MongoDB Storage Provider

dotnet add package Zetian
dotnet add package Zetian.Storage.MongoDB

using Zetian.Server;
using Zetian.Storage.MongoDB.Extensions;

// Basic setup with MongoDB
var server = new SmtpServerBuilder()
    .Port(25)
    .WithMongoDbStorage(
        "mongodb://localhost:27017",
        "smtp_database")
    .Build();

await server.StartAsync();

var server = new SmtpServerBuilder()
    .Port(25)
    .WithMongoDbStorage(
        "mongodb://localhost:27017",
        "smtp_database",
        config =>
        {
            config.CollectionName = "messages";
            config.GridFsBucketName = "attachments";
            
            // GridFS for large attachments
            config.UseGridFsForLargeMessages = true;
            config.GridFsThresholdMB = 50;
            
            // TTL for auto-cleanup
            config.EnableTTL = true;
            config.TTLDays = 30;
            
            // Sharding support
            config.ShardKeyField = "received_date";
            
            // Performance
            config.CompressMessageBody = true;
        })
    .Build();

// GridFS automatically handles large attachments
// Files over threshold are stored in chunks

// Retrieve attachment from GridFS
var gridFsBucket = new GridFSBucket(database, new GridFSBucketOptions
{
    BucketName = "attachments"
});

byte[] fileBytes;
using (var downloadStream = await gridFsBucket.OpenDownloadStreamByNameAsync("large-file.pdf"))
using (var memoryStream = new MemoryStream())
{
    await downloadStream.CopyToAsync(memoryStream);
    fileBytes = memoryStream.ToArray();
}

using var uploadStream = await gridFsBucket.OpenUploadStreamAsync("new-file.pdf");
await uploadStream.WriteAsync(fileBytes);
await uploadStream.CloseAsync();

// TTL index for automatic cleanup
db.messages.createIndex(
    { "created_at": 1 },
    { expireAfterSeconds: 2592000 } // 30 days
);

// Messages older than 30 days are automatically deleted
// No manual cleanup required!

// MongoDB query examples
var collection = database.GetCollection<BsonDocument>("messages");

// Find by sender
var filter = Builders<BsonDocument>.Filter.Eq("from_address", "[email protected]");
var messages = await collection.Find(filter).ToListAsync();

// Find recent messages
var recentFilter = Builders<BsonDocument>.Filter.Gte("received_date", DateTime.UtcNow.AddDays(-7));
var recentMessages = await collection.Find(recentFilter).SortByDescending(x => x["received_date"]).ToListAsync();

// Aggregate statistics
var pipeline = new[]
{
    new BsonDocument("$group", new BsonDocument
    {
        { "_id", "$from_address" },
        { "count", new BsonDocument("$sum", 1) },
        { "total_size", new BsonDocument("$sum", "$message_size") }
    })
};
var stats = await collection.Aggregate<BsonDocument>(pipeline).ToListAsync();