serene-simple/src/main/java/serene/simple/builtin/Reflector.java

/**
 * Serene (simple) - A PoC lisp to collect data on Serenes concepts
 * Copyright (C) 2019-2020 Sameer Rahmani <lxsameer@gnu.org>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA  02110-1301, USA.
 */
/**
 * I have borrowed the foundations of this namespace from Clojure
 * Which is published under EPL license.
 */

package serene.simple.builtin;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.*;
import java.util.stream.Collectors;
import java.util.ArrayList;

import serene.simple.SereneException;

public class Reflector {
  static Object boxArg(Class<?> paramType, Object arg) {
    if (!paramType.isPrimitive())
      return paramType.cast(arg);
    else if (paramType == boolean.class)
      return Boolean.class.cast(arg);
    else if (paramType == char.class)
      return Character.class.cast(arg);
    else if (arg instanceof Number) {
      Number n = (Number) arg;
      if (paramType == int.class)
        return n.intValue();
      else if (paramType == float.class)
        return n.floatValue();
      else if (paramType == double.class)
        return n.doubleValue();
      else if (paramType == long.class)
        return n.longValue();
      else if (paramType == short.class)
        return n.shortValue();
      else if (paramType == byte.class)
        return n.byteValue();
    }
    throw new IllegalArgumentException(
        "Unexpected param type, expected: " + paramType + ", given: " + arg.getClass().getName());
  }


  static Object[] boxArgs(Class<?>[] params, Object[] args) {
    if (params.length == 0)
      return null;
    Object[] ret = new Object[params.length];
    for (int i = 0; i < params.length; i++) {
      Object arg = args[i];
      Class<?> paramType = params[i];
      ret[i] = boxArg(paramType, arg);
    }
    return ret;
  }

  public static Object invokeConstructor(Class<?> c, Object[] args) {
    try {
      Constructor<?>[] allctors = c.getConstructors();
      ArrayList<Object> ctors = new ArrayList<Object>();

      for (int i = 0; i < allctors.length; i++) {
        Constructor<?> ctor = allctors[i];
        if (ctor.getParameterTypes().length == args.length)
          ctors.add(ctor);
      }
      if (ctors.isEmpty()) {
        throw new IllegalArgumentException("No matching ctor found" + " for " + c);
      } else if (ctors.size() == 1) {
        Constructor<?> ctor = (Constructor<?>) ctors.get(0);
        return ctor.newInstance(boxArgs(ctor.getParameterTypes(), args));
      } else // overloaded w/same arity
      {
        for (Iterator iterator = ctors.iterator(); iterator.hasNext();) {
          Constructor<?> ctor = (Constructor<?>) iterator.next();
          Class<?>[] params = ctor.getParameterTypes();
          if (isCongruent(params, args)) {
            Object[] boxedArgs = boxArgs(params, args);
            return ctor.newInstance(boxedArgs);
          }
        }
        throw new IllegalArgumentException("No matching ctor found" + " for " + c);
      }
    } catch (Exception e) {
      throw new SereneException(
        String.format("Can't intantiate '%s': %s", c.getName(), e.getMessage()));
    }
  }

  static public boolean paramArgTypeMatch(Class<?> paramType, Class<?> argType) {
    if (argType == null)
      return !paramType.isPrimitive();
    if (paramType == argType || paramType.isAssignableFrom(argType))
      return true;
    if (paramType == int.class)
      return argType == Integer.class || argType == long.class || argType == Long.class || argType == short.class
          || argType == byte.class;// || argType == FixNum.class;
    else if (paramType == float.class)
      return argType == Float.class || argType == double.class;
    else if (paramType == double.class)
      return argType == Double.class || argType == float.class;// || argType == DoubleNum.class;
    else if (paramType == long.class)
      return argType == Long.class || argType == int.class || argType == short.class || argType == byte.class;// ||
                                                                                                              // argType
                                                                                                              // ==
                                                                                                              // BigNum.class;
    else if (paramType == char.class)
      return argType == Character.class;
    else if (paramType == short.class)
      return argType == Short.class;
    else if (paramType == byte.class)
      return argType == Byte.class;
    else if (paramType == boolean.class)
      return argType == Boolean.class;
    return false;
  }

  static boolean isCongruent(Class<?>[] params, Object[] args) {
    boolean ret = false;
    if (args == null)
      return params.length == 0;
    if (params.length == args.length) {
      ret = true;
      for (int i = 0; ret && i < params.length; i++) {
        Object arg = args[i];
        Class<?> argType = (arg == null) ? null : arg.getClass();
        Class<?> paramType = params[i];
        ret = paramArgTypeMatch(paramType, argType);
      }
    }
    return ret;
  }

}