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

// SmarterSql (c) Johan Sassner 2008

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

using System;

using System.Collections.Generic;

using Sassner.SmarterSql.Objects;

using Sassner.SmarterSql.Parsing;

using Sassner.SmarterSql.ParsingObjects;

using Sassner.SmarterSql.ParsingUtils;

using Sassner.SmarterSql.Utils;



namespace Sassner.SmarterSql.Tree {

	public class InStatement {

		#region GetIfAnyNextValidToken



		/// <summary>

		/// Return true if the next token is of any kind from the suppled TokenInfo objects, else false

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="i"></param>

		/// <param name="nextToken"></param>

		/// <param name="kindToFind"></param>

		/// <returns></returns>

		public static bool GetIfAnyNextValidToken(List<TokenInfo> lstTokens, ref int i, out TokenInfo nextToken, params TokenKind[] kindToFind) {

			nextToken = null;

			int start = i;

			i++;

			for (int j = 0; j < kindToFind.Length; j++) {

				nextToken = GetNextNonCommentToken(lstTokens, ref i);

				if (null != nextToken && nextToken.Kind == kindToFind[j]) {

					return true;

				}

			}

			i = start;

			return false;

		}



		public static bool GetIfAnyNextValidToken(List<TokenInfo> lstTokens, ref int i, out TokenInfo nextToken, params TokenType[] typeToFind) {

			nextToken = null;

			int start = i;

			i++;

			for (int j = 0; j < typeToFind.Length; j++) {

				nextToken = GetNextNonCommentToken(lstTokens, ref i);

				if (null != nextToken && nextToken.Type == typeToFind[j]) {

					return true;

				}

			}

			i = start;

			return false;

		}



		#endregion



		#region GetIfAllNextValidToken



		/// <summary>

		/// Return true if all of the supplied TokenKinds are found after each others, else false

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="i"></param>

		/// <param name="nextToken"></param>

		/// <param name="kindToFind"></param>

		/// <returns></returns>

		public static bool GetIfAllNextValidToken(List<TokenInfo> lstTokens, ref int i, out TokenInfo nextToken, params TokenKind[] kindToFind) {

			nextToken = null;

			int start = i;

			for (int j = 0; j < kindToFind.Length; j++) {

				i++;

				nextToken = GetNextNonCommentToken(lstTokens, ref i);

				if (null == nextToken || nextToken.Kind != kindToFind[j]) {

					i = start;

					return false;

				}

			}

			return true;

		}



		public static bool GetIfAllNextValidToken(List<TokenInfo> lstTokens, ref int i, out TokenInfo nextToken, params TokenType[] typeToFind) {

			nextToken = null;

			int start = i;

			for (int j = 0; j < typeToFind.Length; j++) {

				i++;

				nextToken = GetNextNonCommentToken(lstTokens, ref i);

				if (null == nextToken || nextToken.Type != typeToFind[j]) {

					i = start;

					return false;

				}

			}

			return true;

		}



		#endregion



		#region GetNextNonCommentToken methods



		/// <summary>

		/// Get first next token not being a comment token

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="currentIndex"></param>

		/// <returns></returns>

		public static TokenInfo GetNextNonCommentToken(List<TokenInfo> lstTokens, ref int currentIndex) {

			TokenInfo token = null;

			if (currentIndex >= 0) {

				while (currentIndex <= lstTokens.Count - 1) {

					token = lstTokens[currentIndex];

					if (token.Type == TokenType.Comment) {

						if (currentIndex <= lstTokens.Count - 1) {

							currentIndex++;

						} else {

							return null;

						}

					} else {

						return token;

					}

				}

			}

			return token;

		}



		/// <summary>

		/// Get first next token not being a comment token

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="currentIndex"></param>

		/// <returns></returns>

		public static TokenInfo GetNextNonCommentToken(List<TokenInfo> lstTokens, int currentIndex) {

			TokenInfo token = null;

			if (currentIndex >= 0) {

				while (currentIndex <= lstTokens.Count - 1) {

					token = lstTokens[currentIndex];

					if (token.Type == TokenType.Comment) {

						if (currentIndex <= lstTokens.Count - 1) {

							currentIndex++;

						} else {

							return null;

