#if MYSQL_6_10

// Copyright © 2009, 2016 Oracle and/or its affiliates. All rights reserved.
//
// MySQL Connector/NET is licensed under the terms of the GPLv2
// <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most 
// MySQL Connectors. There are special exceptions to the terms and 
// conditions of the GPLv2 as it is applied to this software, see the 
// FLOSS License Exception
// <http://www.mysql.com/about/legal/licensing/foss-exception.html>.
//
// This program is free software; you can redistribute it and/or modify 
// it under the terms of the GNU General Public License as published 
// by the Free Software Foundation; version 2 of the License.
//
// This program is distributed in the hope that it will be useful, but 
// WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
// for more details.
//
// You should have received a copy of the GNU General Public License along 
// with this program; if not, write to the Free Software Foundation, Inc., 
// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

using Externals.MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;


namespace Externals.MySql.Data.Common
{
    internal class QueryNormalizer
    {
        private static readonly List<string> Keywords = new List<string>();
        private readonly List<Token> _tokens = new List<Token>();
        private int _pos;
        private string _fullSql;
        private string _queryType;

        static QueryNormalizer()
        {
            Keywords.AddRange(Resources.Keywords);
        }

        public string QueryType => _queryType;

        public string Normalize(string sql)
        {
            _tokens.Clear();
            StringBuilder newSql = new StringBuilder();
            _fullSql = sql;

            TokenizeSql(sql);
            DetermineStatementType(_tokens);
            ProcessMathSymbols(_tokens);
            CollapseValueLists(_tokens);
            CollapseInLists(_tokens);
            CollapseWhitespace(_tokens);

            foreach (Token t in _tokens.Where(t => t.Output))
                newSql.Append(t.Text);

            return newSql.ToString();
        }

        private void DetermineStatementType(List<Token> tok)
        {
            foreach (Token t in tok.Where(t => t.Type == TokenType.Keyword))
            {
                _queryType = t.Text.ToUpperInvariant();
                break;
            }
        }

        /// <summary>
        /// Mark - or + signs that are unary ops as no output
        /// </summary>
        /// <param name="tok"></param>
        private static void ProcessMathSymbols(List<Token> tok)
        {
            Token lastToken = null;

            foreach (Token t in tok)
            {
                if (t.Type == TokenType.Symbol &&
                    (t.Text == "-" || t.Text == "+"))
                {
                    if (lastToken != null &&
                        lastToken.Type != TokenType.Number &&
                        lastToken.Type != TokenType.Identifier &&
                        (lastToken.Type != TokenType.Symbol || lastToken.Text != ")"))
                        t.Output = false;
                }
                if (t.IsRealToken)
                    lastToken = t;
            }
        }

        private static void CollapseWhitespace(List<Token> tok)
        {
            Token lastToken = null;

            foreach (Token t in tok)
            {
                if (t.Output &&
                    t.Type == TokenType.Whitespace &&
                    lastToken != null &&
                    lastToken.Type == TokenType.Whitespace)
                {
                    t.Output = false;
                }
                if (t.Output)
                    lastToken = t;
            }
        }

        private void CollapseValueLists(List<Token> tok)
        {
            int pos = -1;
            while (++pos < tok.Count)
            {
                Token t = tok[pos];
                if (t.Type != TokenType.Keyword) continue;
                if (!t.Text.StartsWith("VALUE", StringComparison.OrdinalIgnoreCase)) continue;
                CollapseValueList(tok, ref pos);
            }
        }

        private void CollapseValueList(List<Token> tok, ref int pos)
        {
            List<int> parenIndices = new List<int>();

            // this while loop will find all closing parens in this value list
            while (true)
            {
                // find the close ')'
                while (++pos < tok.Count)
                {
                    if (tok[pos].Type == TokenType.Symbol && tok[pos].Text == ")")
                        break;
                    if (pos == tok.Count - 1)
                        break;
                }
                parenIndices.Add(pos);

                // now find the next "real" token
                while (++pos < tok.Count)
                    if (tok[pos].IsRealToken) break;
                if (pos == tok.Count) break;

                if (tok[pos].Text == ",") continue;
                pos--;
                break;
            }

            // if we only have 1 value then we don't collapse
            if (parenIndices.Count < 2) return;
            int index = parenIndices[0];
            tok[++index] = new Token(TokenType.Whitespace, " ");
            tok[++index] = new Token(TokenType.Comment, "/* , ... */");
            index++;

            // now mark all the other tokens as no output
            while (index <= parenIndices[parenIndices.Count - 1])
                tok[index++].Output = false;
        }

        private void CollapseInLists(List<Token> tok)
        {
            int pos = -1;
            while (++pos < tok.Count)
            {
                Token t = tok[pos];
                if (t.Type != TokenType.Keyword) continue;
                if (t.Text != "IN") continue;
                CollapseInList(tok, ref pos);
            }
        }

        private static Token GetNextRealToken(List<Token> tok, ref int pos)
        {
            while (++pos < tok.Count)
            {
                if (tok[pos].IsRealToken) return tok[pos];
            }
            return null;
        }

        private static void CollapseInList(List<Token> tok, ref int pos)
        {
            Token t = GetNextRealToken(tok, ref pos);
            // Debug.Assert(t.Text == "(");
            if (t == null)
                return;

