using System;
using System.Collections.Generic;
using System.Linq;
using Lucene.Net.QueryParsers;
using Lucene.Net.Search;
using Portoa.Persistence;
using VideoGameQuotes.Api.Persistence;
using Directory = Lucene.Net.Store.Directory;

namespace VideoGameQuotes.Api.Search.Lucene {
	/// <summary>
	/// <see cref="ISearcher{T}"/> implementation for entities based on <c>Lucene.NET</c>
	/// </summary>
	public class LuceneEntitySearcher<T> : ISearcher<T> where T : Entity<T, int> {
		private readonly QueryParser queryParser;
		private readonly Directory indexDirectory;
		private readonly ISearchService<T> searchService;

		public LuceneEntitySearcher(QueryParser queryParser, Directory indexDirectory, ISearchService<T> searchService) {
			this.queryParser = queryParser;
			this.indexDirectory = indexDirectory;
			this.searchService = searchService;
		}

		public IEnumerable<SearchResult<T>> Search(string searchString, int maxResults = 10) {
			if (string.IsNullOrWhiteSpace(searchString)) {
				return Enumerable.Empty<SearchResult<T>>();
			}
			if (maxResults < 0) {
				throw new ArgumentOutOfRangeException("maxResults", maxResults, "Maximum number of results must be greater than or equal to zero");
			}
			if (maxResults == 0) {
				maxResults = int.MaxValue;
			}

			var query = queryParser.Parse(QueryParser.Escape(searchString));
			var searcher = new IndexSearcher(indexDirectory, true);
			try {
				var docs = searcher
					.Search(query, maxResults)
					.scoreDocs;

				var quotes = searchService.FindByIds(docs.Select(doc => int.Parse(searcher.Doc(doc.doc).GetField("id").StringValue())));
				return quotes.Zip(docs, (entity, doc) => new SearchResult<T> { Entity = entity, Score = doc.score }).ToArray();
			} finally {
				searcher.Close();
			}
		}
	}
}