/**
    *    Copyright 2009-2019 the original author or authors.
    *
    *    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 org.apache.ibatis.reflection;
  
  import java.lang.annotation.Annotation;
  import java.lang.reflect.Method;
  import java.util.Collections;
  import java.util.Map;
  import java.util.SortedMap;
  import java.util.TreeMap;
  
  import org.apache.ibatis.annotations.Param;
  import org.apache.ibatis.binding.MapperMethod.ParamMap;
  import org.apache.ibatis.session.Configuration;
  import org.apache.ibatis.session.ResultHandler;
  import org.apache.ibatis.session.RowBounds;
  
  public class ParamNameResolver {
  
    public static final String GENERIC_NAME_PREFIX = "param";
  
    /**
     * <p>
     * The key is the index and the value is the name of the parameter.<br />
     * The name is obtained from {@link Param} if specified. When {@link Param} is not specified,
     * the parameter index is used. Note that this index could be different from the actual index
     * when the method has special parameters (i.e. {@link RowBounds} or {@link ResultHandler}).
     * </p>
     * <ul>
     * <li>aMethod(@Param("M") int a, @Param("N") int b) -&gt; {{0, "M"}, {1, "N"}}</li>
     * <li>aMethod(int a, int b) -&gt; {{0, "0"}, {1, "1"}}</li>
     * <li>aMethod(int a, RowBounds rb, int b) -&gt; {{0, "0"}, {2, "1"}}</li>
     * </ul>
     */
    private final SortedMap<Integer, String> names;
  
    private boolean hasParamAnnotation;
  
    public ParamNameResolver(Configuration config, Method method) {
      final Class<?>[] paramTypes = method.getParameterTypes();
      final Annotation[][] paramAnnotations = method.getParameterAnnotations();
      final SortedMap<Integer, String> map = new TreeMap<>();
      int paramCount = paramAnnotations.length;
      // get names from @Param annotations
      for (int paramIndex = 0; paramIndex < paramCount; paramIndex++) {
        if (isSpecialParameter(paramTypes[paramIndex])) {
          // skip special parameters
          continue;
        }
        String name = null;
        for (Annotation annotation : paramAnnotations[paramIndex]) {
          if (annotation instanceof Param) {
            hasParamAnnotation = true;
            name = ((Param) annotation).value();
            break;
          }
        }
        if (name == null) {
          // @Param was not specified.
          if (config.isUseActualParamName()) {
            name = getActualParamName(method, paramIndex);
          }
          if (name == null) {
            // use the parameter index as the name ("0", "1", ...)
            // gcode issue #71
            name = String.valueOf(map.size());
          }
        }
        map.put(paramIndex, name);
      }
      names = Collections.unmodifiableSortedMap(map);
    }
  
    private String getActualParamName(Method method, int paramIndex) {
      return ParamNameUtil.getParamNames(method).get(paramIndex);
    }
  
    private static boolean isSpecialParameter(Class<?> clazz) {
      return RowBounds.class.isAssignableFrom(clazz) || ResultHandler.class.isAssignableFrom(clazz);
    }
  
    /**
     * Returns parameter names referenced by SQL providers.
     */
    public String[] getNames() {
      return names.values().toArray(new String[0]);
   }
 
   /**
    * <p>
    * A single non-special parameter is returned without a name.
    * Multiple parameters are named using the naming rule.
    * In addition to the default names, this method also adds the generic names (param1, param2,
    * ...).
    * </p>
    */
   public Object getNamedParams(Object[] args) {
     final int paramCount = names.size();
     if (args == null || paramCount == 0) {
       return null;
     } else if (!hasParamAnnotation && paramCount == 1) {
       return args[names.firstKey()];
     } else {
       final Map<String, Object> param = new ParamMap<>();
       int i = 0;
       for (Map.Entry<Integer, String> entry : names.entrySet()) {
         param.put(entry.getValue(), args[entry.getKey()]);
         // add generic param names (param1, param2, ...)
         final String genericParamName = GENERIC_NAME_PREFIX + (i + 1);
         // ensure not to overwrite parameter named with @Param
         if (!names.containsValue(genericParamName)) {
           param.put(genericParamName, args[entry.getKey()]);
         }
         i++;
       }
       return param;
     }
   }
 }