DataStream API (New v2)

/**
 * Main entry point for DataStream programs using the new v2 API
 */
interface ExecutionEnvironment {
    /**
     * Create data stream from source
     * @param source Data source
     * @param <T> Element type
     * @return DataStream with elements from source
     */
    <T> DataStream<T> fromSource(Source<T> source);
    
    /**
     * Create data stream from collection
     * @param collection Collection of elements
     * @param <T> Element type
     * @return DataStream with elements from collection
     */
    <T> DataStream<T> fromCollection(Collection<T> collection);
    
    /**
     * Create data stream from elements
     * @param elements Varargs elements
     * @param <T> Element type
     * @return DataStream with provided elements
     */
    <T> DataStream<T> fromElements(T... elements);
    
    /**
     * Execute the streaming program
     * @return Job execution result
     */
    CompletableFuture<JobExecutionResult> execute();
    
    /**
     * Execute the streaming program with job name
     * @param jobName Name of the job
     * @return Job execution result
     */
    CompletableFuture<JobExecutionResult> execute(String jobName);
}

/**
 * Fundamental data stream interface
 * @param <T> Element type
 */
interface DataStream<T> {
    /**
     * Apply process function to transform elements
     * @param processFunction Process function
     * @param <OUT> Output type
     * @return Transformed stream
     */
    <OUT> DataStream<OUT> process(OneInputStreamProcessFunction<T, OUT> processFunction);
    
    /**
     * Partition stream by key
     * @param keySelector Key extraction function
     * @param <K> Key type
     * @return Keyed partitioned stream
     */
    <K> KeyedPartitionStream<K, T> keyBy(KeySelector<T, K> keySelector);
    
    /**
     * Connect with another stream for dual-input processing
     * @param other Other stream
     * @param <T2> Other stream element type
     * @return Connected streams
     */
    <T2> TwoInputConnectedStreams<T, T2> connectWith(DataStream<T2> other);
    
    /**
     * Broadcast stream to all parallel instances
     * @return Broadcast stream
     */
    BroadcastStream<T> broadcast();
    
    /**
     * Send all elements to single parallel instance
     * @return Global stream
     */
    GlobalStream<T> global();
    
    /**
     * Add sink to consume stream elements
     * @param sink Data sink
     * @return Sink transformation
     */
    DataStreamSink<T> sinkTo(Sink<T> sink);
}

/**
 * Keyed and partitioned stream for stateful operations
 * @param <K> Key type
 * @param <T> Element type
 */
interface KeyedPartitionStream<K, T> {
    /**
     * Apply keyed process function
     * @param processFunction Keyed process function
     * @param <OUT> Output type
     * @return Transformed stream
     */
    <OUT> DataStream<OUT> process(KeyedProcessFunction<K, T, OUT> processFunction);
    
    /**
     * Reduce elements by key using reduce function
     * @param reduceFunction Reduce function
     * @return Stream with reduced elements
     */
    DataStream<T> reduce(ReduceFunction<T> reduceFunction);
    
    /**
     * Aggregate elements by key using aggregate function
     * @param aggregateFunction Aggregate function
     * @param <ACC> Accumulator type
     * @param <OUT> Output type
     * @return Stream with aggregated elements
     */
    <ACC, OUT> DataStream<OUT> aggregate(AggregateFunction<T, ACC, OUT> aggregateFunction);
}

/**
 * Non-keyed partitioned stream
 * @param <T> Element type
 */
interface NonKeyedPartitionStream<T> {
    /**
     * Apply process function to stream
     * @param processFunction Process function
     * @param <OUT> Output type
     * @return Transformed stream
     */
    <OUT> DataStream<OUT> process(OneInputStreamProcessFunction<T, OUT> processFunction);
}

/**
 * Broadcast stream that sends elements to all parallel instances
 * @param <T> Element type
 */
interface BroadcastStream<T> {
    /**
     * Connect with keyed stream for broadcast processing
     * @param keyedStream Keyed stream
     * @param <K> Key type
     * @param <KS> Keyed stream element type
     * @return Broadcast connected stream
     */
    <K, KS> BroadcastConnectedStream<KS, T> connectWith(KeyedPartitionStream<K, KS> keyedStream);
    
    /**
     * Connect with non-keyed stream for broadcast processing
     * @param stream Non-keyed stream
     * @param <S> Stream element type
     * @return Broadcast connected stream
     */
    <S> BroadcastConnectedStream<S, T> connectWith(NonKeyedPartitionStream<S> stream);
}

/**
 * Global stream processed by single parallel instance
 * @param <T> Element type
 */
interface GlobalStream<T> {
    /**
     * Apply process function to global stream
     * @param processFunction Process function
     * @param <OUT> Output type
     * @return Transformed stream
     */
    <OUT> DataStream<OUT> process(OneInputStreamProcessFunction<T, OUT> processFunction);
}

