Line data    Source code

       1             : #region Copyright
       2             : // // -----------------------------------------------------------------------
       3             : // // <copyright company="Chinchilla Software Limited">
       4             : // //   Copyright Chinchilla Software Limited. All rights reserved.
       5             : // // </copyright>
       6             : // // -----------------------------------------------------------------------
       7             : #endregion
       8             : 
       9             : using System;
      10             : using System.Linq;
      11             : using Cqrs.Domain;
      12             : 
      13             : namespace Cqrs.Snapshots
      14             : {
      15             :         /// <summary>
      16             :         /// An <see cref="ISnapshotStrategy{TAuthenticationToken}"/> that takes a snapshot every 15 versions.
      17             :         /// </summary>
      18             :         /// <typeparam name="TAuthenticationToken">The <see cref="Type"/> of the authentication token.</typeparam>
      19             :         public class DefaultSnapshotStrategy<TAuthenticationToken> : ISnapshotStrategy<TAuthenticationToken>
      20           1 :         {
      21             :                 private const int SnapshotInterval = 15;
      22             : 
      23             :                 /// <summary>
      24             :                 /// Indicates if the <paramref name="aggregateType"/> is able to be snapshotted by checking if the <paramref name="aggregateType"/>
      25             :                 /// directly inherits <see cref="SnapshotAggregateRoot{TAuthenticationToken,TSnapshot}"/>
      26             :                 /// </summary>
      27             :                 /// <param name="aggregateType">The <see cref="Type"/> of <see cref="IAggregateRoot{TAuthenticationToken}"/> to check.</param>
      28           1 :                 public virtual bool IsSnapshotable(Type aggregateType)
      29             :                 {
      30             :                         if (aggregateType.BaseType == null)
      31             :                                 return false;
      32             :                         if (aggregateType.BaseType.IsGenericType && aggregateType.BaseType.GetGenericTypeDefinition() == typeof(SnapshotAggregateRoot<,>))
      33             :                                 return true;
      34             :                         return IsSnapshotable(aggregateType.BaseType);
      35             :                 }
      36             : 
      37             :                 /// <summary>
      38             :                 /// Checks <see cref="IsSnapshotable"/> and if it is, also checks if the calculated version number would be exactly dividable by <see cref="GetSnapshotInterval"/>.
      39             :                 /// </summary>
      40             :                 /// <param name="aggregate">The <see cref="IAggregateRoot{TAuthenticationToken}"/> to check.</param>
      41           1 :                 public virtual bool ShouldMakeSnapShot(IAggregateRoot<TAuthenticationToken> aggregate)
      42             :                 {
      43             :                         if (!IsSnapshotable(aggregate.GetType()))
      44             :                                 return false;
      45             : 
      46             :                         // Why isn't this something as simple as `(aggregate.Version + aggregate.GetUncommittedChanges().Count()) % SnapshotInterval`???
      47             :                         int i = aggregate.Version;
      48             : 
      49             :                         int limit = aggregate.GetUncommittedChanges().Count();
      50             :                         for (int j = 0; j < limit; j++)
      51             :                                 if (++i % GetSnapshotInterval() == 0 && i != 0)
      52             :                                         return true;
      53             :                         return false;
      54             :                 }
      55             : 
      56             :                 /// <summary>
      57             :                 /// Returns the value of <see cref="SnapshotInterval"/>.
      58             :                 /// </summary>
      59           1 :                 protected virtual int GetSnapshotInterval()
      60             :                 {
      61             :                         return SnapshotInterval;
      62             :                 }
      63             :         }
      64             : }