks archive
    failed_tasks: Arc<RwLock<HashMap<TaskId, FailedTaskInfo>>>,

    /// Task dependency manager
    dependency_manager: Arc<Mutex<TaskDependencyManager>>,

    /// Task metrics collector
    metrics_collector: Arc<Mutex<TaskMetricsCollector>>,

    /// Task priority manager
    priority_manager: Arc<Mutex<TaskPriorityManager>>,

    /// Task resource manager
    resource_manager: Arc<Mutex<TaskResourceManager>>,

    /// Configuration
    config: ExecutionConfig,

    /// Task ID generator
    id_generator: Arc<Mutex<TaskIdGenerator>>,

    /// Statistics and counters
    statistics: Arc<Mutex<TaskManagerStatistics>>,
}

/// Task scheduling queue with advanced prioritization
#[derive(Debug)]
pub struct TaskSchedulingQueue {
    /// High-priority task queue
    high_priority_queue: VecDeque<TaskId>,

    /// Medium-priority task queue
    medium_priority_queue: VecDeque<TaskId>,

    /// Low-priority task queue
    low_priority_queue: VecDeque<TaskId>,

    /// Critical task queue (highest priority)
    critical_queue: VecDeque<TaskId>,

    /// Idle task queue (lowest priority)
    idle_queue: VecDeque<TaskId>,

    /// Deadline-based priority queue
    deadline_queue: BTreeSet<DeadlineTaskEntry>,

    /// Scheduling statistics
    scheduling_stats: SchedulingStatistics,
}

/// Active task information
#[derive(Debug, Clone)]
pub struct ActiveTaskInfo {
    /// Task reference
    pub task: OptimizationTask,

    /// Execution start time
    pub start_time: Instant,

    /// Current execution phase
    pub current_phase: ExecutionPhase,

    /// Resource allocation
    pub allocated_resources: AllocatedResources,

    /// Progress information
    pub progress: TaskProgress,

    /// Real-time metrics
    pub metrics: RealtimeTaskMetrics,
}

/// Completed task information
#[derive(Debug, Clone)]
pub struct CompletedTaskInfo {
    /// Original task
    pub task: OptimizationTask,

    /// Execution summary
    pub execution_summary: ExecutionSummary,

    /// Final results
    pub results: TaskResults,

    /// Performance metrics
    pub performance_metrics: FinalPerformanceMetrics,

    /// Completion timestamp
    pub completion_time: SystemTime,
}

/// Failed task information
#[derive(Debug, Clone)]
pub struct FailedTaskInfo {
    /// Original task
    pub task: OptimizationTask,

    /// Failure information
    pub failure_info: TaskFailureInfo,

    /// Retry history
    pub retry_history: Vec<RetryAttempt>,

    /// Failure analysis
    pub failure_analysis: FailureAnalysis,

    /// Failure timestamp
    pub failure_time: SystemTime,
}

/// Task dependency manager
#[derive(Debug)]
pub struct TaskDependencyManager {
    /// Dependency graph
    dependency_graph: HashMap<TaskId, HashSet<TaskId>>,

    /// Reverse dependency graph
    reverse_dependency_graph: HashMap<TaskId, HashSet<TaskId>>,

    /// Resolved dependencies cache
    resolved_dependencies: HashMap<TaskId, bool>,

    /// Dependency resolution queue
    resolution_queue: VecDeque<TaskId>,
}

impl TaskManager {
    /// Create a new task manager
    pub fn new(config: ExecutionConfig) -> Self {
        Self {
            tasks: Arc::new(RwLock::new(HashMap::new())),
            scheduling_queue: Arc::new(Mutex::new(TaskSchedulingQueue::new())),
            active_tasks: Arc::new(RwLock::new(HashMap::new())),
            completed_tasks: Arc::new(RwLock::new(HashMap::new())),
            failed_tasks: Arc::new(RwLock::new(HashMap::new())),
            dependency_manager: Arc::new(Mutex::new(TaskDependencyManager::new())),
            metrics_collector: Arc::new(Mutex::new(TaskMetricsCollector::new())),
            priority_manager: Arc::new(Mutex::new(TaskPriorityManager::new())),
            resource_manager: Arc::new(Mutex::new(TaskResourceManager::new())),
            config,
            id_generator: Arc::new(Mutex::new(TaskIdGenerator::new())),
            statistics: Arc::new(Mutex::new(TaskManagerStatistics::new())),
        }
    }

