using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Localization;
using Microsoft.Extensions.Options;

using MongoDB.Entities;

using PrivaPub.ClientModels;
using PrivaPub.ClientModels.Admin;
using PrivaPub.Domain.Instance;
using PrivaPub.Domain.Media;
using PrivaPub.Domain.Moderation;
using PrivaPub.Domain.Privacy;
using PrivaPub.Domain.Social;
using PrivaPub.Extensions;
using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Relays;
using PrivaPub.Infrastructure;
using PrivaPub.Models;
using PrivaPub.Models.Federation;
using PrivaPub.Models.Social;
using PrivaPub.Models.User;
using PrivaPub.Resources;

namespace PrivaPub.Controllers.ClientToServer
{
	// The server's own settings from the administrator's page (completion program R5): what it says of itself, its rules,
	// its thumbnail, its media limits, whether its activity is published, its announcements and the relays it subscribes to.
	// Only an administrator, checked again against the database. Every change is kept in the staff's log.
	[ApiController,
		Route("clientapi/admin"),
		Authorize(Policy = Policies.IsAdmin)]
	public class InstanceAdminController : ControllerBase
	{
		const int MaxSettingsRelays = 20;
		const string Thumbnail = "thumbnail";

		readonly IInstanceSettings _settings;
		readonly IModerationLog _log;
		readonly IStringLocalizer _localizer;
		readonly ILocalActorService _localActors;
		readonly ILogger<InstanceAdminController> _logger;

		public InstanceAdminController(IInstanceSettings settings, IModerationLog log, IStringLocalizer<GenericRes> localizer, ILocalActorService localActors,
			ILogger<InstanceAdminController> logger)
		{
			_settings = settings;
			_log = log;
			_localizer = localizer;
			_localActors = localActors;
			_logger = logger;
		}

		// the token says administrator; the database has the last word
		async Task<RootUser> Administrator(CancellationToken token)
		{
			var root = await DB.Default.Find<RootUser>().MatchID(User.GetUserId()).ExecuteFirstAsync(token);
			return root is { IsBanned: false, DeletedAt: null } && root.Policies.Contains(Policies.IsAdmin) ? root : default;
		}

		IActionResult Refused(int status, string message) => StatusCode(status, new WebResult().Invalidate(_localizer[message], status));

		#region settings

		[HttpGet, Route("/clientapi/admin/settings")]
		public async Task<IActionResult> Settings(CancellationToken token)
		{
			if (await Administrator(token) == default)
				return Forbid();
			return Ok(await View(_settings.Current, token));
		}

		[HttpPost, Route("/clientapi/admin/settings")]
		public async Task<IActionResult> SaveSettings(ServerSettingsForm form, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			var contact = Clean(form.ContactAccountId);
			if (contact != default && !await IsContactable(contact, token))
				return Refused(StatusCodes.Status422UnprocessableEntity, "The contact account must be a persona of this server.");
			var rules = form.Rules ?? new();
			if (rules.Count > ServerSettingsForm.MaxRules || rules.Any(r => string.IsNullOrWhiteSpace(r?.Text)))
				return Refused(StatusCodes.Status422UnprocessableEntity, "Every rule needs its text, and there can be 50 at most.");

			var changed = new List<string>();
			var ruleActs = new List<(string Action, ServerRule Rule)>();
			var now = DateTime.UtcNow;
			var saved = await _settings.Update(settings =>
			{
				void Set(string name, string value, Func<string> get, Action<string> set)
				{
					if (get() == value)
						return;
					set(value);
					changed.Add(name);
				}
				Set("title", form.Title.Trim(), () => settings.Title, v => settings.Title = v);
				Set("short description", Clean(form.ShortDescription), () => settings.ShortDescription, v => settings.ShortDescription = v);
				Set("description", Clean(form.Description), () => settings.Description, v =>
				{
					settings.Description = v;
					settings.DescriptionUpdatedAt = now;
				});
				Set("contact email", Clean(form.ContactEmail), () => settings.ContactEmail, v => settings.ContactEmail = v);
				Set("contact account", contact, () => settings.ContactAccountId, v => settings.ContactAccountId = v);
				Set("privacy policy", Clean(form.PrivacyPolicy), () => settings.PrivacyPolicy, v =>
				{
					settings.PrivacyPolicy = v;
					settings.PrivacyPolicyUpdatedAt = now;
				});
				var terms = Clean(form.TermsOfService);
				Set("terms of service", terms, () => settings.TermsOfService, v => settings.TermsOfService = v);
				var effective = terms == default ? (DateTime?)null
					: form.TermsEffectiveAt is { } on ? DateTime.SpecifyKind(on.Date, DateTimeKind.Utc)
					: changed.Contains("terms of service") || settings.TermsEffectiveAt == default ? now.Date
					: settings.TermsEffectiveAt;
				if (effective != settings.TermsEffectiveAt)
				{
					settings.TermsEffectiveAt = effective;
					if (!changed.Contains("terms of service"))
						changed.Add("terms' date");
				}

