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package com.oracle.truffle.polyglot;

import com.oracle.truffle.api.CallTarget;
import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.Truffle;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.interop.TruffleObject;
import com.oracle.truffle.api.nodes.RootNode;
import com.oracle.truffle.api.profiles.BranchProfile;
import com.oracle.truffle.polyglot.PolyglotLanguage.ContextProfile;

abstract class HostToGuestRootNode extends RootNode {

    // offset used to indicate where the argument start.
    // first two arguments are language context and receiver.
    protected static final int ARGUMENT_OFFSET = 2;

    @CompilationFinal private boolean seenEnter;
    @CompilationFinal private boolean seenNonEnter;

    @CompilationFinal private volatile ContextProfile profile;

    private final PolyglotEngineImpl engine;
    private final BranchProfile error = BranchProfile.create();

    HostToGuestRootNode() {
        this(null);
    }

    HostToGuestRootNode(PolyglotLanguageContext languageContext) {
        super(languageContext != null ? languageContext.getLanguageInstance().spi : null);
        this.engine = (PolyglotEngineImpl) EngineAccessor.NODES.getPolyglotEngine(this);
        assert this.engine != null : "all host to guest root nodes need to be initialized when entered";
        assert needsEnter() || !needsExceptionWrapping() : "HostToGuestRootNode which does not require enter cannot have exception wrapping.";
    }

    protected abstract Class<?> getReceiverType();

    protected boolean needsEnter() {
        return true;
    }

    protected boolean needsExceptionWrapping() {
        return true;
    }

    @Override
    public final Object execute(VirtualFrame frame) {
        Object[] args = frame.getArguments();
        PolyglotLanguageContext languageContext = profileContext(args[0]);
        PolyglotContextImpl context;
        PolyglotContextImpl prev;
        boolean needsEnter;
        try {
            assert languageContext != null;
            context = languageContext.context;
            needsEnter = needsEnter() && languageContext != null && engine.needsEnter(context);
            if (needsEnter) {
                if (!seenEnter) {
                    CompilerDirectives.transferToInterpreterAndInvalidate();
                    seenEnter = true;
                }
                prev = engine.enter(context);
            } else {
                if (!seenNonEnter) {
                    CompilerDirectives.transferToInterpreterAndInvalidate();
                    seenNonEnter = true;
                }
                prev = null;
            }
        } catch (Throwable e) {
            throw handleException(languageContext, e, false, RuntimeException.class);
        }
        try {
            Object[] arguments = frame.getArguments();
            Object receiver = getReceiverType().cast(arguments[1]);
            Object result;
            result = executeImpl(languageContext, receiver, arguments);
            assert !(result instanceof TruffleObject);
            return result;
        } catch (Throwable e) {
            throw handleException(languageContext, e, needsEnter(), RuntimeException.class);
        } finally {
            if (needsEnter) {
                try {
                    engine.leave(prev, context);
                } catch (Throwable e) {
                    throw handleException(languageContext, e, false, RuntimeException.class);
                }
            }
        }
    }

    @SuppressWarnings({"unchecked", "unused"})
    private <E extends Throwable> E handleException(PolyglotLanguageContext languageContext, Throwable e, boolean entered, Class<E> exceptionType) throws E {
        if (needsExceptionWrapping()) {
            error.enter();
            throw PolyglotImpl.guestToHostException(languageContext, e, entered);
        }
        // no wrapping, just throw
        throw (E) e;
    }

    private PolyglotLanguageContext profileContext(Object languageContext) {
        ContextProfile localProfile = this.profile;
        if (localProfile == null) {
            CompilerDirectives.transferToInterpreterAndInvalidate();
            profile = localProfile = ((PolyglotLanguageContext) languageContext).language.profile;
        }
        return localProfile.profile(languageContext);
    }

    protected abstract Object executeImpl(PolyglotLanguageContext languageContext, Object receiver, Object[] args);

    protected static CallTarget createTarget(HostToGuestRootNode node) {
        return Truffle.getRuntime().createCallTarget(node);
    }

    static <T> T installHostCodeCache(PolyglotLanguageContext languageContext, Object key, T value, Class<T> expectedType) {
        T result = expectedType.cast(languageContext.getLanguageInstance().hostInteropCodeCache.putIfAbsent(key, value));
        if (result != null) {
            return result;
        } else {
            return value;
        }
    }

    static <T> T lookupHostCodeCache(PolyglotLanguageContext languageContext, Object key, Class<T> expectedType) {
        return expectedType.cast(languageContext.getLanguageInstance().hostInteropCodeCache.get(key));
    }

}