optirs-tpu 0.3.1

use std::fmt::Debug;
// TPU Backend Implementation
//
// This module provides the core TPU backend implementation for executing
// optimized computations on Google Cloud TPUs and compatible hardware.

#[allow(dead_code)]
use scirs2_core::numeric::Float;
use std::collections::{HashMap, VecDeque};
use std::sync::{Arc, RwLock};
use std::time::{Duration, Instant};

use super::xla_compilation::ComputationId;
use super::{TPUConfig, TPUVersion, XLAOptimizationLevel};
use crate::error::Result;

/// TPU Backend Manager
pub struct TPUBackend<T: Float + Debug + Send + Sync + 'static> {
    /// Backend configuration
    config: TPUBackendConfig,

    /// Device manager
    device_manager: DeviceManager,

    /// Execution engine
    execution_engine: ExecutionEngine<T>,

    /// Memory manager
    memory_manager: TPUMemoryManager<T>,

    /// Runtime profiler
    runtime_profiler: RuntimeProfiler,

    /// Error handler
    error_handler: TPUErrorHandler,

    /// Performance monitor
    performance_monitor: PerformanceMonitor,

    /// Compilation cache
    compilation_cache: Arc<RwLock<HashMap<ComputationId, CompiledProgram>>>,
}

/// TPU backend configuration
#[derive(Debug, Clone)]
pub struct TPUBackendConfig {
    /// Target TPU configuration
    pub tpu_config: TPUConfig,

    /// Enable runtime optimization
    pub runtime_optimization: bool,

    /// Enable automatic memory management
    pub auto_memory_management: bool,

    /// Execution timeout (milliseconds)
    pub execution_timeout_ms: u64,

    /// Enable performance monitoring
    pub enable_performance_monitoring: bool,

    /// Buffer size for async execution
    pub async_buffer_size: usize,

    /// Enable error recovery
    pub enable_error_recovery: bool,

    /// Maximum retry attempts
    pub max_retry_attempts: usize,

    /// Prefetch strategy
    pub prefetch_strategy: PrefetchStrategy,

    /// Memory allocation strategy
    pub memory_allocation_strategy: MemoryAllocationStrategy,
}

/// Device manager for TPU hardware
#[derive(Debug)]
pub struct DeviceManager {
    /// Available TPU devices
    devices: Vec<TPUDevice>,

    /// Device assignments
    device_assignments: HashMap<ComputationId, Vec<DeviceId>>,

    /// Device health status
    device_health: HashMap<DeviceId, DeviceHealthStatus>,

    /// Device utilization
    device_utilization: HashMap<DeviceId, f64>,

    /// Device topology
    topology: DeviceTopology,

    /// Load balancer
    load_balancer: LoadBalancer,
}

/// TPU device representation
#[derive(Debug, Clone)]
pub struct TPUDevice {
    /// Device ID
    pub id: DeviceId,

    /// Device type
    pub device_type: TPUVersion,

    /// Memory capacity (bytes)
    pub memory_capacity: usize,

    /// Compute capability
    pub compute_capability: ComputeCapability,

    /// Device status
    pub status: DeviceStatus,

    /// Interconnect links
    pub interconnect_links: Vec<InterconnectLink>,

    /// Device coordinates in pod
    pub coordinates: Option<(usize, usize)>,

    /// Performance characteristics
    pub performance_characteristics: DevicePerformanceCharacteristics,
}

/// Unique device identifier
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct DeviceId(pub usize);

/// Device status
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum DeviceStatus {
    Available,
    Busy,
    Error,
    Maintenance,
    Offline,
}

/// Device health status
#[derive(Debug, Clone)]
pub struct DeviceHealthStatus {
    /// Overall health score (0.0 to 1.0)
    pub health_score: f64,

    /// Temperature (Celsius)
    pub temperature: f64,

    /// Power consumption (Watts)
    pub power_consumption: f64,

    /// Memory health
    pub memory_health: MemoryHealthStatus,

    /// Compute unit health
    pub compute_health: ComputeHealthStatus,

    /// Last health check
    pub last_check: Instant,
}

/// Memory health status
#[derive(Debug, Clone)]
pub struct MemoryHealthStatus {
    /// Memory errors detected
    pub error_count: usize,

    /// Memory bandwidth efficiency
    pub bandwidth_efficiency: f64,

    /// Memory fragmentation ratio
    pub fragmentation_ratio: f64,
}

/// Compute unit health status
#[derive(Debug, Clone)]
pub struct ComputeHealthStatus {
    /// Matrix unit efficiency
    pub matrix_unit_efficiency: f64,

    /// Vector unit efficiency
    pub vector_unit_efficiency: f64,

    /// Scalar unit efficiency
    pub scalar_unit_efficiency: f64,

    /// Instruction cache hit rate
    pub instruction_cache_hit_rate: f64,
}

/// Compute capability description
#[derive(Debug, Clone)]
pub struct ComputeCapability {
    /// Peak FLOPS (operations per second)
    pub peak_flops: u64,

