State Management

/**
 * Base interface for all state types
 */
interface State {
    /**
     * Clear the state
     */
    void clear();
}

/**
 * State that holds a single value
 * @param <T> Type of the value
 */
interface ValueState<T> extends State {
    /**
     * Get current value
     * @return Current value, null if not set
     * @throws Exception
     */
    T value() throws Exception;
    
    /**
     * Update the state value
     * @param value New value
     * @throws Exception
     */
    void update(T value) throws Exception;
}

/**
 * State that holds a list of elements
 * @param <T> Type of elements in the list
 */
interface ListState<T> extends State {
    /**
     * Get all elements in the list
     * @return Iterable over all elements
     * @throws Exception
     */
    Iterable<T> get() throws Exception;
    
    /**
     * Add element to the list
     * @param value Element to add
     * @throws Exception
     */
    void add(T value) throws Exception;
    
    /**
     * Add all elements from iterable to the list
     * @param values Elements to add
     * @throws Exception
     */
    void addAll(List<T> values) throws Exception;
    
    /**
     * Replace all elements in the list
     * @param values New elements
     * @throws Exception
     */
    void update(List<T> values) throws Exception;
}

/**
 * State that holds a key-value map
 * @param <UK> Type of user keys
 * @param <UV> Type of user values
 */
interface MapState<UK, UV> extends State {
    /**
     * Get value for the given key
     * @param key User key
     * @return Value for the key, null if not present
     * @throws Exception
     */
    UV get(UK key) throws Exception;
    
    /**
     * Associate value with key
     * @param key User key
     * @param value User value
     * @throws Exception
     */
    void put(UK key, UV value) throws Exception;
    
    /**
     * Add all key-value pairs from map
     * @param map Key-value pairs to add
     * @throws Exception
     */
    void putAll(Map<UK, UV> map) throws Exception;
    
    /**
     * Remove key-value pair
     * @param key Key to remove
     * @throws Exception
     */
    void remove(UK key) throws Exception;
    
    /**
     * Check if key exists
     * @param key Key to check
     * @return true if key exists
     * @throws Exception
     */
    boolean contains(UK key) throws Exception;
    
    /**
     * Get all entries
     * @return Iterable over all entries
     * @throws Exception
     */
    Iterable<Map.Entry<UK, UV>> entries() throws Exception;
    
    /**
     * Get all keys
     * @return Iterable over all keys
     * @throws Exception
     */
    Iterable<UK> keys() throws Exception;
    
    /**
     * Get all values
     * @return Iterable over all values
     * @throws Exception
     */
    Iterable<UV> values() throws Exception;
    
    /**
     * Check if state is empty
     * @return true if no entries
     * @throws Exception
     */
    boolean isEmpty() throws Exception;
}

/**
 * State for pre-aggregating values using AggregateFunction
 * @param <IN> Input type
 * @param <OUT> Output type
 */
interface AggregatingState<IN, OUT> extends State {
    /**
     * Get current aggregated result
     * @return Aggregated result
     * @throws Exception
     */
    OUT get() throws Exception;
    
    /**
     * Add value to aggregation
     * @param value Value to add
     * @throws Exception
     */
    void add(IN value) throws Exception;
}

/**
 * State that reduces values on-the-fly using ReduceFunction
 * @param <T> Element type
 */
interface ReducingState<T> extends State {
    /**
     * Get current reduced result
     * @return Reduced result
     * @throws Exception
     */
    T get() throws Exception;
    
    /**
     * Add value to reduction
     * @param value Value to add
     * @throws Exception
     */
    void add(T value) throws Exception;
}

/**
 * State for broadcast patterns - read-only for non-broadcast stream
 * @param <K> Key type
 * @param <V> Value type
 */
interface BroadcastState<K, V> extends State {
    /**
     * Get value for key (read-only for non-broadcast stream)
     * @param key Key to lookup
     * @return Value for key
     * @throws Exception
     */
    V get(K key) throws Exception;
    
    /**
     * Check if key exists (read-only for non-broadcast stream)
     * @param key Key to check
     * @return true if key exists
     * @throws Exception
     */
    boolean contains(K key) throws Exception;
    
    /**
     * Get all entries (read-only for non-broadcast stream)
     * @return Iterable over all entries
     * @throws Exception
     */
    Iterable<Map.Entry<K, V>> entries() throws Exception;
    
    /**
     * Get all keys (read-only for non-broadcast stream)
     * @return Iterable over all keys
     * @throws Exception
     */
    Iterable<K> keys() throws Exception;
    
