using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Localization;
using Microsoft.Net.Http.Headers;

using MongoDB.Entities;

using PrivaPub.ClientModels;
using PrivaPub.ClientModels.Admin;
using PrivaPub.Extensions;
using PrivaPub.Infrastructure.Backup;
using PrivaPub.Models.User;
using PrivaPub.Resources;
using PrivaPub.StaticServices;

namespace PrivaPub.Controllers.ClientToServer
{
	// The server's backups from the administrator's page (owner decision 2026-10-07: it backs up and restores too). Only
	// an administrator, checked again against the database; a download and a restore ask for the password again, and a
	// restore for the server's host typed out. A restore asked for stops the service within seconds, and the next start
	// carries it out (ServerRestore).
	[ApiController,
		Route("clientapi/admin/backups"),
		Authorize(Policy = Policies.IsAdmin)]
	public class BackupController(Backups backups, TransferStore transfers, IPasswordHasher hasher, IStringLocalizer<GenericRes> localizer,
		ILogger<BackupController> logger) : ControllerBase
	{
		[HttpGet, Route("")]
		public async Task<IActionResult> List(CancellationToken token)
		{
			if (await Administrator(token) == default)
				return Forbid();
			var deleted = await DB.Default.Find<RootUser>().Match(u => u.DeletedAt != null).Project(u => u.Include(x => x.DeletedAt)).ExecuteAsync(token);
			var code = ServerBackup.CodeMigration();
			var waiting = RestoreMarker.Read(backups.Root);
			var last = await DB.Default.Find<RestoreRecord>().Sort(r => r.RestoredAt, Order.Descending).ExecuteFirstAsync(token);
			ServerBackup.MakeDirectory(backups.Root);
			return Ok(new ViewBackups
			{
				Backups = [.. backups.List().Select(b => View(b, deleted.Count(u => u.DeletedAt > b.CreatedAt), code))],
				Running = (await MaintenanceLock.Current(token))?.What,
				Waiting = waiting == default ? default : new ViewRestoreWaiting
				{
					Backup = waiting.Backup,
					State = waiting.State,
					Attempts = waiting.Attempts,
					RequestedBy = waiting.RequestedBy,
					RequestedAt = waiting.RequestedAt,
					Error = waiting.Error
				},
				LastRestore = last == default ? default : View(last),
				Host = HostName,
				FreeBytes = new DriveInfo(backups.Root).AvailableFreeSpace
			});
		}

		// a backup made now, while the page polls the list
		[HttpPost, Route("")]
		public async Task<IActionResult> Create(CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			if (await MaintenanceLock.Current(token) is { } held)
				return Conflict(new WebResult().Invalidate(localizer["A {0} is running.", held.What]));
			_ = Task.Run(async () =>
			{
				try
				{
					var (made, error) = await backups.Create("manual", dbOnly: false, CancellationToken.None);
					if (made == default)
						logger.LogWarning("The backup {Admin} asked for was not made: {Error}", admin.UserName, error);
					else
						logger.LogInformation("Backup {Id} made for {Admin}", made.Id, admin.UserName);
				}
				catch (Exception ex)
				{
					logger.LogError(ex, "The backup {Admin} asked for failed", admin.UserName);
				}
			}, CancellationToken.None);
			return Accepted();
		}

		[HttpDelete, Route("{id}")]
		public async Task<IActionResult> Delete(string id, CancellationToken token)
		{
			if (await Administrator(token) == default)
				return Forbid();
			if (RestoreMarker.Read(backups.Root) is { } waiting && (waiting.Backup == id || waiting.PreRestore == id))
				return Conflict(new WebResult().Invalidate(localizer["A restore waits for this backup."]));
			return backups.Delete(id) ? Ok() : NotFound();
		}

