Utility Classes

/**
 * Utilities for working with Timestamp messages
 */
public final class Timestamps {
    // Constants for common timestamp values
    /** Minimum valid timestamp (0001-01-01T00:00:00Z) */
    public static final Timestamp MIN_VALUE;
    
    /** Maximum valid timestamp (9999-12-31T23:59:59.999999999Z) */
    public static final Timestamp MAX_VALUE;
    
    /** Epoch timestamp (1970-01-01T00:00:00.000000000Z) */
    public static final Timestamp EPOCH;
    
    // Comparison utilities
    /** Returns timestamp comparator for sorting */
    public static Comparator<Timestamp> comparator();
    
    /** Compares two timestamps (-1, 0, or 1) */
    public static int compare(Timestamp x, Timestamp y);
    
    // Validation methods
    /** Validates timestamp is within valid range */
    public static boolean isValid(Timestamp timestamp);
    
    /** Validates and returns timestamp, throws exception if invalid */
    public static Timestamp checkValid(Timestamp timestamp) throws IllegalArgumentException;
    
    // Conversion from time units to Timestamp
    /** Creates timestamp from milliseconds since Unix epoch */
    public static Timestamp fromMillis(long millis);
    
    /** Creates timestamp from microseconds since Unix epoch */
    public static Timestamp fromMicros(long micros);
    
    /** Creates timestamp from nanoseconds since Unix epoch */
    public static Timestamp fromNanos(long nanos);
    
    // Conversion from Timestamp to time units
    /** Converts timestamp to milliseconds since Unix epoch */
    public static long toMillis(Timestamp timestamp);
    
    /** Converts timestamp to microseconds since Unix epoch */
    public static long toMicros(Timestamp timestamp);
    
    /** Converts timestamp to nanoseconds since Unix epoch */
    public static long toNanos(Timestamp timestamp);
    
    // Arithmetic operations
    /** Adds duration to timestamp */
    public static Timestamp add(Timestamp timestamp, Duration duration);
    
    /** Subtracts duration from timestamp */
    public static Timestamp subtract(Timestamp timestamp, Duration duration);
    
    /** Calculates duration between two timestamps */
    public static Duration between(Timestamp from, Timestamp to);
    
    // String representation
    /** Converts timestamp to RFC 3339 string format */
    public static String toString(Timestamp timestamp);
    
    /** Parses RFC 3339 timestamp string */
    public static Timestamp parseTimestamp(String value) throws ParseException;
}

/**
 * Utilities for working with Duration messages
 */
public final class Durations {
    // Constants for common duration values
    /** Minimum valid duration (approximately -10,000 years) */
    public static final Duration MIN_VALUE;
    
    /** Maximum valid duration (approximately +10,000 years) */
    public static final Duration MAX_VALUE;
    
    /** Duration of zero */
    public static final Duration ZERO;
    
    // Comparison utilities
    /** Returns duration comparator for sorting */
    public static Comparator<Duration> comparator();
    
    /** Compares two durations (-1, 0, or 1) */
    public static int compare(Duration x, Duration y);
    
    // Validation methods
    /** Validates duration is within valid range */
    public static boolean isValid(Duration duration);
    
    /** Validates and returns duration, throws exception if invalid */
    public static Duration checkValid(Duration duration) throws IllegalArgumentException;
    
    // Conversion from time units to Duration
    /** Creates duration from milliseconds */
    public static Duration fromMillis(long millis);
    
    /** Creates duration from microseconds */
    public static Duration fromMicros(long micros);
    
    /** Creates duration from nanoseconds */
    public static Duration fromNanos(long nanos);
    
    /** Creates duration from seconds */
    public static Duration fromSeconds(long seconds);
    
    /** Creates duration from minutes */
    public static Duration fromMinutes(long minutes);
    
    /** Creates duration from hours */
    public static Duration fromHours(long hours);
    
    /** Creates duration from days */
    public static Duration fromDays(long days);
    
    // Conversion from Duration to time units
    /** Converts duration to total milliseconds */
    public static long toMillis(Duration duration);
    
    /** Converts duration to total microseconds */
    public static long toMicros(Duration duration);
    
    /** Converts duration to total nanoseconds */
    public static long toNanos(Duration duration);
    
    /** Converts duration to total seconds */
    public static long toSeconds(Duration duration);
    
    /** Converts duration to total minutes */
    public static long toMinutes(Duration duration);
    
