// *************************************************************************** }
//
// Delphi MVC Framework
//
// Copyright (c) 2010-2019 Daniele Teti and the DMVCFramework Team
//
// https://github.com/danieleteti/delphimvcframework
//
// ***************************************************************************
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// ***************************************************************************

unit MVCFramework.RQL.AST2MSSQL;

interface

uses
  MVCFramework.RQL.Parser,
  MVCFramework.Commons;

type
  TRQLMSSQLCompiler = class(TRQLCompiler)
  private
    FMapping: TMVCFieldsMapping;
    function RQLFilterToSQL(const aRQLFIlter: TRQLFilter): string;
    function RQLSortToSQL(const aRQLSort: TRQLSort): string;
    function RQLLimitToSQL(const aRQLLimit: TRQLLimit): string;
    function RQLWhereToSQL(const aRQLWhere: TRQLWhere): string;
    function RQLLogicOperatorToSQL(const aRQLFIlter: TRQLLogicOperator): string;
    function RQLCustom2SQL(const aRQLCustom: TRQLCustom): string;
  public
    constructor Create(const Mapping: TMVCFieldsMapping); override;
    procedure AST2SQL(const aRQLAST: TRQLAbstractSyntaxTree; out aSQL: string); override;
  end;

implementation

uses
  System.SysUtils;

{ TRQLMSSQLCompiler }

constructor TRQLMSSQLCompiler.Create(const Mapping: TMVCFieldsMapping);
begin
  inherited Create(Mapping);
  FMapping := Mapping;
end;

function TRQLMSSQLCompiler.RQLCustom2SQL(
  const aRQLCustom: TRQLCustom): string;
begin
  if aRQLCustom is TRQLFilter then
  begin
    Result := RQLFilterToSQL(TRQLFilter(aRQLCustom));
  end
  else if aRQLCustom is TRQLLogicOperator then
  begin
    Result := RQLLogicOperatorToSQL(TRQLLogicOperator(aRQLCustom));
  end
  else if aRQLCustom is TRQLSort then
  begin
    Result := RQLSortToSQL(TRQLSort(aRQLCustom));
  end
  else if aRQLCustom is TRQLLimit then
  begin
    Result := RQLLimitToSQL(TRQLLimit(aRQLCustom));
  end
  else if aRQLCustom is TRQLWhere then
  begin
    Result := RQLWhereToSQL(TRQLWhere(aRQLCustom));
  end
  else
    raise ERQLException.CreateFmt('Unknown token in compiler: %s', [aRQLCustom.ClassName]);
end;

function TRQLMSSQLCompiler.RQLFilterToSQL(const aRQLFIlter: TRQLFilter): string;
var
  lValue, lDBFieldName: string;
begin
  if aRQLFIlter.RightValueType = vtString then
    lValue := aRQLFIlter.OpRight.QuotedString('''')
  else if aRQLFIlter.RightValueType = vtBoolean then
  begin
    if SameText(aRQLFIlter.OpRight, 'true') then
      lValue := '1'
    else
      lValue := '0';
  end
  else
    lValue := aRQLFIlter.OpRight;

  lDBFieldName := GetDatabaseFieldName(aRQLFIlter.OpLeft);

  case aRQLFIlter.Token of
    tkEq:
      begin
        if aRQLFIlter.RightValueType = vtNull then
          Result := Format('(%s IS NULL)', [lDBFieldName])
        else
          Result := Format('(%s = %s)', [lDBFieldName, lValue]);
      end;
    tkLt:
      begin
        Result := Format('(%s < %s)', [lDBFieldName, lValue]);
      end;
    tkLe:
      begin
        Result := Format('(%s <= %s)', [lDBFieldName, lValue]);
      end;
    tkGt:
      begin
        Result := Format('(%s > %s)', [lDBFieldName, lValue]);
      end;
    tkGe:
      begin
        Result := Format('(%s >= %s)', [lDBFieldName, lValue]);
      end;
    tkNe:
      begin
        if aRQLFIlter.RightValueType = vtNull then
          Result := Format('(%s IS NOT NULL)', [lDBFieldName])
        else
          Result := Format('(%s != %s)', [lDBFieldName, lValue]);
      end;
    tkContains:
      begin
        Result := Format('(LOWER(%s) LIKE ''%%%s%%'')', [lDBFieldName, lValue.DeQuotedString.ToLower])
      end;
    tkIn:
      begin
        case aRQLFIlter.RightValueType of
          vtIntegerArray: // if array is empty, RightValueType is always vtIntegerArray
            begin
              Result := Format('(%s IN (%s))', [
                lDBFieldName, string.Join(',', aRQLFIlter.OpRightArray)
                ]);
            end;
          vtStringArray:
            begin
              Result := Format('(%s IN (''%s''))', [
                lDBFieldName, string.Join(''',''', aRQLFIlter.OpRightArray)
                ]);
            end;
        else
          raise ERQLException.Create('Invalid RightValueType for tkIn');
        end;
      end;
  end;
end;