            // if the first token is a keyword then we likely have a 
            // SELECT .. IN (SELECT ...)
            t = GetNextRealToken(tok, ref pos);
            if (t == null || t.Type == TokenType.Keyword) return;

            int start = pos;
            // first find all the tokens that make up the in list
            while (++pos < tok.Count)
            {
                t = tok[pos];
                if (t.Type == TokenType.CommandComment) return;
                if (!t.IsRealToken) continue;
                if (t.Text == "(") return;
                if (t.Text == ")") break;
            }
            int stop = pos;

            for (int i = stop; i > start; i--)
                tok.RemoveAt(i);
            tok.Insert(++start, new Token(TokenType.Whitespace, " "));
            tok.Insert(++start, new Token(TokenType.Comment, "/* , ... */"));
            tok.Insert(++start, new Token(TokenType.Whitespace, " "));
            tok.Insert(++start, new Token(TokenType.Symbol, ")"));
        }

        private void TokenizeSql(string sql)
        {
            _pos = 0;

            while (_pos < sql.Length)
            {
                char c = sql[_pos];
                if (LetterStartsComment(c) && ConsumeComment())
                    continue;
                if (Char.IsWhiteSpace(c))
                    ConsumeWhitespace();
                else if (c == '\'' || c == '\"' || c == '`')
                    ConsumeQuotedToken(c);
                else if (!IsSpecialCharacter(c))
                    ConsumeUnquotedToken();
                else
                    ConsumeSymbol();
            }
        }

        private bool LetterStartsComment(char c)
        {
            return c == '#' || c == '/' || c == '-';
        }

        private bool IsSpecialCharacter(char c)
        {
            return !Char.IsLetterOrDigit(c) && c != '$' && c != '_' && c != '.';
        }

        private bool ConsumeComment()
        {
            char c = _fullSql[_pos];
            // make sure the comment starts correctly
            if (c == '/' && ((_pos + 1) >= _fullSql.Length || _fullSql[_pos + 1] != '*')) return false;
            if (c == '-' && ((_pos + 2) >= _fullSql.Length || _fullSql[_pos + 1] != '-' || _fullSql[_pos + 2] != ' ')) return false;

            string endingPattern = "\n";
            if (c == '/')
                endingPattern = "*/";

            int startingIndex = _pos;

            int index = _fullSql.IndexOf(endingPattern, _pos);
            if (index == -1)
                index = _fullSql.Length - 1;
            else
                index += endingPattern.Length;
            string comment = _fullSql.Substring(_pos, index - _pos);
            if (comment.StartsWith("/*!", StringComparison.Ordinal))
                _tokens.Add(new Token(TokenType.CommandComment, comment));
            _pos = index;
            return true;
        }

        private void ConsumeSymbol()
        {
            char c = _fullSql[_pos++];
            _tokens.Add(new Token(TokenType.Symbol, c.ToString()));
        }

        private void ConsumeQuotedToken(char c)
        {
            bool escaped = false;
            int start = _pos;
            _pos++;
            while (_pos < _fullSql.Length)
            {
                char x = _fullSql[_pos];

                if (x == c && !escaped) break;

                if (escaped)
                    escaped = false;
                else if (x == '\\')
                    escaped = true;
                _pos++;
            }
            _pos++;
            _tokens.Add(c == '\''
              ? new Token(TokenType.String, "?")
              : new Token(TokenType.Identifier, _fullSql.Substring(start, _pos - start)));
        }

        private void ConsumeUnquotedToken()
        {
            int startPos = _pos;
            while (_pos < _fullSql.Length && !IsSpecialCharacter(_fullSql[_pos]))
                _pos++;
            string word = _fullSql.Substring(startPos, _pos - startPos);
            double v;
            if (Double.TryParse(word, out v))
                _tokens.Add(new Token(TokenType.Number, "?"));
            else
            {
                Token t = new Token(TokenType.Identifier, word);
                if (IsKeyword(word))
                {
                    t.Type = TokenType.Keyword;
                    t.Text = t.Text.ToUpperInvariant();
                }
                _tokens.Add(t);
            }
        }

        private void ConsumeWhitespace()
        {
            _tokens.Add(new Token(TokenType.Whitespace, " "));
            while (_pos < _fullSql.Length && Char.IsWhiteSpace(_fullSql[_pos]))
                _pos++;
        }

        private static bool IsKeyword(string word)
        {
            return Keywords.Contains(word.ToUpperInvariant());
        }
    }

    internal class Token
    {
        public TokenType Type;
        public string Text;
        public bool Output;

        public Token(TokenType type, string text)
        {
            Type = type;
            Text = text;
            Output = true;
        }

        public bool IsRealToken => Type != TokenType.Comment &&
                                   Type != TokenType.CommandComment &&
                                   Type != TokenType.Whitespace &&
                                   Output;
    }

    internal enum TokenType
    {
        Keyword,
        String,
        Number,
        Symbol,
        Identifier,
        Comment,
        CommandComment,
        Whitespace
    }
}

#endif