using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using Microsoft.VisualStudio.TextManager.Interop;

using Nemerle.Completion2;

using Nemerle.Compiler;

using Microsoft.VisualStudio;



namespace Nemerle.VisualStudio.LanguageService

{

	/// <summary>

	/// Helper class which match paired token (brackets, brace, etc.)

	/// </summary>

	class BracketFinder

	{

		#region Fields



		public readonly ScanTokenInfo StartBraceInfo;

		private readonly IVsTextColorState ColorState;

		private readonly NemerleSource Source;

		private readonly int StartLine;

		private readonly ScanLexer Lex;

		private readonly NemerleScanner Scanner;



		#endregion



		public BracketFinder(NemerleSource source, int startLine,

			int startCol, NemerleScanner scanner, IVsTextColorState colorState)

		{

			#region Init fields



			Scanner = scanner;

			Source = source;

			StartLine = startLine;

			Lex = scanner.GetNewLexer();

			Lex.SetFileName(source.GetFilePath());

			ColorState = colorState;

			_lineCount = source.GetLineCount();

			var line = startLine - 1;

			_buffer = new string[1] { source.GetText(line, 0, line, source.GetLineLength(line)) };

			_startBufferLine = line;



			#endregion



			#region 2. Determine that it is a paired token. 3. Determine paired token.



			// Get tokens of line under text carret into dynamic array.

			List<ScanTokenInfo> lineToks = GetLineTokens(startLine, true);

			// Find index of token which located under text carret.

			int index = FindIndex(lineToks, x => x.Token.Location.Contains(startLine, startCol));



			if (index < 0)

				return;



			// If index is corret get corresponding token.

			ScanTokenInfo startBraceInfo = lineToks[index];

			// Remember it, if token have paired token.

			if (IsPairedToken(startBraceInfo.Token))

				StartBraceInfo = startBraceInfo;

			else

			{

				// otherwise try get right-hand token...

				startBraceInfo = RightHand(lineToks, index);

				// Remember it, if token have paired token.

				if (IsPairedToken(startBraceInfo.Token))

					StartBraceInfo = startBraceInfo;

			}



			#endregion

		}



		public ScanTokenInfo FindMatchBraceInfo()

		{

			if (StartBraceInfo == null)

				return null;



			// 4. Find paired token in the source file.



			Token tok = StartBraceInfo.Token;

			Predicate<Token> isStartBrace = GetMatchBracePredicate(tok);

			Predicate<Token> isEndBrace = GetMatchBracePredicate(GetPairedToken(tok));

			int nestedLevel = 1;



			foreach (ScanTokenInfo tokInfo in GetTokenIter())

			{

				if (isEndBrace(tokInfo.Token))

					nestedLevel--;

				else if (isStartBrace(tokInfo.Token))

					nestedLevel++;

				if (nestedLevel == 0)

					return tokInfo; // Match found!

			}



			return null; // Match not found.

		}



		#region GetTokenIter()



		/// <summary>

		/// Return iterator which allow iterate throw tokens of curent 

		/// source file. Iteration process start from token behind current 

		/// token and go forward or backward depending on type of start token.

		/// If start token is open token (for example, "(" or "{") iteration

		/// execute forward. If start token is close token (for example, ")" 

		/// or "]") iteration execute backward.

		/// </summary>

		private IEnumerable<ScanTokenInfo> GetTokenIter()

		{

			bool isScanForward = IsOpenToken(StartBraceInfo.Token);

			int startLine = StartLine;

			// 1. Для первой строки находим токен и начиная от него сканируем вперед или назад.

			List<ScanTokenInfo> tokInfs = new List<ScanTokenInfo>(

				GetLineTokens(startLine, isScanForward));



			int tokIndex = FindIndex(tokInfs, delegate(ScanTokenInfo ti)

			{ return ti.Token.Location == StartBraceInfo.Token.Location; });

			if (tokIndex < 0)

				throw new Exception("tokInfs.IndexOf(startBraceInfo)");



			// Scan first line from "start bracket" index.

			for (int i = tokIndex + 1; i < tokInfs.Count; i++)

				yield return tokInfs[i];



			if (isScanForward) // Scan next lines.

				for (int i = startLine + 1, count = _lineCount; i <= count; i++)

					foreach (ScanTokenInfo tokInf in GetLineTokens(i, true))

						yield return tokInf;

			else // Scan previous lines.

				for (int i = startLine - 1; i > 0; i--)

					foreach (ScanTokenInfo tokInf in GetLineTokens(i, false))

						yield return tokInf;

		}



		#endregion



		#region GetLineTokens()



		const int BufferLen = 100;

		string[] _buffer;

		int _startBufferLine;

		int _lineCount;



		/// <summary>

		/// Get tokens of specified line.

