Integration Features

/**
 * Adapts JCache CacheLoader to Caffeine CacheLoader for integration
 */
public final class JCacheLoaderAdapter<K, V> implements CacheLoader<K, Expirable<V>> {
    
    /**
     * Load a single entry from external data source
     * @param key the key to load
     * @return wrapped value with expiration information
     */
    public @Nullable Expirable<V> load(K key);
    
    /**
     * Load multiple entries from external data source
     * @param keys the keys to load
     * @return map of loaded key-value pairs
     */
    public Map<K, Expirable<V>> loadAll(Set<? extends K> keys);
}

// Implement custom cache loader
public class DatabaseUserLoader implements CacheLoader<String, User> {
    private final UserRepository userRepository;
    
    public DatabaseUserLoader(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
    
    @Override
    public User load(String userId) throws CacheLoaderException {
        try {
            User user = userRepository.findById(userId);
            if (user == null) {
                throw new CacheLoaderException("User not found: " + userId);
            }
            return user;
        } catch (Exception e) {
            throw new CacheLoaderException("Failed to load user: " + userId, e);
        }
    }
    
    @Override
    public Map<String, User> loadAll(Iterable<? extends String> userIds) throws CacheLoaderException {
        try {
            Map<String, User> users = new HashMap<>();
            for (String userId : userIds) {
                User user = userRepository.findById(userId);
                if (user != null) {
                    users.put(userId, user);
                }
            }
            return users;
        } catch (Exception e) {
            throw new CacheLoaderException("Failed to load users", e);
        }
    }
}

// Configure cache with loader
CaffeineConfiguration<String, User> config = new CaffeineConfiguration<String, User>()
    .setTypes(String.class, User.class)
    .setCacheLoaderFactory(() -> new DatabaseUserLoader(userRepository))
    .setReadThrough(true);

Cache<String, User> userCache = cacheManager.createCache("users", config);

// Automatic loading on cache miss
User user = userCache.get("user123"); // Loads from database if not cached

/**
 * Disabled cache writer implementation for caches without write-through
 */
public enum DisabledCacheWriter implements CacheWriter<Object, Object> {
    INSTANCE;
    
    /**
     * Get singleton instance of disabled cache writer
     * @return the singleton instance
     */
    public static CacheWriter<Object, Object> get();
    
    /**
     * No-op write operation
     * @param entry the entry to write (ignored)
     */
    public void write(Cache.Entry<? extends Object, ? extends Object> entry);
    
    /**
     * No-op write all operation
     * @param entries the entries to write (ignored)
     */
    public void writeAll(Collection<Cache.Entry<? extends Object, ? extends Object>> entries);
    
    /**
     * No-op delete operation
     * @param key the key to delete (ignored)
     */
    public void delete(Object key);
    
    /**
     * No-op delete all operation
     * @param keys the keys to delete (ignored)
     */
    public void deleteAll(Collection<?> keys);
}

// Implement custom cache writer
public class DatabaseUserWriter implements CacheWriter<String, User> {
    private final UserRepository userRepository;
    
    public DatabaseUserWriter(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
    
    @Override
    public void write(Cache.Entry<? extends String, ? extends User> entry) throws CacheWriterException {
        try {
            userRepository.save(entry.getValue());
        } catch (Exception e) {
            throw new CacheWriterException("Failed to write user: " + entry.getKey(), e);
        }
    }
    
    @Override
    public void writeAll(Collection<Cache.Entry<? extends String, ? extends User>> entries) 
            throws CacheWriterException {
        try {
            List<User> users = entries.stream()
                .map(Cache.Entry::getValue)
                .collect(Collectors.toList());
            userRepository.saveAll(users);
        } catch (Exception e) {
            throw new CacheWriterException("Failed to write users", e);
        }
    }
    
    @Override
    public void delete(Object key) throws CacheWriterException {
        try {
            userRepository.deleteById((String) key);
        } catch (Exception e) {
            throw new CacheWriterException("Failed to delete user: " + key, e);
        }
    }
    
    @Override
    public void deleteAll(Collection<?> keys) throws CacheWriterException {
        try {
            List<String> userIds = keys.stream()
                .map(String.class::cast)
                .collect(Collectors.toList());
            userRepository.deleteAllById(userIds);
        } catch (Exception e) {
            throw new CacheWriterException("Failed to delete users", e);
        }
    }
}

// Configure cache with writer
CaffeineConfiguration<String, User> config = new CaffeineConfiguration<String, User>()
    .setTypes(String.class, User.class)
    .setCacheWriterFactory(() -> new DatabaseUserWriter(userRepository))
    .setWriteThrough(true);

Cache<String, User> userCache = cacheManager.createCache("users", config);

// Automatic writing to database
userCache.put("user123", new User("John Doe")); // Also saves to database
userCache.remove("user123"); // Also deletes from database

