Catalogger.NET/Catalogger.Backend/Services/NewsService.cs

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// Copyright (C) 2021-present sam (starshines.gay)
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
using Catalogger.Backend.Extensions;
using NodaTime;
using NodaTime.Extensions;
using Remora.Discord.API;
using Remora.Discord.API.Abstractions.Objects;
using Remora.Discord.API.Abstractions.Rest;
namespace Catalogger.Backend.Services;
public class NewsService(
Config config,
ILogger logger,
IDiscordRestChannelAPI channelApi,
IClock clock
)
{
private static readonly Duration MaxNewsAge = Duration.FromDays(90); // 3 months
private static readonly Duration ExpiresAfter = Duration.FromHours(1);
private readonly ILogger _logger = logger.ForContext<NewsService>();
private List<IMessage>? _messages;
private readonly SemaphoreSlim _lock = new(1);
private bool _isExpired => clock.GetCurrentInstant() > clock.GetCurrentInstant() + ExpiresAfter;
public async Task<IEnumerable<NewsMessage>> GetNewsAsync()
{
if (_messages != null && !_isExpired)
return _messages.Select(FormatIMessage);
var messages = await GetRawNewsAsync();
return messages.Select(FormatIMessage);
}
public void AddMessage(IMessage message) =>
_messages = _messages?.Take(4).Prepend(message).ToList();
private async Task<List<IMessage>> GetRawNewsAsync()
{
await _lock.WaitAsync();
try
{
if (config.Web.NewsChannel == null)
return [];
_logger.Information("Fetching news from channel {ChannelId}", config.Web.NewsChannel);
var res = await channelApi.GetChannelMessagesAsync(
DiscordSnowflake.New(config.Web.NewsChannel.Value),
limit: 5
);
if (res.IsSuccess)
return _messages = res
.Entity.Where(m =>
m.ID.Timestamp.ToInstant() > clock.GetCurrentInstant() - MaxNewsAge
)
.ToList();
return [];
}
finally
{
_lock.Release();
}
}
public record NewsMessage(
string Author,
string Content,
IEnumerable<string> AttachmentUrls,
DateTimeOffset PostedAt,
DateTimeOffset? EditedAt
);
private NewsMessage FormatIMessage(IMessage msg) =>
new(
msg.Author.Tag(),
msg.Content,
msg.Attachments.Select(a => a.Url),
msg.ID.Timestamp,
msg.EditedTimestamp
);
}