    /** Converts duration to total hours */
    public static long toHours(Duration duration);
    
    /** Converts duration to total days */
    public static long toDays(Duration duration);
    
    // Arithmetic operations
    /** Adds two durations */
    public static Duration add(Duration d1, Duration d2);
    
    /** Subtracts second duration from first */
    public static Duration subtract(Duration d1, Duration d2);
    
    /** Multiplies duration by scalar */
    public static Duration multiply(Duration duration, long times);
    
    /** Multiplies duration by double scalar */
    public static Duration multiply(Duration duration, double times);
    
    /** Divides duration by scalar */
    public static Duration divide(Duration duration, long times);
    
    /** Divides duration by double scalar */
    public static Duration divide(Duration duration, double times);
    
    /** Returns absolute value of duration */
    public static Duration abs(Duration duration);
    
    /** Negates duration */
    public static Duration negate(Duration duration);
    
    // String representation
    /** Converts duration to string representation (e.g., "1.500s", "2m30s") */
    public static String toString(Duration duration);
    
    /** Parses duration string (e.g., "1s", "2.5s", "1m30s") */
    public static Duration parseDuration(String value) throws ParseException;
}

/**
 * Utilities for working with FieldMask messages
 */
public final class FieldMaskUtil {
    // String conversion methods
    /** Converts FieldMask to comma-separated string */
    public static String toString(FieldMask fieldMask);
    
    /** Parses FieldMask from comma-separated string */
    public static FieldMask fromString(String value);
    
    /** Parses and validates FieldMask for specific message type */
    public static FieldMask fromString(Class<? extends Message> type, String value);
    
    // List-based creation methods
    /** Creates FieldMask from field path strings with type validation */
    public static FieldMask fromStringList(Class<? extends Message> type, Iterable<String> paths);
    
    /** Creates FieldMask from field paths using message descriptor */
    public static FieldMask fromStringList(Descriptor descriptor, Iterable<String> paths);
    
    /** Creates FieldMask from field paths without validation */
    public static FieldMask fromStringList(Iterable<String> paths);
    
    /** Creates FieldMask from field numbers */
    public static FieldMask fromFieldNumbers(Class<? extends Message> type, int... fieldNumbers);
    
    // Set operations on field masks
    /** Computes union of multiple field masks */
    public static FieldMask union(FieldMask mask1, FieldMask mask2, FieldMask... otherMasks);
    
    /** Computes intersection of two field masks */
    public static FieldMask intersection(FieldMask mask1, FieldMask mask2);
    
    /** Subtracts second mask from first mask */
    public static FieldMask subtract(FieldMask mask1, FieldMask mask2);
    
    // Validation methods
    /** Validates FieldMask paths for message type */
    public static boolean isValid(Class<? extends Message> type, FieldMask fieldMask);
    
    /** Validates FieldMask paths using message descriptor */
    public static boolean isValid(Descriptor descriptor, FieldMask fieldMask);
    
    // Field mask operations
    /** Merges fields specified by mask from source to destination */
    public static void merge(FieldMask mask, Message source, Message.Builder destination);
    
    /** Merges fields specified by mask with merge options */
    public static void merge(FieldMask mask, Message source, Message.Builder destination, MergeOptions options);
    
    /** Copies fields specified by mask from source to destination builder */
    public static void copy(FieldMask mask, Message source, Message.Builder destination);
    
    // Utility methods
    /** Checks if field mask is valid for given message type */
    public static void normalize(FieldMask.Builder maskBuilder);
    
    /** Gets all field paths that would be affected by the mask */
    public static Set<String> getFieldPathSet(FieldMask fieldMask);
    
    /**
     * Options for field mask merge operations
     */
    public static class MergeOptions {
        /** Whether to replace repeated fields entirely or merge them */
        public MergeOptions setReplaceRepeatedFields(boolean replaceRepeatedFields);
        
        /** Whether to replace message fields entirely or merge them */
        public MergeOptions setReplaceMessageFields(boolean replaceMessageFields);
        
        /** Whether to replace primitive fields */
        public MergeOptions setReplacePrimitiveFields(boolean replacePrimitiveFields);
    }
}

/**
 * Utilities for creating Struct messages
 */
public final class Structs {
    /** Creates struct with one key-value pair */
    public static Struct of(String k1, Value v1);
    
