Add support for single offer endpoint

StellarDotnetSdk.Tests/Requests/OffersRequestBuilderTest.cs

@@ -108,6 +108,25 @@ public async Task TestOffersWithBuyingCreditAsset()
         OfferPageDeserializerTest.AssertTestData(offerResponsePage);
     }
 
+    [TestMethod]
+    public async Task TestSingleOffer()
+    {
+        using var server = await Utils.CreateTestServerWithJson("Responses/offer.json");
+        var offer = await server.Offers.Offer("GAHEAZQD6K7QBBPGLQZQOHCA5L3Z7ZNFBDU5XCCEI7QYVEFIRUF3IW27");
+        Assert.AreEqual("100.0000000", offer.Amount);
+        Assert.AreEqual("1", offer.PagingToken);
+        Assert.AreEqual(0, offer.Buying.CompareTo(new AssetTypeNative()));
+        Assert.AreEqual("GAHEAZQD6K7QBBPGLQZQOHCA5L3Z7ZNFBDU5XCCEI7QYVEFIRUF3IW27", offer.Seller);
+        Assert.AreEqual(0, offer.Selling.CompareTo(Asset.CreateNonNativeAsset("IOM", "GBL37ZFYU3FRBKTFO4YPIAELTO2PN6YEIF3ZS6FKOEAM5SOWALX5IP44")));
+        Assert.AreEqual("1", offer.Id);
+        Assert.AreEqual("https://horizon-testnet.stellar.org/offers/1", offer.Links.Self.Href);
+        Assert.AreEqual("https://horizon-testnet.stellar.org/accounts/GAHEAZQD6K7QBBPGLQZQOHCA5L3Z7ZNFBDU5XCCEI7QYVEFIRUF3IW27", offer.Links.OfferMaker.Href);
+        Assert.AreEqual(new Price(1, 2), offer.PriceRatio);
+        Assert.AreEqual("0.5000000", offer.Price);
+        Assert.AreEqual(380, offer.LastModifiedLedger);
+        Assert.AreEqual("2024-12-10T17:50:08Z", offer.LastModifiedTime);
+
+    }
     private async Task<Server> CreateServer()
     {
         return await Utils.CreateTestServerWithJson("Responses/offerPage.json");

StellarDotnetSdk.Tests/StellarDotnetSdk.Tests.csproj

@@ -464,6 +464,9 @@
         <None Update="TestData\Responses\transactionFeeBump.json">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </None>
+        <None Update="TestData\Responses\offer.json">
+          <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+        </None>
     </ItemGroup>
     <ItemGroup>
         <Compile Remove="KeyPairBIP39Tests.cs"/>

StellarDotnetSdk.Tests/TestData/Responses/offer.json

@@ -0,0 +1,29 @@
+{
+  "_links": {
+    "self": {
+      "href": "https://horizon-testnet.stellar.org/offers/1"
+    },
+    "offer_maker": {
+      "href": "https://horizon-testnet.stellar.org/accounts/GAHEAZQD6K7QBBPGLQZQOHCA5L3Z7ZNFBDU5XCCEI7QYVEFIRUF3IW27"
+    }
+  },
+  "id": "1",
+  "paging_token": "1",
+  "seller": "GAHEAZQD6K7QBBPGLQZQOHCA5L3Z7ZNFBDU5XCCEI7QYVEFIRUF3IW27",
+  "selling": {
+    "asset_type": "credit_alphanum4",
+    "asset_code": "IOM",
+    "asset_issuer": "GBL37ZFYU3FRBKTFO4YPIAELTO2PN6YEIF3ZS6FKOEAM5SOWALX5IP44"
+  },
+  "buying": {
+    "asset_type": "native"
+  },
+  "amount": "100.0000000",
+  "price_r": {
+    "n": 1,
+    "d": 2
+  },
+  "price": "0.5000000",
+  "last_modified_ledger": 380,
+  "last_modified_time": "2024-12-10T17:50:08Z"
+}

StellarDotnetSdk/Requests/OffersRequestBuilder.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Net.Http;
+using System.Threading.Tasks;
 using StellarDotnetSdk.Assets;
 using StellarDotnetSdk.Responses;
 
@@ -13,6 +14,17 @@ public OffersRequestBuilder(Uri serverUri, HttpClient httpClient) :
     {
     }
 
+    /// <summary>
+    ///     Requests specific uri and returns OfferResponse
+    /// </summary>
+    public async Task<OfferResponse> Offer(Uri uri)
+    {
+        var responseHandler = new ResponseHandler<OfferResponse>();
+
+        var response = await HttpClient.GetAsync(uri);
+        return await responseHandler.HandleResponse(response);
+    }
+
     /// <summary>
     ///     Builds request to GET /accounts/{account}/offers
     ///     See: https://www.stellar.org/developers/horizon/reference/offers-for-account.html
@@ -34,10 +46,7 @@ public OffersRequestBuilder ForAccount(string account)
     /// <exception cref="ArgumentNullException"></exception>
     public OffersRequestBuilder Offers(OffersRequestOptions options)
     {
-        if (options == null)
-        {
-            throw new ArgumentNullException(nameof(options));
-        }
+        ArgumentNullException.ThrowIfNull(options);
 
         if (options.Seller != null)
         {
@@ -102,6 +111,17 @@ public OffersRequestBuilder WithBuyingAsset(Asset buying)
         return Offers(options => options.Buying = buying);
     }
 
+    /// <summary>
+    ///     Requests <code>GET /offers/{offerId}</code>
+    ///     <a href="https://developers.stellar.org/docs/data/horizon/api-reference/get-offer-by-offer-id">Retrieve an Offer</a>
+    /// </summary>
+    /// <param name="offerId">ID of the offer to fetch.</param>
+    public async Task<OfferResponse> Offer(string offerId)
+    {
+        SetSegments("offers", offerId);
+        return await Offer(BuildUri());
+    }
+
     private void AddAssetFilterQueryParam(string side, Asset asset)
     {
         UriBuilder.SetQueryParam($"{side}_asset_type", asset.Type);