auradb 0.1.0

//! Cache module for block and value log caching
//! 
//! This module will implement unified caching with multiple eviction policies.
//! 
//! Planned for M2 milestone.

use crate::error::{Error, Result};

/// Cache eviction policy
#[derive(Debug, Clone)]
pub enum EvictionPolicy {
    /// LRU (Least Recently Used)
    Lru,
    /// ARC (Adaptive Replacement Cache)
    Arc,
    /// TinyLFU
    TinyLfu,
}

/// Cache entry
#[derive(Debug, Clone)]
pub struct CacheEntry {
    /// Entry key
    pub key: Vec<u8>,
    /// Entry data
    pub data: Vec<u8>,
    /// Access count
    pub access_count: u64,
    /// Last access time
    pub last_access: u64,
}

/// Unified cache for SST blocks and vlog pages
pub struct UnifiedCache {
    // TODO: Implement cache functionality
}

impl UnifiedCache {
    /// Create a new unified cache
    pub fn new(_capacity: usize, _policy: EvictionPolicy) -> Self {
        Self {}
    }
    
    /// Get an entry from cache
    pub fn get(&mut self, _key: &[u8]) -> Option<Vec<u8>> {
        // TODO: Implement
        None
    }
    
    /// Put an entry into cache
    pub fn put(&mut self, _key: Vec<u8>, _data: Vec<u8>) -> Result<()> {
        // TODO: Implement
        Ok(())
    }
    
    /// Get cache statistics
    pub fn stats(&self) -> CacheStats {
        // TODO: Implement
        CacheStats::default()
    }
}

/// Cache statistics
#[derive(Debug, Clone, Default)]
pub struct CacheStats {
    /// Hit count
    pub hits: u64,
    /// Miss count
    pub misses: u64,
    /// Current size
    pub size: usize,
    /// Capacity
    pub capacity: usize,
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn test_cache_creation() {
        let cache = UnifiedCache::new(1024, EvictionPolicy::Lru);
        let stats = cache.stats();
        assert_eq!(stats.capacity, 1024);
    }
}