						}

					} else {

						return token;

					}

				}

			}

			return token;

		}



		/// <summary>

		/// Get first next token not being a comment token

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="currentIndex"></param>

		/// <param name="defaultIndex"></param>

		/// <returns></returns>

		public static int GetNextNonCommentToken(List<TokenInfo> lstTokens, int currentIndex, int defaultIndex) {

			TokenInfo token;

			if (currentIndex >= 0) {

				while (currentIndex <= lstTokens.Count - 1) {

					token = lstTokens[currentIndex];

					if (token.Type == TokenType.Comment) {

						if (currentIndex <= lstTokens.Count - 1) {

							currentIndex++;

						} else {

							return defaultIndex;

						}

					} else {

						return currentIndex;

					}

				}

			}

			return currentIndex;

		}



		#endregion



		#region GetPreviousNonCommentToken methods



		/// <summary>

		/// Get first previous token that ain't a comment token

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="currentIndex"></param>

		/// <returns></returns>

		public static TokenInfo GetPreviousNonCommentToken(List<TokenInfo> lstTokens, ref int currentIndex) {

			TokenInfo token = null;

			if (currentIndex <= lstTokens.Count - 1) {

				while (currentIndex >= 0) {

					token = lstTokens[currentIndex];

					if (token.Type == TokenType.Comment) {

						if (currentIndex - 1 >= 0) {

							currentIndex--;

						} else {

							return null;

						}

					} else {

						return token;

					}

				}

			}

			return token;

		}



		/// <summary>

		/// Get first previous token that ain't a comment token

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="currentIndex"></param>

		/// <returns></returns>

		public static TokenInfo GetPreviousNonCommentToken(List<TokenInfo> lstTokens, int currentIndex) {

			TokenInfo token = null;

			if (currentIndex <= lstTokens.Count - 1) {

				while (currentIndex >= 0) {

					token = lstTokens[currentIndex];

					if (token.Type == TokenType.Comment) {

						if (currentIndex - 1 >= 0) {

							currentIndex--;

						} else {

							return null;

						}

					} else {

						return token;

					}

				}

			}

			return token;

		}



		/// <summary>

		/// Get first previous token that ain't a comment token

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="currentIndex"></param>

		/// <param name="defaultIndex"></param>

		/// <returns></returns>

		public static int GetPreviousNonCommentToken(List<TokenInfo> lstTokens, int currentIndex, int defaultIndex) {

			TokenInfo token;

			if (currentIndex <= lstTokens.Count - 1) {

				while (currentIndex >= 0) {

					token = lstTokens[currentIndex];

					if (token.Type == TokenType.Comment) {

						if (currentIndex - 1 >= 0) {

							currentIndex--;

						} else {

							return defaultIndex;

						}

					} else {

						return currentIndex;

					}

				}

			}

			return currentIndex;

		}



		#endregion



		public static bool IsDatabase(int currentIndex, List<TokenInfo> tokens, Server activeServer, out Connection foundConnection) {

			foundConnection = null;



			if (currentIndex >= 0) {

				string database = tokens[currentIndex].Token.UnqoutedImage;



				foreach (Connection connection in activeServer.Connections) {

					if (connection.ActiveConnection.DatabaseName.Equals(database, StringComparison.OrdinalIgnoreCase)) {

						foundConnection = connection;

						return true;

					}

				}



				if (Server.AddNewConnection(activeServer, database, out foundConnection)) {

					return true;

				}

			}



			return false;

		}



		/// <summary>

		/// Find out if the token at the current index is a schema

		/// </summary>

		/// <param name="currentIndex"></param>

		/// <param name="activeServer"></param>

		/// <param name="foundSchema"></param>

		/// <param name="foundConnection"></param>

		/// <param name="tokens"></param>

		/// <param name="activeConnection"></param>

		/// <returns></returns>

		public static bool IsSchema(int currentIndex, List<TokenInfo> tokens, Connection activeConnection, Server activeServer, out SysObjectSchema foundSchema, out Connection foundConnection) {

			if (currentIndex >= 0) {

				string database = activeConnection.ActiveConnection.DatabaseName;

				string schema = tokens[currentIndex].Token.UnqoutedImage;



				if (schema.Equals(".")) {

					schema = activeServer.GetDefaultSchema();

					if (currentIndex - 1 >= 0 && tokens[currentIndex - 1].Kind == TokenKind.Name) {

						database = tokens[currentIndex - 1].Token.UnqoutedImage;

