Improve FetchRequest & FetchResponse public API and make it more futu…

…re-proof + fix bug in UnityWebRequestConfigFetcher

samples/UnityWebGL/Assets/Scripts/SingletonServices.cs

@@ -153,7 +153,11 @@ public async Task<FetchResponse> FetchAsync(FetchRequest request, CancellationTo
 
             using var webRequest = UnityWebRequest.Get(uri);
 
-            webRequest.SetRequestHeader(request.SdkInfoHeader.Key, request.SdkInfoHeader.Value);
+            for (int i = 0, n = request.Headers.Count; i < n; i++)
+            {
+                var header = request.Headers[i];
+                webRequest.SetRequestHeader(header.Key, header.Value);
+            }
 
             webRequest.timeout = (int)request.Timeout.TotalSeconds;
 
@@ -177,20 +181,11 @@ public async Task<FetchResponse> FetchAsync(FetchRequest request, CancellationTo
 
             await tcs.Task;
 
-            if (webRequest.result == UnityWebRequest.Result.Success)
+            if (webRequest.result is UnityWebRequest.Result.Success or UnityWebRequest.Result.ProtocolError)
             {
                 var statusCode = (HttpStatusCode)webRequest.responseCode;
                 Debug.Log($"Fetching config finished with status code {statusCode}.");
-                if (statusCode == HttpStatusCode.OK)
-                {
-                    var eTag = webRequest.GetResponseHeader("etag");
-                    var text = webRequest.downloadHandler.text;
-                    return new FetchResponse(statusCode, reasonPhrase: null, eTag is { Length: > 0 } ? eTag : null, webRequest.downloadHandler.text);
-                }
-                else
-                {
-                    return new FetchResponse(statusCode, reasonPhrase: null, null, null);
-                }
+                return new FetchResponse(statusCode, reasonPhrase: null, webRequest.GetResponseHeaders(), statusCode == HttpStatusCode.OK ? webRequest.downloadHandler.text : null);
             }
             else if (webRequest.result == UnityWebRequest.Result.ConnectionError && webRequest.error == "Request timeout")
             {

src/ConfigCatClient/ConfigService/DefaultConfigFetcher.cs

@@ -11,7 +11,7 @@ namespace ConfigCat.Client;
 internal sealed class DefaultConfigFetcher : IConfigFetcher, IDisposable
 {
     private readonly object syncObj = new();
-    private readonly KeyValuePair<string, string> sdkInfoHeader;
+    private readonly IReadOnlyList<KeyValuePair<string, string>> requestHeaders;
     private readonly LoggerWrapper logger;
     private readonly IConfigCatConfigFetcher configFetcher;
     private readonly bool isCustomUri;
@@ -25,9 +25,10 @@ public DefaultConfigFetcher(Uri requestUri, string productVersion, LoggerWrapper
         IConfigCatConfigFetcher configFetcher, bool isCustomUri, TimeSpan timeout)
     {
         this.requestUri = requestUri;
-        this.sdkInfoHeader = new KeyValuePair<string, string>(
-            "X-ConfigCat-UserAgent",
-            new ProductInfoHeaderValue("ConfigCat-Dotnet", productVersion).ToString());
+        this.requestHeaders = new[]
+        {
+            new KeyValuePair<string, string>("X-ConfigCat-UserAgent", new ProductInfoHeaderValue("ConfigCat-Dotnet", productVersion).ToString())
+        };
         this.logger = logger;
         this.configFetcher = configFetcher;
         this.isCustomUri = isCustomUri;
@@ -153,7 +154,7 @@ private async ValueTask<DeserializedResponse> FetchRequestAsync(string? httpETag
     {
         for (; ; maxExecutionCount--)
         {
-            var request = new FetchRequest(this.requestUri, httpETag, this.sdkInfoHeader, this.timeout);
+            var request = new FetchRequest(this.requestUri, httpETag, this.requestHeaders, this.timeout);
 
             var response = await this.configFetcher.FetchAsync(request, this.cancellationTokenSource.Token).ConfigureAwait(TaskShim.ContinueOnCapturedContext);
 

src/ConfigCatClient/ConfigService/FetchRequest.cs

@@ -12,11 +12,11 @@ public readonly struct FetchRequest
     /// <summary>
     /// Initializes a new instance of the <see cref="FetchRequest"/> struct.
     /// </summary>
-    public FetchRequest(Uri uri, string? lastETag, KeyValuePair<string, string> sdkInfoHeader, TimeSpan timeout)
+    public FetchRequest(Uri uri, string? lastETag, IReadOnlyList<KeyValuePair<string, string>> headers, TimeSpan timeout)
     {
         Uri = uri ?? throw new ArgumentNullException(nameof(uri));
         LastETag = lastETag;
-        SdkInfoHeader = sdkInfoHeader;
+        Headers = headers;
         Timeout = timeout;
     }
 
@@ -27,13 +27,17 @@ public FetchRequest(Uri uri, string? lastETag, KeyValuePair<string, string> sdkI
 
     /// <summary>
     /// The value of the <c>ETag</c> HTTP response header received during the last successful request (if any).
+    /// If available, should be included in the HTTP request, either in the <c>If-None-Match</c> header or in the <c>ccetag</c> query string parameter.
     /// </summary>
+    /// <remarks>
+    /// In browser runtime environments the <c>If-None-Match</c> header should be avoided because that may cause unnecessary CORS preflight requests.
+    /// </remarks>
     public string? LastETag { get; }
 