/**
 * Base interface for process functions
 */
interface ProcessFunction {}

/**
 * Single input stream processing function
 * @param <IN> Input type
 * @param <OUT> Output type
 */
interface OneInputStreamProcessFunction<IN, OUT> extends ProcessFunction {
    /**
     * Process single element
     * @param element Input element
     * @param output Output collector
     * @param ctx Runtime context
     * @throws Exception
     */
    void processElement(IN element, Collector<OUT> output, RuntimeContext ctx) throws Exception;
    
    /**
     * Process timer event
     * @param timestamp Timer timestamp
     * @param output Output collector
     * @param ctx Runtime context
     * @throws Exception
     */
    default void onTimer(long timestamp, Collector<OUT> output, RuntimeContext ctx) throws Exception {}
}

/**
 * Key-aware process function for keyed streams
 * @param <K> Key type
 * @param <IN> Input type
 * @param <OUT> Output type
 */
interface KeyedProcessFunction<K, IN, OUT> extends ProcessFunction {
    /**
     * Process element with key context
     * @param element Input element
     * @param output Output collector
     * @param ctx Partitioned context with key access
     * @throws Exception
     */
    void processElement(IN element, Collector<OUT> output, PartitionedContext<K> ctx) throws Exception;
    
    /**
     * Process timer with key context
     * @param timestamp Timer timestamp
     * @param output Output collector
     * @param ctx Partitioned context with key access
     * @throws Exception
     */
    default void onTimer(long timestamp, Collector<OUT> output, PartitionedContext<K> ctx) throws Exception {}
}

/**
 * Dual input stream processing function (non-broadcast)
 * @param <IN1> First input type
 * @param <IN2> Second input type
 * @param <OUT> Output type
 */
interface TwoInputNonBroadcastStreamProcessFunction<IN1, IN2, OUT> extends ProcessFunction {
    /**
     * Process element from first input
     * @param element Element from first input
     * @param output Output collector
     * @param ctx Runtime context
     * @throws Exception
     */
    void processElement1(IN1 element, Collector<OUT> output, RuntimeContext ctx) throws Exception;
    
    /**
     * Process element from second input
     * @param element Element from second input
     * @param output Output collector
     * @param ctx Runtime context
     * @throws Exception
     */
    void processElement2(IN2 element, Collector<OUT> output, RuntimeContext ctx) throws Exception;
}

/**
 * Multi-output stream processing function
 * @param <IN> Input type
 * @param <OUT1> First output type
 * @param <OUT2> Second output type
 */
interface TwoOutputStreamProcessFunction<IN, OUT1, OUT2> extends ProcessFunction {
    /**
     * Process element producing multiple outputs
     * @param element Input element
     * @param output1 First output collector
     * @param output2 Second output collector
     * @param ctx Runtime context
     * @throws Exception
     */
    void processElement(IN element, Collector<OUT1> output1, Collector<OUT2> output2, RuntimeContext ctx) throws Exception;
}

/**
 * Runtime context for accessing runtime information
 */
interface RuntimeContext {
    /**
     * Get task name
     * @return Task name
     */
    String getTaskName();
    
    /**
     * Get parallelism of current operator
     * @return Parallelism
     */
    int getParallelism();
    
    /**
     * Get index of current parallel subtask
     * @return Subtask index
     */
    int getIndexOfThisSubtask();
    
    /**
     * Get processing time manager
     * @return Processing time manager
     */
    ProcessingTimeManager getProcessingTimeManager();
    
    /**
     * Get state manager
     * @return State manager
     */
    StateManager getStateManager();
}

/**
 * Context for partitioned (keyed) processing
 * @param <K> Key type
 */
interface PartitionedContext<K> extends RuntimeContext {
    /**
     * Get current key
     * @return Current processing key
     */
    K getCurrentKey();
    
    /**
     * Get keyed state manager
     * @return Keyed state manager
     */
    KeyedStateManager getKeyedStateManager();
}

/**
 * Interface for state management
 */
interface StateManager {
    /**
     * Get value state
     * @param descriptor State descriptor
     * @param <T> Value type
     * @return Value state
     */
    <T> ValueState<T> getState(ValueStateDescriptor<T> descriptor);
    
    /**
     * Get list state
     * @param descriptor State descriptor
     * @param <T> Element type
     * @return List state
     */
    <T> ListState<T> getListState(ListStateDescriptor<T> descriptor);
    
    /**
     * Get map state
     * @param descriptor State descriptor
     * @param <UK> User key type
     * @param <UV> User value type
     * @return Map state
     */
    <UK, UV> MapState<UK, UV> getMapState(MapStateDescriptor<UK, UV> descriptor);
}

/**
 * Interface for keyed state management
 */
interface KeyedStateManager extends StateManager {
    /**
     * Get reducing state
     * @param descriptor State descriptor
     * @param <T> Element type
     * @return Reducing state
     */
    <T> ReducingState<T> getReducingState(ReducingStateDescriptor<T> descriptor);
    
