using System.Collections.Generic;
using System.Linq;
using Lucene.Net.Analysis;
using Lucene.Net.Analysis.Standard;
using Lucene.Net.Documents;
using Lucene.Net.Index;
using Lucene.Net.QueryParsers;
using Lucene.Net.Search;
using Portoa.Persistence;

namespace VideoGameQuotes.Api.Search.Lucene {
	/// <summary>
	/// <see cref="IQuoteSearcher"/> implementation based on <c>Lucene.NET</c>
	/// </summary>
	public class LuceneQuoteSearcher : IQuoteSearcher {
		private readonly ISearchIndexLocator indexLocator;
		private readonly IRepository<Quote> quoteRepository;
		private readonly Analyzer analyzer = new StandardAnalyzer();
		private readonly QueryParser queryParser;

		public LuceneQuoteSearcher(ISearchIndexLocator indexLocator, IRepository<Quote> quoteRepository) {
			this.indexLocator = indexLocator;
			this.quoteRepository = quoteRepository;
			queryParser = new QueryParser("text", analyzer);
		}

		[UnitOfWork]
		public IEnumerable<SearchResult> Search(string searchString) {
			if (string.IsNullOrWhiteSpace(searchString)) {
				return Enumerable.Empty<SearchResult>();
			}

			var query = queryParser.Parse(QueryParser.Escape(searchString));
			var searcher = new IndexSearcher(indexLocator.IndexDirectory);
			return searcher
				.Search(query)
				.ToEnumerable()
				.Select(hit => new SearchResult { 
					Score = hit.GetScore(), 
					Quote = quoteRepository.FindById(int.Parse(hit.GetDocument().GetField("id").StringValue())) 
				});
		}

		[UnitOfWork]
		public void BuildIndex(bool replaceOldIndex = true) {
			var indexWriter = new IndexWriter(indexLocator.IndexDirectory, analyzer, replaceOldIndex);
			foreach (var quote in quoteRepository.Records) {
				indexWriter.AddDocument(CreateDocument(quote));
			}

			indexWriter.Optimize();
			indexWriter.Close();
		}

		private static Document CreateDocument(Quote quote) {
			var document = new Document();
			document.Add(new Field("id", quote.Id.ToString(), Field.Store.YES, Field.Index.NO));
			document.Add(new Field("text", quote.Text, Field.Store.YES, Field.Index.TOKENIZED));
			return document;
		}
	}
}