using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Sony.Filtr.PersistentCaching;

namespace Sony.Filtr.PlaylistGeneration.Autocomplete
{
    public class RedisAutocompleteFactory : IAutocompleteFactory
    {
        private const string autocompleteRedisKey = "Artist-Autocomplete";
        private const char fullWordMarker = '*';

        private readonly string _index;
        public RedisAutocompleteFactory(string index = null)
        {
            _index = index ?? string.Empty;
        }

        private string GetArtistAutocompleteKey()
        {
            return _index + autocompleteRedisKey;
        }

        private string GetArtistIndexedKey()
        {
            return _index + "IndexedArtists";
        }

        public IEnumerable<string> SearchArtists(string search, int count)
        {
            search = search.ToLower();

            var startTask = PersistentCachingManager.Instance.Connection.SortedSets.Rank(0, GetArtistAutocompleteKey(), search);
            try
            {
                if (startTask.Result == 0)
                    return new string[] { };
            }
            catch (Exception ex)
            {
                //We need to have this try-catch because of a bug in booksleeve that doesn't handle non-existing keys in SortedSets.

                //MusicMatch.ErrorLogging.ErrorLoggingManager.Instance.LogError(ex);
                return new string[] { };
            }

            var start = startTask.Result;
            if (!start.HasValue)
                return new string[] { };

            List<string> results = new List<string>();
            var rangeLength = 50;
            while (results.Count < count)
            {
                long endIndex = start.Value + rangeLength - 1;
                var range = PersistentCachingManager.Instance.Connection.SortedSets.Range(0, GetArtistAutocompleteKey(), start.Value, endIndex);
                start += rangeLength;
                if (range.Result == null || !range.Result.Any())
                    break;
                foreach (var item in range.Result)
                {
                    var itemKey = Encoding.UTF8.GetString(item.Key);
                    var minLength = Math.Min(itemKey.Length, search.Length);
                    if (itemKey.Substring(0, minLength) != search.Substring(0, minLength))
                        count = results.Count;

                    if (itemKey.EndsWith(fullWordMarker.ToString()) && results.Count != count)
                        results.Add(itemKey.Substring(0, itemKey.Length - 1));
                }
            }
            return results.OrderBy(r => r);
        }

        public void IndexArtistAsync(string artistName)
        {
            if (HasIndexed(artistName))
                return;

            artistName = artistName.ToLower();

            IndexAsync(artistName);
            var withoutPrefix = StripCommonPrefix(artistName);
            if (withoutPrefix != artistName)
                IndexAsync(withoutPrefix);

            SetAsIndexed(artistName);
        }

        private string[] GetIndexedArtists()
        {
            return PersistentCachingManager.Instance.Connection.Sets.GetAllString(0, GetArtistIndexedKey()).Result;
        }

        private void SetAsIndexed(string artistName)
        {
            PersistentCachingManager.Instance.Connection.Sets.Add(0, GetArtistIndexedKey(), artistName);
        }

        public bool HasIndexed(string artistName)
        {
            return PersistentCachingManager.Instance.Connection.Sets.Contains(0, GetArtistIndexedKey(), artistName.ToLower()).Result;
        }

        private void IndexAsync(string value)
        {
            value = value.ToLower();
            for (int i = 0; i < value.Length; i++)
            {
                PersistentCachingManager.Instance.Connection.SortedSets.Add(0, GetArtistAutocompleteKey(), value.Substring(0, value.Length - i), 0);
            }

            PersistentCachingManager.Instance.Connection.SortedSets.Add(0, GetArtistAutocompleteKey(), value + fullWordMarker, 0);
        }

        private string StripCommonPrefix(string value)
        {
            if (value.StartsWith("the ", StringComparison.InvariantCultureIgnoreCase))
                value = value.Substring(4);
            else if (value.StartsWith("a ", StringComparison.InvariantCultureIgnoreCase))
                value = value.Substring(2);
            return value;
        }
    }
}