					}

				} else {

					if (currentIndex - 2 >= 0 && tokens[currentIndex - 1].Kind == TokenKind.Dot && tokens[currentIndex - 2].Kind == TokenKind.Name) {

						database = tokens[currentIndex - 2].Token.UnqoutedImage;

					}

				}



				return IsSchema(activeServer, activeConnection, schema, database, out foundSchema, out foundConnection);

			}

			foundSchema = null;

			foundConnection = null;

			return false;

		}



		/// <summary>

		/// See if we are a candidate for auto-generating column_list

		/// INSERT 

		///		[ TOP ( expression ) [ PERCENT ] ] 

		///		[ INTO ] 

		///		{ <object> | rowset_function_limited [ WITH ( <Table_Hint_Limited> [ ...n ] ) ] }

		///		{

		///		[ ( column_list ) ] 

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="currentIndex"></param>

		///<param name="foundTableSource"> </param>

		///<returns></returns>

		public static bool IsCandidateForInsertColumns(List<TokenInfo> lstTokens, int currentIndex, out TableSource foundTableSource) {

			foundTableSource = null;



			TokenInfo token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

			if (null != token && token.Kind == TokenKind.LeftParenthesis) {

				currentIndex--;

				token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

				if (null == token) {

					return false;

				}



				// Handle: [ WITH ( <Table_Hint_Limited> [ ...n ] ) ]

				if (token.Kind == TokenKind.RightParenthesis && -1 != token.MatchingParenToken && currentIndex > token.MatchingParenToken) {

					currentIndex = token.MatchingParenToken - 1;

					token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

					if (null == token || token.Kind != TokenKind.KeywordWith) {

						return false;

					}

					currentIndex--;

					token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

					if (null == token) {

						return false;

					}

				}



				// Handle: <object>

				token = null;

				foreach (TableSource tableSource in TextEditor.CurrentWindowData.Parser.TableSources) {

					if (tableSource.Table.EndIndex == currentIndex) {

						foundTableSource = tableSource;

						currentIndex = tableSource.Table.StartIndex - 1;

						token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

						break;

					}

				}

				if (null != token) {

					// Handle: [ INTO ]

					if (token.Kind == TokenKind.KeywordInto) {

						currentIndex--;

						token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

						if (null == token) {

							return false;

						}

					}



					// Handle: [ TOP ( expression ) [ PERCENT ] ]

					if (token.Kind == TokenKind.KeywordPercent) {

						currentIndex--;

						token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

						if (null == token) {

							return false;

						}

					}

					if (token.Kind == TokenKind.RightParenthesis && -1 != token.MatchingParenToken && currentIndex > token.MatchingParenToken) {

						currentIndex = token.MatchingParenToken - 1;

						token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

						if (null == token || token.Kind != TokenKind.KeywordTop) {

							return false;

						}

						currentIndex--;

						token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

						if (null == token) {

							return false;

						}

					}



					// Handle: INSERT

					if (token.Kind == TokenKind.KeywordInsert) {

						return true;

					}

				}

			}



			return false;

		}



		/// <summary>

		/// Is the supplied schemaName a schema in database databaseName?

		/// </summary>

		/// <param name="objActiveServer"></param>

		/// <param name="objActiveConnection"></param>

		/// <param name="schemaName"></param>

		/// <param name="databaseName"></param>

		/// <param name="foundSchema"></param>

		/// <param name="foundConnection"></param>

		/// <returns></returns>

		public static bool IsSchema(Server objActiveServer, Connection objActiveConnection, string schemaName, string databaseName, out SysObjectSchema foundSchema, out Connection foundConnection) {

			foundSchema = null;

			foundConnection = null;



			if (null != objActiveConnection) {

				if (objActiveConnection.ActiveConnection.DatabaseName.Equals(databaseName, StringComparison.OrdinalIgnoreCase)) {

					if (IsSchema(objActiveConnection, schemaName, databaseName, out foundSchema)) {

						foundConnection = objActiveConnection;

						return true;