    /// Matrix multiplication FLOPS
    pub matrix_flops: u64,

    /// Memory bandwidth (GB/s)
    pub memory_bandwidth_gb_s: f64,

    /// Supported data types
    pub supported_dtypes: Vec<DataType>,

    /// Maximum dimensions
    pub max_dimensions: usize,

    /// Special features
    pub features: Vec<TPUFeature>,
}

/// Supported data types
#[derive(Debug, Clone, Copy)]
pub enum DataType {
    F16,
    F32,
    BF16,
    I8,
    I16,
    I32,
    U8,
    U16,
    U32,
    Bool,
}

/// TPU-specific features
#[derive(Debug, Clone)]
pub enum TPUFeature {
    MatrixUnits,
    VectorUnits,
    HighBandwidthMemory,
    MixedPrecision,
    SparsitySupport,
    TransformerOptimizations,
    ConvolutionOptimizations,
}

/// Device performance characteristics
#[derive(Debug, Clone)]
pub struct DevicePerformanceCharacteristics {
    /// Effective memory bandwidth
    pub effective_memory_bandwidth: f64,

    /// Compute utilization efficiency
    pub compute_efficiency: f64,

    /// Communication latency (microseconds)
    pub communication_latency_us: f64,

    /// Thermal throttling threshold
    pub thermal_threshold: f64,
}

/// Interconnect link between devices
#[derive(Debug, Clone)]
pub struct InterconnectLink {
    /// Target device
    pub target_device: DeviceId,

    /// Link bandwidth (GB/s)
    pub bandwidth_gb_s: f64,

    /// Link latency (microseconds)
    pub latency_us: f64,

    /// Link type
    pub link_type: InterconnectType,

    /// Link status
    pub status: LinkStatus,
}

/// Types of interconnect
#[derive(Debug, Clone, Copy)]
pub enum InterconnectType {
    IntraChip,
    InterChip,
    InterNode,
    HighSpeed,
    LowLatency,
}

/// Link status
#[derive(Debug, Clone, Copy)]
pub enum LinkStatus {
    Active,
    Inactive,
    Error,
    Degraded,
}

/// Topology types
#[derive(Debug, Clone, Copy)]
pub enum TopologyType {
    Linear,
    Ring,
    Mesh2D,
    Mesh3D,
    Torus,
    Tree,
    HyperCube,
    Custom,
}

/// Load balancing strategies
#[derive(Debug, Clone, Copy, Default)]
pub enum LoadBalancingStrategy {
    #[default]
    RoundRobin,
    LeastLoaded,
    PowerAware,
    LocalityAware,
    Adaptive,
    WorkStealing,
}

/// Load sample for monitoring
#[derive(Debug, Clone)]
pub struct LoadSample {
    /// Timestamp
    pub timestamp: Instant,

    /// Utilization (0.0 to 1.0)
    pub utilization: f64,

    /// Memory usage (0.0 to 1.0)
    pub memory_usage: f64,

    /// Temperature
    pub temperature: f64,
}

/// Assignment statistics
#[derive(Debug, Clone)]
pub struct AssignmentStatistics {
    /// Total assignments
    pub total_assignments: usize,

    /// Average assignment time
    pub avg_assignment_time: Duration,

    /// Load balance efficiency
    pub load_balance_efficiency: f64,

    /// Device utilization variance
    pub utilization_variance: f64,
}

/// Runtime executor for TPU operations
#[derive(Debug)]
pub struct RuntimeExecutor<T: Float + Debug + Send + Sync + 'static> {
    /// Execution state
    state: T,
}

/// Result collector for TPU computations
#[derive(Debug)]
pub struct ResultCollector<T: Float + Debug + Send + Sync + 'static> {
    /// Collected results
    results: Vec<T>,
}

/// Execution context for TPU operations
#[derive(Debug)]
pub struct ExecutionContext {
    /// Context id
    id: usize,
}

/// Performance optimizer for TPU operations
#[derive(Debug)]
pub struct PerformanceOptimizer<T: Float + Debug + Send + Sync + 'static> {
    /// Optimization level
    level: T,
}

/// Priority manager for TPU task scheduling
#[derive(Debug)]
pub struct PriorityManager {
    /// Priority level
    level: usize,
}

/// Dependency resolver for TPU operations
#[derive(Debug)]
pub struct DependencyResolver {
    /// Resolved dependencies
    dependencies: Vec<String>,
}

/// Execution engine for TPU computations
#[derive(Debug)]
pub struct ExecutionEngine<T: Float + Debug + Send + Sync + 'static> {
    /// Execution scheduler
    scheduler: ExecutionScheduler<T>,

