feat: Cache tokens between calls (#19)

source/VMelnalksnis.NordigenDotNet.DependencyInjection/ServiceCollectionExtensions.cs

@@ -30,13 +30,16 @@ public static class ServiceCollectionExtensions
 	/// <summary>Adds all required services for <see cref="INordigenClient"/>.</summary>
 	/// <param name="serviceCollection">The service collection in which to register the services.</param>
 	/// <param name="configuration">The configuration to which to bind options models.</param>
+	/// <param name="clock">Clock for accessing the current time.</param>
 	/// <param name="dateTimeZoneProvider">Time zone provider for date and time serialization.</param>
 	/// <returns>The <see cref="IHttpClientBuilder"/> for the <see cref="HttpClient"/> used by <see cref="INordigenClient"/>.</returns>
 	public static IHttpClientBuilder AddNordigenDotNet(
 		this IServiceCollection serviceCollection,
 		IConfiguration configuration,
+		IClock clock,
 		IDateTimeZoneProvider dateTimeZoneProvider)
 	{
+		serviceCollection.TryAddSingleton(clock);
 		serviceCollection.TryAddSingleton(dateTimeZoneProvider);
 		return serviceCollection.AddNordigenDotNet(configuration);
 	}
@@ -58,6 +61,7 @@ public static class ServiceCollectionExtensions
 		serviceCollection.AddHttpClient<TokenDelegatingHandler>(ConfigureNordigenClient);
 
 		return serviceCollection
+			.AddSingleton<NordigenTokenCache>()
 			.AddTransient<INordigenClient, NordigenClient>()
 			.AddTransient<IAccountClient, AccountClient>()
 			.AddTransient<IAgreementClient, AgreementClient>()

source/VMelnalksnis.NordigenDotNet/NordigenOptions.cs

@@ -24,4 +24,7 @@ public sealed record NordigenOptions
 	/// <summary>Gets the secret key used to create new access tokens.</summary>
 	[Required]
 	public string SecretKey { get; init; } = null!;
+
+	/// <summary>Gets the factor by which to divide the expiration time for access and refresh tokens.</summary>
+	public double ExpirationFactor { get; init; } = 2d;
 }

source/VMelnalksnis.NordigenDotNet/Tokens/NordigenTokenCache.cs

@@ -0,0 +1,59 @@
+// Copyright 2022 Valters Melnalksnis
+// Licensed under the Apache License 2.0.
+// See LICENSE file in the project root for full license information.
+
+using NodaTime;
+
+namespace VMelnalksnis.NordigenDotNet.Tokens;
+
+/// <summary>Caches refresh and access tokens for <see cref="NordigenHttpClient"/>.</summary>
+public sealed class NordigenTokenCache
+{
+	private readonly NordigenOptions _nordigenOptions;
+	private readonly IClock _clock;
+
+	/// <summary>Initializes a new instance of the <see cref="NordigenTokenCache"/> class.</summary>
+	/// <param name="nordigenOptions">Options for connection to the Nordigen API.</param>
+	/// <param name="clock">Clock for accessing the current time.</param>
+	public NordigenTokenCache(NordigenOptions nordigenOptions, IClock clock)
+	{
+		_nordigenOptions = nordigenOptions;
+		_clock = clock;
+	}
+
+	internal AccessToken? AccessToken { get; private set; }
+
+	internal bool IsAccessExpired =>
+		AccessToken is not null &&
+		AccessExpiresAt is not null &&
+		_clock.GetCurrentInstant() > AccessExpiresAt;
+
+	internal Token? Token { get; private set; }
+
+	internal bool IsRefreshExpired =>
+		Token is not null &&
+		RefreshExpiresAt is not null &&
+		_clock.GetCurrentInstant() > RefreshExpiresAt;
+
+	private Instant? AccessExpiresAt { get; set; }
+
+	private Instant? RefreshExpiresAt { get; set; }
+
+	internal void SetToken(Token token)
+	{
+		Token = token;
+		AccessToken = token;
+		var currentInstant = _clock.GetCurrentInstant();
+		var factor = _nordigenOptions.ExpirationFactor;
+		AccessExpiresAt = currentInstant + Duration.FromSeconds(token.AccessExpires / factor);
+		RefreshExpiresAt = currentInstant + Duration.FromSeconds(token.RefreshExpires / factor);
+	}
+
+	internal void SetAccessToken(AccessToken accessToken)
+	{
+		AccessToken = accessToken;
+		var currentInstant = _clock.GetCurrentInstant();
+		var factor = _nordigenOptions.ExpirationFactor;
+		AccessExpiresAt = currentInstant + Duration.FromSeconds(accessToken.AccessExpires / factor);
+	}
+}

source/VMelnalksnis.NordigenDotNet/Tokens/TokenDelegatingHandler.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License 2.0.
 // See LICENSE file in the project root for full license information.
 