    /**
     * Get all values (read-only for non-broadcast stream)
     * @return Iterable over all values
     * @throws Exception
     */
    Iterable<V> values() throws Exception;
    
    // Write operations available only in broadcast stream processing functions
    
    /**
     * Associate value with key (broadcast stream only)
     * @param key Key
     * @param value Value
     * @throws Exception
     */
    void put(K key, V value) throws Exception;
    
    /**
     * Add all key-value pairs (broadcast stream only)
     * @param map Key-value pairs to add
     * @throws Exception
     */
    void putAll(Map<K, V> map) throws Exception;
    
    /**
     * Remove key-value pair (broadcast stream only)
     * @param key Key to remove
     * @throws Exception
     */
    void remove(K key) throws Exception;
}

/**
 * Base descriptor for state variables
 * @param <S> State type
 * @param <T> Value type
 */
abstract class StateDescriptor<S extends State, T> {
    /**
     * Get state name
     * @return State name
     */
    public String getName();
    
    /**
     * Get type information
     * @return Type information
     */
    public TypeInformation<T> getTypeInformation();
    
    /**
     * Set default value
     * @param defaultValue Default value
     */
    public void setDefaultValue(T defaultValue);
    
    /**
     * Get default value
     * @return Default value
     */
    public T getDefaultValue();
}

/**
 * Descriptor for ValueState
 * @param <T> Value type
 */
class ValueStateDescriptor<T> extends StateDescriptor<ValueState<T>, T> {
    /**
     * Create descriptor with name and type information
     * @param name State name
     * @param typeInfo Type information
     */
    public ValueStateDescriptor(String name, TypeInformation<T> typeInfo);
    
    /**
     * Create descriptor with name and type class
     * @param name State name
     * @param typeClass Type class
     */
    public ValueStateDescriptor(String name, Class<T> typeClass);
}

/**
 * Descriptor for ListState
 * @param <T> Element type
 */
class ListStateDescriptor<T> extends StateDescriptor<ListState<T>, List<T>> {
    /**
     * Create descriptor with name and element type information
     * @param name State name
     * @param elementTypeInfo Element type information
     */
    public ListStateDescriptor(String name, TypeInformation<T> elementTypeInfo);
    
    /**
     * Create descriptor with name and element type class
     * @param name State name
     * @param elementTypeClass Element type class
     */
    public ListStateDescriptor(String name, Class<T> elementTypeClass);
}

/**
 * Descriptor for MapState
 * @param <UK> User key type
 * @param <UV> User value type
 */
class MapStateDescriptor<UK, UV> extends StateDescriptor<MapState<UK, UV>, Map<UK, UV>> {
    /**
     * Create descriptor with name and type information
     * @param name State name
     * @param keyTypeInfo Key type information
     * @param valueTypeInfo Value type information
     */
    public MapStateDescriptor(String name, TypeInformation<UK> keyTypeInfo, TypeInformation<UV> valueTypeInfo);
    
    /**
     * Create descriptor with name and type classes
     * @param name State name
     * @param keyTypeClass Key type class
     * @param valueTypeClass Value type class
     */
    public MapStateDescriptor(String name, Class<UK> keyTypeClass, Class<UV> valueTypeClass);
}

/**
 * Descriptor for AggregatingState
 * @param <IN> Input type
 * @param <ACC> Accumulator type
 * @param <OUT> Output type
 */
class AggregatingStateDescriptor<IN, ACC, OUT> extends StateDescriptor<AggregatingState<IN, OUT>, ACC> {
    /**
     * Create descriptor with name, aggregate function, and accumulator type
     * @param name State name
     * @param aggFunction Aggregate function
     * @param accTypeInfo Accumulator type information
     */
    public AggregatingStateDescriptor(String name, AggregateFunction<IN, ACC, OUT> aggFunction, TypeInformation<ACC> accTypeInfo);
}

/**
 * Descriptor for ReducingState
 * @param <T> Element type
 */
class ReducingStateDescriptor<T> extends StateDescriptor<ReducingState<T>, T> {
    /**
     * Create descriptor with name, reduce function, and type information
     * @param name State name
     * @param reduceFunction Reduce function
     * @param typeInfo Type information
     */
    public ReducingStateDescriptor(String name, ReduceFunction<T> reduceFunction, TypeInformation<T> typeInfo);
}