    /**
     * Get aggregating state
     * @param descriptor State descriptor
     * @param <IN> Input type
     * @param <ACC> Accumulator type
     * @param <OUT> Output type
     * @return Aggregating state
     */
    <IN, ACC, OUT> AggregatingState<IN, OUT> getAggregatingState(AggregatingStateDescriptor<IN, ACC, OUT> descriptor);
}

/**
 * Interface for processing time management
 */
interface ProcessingTimeManager {
    /**
     * Get current processing time
     * @return Current processing time timestamp
     */
    long getCurrentProcessingTime();
    
    /**
     * Register processing time timer
     * @param timestamp Timer timestamp
     */
    void registerTimer(long timestamp);
    
    /**
     * Delete processing time timer
     * @param timestamp Timer timestamp
     */
    void deleteTimer(long timestamp);
}

/**
 * Base window strategy interface
 * @param <W> Window type
 */
interface WindowStrategy<W> {
    /**
     * Assign windows to element
     * @param element Element to assign windows to
     * @param timestamp Element timestamp
     * @return Collection of windows
     */
    Collection<W> assignWindows(Object element, long timestamp);
    
    /**
     * Get window serializer
     * @return Window serializer
     */
    TypeSerializer<W> getWindowSerializer();
}

/**
 * Tumbling time window strategy
 */
class TumblingTimeWindowStrategy implements WindowStrategy<TimeWindow> {
    /**
     * Create tumbling time windows with specified size
     * @param size Window size
     * @return Tumbling window strategy
     */
    public static TumblingTimeWindowStrategy of(Duration size);
    
    /**
     * Create tumbling time windows with size and offset
     * @param size Window size
     * @param offset Window offset
     * @return Tumbling window strategy
     */
    public static TumblingTimeWindowStrategy of(Duration size, Duration offset);
}

/**
 * Sliding time window strategy
 */
class SlidingTimeWindowStrategy implements WindowStrategy<TimeWindow> {
    /**
     * Create sliding time windows with size and slide
     * @param size Window size
     * @param slide Slide interval
     * @return Sliding window strategy
     */
    public static SlidingTimeWindowStrategy of(Duration size, Duration slide);
    
    /**
     * Create sliding time windows with size, slide, and offset
     * @param size Window size
     * @param slide Slide interval
     * @param offset Window offset
     * @return Sliding window strategy
     */
    public static SlidingTimeWindowStrategy of(Duration size, Duration slide, Duration offset);
}

/**
 * Session window strategy
 */
class SessionWindowStrategy implements WindowStrategy<TimeWindow> {
    /**
     * Create session windows with inactivity gap
     * @param gap Inactivity gap
     * @return Session window strategy
     */
    public static SessionWindowStrategy withGap(Duration gap);
}

/**
 * Time window implementation
 */
class TimeWindow {
    /**
     * Get window start time
     * @return Start timestamp
     */
    public long getStart();
    
    /**
     * Get window end time
     * @return End timestamp
     */
    public long getEnd();
    
    /**
     * Get window maximum timestamp
     * @return Maximum timestamp
     */
    public long maxTimestamp();
    
    /**
     * Check if window contains timestamp
     * @param timestamp Timestamp to check
     * @return true if timestamp is in window
     */
    public boolean contains(long timestamp);
}

/**
 * Event time extension for DataStream API v2
 */
class EventTimeExtension {
    /**
     * Enable event time processing for stream
     * @param stream Input stream
     * @param <T> Element type
     * @return Stream with event time support
     */
    public static <T> DataStream<T> withEventTime(DataStream<T> stream);
    
    /**
     * Assign timestamps and watermarks
     * @param stream Input stream
     * @param timestampAssigner Timestamp assigner
     * @param <T> Element type
     * @return Stream with timestamps and watermarks
     */
    public static <T> DataStream<T> assignTimestampsAndWatermarks(
        DataStream<T> stream, 
        TimestampAssigner<T> timestampAssigner
    );
}

/**
 * Interface for event time management
 */
interface EventTimeManager {
    /**
     * Get current event time
     * @return Current event time
     */
    long getCurrentEventTime();
    
    /**
     * Register event time timer
     * @param timestamp Timer timestamp
     */
    void registerTimer(long timestamp);
    
    /**
     * Delete event time timer
     * @param timestamp Timer timestamp
     */
    void deleteTimer(long timestamp);
}

/**
 * Interface for assigning timestamps to elements
 * @param <T> Element type
 */
interface TimestampAssigner<T> {
    /**
     * Extract timestamp from element
     * @param element Element
     * @param recordTimestamp Record timestamp
     * @return Element timestamp
     */
    long extractTimestamp(T element, long recordTimestamp);
}