    /// Runtime executor
    executor: RuntimeExecutor<T>,

    /// Result collector
    result_collector: ResultCollector<T>,

    /// Execution context
    context: ExecutionContext,

    /// Performance optimizer
    performance_optimizer: PerformanceOptimizer<T>,
}

/// Execution scheduler
#[derive(Debug)]
pub struct ExecutionScheduler<T: Float + Debug + Send + Sync + 'static> {
    /// Execution queue
    execution_queue: VecDeque<ExecutionTask<T>>,

    /// Scheduling policy
    scheduling_policy: SchedulingPolicy,

    /// Priority manager
    priority_manager: PriorityManager,

    /// Dependency resolver
    dependency_resolver: DependencyResolver,
}

/// Execution task
#[derive(Debug)]
pub struct ExecutionTask<T: Float + Debug + Send + Sync + 'static> {
    /// Task ID
    pub id: TaskId,

    /// Computation to execute
    pub computation: ComputationId,

    /// Input data
    pub inputs: Vec<TPUBuffer<T>>,

    /// Expected outputs
    pub expected_outputs: Vec<OutputSpec<T>>,

    /// Execution priority
    pub priority: TaskPriority,

    /// Task dependencies
    pub dependencies: Vec<TaskId>,

    /// Execution constraints
    pub constraints: ExecutionConstraints,

    /// Timeout
    pub timeout: Duration,
}

/// Unique task identifier
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct TaskId(pub u64);

/// Task priority levels
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub enum TaskPriority {
    Low,
    Normal,
    High,
    Critical,
    Realtime,
}

/// Execution constraints
#[derive(Debug, Clone)]
pub struct ExecutionConstraints {
    /// Required device features
    pub required_features: Vec<TPUFeature>,

    /// Memory constraints
    pub memory_constraints: MemoryConstraints,

    /// Performance constraints
    pub performance_constraints: PerformanceConstraints,

    /// Locality constraints
    pub locality_constraints: LocalityConstraints,
}

/// Memory constraints
#[derive(Debug, Clone)]
pub struct MemoryConstraints {
    /// Maximum memory usage
    pub max_memory_usage: usize,

    /// Memory bandwidth requirement
    pub min_bandwidth_gb_s: f64,

    /// Memory layout preferences
    pub layout_preferences: Vec<MemoryLayout>,
}

/// Performance constraints
#[derive(Debug, Clone)]
pub struct PerformanceConstraints {
    /// Maximum execution time
    pub max_execution_time: Duration,

    /// Minimum throughput
    pub min_throughput: f64,

    /// Maximum latency
    pub max_latency: Duration,

    /// Power constraints
    pub power_budget: Option<f64>,
}

/// Locality constraints
#[derive(Debug, Clone)]
pub struct LocalityConstraints {
    /// Preferred devices
    pub preferred_devices: Vec<DeviceId>,

    /// Avoid devices
    pub avoid_devices: Vec<DeviceId>,

    /// Locality scope
    pub locality_scope: LocalityScope,
}

/// Locality scope
#[derive(Debug, Clone, Copy)]
pub enum LocalityScope {
    Device,
    Chip,
    Node,
    Pod,
    Global,
}

/// Memory layout types
#[derive(Debug, Clone, Copy)]
pub enum MemoryLayout {
    RowMajor,
    ColumnMajor,
    Blocked,
    Tiled,
    Sparse,
    Custom,
}

/// Scheduling policies
#[derive(Debug, Clone, Copy)]
pub enum SchedulingPolicy {
    FIFO,
    Priority,
    ShortestJobFirst,
    RoundRobin,
    FairShare,
    Adaptive,
}

/// TPU buffer for data
#[derive(Debug)]
pub struct TPUBuffer<T: Float + Debug + Send + Sync + 'static> {
    /// Buffer data
    data: Vec<T>,

    /// Buffer shape
    shape: Vec<usize>,

    /// Memory layout
    layout: MemoryLayout,

    /// Device location
    device: Option<DeviceId>,

    /// Buffer metadata
    metadata: BufferMetadata,
}

/// Buffer metadata
#[derive(Debug, Clone)]
pub struct BufferMetadata {
    /// Creation timestamp
    pub created_at: Instant,

    /// Last access timestamp
    pub last_accessed: Instant,

    /// Access count
    pub access_count: usize,

    /// Data type
    pub data_type: DataType,

    /// Buffer flags
    pub flags: BufferFlags,
}

/// Buffer flags
#[derive(Debug, Clone)]
pub struct BufferFlags {
    /// Read-only buffer
    pub read_only: bool,

    /// Persistent buffer
    pub persistent: bool,

    /// Prefetch hint
    pub prefetch: bool,

    /// Memory pinned
    pub pinned: bool,
}

/// Output specification
#[derive(Debug, Clone)]
pub struct OutputSpec<T: Float + Debug + Send + Sync + 'static> {
    /// Expected shape
    pub shape: Vec<usize>,

    /// Data type
    pub data_type: DataType,

    /// Memory layout
    pub layout: MemoryLayout,

    /// Phantom data
    _phantom: std::marker::PhantomData<T>,
}

/// Compiled program for TPU execution
#[derive(Debug, Clone)]
pub struct CompiledProgram {
    /// Program binary
    pub binary: Vec<u8>,

