/*
 * 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
 *
 *     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.jdo.tck.util.signature;

import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/** A helper class for translating between Java user type names and reflection type names. */
public class TypeHelper {
  /** Error message for format errors with a user type name. */
  private static final String MSG_ILLEGAL_USR_TYPE = "illegal user type name: ";

  /** Error message for format errors with a reflection type name. */
  private static final String MSG_ILLEGAL_RFL_TYPE = "illegal reflection type name: ";

  /** Throws an IllegalArgumentException if a given condition is violated. */
  private static void check(boolean cond, String msg) {
    if (!cond) throw new IllegalArgumentException(msg);
  }

  /** Maps primitive reflection type names to (Java) user names. */
  private static final Map<String, String> userTypeNames = new HashMap<>();

  /** Maps primitive (Java) user type names to reflection names. */
  private static final Map<String, String> reflectionTypeNames = new HashMap<>();

  /** Maps primitive type names to class objects. */
  private static final Map<String, Class<?>> primitiveClasses = new HashMap<>();

  // initializes the type maps
  static {
    userTypeNames.put("B", "byte");
    userTypeNames.put("C", "char");
    userTypeNames.put("D", "double");
    userTypeNames.put("F", "float");
    userTypeNames.put("I", "int");
    userTypeNames.put("J", "long");
    userTypeNames.put("S", "short");
    userTypeNames.put("Z", "boolean");
    userTypeNames.put("V", "void");

    for (final Map.Entry<String, String> e : userTypeNames.entrySet()) {
      reflectionTypeNames.put(e.getValue(), e.getKey());
    }

    primitiveClasses.put("byte", byte.class);
    primitiveClasses.put("char", char.class);
    primitiveClasses.put("double", double.class);
    primitiveClasses.put("float", float.class);
    primitiveClasses.put("int", int.class);
    primitiveClasses.put("long", long.class);
    primitiveClasses.put("short", short.class);
    primitiveClasses.put("boolean", boolean.class);
    primitiveClasses.put("void", void.class);
  }

  /**
   * Returns the (Java) user name for a reflection type name.
   *
   * @param name typed name
   * @return user name for a reflection type name
   */
  public static String userTypeName(String name) {
    check(name != null, MSG_ILLEGAL_RFL_TYPE + name);

    // count array dimensions from start
    final int n = name.length();
    check(n > 0, MSG_ILLEGAL_RFL_TYPE + name);
    int i = 0;
    final StringBuilder sb = new StringBuilder();
    while (name.charAt(i) == '[') {
      sb.append("[]");
      i++;
      check(i < n, MSG_ILLEGAL_RFL_TYPE + name);
    }

    // no translation of primitive type names if not an array type
    if (i == 0) {
      return name;
    }

    // translate and recompose name
    final String s;
    if (name.charAt(i) == 'L') {
      check(name.endsWith(";"), MSG_ILLEGAL_RFL_TYPE + name);
      s = name.substring(i + 1, n - 1);
    } else {
      s = userTypeNames.get(name.substring(i));
      check(s != null, MSG_ILLEGAL_RFL_TYPE + name);
    }
    return (s + sb);
  }

  /**
   * Returns the (Java) user names for reflection type names.
   *
   * @param names type names
   * @return the (Java) user names for reflection type names.
   */
  public static String[] userTypeNames(String[] names) {
    final String[] u = new String[names.length];
    for (int i = names.length - 1; i >= 0; i--) {
      u[i] = userTypeName(names[i]);
    }
    return u;
  }

  /**
   * Returns the reflection name for a (Java) user type name.
   *
   * @param name type name
   * @return reflection name for a (Java) user type name
   */
  public static String reflectionTypeName(String name) {
    check(name != null, MSG_ILLEGAL_USR_TYPE + name);

