MessagePoster.cs

namespace Pacsource.Util;

using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Net.Http.Json;
using System.Threading.Tasks;

public class MessagePoster {
    private static readonly string tgTk = "";
    private static readonly string tgChan = "";
    private static readonly  string maxTk = "";
    private static readonly  string maxChan = "";

    public static async Task<string> SendTgMessageAsync(string text) {
        if (text is null) throw new ArgumentNullException(nameof(text));

        using var http = new HttpClient();
        http.BaseAddress = new Uri($"https://api.telegram.org/bot{tgTk}/");

        var payload = new {
            chat_id = tgChan,
            text,
            parse_mode = "MarkdownV2"
        };

        using var resp = await http.PostAsJsonAsync("sendMessage", payload).ConfigureAwait(false);
        resp.EnsureSuccessStatusCode();
        return await resp.Content.ReadAsStringAsync().ConfigureAwait(false);
    }

    public static async Task<string> SendMaxMessageAsync(string text) {
        if (text is null) throw new ArgumentNullException(nameof(text));

        using var http = new HttpClient();
        http.BaseAddress = new Uri("https://platform-api.max.ru/");

        http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Authorization", maxTk);

        var payload = new {
            chat_id = maxChan,
            text,
            format = "markdown"
        };

        using var resp = await http.PostAsJsonAsync("messages", payload).ConfigureAwait(false);
        resp.EnsureSuccessStatusCode();
        return await resp.Content.ReadAsStringAsync().ConfigureAwait(false);
    }

    public static async Task SendMessageAsync(string text) {
        // await SendMaxMessageAsync(text);
        await SendTgMessageAsync(text);
    }
}