using MongoDB.Entities;

using PrivaPub.ClientModels;
using PrivaPub.ClientModels.User;
using PrivaPub.ClientModels.User.Avatar;
using PrivaPub.Infrastructure.Backup;
using PrivaPub.Models.User;
using PrivaPub.Services;
using PrivaPub.Services.ClientToServer.Private;
using PrivaPub.StaticServices;

using System.ComponentModel.DataAnnotations;
using System.Security.Cryptography;

namespace PrivaPub.Infrastructure.Cli
{
	// `PrivaPub admin ...` runs with the whole server built but not started: no Kestrel, no hosted services.
	public static class AdminCommands
	{
		public const string SmokeLogin = "deploy-smoke";

		const string Usage = """
			usage: PrivaPub admin promote|demote <root>
			       PrivaPub admin create-root <login> [--admin]   the password is read from standard input
			       PrivaPub admin smoke <persona>                 prints "<login> <password>" for the deploy's signed-in check
			       PrivaPub admin media audit [--fix]             media files against what holds them; --fix (as www-data) trashes
			                                                      what nothing holds and gives today's pictures their rows
			       PrivaPub admin backup [--kind manual|pre-deploy] [--db-only]
			                                                      backs the server up; --db-only lists the media without
			                                                      linking them (the deploy's, which can't link www-data's files)
			       PrivaPub admin backups                         the backups kept, newest first
			       PrivaPub admin backup verify <id>              whether a backup's files are what its manifest says
			       PrivaPub admin restore <id>                    restores a backup: the service stops within seconds and
			                                                      restores it when systemd starts it again; everyone signs
			                                                      in again, and what was made since is lost, except what
			                                                      protects (blocks, deletions, ...)
			       PrivaPub admin restore --status                the restore waiting, and the last one done
			""";

		/// <summary>Whether a command runs before migrations: backups are of the database as it was.</summary>
		public static bool BeforeMigrations(string[] args) => args is ["backup", ..] or ["backups"] or ["restore", ..];

		public static async Task<int> Run(string[] args, IServiceProvider services, TextReader input = default, TextWriter output = default)
		{
			input ??= Console.In;
			output ??= Console.Out;
			switch (args)
			{
				case [("promote" or "demote") and var verb, var userName]:
					return await Promote(verb == "promote", userName, output);
				case ["create-root", var login, .. var flags] when flags.All(f => f == "--admin"):
					return await CreateRoot(services, login, input.ReadLine(), flags.Contains("--admin"), output);
				case ["smoke", var persona]:
					return await Smoke(services, persona, output);
				case ["media", "audit", .. var flags] when flags.All(f => f == "--fix"):
					return await AuditMedia(services, flags.Contains("--fix"), output);
				case ["backup", "verify", var id]:
					return await VerifyBackup(services, id, output);
				case ["backup", .. var flags] when BackupFlags(flags, out var kind, out var dbOnly):
					return await BackUp(services, kind, dbOnly, output);
				case ["backups"]:
					return ListBackups(services, output);
				case ["restore", "--status"]:
					return await RestoreStatus(services, output);
				case ["restore", var id] when !id.StartsWith('-'):
					return await Restore(services, id, output);
				default:
					Console.Error.WriteLine(Usage);
					return 2;
			}
		}

		static readonly string[] CommandKinds = ["manual", "pre-deploy"];

		static bool BackupFlags(string[] flags, out string kind, out bool dbOnly)
		{
			kind = "manual";
			dbOnly = false;
			for (var i = 0; i < flags.Length; i++)
				switch (flags[i])
				{
					case "--db-only":
						dbOnly = true;
						break;
					case "--kind" when i + 1 < flags.Length && CommandKinds.Contains(flags[i + 1]):
						kind = flags[++i];
						break;
					default:
						return false;
				}
			return true;
		}

		static async Task<int> BackUp(IServiceProvider services, string kind, bool dbOnly, TextWriter output)
		{
			var (made, error) = await services.GetRequiredService<Backups>().Create(kind, dbOnly, CancellationToken.None);
			if (made == default)
			{
				Console.Error.WriteLine(error);
				return 1;
			}
			var manifest = made.Manifest;
			output.WriteLine($"{made.Id}: {manifest.Collections.Count} collections, {manifest.Collections.Sum(c => c.Count)} documents, {made.Bytes / 1024} KiB");
			output.WriteLine(dbOnly
				? $"{manifest.Media.List.Count} media files listed, not linked"
				: $"{manifest.Media.Files} media files, {manifest.Media.Bytes / 1024 / 1024} MiB, {manifest.Media.Missing} missing");
			if (!manifest.Consistent)
				output.WriteLine("not read at one instant: Mongo is not a replica set");
			return 0;
		}

