/*
    * 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.ByteArrayInputStream;
  import java.io.DataInput;
  import java.io.DataOutputStream;
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.util.Objects;
  
  import org.apache.bcel.Const;
  import org.apache.bcel.util.Args;
  
  /**
   * This class is derived from <em>Attribute</em> and represents a reference to a GJ attribute.
   *
   * @see Attribute
   */
  public final class Signature extends Attribute {
  
      /**
       * Extends ByteArrayInputStream to make 'unreading' chars possible.
       */
      private static final class MyByteArrayInputStream extends ByteArrayInputStream {
  
          MyByteArrayInputStream(final String data) {
              super(data.getBytes(StandardCharsets.UTF_8));
          }
  
          String getData() {
              return new String(buf, StandardCharsets.UTF_8);
          }
  
          void unread() {
              if (pos > 0) {
                  pos--;
              }
          }
      }
  
      /**
       * The maximum nesting depth of a signature accepted by {@link #translate(String)}. Guards against a
       * {@link StackOverflowError} from deeply nested, attacker-supplied generic signatures.
       */
      private static final int MAX_NESTING_DEPTH = 512;
  
      private static boolean identStart(final int ch) {
          return ch == 'T' || ch == 'L';
      }
  
      /**
       * Tests if a string is an actual parameter list.
       *
       * @param s The string to test.
       * @return true if the string is an actual parameter list.
       * @since 6.0 is no longer final
       */
      public static boolean isActualParameterList(final String s) {
          return s.startsWith("L") && s.endsWith(">;");
      }
  
      /**
       * Tests if a string is a formal parameter list.
       *
       * @param s The string to test.
       * @return true if the string is a formal parameter list.
       * @since 6.0 is no longer final
       */
      public static boolean isFormalParameterList(final String s) {
          return s.startsWith("<") && s.indexOf(':') > 0;
      }
  
      private static void matchGJIdent(final MyByteArrayInputStream in, final StringBuilder buf) {
          matchGJIdent(in, buf, 0);
      }
  
      private static void matchGJIdent(final MyByteArrayInputStream in, final StringBuilder buf, final int depth) {
          if (depth > MAX_NESTING_DEPTH) {
              throw new IllegalArgumentException("Illegal signature: " + in.getData() + " exceeds maximum nesting depth " + MAX_NESTING_DEPTH);
          }
          int ch;
          matchIdent(in, buf);
         ch = in.read();
         if (ch == '<' || ch == '(') { // Parameterized or method
             // System.out.println("Enter <");
             buf.append((char) ch);
             matchGJIdent(in, buf, depth + 1);
             while ((ch = in.read()) != '>' && ch != ')') { // List of parameters
                 if (ch == -1) {
                     throw new IllegalArgumentException("Illegal signature: " + in.getData() + " reaching EOF");
                 }
                 // System.out.println("Still no >");
                 buf.append(", ");
                 in.unread();
                 matchGJIdent(in, buf, depth + 1); // Recursive call
             }
             // System.out.println("Exit >");
             buf.append((char) ch);
         } else {
             in.unread();
         }
         ch = in.read();
         if (identStart(ch)) {
             in.unread();
             matchGJIdent(in, buf, depth + 1);
         } else if (ch == ')') {
             in.unread();
         } else if (ch != ';') {
             throw new IllegalArgumentException("Illegal signature: " + in.getData() + " read " + (char) ch);
         }
     }
 