/**
 * Interface for copying objects for store-by-value semantics
 */
public interface Copier {
    
    /**
     * Copy an object using the specified ClassLoader
     * @param object the object to copy
     * @param classLoader the ClassLoader for deserialization
     * @return copied object
     */
    public <T> T copy(T object, ClassLoader classLoader);
    
    /**
     * Get identity copier that returns objects unchanged
     * @return identity copier instance
     */
    public static Copier identity();
}

/**
 * Copier implementation using Java serialization
 */
public class JavaSerializationCopier extends AbstractCopier<byte[]> {
    
    /**
     * Create new Java serialization copier
     */
    public JavaSerializationCopier();
    
    /**
     * Serialize object to byte array
     * @param object the object to serialize
     * @param classLoader the ClassLoader for serialization
     * @return serialized byte array
     */
    protected byte[] serialize(Object object, ClassLoader classLoader);
    
    /**
     * Deserialize byte array to object
     * @param data the serialized data
     * @param classLoader the ClassLoader for deserialization
     * @return deserialized object
     */
    protected Object deserialize(byte[] data, ClassLoader classLoader);
}

// Custom copier implementation using JSON
public class JsonCopier implements Copier {
    private final ObjectMapper objectMapper;
    
    public JsonCopier() {
        this.objectMapper = new ObjectMapper();
    }
    
    @Override
    public <T> T copy(T object, ClassLoader classLoader) {
        if (object == null) {
            return null;
        }
        
        try {
            // Serialize to JSON and deserialize back
            String json = objectMapper.writeValueAsString(object);
            @SuppressWarnings("unchecked")
            Class<T> clazz = (Class<T>) object.getClass();
            return objectMapper.readValue(json, clazz);
        } catch (Exception e) {
            throw new RuntimeException("Failed to copy object", e);
        }
    }
}

// Configure cache with custom copier
CaffeineConfiguration<String, User> config = new CaffeineConfiguration<String, User>()
    .setTypes(String.class, User.class)
    .setStoreByValue(true)
    .setCopierFactory(() -> new JsonCopier());

Cache<String, User> userCache = cacheManager.createCache("users", config);

// Objects are copied on store and retrieve
User original = new User("John Doe");
userCache.put("user1", original);
User retrieved = userCache.get("user1"); // Different instance, same data
assert original != retrieved; // Different object references
assert original.equals(retrieved); // Same data

/**
 * Mutable entry implementation for entry processors
 */
public final class EntryProcessorEntry<K, V> implements MutableEntry<K, V> {
    
    /**
     * Get the entry key
     * @return the key of this entry
     */
    public K getKey();
    
    /**
     * Get the entry value
     * @return the value of this entry, or null if not present
     */
    public V getValue();
    
    /**
     * Check if the entry exists in the cache
     * @return true if the entry exists
     */
    public boolean exists();
    
    /**
     * Remove this entry from the cache
     */
    public void remove();
    
    /**
     * Set the value of this entry
     * @param value the new value to set
     */
    public void setValue(V value);
    
    /**
     * Unwrap this entry to a specific type
     * @param clazz the class to unwrap to
     * @return unwrapped instance
     */
    public <T> T unwrap(Class<T> clazz);
}

/**
 * Entry processor action enumeration
 */
public enum Action {
    NONE,     // No action performed
    READ,     // Entry was read
    CREATED,  // Entry was created
    LOADED,   // Entry was loaded from external source
    UPDATED,  // Entry was updated
    DELETED   // Entry was deleted
}

// Counter increment entry processor
EntryProcessor<String, AtomicInteger, Integer> incrementProcessor = 
    (entry, arguments) -> {
        AtomicInteger counter = entry.getValue();
        if (counter == null) {
            counter = new AtomicInteger(0);
        }
        int newValue = counter.incrementAndGet();
        entry.setValue(counter);
        return newValue;
    };

// Conditional update entry processor
EntryProcessor<String, User, Boolean> updateEmailProcessor = 
    (entry, arguments) -> {
        User user = entry.getValue();
        if (user == null) {
            return false;
        }
        
        String newEmail = (String) arguments[0];
        if (!isValidEmail(newEmail)) {
            return false;
        }
        
        user.setEmail(newEmail);
        entry.setValue(user);
        return true;
    };

// Complex business logic processor
EntryProcessor<String, Account, TransactionResult> transferProcessor = 
    (entry, arguments) -> {
        Account account = entry.getValue();
        BigDecimal amount = (BigDecimal) arguments[0];
        String transactionId = (String) arguments[1];
        
        if (account == null) {
            return new TransactionResult(false, "Account not found");
        }
        
        if (account.getBalance().compareTo(amount) < 0) {
            return new TransactionResult(false, "Insufficient funds");
        }
        
