Converter.cs

using Microsoft.Azure.Storage.Queue;

using FluentStorage.Messaging;
using System;
using System.IO;
using System.Linq;
using System.Text;
using FluentStorage.Utils.Extensions;

namespace FluentStorage.Azure.Queues {
	internal static class Converter {
		private const string PropEndWord = "PROPEND";
		private static readonly Guid CustomFlag = new Guid("820e7dc0-46a3-4177-a241-cdac97275ca9");
		private static readonly byte[] CustomFlagBytes = CustomFlag.ToByteArray();

		public static CloudQueueMessage ToCloudQueueMessage(QueueMessage message) {
			if (message == null)
				throw new ArgumentNullException(nameof(message));

			//when there are no properties pack the data as binary in raw form
			if (message.Properties == null || message.Properties.Count == 0) {
				var r = new CloudQueueMessage((string)null);
				r.SetMessageContent2(message.Content);
				return r;
			}

			//note that Azure Storage doesn't have properties on message, therefore I can do a simulation instead

			var clazz = new JsonProps {
				Properties = message.Properties.Select(p => new JsonProp { Name = p.Key, Value = p.Value }).ToArray()
			};
			byte[] propBytes = Encoding.UTF8.GetBytes(clazz.ToJsonString());

			CloudQueueMessage result;
			using (var ms = new MemoryStream()) {
				using (var writer = new BinaryWriter(ms, Encoding.UTF8)) {
					writer.Write(CustomFlagBytes);
					writer.Write(propBytes.Length);
					writer.Write(propBytes);
					if (message.Content != null) {
						writer.Write(message.Content);
					}
				}

				result = new CloudQueueMessage((string)null);
				result.SetMessageContent2(ms.ToArray());
			}

			return result;
		}

		public static QueueMessage ToQueueMessage(CloudQueueMessage message) {
			if (message == null) return null;

			byte[] mb = message.AsBytes;
			QueueMessage result;
			if (!IsCustomMessage(mb)) {
				result = new QueueMessage(CreateId(message), mb);
			}
			else {
				using (var ms = new MemoryStream(mb)) {
					//skip forward custom message flag
					ms.Seek(CustomFlagBytes.Length, SeekOrigin.Begin);

					//read the custom properties length
					int cpl;
					using (var br = new BinaryReader(ms, Encoding.UTF8, true)) {
						cpl = br.ReadInt32();
					}

					//read the actual properties
					byte[] propBytes = new byte[cpl];
					ms.Read(propBytes, 0, cpl);
					string propString = Encoding.UTF8.GetString(propBytes);
					JsonProps props = propString.AsJsonObject<JsonProps>();

					//read message data
					byte[] leftovers = ms.ToByteArray();

					result = new QueueMessage(CreateId(message), leftovers);
					foreach (JsonProp prop in props.Properties) {
						result.Properties[prop.Name] = prop.Value;
					}
				}
			}

			result.DequeueCount = message.DequeueCount;
			return result;
		}

		private static bool IsCustomMessage(byte[] messageBytes) {
			if (messageBytes.Length < CustomFlagBytes.Length) return false;

			byte[] firstBytes = new byte[CustomFlagBytes.Length];
			Array.Copy(messageBytes, 0, firstBytes, 0, CustomFlagBytes.Length);

			return firstBytes.SequenceEqual(CustomFlagBytes);
		}

		internal static string CreateId(CloudQueueMessage message) {
			if (string.IsNullOrEmpty(message.PopReceipt)) return message.Id;

			return message.Id + ":" + message.PopReceipt;
		}

		internal static void SplitId(string compositeId, out string id, out string popReceipt) {
			string[] parts = compositeId.Split(new[] { ':' }, 2, StringSplitOptions.RemoveEmptyEntries);
			id = parts[0];
			popReceipt = parts.Length > 1 ? parts[1] : null;
		}

	}
}