		// a link to download it with, for the password
		[HttpPost, Route("{id}/ticket")]
		public async Task<IActionResult> Ticket(string id, BackupPasswordForm form, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			if (!PasswordHolds(admin, form.Password))
				return UnprocessableEntity(new WebResult().Invalidate(localizer["Wrong password."]));
			if (backups.Find(id) == default)
				return NotFound();
			var (ticket, expires) = transfers.Ticket(id);
			return Ok(new ViewBackupTicket { Url = $"/clientapi/admin/backups/download/{ticket}", ExpiresAt = expires, Bytes = BackupTar.Of(backups.Root, id).Length });
		}

		// the backup as one tar, for a ticket: a plain link, so the browser downloads it to disk and resumes it
		[HttpGet, Route("download/{ticket}"), AllowAnonymous]
		public async Task Download(string ticket, CancellationToken token)
		{
			var id = transfers.Redeem(ticket);
			if (id == default || backups.Find(id) == default)
			{
				Response.StatusCode = StatusCodes.Status404NotFound;
				return;
			}
			HttpContext.Features.Get<IHttpResponseBodyFeature>()?.DisableBuffering();
			var tar = BackupTar.Of(backups.Root, id);
			var (from, to) = (0L, tar.Length - 1);
			Response.Headers.AcceptRanges = "bytes";
			Response.Headers.CacheControl = "no-store";
			Response.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = $"privapub-{id}.tar" }.ToString();
			var range = Request.GetTypedHeaders().Range;
			if (range is { Unit.Value: "bytes", Ranges.Count: 1 })
			{
				var asked = range.Ranges.First();
				var start = asked.From ?? tar.Length - asked.To.GetValueOrDefault();
				var end = asked.From.HasValue ? Math.Min(asked.To ?? tar.Length - 1, tar.Length - 1) : tar.Length - 1;
				if (start < 0 || start > end)
				{
					Response.StatusCode = StatusCodes.Status416RangeNotSatisfiable;
					Response.Headers.ContentRange = $"bytes */{tar.Length}";
					return;
				}
				(from, to) = (start, end);
				Response.StatusCode = StatusCodes.Status206PartialContent;
				Response.Headers.ContentRange = $"bytes {from}-{to}/{tar.Length}";
			}
			Response.ContentType = "application/x-tar";
			Response.ContentLength = to - from + 1;
			await tar.Write(Response.Body, from, to, token);
		}

		[HttpPost, Route("uploads")]
		public async Task<IActionResult> StartUpload(CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			return Ok(new ViewBackupUpload { Id = transfers.Start(admin.UserName), ChunkBytes = TransferStore.ChunkBytes });
		}

		[HttpGet, Route("uploads/{id}")]
		public async Task<IActionResult> Upload(string id, CancellationToken token)
		{
			if (await Administrator(token) == default)
				return Forbid();
			var received = transfers.Received(id);
			return received < 0 ? NotFound() : Ok(new ViewBackupUpload { Id = id, Received = received, ChunkBytes = TransferStore.ChunkBytes });
		}

		// a piece, at the offset already received: 409 with what was received when it isn't
		[HttpPut, Route("uploads/{id}"), RequestSizeLimit(TransferStore.ChunkBytes + 1024 * 1024)]
		public async Task<IActionResult> Append(string id, [FromQuery] long offset, CancellationToken token)
		{
			if (await Administrator(token) == default)
				return Forbid();
			var (received, taken) = await transfers.Append(id, offset, Request.Body, token);
			if (received < 0)
				return NotFound();
			var view = new ViewBackupUpload { Id = id, Received = received, ChunkBytes = TransferStore.ChunkBytes };
			return taken ? Ok(view) : Conflict(view);
		}

		[HttpPost, Route("uploads/{id}/finish")]
		public async Task<IActionResult> FinishUpload(string id, CancellationToken token)
		{
			if (await Administrator(token) == default)
				return Forbid();
			if (await MaintenanceLock.Current(token) is { What: "restore" })
				return Conflict(new WebResult().Invalidate(localizer["A {0} is running.", "restore"]));
			var (backup, error) = await transfers.Finish(id, token);
			if (backup == default)
				return UnprocessableEntity(new WebResult().Invalidate(error));
			return Ok(View(backup, 0, ServerBackup.CodeMigration()));
		}

