CatsOfMastodon/Services/PostResolver.cs

using System.Text.Json;
using Microsoft.Extensions.Logging;
using mstdnCats.Models;

namespace mstdnCats.Services;

public sealed class PostResolver
{
    public static async Task<List<Post>?> GetPostsAsync(string tag, ILogger<MastodonBot>? logger, string instance)
    {
        // Get posts
        var _httpClient = new HttpClient();
        // Get posts from mastodon api (40 latest posts)
        var requestUrl = $"{instance}/api/v1/timelines/tag/{tag}?limit=40";
        var response = await _httpClient.GetAsync(requestUrl);

        // Print out ratelimit info
        var remainingTime = int.Parse(response.Headers.GetValues("X-RateLimit-Remaining").First());
        var resetTime = DateTime.Parse(response.Headers.GetValues("X-RateLimit-Reset").First());
        var diff = resetTime - DateTime.UtcNow;
        logger?.LogInformation($"Remaining requests: {remainingTime}, ratelimit reset in {diff.Hours} hours {diff.Minutes} minutes {diff.Seconds} seconds");

        // Check if response is ok
        if (
            response.StatusCode == System.Net.HttpStatusCode.OK ||
            response.Content.Headers.ContentType.MediaType.Contains("application/json") ||
            (response.Headers.TryGetValues("X-RateLimit-Remaining", out var remaining) &&
             int.Parse(remaining.First()) != 0)
        )
        {
            // Deserialize response based on 'Post' model
            return JsonSerializer.Deserialize<List<Post>>(await response.Content.ReadAsStringAsync());
        }

        else
        {
            logger?.LogCritical("Error while getting posts: " + response.StatusCode);
            return null;
        }
    }
}