/*
 * 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
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 */
package com.sun.tools.javac.code;

import java.util.HashMap;
import java.util.Map;

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 userCodeHandler should be set using setHandler, and the original handler should be restored when the control returns back to javac. Implementations of API methods should use Symbol.apiComplete() instead of Symbol.complete, as the apiComplete method will invoke handleAPICompletionFailure, which will catch the CompletionFailure and will either rethrow it or skip it, depending on the 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 HashMap<>();

        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 classSymbolRemoved(ClassSymbol sym) {
            class2Flip.remove(sym);
        }
        public void uninstall() {
            class2Flip.values().forEach(f -> f.flip());
        }
    };

    public final Handler speculativeCodeHandler = new Handler() {
        private final Map<ClassSymbol, FlipSymbolDescription> class2Flip = new HashMap<>();

        public void install() {
        }
        public void handleAPICompletionFailure(CompletionFailure cf) {
            throw cf;
        }
        public void classSymbolCompleteFailed(ClassSymbol sym, Completer origCompleter) {
            class2Flip.put(sym, new FlipSymbolDescription(sym, new DeferredCompleter(origCompleter)));
        }
        public void classSymbolRemoved(ClassSymbol sym) {
            class2Flip.remove(sym);
        }
        public void uninstall() {
            class2Flip.values().forEach(f -> f.flip());
            class2Flip.clear();
        }
    };

    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 classSymbolRemoved(ClassSymbol sym) {}
        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 void classSymbolRemoved(ClassSymbol sym) {
        handler.classSymbolRemoved(sym);
    }

    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 classSymbolRemoved(ClassSymbol sym);
        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;
        }

    }
}