    /// Submit a new task for execution
    pub fn submit_task(&self, mut task: OptimizationTask) -> Result<TaskId, TaskError> {
        // Generate task ID if not provided
        if task.id == TaskId(Uuid::nil()) {
            task.id = self.generate_task_id()?;
        }

        // Validate task
        self.validate_task(&task)?;

        // Update task metadata
        task.created_at = SystemTime::now();

        // Store task
        {
            let mut tasks = self.tasks.write().expect("lock should not be poisoned");
            tasks.insert(task.id, task.clone());
        }

        // Add to scheduling queue
        {
            let mut queue = self.scheduling_queue.lock().expect("lock should not be poisoned");
            queue.enqueue_task(task.id, task.priority);
        }

        // Update dependencies
        {
            let mut dep_manager = self.dependency_manager.lock().expect("lock should not be poisoned");
            dep_manager.register_dependencies(&task)?;
        }

        // Update statistics
        {
            let mut stats = self.statistics.lock().expect("lock should not be poisoned");
            stats.tasks_submitted += 1;
        }

        Ok(task.id)
    }

    /// Get the next task to execute
    pub fn get_next_task(&self) -> Option<OptimizationTask> {
        let mut queue = self.scheduling_queue.lock().expect("lock should not be poisoned");
        let task_id = queue.dequeue_next_task()?;

        let tasks = self.tasks.read().expect("lock should not be poisoned");
        tasks.get(&task_id).cloned()
    }

    /// Mark task as started
    pub fn start_task(&self, task_id: TaskId) -> Result<(), TaskError> {
        let task = {
            let tasks = self.tasks.read().expect("lock should not be poisoned");
            tasks
                .get(&task_id)
                .cloned()
                .ok_or(TaskError::TaskNotFound(task_id))?
        };

        let active_info = ActiveTaskInfo {
            task: task.clone(),
            start_time: Instant::now(),
            current_phase: ExecutionPhase::Initializing,
            allocated_resources: AllocatedResources::default(),
            progress: TaskProgress::default(),
            metrics: RealtimeTaskMetrics::default(),
        };

        {
            let mut active_tasks = self.active_tasks.write().expect("lock should not be poisoned");
            active_tasks.insert(task_id, active_info);
        }

        {
            let mut stats = self.statistics.lock().expect("lock should not be poisoned");
            stats.tasks_started += 1;
        }

        Ok(())
    }

    /// Mark task as completed
    pub fn complete_task(&self, task_id: TaskId, results: TaskResults) -> Result<(), TaskError> {
        let active_info = {
            let mut active_tasks = self.active_tasks.write().expect("lock should not be poisoned");
            active_tasks
                .remove(&task_id)
                .ok_or(TaskError::TaskNotActive(task_id))?
        };

        let execution_duration = active_info.start_time.elapsed();
        let completion_info = CompletedTaskInfo {
            task: active_info.task,
            execution_summary: ExecutionSummary {
                execution_duration,
                phases_completed: vec![], // Would be populated with actual phase info
                resource_utilization: ResourceUtilization::default(),
            },
            results,
            performance_metrics: FinalPerformanceMetrics::default(),
            completion_time: SystemTime::now(),
        };

        {
            let mut completed_tasks = self.completed_tasks.write().expect("lock should not be poisoned");
            completed_tasks.insert(task_id, completion_info);
        }

        {
            let mut stats = self.statistics.lock().expect("lock should not be poisoned");
            stats.tasks_completed += 1;
        }

        // Update dependency resolution
        {
            let mut dep_manager = self.dependency_manager.lock().expect("lock should not be poisoned");
            dep_manager.mark_task_completed(task_id);
        }

