/*******************************************************************************
 * Copyright 2013 SAP AG
 * 
 * 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.
 ******************************************************************************/
package com.sap.core.odata.core.uri.expression;

import com.sap.core.odata.api.edm.EdmEntityType;
import com.sap.core.odata.api.uri.expression.CommonExpression;
import com.sap.core.odata.api.uri.expression.ExpressionParserException;
import com.sap.core.odata.api.uri.expression.OrderByExpression;
import com.sap.core.odata.api.uri.expression.SortOrder;

public class OrderByParserImpl extends FilterParserImpl implements OrderByParser {
  public OrderByParserImpl(final EdmEntityType resourceEntityType) {
    super(resourceEntityType);
  }

  @Override
  public OrderByExpression parseOrderByString(final String orderByExpression) throws ExpressionParserException, ExpressionParserInternalError {
    curExpression = orderByExpression;
    OrderByExpressionImpl orderCollection = new OrderByExpressionImpl(curExpression);

    try {
      tokenList = new Tokenizer(orderByExpression).tokenize(); //throws TokenizerMessage
    } catch (TokenizerException tokenizerException) {
      throw FilterParserExceptionImpl.createERROR_IN_TOKENIZER(tokenizerException, curExpression);
    }

    while (true) {
      CommonExpression node = null;
      try {
        CommonExpression nodeLeft = readElement(null);
        node = readElements(nodeLeft, 0);
      } catch (ExpressionParserException expressionException) {
        expressionException.setFilterTree(orderCollection);
        throw expressionException;
      }

      OrderExpressionImpl orderNode = new OrderExpressionImpl(node);

      //read the sort order
      Token token = tokenList.lookToken();
      if (token == null) {
        orderNode.setSortOrder(SortOrder.asc);
      } else if ((token.getKind() == TokenKind.LITERAL) && (token.getUriLiteral().equals("asc"))) {
        orderNode.setSortOrder(SortOrder.asc);
        tokenList.next();
        token = tokenList.lookToken();
      } else if ((token.getKind() == TokenKind.LITERAL) && (token.getUriLiteral().equals("desc"))) {
        orderNode.setSortOrder(SortOrder.desc);
        tokenList.next();
        token = tokenList.lookToken();
      } else if (token.getKind() == TokenKind.COMMA) {
        orderNode.setSortOrder(SortOrder.asc);
      } else {
        // Tested with TestParserExceptions.TestOPMparseOrderByString CASE 1
        throw FilterParserExceptionImpl.createINVALID_SORT_ORDER(token, curExpression);
      }

      orderCollection.addOrder(orderNode);

      //ls_token may be a ',' or  empty.
      if (token == null) {
        break;
      } else if (token.getKind() == TokenKind.COMMA) {
        Token oldToken = token;
        tokenList.next();
        token = tokenList.lookToken();

        if (token == null) {
          // Tested with TestParserExceptions.TestOPMparseOrderByString CASE 2
          throw FilterParserExceptionImpl.createEXPRESSION_EXPECTED_AFTER_POS(oldToken, curExpression);
        }
      } else { //e.g. in case $orderby=String asc a

        throw FilterParserExceptionImpl.createCOMMA_OR_END_EXPECTED_AT_POS(token, curExpression);
      }

    }
    return orderCollection;
  }
}