using System.Net;

using collAnon.Client.Services;

using decePubClient.Extensions;
using decePubClient.Helpers;
using decePubClient.Models;
using decePubClient.Models.Mastodon;

using PrivaPub.ClientModels;
using PrivaPub.ClientModels.User;
using PrivaPub.ClientModels.User.Avatar;

namespace decePubClient.Services
{
	/// <summary>
	/// One sign-in for both of PrivaPub's APIs: the root signs in on /clientapi, then each persona it uses gets its own
	/// Mastodon token in exchange for the JWT (PrivaPub's PersonaExchange), so the Mastodon API never learns the root.
	/// Results are WebResults, lists come back empty on failure; nothing throws.
	/// </summary>
	public class AuthService(IHttpService httpService, TokenAuthStateProvider authStateProvider, AppConfiguration appConfiguration,
		ILoggingService logger, CoalescingStringLocalizer localizer)
	{
		/// <summary>The JWT is renewed (sniff/again) once less than this, or a quarter of its lifetime, is left.</summary>
		static readonly TimeSpan RenewBefore = TimeSpan.FromDays(2);

		/// <summary>Signs the root in; the JWT never goes with the request (PrivaPub redirects a login that carries one).</summary>
		public async Task<WebResult> Login(LoginForm form, CancellationToken cancellationToken = default)
		{
			using var response = await httpService.PostTotallyAnon(APIs.ClientApi.POST_Login, form, cancellationToken: cancellationToken);
			if (!response.IsSuccessStatusCode)
				return await response.Content.ReadWebResult(response.StatusCode, localizer, cancellationToken);

			var jwtUser = await response.DefaultReadFromJsonAsync<JwtUser>(cancellationToken);
			if (string.IsNullOrEmpty(jwtUser?.Token))
				return new WebResult().Invalidate(localizer["The server sent an invalid response."], (int)HttpStatusCode.BadGateway);

			await authStateProvider.SetSession(jwtUser, cancellationToken);
			return new WebResult { Data = jwtUser };
		}

		/// <summary>The root's personas.</summary>
		public async Task<List<ViewAvatar>> Personas(CancellationToken cancellationToken = default)
		{
			using var response = await httpService.Get(APIs.ClientApi.GET_Personas, cancellationToken: cancellationToken);
			if (!response.IsSuccessStatusCode)
			{
				await LogFailure(response, nameof(Personas), cancellationToken);
				return [];
			}

			return await response.DefaultReadFromJsonAsync<List<ViewAvatar>>(cancellationToken) ?? [];
		}

		/// <summary>Acts as the persona from now on, exchanging a token for it unless it has one.</summary>
		public async Task<WebResult> UsePersona(string personaId, CancellationToken cancellationToken = default)
		{
			var session = await authStateProvider.GetAuthData(cancellationToken);
			if (session.PersonaTokens.ContainsKey(personaId))
			{
				await authStateProvider.SetPersona(personaId, cancellationToken: cancellationToken);
				return new();
			}

			using var response = await httpService.ExchangePersonaToken(personaId, cancellationToken);
			return response.IsSuccessStatusCode ? new() : await response.Content.ReadWebResult(response.StatusCode, localizer, cancellationToken);
		}

		/// <summary>The current persona's Mastodon account, or null.</summary>
		public async Task<Account> CurrentAccount(CancellationToken cancellationToken = default)
		{
			using var response = await httpService.Get(APIs.Mastodon.GET_VerifyCredentials, cancellationToken: cancellationToken);
			if (!response.IsSuccessStatusCode)
			{
				await LogFailure(response, nameof(CurrentAccount), cancellationToken);
				return null;
			}

			return await response.MastodonReadFromJsonAsync<Account>(cancellationToken);
		}

		/// <summary>Renews the JWT when it is about to expire; persona tokens do not expire and are kept.</summary>
		public async Task RefreshIfNeeded(CancellationToken cancellationToken = default)
		{
			var session = await authStateProvider.GetAuthData(cancellationToken);
			if (session.TokenExpiration is not { } expiration)
				return;
			var lifetime = session.TokenIssuedAt is { } issued ? TimeSpan.FromTicks(expiration - issued) : RenewBefore * 4;
			var renewBefore = lifetime / 4 < RenewBefore ? lifetime / 4 : RenewBefore;
			if (new DateTime(expiration, DateTimeKind.Utc) - DateTime.UtcNow > renewBefore)
				return;
			if (await authStateProvider.GetToken(cancellationToken) is null)
				return;

			using var response = await httpService.Get(APIs.ClientApi.GET_SniffAgain, cancellationToken: cancellationToken);
			if (!response.IsSuccessStatusCode)
			{
				await LogFailure(response, nameof(RefreshIfNeeded), cancellationToken);
				return;
			}

			var jwtUser = await response.DefaultReadFromJsonAsync<JwtUser>(cancellationToken);
			if (!string.IsNullOrEmpty(jwtUser?.Token))
				await authStateProvider.SetSession(jwtUser, cancellationToken);
		}

		/// <summary>Revokes every persona token the client holds, tells PrivaPub, then forgets the session and the local data.</summary>
		public async Task Logout(CancellationToken cancellationToken = default)
		{
			var session = await authStateProvider.GetAuthData(cancellationToken);
			foreach (var token in session.PersonaTokens.Values)
			{
				using var revoked = await httpService.PostTotallyAnon(APIs.OAuth.POST_Revoke, new Dictionary<string, string>
				{
					["token"] = token,
					["client_id"] = appConfiguration.ClientId
				}, cancellationToken: cancellationToken);
				if (!revoked.IsSuccessStatusCode)
					await LogFailure(revoked, nameof(Logout), cancellationToken);
			}

			if (await authStateProvider.GetToken(cancellationToken) is not null)
			{
				using var response = await httpService.Get(APIs.ClientApi.GET_Logout, cancellationToken: cancellationToken);
				if (!response.IsSuccessStatusCode)
					await LogFailure(response, nameof(Logout), cancellationToken);
			}

			await authStateProvider.LogoutAsync(deleteDb: true, cancellationToken);
		}

		async Task LogFailure(HttpResponseMessage response, string caller, CancellationToken cancellationToken)
		{
			var result = await response.Content.ReadWebResult(response.StatusCode, localizer, cancellationToken);
			if (result.StatusCode is not (int)HttpStatusCode.Gone)
				await logger.ProcessWarning(result.ToString(localizer), $"{nameof(AuthService)}.{caller}", cancellationToken);
		}
	}
}