        Ok(())
    }

    /// Mark task as failed
    pub fn fail_task(
        &self,
        task_id: TaskId,
        failure_info: TaskFailureInfo,
    ) -> Result<(), TaskError> {
        let active_info = {
            let mut active_tasks = self.active_tasks.write().expect("lock should not be poisoned");
            active_tasks
                .remove(&task_id)
                .ok_or(TaskError::TaskNotActive(task_id))?
        };

        let failed_info = FailedTaskInfo {
            task: active_info.task,
            failure_info,
            retry_history: vec![],
            failure_analysis: FailureAnalysis::default(),
            failure_time: SystemTime::now(),
        };

        {
            let mut failed_tasks = self.failed_tasks.write().expect("lock should not be poisoned");
            failed_tasks.insert(task_id, failed_info);
        }

        {
            let mut stats = self.statistics.lock().expect("lock should not be poisoned");
            stats.tasks_failed += 1;
        }

        Ok(())
    }

    /// Get task by ID
    pub fn get_task(&self, task_id: TaskId) -> Option<OptimizationTask> {
        let tasks = self.tasks.read().expect("lock should not be poisoned");
        tasks.get(&task_id).cloned()
    }

    /// Get active tasks
    pub fn get_active_tasks(&self) -> Vec<ActiveTaskInfo> {
        let active_tasks = self.active_tasks.read().expect("lock should not be poisoned");
        active_tasks.values().cloned().collect()
    }

    /// Get task statistics
    pub fn get_statistics(&self) -> TaskManagerStatistics {
        let stats = self.statistics.lock().expect("lock should not be poisoned");
        stats.clone()
    }

    /// Generate a new task ID
    fn generate_task_id(&self) -> Result<TaskId, TaskError> {
        let mut generator = self.id_generator.lock().expect("lock should not be poisoned");
        Ok(generator.generate())
    }

    /// Validate a task before submission
    fn validate_task(&self, task: &OptimizationTask) -> Result<(), TaskError> {
        // Validate task name
        if task.name.is_empty() {
            return Err(TaskError::InvalidTask(
                "Task name cannot be empty".to_string(),
            ));
        }

        // Validate resource requirements
        if task
            .resource_requirements
            .memory_requirements
            .min_memory_bytes
            == 0
        {
            return Err(TaskError::InvalidTask(
                "Memory requirements must be specified".to_string(),
            ));
        }

        // Validate success criteria
        for criterion in &task.success_criteria {
            if criterion.weight < 0.0 || criterion.weight > 1.0 {
                return Err(TaskError::InvalidTask(
                    "Success criterion weight must be between 0.0 and 1.0".to_string(),
                ));
            }
        }

        Ok(())
    }
}

impl TaskSchedulingQueue {
    fn new() -> Self {
        Self {
            high_priority_queue: VecDeque::new(),
            medium_priority_queue: VecDeque::new(),
            low_priority_queue: VecDeque::new(),
            critical_queue: VecDeque::new(),
            idle_queue: VecDeque::new(),
            deadline_queue: BTreeSet::new(),
            scheduling_stats: SchedulingStatistics::default(),
        }
    }

    fn enqueue_task(&mut self, task_id: TaskId, priority: TaskPriority) {
        match priority {
            TaskPriority::Critical => self.critical_queue.push_back(task_id),
            TaskPriority::High => self.high_priority_queue.push_back(task_id),
            TaskPriority::Medium => self.medium_priority_queue.push_back(task_id),
            TaskPriority::Low => self.low_priority_queue.push_back(task_id),
            TaskPriority::Idle => self.idle_queue.push_back(task_id),
        }

        self.scheduling_stats.tasks_enqueued += 1;
    }

    fn dequeue_next_task(&mut self) -> Option<TaskId> {
        // Check critical queue first
        if let Some(task_id) = self.critical_queue.pop_front() {
            self.scheduling_stats.tasks_dequeued += 1;
            return Some(task_id);
        }

