add "balance" GraphQL query

Mimir/GraphQL/Queries/Query.cs

@@ -1,3 +1,6 @@
+using HotChocolate.AspNetCore;
+using Lib9c.GraphQL.Extensions;
+using Lib9c.GraphQL.InputObjects;
 using Lib9c.Models.States;
 using Libplanet.Crypto;
 using Mimir.GraphQL.Objects;
@@ -14,8 +17,35 @@ public class Query
  /// <param name="collectionName">The name of the collection.</param>
  /// <param name="repo"></param>
  /// <returns>The metadata</returns>
- public async Task<MetadataDocument> GetMetadataAsync(string collectionName, [Service] MetadataRepository repo)
- => await repo.GetByCollectionAsync(collectionName);
+ public async Task<MetadataDocument> GetMetadataAsync(string collectionName, [Service] MetadataRepository repo) =>
+ await repo.GetByCollectionAsync(collectionName);
+
+ /// <summary>
+ /// Get the balance of a specific currency for a given address.
+ /// Choose one of the following parameters to specify the currency: currency, currencyTicker
+ /// </summary>
+ /// <param name="currency">The currency object.</param>
+ /// <param name="currencyTicker">The ticker of the currency.</param>
+ /// <param name="address">The address of the balance.</param>
+ /// <exception cref="GraphQLRequestException"></exception>
+ public async Task<string> GetBalanceAsync(
+ CurrencyInput? currency,
+ string? currencyTicker,
+ Address address,
+ [Service] BalanceRepository repo)
+ {
+ if (currency is not null)
+ {
+ return (await repo.GetByAddressAsync(currency.ToCurrency(), address)).Object;
+ }
+
+ if (currencyTicker is not null)
+ {
+ return (await repo.GetByAddressAsync(currencyTicker.ToCurrency(), address)).Object;
+ }
+
+ throw new GraphQLRequestException("Either currency or currencyTicker must be provided.");
+ }
 
  /// <summary>
  /// Get an agent state by address.