/**
 * Base interface for async state API
 */
interface org.apache.flink.api.common.state.v2.State {
    /**
     * Clear the state asynchronously
     * @return Future representing completion
     */
    StateFuture<Void> asyncClear();
}

/**
 * Async single value state
 * @param <T> Value type
 */
interface org.apache.flink.api.common.state.v2.ValueState<T> extends org.apache.flink.api.common.state.v2.State {
    /**
     * Get current value asynchronously
     * @return Future with current value
     */
    StateFuture<T> asyncValue();
    
    /**
     * Update state value asynchronously
     * @param value New value
     * @return Future representing completion
     */
    StateFuture<Void> asyncUpdate(T value);
}

/**
 * Async list state
 * @param <T> Element type
 */
interface org.apache.flink.api.common.state.v2.ListState<T> extends org.apache.flink.api.common.state.v2.State {
    /**
     * Get all elements asynchronously
     * @return Future with iterable over elements
     */
    StateFuture<Iterable<T>> asyncGet();
    
    /**
     * Add element asynchronously
     * @param value Element to add
     * @return Future representing completion
     */
    StateFuture<Void> asyncAdd(T value);
    
    /**
     * Update list asynchronously
     * @param values New elements
     * @return Future representing completion
     */
    StateFuture<Void> asyncUpdate(List<T> values);
}

/**
 * Async map state
 * @param <UK> User key type
 * @param <UV> User value type
 */
interface org.apache.flink.api.common.state.v2.MapState<UK, UV> extends org.apache.flink.api.common.state.v2.State {
    /**
     * Get value for key asynchronously
     * @param key User key
     * @return Future with value
     */
    StateFuture<UV> asyncGet(UK key);
    
    /**
     * Put key-value pair asynchronously
     * @param key User key
     * @param value User value
     * @return Future representing completion
     */
    StateFuture<Void> asyncPut(UK key, UV value);
    
    /**
     * Remove key asynchronously
     * @param key Key to remove
     * @return Future representing completion
     */
    StateFuture<Void> asyncRemove(UK key);
    
    /**
     * Check if key exists asynchronously
     * @param key Key to check
     * @return Future with boolean result
     */
    StateFuture<Boolean> asyncContains(UK key);
    
    /**
     * Get all entries asynchronously
     * @return Future with iterable over entries
     */
    StateFuture<Iterable<Map.Entry<UK, UV>>> asyncEntries();
}

/**
 * Future type for async state operations
 * @param <T> Result type
 */
interface StateFuture<T> {
    /**
     * Apply function when future completes
     * @param fn Function to apply
     * @param <U> Function result type
     * @return New future with function result
     */
    <U> StateFuture<U> thenApply(Function<T, U> fn);
    
    /**
     * Compose with another async operation
     * @param fn Function returning another future
     * @param <U> Composed result type
     * @return Future representing composed operation
     */
    <U> StateFuture<U> thenCompose(Function<T, StateFuture<U>> fn);
    
    /**
     * Handle completion or exception
     * @param fn Handler function
     * @param <U> Handler result type
     * @return Future with handler result
     */
    <U> StateFuture<U> handle(BiFunction<T, Throwable, U> fn);
}

/**
 * Base interface for watermarks
 */
interface Watermark {
    /**
     * Get watermark timestamp
     * @return Timestamp
     */
    long getTimestamp();
    
    /**
     * Check if this is a special watermark (e.g., MAX_WATERMARK)
     * @return true if special watermark
     */
    boolean isSpecial();
}

/**
 * Long-based watermark implementation
 */
class LongWatermark implements Watermark {
    /**
     * Create watermark with timestamp
     * @param timestamp Watermark timestamp
     */
    public LongWatermark(long timestamp);
    
    @Override
    public long getTimestamp();
    
    @Override
    public boolean isSpecial();
    
    /** Maximum possible watermark value */
    public static final LongWatermark MAX_WATERMARK;
}

/**
 * Boolean-based watermark implementation
 */
class BoolWatermark implements Watermark {
    /**
     * Create boolean watermark
     * @param value Boolean value
     */
    public BoolWatermark(boolean value);
    
    /**
     * Get boolean value
     * @return Boolean value
     */
    public boolean getValue();
}

/**
 * Interface for watermark management
 */
interface WatermarkManager {
    /**
     * Update watermarks
     * @param watermarks New watermarks
     */
    void updateWatermarks(Collection<Watermark> watermarks);
    
    /**
     * Get current combined watermark
     * @return Current watermark
     */
    Watermark getCurrentWatermark();
}