        // Check deadline queue for urgent tasks
        if let Some(deadline_entry) = self.deadline_queue.iter().next() {
            let now = SystemTime::now();
            if deadline_entry.deadline <= now {
                let task_id = deadline_entry.task_id;
                self.deadline_queue.remove(&deadline_entry.clone());
                self.scheduling_stats.tasks_dequeued += 1;
                return Some(task_id);
            }
        }

        // Check other priority queues
        if let Some(task_id) = self.high_priority_queue.pop_front() {
            self.scheduling_stats.tasks_dequeued += 1;
            return Some(task_id);
        }

        if let Some(task_id) = self.medium_priority_queue.pop_front() {
            self.scheduling_stats.tasks_dequeued += 1;
            return Some(task_id);
        }

        if let Some(task_id) = self.low_priority_queue.pop_front() {
            self.scheduling_stats.tasks_dequeued += 1;
            return Some(task_id);
        }

        if let Some(task_id) = self.idle_queue.pop_front() {
            self.scheduling_stats.tasks_dequeued += 1;
            return Some(task_id);
        }

        None
    }
}

impl TaskDependencyManager {
    fn new() -> Self {
        Self {
            dependency_graph: HashMap::new(),
            reverse_dependency_graph: HashMap::new(),
            resolved_dependencies: HashMap::new(),
            resolution_queue: VecDeque::new(),
        }
    }

    fn register_dependencies(&mut self, task: &OptimizationTask) -> Result<(), TaskError> {
        for &dep_id in &task.dependencies.prerequisite_tasks {
            self.dependency_graph
                .entry(task.id)
                .or_insert_with(HashSet::new)
                .insert(dep_id);

            self.reverse_dependency_graph
                .entry(dep_id)
                .or_insert_with(HashSet::new)
                .insert(task.id);
        }

        Ok(())
    }

    fn mark_task_completed(&mut self, task_id: TaskId) {
        self.resolved_dependencies.insert(task_id, true);

        // Check if any dependent tasks can now be resolved
        if let Some(dependents) = self.reverse_dependency_graph.get(&task_id) {
            for &dependent_id in dependents {
                self.check_dependencies_resolved(dependent_id);
            }
        }
    }

    fn check_dependencies_resolved(&mut self, task_id: TaskId) -> bool {
        if let Some(dependencies) = self.dependency_graph.get(&task_id) {
            for &dep_id in dependencies {
                if !self.resolved_dependencies.get(&dep_id).unwrap_or(&false) {
                    return false;
                }
            }
        }

        self.resolved_dependencies.insert(task_id, true);
        self.resolution_queue.push_back(task_id);
        true
    }
}

/// Task ID generator
#[derive(Debug)]
pub struct TaskIdGenerator {
    counter: AtomicU64,
}

impl TaskIdGenerator {
    fn new() -> Self {
        Self {
            counter: AtomicU64::new(0),
        }
    }

    fn generate(&self) -> TaskId {
        TaskId(Uuid::new_v4())
    }
}

/// Task error types
#[derive(Debug, Clone)]
pub enum TaskError {
    /// Task not found
    TaskNotFound(TaskId),
    /// Task is not currently active
    TaskNotActive(TaskId),
    /// Invalid task configuration
    InvalidTask(String),
    /// Dependency resolution failed
    DependencyResolutionFailed(String),
    /// Resource allocation failed
    ResourceAllocationFailed(String),
    /// Task execution failed
    ExecutionFailed(String),
}

// === Placeholder Types (Implementation Details) ===

// These would be fully implemented in their respective modules or as part of detailed implementation

macro_rules! default_placeholder_struct {
    ($name:ident) => {
        #[derive(Debug, Clone, Default, Serialize, Deserialize)]
        pub struct $name {
            pub placeholder: bool,
        }
    };
}

