using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace LibSearchBox
{
	public class SearchBoxException : Exception { public SearchBoxException(string message) : base(message) {  } }

	[JsonObject(MemberSerialization.OptIn)]
	public class SearchBox
	{
		private IdMap idMap = new IdMap();

		[JsonProperty("ids")]
		public Dictionary<int, string> IdMap {
			get {
				Dictionary<int, string> result = idMap.MapOut;
				if (result.Count == 0) return null;
				return result;
			}
			set {
				if (value == null) return;
				idMap.Import(value);
			}
		}

		[JsonProperty]
		public ConcurrentDictionary<int, DocumentMeta> metaTable = new ConcurrentDictionary<int, DocumentMeta>();
		[JsonProperty]
		public InvertedIndex index = new InvertedIndex();

		public bool Verbose { get; set; } = false;

		public SearchBox()
		{

		}

		#region Index Management

		public void AddDocument(string title, IEnumerable<string> tags, string content)
		{
			DocumentMeta info = new DocumentMeta(title, tags);
			int id = idMap.GetId(info.Title);
			metaTable.AddOrUpdate(id, info, (key, oldValue) => info);
			Index upsideIndex = new Index(content);
			index.AddIndex(id, upsideIndex);
		}

		public void UpdateDocument(string title, IEnumerable<string> newTags, string oldContent, string newContent)
		{
			int id = idMap.GetId(title);
			DocumentMeta info = metaTable[id];
			info.ReplaceTags(newTags);

			Index oldIndex = new Index(oldContent), newIndex = new Index(newContent);
			if (!index.ReplaceIndex(id, oldIndex, newIndex))
				throw new SearchBoxException($"Error: Failed to replace index for document with title {title}.");
		}

		public void RemoveDocument(string title)
		{
			int id = idMap.DeletePageName(title);
			metaTable.TryRemove(id, out DocumentMeta noop);
			if (!index.RemoveById(id))
				throw new SearchBoxException($"Failed to remove page with title '{title}' from inverted index.");

		}

		#endregion

		#region Query

		public List<SearchResult> Query(string query, QuerySettings settings)
		{
			// pageId => token -> count
			ConcurrentDictionary<int, ConcurrentDictionary<string, int>> matchingPages = new ConcurrentDictionary<int, ConcurrentDictionary<string, int>>();

			Tokenizer tokenizer = new Tokenizer(query);
			foreach(Tuple<int, string> token in tokenizer.IterateTokens())
			{
				ConcurrentDictionary<int, List<int>> tokenResults = index.Query(token.Item2);

				Parallel.ForEach(tokenResults, (KeyValuePair<int, List<int>> pageTokenDef) => {
					// pageTokenDef: pageId => List of token offsets
					ConcurrentDictionary<string, int> pageData = matchingPages.GetOrAdd(pageTokenDef.Key, new ConcurrentDictionary<string, int>());
					if (!pageData.TryAdd(token.Item2, pageTokenDef.Value.Count))
						throw new SearchBoxException("Error: Failed to add token count to page data in search " +
						    "results - the key already exists (are there duplicate tokens for this page id " +
						    "in the inverted index?");
				});
			}

			ConcurrentBag<SearchResult> resultsRaw = new ConcurrentBag<SearchResult>();
			Parallel.ForEach(matchingPages, (KeyValuePair<int, ConcurrentDictionary<string, int>> pageDef) => {
				int rank = pageDef.Value.Values.Sum(); // FUTURE: Linq is slow. Is theree a faster way of doing this?
				if (!metaTable.TryGetValue(pageDef.Key, out DocumentMeta metaInfo)) {
					if (Verbose) Console.Error.WriteLine($"Warning: Failed to fetch meta info for page id {pageDef.Key}");
				}
				else {
					foreach (Tuple<int, string> token in tokenizer.IterateTokens()) {
						if (metaInfo.SearchableTitle.Contains(token.Item2))
							rank += settings.WeightTitleMatch; // FUTURE: Alter the amount added by the length of the word matched

						foreach (string nextTag in metaInfo.SearchableTags)
							if (nextTag.Contains(token.Item2))
								rank += settings.WeightTagMatch;
					}
				}

				List<SearchOffset> offsets = new List<SearchOffset>();
				foreach (Tuple<int, string> token in tokenizer.IterateTokens())
					offsets.AddRange(index.Query(token.Item2)[pageDef.Key].Select((int offset) => new SearchOffset(token.Item2, offset)));
				offsets.Sort((SearchOffset x, SearchOffset y) => x.Offset - y.Offset);

				resultsRaw.Add(new SearchResult(
					idMap.GetPageName(pageDef.Key),
					rank,
					offsets
				));
			});

			List<SearchResult> results = new List<SearchResult>(resultsRaw.AsEnumerable());
			results.OrderBy((SearchResult result) => result.Rank);
			return results;
		}

		#endregion
	}
}