/*******************************************************************************
 * 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 java.util.ArrayList;
import java.util.List;

import com.sap.core.odata.api.edm.EdmType;

public interface ParameterSetCombination {

  void add(ParameterSet parameterSet);

  ParameterSet validate(List<EdmType> actualParameterTypes) throws ExpressionParserInternalError;

  void addFirst(ParameterSet parameterSet);

  EdmType getReturnType();

  public static class PSCflex implements ParameterSetCombination {
    public List<ParameterSet> combinations = new ArrayList<ParameterSet>();

    @Override
    public void add(final ParameterSet parameterSet) {
      combinations.add(parameterSet);
    }

    @Override
    public EdmType getReturnType() {
      int parameterCount = combinations.size();
      if (parameterCount == 0) {
        return null;
      }

      if (parameterCount == 1) {
        return combinations.get(0).getReturnType();
      }

      //There are more than 1 possible return type, check if they are equal, if not return null.
      EdmType returnType = combinations.get(0).getReturnType();
      for (int i = 1; i < parameterCount; i++) {
        if (returnType != combinations.get(i)) {
          return null;
        }
      }

      return returnType;

    }

    @Override
    public void addFirst(final ParameterSet parameterSet) {
      List<ParameterSet> oldCombinations = combinations;
      combinations = new ArrayList<ParameterSet>();
      combinations.add(parameterSet);
      for (ParameterSet parameterSet1 : oldCombinations) {
        combinations.add(parameterSet1);
      }

    }

    @Override
    public ParameterSet validate(final List<EdmType> actualParameterTypes) throws ExpressionParserInternalError {
      if (combinations.size() == 0) {
        return new ParameterSet(null, null);
      }

      //first check for exact parameter combination
      for (ParameterSet parameterSet : combinations) {
        boolean s = parameterSet.equals(actualParameterTypes, false);
        if (s) {
          return parameterSet;
        }
      }

      //first check for parameter combination with promotion
      for (ParameterSet parameterSet : combinations) {
        boolean s = parameterSet.equals(actualParameterTypes, true);
        if (s) {
          return parameterSet;
        }
      }
      return null;
    }

  }

  public static class PSCReturnTypeEqLastParameter implements ParameterSetCombination {

    @Override
    public void add(final ParameterSet parameterSet) {
      throw new IllegalStateException();
    }

    @Override
    public void addFirst(final ParameterSet parameterSet) {
      throw new IllegalStateException();
    }

    @Override
    public ParameterSet validate(final List<EdmType> actualParameterTypes) throws ExpressionParserInternalError {
      EdmType xxx = actualParameterTypes.get(actualParameterTypes.size() - 1);
      return new ParameterSet(xxx, null);
      //return actualParameterTypes.get(actualParameterTypes.size() - 1);
    }

    @Override
    public EdmType getReturnType() {
      //If the return type is always the type of the last parameter of the actual parameters ( e.g. when using the method operator) 
      //then the return type can not predicted.
      return null;
    }
  }

}