using PrivaPub.Api.Mastodon.Entities;
using PrivaPub.Federation.Actors;
using PrivaPub.StaticServices;

namespace PrivaPub.Api.Mastodon.Mappers
{
	public class AccountSearch
	{
		readonly MastodonMapper _mapper;
		readonly DbEntities _dbEntities;
		readonly ILocalActorService _localActors;
		readonly IRemoteActorService _remoteActors;

		public AccountSearch(MastodonMapper mapper, DbEntities dbEntities, ILocalActorService localActors, IRemoteActorService remoteActors)
		{
			_mapper = mapper;
			_dbEntities = dbEntities;
			_localActors = localActors;
			_remoteActors = remoteActors;
		}

		public async Task<List<Account>> Find(string q, bool resolve, int limit, CancellationToken token) => await Find(q, resolve, limit, 0, token);

		// following=true: only accounts the persona follows, matched by the start of their name, display name or server
		// (what a client offers when adding to a list), read from what PrivaPub holds and never resolved
		public async Task<List<Account>> Followed(string viewerId, string q, int limit, CancellationToken token)
		{
			q = q?.Trim().TrimStart('@') ?? string.Empty;
			var ids = (await _dbEntities.Followings.Match(f => f.AvatarId == viewerId && f.State == Models.Social.FollowState.Accepted).ExecuteAsync(token))
				.Select(f => f.TargetAccountId).Where(id => !string.IsNullOrEmpty(id)).ToList();
			if (ids.Count == 0)
				return new List<Account>();
			var parts = q.Split('@');
			var localDomain = new Uri(_localActors.BaseAddress).Authority;
			bool Matches(string userName, string name, string domain) =>
				userName?.StartsWith(parts[0], StringComparison.OrdinalIgnoreCase) == true
					&& (parts.Length < 2 || domain?.StartsWith(parts[1], StringComparison.OrdinalIgnoreCase) == true)
				|| parts.Length == 1 && name?.Contains(q, StringComparison.OrdinalIgnoreCase) == true;
			var found = (await _dbEntities.Avatars.Match(a => ids.Contains(a.ID) && !a.DeletionAt.HasValue).ExecuteAsync(token))
				.Where(a => Matches(a.UserName, a.Name, localDomain)).Select(a => (a.UserName, a.ID))
				.Concat((await _dbEntities.ForeignAvatars.Match(f => ids.Contains(f.ID) && !f.DeletionAt.HasValue).ExecuteAsync(token))
					.Where(f => Matches(f.UserName, f.Name, f.Domain)).Select(f => (f.UserName, f.ID)))
				.OrderBy(a => a.UserName, StringComparer.OrdinalIgnoreCase).Take(limit).Select(a => a.ID).ToList();
			var accounts = await _mapper.Accounts(found, token);
			return found.Where(accounts.ContainsKey).Select(id => accounts[id]).ToList();
		}

		// gone accounts (remote ones that deleted themselves, personas of banned or deleted roots) are never found
		public async Task<List<Account>> Find(string q, bool resolve, int limit, int offset, CancellationToken token)
		{
			q = q?.Trim().TrimStart('@');
			if (string.IsNullOrEmpty(q))
				return new List<Account>();
			var results = new List<Account>();
			var parts = q.Split('@');
			var localDomain = new Uri(_localActors.BaseAddress).Authority;
			if (parts.Length == 2 && !parts[1].Equals(localDomain, StringComparison.OrdinalIgnoreCase) && !string.IsNullOrEmpty(parts[0]))
			{
				var userName = parts[0];
				var domain = parts[1].ToLowerInvariant();
				var known = await _dbEntities.ForeignAvatars.Match(f => f.UserName == userName && f.Domain == domain && !f.DeletionAt.HasValue).ExecuteFirstAsync(token);
				if (known == default && resolve)
				{
					var actorUri = await _remoteActors.ResolveHandle(q, token);
					known = actorUri == default ? default : await _remoteActors.GetActor(actorUri, refresh: false, token);
				}
				if (known is { DeletionAt: null } && offset == 0)
					results.Add(_mapper.Foreign(known));
				return results;
			}

			var prefix = parts[0].ToLowerInvariant();
			var barred = await Domain.Privacy.Counted.BarredPersonas(token);
			var locals = await _dbEntities.Avatars
				.Match(a => a.UserName.StartsWith(prefix) && !a.DeletionAt.HasValue && a.Settings.IsDiscoverable != false && !barred.Contains(a.ID))
				.Sort(a => a.UserName, MongoDB.Entities.Order.Ascending)
				.Limit(offset + limit).ExecuteAsync(token);
			foreach (var avatar in locals.Skip(offset))
				results.Add(await _mapper.Local(_localActors.FromAvatar(avatar), false, token));
			var skipRemote = Math.Max(0, offset - locals.Count);
			if (results.Count < limit)
				foreach (var foreign in await _dbEntities.ForeignAvatars.Match(f => f.UserName.StartsWith(parts[0]) && f.IsDiscoverable && !f.DeletionAt.HasValue)
					.Sort(f => f.UserName, MongoDB.Entities.Order.Ascending)
					.Skip(skipRemote).Limit(limit - results.Count).ExecuteAsync(token))
					results.Add(_mapper.Foreign(foreign));
			return results;
		}
	}
}