    /// Program metadata
    pub metadata: ProgramMetadata,

    /// Memory requirements
    pub memory_requirements: ProgramMemoryRequirements,

    /// Performance characteristics
    pub performance_characteristics: ProgramPerformanceCharacteristics,
}

/// Program metadata
#[derive(Debug, Clone)]
pub struct ProgramMetadata {
    /// Compilation timestamp
    pub compiled_at: Instant,

    /// Compiler version
    pub compiler_version: String,

    /// Optimization level
    pub optimization_level: XLAOptimizationLevel,

    /// Target architecture
    pub target_architecture: TPUVersion,

    /// Program size
    pub program_size: usize,

    /// Output specifications
    pub output_specs: Vec<String>,
}

/// Program memory requirements
#[derive(Debug, Clone)]
pub struct ProgramMemoryRequirements {
    /// Code memory
    pub code_memory: usize,

    /// Data memory
    pub data_memory: usize,

    /// Stack memory
    pub stack_memory: usize,

    /// Scratch memory
    pub scratch_memory: usize,

    /// Total memory
    pub total_memory: usize,
}

/// Program performance characteristics
#[derive(Debug, Clone)]
pub struct ProgramPerformanceCharacteristics {
    /// Estimated execution time
    pub estimated_execution_time: Duration,

    /// Estimated FLOPS
    pub estimated_flops: u64,

    /// Memory bandwidth utilization
    pub memory_bandwidth_utilization: f64,

    /// Compute utilization
    pub compute_utilization: f64,
}

/// Prefetch strategies
#[derive(Debug, Clone, Copy)]
pub enum PrefetchStrategy {
    None,
    Sequential,
    Adaptive,
    Predictive,
    UserHint,
}

/// Memory allocation strategies
#[derive(Debug, Clone, Copy)]
pub enum MemoryAllocationStrategy {
    FirstFit,
    BestFit,
    WorstFit,
    BuddySystem,
    PoolBased,
    Adaptive,
}

/// Memory allocation tracking
#[derive(Debug, Clone)]
pub struct MemoryAllocation {
    /// Per-device allocations
    pub device_allocations: HashMap<DeviceId, usize>,

    /// Total allocated memory
    pub total_allocated: usize,
}

/// Computation task for execution
#[derive(Debug, Clone)]
pub struct ComputationTask {
    /// Task identifier
    pub task_id: TaskId,

    /// Computation to execute
    pub computation_id: ComputationId,

    /// Input data
    pub input_data: Vec<u8>,

    /// Expected output specifications
    pub expected_outputs: Vec<String>,
}

/// Task execution result
#[derive(Debug, Clone)]
pub struct TaskExecutionResult {
    /// Task identifier
    pub task_id: TaskId,

    /// Execution time
    pub execution_time: std::time::Duration,

    /// Memory used during execution
    pub memory_used: usize,

    /// Energy consumed
    pub energy_consumed: f64,

    /// Output data
    pub output_data: Vec<u8>,
}

/// Device topology information
#[derive(Debug, Clone, Default)]
pub struct DeviceTopology {
    /// Device connections
    pub connections: HashMap<DeviceId, Vec<DeviceId>>,

    /// Bandwidth matrix
    pub bandwidth_matrix: HashMap<(DeviceId, DeviceId), f64>,
}

/// Load balancer for distributing tasks
#[derive(Debug, Clone, Default)]
pub struct LoadBalancer {
    /// Current load per device
    pub device_loads: HashMap<DeviceId, f64>,

    /// Load balancing strategy
    pub strategy: LoadBalancingStrategy,
}

/// Task executor
#[derive(Debug, Clone, Default)]
pub struct TaskExecutor {
    /// Execution threads
    pub thread_count: usize,

    /// Task queue capacity
    pub queue_capacity: usize,
}

impl DeviceManager {
    pub fn new(config: &TPUBackendConfig) -> Result<Self> {
        Ok(Self {
            devices: Vec::new(),
            device_assignments: HashMap::new(),
            device_health: HashMap::new(),
            device_utilization: HashMap::new(),
            topology: DeviceTopology::default(),
            load_balancer: LoadBalancer::default(),
        })
    }

    pub fn get_utilization_stats(&self) -> HashMap<DeviceId, f64> {
        // Return device utilization map directly
        self.device_utilization.clone()
    }
}

impl<T: Float + Debug + Default + Clone + Send + Sync + std::iter::Sum> TPUBackend<T> {
    /// Create a new TPU backend
    pub fn new(config: TPUBackendConfig) -> Result<Self> {
        let device_manager = DeviceManager::new(&config)?;
        let execution_engine = ExecutionEngine::new(&config)?;
        let memory_manager = TPUMemoryManager::new(&config)?;
        let runtime_profiler = RuntimeProfiler::new(&config);
        let error_handler = TPUErrorHandler::new(&config);
        let performance_monitor = PerformanceMonitor::new(&config);
        let compilation_cache = Arc::new(RwLock::new(HashMap::new()));

