/*

 * Copyright (c) 2017, Oracle and/or its affiliates. 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.  Oracle designates this

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

 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package com.sun.tools.javac.code;

import java.util.Map;

import java.util.WeakHashMap;

import com.sun.tools.javac.code.Kinds.Kind;

import com.sun.tools.javac.code.Scope.WriteableScope;

import com.sun.tools.javac.code.Symbol;

import com.sun.tools.javac.code.Symbol.ClassSymbol;

import com.sun.tools.javac.code.Symbol.Completer;

import com.sun.tools.javac.code.Symbol.CompletionFailure;

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

/** When a CompletionFailure is thrown when user code is running, it shouldn't be

 *  thrown out to the client code, but rather skipped, and then rethrown later if javac

 *  itself will complete the Symbol.

 *

 *  On all places where javac invokes client code (e.g. TaskListeners, annotation

 *  Processors), the {@code userCodeHandler} should be set using

 *  {@link DeferredCompletionFailureHandler#setHandler}, and the original handler

 *  should be restored when the control returns back to javac.

 *

 *  Implementations of API methods should use {@link Symbol#apiComplete()} instead of

 *  {@link Symbol#complete}, as the {@code apiComplete} method will invoke

 *  {@link DeferredCompletionFailureHandler#handleAPICompletionFailure }, which will

 *  catch the CompletionFailure and will either rethrow it or skip it, depending on

 *  the context.

 */

public class DeferredCompletionFailureHandler {

    protected static final Context.Key<DeferredCompletionFailureHandler> deferredCompletionFailureHandlerKey = new Context.Key<>();

    public static DeferredCompletionFailureHandler instance(Context context) {

        DeferredCompletionFailureHandler instance = context.get(deferredCompletionFailureHandlerKey);

        if (instance == null)

            instance = new DeferredCompletionFailureHandler(context);

        return instance;

    }

    public final Handler userCodeHandler = new Handler() {

        private final Map<ClassSymbol, FlipSymbolDescription> class2Flip = new WeakHashMap<>();

        public void install() {

            class2Flip.values().forEach(f -> f.flip());

        }

        public void handleAPICompletionFailure(CompletionFailure cf) {

            //ignore

        }

        public void classSymbolCompleteFailed(ClassSymbol sym, Completer origCompleter) {

            class2Flip.put(sym, new FlipSymbolDescription(sym, new DeferredCompleter(origCompleter) {

                @Override public void complete(Symbol sym) throws CompletionFailure {

                    class2Flip.remove(sym);

                    super.complete(sym);

                }

            }));

        }

        public void uninstall() {

            class2Flip.values().forEach(f -> f.flip());

        }

    };

    public final Handler javacCodeHandler = new Handler() {

        public void install() {

        }

        public void handleAPICompletionFailure(CompletionFailure cf) {

            throw cf;

        }

        public void classSymbolCompleteFailed(ClassSymbol sym, Completer origCompleter) {}

        public void uninstall() {

        }

    };

    private Handler handler = javacCodeHandler;

    protected DeferredCompletionFailureHandler(Context context) {

        context.put(deferredCompletionFailureHandlerKey, this);

    }

    public Handler setHandler(Handler h) {

        if (h == handler) return handler;

        handler.uninstall();

        Handler prev = handler;

        handler = h;

        handler.install();

        return prev;

    }

    public void handleAPICompletionFailure(CompletionFailure cf) {

        handler.handleAPICompletionFailure(cf);

    }

    public void classSymbolCompleteFailed(ClassSymbol sym, Completer origCompleter) {

        handler.classSymbolCompleteFailed(sym, origCompleter);

    }

    public boolean isDeferredCompleter(Completer c) {

        return c instanceof DeferredCompleter;

    }

    public interface Handler {

        public void install();

        public void handleAPICompletionFailure(CompletionFailure cf);

        public void classSymbolCompleteFailed(ClassSymbol sym, Completer origCompleter);

        public void uninstall();

    }

    private class DeferredCompleter implements Completer {

        private final Completer origCompleter;

        public DeferredCompleter(Completer origCompleter) {

            this.origCompleter = origCompleter;

        }

        @Override

        public void complete(Symbol sym) throws CompletionFailure {

            origCompleter.complete(sym);

        }

    }

    private static class FlipSymbolDescription {

        public final ClassSymbol sym;

        public Type type;

        public Kind kind;

        public WriteableScope members;

        public Completer completer;

        public FlipSymbolDescription(ClassSymbol sym, Completer completer) {

            this.sym = sym;

            this.type = sym.type;

            this.kind = sym.kind;

            this.members = null;

            this.completer = completer;

        }

        public void flip() {

            Type prevType = sym.type;

            sym.type = type;

            this.type = prevType;

            Kind prevKind = sym.kind;

            sym.kind = kind;

            this.kind = prevKind;

            Completer prevCompleter = sym.completer;

            sym.completer = completer;

            this.completer = prevCompleter;

            WriteableScope prevMembers = sym.members_field;

            sym.members_field = members;

            this.members = prevMembers;

        }

    }

}