		static int ListBackups(IServiceProvider services, TextWriter output)
		{
			foreach (var backup in services.GetRequiredService<Backups>().List())
				output.WriteLine($"{backup.Id}\t{backup.Kind}\t{backup.CreatedAt:u}\t{backup.Bytes / 1024} KiB\t{backup.Manifest?.Media.Files ?? 0} media{(backup.Manifest?.DbOnly == true ? " (listed)" : string.Empty)}");
			return 0;
		}

		static async Task<int> VerifyBackup(IServiceProvider services, string id, TextWriter output)
		{
			var problems = await services.GetRequiredService<Backups>().Verify(id, CancellationToken.None);
			foreach (var problem in problems)
				output.WriteLine(problem);
			if (problems.Count > 0)
				return 1;
			output.WriteLine($"{id}: whole");
			return 0;
		}

		static async Task<int> Restore(IServiceProvider services, string id, TextWriter output)
		{
			var backups = services.GetRequiredService<Backups>();
			var refused = await ServerRestore.Request(backups.Context(), id, "cli", CancellationToken.None);
			if (refused != default)
			{
				Console.Error.WriteLine(refused);
				return 1;
			}
			output.WriteLine($"{id} will be restored: the running service stops within seconds and restores it when it starts again");
			output.WriteLine("(systemd starts it again; follow it with journalctl -u privapub, then PrivaPub admin restore --status)");
			return 0;
		}

		static async Task<int> RestoreStatus(IServiceProvider services, TextWriter output)
		{
			var waiting = RestoreMarker.Read(services.GetRequiredService<Backups>().Root);
			if (waiting != default)
				output.WriteLine($"waiting: {waiting.Backup}, {waiting.State}, attempt {waiting.Attempts} of {RestoreMarker.MaxAttempts}, asked by {waiting.RequestedBy} at {waiting.RequestedAt:u}{(waiting.Error == default ? string.Empty : $": {waiting.Error}")}");
			var last = await DB.Default.Find<RestoreRecord>().Sort(r => r.RestoredAt, Order.Descending).ExecuteFirstAsync();
			if (last == default)
			{
				if (waiting == default)
					output.WriteLine("no restore asked for, none done");
				return 0;
			}
			if (last.Abandoned)
			{
				output.WriteLine($"last: {last.Backup} abandoned at {last.RestoredAt:u}, nothing changed: {last.Error}");
				return 0;
			}
			var report = last.Report;
			output.WriteLine($"last: {last.Backup} (made {last.BackupCreatedAt:u}) restored at {last.RestoredAt:u}, asked by {last.RequestedBy}; before it: {last.PreRestore}");
			output.WriteLine($"  {report.Documents} documents in {report.Collections} collections, {report.MediaRestored} media files brought back, {report.MediaMissing} missing");
			output.WriteLine($"  deleted again: {report.RootsDeleted} roots, {report.PersonasDeleted} personas, {report.GroupsDeleted} groups, {report.PostsDeleted} posts");
			output.WriteLine($"  made since, now deleted: roots {Names(report.RootsTombstoned)}, personas {Names(report.PersonasTombstoned)}, groups {Names(report.GroupsTombstoned)}; {report.PostsGone} posts gone");
			output.WriteLine($"  {report.ProtectiveKept} protective rows kept, {report.MediaTrashed} media trashed, {report.SessionsEnded} sessions ended");
			return 0;
		}

		static string Names(List<string> names) => names.Count == 0 ? "none" : string.Join(", ", names);

		static async Task<int> AuditMedia(IServiceProvider services, bool fix, TextWriter output)
		{
			var report = await Domain.Media.MediaAudit.Run(services.GetRequiredService<Domain.Media.IMediaService>(), fix, CancellationToken.None);
			output.WriteLine($"{report.Files} files served, {report.Held} rows holding media");
			output.WriteLine($"{report.Adopted} pictures personas show without a row{(fix ? ": given one" : string.Empty)}");
			output.WriteLine($"{report.OfDeleted} media of deleted posts or personas{(fix ? ": trashed" : string.Empty)}");
			output.WriteLine($"{report.MissingFiles} rows whose files are missing{(fix ? ": trashed" : string.Empty)}");
			output.WriteLine($"{report.Unheld} files nothing holds{(fix ? ": trashed" : string.Empty)}");
			foreach (var example in report.Examples)
				output.WriteLine($"  {example}");
			if (!fix && report.Adopted + report.OfDeleted + report.MissingFiles + report.Unheld > 0)
				output.WriteLine("run again with --fix, as www-data, to apply this; trashed files are deleted after a day");
			return 0;
		}