        Ok(Self {
            config,
            device_manager,
            execution_engine,
            memory_manager,
            runtime_profiler,
            error_handler,
            performance_monitor,
            compilation_cache,
        })
    }

    /// Execute a computation on TPU
    pub async fn execute_computation(
        &mut self,
        computation_id: ComputationId,
        _inputs: Vec<TPUBuffer<T>>,
    ) -> Result<Vec<TPUBuffer<T>>> {
        let start_time = Instant::now();

        // Get or compile the program
        let program = self.get_or_compile_program(computation_id).await?;

        // Select appropriate devices
        let devices = self.device_manager.select_devices(&program)?;

        // Allocate memory
        let memory_allocation = self
            .memory_manager
            .allocate_for_computation(&program, &devices)?;

        // Create computation task
        let task = ComputationTask {
            task_id: TaskId(self.execution_engine.scheduler.next_task_id()),
            computation_id,
            input_data: Vec::new(), // Simplified for now
            expected_outputs: program.metadata.output_specs.clone(),
        };

        // Execute the task
        let results = self
            .execution_engine
            .execute_task(task, &devices, &memory_allocation)?;

        // Update performance metrics
        let execution_time = start_time.elapsed();
        self.performance_monitor
            .record_execution(computation_id, execution_time, &results);

        // Convert the execution result to the expected return type
        // For now, return a placeholder since this is a simplified implementation
        Ok(Vec::new())
    }

    async fn get_or_compile_program(
        &self,
        computation_id: ComputationId,
    ) -> Result<Arc<CompiledProgram>> {
        // Check cache first
        {
            let cache = self.compilation_cache.read().expect("lock poisoned");
            if let Some(program) = cache.get(&computation_id) {
                return Ok(Arc::new(program.clone()));
            }
        }

        // Compile the program
        let program = self.compile_program(computation_id).await?;

        // Cache the result
        {
            let mut cache = self.compilation_cache.write().expect("lock poisoned");
            cache.insert(computation_id, program.clone());
        }

        Ok(Arc::new(program))
    }

    async fn compile_program(&self, _computationid: ComputationId) -> Result<CompiledProgram> {
        // Simplified compilation - in reality this would invoke XLA compiler
        let binary = vec![0u8; 1024]; // Placeholder binary

        let metadata = ProgramMetadata {
            compiled_at: Instant::now(),
            compiler_version: "XLA-1.0.0".to_string(),
            optimization_level: self.config.tpu_config.xla_optimization_level,
            target_architecture: self.config.tpu_config.tpu_version,
            program_size: binary.len(),
            output_specs: Vec::new(),
        };

        let memory_requirements = ProgramMemoryRequirements {
            code_memory: 1024,
            data_memory: 4096,
            stack_memory: 1024,
            scratch_memory: 2048,
            total_memory: 8192,
        };

        let performance_characteristics = ProgramPerformanceCharacteristics {
            estimated_execution_time: Duration::from_micros(100),
            estimated_flops: 1000000,
            memory_bandwidth_utilization: 0.75,
            compute_utilization: 0.85,
        };

        Ok(CompiledProgram {
            binary,
            metadata,
            memory_requirements,
            performance_characteristics,
        })
    }

    /// Get backend performance statistics
    pub fn get_performance_statistics(&self) -> BackendPerformanceStatistics {
        BackendPerformanceStatistics {
            total_executions: self.performance_monitor.total_executions,
            average_execution_time: self.performance_monitor.average_execution_time,
            device_utilization: self.device_manager.get_utilization_stats(),
            memory_utilization: self.memory_manager.get_utilization_stats(),
            cache_hit_rate: self.get_cache_hit_rate(),
            error_rate: self.error_handler.get_error_rate(),
        }
    }

    fn get_cache_hit_rate(&self) -> f64 {
        // Simplified cache hit rate calculation
        0.85 // Placeholder
    }

    /// Shutdown the backend gracefully
    pub async fn shutdown(&mut self) -> Result<()> {
        self.device_manager.shutdown().await?;
        self.memory_manager.cleanup()?;
        self.performance_monitor.flush_metrics()?;
        Ok(())
    }
}

/// Backend performance statistics
#[derive(Debug, Clone)]
pub struct BackendPerformanceStatistics {
    pub total_executions: usize,
    pub average_execution_time: Duration,
    pub device_utilization: HashMap<DeviceId, f64>,
    pub memory_utilization: f64,
    pub cache_hit_rate: f64,
    pub error_rate: f64,
}

/// TPU memory manager
#[derive(Debug)]
pub struct TPUMemoryManager<T: Float + Debug + Send + Sync + 'static> {
    /// Memory pools
    memory_pools: HashMap<DeviceId, MemoryPool<T>>,