default_placeholder_struct!(AllocationPattern);
default_placeholder_struct!(AllocationConstraint);
default_placeholder_struct!(CleanupLevel);
default_placeholder_struct!(CompactionStrategy);
default_placeholder_struct!(CacheLevel);
default_placeholder_struct!(CacheOptimizationTarget);
default_placeholder_struct!(BandwidthScope);
default_placeholder_struct!(LatencyType);
default_placeholder_struct!(PoolOperation);
default_placeholder_struct!(PoolParameters);
default_placeholder_struct!(BalancingTarget);
default_placeholder_struct!(BalancingStrategy);
default_placeholder_struct!(MonitoringScope);
default_placeholder_struct!(MetricsCollection);
default_placeholder_struct!(DiagnosticLevel);
default_placeholder_struct!(DiagnosticScope);
default_placeholder_struct!(PluginInfo);
default_placeholder_struct!(ScriptInfo);
default_placeholder_struct!(MLModelInfo);
default_placeholder_struct!(CustomImplementationInfo);
default_placeholder_struct!(CombinationLogic);
default_placeholder_struct!(SafetyConstraint);
default_placeholder_struct!(PerformanceConstraint);
default_placeholder_struct!(ValidationRequirements);
default_placeholder_struct!(StorageRequirements);
default_placeholder_struct!(NetworkRequirements);
default_placeholder_struct!(AllocationPreferences);
default_placeholder_struct!(SharingConfiguration);
default_placeholder_struct!(AffinityPreferences);
default_placeholder_struct!(NumaRequirements);
default_placeholder_struct!(MemoryType);
default_placeholder_struct!(MemoryAccessPattern);
default_placeholder_struct!(AlignmentRequirements);
default_placeholder_struct!(LocalityPreferences);
default_placeholder_struct!(MultiGpuRequirements);
default_placeholder_struct!(LocationPreferences);
default_placeholder_struct!(SecurityLevel);
default_placeholder_struct!(AccessRestriction);
default_placeholder_struct!(EncryptionRequirements);
default_placeholder_struct!(DependencyType);
default_placeholder_struct!(SatisfactionCondition);
default_placeholder_struct!(ResourceDependency);
default_placeholder_struct!(DataDependency);
default_placeholder_struct!(ConditionalDependency);
default_placeholder_struct!(DependencyResolutionStrategy);
default_placeholder_struct!(CreatorInfo);
default_placeholder_struct!(TaskCategory);
default_placeholder_struct!(TaskVersion);
default_placeholder_struct!(ExecutionHistory);
default_placeholder_struct!(PerformanceMetrics);
default_placeholder_struct!(QualityAssuranceInfo);
default_placeholder_struct!(MonitoringSettings);
default_placeholder_struct!(LocationSpecification);
default_placeholder_struct!(LocationSelectionStrategy);
default_placeholder_struct!(LocationFailoverConfig);
default_placeholder_struct!(CapabilityRequirement);
default_placeholder_struct!(HardwarePerformanceRequirement);
default_placeholder_struct!(AvailabilityRequirement);
default_placeholder_struct!(FailureDetectionConfig);
default_placeholder_struct!(TaskRetryConfig);
default_placeholder_struct!(FailureRecoveryConfig);
default_placeholder_struct!(FailureNotificationConfig);
default_placeholder_struct!(RollbackConfig);
default_placeholder_struct!(FailureAnalysisConfig);
default_placeholder_struct!(TimeoutHandlingStrategy);
default_placeholder_struct!(TimeoutEscalationConfig);
default_placeholder_struct!(TaskMetricsCollector);
default_placeholder_struct!(TaskPriorityManager);
default_placeholder_struct!(TaskResourceManager);
default_placeholder_struct!(TaskManagerStatistics);
/// Entry for deadline-based task tracking
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DeadlineTaskEntry {
    /// Task identifier
    pub task_id: TaskId,
    /// Task deadline
    #[serde(skip, default = "default_instant")]
    pub deadline: std::time::Instant,
    /// Priority for tie-breaking
    pub priority: u32,
}
/// Scheduling statistics for task management
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct SchedulingStatistics {
    /// Total tasks scheduled
    pub total_scheduled: u64,
    /// Total tasks dequeued
    pub tasks_dequeued: u64,
    /// Successful executions
    pub successful: u64,
    /// Failed executions
    pub failed: u64,
}
default_placeholder_struct!(ExecutionPhase);
default_placeholder_struct!(AllocatedResources);
default_placeholder_struct!(TaskProgress);
default_placeholder_struct!(RealtimeTaskMetrics);
default_placeholder_struct!(ExecutionSummary);
default_placeholder_struct!(TaskResults);
default_placeholder_struct!(FinalPerformanceMetrics);
default_placeholder_struct!(TaskFailureInfo);
default_placeholder_struct!(RetryAttempt);
default_placeholder_struct!(FailureAnalysis);
default_placeholder_struct!(ResourceUtilization);