				// rules: the form's order; a named rule keeps its id, a new one gets one, one left out is deleted but kept
				var existing = settings.Rules.GroupBy(r => r.Id).ToDictionary(g => g.Key, g => g.First());
				var listed = new HashSet<string>();
				var position = 0;
				foreach (var asked in rules)
				{
					var text = asked.Text.Trim();
					var hint = Clean(asked.Hint);
					if (asked.Id != default && existing.TryGetValue(asked.Id, out var rule) && listed.Add(rule.Id))
					{
						if (rule.Text != text || rule.Hint != hint || rule.DeletedAt != default)
							ruleActs.Add((AdminActions.RuleUpdate, rule));
						else if (rule.Position != position)
							changed.Add("rules' order");
						rule.Text = text;
						rule.Hint = hint;
						rule.DeletedAt = default;
						rule.Position = position++;
						continue;
					}
					var added = new ServerRule { Text = text, Hint = hint, Position = position++ };
					settings.Rules.Add(added);
					listed.Add(added.Id);
					ruleActs.Add((AdminActions.RuleInsert, added));
				}
				foreach (var gone in settings.Rules.Where(r => r.DeletedAt == default && !listed.Contains(r.Id)))
				{
					gone.DeletedAt = now;
					ruleActs.Add((AdminActions.RuleDelete, gone));
				}

				var media = form.Media ?? new();
				var limits = settings.Media ?? new();
				if (limits.QuotaBytesPerRoot != media.QuotaBytesPerRoot || limits.MaxImageBytes != media.MaxImageBytes
					|| limits.MaxVideoBytes != media.MaxVideoBytes || limits.MaxSeconds != media.MaxSeconds)
				{
					settings.Media = new ServerMediaLimits
					{
						QuotaBytesPerRoot = media.QuotaBytesPerRoot is { } quota ? Math.Max(0, quota) : (long?)null,
						MaxImageBytes = media.MaxImageBytes is { } image ? Math.Clamp(image, 1, MediaLimitsFromSettings.MaxImageBytes) : (long?)null,
						MaxVideoBytes = media.MaxVideoBytes is { } video ? Math.Clamp(video, 1, MediaLimitsFromSettings.MaxVideoBytes) : (long?)null,
						MaxSeconds = media.MaxSeconds is { } seconds ? Math.Clamp(seconds, 1, MediaLimitsFromSettings.MaxSeconds) : (int?)null
					};
					changed.Add("media limits");
				}
				if (settings.PublishActivity != form.PublishActivity)
				{
					settings.PublishActivity = form.PublishActivity;
					changed.Add(form.PublishActivity ? "activity published" : "activity unpublished");
				}
			}, admin.ID, token);

			if (changed.Count > 0)
				await _log.Write(admin.ID, AdminActions.SettingsUpdate, AdminTargets.Settings, ServerSettings.Name, saved.Title, note: string.Join(", ", changed), token: token);
			foreach (var (action, rule) in ruleActs)
				await _log.Write(admin.ID, action, AdminTargets.Rule, rule.Id, rule.Text, token: token);
			return Ok(await View(saved, token));
		}

		// the server's thumbnail (the instance API's), from a picture checked and re-encoded like a profile picture
		[HttpPost, Route("/clientapi/admin/settings/thumbnail"), RequestSizeLimit(MediaLimitsFromSettings.MaxImageBytes + 1024 * 1024),
			RequestFormLimits(MultipartBodyLengthLimit = MediaLimitsFromSettings.MaxImageBytes + 1024 * 1024)]
		public async Task<IActionResult> SaveThumbnail([FromServices] IMediaService media, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			var file = Request.HasFormContentType ? (await Request.ReadFormAsync(token)).Files["file"] : default;
			var outcome = await media.ServerImage(Thumbnail, file, token);
			if (!outcome.Ok)
				return StatusCode(outcome.Status, new WebResult().Invalidate(outcome.Error, outcome.Status));
			var previous = default(string);
			var saved = await _settings.Update(settings =>
			{
				previous = settings.ThumbnailMediaId;
				settings.ThumbnailMediaId = outcome.Attachment.ID;
				settings.ThumbnailUrl = media.Url(outcome.Attachment.FilePath);
			}, admin.ID, token);
			if (previous != default)
				await media.Trash(m => m.ID == previous && m.ServerUse == Thumbnail, "thumbnail replaced", token);
			await _log.Write(admin.ID, AdminActions.SettingsThumbnail, AdminTargets.Settings, ServerSettings.Name, saved.Title, note: "replaced", token: token);
			return Ok(await View(saved, token));
		}