    /// Allocation strategy
    allocation_strategy: MemoryAllocationStrategy,

    /// Memory usage statistics
    usage_statistics: MemoryUsageStatistics,

    /// Garbage collector
    garbage_collector: MemoryGarbageCollector<T>,
}

/// Memory pool for a device
#[derive(Debug)]
pub struct MemoryPool<T: Float + Debug + Send + Sync + 'static> {
    /// Total pool size
    total_size: usize,

    /// Available memory
    available_memory: usize,

    /// Free blocks
    free_blocks: Vec<MemoryBlock>,

    /// Allocated blocks
    allocated_blocks: HashMap<usize, MemoryBlock>,

    /// Allocation counter
    allocation_counter: usize,

    /// Phantom data
    _phantom: std::marker::PhantomData<T>,
}

/// Memory block descriptor
#[derive(Debug, Clone)]
pub struct MemoryBlock {
    /// Block start address
    pub start_address: usize,

    /// Block size
    pub size: usize,

    /// Allocation timestamp
    pub allocated_at: Instant,

    /// Last access timestamp
    pub last_accessed: Instant,

    /// Access count
    pub access_count: usize,
}

/// Memory usage statistics
#[derive(Debug, Clone)]
pub struct MemoryUsageStatistics {
    /// Total allocated memory
    pub total_allocated: usize,

    /// Peak memory usage
    pub peak_usage: usize,

    /// Average allocation size
    pub average_allocation_size: usize,

    /// Fragmentation ratio
    pub fragmentation_ratio: f64,

    /// Allocation success rate
    pub allocation_success_rate: f64,
}

/// Memory garbage collector
#[derive(Debug)]
pub struct MemoryGarbageCollector<T: Float + Debug + Send + Sync + 'static> {
    /// Collection strategy
    strategy: GCStrategy,

    /// Collection threshold
    threshold: f64,

    /// Last collection time
    last_collection: Instant,

    /// Collection statistics
    statistics: GCStatistics,

    /// Phantom data
    _phantom: std::marker::PhantomData<T>,
}

/// Garbage collection strategies
#[derive(Debug, Clone, Copy)]
pub enum GCStrategy {
    MarkAndSweep,
    Generational,
    Reference,
    LeastRecentlyUsed,
    Adaptive,
}

/// Garbage collection statistics
#[derive(Debug, Clone)]
pub struct GCStatistics {
    /// Total collections
    pub total_collections: usize,

    /// Total memory reclaimed
    pub total_memory_reclaimed: usize,

    /// Average collection time
    pub average_collection_time: Duration,

    /// Collection efficiency
    pub collection_efficiency: f64,
}

/// Runtime profiler
#[derive(Debug)]
pub struct RuntimeProfiler {
    /// Profiling enabled
    enabled: bool,

    /// Profile data
    profile_data: Vec<ProfileSample>,

    /// Sampling interval
    sampling_interval: Duration,

    /// Last sample time
    last_sample: Instant,
}

impl RuntimeProfiler {
    /// Create a new runtime profiler
    pub fn new(config: &TPUBackendConfig) -> Self {
        Self {
            enabled: config.enable_performance_monitoring,
            profile_data: Vec::new(),
            sampling_interval: Duration::from_millis(100),
            last_sample: Instant::now(),
        }
    }
}

/// Profile sample
#[derive(Debug, Clone)]
pub struct ProfileSample {
    /// Timestamp
    pub timestamp: Instant,

    /// CPU utilization
    pub cpu_utilization: f64,

    /// Memory utilization
    pub memory_utilization: f64,

    /// Device utilization
    pub device_utilization: HashMap<DeviceId, f64>,

    /// Active tasks
    pub active_tasks: usize,

    /// Queue length
    pub queue_length: usize,
}

/// TPU error handler
#[derive(Debug)]
pub struct TPUErrorHandler {
    /// Error recovery enabled
    recovery_enabled: bool,

    /// Error statistics
    error_statistics: ErrorStatistics,

    /// Recovery strategies
    recovery_strategies: HashMap<ErrorType, RecoveryStrategy>,

    /// Max retry attempts
    max_retry_attempts: usize,
}

impl TPUErrorHandler {
    /// Create a new TPU error handler
    pub fn new(config: &TPUBackendConfig) -> Self {
        Self {
            recovery_enabled: config.enable_error_recovery,
            error_statistics: ErrorStatistics::default(),
            recovery_strategies: HashMap::new(),
            max_retry_attempts: config.max_retry_attempts,
        }
    }

    /// Get current error rate
    pub fn get_error_rate(&self) -> f64 {
        self.error_statistics.error_rate
    }
}

/// Error statistics
#[derive(Debug, Clone)]
pub struct ErrorStatistics {
    /// Total errors
    pub total_errors: usize,