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum StrategyParameter {
    String(String),
    Integer(i64),
    Float(f64),
    Boolean(bool),
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum MetadataValue {
    String(String),
    Integer(i64),
    Float(f64),
    Boolean(bool),
    Array(Vec<MetadataValue>),
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum TimeConstraintType {
    MaxExecutionTime,
    Deadline,
    StartTime,
    EndTime,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum ResourceType {
    CPU,
    Memory,
    GPU,
    Storage,
    Network,
    Custom(u32),
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum ConstraintOperator {
    LessThan,
    LessThanOrEqual,
    Equal,
    GreaterThanOrEqual,
    GreaterThan,
    NotEqual,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum ConstraintEnforcementLevel {
    Advisory,
    Warning,
    Strict,
    Critical,
}

// Implement necessary traits
impl TaskId {
    pub fn new() -> Self {
        Self(Uuid::new_v4())
    }

    pub fn nil() -> Self {
        Self(Uuid::nil())
    }
}

impl Default for TaskId {
    fn default() -> Self {
        Self::nil()
    }
}

impl std::fmt::Display for TaskId {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl PartialEq for DeadlineTaskEntry {
    fn eq(&self, other: &Self) -> bool {
        self.task_id == other.task_id
    }
}

impl Eq for DeadlineTaskEntry {}

impl std::cmp::Ord for DeadlineTaskEntry {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        self.deadline
            .cmp(&other.deadline)
            .then_with(|| self.task_id.0.cmp(&other.task_id.0))
    }
}

impl std::cmp::PartialOrd for DeadlineTaskEntry {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}

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

    #[test]
    fn test_task_id_generation() {
        let id1 = TaskId::new();
        let id2 = TaskId::new();
        assert_ne!(id1, id2);
    }

    #[test]
    fn test_task_priority_ordering() {
        assert!(TaskPriority::Critical < TaskPriority::High);
        assert!(TaskPriority::High < TaskPriority::Medium);
        assert!(TaskPriority::Medium < TaskPriority::Low);
        assert!(TaskPriority::Low < TaskPriority::Idle);
    }

    #[test]
    fn test_task_manager_creation() {
        let config = ExecutionConfig::default();
        let task_manager = TaskManager::new(config);
        let stats = task_manager.get_statistics();
        assert_eq!(stats.tasks_submitted, 0);
    }

    #[test]
    fn test_task_submission() {
        let config = ExecutionConfig::default();
        let task_manager = TaskManager::new(config);