		[HttpDelete, Route("/clientapi/admin/settings/thumbnail")]
		public async Task<IActionResult> DeleteThumbnail([FromServices] IMediaService media, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			var previous = default(string);
			var saved = await _settings.Update(settings =>
			{
				previous = settings.ThumbnailMediaId;
				settings.ThumbnailMediaId = default;
				settings.ThumbnailUrl = default;
			}, admin.ID, token);
			if (previous != default)
			{
				await media.Trash(m => m.ID == previous && m.ServerUse == Thumbnail, "thumbnail removed", token);
				await _log.Write(admin.ID, AdminActions.SettingsThumbnail, AdminTargets.Settings, ServerSettings.Name, saved.Title, note: "removed", token: token);
			}
			return Ok(await View(saved, token));
		}

		// a local persona whose login may act: the contact is shown to everyone as the one who runs the server
		static async Task<bool> IsContactable(string avatarId, CancellationToken token) =>
			await DB.Default.Find<Avatar>().Match(a => a.ID == avatarId && !a.DeletionAt.HasValue).ExecuteAnyAsync(token)
				&& !(await Counted.BarredPersonas(token)).Contains(avatarId);

		static string Clean(string text) => string.IsNullOrWhiteSpace(text) ? default : text.Trim();

		async Task<ViewServerSettings> View(ServerSettings settings, CancellationToken token)
		{
			var services = HttpContext.RequestServices;
			var configured = services.GetRequiredService<IConfiguration>().GetSection("Media").Get<MediaOptions>() ?? new MediaOptions();
			var effective = services.GetRequiredService<IOptionsMonitor<MediaOptions>>().CurrentValue;
			var contact = settings.ContactAccountId == default ? default
				: await DB.Default.Find<Avatar>().Match(a => a.ID == settings.ContactAccountId && !a.DeletionAt.HasValue).ExecuteFirstAsync(token);
			var updatedBy = settings.UpdatedBy == default || settings.UpdatedBy == AdminAction.Cli ? settings.UpdatedBy
				: (await DB.Default.Find<RootUser>().MatchID(settings.UpdatedBy).ExecuteFirstAsync(token))?.UserName;
			var limits = settings.Media ?? new();
			return new ViewServerSettings
			{
				Title = settings.Title,
				ShortDescription = settings.ShortDescription,
				Description = settings.Description,
				DescriptionUpdatedAt = settings.DescriptionUpdatedAt,
				ContactEmail = settings.ContactEmail,
				ContactAccountId = settings.ContactAccountId,
				ContactAccount = contact == default ? default : new ViewContactAccount
				{
					Id = contact.ID,
					UserName = contact.UserName,
					Name = contact.Name,
					Handle = _localActors.FromAvatar(contact).Handle
				},
				ThumbnailUrl = settings.ThumbnailUrl ?? $"{_localActors.BaseAddress}{ServerSettings.DefaultThumbnailPath}",
				ThumbnailIsDefault = settings.ThumbnailUrl == default,
				PrivacyPolicy = settings.PrivacyPolicy,
				PrivacyPolicyUpdatedAt = settings.PrivacyPolicyUpdatedAt,
				TermsOfService = settings.TermsOfService,
				TermsEffectiveAt = settings.TermsEffectiveAt,
				Rules = settings.Rules.OrderBy(r => r.DeletedAt != default).ThenBy(r => r.Position).Select(r => new ViewServerRule
				{
					Id = r.Id,
					Text = r.Text,
					Hint = r.Hint,
					Position = r.Position,
					IsDeleted = r.DeletedAt != default,
					DeletedAt = r.DeletedAt
				}).ToList(),
				Relays = await RelayViews(settings, token),
				Media = new ViewMediaLimits
				{
					QuotaBytesPerRoot = limits.QuotaBytesPerRoot,
					MaxImageBytes = limits.MaxImageBytes,
					MaxVideoBytes = limits.MaxVideoBytes,
					MaxSeconds = limits.MaxSeconds,
					ConfiguredQuotaBytesPerRoot = configured.QuotaBytesPerRoot,
					ConfiguredMaxImageBytes = configured.MaxImageBytes,
					ConfiguredMaxVideoBytes = configured.MaxVideoBytes,
					ConfiguredMaxSeconds = configured.MaxSeconds,
					EffectiveQuotaBytesPerRoot = effective.QuotaBytesPerRoot,
					EffectiveMaxImageBytes = effective.MaxImageBytes,
					EffectiveMaxVideoBytes = effective.MaxVideoBytes,
					EffectiveMaxSeconds = effective.MaxSeconds
				},
				RegistrationMode = services.GetRequiredService<IOptionsMonitor<RegistrationOptions>>().CurrentValue.Mode.ToString(),
				PublishActivity = settings.PublishActivity,
				UpdatedAt = settings.UpdatedAt,
				UpdatedBy = updatedBy
			};
		}

