/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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
    *
   *   https://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.bcel.classfile;
  
  import java.io.DataInput;
  import java.io.DataOutputStream;
  import java.io.IOException;
  
  import org.apache.bcel.Const;
  
  /**
   * The element_value structure is documented at https://docs.oracle.com/javase/specs/jvms/se11/html/jvms-4.html#jvms-4.7.16.1
   *
   * <pre>
   * element_value {
   *    u1 tag;
   *    union {
   *        u2 const_value_index;
   *
   *        {   u2 type_name_index;
   *            u2 const_name_index;
   *        } enum_const_value;
   *
   *        u2 class_info_index;
   *
   *        annotation annotation_value;
   *
   *        {   u2            num_values;
   *            element_value values[num_values];
   *        } array_value;
   *    } value;
   *}
   *</pre>
   * @since 6.0
   */
  public abstract class ElementValue {
  
      public static final byte STRING = 's';
      public static final byte ENUM_CONSTANT = 'e';
      public static final byte CLASS = 'c';
      public static final byte ANNOTATION = '@';
      public static final byte ARRAY = '[';
      public static final byte PRIMITIVE_INT = 'I';
      public static final byte PRIMITIVE_BYTE = 'B';
      public static final byte PRIMITIVE_CHAR = 'C';
      public static final byte PRIMITIVE_DOUBLE = 'D';
      public static final byte PRIMITIVE_FLOAT = 'F';
      public static final byte PRIMITIVE_LONG = 'J';
      public static final byte PRIMITIVE_SHORT = 'S';
      public static final byte PRIMITIVE_BOOLEAN = 'Z';
      static final ElementValue[] EMPTY_ARRAY = {};
  
      /**
       * Reads an {@code element_value} as an {@code ElementValue}.
       *
       * @param input Raw data input.
       * @param cpool Constant pool.
       * @return a new ElementValue.
       * @throws IOException if an I/O error occurs.
       */
      public static ElementValue readElementValue(final DataInput input, final ConstantPool cpool) throws IOException {
          return readElementValue(input, cpool, 0);
      }
  
      /**
       * Reads an {@code element_value} as an {@code ElementValue}.
       *
       * @param input Raw data input.
       * @param cpool Constant pool.
       * @param arrayNesting level of current array nesting.
       * @return a new ElementValue.
       * @throws IOException if an I/O error occurs.
       * @since 6.7.0
       */
      public static ElementValue readElementValue(final DataInput input, final ConstantPool cpool, int arrayNesting)
              throws IOException {
          final byte tag = input.readByte();
          switch (tag) {
          case PRIMITIVE_BYTE:
          case PRIMITIVE_CHAR:
          case PRIMITIVE_DOUBLE:
          case PRIMITIVE_FLOAT:
         case PRIMITIVE_INT:
         case PRIMITIVE_LONG:
         case PRIMITIVE_SHORT:
         case PRIMITIVE_BOOLEAN:
         case STRING:
             return new SimpleElementValue(tag, input.readUnsignedShort(), cpool);
 
         case ENUM_CONSTANT:
             return new EnumElementValue(ENUM_CONSTANT, input.readUnsignedShort(), input.readUnsignedShort(), cpool);
 
         case CLASS:
             return new ClassElementValue(CLASS, input.readUnsignedShort(), cpool);
 
         case ANNOTATION:
             // TODO isRuntimeVisible
             return new AnnotationElementValue(ANNOTATION, AnnotationEntry.read(input, cpool, false), cpool);
 
         case ARRAY:
             arrayNesting++;
             if (arrayNesting > Const.MAX_ARRAY_DIMENSIONS) {
                 // JVM spec 4.4.1
                 throw new ClassFormatException(String.format("Arrays are only valid if they represent %,d or fewer dimensions.", Const.MAX_ARRAY_DIMENSIONS));
             }
             final int numArrayVals = input.readUnsignedShort();
             final ElementValue[] evalues = new ElementValue[numArrayVals];
             for (int j = 0; j < numArrayVals; j++) {
                 evalues[j] = readElementValue(input, cpool, arrayNesting);
             }
             return new ArrayElementValue(ARRAY, evalues, cpool);
 
         default:
             throw new ClassFormatException("Unexpected element value tag in annotation: " + tag);
         }
     }
 
     /**
      * @deprecated (since 6.0) will be made private and final; do not access directly, use getter
      */
     @java.lang.Deprecated
     protected int type; // TODO should be final
     /**
      * @deprecated (since 6.0) will be made private and final; do not access directly, use getter
      */
     @java.lang.Deprecated
     protected ConstantPool cpool; // TODO should be final
 
     protected ElementValue(final int type, final ConstantPool cpool) {
         this.type = type;
         this.cpool = cpool;
     }
 
     public abstract void dump(DataOutputStream dos) throws IOException;
 
     /** @since 6.0 */
     final ConstantPool getConstantPool() {
         return cpool;
     }
 
     public int getElementValueType() {
         return type;
     }
 
     /** @since 6.0 */
     final int getType() {
         return type;
     }
 
     public abstract String stringifyValue();
 
     public String toShortString() {
         return stringifyValue();
     }
 
     @Override
     public String toString() {
         return stringifyValue();
     }
 }