		static async Task<int> Promote(bool promote, string userName, TextWriter output)
		{
			userName = userName.ToLowerInvariant();
			var user = await DB.Default.Find<RootUser>().Match(u => u.UserName == userName).ExecuteFirstAsync();
			if (user == default)
			{
				Console.Error.WriteLine($"no root user '{userName}'");
				return 1;
			}

			user.Policies.RemoveAll(p => p is Policies.IsAdmin or Policies.IsModerator);
			if (promote)
				user.Policies.AddRange(new[] { Policies.IsAdmin, Policies.IsModerator });
			if (!user.Policies.Contains(Policies.IsUser))
				user.Policies.Add(Policies.IsUser);
			user.UpdatedAt = DateTime.UtcNow;
			await DB.Default.SaveAsync(user);

			output.WriteLine($"{userName}: {string.Join(", ", user.Policies)}");
			return 0;
		}

		// With sign-up closed this is how the first root is made; group invitations make the rest.
		static async Task<int> CreateRoot(IServiceProvider services, string login, string password, bool admin, TextWriter output)
		{
			var form = new LoginForm { UserName = login, Password = password?.Trim() };
			var problems = new List<ValidationResult>();
			if (!Validator.TryValidateObject(form, new ValidationContext(form), problems, validateAllProperties: true))
			{
				Console.Error.WriteLine(string.Join(Environment.NewLine, problems.Select(p => p.ErrorMessage)));
				return 1;
			}
			var created = await services.GetRequiredService<IRootUsersService>().SignUpAsync(form);
			if (!created.IsValid)
			{
				Console.Error.WriteLine(created.ErrorMessage);
				return 1;
			}
			return admin ? await Promote(true, login, output) : await Report(login, output);
		}

		static Task<int> Report(string login, TextWriter output)
		{
			output.WriteLine($"{login.ToLowerInvariant()}: created");
			return Task.FromResult(0);
		}

		// The deploy's signed-in smoke check: a root nobody signs in to by hand, owning one undiscoverable persona. Every run
		// sets a new password and prints it, so no secret is kept anywhere and nothing waits on a person.
		static async Task<int> Smoke(IServiceProvider services, string personaName, TextWriter output)
		{
			personaName = personaName.ToLowerInvariant();
			var password = "Smoke-x" + Convert.ToHexStringLower(RandomNumberGenerator.GetBytes(24));
			var root = await DB.Default.Find<RootUser>().Match(u => u.UserName == SmokeLogin).ExecuteFirstAsync();
			if (root == default)
			{
				var created = await services.GetRequiredService<IRootUsersService>().SignUpAsync(new LoginForm { UserName = SmokeLogin, Password = password });
				if (!created.IsValid)
				{
					Console.Error.WriteLine(created.ErrorMessage);
					return 1;
				}
				root = await DB.Default.Find<RootUser>().Match(u => u.UserName == SmokeLogin).ExecuteFirstAsync();
			}
			else if (root.DeletedAt.HasValue || root.IsBanned)
			{
				Console.Error.WriteLine($"the root '{SmokeLogin}' is deleted or banned");
				return 1;
			}
			else
				await DB.Default.Update<RootUser>().MatchID(root.ID)
					.Modify(u => u.HashedPassword, services.GetRequiredService<IPasswordHasher>().Hash(password))
					.Modify(u => u.UpdatedAt, DateTime.UtcNow)
					.ExecuteAsync();

			var owned = (await DB.Default.Find<RootToAvatar>().Match(ra => ra.RootId == root.ID).ExecuteAsync()).Select(ra => ra.AvatarId).ToList();
			var persona = await DB.Default.Find<Avatar>().Match(a => owned.Contains(a.ID) && a.UserName == personaName && !a.DeletionAt.HasValue).ExecuteFirstAsync();
			if (persona == default)
			{
				var inserted = await services.GetRequiredService<IPrivateAvatarUsersService>().InsertAvatar(new InsertAvatarForm
				{
					RootId = root.ID,
					UserName = personaName,
					Name = personaName,
					Biography = "The deploy signs in here to check that the Mastodon API works for a signed-in persona."
				});
				if (!inserted.IsValid)
				{
					Console.Error.WriteLine(inserted.ErrorMessage);
					return 1;
				}
				persona = await DB.Default.Find<Avatar>().MatchID(((ViewAvatar)inserted.Data).Id).ExecuteFirstAsync();
			}
			await DB.Default.Update<Avatar>().MatchID(persona.ID)
				.Modify(a => a.Settings.IsDiscoverable, false)
				.Modify(a => a.Settings.IsIndexable, false)
				.ExecuteAsync();

			output.WriteLine($"{SmokeLogin} {password}");
			return 0;
		}
	}
}