// Copyright © 2014, 2016 Oracle and/or its affiliates. All rights reserved.
//
// MySQL for Visual Studio 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 System;
using System.Collections.Generic;
using System.Data.Common;
using System.IO;
using System.Text;
using Antlr.Runtime;
using Antlr.Runtime.Tree;
using MySql.Data.MySqlClient;
using MySql.Data.VisualStudio.Nodes;
using MySql.Parser;
#if CLR4
using System.Linq;
#endif

namespace MySql.Data.VisualStudio.LanguageService
{
  internal static class LanguageServiceUtil
  {
    // Cache of parsed text.
    // This cache is organized by input text then by server version (for each combination of the previous two,
    // returns a CommonTokenStream).
    private static Dictionary<string,  Dictionary<Version, TokenStreamRemovable>> _parserCache =
      new Dictionary<string, Dictionary<Version, TokenStreamRemovable>>();

    private static Dictionary<string, string> _keywords4ResultSets;

    static LanguageServiceUtil()
    {
      _keywords4ResultSets = new Dictionary<string, string>( StringComparer.OrdinalIgnoreCase );
      _keywords4ResultSets.Add("analyze", "");
      _keywords4ResultSets.Add("check", "");
      _keywords4ResultSets.Add("checksum", "");
      _keywords4ResultSets.Add("describe", "");
      _keywords4ResultSets.Add("explain", "");
      _keywords4ResultSets.Add("explain_stmt", "");
      _keywords4ResultSets.Add("optimize", "");
      _keywords4ResultSets.Add("repair", "");
      _keywords4ResultSets.Add("select", "");
      _keywords4ResultSets.Add("show", "");
    }

    public static TokenStreamRemovable GetTokenStream(string sql, Version version)
    {
      Dictionary<Version, TokenStreamRemovable> lines;
      if (_parserCache.TryGetValue(sql, out lines))
      {
        TokenStreamRemovable tsr;
        if( lines.TryGetValue( version, out tsr ) )
          return tsr;
      }
      // no cache entry, then parse
      MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(sql));//ASCIIEncoding.ASCII.GetBytes(sql));
      CaseInsensitiveInputStream input = new CaseInsensitiveInputStream(ms);
      MySQLLexer lexer = new MySQLLexer(input);
      lexer.MySqlVersion = version;
      TokenStreamRemovable tokens = new TokenStreamRemovable(lexer);

      if (lines == null)
      {
        lines = new Dictionary<Version, TokenStreamRemovable>();        
        _parserCache.Add(sql, lines);
      }
      lines.Add(version, tokens);
      return tokens;
    }

    internal static MySQL51Parser.program_return ParseSql(string sql)
    {
      return ParseSql(sql, false);
    }

    internal static MySQL51Parser.program_return ParseSql(string sql, bool expectErrors, out StringBuilder sb)
    {
      CommonTokenStream ts;
      return ParseSql(sql, expectErrors, out sb, out ts);
    }

    internal static MySQL51Parser.program_return ParseSql(string sql, bool expectErrors, out StringBuilder sb, string version)
    {
      Version ver = GetVersion(version);
      CommonTokenStream ts;
      return ParseSql(sql, expectErrors, out sb, out ts, ver);
    }

    internal static MySQL51Parser.program_return ParseSql(
      string sql, bool expectErrors, out StringBuilder sb, out CommonTokenStream tokensOutput, Version version)
    {
      sql = sql.TrimStart();
      MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(sql));//ASCIIEncoding.ASCII.GetBytes(sql));
      CaseInsensitiveInputStream input = new CaseInsensitiveInputStream(ms);
      //ANTLRInputStream input = new ANTLRInputStream(ms);
      MySQLLexer lexer = new MySQLLexer(input);
      lexer.MySqlVersion = version;
      CommonTokenStream tokens = new CommonTokenStream(lexer);
      tokensOutput = tokens;
      return DoParse(tokens, expectErrors, out sb, lexer.MySqlVersion);
    }

    internal static MySQL51Parser.program_return ParseSql(
      string sql, bool expectErrors, out StringBuilder sb, CommonTokenStream tokens)
    {
      DbConnection con = GetConnection();
      return DoParse( tokens, expectErrors, out sb, GetVersion( con.ServerVersion ));
    }