     private static void matchIdent(final MyByteArrayInputStream in, final StringBuilder buf) {
         int ch;
         if ((ch = in.read()) == -1) {
             throw new IllegalArgumentException("Illegal signature: " + in.getData() + " no ident, reaching EOF");
         }
         // System.out.println("return from ident:" + (char) ch);
         if (!identStart(ch)) {
             final StringBuilder buf2 = new StringBuilder();
             int count = 1;
             while (Character.isJavaIdentifierPart((char) ch)) {
                 buf2.append((char) ch);
                 count++;
                 ch = in.read();
             }
             if (ch == ':') { // Ok, formal parameter
                 final int skipExpected = "Ljava/lang/Object".length();
                 final long skipActual = in.skip(skipExpected);
                 if (skipActual != skipExpected) {
                     throw new IllegalStateException(String.format("Unexpected skip: expected=%,d, actual=%,d", skipExpected, skipActual));
                 }
                 buf.append(buf2);
                 ch = in.read();
                 in.unread();
                 // System.out.println("so far:" + buf2 + ":next:" +(char) ch);
             } else {
                 for (int i = 0; i < count; i++) {
                     in.unread();
                 }
             }
             return;
         }
         final StringBuilder buf2 = new StringBuilder();
         ch = in.read();
         do {
             buf2.append((char) ch);
             ch = in.read();
             // System.out.println("within ident:"+ (char) ch);
         } while (ch != -1 && (Character.isJavaIdentifierPart((char) ch) || ch == '/'));
         buf.append(Utility.pathToPackage(buf2.toString()));
         // System.out.println("regular return ident:"+ (char) ch + ":" + buf2);
         if (ch != -1) {
             in.unread();
         }
     }
 
     /**
      * Translates a signature string.
      *
      * @param s The signature string.
      * @return The translated signature.
      */
     public static String translate(final String s) {
         // System.out.println("Sig:" + s);
         final StringBuilder buf = new StringBuilder();
         matchGJIdent(new MyByteArrayInputStream(s), buf);
         return buf.toString();
     }
 
     private int signatureIndex;
 
     /**
      * Constructs object from file stream.
      *
      * @param nameIndex Index in constant pool to CONSTANT_Utf8.
      * @param length Content length in bytes.
      * @param input Input stream.
      * @param constantPool Array of constants.
      * @throws IOException Thrown if an I/O error occurs.
      */
     Signature(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
         this(nameIndex, length, input.readUnsignedShort(), constantPool);
     }
 
     /**
      * Constructs a Signature.
      *
      * @param nameIndex Index in constant pool to CONSTANT_Utf8.
      * @param length Content length in bytes.
      * @param signatureIndex Index in constant pool to CONSTANT_Utf8.
      * @param constantPool Array of constants.
      */
     public Signature(final int nameIndex, final int length, final int signatureIndex, final ConstantPool constantPool) {
         super(Const.ATTR_SIGNATURE, nameIndex, Args.require(length, 2, "Signature length attribute"), constantPool);
         this.signatureIndex = signatureIndex;
         // validate:
         Objects.requireNonNull(constantPool.getConstantUtf8(signatureIndex), "constantPool.getConstantUtf8(signatureIndex)");
     }
 
     /**
      * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
      * physical copy.
      *
      * @param c Source to copy.
      */
     public Signature(final Signature c) {
         this(c.getNameIndex(), c.getLength(), c.getSignatureIndex(), c.getConstantPool());
     }
 
     /**
      * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
      * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
      *
      * @param v Visitor object.
      */
     @Override
     public void accept(final Visitor v) {
         // System.err.println("Visiting non-standard Signature object");
         v.visitSignature(this);
     }
 
     /**
      * @return deep copy of this attribute.
      */
     @Override
     public Attribute copy(final ConstantPool constantPool) {
         return (Attribute) clone();
     }
 
     /**
      * Dumps source file attribute to file stream in binary format.
      *
      * @param file Output file stream.
      * @throws IOException Thrown if an I/O error occurs.
      */
     @Override
     public void dump(final DataOutputStream file) throws IOException {
         super.dump(file);
         file.writeShort(signatureIndex);
     }
 
     /**
      * Gets the GJ signature.
      *
      * @return GJ signature.
      */
     public String getSignature() {
         return super.getConstantPool().getConstantUtf8(signatureIndex).getBytes();
     }
 
     /**
      * Gets the signature index.
      *
      * @return Index in constant pool of source file name.
      */
     public int getSignatureIndex() {
         return signatureIndex;
     }
 
     /**
      * Sets the signature index.
      *
      * @param signatureIndex The index info the constant pool of this signature.
      */
     public void setSignatureIndex(final int signatureIndex) {
         this.signatureIndex = signatureIndex;
     }
 
     /**
      * @return String representation.
      */
     @Override
     public String toString() {
         return "Signature: " + getSignature();
     }
 }