		#endregion

		#region announcements

		[HttpGet, Route("/clientapi/admin/announcements/list")]
		public async Task<IActionResult> Announcements([FromServices] IAnnouncements announcements, CancellationToken token)
		{
			if (await Administrator(token) == default)
				return Forbid();
			var views = new List<ViewAnnouncement>();
			foreach (var announcement in await announcements.All(token))
				views.Add(await View(announcement, token));
			return Ok(views);
		}

		[HttpPost, Route("/clientapi/admin/announcements/insert")]
		public async Task<IActionResult> InsertAnnouncement([FromServices] IAnnouncements announcements, AnnouncementForm form, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			if (Invalid(form) is { } refused)
				return refused;
			var made = await announcements.Insert(Draft(form), token);
			await _log.Write(admin.ID, AdminActions.AnnouncementInsert, AdminTargets.Announcement, made.ID, made.Text,
				note: made.IsPublished ? "published" : "draft", token: token);
			return Ok(await View(made, token));
		}

		[HttpPost, Route("/clientapi/admin/announcements/update")]
		public async Task<IActionResult> UpdateAnnouncement([FromServices] IAnnouncements announcements, AnnouncementForm form, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			if (Invalid(form) is { } refused)
				return refused;
			var updated = await announcements.Update(form.Id, Draft(form), token);
			if (updated == default)
				return NotFound();
			await _log.Write(admin.ID, AdminActions.AnnouncementUpdate, AdminTargets.Announcement, updated.ID, updated.Text,
				note: updated.IsPublished ? "published" : "draft", token: token);
			return Ok(await View(updated, token));
		}

		[HttpPost, Route("/clientapi/admin/announcements/delete")]
		public async Task<IActionResult> DeleteAnnouncement([FromServices] IAnnouncements announcements, [FromQuery] string id, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			var deleted = await announcements.Delete(id, token);
			if (deleted == default)
				return NotFound();
			await _log.Write(admin.ID, AdminActions.AnnouncementDelete, AdminTargets.Announcement, deleted.ID, deleted.Text, token: token);
			return Ok();
		}

		IActionResult Invalid(AnnouncementForm form) =>
			string.IsNullOrWhiteSpace(form.Text)
				? Refused(StatusCodes.Status422UnprocessableEntity, "An announcement needs its text.")
				: form.StartsAt != default && form.EndsAt != default && form.EndsAt < form.StartsAt
					? Refused(StatusCodes.Status422UnprocessableEntity, "An announcement can't end before it starts.")
					: default;

		static AnnouncementDraft Draft(AnnouncementForm form) => new(form.Text, form.StartsAt, form.EndsAt, form.AllDay, form.IsPublished);

		static async Task<ViewAnnouncement> View(Announcement announcement, CancellationToken token)
		{
			var reactions = await DB.Default.Find<AnnouncementReaction>().Match(r => r.AnnouncementId == announcement.ID).ExecuteAsync(token);
			return new ViewAnnouncement
			{
				Id = announcement.ID,
				Text = announcement.Text,
				Html = announcement.Html,
				StartsAt = announcement.StartsAt,
				EndsAt = announcement.EndsAt,
				AllDay = announcement.AllDay,
				IsPublished = announcement.IsPublished,
				IsShown = announcement.IsPublished && (announcement.EndsAt == default || announcement.EndsAt > DateTime.UtcNow),
				PublishedAt = announcement.PublishedAt,
				CreatedAt = announcement.CreatedAt,
				UpdatedAt = announcement.UpdatedAt,
				Reads = await DB.Default.CountAsync<AnnouncementRead>(r => r.AnnouncementId == announcement.ID, token),
				Reactions = reactions.GroupBy(r => r.Name).Select(g => new ViewAnnouncementReaction { Name = g.Key, Count = g.Count() }).ToList()
			};
		}

