/*
 *    The contents of this file are subject to the Initial
 *    Developer's Public License Version 1.0 (the "License");
 *    you may not use this file except in compliance with the
 *    License. You may obtain a copy of the License at
 *    https://github.com/FirebirdSQL/NETProvider/blob/master/license.txt.
 *
 *    Software distributed under the License is distributed on
 *    an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either
 *    express or implied. See the License for the specific
 *    language governing rights and limitations under the License.
 *
 *    All Rights Reserved.
 */

//$Authors = Abel Eduardo Pereira, Jiri Cincura (jiri@cincura.net)

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;

namespace FirebirdSql.Data.Isql
{
	class SqlStringParser
	{
		string _source;
		int _sourceLength;
		string[] _tokens;

		public string[] Tokens
		{
			get { return _tokens; }
			set
			{
				if (value == null)
					throw new ArgumentNullException();
				foreach (var item in value)
				{
					if (value == null)
						throw new ArgumentNullException();
					if (string.IsNullOrEmpty(item))
						throw new ArgumentException();
				}
				_tokens = value;
			}
		}

		public SqlStringParser(string targetString)
		{
			_tokens = new[] { " " };
			_source = targetString;
			_sourceLength = targetString.Length;
		}

		public IEnumerable<FbStatement> Parse()
		{
			var lastYield = 0;
			var index = 0;
			var rawResult = new StringBuilder();
			while (true)
			{
				Continue:
				{ }
				if (index >= _sourceLength)
				{
					break;
				}
				if (GetChar(index) == '\'')
				{
					rawResult.Append(GetChar(index));
					index++;
					rawResult.Append(ProcessLiteral(ref index));
					rawResult.Append(GetChar(index));
					index++;
				}
				else if (GetChar(index) == '-' && GetNextChar(index) == '-')
				{
					index++;
					ProcessSinglelineComment(ref index);
					index++;
				}
				else if (GetChar(index) == '/' && GetNextChar(index) == '*')
				{
					index++;
					ProcessMultilineComment(ref index);
					index++;
				}
				else
				{
					foreach (var token in Tokens)
					{
						if (string.Compare(_source, index, token, 0, token.Length, StringComparison.Ordinal) == 0)
						{
							index += token.Length;
							yield return new FbStatement(_source.Substring(lastYield, index - lastYield - token.Length), rawResult.ToString());
							lastYield = index;
							rawResult.Clear();
							goto Continue;
						}
					}
					if (!(rawResult.Length == 0 && char.IsWhiteSpace(GetChar(index))))
					{
						rawResult.Append(GetChar(index));
					}
					index++;
				}
			}

			if (index >= _sourceLength)
			{
				var parsed = _source.Substring(lastYield);
				if (parsed.Trim() == string.Empty)
				{
					yield break;
				}
                yield return new FbStatement(parsed, rawResult.ToString());
				lastYield = _sourceLength;
				rawResult.Clear();
			}
			else
			{
				yield return new FbStatement(_source.Substring(lastYield, index - lastYield), rawResult.ToString());
				lastYield = index;
				rawResult.Clear();
			}
		}

		string ProcessLiteral(ref int index)
		{
			var sb = new StringBuilder();
			while (index < _sourceLength)
			{
				if (GetChar(index) == '\'')
				{
					if (GetNextChar(index) == '\'')
					{
						sb.Append(GetChar(index));
						index++;
					}
					else
					{
						break;
					}
				}
				sb.Append(GetChar(index));
				index++;
			}
			return sb.ToString();
		}

		void ProcessMultilineComment(ref int index)
		{
			while (index < _sourceLength)
			{
				if (GetChar(index) == '*' && GetNextChar(index) == '/')
				{
					index++;
					break;
				}
				index++;
			}
		}

		void ProcessSinglelineComment(ref int index)
		{
			while (index < _sourceLength)
			{
				if (GetChar(index) == '\n')
				{
					break;
				}
				if (GetChar(index) == '\r')
				{
					if (GetNextChar(index) == '\n')
					{
						index++;
					}
					break;
				}
				index++;
			}
		}

		char GetChar(int index)
		{
			return _source[index];
		}

		char? GetNextChar(int index)
		{
			return index + 1 < _sourceLength
				? _source[index + 1]
				: (char?)null;
		}
	}
}