function TRQLMSSQLCompiler.RQLLimitToSQL(const aRQLLimit: TRQLLimit): string;
begin
  Result := Format(' /*limit*/ OFFSET %d ROWS FETCH NEXT %d ROWS ONLY', [aRQLLimit.Start, aRQLLimit.Count]);
end;

function TRQLMSSQLCompiler.RQLLogicOperatorToSQL(const aRQLFIlter: TRQLLogicOperator): string;
var
  lJoin: string;
  lRQLCustom: TRQLCustom;
  lFirst: Boolean;
begin
  case aRQLFIlter.Token of
    tkAnd:
      begin
        lJoin := ' and ';
      end;
    tkOr:
      begin
        lJoin := ' or ';
      end;
  else
    raise ERQLException.Create('Invalid token in RQLLogicOperator');
  end;

  Result := '';
  lFirst := True;
  for lRQLCustom in aRQLFIlter.FilterAST do
  begin
    if not lFirst then
    begin
      Result := Result + lJoin;
    end;
    lFirst := False;
    Result := Result + RQLCustom2SQL(lRQLCustom);
  end;
  Result := '(' + Result + ')';
end;

function TRQLMSSQLCompiler.RQLSortToSQL(const aRQLSort: TRQLSort): string;
var
  I: Integer;
begin
  Result := ' /*sort*/ ORDER BY';
  for I := 0 to aRQLSort.Fields.Count - 1 do
  begin
    if I > 0 then
      Result := Result + ',';
    Result := Result + ' ' + GetDatabaseFieldName(aRQLSort.Fields[I]);
    if aRQLSort.Signs[I] = '+' then
      Result := Result + ' ASC'
    else
      Result := Result + ' DESC';
  end;
end;

function TRQLMSSQLCompiler.RQLWhereToSQL(const aRQLWhere: TRQLWhere): string;
begin
  Result := ' WHERE ';
end;

procedure TRQLMSSQLCompiler.AST2SQL(const aRQLAST: TRQLAbstractSyntaxTree;
  out aSQL: string);
var
  lBuff: TStringBuilder;
  lItem: TRQLCustom;
  LFoundSort: Boolean;
  LitemSort: TRQLSort;
begin
  inherited;

  {
    Here you can rearrange tokens in the list, for example:
    For firebird and mysql syntax you have: filters, sort, limit (default)
    For MSSQL syntax you need to rearrange in: limit, filters, sort
  }

  LFoundSort := False;
  lBuff := TStringBuilder.Create;
  try
    for lItem in aRQLAST do
    begin

      if (lItem is TRQLLimit) and (not LFoundSort) then
      begin
        LitemSort := TRQLSort.Create;
        LitemSort.Add('+', FMapping[0].InstanceFieldName);
        lBuff.Append(RQLCustom2SQL(LitemSort));
      end;

      lBuff.Append(RQLCustom2SQL(lItem));

      if (lItem is TRQLSort) then
        LFoundSort := True;

    end;
    aSQL := lBuff.ToString;
  finally
    lBuff.Free;
  end;
end;

initialization

TRQLCompilerRegistry.Instance.RegisterCompiler('mssql', TRQLMSSQLCompiler);

finalization

TRQLCompilerRegistry.Instance.UnRegisterCompiler('mssql');

end.