//! Kernel cache for compiled functions

use crate::advanced_jit_compilation::config::{CacheConfig, EvictionPolicy, JitCompilerConfig};
use crate::advanced_jit_compilation::llvm_engine::CompiledModule;
use crate::error::{CoreError, CoreResult};
#[cfg(feature = "serialization")]
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::time::{Duration, Instant};

/// Kernel cache for compiled functions
#[derive(Debug)]
pub struct KernelCache {
    /// Cached kernels
    kernels: HashMap<String, CachedKernel>,
    /// Cache statistics
    pub stats: CacheStatistics,
    /// Cache configuration
    #[allow(dead_code)]
    config: CacheConfig,
    /// LRU eviction list
    #[allow(dead_code)]
    lru_list: Vec<String>,
}

/// Cached kernel representation
#[derive(Debug, Clone)]
pub struct CachedKernel {
    /// Kernel identifier
    pub id: String,
    /// Compiled function pointer
    pub functionptr: usize,
    /// Kernel metadata
    pub metadata: KernelMetadata,
    /// Performance metrics
    pub performance: KernelPerformance,
    /// Last access time
    pub last_accessed: Instant,
    /// Access count
    pub access_count: u64,
}

/// Kernel metadata
#[cfg_attr(feature = "serialization", derive(Serialize, Deserialize))]
#[derive(Debug, Clone)]
pub struct KernelMetadata {
    /// Kernel name
    pub name: String,
    /// Input types
    pub input_types: Vec<String>,
    /// Output type
    pub output_type: String,
    /// Specialization parameters
    pub specialization_params: HashMap<String, String>,
    /// Compilation flags
    pub compilation_flags: Vec<String>,
    /// Source code fingerprint
    pub source_fingerprint: u64,
}

/// Kernel performance metrics
#[derive(Debug, Clone)]
pub struct KernelPerformance {
    /// Execution time statistics
    pub execution_times: Vec<Duration>,
    /// Memory access patterns
    pub memory_access_patterns: MemoryAccessPattern,
    /// Vectorization utilization
    pub vectorization_utilization: f64,
    /// Branch prediction accuracy
    pub branch_prediction_accuracy: f64,
    /// Cache hit rates
    pub cache_hit_rates: CacheHitRates,
}

/// Memory access patterns
#[derive(Debug, Clone)]
pub struct MemoryAccessPattern {
    /// Sequential access percentage
    pub sequential_access: f64,
    /// Random access percentage
    pub random_access: f64,
    /// Stride access percentage
    pub stride_access: f64,
    /// Prefetch efficiency
    pub prefetch_efficiency: f64,
}

/// Cache hit rates
#[derive(Debug, Clone)]
pub struct CacheHitRates {
    /// L1 cache hit rate
    pub l1_hit_rate: f64,
    /// L2 cache hit rate
    pub l2_hit_rate: f64,
    /// L3 cache hit rate
    pub l3_hit_rate: f64,
    /// TLB hit rate
    pub tlb_hit_rate: f64,
}

/// Cache statistics
#[derive(Debug, Clone)]
pub struct CacheStatistics {
    /// Total cache hits
    pub hits: u64,
    /// Total cache misses
    pub misses: u64,
    /// Cache evictions
    pub evictions: u64,
    /// Current cache size
    pub current_size_bytes: usize,
    /// Maximum cache size
    pub maxsize_bytes: usize,
}

/// Compiled kernel representation
#[derive(Debug)]
pub struct CompiledKernel {
    /// Kernel name
    pub name: String,
    /// Compiled module
    pub compiled_module: CompiledModule,
    /// Kernel metadata
    pub metadata: KernelMetadata,
    /// Performance metrics
    pub performance: KernelPerformance,
    /// Creation timestamp
    pub created_at: Instant,
}

impl Default for KernelPerformance {
    fn default() -> Self {
        Self {
            execution_times: Vec::new(),
            memory_access_patterns: MemoryAccessPattern {
                sequential_access: 0.8,
                random_access: 0.1,
                stride_access: 0.1,
                prefetch_efficiency: 0.7,
            },
            vectorization_utilization: 0.6,
            branch_prediction_accuracy: 0.9,
            cache_hit_rates: CacheHitRates {
                l1_hit_rate: 0.95,
                l2_hit_rate: 0.85,
                l3_hit_rate: 0.75,
                tlb_hit_rate: 0.98,
            },
        }
    }
}

impl KernelCache {
    pub fn new(config: &JitCompilerConfig) -> CoreResult<Self> {
        Ok(Self {
            kernels: HashMap::new(),
            stats: CacheStatistics {
                hits: 0,
                misses: 0,
                evictions: 0,
                current_size_bytes: 0,
                maxsize_bytes: 512 * 1024 * 1024, // 512MB
            },
            config: CacheConfig {
                maxsize_mb: 512,
                eviction_policy: EvictionPolicy::LRU,
                enable_cache_warming: true,
                enable_persistence: false,
                persistence_dir: None,
            },
            lru_list: Vec::new(),
        })
    }

    pub fn get(&self, name: &str) -> Option<&CachedKernel> {
        self.kernels.get(name)
    }

    pub fn insert(&mut self, kernel: &CompiledKernel) -> CoreResult<()> {
        // Simplified implementation
        Ok(())
    }

    pub fn get_statistics(&self) -> CacheStatistics {
        self.stats.clone()
    }
}

impl CachedKernel {
    pub fn is_valid_for_source(&self, source: &str) -> bool {
        // Simplified implementation
        true
    }
}

impl CompiledKernel {
    /// Get function pointer for execution
    pub fn get_function_pointer(&self) -> CoreResult<usize> {
        self.compiled_module
            .function_pointers
            .get("main")
            .copied()
            .ok_or_else(|| {
                CoreError::InvalidArgument(crate::error::ErrorContext::new(
                    "Main function not found".to_string(),
                ))
            })
    }
}
