Protobuf fake data generator

using System; using System.Collections.Generic; using System.Linq; using Google.Protobuf; using Google.Protobuf.Reflection; using Google.Protobuf.Collections; using Google.Protobuf.WellKnownTypes; using System.Collections; public class ProtobufFaker { private readonly Random _random; private readonly int _maxCollectionSize; private readonly int _stringMaxLength; public ProtobufFaker(int? seed = null, int maxCollectionSize = 5, int stringMaxLength = 20) { _random = seed.HasValue ? new Random(seed.Value) : new Random(); _maxCollectionSize = maxCollectionSize; _stringMaxLength = stringMaxLength; } public T Generate<T>() where T : IMessage, new() { var message = new T(); PopulateMessage(message); return message; } public void PopulateMessage(IMessage message) { var descriptor = message.Descriptor; foreach (var fieldDescriptor in descriptor.Fields.InDeclarationOrder()) { if (fieldDescriptor.IsRepeated) { var list = (IList)fieldDescriptor.Accessor.GetValue(message); var count = _random.Next(1, _maxCollectionSize + 1); for (int i = 0; i < count; i++) { var value = GenerateSingleValue(fieldDescriptor); if (value != null) { list.Add(value); } } } else { var value = GenerateFieldValue(fieldDescriptor); if (value != null) { fieldDescriptor.Accessor.SetValue(message, value); } } } } private object? GenerateFieldValue(FieldDescriptor field) { if (field.IsMap) { return GenerateMapField(field); } // Handle oneof fields if (field.ContainingOneof != null) { // Randomly decide whether to set this oneof field if (_random.Next(2) == 0) { return null; } } return GenerateSingleValue(field); } private object? GenerateSingleValue(FieldDescriptor field) { if (field.FieldType == FieldType.Message && field.MessageType.FullName == "google.protobuf.Timestamp") { return GenerateTimestamp(); } return field.FieldType switch { FieldType.Double => _random.NextDouble() * 1000, FieldType.Float => (float)(_random.NextDouble() * 1000), FieldType.Int64 or FieldType.SInt64 or FieldType.SFixed64 => (long)_random.Next(1, 1000), FieldType.UInt64 or FieldType.Fixed64 => (ulong)_random.Next(1, 1000), FieldType.Int32 or FieldType.SInt32 or FieldType.SFixed32 => _random.Next(1, 1000), FieldType.Fixed32 or FieldType.UInt32 => (uint)_random.Next(1, 1000), FieldType.Bool => _random.Next(2) == 1, FieldType.String => GenerateRandomString(), FieldType.Bytes => GenerateRandomBytes(), FieldType.Enum => GenerateEnumValue(field.EnumType), FieldType.Message => GenerateNestedMessage(field.MessageType), _ => null, }; } private object? GenerateMapField(FieldDescriptor field) { var count = _random.Next(1, _maxCollectionSize + 1); var mapField = field.Accessor.GetValue((IMessage?)Activator.CreateInstance(field.ContainingType.ClrType)); var mapDescriptor = field.MessageType; var keyDescriptor = mapDescriptor.FindFieldByNumber(1); // Key is always field 1 var valueDescriptor = mapDescriptor.FindFieldByNumber(2); // Value is always field 2 var addMethod = mapField.GetType().GetMethod("Add"); if (addMethod == null) { return null; } for (int i = 0; i < count; i++) { var key = GenerateSingleValue(keyDescriptor); var value = GenerateSingleValue(valueDescriptor); if (key != null && value != null) { addMethod.Invoke(mapField, [key, value]); } } return mapField; } private IMessage? GenerateNestedMessage(MessageDescriptor messageDescriptor) { var message = (IMessage?)Activator.CreateInstance(messageDescriptor.ClrType); if (message == null) { return null; } PopulateMessage(message); return message; } private object GenerateEnumValue(EnumDescriptor enumDescriptor) { var values = enumDescriptor.Values; var randomIndex = _random.Next(values.Count); return values[randomIndex].Number; } private Timestamp GenerateTimestamp() { var now = DateTime.UtcNow; var daysOffset = _random.Next(-365 * 2, 365 * 2); // ±2 years from now var hoursOffset = _random.Next(-24, 24); var minutesOffset = _random.Next(-60, 60); var randomTime = now .AddDays(daysOffset) .AddHours(hoursOffset) .AddMinutes(minutesOffset); return Timestamp.FromDateTime(randomTime); } private string GenerateRandomString() { const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"; var length = _random.Next(1, _stringMaxLength + 1); return new string(Enumerable.Repeat(chars, length) .Select(s => s[_random.Next(s.Length)]).ToArray()); } private ByteString GenerateRandomBytes() { var length = _random.Next(1, _stringMaxLength + 1); var bytes = new byte[length]; _random.NextBytes(bytes); return ByteString.CopyFrom(bytes); } } // Example usage: /* public class Program { public static void Main() { var faker = new ProtobufFaker(); // Generate fake data for any protobuf message var message = faker.Generate<YourProtobufMessage>(); // The faker will properly handle: // - All protobuf field types // - Repeated fields // - Map fields // - Oneof fields // - Nested messages // - Enums // - Optional fields Console.WriteLine(message.ToString()); } } */