+using System.Net;
 using System.Net.Http;
 using System.Net.Http.Json;
 using System.Text.Json;
@@ -22,14 +23,17 @@ public sealed class TokenDelegatingHandler : DelegatingHandler
 
 	private readonly HttpClient _httpClient;
 	private readonly NordigenOptions _nordigenOptions;
+	private readonly NordigenTokenCache _tokenCache;
 
 	/// <summary>Initializes a new instance of the <see cref="TokenDelegatingHandler"/> class.</summary>
 	/// <param name="httpClient">Http client configured for making requests to the Nordigen API.</param>
 	/// <param name="nordigenOptions">Options for connection to the Nordigen API.</param>
-	public TokenDelegatingHandler(HttpClient httpClient, NordigenOptions nordigenOptions)
+	/// <param name="tokenCache">Nordigen API token cache for preserving tokens between requests.</param>
+	public TokenDelegatingHandler(HttpClient httpClient, NordigenOptions nordigenOptions, NordigenTokenCache tokenCache)
 	{
 		_httpClient = httpClient;
 		_nordigenOptions = nordigenOptions;
+		_tokenCache = tokenCache;
 	}
 
 	/// <inheritdoc />
@@ -37,13 +41,27 @@ public sealed class TokenDelegatingHandler : DelegatingHandler
 		HttpRequestMessage request,
 		CancellationToken cancellationToken)
 	{
-		var token = await CreateNewToken().ConfigureAwait(false);
-		request.Headers.Authorization = new("Bearer", token.Access);
+		if (_tokenCache.AccessToken is null || _tokenCache.IsRefreshExpired)
+		{
+			await CreateNewToken().ConfigureAwait(false);
+		}
+		else if (_tokenCache.IsAccessExpired)
+		{
+			await RefreshToken().ConfigureAwait(false);
+		}
 
+		request.Headers.Authorization = new("Bearer", _tokenCache.AccessToken?.Access);
+		var response = await base.SendAsync(request, cancellationToken).ConfigureAwait(false);
+		if (response.StatusCode is not HttpStatusCode.Unauthorized)
+		{
+			return response;
+		}
+
+		await CreateNewToken().ConfigureAwait(false);
 		return await base.SendAsync(request, cancellationToken).ConfigureAwait(false);
 	}
 
-	private async Task<Token> CreateNewToken()
+	private async Task CreateNewToken()
 	{
 		var tokenCreation = new TokenCreation(_nordigenOptions.SecretId, _nordigenOptions.SecretKey);
 		var tokenResponse = await _httpClient
@@ -52,18 +70,18 @@ public sealed class TokenDelegatingHandler : DelegatingHandler
 
 		await tokenResponse.ThrowIfNotSuccessful().ConfigureAwait(false);
 		var token = await tokenResponse.Content.ReadFromJsonAsync(_tokenInfo).ConfigureAwait(false);
-		return token!;
+		_tokenCache.SetToken(token!);
 	}
 
-	private async Task<AccessToken> Refresh(TokenRefresh tokenRefresh)
+	private async Task RefreshToken()
 	{
 		var tokenResponse = await _httpClient
-			.PostAsJsonAsync(Routes.Tokens.Refresh, tokenRefresh, _tokenRefreshInfo)
+			.PostAsJsonAsync(Routes.Tokens.Refresh, new(_tokenCache.Token!.Refresh), _tokenRefreshInfo)
 			.ConfigureAwait(false);
 
 		await tokenResponse.ThrowIfNotSuccessful().ConfigureAwait(false);
 		var accessToken = await tokenResponse.Content.ReadFromJsonAsync(_accessTokenInfo).ConfigureAwait(false);
 
-		return accessToken!;
+		_tokenCache.SetAccessToken(accessToken!);
 	}
 }