/*

 * Copyright 1999-2006 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package com.sun.tools.javac.comp;

import com.sun.tools.javac.util.*;

import com.sun.tools.javac.tree.*;

import java.util.Iterator;

import java.util.NoSuchElementException;

/** A class for environments, instances of which are passed as

 *  arguments to tree visitors.  Environments refer to important ancestors

 *  of the subtree that's currently visited, such as the enclosing method,

 *  the enclosing class, or the enclosing toplevel node. They also contain

 *  a generic component, represented as a type parameter, to carry further

 *  information specific to individual passes.

 *

 *  <p><b>This is NOT part of any API supported by Sun Microsystems.  If

 *  you write code that depends on this, you do so at your own risk.

 *  This code and its internal interfaces are subject to change or

 *  deletion without notice.</b>

 */

public class Env<A> implements Iterable<Env<A>> {

    /** The next enclosing environment.

     */

    public Env<A> next;

    /** The environment enclosing the current class.

     */

    public Env<A> outer;

    /** The tree with which this environment is associated.

     */

    public JCTree tree;

    /** The enclosing toplevel tree.

     */

    public JCTree.JCCompilationUnit toplevel;

    /** The next enclosing class definition.

     */

    public JCTree.JCClassDecl enclClass;

    /** The next enclosing method definition.

     */

    public JCTree.JCMethodDecl enclMethod;

    /** A generic field for further information.

     */

    public A info;

    /** Is this an environment for evaluating a base clause?

     */

    public boolean baseClause = false;

    /** Create an outermost environment for a given (toplevel)tree,

     *  with a given info field.

     */

    public Env(JCTree tree, A info) {

        this.next = null;

        this.outer = null;

        this.tree = tree;

        this.toplevel = null;

        this.enclClass = null;

        this.enclMethod = null;

        this.info = info;

    }

    /** Duplicate this environment, updating with given tree and info,

     *  and copying all other fields.

     */

    public Env<A> dup(JCTree tree, A info) {

        return dupto(new Env<A>(tree, info));

    }

    /** Duplicate this environment into a given Environment,

     *  using its tree and info, and copying all other fields.

     */

    public Env<A> dupto(Env<A> that) {

        that.next = this;

        that.outer = this.outer;

        that.toplevel = this.toplevel;

        that.enclClass = this.enclClass;

        that.enclMethod = this.enclMethod;

        return that;

    }

    /** Duplicate this environment, updating with given tree,

     *  and copying all other fields.

     */

    public Env<A> dup(JCTree tree) {

        return dup(tree, this.info);

    }

    /** Return closest enclosing environment which points to a tree with given tag.

     */

    public Env<A> enclosing(int tag) {

        Env<A> env1 = this;

        while (env1 != null && env1.tree.getTag() != tag) env1 = env1.next;

        return env1;

    }

    public String toString() {

        return "Env[" + info + (outer == null ? "" : ",outer=" + outer) + "]";

    }

    public Iterator<Env<A>> iterator() {

        return new Iterator<Env<A>>() {

            Env<A> next = Env.this;

            public boolean hasNext() {

                return next.outer != null;

            }

            public Env<A> next() {

                if (hasNext()) {

                    Env<A> current = next;

                    next = current.outer;

                    return current;

                }

                throw new NoSuchElementException();

            }

            public void remove() {

                throw new UnsupportedOperationException();

            }

        };

    }

}