		/// </summary>

		/// <param name="line">Line number which tokens it is necessary retrieve</param>

		/// <param name="isForward">Direction of iteration (true is forward)</param>

		/// <returns>Token list</returns>

		List<ScanTokenInfo> GetLineTokens(int nline, bool isForward)

		{

			int line = nline - 1;

			ScanState scanState = GetLineState(nline);

			string lineText;



			int index = line - _startBufferLine;



			// читаем буферами по BufferLen стрк, чтобы ускорить работу

			if (index < 0 || index >= _buffer.Length)

			{

				int start, end;



				if (isForward)

				{

					end = Math.Min(_lineCount - 1, line + BufferLen);

					start = line;

				}

				else

				{

					start = Math.Max(0, line - BufferLen);

					end = line;

				}



				var str = Source.GetText(start, 0, end, Source.GetLineLength(end));

				_buffer = str.Split(new string[] { "\r\n", "\n", "\r" }, StringSplitOptions.None);

				_startBufferLine = start;

				index = line - _startBufferLine;

			}

				

			lineText = _buffer[index];



			Scanner.SetSource(lineText, 0);

			Lex.SetLine(nline, lineText, 0, null, null);

			List<ScanTokenInfo> lst = new List<ScanTokenInfo>();



			foreach (ScanTokenInfo var in GetLineTokens(Lex, scanState))

				lst.Add(var);



			if (!isForward)

				lst.Reverse();



			return lst;

		}



		/// <summary>Return colorer lexer state for specified line.</summary>

		private ScanState GetLineState(int line)

		{

			int state;

			ErrorHandler.ThrowOnFailure(

				ColorState.GetColorStateAtStartOfLine(line, out state));

			return (ScanState)state;

		}



		/// <summary>

		/// Implementation of<c>GetLineTokens</c>(). Don't use this method directly!

		/// </summary>

		IEnumerable<ScanTokenInfo> GetLineTokens(ScanLexer lex, ScanState scanState)

		{

			ScanTokenInfo info = lex.GetToken(scanState);

			scanState = info.State;

			while (!info.IsEndOfLine)

			{

				yield return info;

				info = lex.GetToken(scanState);

				scanState = info.State;

			}

		}



		#endregion



		#region Paired token identification functions



		public static bool IsOpenToken(Token token)

		{

			if (token is Token.BeginBrace) return true;

			if (token is Token.BeginQuote) return true;

			if (token is Token.BeginRound) return true;

			if (token is Token.BeginSquare) return true;



			if (token is Token.EndBrace) return false;

			if (token is Token.EndQuote) return false;

			if (token is Token.EndRound) return false;

			if (token is Token.EndSquare) return false;



			Token.Keyword kwd = token as Token.Keyword;



			if (kwd != null)

			{

				if (kwd.name == "if") return true;

				if (kwd.name == "else") return false;

			}



			throw new ArgumentException(string.Format("The token '{0}' not a brace!", token), "token");

		}



		private static bool IsPairedToken(Token token)

		{

			if (token is Token.BeginBrace || token is Token.BeginQuote

				|| token is Token.BeginRound || token is Token.BeginSquare

				|| token is Token.EndBrace || token is Token.EndQuote

				|| token is Token.EndRound || token is Token.EndSquare

			)

				return true;



			var kwd = token as Token.Keyword;



			if (kwd != null && (kwd.name == "if" || kwd.name == "else"))

				return true;



			return false;

		}



		/// <summary>

		/// Return predicate function which check it argument is same token .

		/// </summary>

		private static Predicate<Token> GetMatchBracePredicate(Token token)

		{

			if (token is Token.BeginBrace) return t => t is Token.BeginBrace;

			if (token is Token.BeginQuote) return t => t is Token.BeginQuote;

			if (token is Token.BeginRound) return t => t is Token.BeginRound;

			if (token is Token.BeginSquare) return t => t is Token.BeginSquare;



			if (token is Token.EndBrace) return t => t is Token.EndBrace;

			if (token is Token.EndQuote) return t => t is Token.EndQuote;

			if (token is Token.EndRound) return t => t is Token.EndRound;

			if (token is Token.EndSquare) return t => t is Token.EndSquare;



			Token.Keyword kwd = token as Token.Keyword;



			if (kwd != null)

			{

				if (kwd.name == "if")

					return delegate(Token t)

					{

						Token.Keyword kwd1 = t as Token.Keyword;



						return kwd1 != null && kwd1.name == "if";

					};

				if (kwd.name == "else")

					return delegate(Token t)

					{

						Token.Keyword kwd1 = t as Token.Keyword;

						return kwd1 != null && kwd1.name == "else";

					};

			}



			return null;

		}



		private static Token GetPairedToken(Token token)

		{

			if (token is Token.BeginBrace) return new Token.EndBrace(true);

			if (token is Token.BeginQuote) return new Token.EndQuote();

			if (token is Token.BeginRound) return new Token.EndRound();

			if (token is Token.BeginSquare) return new Token.EndSquare();



			if (token is Token.EndBrace) return new Token.BeginBrace(true);

			if (token is Token.EndQuote) return new Token.BeginQuote();

			if (token is Token.EndRound) return new Token.BeginRound();

			if (token is Token.EndSquare) return new Token.BeginSquare();



			Token.Keyword kwd = token as Token.Keyword;



			if (kwd != null)

			{

				if (kwd.name == "if") return new Token.Keyword("else");

				if (kwd.name == "else") return new Token.Keyword("if");

			}



			return null;

		}



		#endregion



		#region Utils



		static T RightHand<T>(IList<T> lst, int index) where T : new()

		{

			int nextIndex = index + 1;

			if (nextIndex >= lst.Count)

				return new T();



			return lst[nextIndex];

		}



		static int FindIndex<T>(IList<T> lst, Predicate<T> predicate) where T : class

		{

			for (int i = 0; i < lst.Count; i++)

				if (predicate(lst[i]))

					return i;



			return -1;

		}



		#endregion

	}

}