using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Text;
using SBRL.Utilities;

namespace LibSearchBox
{
	[Flags]
	public enum IndexOptions
	{
		ExcludeStopwords = 1
	}

	public class Index : IEnumerable<KeyValuePair<string, List<int>>>
	{
		private Dictionary<string, List<int>> index = new Dictionary<string, List<int>>();
		private StopwordTester stopwordTester;

		public Index(string inSource, IEnumerable<string> stopwords, IndexOptions options)
		{
			if (options.HasFlag(IndexOptions.ExcludeStopwords))
				stopwordTester = new StopwordTester(stopwords);
			
			// Tokenize the input and file it in our index
			Tokenizer tokenizer = new Tokenizer(inSource);
			foreach ((int, string) token in tokenizer) {
				if (stopwordTester.IsStopword(token.Item2)) continue;
				insert(token.Item2, token.Item1);
			}

		}

		public Index(string inSource, IndexOptions options)
			: this(inSource, EmbeddedFiles.EnumerateLines("LibSearchBox.EmbeddedFiles.Stopwords.txt"), options)
		{
		}
		public Index(string inSource) : this(inSource, IndexOptions.ExcludeStopwords)
		{
		}

		public List<int> this[string key] {
			get {
				return index[key];
			}
		}


		protected void insert(string token, int offset)
		{
			if (!index.ContainsKey(token))
				index.Add(token, new List<int>());
			index[token].Add(offset);
		}



		public IEnumerable<string> Tokens()
		{
			return index.Keys;
		}
		public IEnumerable<KeyValuePair<string, List<int>>> IterateItems()
		{
			foreach(KeyValuePair<string, List<int>> item in index)
				yield return item;
		}

		public IEnumerator<KeyValuePair<string, List<int>>> GetEnumerator()
		{
			return IterateItems().GetEnumerator();
		}
		IEnumerator IEnumerable.GetEnumerator()
		{
			return GetEnumerator();
		}

		public override string ToString()
		{
			StringBuilder result = new StringBuilder("Index: \n");
			foreach (KeyValuePair<string, List<int>> item in index)
				result.AppendLine($"\t{item.Key}: {string.Join(", ", item.Value)}");
			return result.ToString();
		}

		// --------------------------------------------------------------------------------------

		public static Index FromFile(string filename)
		{
			return new Index(File.ReadAllText(filename));
		}

	}
}