/**
 * Copyright (c) 2016, biezhi 王爵 (biezhi.me@gmail.com)
 * <p>
 * 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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 com.blade.kit;

import org.objectweb.asm.*;

import java.io.IOException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

/**
 * ASM Tools
 *
 * @author    <a href="mailto:biezhi.me@gmail.com" target="_blank">biezhi</a>
 * @since 1.6.6
 */
public final class AsmKit {

    /**
     * <p>
     * 比较参数类型是否一致
     * </p>
     *
     * @param types   asm的类型({@link Type})
     * @param clazzes java 类型({@link Class})
     * @return
     */
    private static boolean sameType(Type[] types, Class<?>[] clazzes) {
        // 个数不同
        if (types.length != clazzes.length) {
            return false;
        }
        for (int i = 0; i < types.length; i++) {
            if (!Type.getType(clazzes[i]).equals(types[i])) {
                return false;
            }
        }
        return true;
    }

    /**
     *
     * <p>
     * 获取方法的参数名
     * </p>
     *
     * @param m
     * @return
     */
    public static String[] getMethodParamNames(final Method m) throws IOException {
        final String[] paramNames = new String[m.getParameterTypes().length];
        final String n = m.getDeclaringClass().getName();
        ClassReader cr = null;
        try {
            cr = new ClassReader(n);
        } catch (IOException e) {
            return null;
        }
        cr.accept(new ClassVisitor(Opcodes.ASM5) {
            @Override
            public MethodVisitor visitMethod(final int access, final String name, final String desc,
                                             final String signature, final String[] exceptions) {
                final Type[] args = Type.getArgumentTypes(desc);
                // 方法名相同并且参数个数相同
                if (!name.equals(m.getName()) || !sameType(args, m.getParameterTypes())) {
                    return super.visitMethod(access, name, desc, signature, exceptions);
                }
                MethodVisitor v = super.visitMethod(access, name, desc, signature, exceptions);
                return new MethodVisitor(Opcodes.ASM5, v) {
                    @Override
                    public void visitLocalVariable(String name, String desc, String signature, Label start, Label end,
                                                   int index) {
                        int i = index - 1;
                        // 如果是静态方法，则第一就是参数
                        // 如果不是静态方法，则第一个是"this"，然后才是方法的参数
                        if (Modifier.isStatic(m.getModifiers())) {
                            i = index;
                        }
                        if (i >= 0 && i < paramNames.length) {
                            paramNames[i] = name;
                        }
                        super.visitLocalVariable(name, desc, signature, start, end, index);
                    }
                };
            }
        }, 0);
        return paramNames;
    }

}