/// <summary>
/// Loads the most recent snapshot using the specified connection and aggregate identifier.
/// </summary>
/// <typeparam name="TKey">The type of aggregate identifier.</typeparam>
/// <param name="connection">The <see cref="DbConnection">connection</see> used to load the snapshot.</param>
/// <param name="aggregateId">The identifier of the aggregate to load the snapshot for.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken">token</see> that can be used to cancel the operation.</param>
/// <returns>The <see cref="Task{TResult}">task</see> containing the loaded <see cref="SqlSnapshotDescriptor{TKey}">snapshot</see>
/// or <c>null</c> if no match is found.</returns>
public virtual async Task <SqlSnapshotDescriptor <TKey> > LoadSnapshot <TKey>(DbConnection connection, TKey aggregateId, CancellationToken cancellationToken)
{
Arg.NotNull(connection, nameof(connection));
var snapshot = default(SqlSnapshotDescriptor <TKey>);
using (var command = connection.CreateCommand())
{
var parameter = command.CreateParameter();
parameter.ParameterName = "AggregateId";
parameter.Value = aggregateId;
command.Parameters.Add(parameter);
command.CommandText = Sql.Snapshots.Load;
using (var reader = await command.ExecuteReaderAsync(SingleRow, cancellationToken).ConfigureAwait(false))
{
if (await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
{
snapshot = new SqlSnapshotDescriptor <TKey>()
{
AggregateId = aggregateId,
SnapshotType = reader.GetString(0),
Version = reader.GetInt32(1),
Snapshot = reader.GetStream(2),
};
}
}
}
return(snapshot);
}
/// <summary>
/// Saves the specified snapshot descriptor using the provided command.
/// </summary>
/// <typeparam name="TKey">The type of key.</typeparam>
/// <param name="command">The <see cref="DbCommand">database command</see> used to save the snapshot.</param>
/// <param name="snapshotDescriptor">The <see cref="EventDescriptor{TKey}">snapshot descriptor</see> that
/// describes the snapshot being saved.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken">token</see> that can be used to cancel the operation.</param>
/// <returns>A <see cref="Task">task</see> representing the asynchronous operation.</returns>
public virtual Task SaveSnapshot <TKey>(DbCommand command, SqlSnapshotDescriptor <TKey> snapshotDescriptor, CancellationToken cancellationToken)
{
Arg.NotNull(command, nameof(command));
Arg.NotNull(snapshotDescriptor, nameof(snapshotDescriptor));
command.Parameters["AggregateId"].Value = snapshotDescriptor.AggregateId;
command.Parameters["Version"].Value = snapshotDescriptor.Version;
command.Parameters["Type"].Value = snapshotDescriptor.SnapshotType;
command.Parameters["Snapshot"].Value = snapshotDescriptor.Snapshot;
return(command.ExecuteNonQueryAsync(cancellationToken));
}
/// <summary>
/// Saves the specified snapshot descriptor.
/// </summary>
/// <typeparam name="TKey">The type of key.</typeparam>
/// <param name="snapshotDescriptor">The <see cref="EventDescriptor{TKey}">snapshot descriptor</see> that
/// describes the snapshot being saved.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken">token</see> that can be used to cancel the operation.</param>
/// <returns>A <see cref="Task">task</see> representing the asynchronous operation.</returns>
public virtual async Task SaveSnapshot <TKey>(SqlSnapshotDescriptor <TKey> snapshotDescriptor, CancellationToken cancellationToken)
{
Arg.NotNull(snapshotDescriptor, nameof(snapshotDescriptor));
using (var connection = CreateConnection())
{
await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
using (var command = NewSaveEventCommand())
{
command.Connection = connection;
await SaveSnapshot(command, snapshotDescriptor, cancellationToken).ConfigureAwait(false);
}
}
}
/// <summary>
/// Returns a new event stream that contains a snapshot using the specified descriptor.
/// </summary>
/// <param name="events">The <see cref="IEnumerable{T}">sequence</see> representing the <see cref="IEvent">event</see> stream.</param>
/// <param name="snapshotDescriptor">The <see cref="SqlSnapshotDescriptor{TKey}">descriptor</see> describing the
/// <see cref="ISnapshot{TKey}">snapshot</see> contained in the stream.</param>
/// <returns>A new <see cref="IEnumerable{T}">sequence</see> of <see cref="IEvent">events</see> containing a
/// <see cref="ISnapshot{TKey}">snapshot</see>.</returns>
protected virtual IEnumerable <IEvent> NewEventStreamWithSnapshot(IEnumerable <IEvent> events, SqlSnapshotDescriptor <TKey> snapshotDescriptor)
{
Arg.NotNull(events, nameof(events));
Arg.NotNull(snapshotDescriptor, nameof(snapshotDescriptor));
Contract.Ensures(Contract.Result <IEnumerable <IEvent> >() != null);
return(snapshotSerializer.Deserialize(events, snapshotDescriptor));
}
internal IEnumerable <IEvent> Deserialize <TKey>(IEnumerable <IEvent> events, SqlSnapshotDescriptor <TKey> snapshotDescriptor)
{
var abstractFactory = factories.GetOrAdd(snapshotDescriptor.SnapshotType, NewFactory);
var deserialize = abstractFactory.NewDeserializer(snapshotDescriptor.SnapshotType);
return(deserialize(events, snapshotDescriptor.Snapshot));
}