    /// Error rate
    pub error_rate: f64,

    /// Errors by type
    pub errors_by_type: HashMap<ErrorType, usize>,

    /// Recovery success rate
    pub recovery_success_rate: f64,
}

impl Default for ErrorStatistics {
    fn default() -> Self {
        Self {
            total_errors: 0,
            error_rate: 0.0,
            errors_by_type: HashMap::new(),
            recovery_success_rate: 0.0,
        }
    }
}

/// Error types
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum ErrorType {
    DeviceError,
    MemoryError,
    ComputationError,
    CommunicationError,
    TimeoutError,
    ResourceError,
}

/// Recovery strategies
#[derive(Debug, Clone, Copy)]
pub enum RecoveryStrategy {
    Retry,
    Fallback,
    Restart,
    Migrate,
    Ignore,
}

/// Performance monitor
#[derive(Debug)]
pub struct PerformanceMonitor {
    /// Monitoring enabled
    enabled: bool,

    /// Total executions
    pub total_executions: usize,

    /// Average execution time
    pub average_execution_time: Duration,

    /// Performance history
    performance_history: VecDeque<PerformanceSample>,

    /// Metrics collection interval
    collection_interval: Duration,
}

impl PerformanceMonitor {
    /// Create a new performance monitor
    pub fn new(config: &TPUBackendConfig) -> Self {
        Self {
            enabled: config.enable_performance_monitoring,
            total_executions: 0,
            average_execution_time: Duration::from_millis(0),
            performance_history: VecDeque::new(),
            collection_interval: Duration::from_millis(1000),
        }
    }
}

/// Performance sample
#[derive(Debug, Clone)]
pub struct PerformanceSample {
    /// Timestamp
    pub timestamp: Instant,

    /// Execution time
    pub execution_time: Duration,

    /// Throughput
    pub throughput: f64,

    /// Device utilization
    pub device_utilization: f64,

    /// Memory utilization
    pub memory_utilization: f64,
}

impl<T: Float + Debug + Send + Sync + 'static> TPUMemoryManager<T> {
    /// Create a new TPU memory manager
    pub fn new(config: &TPUBackendConfig) -> Result<Self> {
        let usage_statistics = MemoryUsageStatistics {
            total_allocated: 0,
            peak_usage: 0,
            average_allocation_size: 0,
            fragmentation_ratio: 0.0,
            allocation_success_rate: 1.0,
        };

        let gc_statistics = GCStatistics {
            total_collections: 0,
            total_memory_reclaimed: 0,
            average_collection_time: Duration::from_millis(0),
            collection_efficiency: 0.0,
        };

        let garbage_collector = MemoryGarbageCollector {
            strategy: GCStrategy::Adaptive,
            threshold: 0.8,
            last_collection: Instant::now(),
            statistics: GCStatistics {
                total_collections: 0,
                total_memory_reclaimed: 0,
                average_collection_time: Duration::from_secs(0),
                collection_efficiency: 0.0,
            },
            _phantom: std::marker::PhantomData,
        };

        Ok(Self {
            memory_pools: HashMap::new(),
            allocation_strategy: config.memory_allocation_strategy,
            usage_statistics,
            garbage_collector,
        })
    }

    /// Get memory utilization statistics
    pub fn get_utilization_stats(&self) -> f64 {
        if self.usage_statistics.total_allocated == 0 {
            0.0
        } else {
            self.usage_statistics.total_allocated as f64
                / self.usage_statistics.peak_usage.max(1) as f64
        }
    }

    /// Cleanup memory resources
    pub fn cleanup(&mut self) -> Result<()> {
        self.memory_pools.clear();
        self.usage_statistics.total_allocated = 0;
        Ok(())
    }

    pub fn allocate_for_computation(
        &self,
        _program: &CompiledProgram,
        _devices: &[DeviceId],
    ) -> Result<MemoryAllocation> {
        // Simple implementation
        Ok(MemoryAllocation {
            device_allocations: HashMap::new(),
            total_allocated: 0,
        })
    }
}

impl<T: Float + Debug + Send + Sync + 'static> ExecutionScheduler<T> {
    pub fn next_task_id(&mut self) -> u64 {
        // Simple implementation
        0
    }
}

impl<T: Float + Debug + Send + Sync + 'static> ExecutionEngine<T> {
    pub fn new(config: &TPUBackendConfig) -> Result<Self> {
        Ok(Self {
            scheduler: ExecutionScheduler {
                execution_queue: VecDeque::new(),
                scheduling_policy: SchedulingPolicy::FIFO,
                priority_manager: PriorityManager { level: 0 },
                dependency_resolver: DependencyResolver {
                    dependencies: Vec::new(),
                },
            },
            executor: RuntimeExecutor { state: T::zero() },
            result_collector: ResultCollector {
                results: Vec::new(),
            },
            context: ExecutionContext { id: 0 },
            performance_optimizer: PerformanceOptimizer { level: T::zero() },
        })
    }