        // Perform transfer
        account.setBalance(account.getBalance().subtract(amount));
        account.addTransaction(new Transaction(transactionId, amount));
        entry.setValue(account);
        
        return new TransactionResult(true, "Transfer completed");
    };

// Use entry processors
Integer newCount = cache.invoke("counter1", incrementProcessor);
Boolean emailUpdated = cache.invoke("user123", updateEmailProcessor, "new@example.com");
TransactionResult result = cache.invoke("account456", transferProcessor, 
    new BigDecimal("100.00"), "txn-789");

// Database integration pattern
public class DatabaseIntegratedCache<K, V> {
    private final Cache<K, V> cache;
    private final Repository<K, V> repository;
    
    public DatabaseIntegratedCache(Cache<K, V> cache, Repository<K, V> repository) {
        this.cache = cache;
        this.repository = repository;
    }
    
    // Write-behind pattern
    public void putAsync(K key, V value) {
        cache.put(key, value);
        CompletableFuture.runAsync(() -> {
            try {
                repository.save(key, value);
            } catch (Exception e) {
                // Handle async write failure
                handleWriteFailure(key, value, e);
            }
        });
    }
    
    // Cache-aside pattern
    public V getWithFallback(K key) {
        V value = cache.get(key);
        if (value == null) {
            value = repository.findById(key);
            if (value != null) {
                cache.put(key, value);
            }
        }
        return value;
    }
    
    private void handleWriteFailure(K key, V value, Exception e) {
        // Implement failure handling strategy
    }
}

// Web service integration pattern  
public class WebServiceCacheLoader implements CacheLoader<String, ApiResponse> {
    private final WebClient webClient;
    private final CircuitBreaker circuitBreaker;
    
    @Override
    public ApiResponse load(String endpoint) throws CacheLoaderException {
        return circuitBreaker.executeSupplier(() -> {
            try {
                return webClient.get()
                    .uri(endpoint)
                    .retrieve()
                    .bodyToMono(ApiResponse.class)
                    .block(Duration.ofSeconds(10));
            } catch (Exception e) {
                throw new CacheLoaderException("Failed to load from web service", e);
            }
        });
    }
}

// Event-driven invalidation pattern
public class EventDrivenCacheInvalidation {
    private final Cache<String, Object> cache;
    private final EventBus eventBus;
    
    public EventDrivenCacheInvalidation(Cache<String, Object> cache, EventBus eventBus) {
        this.cache = cache;
        this.eventBus = eventBus;
        
        // Register for invalidation events
        eventBus.register(this);
    }
    
    @Subscribe
    public void handleInvalidationEvent(CacheInvalidationEvent event) {
        if (event.isInvalidateAll()) {
            cache.removeAll();
        } else {
            cache.removeAll(event.getKeysToInvalidate());
        }
    }
}

public class BulkOperationHelper {
    
    // Bulk load with batching
    public static <K, V> void bulkLoadWithBatching(
            Cache<K, V> cache, 
            Set<K> keys, 
            CacheLoader<K, V> loader,
            int batchSize) {
        
        List<K> keyList = new ArrayList<>(keys);
        for (int i = 0; i < keyList.size(); i += batchSize) {
            int endIndex = Math.min(i + batchSize, keyList.size());
            List<K> batch = keyList.subList(i, endIndex);
            
            try {
                Map<K, V> loaded = loader.loadAll(batch);
                cache.putAll(loaded);
            } catch (Exception e) {
                // Handle batch failure - could retry individual items
                handleBatchFailure(cache, batch, loader, e);
            }
        }
    }
    
    // Bulk write with error handling
    public static <K, V> void bulkWriteWithErrorHandling(
            Cache<K, V> cache,
            Map<K, V> entries,
            CacheWriter<K, V> writer) {
        
        try {
            List<Cache.Entry<K, V>> entryList = entries.entrySet().stream()
                .map(e -> new SimpleEntry<>(e.getKey(), e.getValue()))
                .collect(Collectors.toList());
            
            writer.writeAll(entryList);
            cache.putAll(entries);
        } catch (CacheWriterException e) {
            // Fall back to individual writes
            for (Map.Entry<K, V> entry : entries.entrySet()) {
                try {
                    writer.write(new SimpleEntry<>(entry.getKey(), entry.getValue()));
                    cache.put(entry.getKey(), entry.getValue());
                } catch (Exception individualError) {
                    // Log individual failure but continue
                    handleIndividualWriteFailure(entry.getKey(), entry.getValue(), individualError);
                }
            }
        }
    }
    
    private static <K, V> void handleBatchFailure(Cache<K, V> cache, List<K> batch, 
                                                 CacheLoader<K, V> loader, Exception e) {
        // Implementation depends on failure handling strategy
    }
    
    private static <K, V> void handleIndividualWriteFailure(K key, V value, Exception e) {
        // Implementation depends on failure handling strategy
    }
}