		[HttpDelete, Route("uploads/{id}")]
		public async Task<IActionResult> CancelUpload(string id, CancellationToken token)
		{
			if (await Administrator(token) == default)
				return Forbid();
			return transfers.Cancel(id) ? Ok() : NotFound();
		}

		// asked for with the password and the host typed out: the service stops within seconds and restores it as it starts
		[HttpPost, Route("{id}/restore")]
		public async Task<IActionResult> Restore(string id, RestoreBackupForm form, CancellationToken token)
		{
			var admin = await Administrator(token);
			if (admin == default)
				return Forbid();
			if (!PasswordHolds(admin, form.Password))
				return UnprocessableEntity(new WebResult().Invalidate(localizer["Wrong password."]));
			if (!string.Equals(form.Host?.Trim(), HostName, StringComparison.OrdinalIgnoreCase))
				return UnprocessableEntity(new WebResult().Invalidate(localizer["Type this server's host to restore it."]));
			var refused = await ServerRestore.Request(backups.Context(), id, admin.UserName, token);
			if (refused != default)
				return UnprocessableEntity(new WebResult().Invalidate(refused));
			logger.LogWarning("{Admin} asked to restore {Backup}", admin.UserName, id);
			return Accepted();
		}

		string HostName => Uri.TryCreate(backups.Host, UriKind.Absolute, out var host) ? host.Authority : backups.Host;

		// 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;
		}

		bool PasswordHolds(RootUser root, string password) =>
			!string.IsNullOrEmpty(password) && !string.IsNullOrEmpty(root.HashedPassword) && hasher.Check(root.HashedPassword, password).verified;

		static ViewBackup View(BackupInfo backup, int rootsDeletedSince, int code)
		{
			var manifest = backup.Manifest;
			return new ViewBackup
			{
				Id = backup.Id,
				Kind = backup.Kind,
				CreatedAt = backup.CreatedAt,
				Bytes = backup.Bytes,
				MediaBytes = manifest.Media.Bytes,
				MediaFiles = manifest.DbOnly ? manifest.Media.List.Count : manifest.Media.Files,
				MediaMissing = manifest.Media.Missing,
				DbOnly = manifest.DbOnly,
				Consistent = manifest.Consistent,
				Collections = manifest.Collections.Count,
				Documents = manifest.Collections.Sum(c => c.Count),
				AppCommit = manifest.AppCommit,
				MigrationNumber = manifest.MigrationNumber,
				RootsDeletedSince = rootsDeletedSince,
				NotRestorable = manifest.Format != ArchiveManifest.CurrentFormat ? "format"
					: manifest.MigrationNumber > code ? "newer"
					: default
			};
		}

		static ViewRestore View(RestoreRecord record) => new()
		{
			Backup = record.Backup,
			BackupCreatedAt = record.BackupCreatedAt,
			PreRestore = record.PreRestore,
			RequestedBy = record.RequestedBy,
			RestoredAt = record.RestoredAt,
			Abandoned = record.Abandoned,
			Error = record.Error,
			Documents = record.Report.Documents,
			Collections = record.Report.Collections,
			MediaRestored = record.Report.MediaRestored,
			MediaMissing = record.Report.MediaMissing,
			RootsDeleted = record.Report.RootsDeleted,
			PersonasDeleted = record.Report.PersonasDeleted,
			GroupsDeleted = record.Report.GroupsDeleted,
			PostsDeleted = record.Report.PostsDeleted,
			RootsTombstoned = record.Report.RootsTombstoned,
			PersonasTombstoned = record.Report.PersonasTombstoned,
			GroupsTombstoned = record.Report.GroupsTombstoned,
			PostsGone = record.Report.PostsGone,
			MediaTrashed = record.Report.MediaTrashed,
			ProtectiveKept = record.Report.ProtectiveKept,
			SessionsEnded = record.Report.SessionsEnded
		};
	}
}