        let task = OptimizationTask {
            id: TaskId::new(),
            name: "Test Task".to_string(),
            description: "A test optimization task".to_string(),
            task_type: OptimizationTaskType::MemoryAllocation {
                allocation_size: 1024,
                pattern: AllocationPattern::default(),
                constraints: vec![],
            },
            priority: TaskPriority::Medium,
            strategy: OptimizationStrategy {
                name: "test_strategy".to_string(),
                implementation: StrategyImplementation::Builtin("test".to_string()),
                parameters: HashMap::new(),
                composition: None,
                constraints: vec![],
                safety_level: SafetyLevel::Standard,
                expected_improvement: 0.1,
                validation_requirements: ValidationRequirements::default(),
            },
            resource_requirements: ResourceRequirements {
                cpu_requirements: CpuRequirements {
                    min_cores: 1,
                    preferred_cores: 2,
                    max_cores: 4,
                    architecture_requirements: vec![],
                    min_frequency_ghz: 2.0,
                    required_features: vec![],
                    affinity_preferences: AffinityPreferences::default(),
                    numa_requirements: NumaRequirements::default(),
                },
                memory_requirements: MemoryRequirements {
                    min_memory_bytes: 1024 * 1024,
                    preferred_memory_bytes: 2 * 1024 * 1024,
                    max_memory_bytes: 4 * 1024 * 1024,
                    memory_type: MemoryType::default(),
                    access_pattern: MemoryAccessPattern::default(),
                    alignment_requirements: AlignmentRequirements::default(),
                    locality_preferences: LocalityPreferences::default(),
                },
                gpu_requirements: GpuRequirements {
                    gpu_count: 0,
                    min_compute_capability: (3, 5),
                    min_gpu_memory_bytes: 0,
                    architecture_preferences: vec![],
                    required_features: vec![],
                    multi_gpu_requirements: MultiGpuRequirements::default(),
                },
                storage_requirements: StorageRequirements::default(),
                network_requirements: NetworkRequirements::default(),
                hardware_requirements: vec![],
                allocation_preferences: AllocationPreferences::default(),
                sharing_configuration: SharingConfiguration::default(),
            },
            constraints: vec![],
            dependencies: TaskDependencies {
                prerequisite_tasks: vec![],
                conflicting_tasks: vec![],
                successor_tasks: vec![],
                resource_dependencies: vec![],
                data_dependencies: vec![],
                conditional_dependencies: vec![],
                resolution_strategy: DependencyResolutionStrategy::default(),
            },
            metadata: TaskMetadata {
                creator: CreatorInfo::default(),
                category: TaskCategory::default(),
                tags: HashSet::new(),
                version: TaskVersion::default(),
                execution_history: ExecutionHistory::default(),
                performance_metrics: PerformanceMetrics::default(),
                quality_assurance: QualityAssuranceInfo::default(),
                monitoring_settings: MonitoringSettings::default(),
                custom_metadata: HashMap::new(),
            },
            success_criteria: vec![],
            failure_handling: FailureHandlingConfig {
                detection: FailureDetectionConfig::default(),
                retry: TaskRetryConfig::default(),
                recovery: FailureRecoveryConfig::default(),
                notification: FailureNotificationConfig::default(),
                rollback: RollbackConfig::default(),
                analysis: FailureAnalysisConfig::default(),
            },
            execution_location: ExecutionLocation {
                preferred_locations: vec![],
                allowed_locations: vec![],
                forbidden_locations: vec![],
                selection_strategy: LocationSelectionStrategy::default(),
                failover_configuration: LocationFailoverConfig::default(),
            },
            timeout_config: TimeoutConfig {
                overall_timeout: Duration::from_secs(300),
                operation_timeouts: HashMap::new(),
                handling_strategy: TimeoutHandlingStrategy::default(),
                grace_period: Duration::from_secs(30),
                escalation: TimeoutEscalationConfig::default(),
            },
            custom_parameters: HashMap::new(),
            created_at: SystemTime::now(),
            deadline: None,
            estimated_duration: Some(Duration::from_secs(60)),
        };

        let task_id = task_manager.submit_task(task).unwrap();
        let stats = task_manager.get_statistics();
        assert_eq!(stats.tasks_submitted, 1);

        let retrieved_task = task_manager.get_task(task_id).unwrap();
        assert_eq!(retrieved_task.name, "Test Task");
    }

    #[test]
    fn test_task_scheduling_queue() {
        let mut queue = TaskSchedulingQueue::new();

        let critical_task = TaskId::new();
        let high_task = TaskId::new();
        let medium_task = TaskId::new();

        queue.enqueue_task(medium_task, TaskPriority::Medium);
        queue.enqueue_task(critical_task, TaskPriority::Critical);
        queue.enqueue_task(high_task, TaskPriority::High);

        // Critical task should be dequeued first
        assert_eq!(queue.dequeue_next_task(), Some(critical_task));
        // High priority task should be next
        assert_eq!(queue.dequeue_next_task(), Some(high_task));
        // Medium priority task should be last
        assert_eq!(queue.dequeue_next_task(), Some(medium_task));
    }
}