     /// <summary>
-    /// The name and value of the HTTP request header containing information about the SDK. Should be included in every request.
+    /// Additional HTTP request headers. Should be included in every HTTP request.
     /// </summary>
-    public KeyValuePair<string, string> SdkInfoHeader { get; }
+    public IReadOnlyList<KeyValuePair<string, string>> Headers { get; }
 
     /// <summary>
     /// The request timeout to apply, configured via <see cref="ConfigCatClientOptions.HttpTimeout"/>.

src/ConfigCatClient/ConfigService/FetchResponse.cs

@@ -1,7 +1,8 @@
+using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Net;
 using System.Net.Http;
-using System.Net.Http.Headers;
 
 namespace ConfigCat.Client;
 
@@ -10,26 +11,51 @@ namespace ConfigCat.Client;
 /// </summary>
 public readonly struct FetchResponse
 {
-    internal static FetchResponse From(HttpResponseMessage httpResponse, string? httpResponseBody = null)
-    {
-        return new FetchResponse(httpResponse.StatusCode, httpResponse.ReasonPhrase, httpResponse.Headers, httpResponseBody);
-    }
-
-    private readonly object? headersOrETag; // either null or a string or HttpResponseHeaders
-
-    private FetchResponse(HttpStatusCode statusCode, string? reasonPhrase, object? headersOrETag, string? body)
+    private FetchResponse(HttpStatusCode statusCode, string? reasonPhrase, string? body)
     {
         StatusCode = statusCode;
         ReasonPhrase = reasonPhrase;
-        this.headersOrETag = headersOrETag;
         Body = body;
     }
 
+    internal FetchResponse(HttpResponseMessage httpResponse, string? httpResponseBody = null)
+        : this(httpResponse.StatusCode, httpResponse.ReasonPhrase, httpResponseBody)
+    {
+        ETag = httpResponse.Headers.ETag?.Tag;
+        RayId = httpResponse.Headers.TryGetValues("CF-RAY", out var values) ? values.FirstOrDefault() : null;
+    }
+
     /// <summary>
     /// Initializes a new instance of the <see cref="FetchResponse"/> struct.
     /// </summary>
-    public FetchResponse(HttpStatusCode statusCode, string? reasonPhrase, string? eTag, string? body)
-        : this(statusCode, reasonPhrase, (object?)eTag, body) { }
+    public FetchResponse(HttpStatusCode statusCode, string? reasonPhrase, IEnumerable<KeyValuePair<string, string>> headers, string? body = null)
+        : this(statusCode, reasonPhrase, body)
+    {
+        string? eTag = null, rayId = null;
+
+        foreach (var header in headers)
+        {
+            if (eTag is null && "ETag".Equals(header.Key, StringComparison.OrdinalIgnoreCase))
+            {
+                eTag = header.Value;
+                if (rayId is not null)
+                {
+                    break;
+                }
+            }
+            else if (rayId is null && "CF-RAY".Equals(header.Key, StringComparison.OrdinalIgnoreCase))
+            {
+                rayId = header.Value;
+                if (eTag is not null)
+                {
+                    break;
+                }
+            }
+        }
+
+        ETag = eTag;
+        RayId = rayId;
+    }
 
     /// <summary>
     /// The HTTP status code.
@@ -44,9 +70,9 @@ public FetchResponse(HttpStatusCode statusCode, string? reasonPhrase, string? eT
     /// <summary>
     /// The value of the <c>ETag</c> HTTP response header.
     /// </summary>
-    public string? ETag => this.headersOrETag is HttpResponseHeaders headers ? headers.ETag?.Tag : (string?)this.headersOrETag;
+    public string? ETag { get; }
 
-    internal string? RayId => this.headersOrETag is HttpResponseHeaders headers && headers.TryGetValues("CF-RAY", out var values) ? values.FirstOrDefault() : null;
+    internal string? RayId { get; }
 
     /// <summary>
     /// The response body.

src/ConfigCatClient/ConfigService/HttpClientConfigFetcher.cs

@@ -71,7 +71,11 @@ public async Task<FetchResponse> FetchAsync(FetchRequest request, CancellationTo
             RequestUri = request.Uri,
         };
 
-        httpRequest.Headers.Add(request.SdkInfoHeader.Key, request.SdkInfoHeader.Value);
+        for (int i = 0, n = request.Headers.Count; i < n; i++)
+        {
+            var header = request.Headers[i];
+            httpRequest.Headers.Add(header.Key, header.Value);
+        }
 
         if (request.LastETag is not null)
         {
@@ -90,11 +94,11 @@ public async Task<FetchResponse> FetchAsync(FetchRequest request, CancellationTo
                 var httpResponseBody = await httpResponse.Content.ReadAsStringAsync().ConfigureAwait(TaskShim.ContinueOnCapturedContext);
 #endif
 
-                return FetchResponse.From(httpResponse, httpResponseBody);
+                return new FetchResponse(httpResponse, httpResponseBody);
             }
             else
             {
-                var response = FetchResponse.From(httpResponse);
+                var response = new FetchResponse(httpResponse);
                 if (!response.IsExpected)
                 {
                     this.httpClient = null;