					}

				} else {

					foreach (Connection connection in objActiveServer.Connections) {

						if (connection.ActiveConnection.DatabaseName.Equals(databaseName, StringComparison.OrdinalIgnoreCase)) {

							foundConnection = connection;

							return IsSchema(connection, schemaName, databaseName, out foundSchema);

						}

					}



					if (Server.AddNewConnection(objActiveServer, databaseName, out objActiveConnection)) {

						foundConnection = objActiveConnection;

						return IsSchema(objActiveConnection, schemaName, databaseName, out foundSchema);

					}

					return false;

				}

			}



			return false;

		}



		/// <summary>

		/// Is the supplied schemaName a schema in database databaseName?

		/// </summary>

		/// <param name="objActiveConnection"></param>

		/// <param name="schemaName"></param>

		/// <param name="databaseName"></param>

		/// <param name="foundSchema"></param>

		/// <returns></returns>

		private static bool IsSchema(Connection objActiveConnection, string schemaName, string databaseName, out SysObjectSchema foundSchema) {

			foundSchema = null;

			if (null != objActiveConnection) {

				List<SysObjectSchema> sysObjectSchemas = objActiveConnection.GetSysObjectSchemas();

				foreach (SysObjectSchema schema in sysObjectSchemas) {

					if (null != schema.Schema && schemaName.Equals(schema.Schema, StringComparison.OrdinalIgnoreCase) && schema.Connection.ActiveConnection.DatabaseName.Equals(databaseName, StringComparison.OrdinalIgnoreCase)) {

						foundSchema = schema;

						return true;

					}

				}

			}

			return false;

		}



		//DECLARE 

		//     {{ @local_variable [AS] data_type }

		//    | { @cursor_variable_name CURSOR }

		//    | { @table_variable_name [AS] < table_type_definition > }

		//     } [ ,...n]

		public static bool IsInStatementDeclare(List<TokenInfo> lstTokens, int currentIndex) {

			int parenLevel = -1;



			while (currentIndex >= 0) {

				TokenInfo token = lstTokens[currentIndex];

				if (-1 == parenLevel) {

					parenLevel = token.ParenLevel;

				}

				if (token.ParenLevel == parenLevel) {

					if (token.Kind == TokenKind.KeywordDeclare) {

						return true;

					}

					if (!(token.Type == TokenType.Comment || token.Type == TokenType.DataType || token.Kind == TokenKind.Comma || token.Kind == TokenKind.RightParenthesis || token.Type == TokenType.Identifier || token.Kind == TokenKind.KeywordAs || token.Kind == TokenKind.KeywordCursor || token.Kind == TokenKind.Variable)) {

						return false;

					}

				}

				currentIndex--;

			}

			return false;

		}



		/// <summary>

		/// Find out if this token is an table alias. Look for AS keyword and/or table name / derived table

		/// </summary>

		/// <param name="lstTokens"></param>

		/// <param name="currentIndex"></param>

		/// <param name="table"></param>

		/// <returns></returns>

		public static bool IsTableAlias(List<TokenInfo> lstTokens, int currentIndex, string table) {

			if (currentIndex - 1 >= 0) {

				currentIndex--;

				TokenInfo token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);



				if (token.Kind == TokenKind.KeywordAs) {

					if (currentIndex - 1 >= 0) {

						currentIndex--;

						token = GetPreviousNonCommentToken(lstTokens, ref currentIndex);

					}

				}

				if (token.Type == TokenType.Identifier) {

					if (token.Token.UnqoutedImage.Equals(table, StringComparison.OrdinalIgnoreCase)) {

						return true;

					}

				} else if (token.Kind == TokenKind.RightParenthesis) {

					return true;

				}

			}

			return false;

		}



		//	DELETE 

		//		[ TOP ( expression ) [ PERCENT ] ] 

		//		[ FROM ] 

		//  .....

		public static bool IsInStatementDelete(List<TokenInfo> lstTokens, int currentIndex) {

			int parenLevel = -1;



			while (currentIndex >= 0) {

				TokenInfo token = lstTokens[currentIndex];

				if (-1 == parenLevel) {

					parenLevel = token.ParenLevel;