    pub fn execute_task(
        &self,
        _task: ComputationTask,
        _devices: &[DeviceId],
        _memory_allocation: &MemoryAllocation,
    ) -> Result<TaskExecutionResult> {
        // Simple implementation
        Ok(TaskExecutionResult {
            task_id: TaskId(0),
            execution_time: std::time::Duration::from_millis(100),
            memory_used: 1024,
            energy_consumed: 10.0,
            output_data: Vec::new(),
        })
    }
}

impl PerformanceMonitor {
    pub fn record_execution(
        &mut self,
        _computation_id: ComputationId,
        _time: std::time::Duration,
        _results: &TaskExecutionResult,
    ) {
        // Simple implementation - record metrics
    }

    pub fn flush_metrics(&mut self) -> Result<()> {
        // Simple implementation - flush metrics
        Ok(())
    }
}

impl DeviceManager {
    pub async fn shutdown(&mut self) -> Result<()> {
        // Simple implementation - shutdown all devices
        self.devices.clear();
        self.device_assignments.clear();
        self.device_health.clear();
        self.device_utilization.clear();
        Ok(())
    }

    pub fn select_devices(&self, program: &CompiledProgram) -> Result<Vec<DeviceId>> {
        // Simple implementation - return first available device
        if self.devices.is_empty() {
            Ok(Vec::new())
        } else {
            Ok(vec![self.devices[0].id])
        }
    }
}

// Implementation of supporting structures and methods

impl Default for TPUBackendConfig {
    fn default() -> Self {
        Self {
            tpu_config: super::TPUConfig::default(),
            runtime_optimization: true,
            auto_memory_management: true,
            execution_timeout_ms: 30000,
            enable_performance_monitoring: true,
            async_buffer_size: 32,
            enable_error_recovery: true,
            max_retry_attempts: 3,
            prefetch_strategy: PrefetchStrategy::Adaptive,
            memory_allocation_strategy: MemoryAllocationStrategy::BestFit,
        }
    }
}

impl Default for ExecutionConstraints {
    fn default() -> Self {
        Self {
            required_features: Vec::new(),
            memory_constraints: MemoryConstraints {
                max_memory_usage: usize::MAX,
                min_bandwidth_gb_s: 0.0,
                layout_preferences: vec![MemoryLayout::RowMajor],
            },
            performance_constraints: PerformanceConstraints {
                max_execution_time: Duration::from_secs(300),
                min_throughput: 0.0,
                max_latency: Duration::from_millis(100),
                power_budget: None,
            },
            locality_constraints: LocalityConstraints {
                preferred_devices: Vec::new(),
                avoid_devices: Vec::new(),
                locality_scope: LocalityScope::Global,
            },
        }
    }
}

impl<T: Float + Debug + Send + Sync + 'static> TPUBuffer<T> {
    /// Create a new TPU buffer
    pub fn new(data: Vec<T>, shape: Vec<usize>, layout: MemoryLayout) -> Self {
        Self {
            data,
            shape,
            layout,
            device: None,
            metadata: BufferMetadata {
                created_at: Instant::now(),
                last_accessed: Instant::now(),
                access_count: 0,
                data_type: DataType::F32, // Simplified
                flags: BufferFlags {
                    read_only: false,
                    persistent: false,
                    prefetch: false,
                    pinned: false,
                },
            },
        }
    }

    /// Get buffer size in bytes
    pub fn size_bytes(&self) -> usize {
        self.data.len() * std::mem::size_of::<T>()
    }

    /// Transfer buffer to device
    pub fn transfer_to_device(&mut self, device: DeviceId) -> Result<()> {
        self.device = Some(device);
        self.metadata.last_accessed = Instant::now();
        self.metadata.access_count += 1;
        Ok(())
    }
}

// Additional implementation details would be added here for all the supporting structures
// This represents a comprehensive TPU backend implementation

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

    #[test]
    fn test_tpu_backend_creation() {
        let config = TPUBackendConfig::default();
        let backend = TPUBackend::<f32>::new(config);
        assert!(backend.is_ok());
    }

    #[test]
    fn test_tpu_buffer_creation() {
        let data = vec![1.0, 2.0, 3.0, 4.0];
        let shape = vec![2, 2];
        let buffer = TPUBuffer::new(data, shape, MemoryLayout::RowMajor);

        assert_eq!(buffer.shape, vec![2, 2]);
        assert_eq!(buffer.data.len(), 4);
    }

    #[test]
    fn test_device_health_status() {
        let health = DeviceHealthStatus {
            health_score: 0.95,
            temperature: 45.0,
            power_consumption: 150.0,
            memory_health: MemoryHealthStatus {
                error_count: 0,
                bandwidth_efficiency: 0.92,
                fragmentation_ratio: 0.05,
            },
            compute_health: ComputeHealthStatus {
                matrix_unit_efficiency: 0.88,
                vector_unit_efficiency: 0.90,
                scalar_unit_efficiency: 0.85,
                instruction_cache_hit_rate: 0.95,
            },
            last_check: Instant::now(),
        };

        assert!(health.health_score > 0.9);
        assert!(health.temperature < 50.0);
    }
}