    /** Creates struct with two key-value pairs */
    public static Struct of(String k1, Value v1, String k2, Value v2);
    
    /** Creates struct with three key-value pairs */
    public static Struct of(String k1, Value v1, String k2, Value v2, String k3, Value v3);
    
    /** Creates struct with four key-value pairs */
    public static Struct of(String k1, Value v1, String k2, Value v2, String k3, Value v3, String k4, Value v4);
    
    /** Creates struct with five key-value pairs */
    public static Struct of(String k1, Value v1, String k2, Value v2, String k3, Value v3, String k4, Value v4, String k5, Value v5);
}

/**
 * Utilities for creating Value messages
 */
public final class Values {
    /** Creates null value */
    public static Value ofNull();
    
    /** Creates boolean value */
    public static Value of(boolean value);
    
    /** Creates number value from double */
    public static Value of(double value);
    
    /** Creates number value from int */
    public static Value of(int value);
    
    /** Creates number value from long */
    public static Value of(long value);
    
    /** Creates string value */
    public static Value of(String value);
    
    /** Creates struct value */
    public static Value of(Struct value);
    
    /** Creates list value */
    public static Value of(ListValue value);
    
    /** Creates list value from Value iterable */
    public static Value of(Iterable<Value> values);
    
    /** Creates list value from mixed objects (converted to Values) */
    public static Value ofList(Object... values);
}

/**
 * Utilities for working with Any messages
 */
public final class Any {
    /** Packs message into Any */
    public static Any pack(Message message);
    
    /** Packs message into Any with custom type URL prefix */
    public static Any pack(Message message, String typeUrlPrefix);
    
    /** Unpacks Any to specific message type */
    public static <T extends Message> T unpack(Any any, Class<T> clazz) throws InvalidProtocolBufferException;
    
    /** Checks if Any contains message of specific type */
    public static <T extends Message> boolean is(Any any, Class<T> clazz);
    
    /** Gets type URL from Any */
    public static String getTypeUrl(Any any);
    
    /** Gets type name from type URL */
    public static String getTypeName(String typeUrl);
    
    /** Creates type URL from type name */
    public static String getTypeUrl(String typeUrlPrefix, Descriptor descriptor);
}

import com.google.protobuf.util.*;
import com.google.protobuf.*;
import java.time.Instant;

// Working with timestamps
Timestamp now = Timestamps.fromMillis(System.currentTimeMillis());
Timestamp epoch = Timestamps.EPOCH;
Timestamp future = Timestamps.add(now, Durations.fromHours(24));

// Timestamp comparisons and validation
if (Timestamps.compare(now, future) < 0) {
    System.out.println("Now is before future");
}

if (Timestamps.isValid(now)) {
    String rfc3339 = Timestamps.toString(now);
    System.out.println("Timestamp: " + rfc3339);
}

// Working with durations
Duration oneHour = Durations.fromHours(1);
Duration thirtyMinutes = Durations.fromMinutes(30);
Duration totalTime = Durations.add(oneHour, thirtyMinutes);

long totalSeconds = Durations.toSeconds(totalTime);
System.out.println("Total seconds: " + totalSeconds);

// Working with field masks
FieldMask mask = FieldMaskUtil.fromString("name,email,profile.age");
FieldMask nameMask = FieldMaskUtil.fromStringList(Arrays.asList("name", "email"));

// Merge specific fields from one message to another
MyMessage source = MyMessage.newBuilder()
    .setName("John")
    .setEmail("john@example.com")
    .setAge(30)
    .build();

MyMessage.Builder target = MyMessage.newBuilder();
FieldMaskUtil.merge(nameMask, source, target);
MyMessage result = target.build(); // Only has name and email fields

// Working with Struct and Value
Struct jsonStruct = Structs.of(
    "name", Values.of("John Doe"),
    "age", Values.of(30),
    "active", Values.of(true)
);

Value listValue = Values.of(Arrays.asList(
    Values.of("item1"),
    Values.of("item2"),
    Values.of(42)
));

// Working with Any messages
MyMessage originalMessage = MyMessage.newBuilder()
    .setName("Test")
    .build();

Any packedMessage = Any.pack(originalMessage);
System.out.println("Type URL: " + Any.getTypeUrl(packedMessage));

if (Any.is(packedMessage, MyMessage.class)) {
    MyMessage unpacked = Any.unpack(packedMessage, MyMessage.class);
    System.out.println("Unpacked name: " + unpacked.getName());
}