				}

				if (token.ParenLevel == parenLevel) {

					if (token.Kind == TokenKind.KeywordDelete) {

						return true;

					}

					if (!(token.Type == TokenType.Comment || token.Kind == TokenKind.KeywordFrom || token.Kind == TokenKind.KeywordPercent || token.Kind == TokenKind.KeywordTop || token.Kind == TokenKind.RightParenthesis)) {

						return false;

					}

				}

				currentIndex--;

			}

			return false;

		}



		//[ { EXEC | EXECUTE } ]

		//    { 

		//      [ @return_status = ]

		//      { module_name [ ;number ] | @module_name_var } 

		//

		// NOTE: Only part of Execute statement check is validated

		public static bool IsInStatementExecute(List<TokenInfo> lstTokens, int currentIndex) {

			while (currentIndex >= 0) {

				TokenInfo token = lstTokens[currentIndex];

				if (token.Kind == TokenKind.KeywordExec) {

					return true;

				}

				if (!(token.Type == TokenType.Comment || token.Kind == TokenKind.Assign || token.Kind == TokenKind.Variable)) {

					return false;

				}

				currentIndex--;

			}

			return false;

		}



		/// <summary>

		/// Is this a TableSample statement? If so return the end index of the last token

		///    TABLESAMPLE [SYSTEM] ( sample_number [ PERCENT | ROWS ] ) [ REPEATABLE ( repeat_seed ) ]

		/// </summary>

		/// <param name="tokens"></param>

		/// <param name="currentIndex"></param>

		/// <param name="statementEndIndex"></param>

		/// <returns></returns>

		public static bool IsInStatementTableSample(List<TokenInfo> tokens, int currentIndex, out int statementEndIndex) {

			statementEndIndex = -1;



			TokenInfo token = GetNextNonCommentToken(tokens, ref currentIndex);

			if (null != token && token.Kind == TokenKind.KeywordTableSample) {

				currentIndex++;

				token = GetNextNonCommentToken(tokens, ref currentIndex);

				if (null != token && token.Kind == TokenKind.KeywordSystem) {

					currentIndex++;

					token = GetNextNonCommentToken(tokens, ref currentIndex);

				}

				if (null != token) {

					int matchingParenToken = token.MatchingParenToken;



					// ... ( sample_number [ PERCENT | ROWS ] ) [ REPEATABLE ( repeat_seed ) ]

					if (token.Kind == TokenKind.LeftParenthesis && -1 != matchingParenToken && currentIndex < matchingParenToken) {

						currentIndex++;

						token = GetNextNonCommentToken(tokens, ref currentIndex);

						if (null != token && token.Kind == TokenKind.ValueNumber) {

							currentIndex++;

							token = GetNextNonCommentToken(tokens, ref currentIndex);

							if (null != token && (token.Kind == TokenKind.KeywordPercent || token.Kind == TokenKind.KeywordRows)) {

								currentIndex++;

								token = GetNextNonCommentToken(tokens, ref currentIndex);

							}

							if (null != token) {

								currentIndex = matchingParenToken + 1;

								token = GetNextNonCommentToken(tokens, ref currentIndex);

								if (null != token && token.Kind == TokenKind.KeywordRepeatable) {

									currentIndex++;

									token = GetNextNonCommentToken(tokens, ref currentIndex);

									if (null != token) {

										matchingParenToken = token.MatchingParenToken;

										if (token.Kind == TokenKind.LeftParenthesis && -1 != matchingParenToken && currentIndex < matchingParenToken) {

											currentIndex++;

											token = GetNextNonCommentToken(tokens, ref currentIndex);

											if (null != token && token.Kind == TokenKind.ValueNumber) {

												statementEndIndex = matchingParenToken;

												return true;

											}

										}

									}

								} else {

									statementEndIndex = currentIndex;

									return true;

								}

							}

						}

					}

				}

			}



			return false;

		}



		/// <summary>

		/// Is this a WITH(tablehint) statement? If so return the end index of the last token

		///   WITH ( < table_hint > [ [ , ]...n ] )