    internal static MySQL51Parser.program_return ParseSql(
      string sql, bool expectErrors, out StringBuilder sb, out CommonTokenStream tokensOutput)
    {
      sql = sql.TrimStart();
      DbConnection con = GetConnection();
      MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(sql));//ASCIIEncoding.ASCII.GetBytes(sql));
      CaseInsensitiveInputStream input = new CaseInsensitiveInputStream(ms);
      //ANTLRInputStream input = new ANTLRInputStream(ms);
      MySQLLexer lexer = new MySQLLexer(input);
      lexer.MySqlVersion = GetVersion( con.ServerVersion );
      CommonTokenStream tokens = new CommonTokenStream(lexer);
      tokensOutput = tokens;
      return DoParse(tokens, expectErrors, out sb, lexer.MySqlVersion);
    }

    private static MySQL51Parser.program_return DoParse( 
      CommonTokenStream tokens, bool expectErrors, out StringBuilder sb, Version version )
    {
      MySQLParser parser = new MySQLParser(tokens);
      parser.MySqlVersion = version;
      sb = new StringBuilder();
      TextWriter tw = new StringWriter(sb);
      parser.TraceDestination = tw;
      MySQL51Parser.program_return r = null;
      int tokCount = tokens.Count;
      try
      {
        r = parser.program();
      }
      catch (RewriteEmptyStreamException e)
      {
        if (!expectErrors)
        {
          sb.AppendLine();
          sb.Append(e.Message);
        }
      }
      /*
       * The parser inserts a new <EOF> to the token stream, this is probably an ANTLR bug, the code here takes care of it.
       * */
      if (( tokens.Count - 1 ) == tokCount)
      {
        TokenStreamRemovable tsr = (TokenStreamRemovable)tokens;
        tsr.Remove(tokens.Get(tokens.Count - 1));
      }
      tokens.Reset();
      return r;
    }

    private static MySQL51Parser.program_return ParseSql(string sql, bool expectErrors)
    {
      StringBuilder sb;
      CommonTokenStream ts;
      return ParseSql(sql, expectErrors, out sb, out ts);
    }

    internal static Version GetVersion( string versionString )
    {
      Version version;
      int i = 0;
      while (i < versionString.Length &&
          (Char.IsDigit(versionString[i]) || versionString[i] == '.'))
        i++;
      version = new Version(versionString.Substring(0, i));
      return version;
    }

    /// <summary>
    /// Gets MySql server version from the connection string (useful for recognize the exact syntax for that version in
    /// the parser's grammar and scanner).
    /// </summary>
    /// <returns></returns>
    internal static Version GetVersion()
    {
      DbConnection con = GetConnection();
      if (con != null)
      {
        return GetVersion(con.ServerVersion);
      }
      else
      {
        // default to server 5.1
        return new Version(5, 1);
      }
    }

    public static DbConnection GetConnection()
    {
      DbConnection connection = DocumentNode.GetCurrentConnection();
      if (connection == null)
      {
        Editors.EditorBroker broker = Editors.EditorBroker.Broker;
        if (broker != null)
        {
          connection = broker.GetCurrentConnection();
        }
      }
      return connection;
    }

    public static string GetCurrentDatabase()
    {
      Editors.EditorBroker broker = Editors.EditorBroker.Broker;
      if (broker != null)
      {
        return broker.GetCurrentDatabase();
      }
      return null;
    }

    public static string GetRoutineName(string sql)
    {
      StringBuilder sb;
      MySQL51Parser.program_return pr = ParseSql(sql, false, out sb);
      if (sb.Length != 0)
      {
        throw new ApplicationException(string.Format("Syntactic error in stored routine: {0}", sb));
      }
      else
      {
        CommonTree t = (CommonTree)pr.Tree;
        if (t.IsNil)
          t = (CommonTree)t.GetChild(0);
        string name;
        if (string.Equals(t.GetChild(1).Text, "definer", StringComparison.OrdinalIgnoreCase))
          name = t.GetChild(3).Text;
        else
          name = t.GetChild(1).Text;
        return name.Replace("`", "");
      }
    }

    /// <summary>
    /// Returns true is the first SQL statement in the string returns a result set 
    /// (after parsing comments and other noise).
    /// </summary>
    /// <param name="sql"></param>
    /// <param name="con"></param>
    /// <returns></returns>
    public static bool DoesStmtReturnResults( string sql, MySqlConnection con )
    {
      StringBuilder sb;
      MySQL51Parser.program_return t = ParseSql( sql, false, out sb, con.ServerVersion );
      ITree tree = t.Tree as ITree;
      if (tree != null && tree.IsNil)
      {
        tree = tree.GetChild(0);
      }

      return tree != null && _keywords4ResultSets.ContainsKey(tree.Text);
    }
  }
}
