using System.Diagnostics.CodeAnalysis;
using JetBrains.Annotations;

namespace Foxnouns.Backend.Services;

public class RemoteAuthService(Config config, ILogger logger)
{
    private readonly ILogger _logger = logger.ForContext<RemoteAuthService>();
    private readonly HttpClient _httpClient = new();

    private readonly Uri _discordTokenUri = new("https://discord.com/api/oauth2/token");
    private readonly Uri _discordUserUri = new("https://discord.com/api/v10/users/@me");

    public async Task<RemoteUser> RequestDiscordTokenAsync(
        string code,
        CancellationToken ct = default
    )
    {
        var redirectUri = $"{config.BaseUrl}/auth/callback/discord";
        var resp = await _httpClient.PostAsync(
            _discordTokenUri,
            new FormUrlEncodedContent(
                new Dictionary<string, string>
                {
                    { "client_id", config.DiscordAuth.ClientId! },
                    { "client_secret", config.DiscordAuth.ClientSecret! },
                    { "grant_type", "authorization_code" },
                    { "code", code },
                    { "redirect_uri", redirectUri },
                }
            ),
            ct
        );
        if (!resp.IsSuccessStatusCode)
        {
            var respBody = await resp.Content.ReadAsStringAsync(ct);
            _logger.Error(
                "Received error status {StatusCode} when exchanging OAuth token: {ErrorBody}",
                (int)resp.StatusCode,
                respBody
            );
            throw new FoxnounsError("Invalid Discord OAuth response");
        }

        resp.EnsureSuccessStatusCode();
        var token = await resp.Content.ReadFromJsonAsync<DiscordTokenResponse>(ct);
        if (token == null)
            throw new FoxnounsError("Discord token response was null");

        var req = new HttpRequestMessage(HttpMethod.Get, _discordUserUri);
        req.Headers.Add("Authorization", $"{token.token_type} {token.access_token}");

        var resp2 = await _httpClient.SendAsync(req, ct);
        resp2.EnsureSuccessStatusCode();
        var user = await resp2.Content.ReadFromJsonAsync<DiscordUserResponse>(ct);
        if (user == null)
            throw new FoxnounsError("Discord user response was null");

        return new RemoteUser(user.id, user.username);
    }

    [SuppressMessage(
        "ReSharper",
        "InconsistentNaming",
        Justification = "Easier to use snake_case here, rather than passing in JSON converter options"
    )]
    [UsedImplicitly]
    private record DiscordTokenResponse(string access_token, string token_type);

    [SuppressMessage(
        "ReSharper",
        "InconsistentNaming",
        Justification = "Easier to use snake_case here, rather than passing in JSON converter options"
    )]
    [UsedImplicitly]
    private record DiscordUserResponse(string id, string username);

    public record RemoteUser(string Id, string Username);
}