		/// </summary>

		/// <param name="tokens"></param>

		/// <param name="currentIndex"></param>

		/// <param name="staticData"></param>

		/// <param name="statementEndIndex"></param>

		/// <returns></returns>

		public static bool IsInStatementWithTableHint(List<TokenInfo> tokens, int currentIndex, StaticData staticData, out int statementEndIndex) {

			statementEndIndex = -1;



			TokenInfo token = GetNextNonCommentToken(tokens, ref currentIndex);

			if (null != token && token.Kind == TokenKind.KeywordWith) {

				currentIndex++;

				token = GetNextNonCommentToken(tokens, ref currentIndex);

				if (null != token) {

					int matchingParenToken = token.MatchingParenToken;

					if (token.Kind == TokenKind.LeftParenthesis && -1 != matchingParenToken && currentIndex < matchingParenToken) {

						int endIndex = matchingParenToken;



						currentIndex++;

						// Make a note if we find any valid table hints

						bool foundTableHint = false;

						while (currentIndex < endIndex) {

							token = GetNextNonCommentToken(tokens, ref currentIndex);

							if (null != token) {

								if (token.Kind == TokenKind.Comma || token.Kind == TokenKind.LeftParenthesis || token.Kind == TokenKind.RightParenthesis || token.Kind == TokenKind.ValueNumber) {

									// Do nothing

								} else {

									bool foundLocalTableHint = false;

									foreach (Token tableHint in staticData.TableHints) {

										if (token.Kind == tableHint.Kind) {

											foundTableHint = true;

											foundLocalTableHint = true;

											break;

										}

									}

									if (!foundLocalTableHint) {

										return false;

									}

								}

							} else {

								return false;

							}

							currentIndex++;

						}



						statementEndIndex = endIndex;

						return foundTableHint;

					}

				}

			}



			return false;

		}



		/// <summary>

		/// Find the start of the Join statement.

		///	  <table_source> <join_type> <table_source> ON <search_condition>

		///     <join_type> ::= [ { CROSS | { INNER | { { LEFT | RIGHT | FULL } [ OUTER ] } } [ <join_hint> ] } ] JOIN

		///     <join_hint> ::= 

		///        { LOOP | HASH | MERGE | REMOTE }

		/// </summary>

		/// <param name="tokens"></param>

		/// <param name="currentIndex">currentIndex points at the JOIN token</param>

		/// <param name="startIndex"></param>

		/// <returns></returns>

		public static bool FindStartOfJoin(List<TokenInfo> tokens, int currentIndex, out int startIndex) {

			startIndex = -1;



			TokenInfo token = GetPreviousNonCommentToken(tokens, ref currentIndex);

			if (null != token && token.Kind == TokenKind.KeywordJoin) {

				bool joinHintFound = false;

				currentIndex--;

				token = GetPreviousNonCommentToken(tokens, ref currentIndex);

				if (null != token) {

					if (token.Kind == TokenKind.KeywordLoop || token.Kind == TokenKind.KeywordHash || token.Kind == TokenKind.KeywordMerge || token.Kind == TokenKind.KeywordRemote) {

						joinHintFound = true;

						currentIndex--;

						token = GetPreviousNonCommentToken(tokens, ref currentIndex);

					} else if (token.Kind == TokenKind.KeywordInner || token.Kind == TokenKind.KeywordCross) {

						startIndex = currentIndex;

						return true;

					}



					if (null != token) {

						bool requireLeftRightFull = false;

						if (token.Kind == TokenKind.KeywordOuter) {

							requireLeftRightFull = true;

							currentIndex--;

							token = GetPreviousNonCommentToken(tokens, ref currentIndex);

						}



						if (null != token) {

							if (token.Kind == TokenKind.KeywordLeft || token.Kind == TokenKind.KeywordRight || token.Kind == TokenKind.KeywordFull) {

								startIndex = currentIndex;

								return true;

							}

						}

						// Since INNER and OUTER keywords are optional, a join hint may be the start of the Join statement

						if (joinHintFound) {

							currentIndex++;

							GetNextNonCommentToken(tokens, ref currentIndex);

							startIndex = currentIndex;

							return true;

						}

						if (!requireLeftRightFull) {

							startIndex = currentIndex;

							return true;

						}

					}

				}

			}



			return false;

		}

	}

}