/*
 * 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.verifier.structurals;

/**
 * This class represents a JVM execution frame; that means, a local variable array and an operand stack.
 */

public class Frame {

    /**
     * For instance initialization methods, it is important to remember which instance it is that is not initialized yet. It
     * will be initialized invoking another constructor later. NULL means the instance already *is* initialized.
     *
     * @deprecated Use the getter/setter to access the field as it may be made private in a later release
     */
    @Deprecated
    protected static UninitializedObjectType _this;

    /**
     * Gets the static _this reference.
     *
     * @return the _this.
     * @since 6.0
     */
    public static UninitializedObjectType getThis() {
        return _this;
    }

    /**
     * Sets the static _this reference.
     *
     * @param _this the _this to set.
     * @since 6.0
     */
    public static void setThis(final UninitializedObjectType _this) {
        Frame._this = _this;
    }

    /**
     * The local variables.
     */
    private final LocalVariables locals;

    /**
     * The operand stack.
     */
    private final OperandStack stack;

    /**
     * Constructs a Frame.
     *
     * @param maxLocals the maximum number of local variables.
     * @param maxStack the maximum stack size.
     */
    public Frame(final int maxLocals, final int maxStack) {
        locals = new LocalVariables(maxLocals);
        stack = new OperandStack(maxStack);
    }

    /**
     * Constructs a Frame.
     *
     * @param locals the local variables.
     * @param stack the operand stack.
     */
    public Frame(final LocalVariables locals, final OperandStack stack) {
        this.locals = locals;
        this.stack = stack;
    }

    /**
     * Creates a clone of this frame.
     *
     * @return a clone of this frame.
     */
    @Override
    protected Object clone() {
        return new Frame(locals.getClone(), stack.getClone());
    }

    /**
     * Checks if this frame equals another object.
     *
     * @param o the object to compare.
     * @return true if equal, false otherwise.
     */
    @Override
    public boolean equals(final Object o) {
        if (!(o instanceof Frame)) {
            return false; // implies "null" is non-equal.
        }
        final Frame f = (Frame) o;
        return this.stack.equals(f.stack) && this.locals.equals(f.locals);
    }

    /**
     * Gets a clone of this frame.
     *
     * @return a clone of this frame.
     */
    public Frame getClone() {
        return (Frame) clone();
    }

    /**
     * Gets the local variables.
     *
     * @return the local variables.
     */
    public LocalVariables getLocals() {
        return locals;
    }

    /**
     * Gets the operand stack.
     *
     * @return the operand stack.
     */
    public OperandStack getStack() {
        return stack;
    }

    /**
     * @return a hash code value for the object.
     */
    @Override
    public int hashCode() {
        return stack.hashCode() ^ locals.hashCode();
    }

    /**
     * Returns a String representation of the Frame instance.
     */
    @Override
    public String toString() {
        final StringBuilder s = new StringBuilder("Local Variables:\n");
        s.append(locals);
        s.append("OperandStack:\n");
        s.append(stack);
        return s.toString();
    }
}