    // count array dimensions from end
    final int n = name.length();
    check(n > 0, MSG_ILLEGAL_USR_TYPE + name);
    int i = n - 1;
    final StringBuilder sb = new StringBuilder();
    while (name.charAt(i) == ']') {
      i--;
      check(name.charAt(i) == '[', MSG_ILLEGAL_USR_TYPE + name);
      sb.append("[");
      i--;
      check(i >= 0, MSG_ILLEGAL_USR_TYPE + name);
    }

    // no translation of primitive type names if not an array type
    if (++i == n) {
      return name;
    }

    // translate and recompose name
    final String s = name.substring(0, i);
    final String p = reflectionTypeNames.get(s);
    return sb.append(p != null ? p : "L" + s + ";").toString();
  }

  /**
   * Returns the (Java) user names for reflection type names.
   *
   * @param names type names
   * @return the (Java) user names for reflection type names.
   */
  public static String[] reflectionTypeNames(String[] names) {
    final String[] r = new String[names.length];
    for (int i = names.length - 1; i >= 0; i--) {
      r[i] = reflectionTypeName(names[i]);
    }
    return r;
  }

  /**
   * Returns the class object for a primitive type name, or <code>null</code> if the name does not
   * denote a primitive type (class objects of primitive types cannot be loaded with reflection).
   *
   * @param name type name
   * @return class object
   */
  public static Class<?> primitiveClass(String name) {
    return primitiveClasses.get(name);
  }

  /**
   * Tests if a name denotes a primitive type.
   *
   * @param name type name
   * @return true if a name denotes a primitive type.
   */
  public static boolean isPrimitive(String name) {
    return primitiveClasses.containsKey(name);
  }

  /**
   * Returns the component type name of a (Java) user type name.
   *
   * @param name type name
   * @return component type name of a (Java) user type name
   */
  public static String componentUserTypeName(String name) {
    check(name != null, MSG_ILLEGAL_USR_TYPE + name);
    final int n = name.length();
    check(n > 0, MSG_ILLEGAL_USR_TYPE + name);
    final int i = name.indexOf('[');
    if (i >= 0) {
      check(i > 0, MSG_ILLEGAL_USR_TYPE + name);
      name = name.substring(0, i);
    }
    return name;
  }

  /**
   * Returns the <code>java.lang.</code>-qualified name for a given unqualified (Java) user type
   * name.
   *
   * @param name type name
   * @return qualified name
   */
  public static String qualifiedUserTypeName(String name) {
    final String c = componentUserTypeName(name);
    return ((isPrimitive(c) || c.indexOf('.') >= 0) ? name : "java.lang." + name);
  }

  /**
   * Returns the <code>java.lang.</code>-qualified names for given unqualified (Java) user type
   * names.
   *
   * @param names type names
   * @return qualified name
   */
  public static String[] qualifiedUserTypeNames(String[] names) {
    final String[] q = new String[names.length];
    for (int i = names.length - 1; i >= 0; i--) {
      q[i] = qualifiedUserTypeName(names[i]);
    }
    return q;
  }

  /**
   * Compares a type name with a class objects for equality in the name.
   *
   * @param userTypeName type name
   * @param cls class object
   * @return true if name matches
   */
  public static boolean isNameMatch(String userTypeName, Class<?> cls) {
    final String c = (cls == null ? null : userTypeName(cls.getName()));
    return (userTypeName == null ? (c == null) : userTypeName.equals(c));
  }

  /**
   * Compares an array of type names with an array of class objects for set-equality in the names
   * (i.e., ignoring order).
   *
   * @param userTypeName type names
   * @param cls class objects
   * @return true if names matches
   */
  public static boolean isNameMatch(String[] userTypeName, Class<?>[] cls) {
    final Set<String> s = new HashSet<>(Arrays.asList(userTypeName));
    for (int i = cls.length - 1; i >= 0; i--) {
      if (!s.remove(userTypeName(cls[i].getName()))) {
        return false;
      }
    }
    return s.isEmpty();
  }
}