using System.Net.Http.Headers;
using Foxchat.Core.Models;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;

namespace Foxchat.Core.Federation;

public partial class RequestSigningService
{
    public const string USER_AGENT_HEADER = "User-Agent";
    public const string USER_AGENT = "Foxchat.NET";
    public const string DATE_HEADER = "Date";

    public const string SERVER_HEADER = "X-Foxchat-Server";
    public const string SIGNATURE_HEADER = "X-Foxchat-Signature";
    public const string USER_HEADER = "X-Foxchat-User";

    private static readonly JsonSerializerSettings _jsonSerializerSettings = new()
    {
        ContractResolver = new DefaultContractResolver
        {
            NamingStrategy = new SnakeCaseNamingStrategy()
        }
    };

    public async Task<T> RequestAsync<T>(HttpMethod method, string domain, string requestPath, string? userId = null, object? body = null)
    {
        var request = BuildHttpRequest(method, domain, requestPath, userId, body);
        var resp = await _httpClient.SendAsync(request);
        if (!resp.IsSuccessStatusCode)
        {
            var error = await resp.Content.ReadAsStringAsync();
            throw new ApiError.OutgoingFederationError($"Request to {domain}{requestPath} returned an error", DeserializeObject<Models.ApiError>(error));
        }

        var bodyString = await resp.Content.ReadAsStringAsync();
        return DeserializeObject<T>(bodyString)
            ?? throw new ApiError.OutgoingFederationError($"Request to {domain}{requestPath} returned invalid response body");
    }

    private HttpRequestMessage BuildHttpRequest(HttpMethod method, string domain, string requestPath, string? userId = null, object? bodyData = null)
    {
        var body = bodyData != null ? SerializeObject(bodyData) : null;

        var now = _clock.GetCurrentInstant();
        var url = $"https://{domain}{requestPath}";
        var signature = GenerateSignature(new SignatureData(now, domain, requestPath, body?.Length, userId));

        var request = new HttpRequestMessage(method, url);
        request.Headers.Clear();
        request.Headers.Add(USER_AGENT_HEADER, USER_AGENT);
        request.Headers.Add(DATE_HEADER, FormatTime(now));
        request.Headers.Add(SERVER_HEADER, _config.Domain);
        request.Headers.Add(SIGNATURE_HEADER, signature);
        if (userId != null)
            request.Headers.Add(USER_HEADER, userId);
        if (body != null)
            request.Content = new StringContent(body, new MediaTypeHeaderValue("application/json", "utf-8"));

        return request;
    }

    public static string SerializeObject(object data) => JsonConvert.SerializeObject(data, _jsonSerializerSettings);
    public static T? DeserializeObject<T>(string data) => JsonConvert.DeserializeObject<T>(data, _jsonSerializerSettings);
}