		#endregion

		#region relays

		[HttpGet, Route("/clientapi/admin/relays")]
		public async Task<IActionResult> Relays(CancellationToken token)
		{
			if (await Administrator(token) == default)
				return Forbid();
			return Ok(await RelayViews(_settings.Current, token));
		}

		// a relay named by the settings: subscribed to at once (in the background: resolving it is a fetch), the page polls
		[HttpPost, Route("/clientapi/admin/relays/insert")]
		public async Task<IActionResult> InsertRelay([FromServices] IRelays relays, RelayForm form, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			var address = form.Address?.Trim();
			if (!Uri.TryCreate(address, UriKind.Absolute, out var uri) || uri.Scheme != Uri.UriSchemeHttps || !string.IsNullOrEmpty(uri.UserInfo)
				|| !string.IsNullOrEmpty(uri.Fragment))
				return Refused(StatusCodes.Status422UnprocessableEntity, "A relay is named by the https address of its actor or its inbox.");
			if (relays.Configured.Contains(address))
				return Refused(StatusCodes.Status409Conflict, "The configuration names this relay already.");
			if (_settings.Current.Relays.Contains(address))
				return Ok(await RelayViews(_settings.Current, token));
			if (_settings.Current.Relays.Count >= MaxSettingsRelays)
				return Refused(StatusCodes.Status422UnprocessableEntity, "The settings name 20 relays at most.");
			var saved = await _settings.Update(settings =>
			{
				if (!settings.Relays.Contains(address))
					settings.Relays.Add(address);
			}, admin.ID, token);
			await _log.Write(admin.ID, AdminActions.RelayInsert, AdminTargets.Relay, address, address, token: token);
			Reconcile(relays);
			return Accepted(await RelayViews(saved, token));
		}

		// a relay the settings named: unsubscribed at once (its Undo is queued); the configuration's are removed only there
		[HttpPost, Route("/clientapi/admin/relays/delete")]
		public async Task<IActionResult> DeleteRelay([FromServices] IRelays relays, [FromQuery] string address, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			address = address?.Trim();
			if (relays.Configured.Contains(address))
				return Refused(StatusCodes.Status409Conflict, "This relay is named by the configuration (Federation:Relays): remove it there.");
			if (string.IsNullOrEmpty(address) || !_settings.Current.Relays.Contains(address))
				return NotFound();
			var saved = await _settings.Update(settings => settings.Relays.Remove(address), admin.ID, token);
			await _log.Write(admin.ID, AdminActions.RelayDelete, AdminTargets.Relay, address, address, token: token);
			Reconcile(relays);
			return Accepted(await RelayViews(saved, token));
		}

		void Reconcile(IRelays relays) => _ = Task.Run(async () =>
		{
			try
			{
				await relays.Reconcile(CancellationToken.None);
			}
			catch (Exception ex)
			{
				_logger.LogWarning(ex, "Relay subscriptions could not be brought up to date");
			}
		}, CancellationToken.None);

		async Task<List<ViewRelay>> RelayViews(ServerSettings settings, CancellationToken token)
		{
			var configured = HttpContext.RequestServices.GetRequiredService<IRelays>().Configured;
			var subscriptions = (await DB.Default.Find<RelaySubscription>().ExecuteAsync(token)).GroupBy(s => s.Configured).ToDictionary(g => g.Key, g => g.First());
			ViewRelay View(string address, string source)
			{
				var subscription = subscriptions.GetValueOrDefault(address);
				return new ViewRelay
				{
					Address = address,
					Source = source,
					State = subscription == default ? "none" : subscription.State.ToString().ToLowerInvariant(),
					ActorURI = subscription?.ActorURI,
					RequestedAt = subscription?.RequestedAt,
					AnsweredAt = subscription?.AnsweredAt
				};
			}
			return configured.Select(a => View(a, "configuration"))
				.Concat((settings.Relays ?? new()).Where(a => !configured.Contains(a)).Select(a => View(a, "settings")))
				.ToList();
		}

		#endregion
	}
}