// Field mask path examples:
// "name" - selects top-level name field
// "user.name" - selects name field within user message
// "user.address.street" - selects street field within nested address
// "items" - selects entire repeated field
// "user.phone_numbers" - selects repeated phone_numbers field
// "map_field" - selects entire map field
// "map_field.key" - selects specific map entry (not standard, use with caution)

// Complex field mask examples:
FieldMask complexMask = FieldMaskUtil.fromString(
    "user.name,user.email,user.profile.age,settings.notifications,items"
);

// Field mask operations:
FieldMask mask1 = FieldMaskUtil.fromString("name,email");
FieldMask mask2 = FieldMaskUtil.fromString("email,age");

FieldMask union = FieldMaskUtil.union(mask1, mask2); // "name,email,age"
FieldMask intersection = FieldMaskUtil.intersection(mask1, mask2); // "email"
FieldMask difference = FieldMaskUtil.subtract(mask1, mask2); // "name"

// Timestamp conversions
Instant javaInstant = Instant.ofEpochMilli(Timestamps.toMillis(timestamp));
Timestamp fromInstant = Timestamps.fromMillis(javaInstant.toEpochMilli());

// Duration conversions  
java.time.Duration javaDuration = java.time.Duration.ofMillis(Durations.toMillis(protoDuration));
Duration fromJavaDuration = Durations.fromMillis(javaDuration.toMillis());

// Struct/Value to JSON-like operations
Map<String, Object> javaMap = convertStructToMap(struct);
Object javaValue = convertValueToObject(value);
List<Object> javaList = convertListValueToList(listValue);

// Helper methods for conversions (not part of API, but common patterns)
public static Map<String, Object> convertStructToMap(Struct struct) {
    Map<String, Object> map = new HashMap<>();
    for (Map.Entry<String, Value> entry : struct.getFieldsMap().entrySet()) {
        map.put(entry.getKey(), convertValueToObject(entry.getValue()));
    }
    return map;
}

public static Object convertValueToObject(Value value) {
    switch (value.getKindCase()) {
        case NULL_VALUE: return null;
        case BOOL_VALUE: return value.getBoolValue();
        case NUMBER_VALUE: return value.getNumberValue();
        case STRING_VALUE: return value.getStringValue();
        case STRUCT_VALUE: return convertStructToMap(value.getStructValue());
        case LIST_VALUE: return convertListValueToList(value.getListValue());
        default: throw new IllegalArgumentException("Unknown value type");
    }
}

// Timestamp/Duration validation errors
try {
    Timestamp invalid = Timestamps.checkValid(someTimestamp);
} catch (IllegalArgumentException e) {
    // Handle invalid timestamp (out of range, invalid seconds/nanos)
}

// Parse exceptions for string formats
try {
    Timestamp parsed = Timestamps.parseTimestamp("invalid-format");
} catch (ParseException e) {
    // Handle invalid RFC 3339 format
}

try {
    Duration parsed = Durations.parseDuration("invalid-duration");
} catch (ParseException e) {
    // Handle invalid duration format
}

// Field mask validation errors
try {
    FieldMask mask = FieldMaskUtil.fromString(MyMessage.class, "invalid.field.path");
} catch (IllegalArgumentException e) {
    // Handle invalid field path for message type
}

// Any message unpacking errors
try {
    MyMessage unpacked = Any.unpack(anyMessage, MyMessage.class);
} catch (InvalidProtocolBufferException e) {
    // Handle type mismatch or malformed Any message
}

// Exception types for parsing
public class ParseException extends Exception {
    public ParseException(String message);
    public ParseException(String message, Throwable cause);
}

// Well-known type message classes (defined in well-known type .proto files)
public final class Timestamp extends GeneratedMessage { /* ... */ }
public final class Duration extends GeneratedMessage { /* ... */ }
public final class FieldMask extends GeneratedMessage { /* ... */ }
public final class Struct extends GeneratedMessage { /* ... */ }
public final class Value extends GeneratedMessage { /* ... */ }
public final class ListValue extends GeneratedMessage { /* ... */ }
public final class Any extends GeneratedMessage { /* ... */ }
public final class NullValue extends GeneratedMessage { /* ... */ }

// Utility helper classes (internal)
public final class FieldMaskTree {
    // Internal tree structure for efficient field mask operations
}