/*
 * This file is part of LanternServer, licensed under the MIT License (MIT).
 *
 * Copyright (c) LanternPowered <https://www.lanternpowered.org>
 * Copyright (c) SpongePowered <https://www.spongepowered.org>
 * Copyright (c) contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the Software), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package org.lanternpowered.server.event.filter.delegate;

import static org.objectweb.asm.Opcodes.ACONST_NULL;
import static org.objectweb.asm.Opcodes.ALOAD;
import static org.objectweb.asm.Opcodes.ARETURN;
import static org.objectweb.asm.Opcodes.CHECKCAST;
import static org.objectweb.asm.Opcodes.IFEQ;
import static org.objectweb.asm.Opcodes.IFNE;
import static org.objectweb.asm.Opcodes.INVOKEINTERFACE;

import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Type;
import org.spongepowered.api.event.Cancellable;
import org.spongepowered.api.util.Tristate;

import java.lang.reflect.Method;

public class CancellationEventFilterDelegate implements FilterDelegate {

    private final Tristate state;

    public CancellationEventFilterDelegate(Tristate state) {
        this.state = state;
    }

    @Override
    public int write(String name, ClassWriter cw, MethodVisitor mv, Method method, int locals) {
        if (!Cancellable.class.isAssignableFrom(method.getParameters()[0].getType())) {
            throw new IllegalStateException("Attempted to filter a non-cancellable event type by its cancellation status");
        }
        if (this.state == Tristate.UNDEFINED) {
            return locals;
        }
        mv.visitVarInsn(ALOAD, 1);
        mv.visitTypeInsn(CHECKCAST, Type.getInternalName(Cancellable.class));
        mv.visitMethodInsn(INVOKEINTERFACE, Type.getInternalName(Cancellable.class), "isCancelled", "()Z", true);
        Label success = new Label();
        if (this.state == Tristate.TRUE) {
            mv.visitJumpInsn(IFNE, success);
        } else {
            mv.visitJumpInsn(IFEQ, success);
        }
        mv.visitInsn(ACONST_NULL);
        mv.visitInsn(ARETURN);
        mv.visitLabel(success);
        return locals;
    }

}