Restructured the project structure back to the way it was, there's no reasonable way to split the modules

src/NadekoBot/Modules/Patronage/Patreon/PatreonClient.cs

@@ -0,0 +1,149 @@
+#nullable disable
+using OneOf;
+using OneOf.Types;
+using System.Net.Http.Json;
+using System.Text.Json;
+
+namespace NadekoBot.Modules.Patronage;
+
+public class PatreonClient : IDisposable
+{
+    private readonly string _clientId;
+    private readonly string _clientSecret;
+    private string refreshToken;
+    
+    
+    private string accessToken = string.Empty;
+    private readonly HttpClient _http;
+    
+    private DateTime refreshAt = DateTime.UtcNow;
+
+    public PatreonClient(string clientId, string clientSecret, string refreshToken)
+    {
+        _clientId = clientId;
+        _clientSecret = clientSecret;
+        this.refreshToken = refreshToken;
+
+        _http = new();
+    }
+
+    public void Dispose()
+        => _http.Dispose();
+
+    public PatreonCredentials GetCredentials()
+        => new PatreonCredentials()
+        {
+            AccessToken = accessToken,
+            ClientId = _clientId,
+            ClientSecret = _clientSecret,
+            RefreshToken = refreshToken,
+        };
+
+    public async Task<OneOf<Success, Error<string>>> RefreshTokenAsync(bool force)
+    {
+        if (!force && IsTokenValid())
+            return new Success();
+
+        var res = await _http.PostAsync("https://www.patreon.com/api/oauth2/token"
+                                        + "?grant_type=refresh_token"
+                                        + $"&refresh_token={refreshToken}"
+                                        + $"&client_id={_clientId}"
+                                        + $"&client_secret={_clientSecret}",
+            null);
+
+        if (!res.IsSuccessStatusCode)
+            return new Error<string>($"Request did not return a sucess status code. Status code: {res.StatusCode}");
+
+        try
+        {
+            var data = await res.Content.ReadFromJsonAsync<PatreonRefreshData>();
+
+            if (data is null)
+                return new Error<string>($"Invalid data retrieved from Patreon.");
+
+            refreshToken = data.RefreshToken;
+            accessToken = data.AccessToken;
+
+            refreshAt = DateTime.UtcNow.AddSeconds(data.ExpiresIn - 5.Minutes().TotalSeconds);
+            return new Success();
+        }
+        catch (Exception ex)
+        {
+            return new Error<string>($"Error during deserialization: {ex.Message}");
+        }
+    }
+
+    private async ValueTask<bool> EnsureTokenValidAsync()
+    {
+        if (!IsTokenValid())
+        {
+            var res = await RefreshTokenAsync(true);
+            return res.Match(
+                static _ => true,
+                static err =>
+                {
+                    Log.Warning("Error getting token: {ErrorMessage}", err.Value);
+                    return false;
+                });
+        }
+
+        return true;
+    }
+
+    private bool IsTokenValid()
+        => refreshAt > DateTime.UtcNow && !string.IsNullOrWhiteSpace(accessToken);
+
+    public async Task<OneOf<IAsyncEnumerable<IReadOnlyCollection<PatreonMemberData>>, Error<string>>> GetMembersAsync(string campaignId)
+    {
+        if (!await EnsureTokenValidAsync())
+            return new Error<string>("Unable to get patreon token");
+
+        return OneOf<IAsyncEnumerable<IReadOnlyCollection<PatreonMemberData>>, Error<string>>.FromT0(
+            GetMembersInternalAsync(campaignId));
+    }
+    
+    private async IAsyncEnumerable<IReadOnlyCollection<PatreonMemberData>> GetMembersInternalAsync(string campaignId)
+    {
+        _http.DefaultRequestHeaders.Clear();
+        _http.DefaultRequestHeaders.TryAddWithoutValidation("Authorization",
+            $"Bearer {accessToken}");
+
+        var page =
+            $"https://www.patreon.com/api/oauth2/v2/campaigns/{campaignId}/members"
+            + $"?fields%5Bmember%5D=full_name,currently_entitled_amount_cents,last_charge_date,last_charge_status"
+            + $"&fields%5Buser%5D=social_connections"
+            + $"&include=user"
+            + $"&sort=-last_charge_date";
+        PatreonMembersResponse data;
+
+        do
+        {
+            var res = await _http.GetStreamAsync(page);
+            data = await JsonSerializer.DeserializeAsync<PatreonMembersResponse>(res);
+
+            if (data is null)
+                break;
+
+            var userData = data.Data
+                               .Join(data.Included,
+                                   static m => m.Relationships.User.Data.Id,
+                                   static u => u.Id,
+                                   static (m, u) => new PatreonMemberData()
+                                   {
+                                       PatreonUserId = m.Relationships.User.Data.Id,
+                                       UserId = ulong.TryParse(
+                                           u.Attributes?.SocialConnections?.Discord?.UserId ?? string.Empty,
+                                           out var userId)
+                                           ? userId
+                                           : 0,
+                                       EntitledToCents = m.Attributes.CurrentlyEntitledAmountCents,
+                                       LastChargeDate = m.Attributes.LastChargeDate,
+                                       LastChargeStatus = m.Attributes.LastChargeStatus
+                                   })
+                               .ToArray();
+            
+            yield return userData;
+
+        } while (!string.IsNullOrWhiteSpace(page = data.Links?.Next));
+    }
+}