How to convert DocumentClient to IDocumentClient in gremlin?

Question

I am using cosmos db to store and fetch data. Previously I was using DocumentClient like:

 public class ProductRepository : IProductRepository
    {
        private DocumentClient _documentClient;
        private DocumentCollection _graphCollection;        

        public ProductRepository(DocumentClient documentClient, DocumentCollection graphCollection)
        {
            _documentClient = documentClient;
            _graphCollection = graphCollection;

        }

        public async Task Create(Product product)
        {
            var createQuery = CreateQuery(product);
            IDocumentQuery<dynamic> query = _documentClient.CreateGremlinQuery<dynamic>(_graphCollection, createQuery);
            if(query.HasMoreResults)
            {
                await query.ExecuteNextAsync();
            }
        }

     public async Task<Product> Get(string id)
     {
        Product product = null;
        var getQuery = @"g.V('" + id + "')";
        var query = _documentClient.CreateGremlinQuery<dynamic>(_graphCollection, getQuery);
        if (query.HasMoreResults)
        {
            var result = await query.ExecuteNextAsync();
            if (result.Count == 0)
                return product;
            var productData = (JObject)result.FirstOrDefault();
            product = new Product
            {
               name = productData["name"].ToString()
            };
        }
        return product;
     }
    }
}

But it is not unit testable so I want to convert it to IDocumentClient but IDocumentClient doesn't contain definition for CreateGremlinQuery. So what is the best possible way to convert my methods so that they will be using IDocumentClient? Do I need to use CreateDocumentQuery? if yes, how can I convert CreateGremlimQuery to CreateDocumentQuery?

Answer 1

There are several ways to get around that. The simplest one would be to simply hard cast your IDocumentClient to DocumentClient.

If you go with that approach your code becomes:

public class ProductRepository : IProductRepository
{
    private IDocumentClient _documentClient;
    private DocumentCollection _graphCollection;        

    public ProductRepository(IDocumentClient documentClient, DocumentCollection graphCollection)
    {
        _documentClient = documentClient;
        _graphCollection = graphCollection;

    }

    public async Task Create(Product product)
    {
        var createQuery = CreateQuery(product);
        IDocumentQuery<dynamic> query = ((DocumentClient)_documentClient).CreateGremlinQuery<dynamic>(_graphCollection, createQuery);
        if(query.HasMoreResults)
        {
            await query.ExecuteNextAsync();
        }
    }

     public async Task<Product> Get(string id)
     {
        Product product = null;
        var getQuery = @"g.V('" + id + "')";
        var query = ((DocumentClient)_documentClient).CreateGremlinQuery<dynamic>(_graphCollection, getQuery);
        if (query.HasMoreResults)
        {
            var result = await query.ExecuteNextAsync();
            if (result.Count == 0)
                return product;
            var productData = (JObject)result.FirstOrDefault();
            product = new Product
            {
               name = productData["name"].ToString()
            };
        }
        return product;
    }
}

You could also create your own extensions for IDocumentClient.

public static class MoreGraphExtensions
    {
        public static IDocumentQuery<T> CreateGremlinQuery<T>(this IDocumentClient documentClient, DocumentCollection collection, string gremlinExpression, FeedOptions feedOptions = null, GraphSONMode graphSONMode = GraphSONMode.Compact)
        {
            return GraphExtensions.CreateGremlinQuery<T>((DocumentClient)documentClient, collection, gremlinExpression, feedOptions, graphSONMode);
        }

        public static IDocumentQuery<object> CreateGremlinQuery(this IDocumentClient documentClient, DocumentCollection collection, string gremlinExpression, FeedOptions feedOptions = null, GraphSONMode graphSONMode = GraphSONMode.Compact)
        {
            return GraphExtensions.CreateGremlinQuery<object>((DocumentClient)documentClient, collection, gremlinExpression, feedOptions, graphSONMode);
        }
    }

It is a pre-release however, so I do think that Microsoft will get around moving the extension methods at the interface level.