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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * The Universal Permissive License (UPL), Version 1.0
 *
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 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
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 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
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 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
 *
 * without restriction, including without limitation the rights to copy, create
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
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package com.oracle.truffle.js.runtime.interop;

import java.util.ArrayList;
import java.util.List;

import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
import com.oracle.truffle.api.dsl.Cached;
import com.oracle.truffle.api.interop.InteropLibrary;
import com.oracle.truffle.api.interop.TruffleObject;
import com.oracle.truffle.api.interop.UnknownIdentifierException;
import com.oracle.truffle.api.interop.UnsupportedMessageException;
import com.oracle.truffle.api.library.CachedLibrary;
import com.oracle.truffle.api.library.ExportLibrary;
import com.oracle.truffle.api.library.ExportMessage;
import com.oracle.truffle.api.object.DynamicObject;
import com.oracle.truffle.api.object.DynamicObjectLibrary;
import com.oracle.truffle.js.nodes.interop.ExportValueNode;
import com.oracle.truffle.js.runtime.objects.Dead;
import com.oracle.truffle.js.runtime.objects.JSProperty;

Wraps a dynamic scope object, filters out dead variables, and prevents const assignment.
/**
 * Wraps a dynamic scope object, filters out dead variables, and prevents const assignment.
 */
@ExportLibrary(InteropLibrary.class)
public final class DynamicScopeWrapper implements TruffleObject {
    final DynamicObject scope;

    public DynamicScopeWrapper(DynamicObject scope) {
        this.scope = scope;
    }

    boolean isConst(String name, DynamicObjectLibrary access) {
        return JSProperty.isConst(access.getProperty(scope, name));
    }

    @SuppressWarnings("static-method")
    @ExportMessage
    boolean hasMembers() {
        return true;
    }

    @ExportMessage
    @TruffleBoundary
    Object getMembers(@SuppressWarnings("unused") boolean includeInternal,
                    @CachedLibrary("this.scope") DynamicObjectLibrary access) {
        List<String> keys = new ArrayList<>();
        for (Object key : access.getKeyArray(scope)) {
            if (key instanceof String) {
                Object value = access.getOrDefault(scope, key, null);
                if (value != null && value != Dead.instance()) {
                    keys.add((String) key);
                }
            }
        }
        return InteropList.create(keys);
    }

    @ExportMessage
    boolean isMemberReadable(String name,
                    @CachedLibrary("this.scope") DynamicObjectLibrary access) {
        Object value = access.getOrDefault(scope, name, null);
        if (value == null || value == Dead.instance()) {
            return false;
        }
        return true;
    }

    @ExportMessage
    boolean isMemberModifiable(String name,
                    @CachedLibrary("this.scope") DynamicObjectLibrary access) {
        return isMemberReadable(name, access) && !isConst(name, access);
    }

    @SuppressWarnings("static-method")
    @ExportMessage
    boolean isMemberInsertable(@SuppressWarnings("unused") String name) {
        return false;
    }

    @ExportMessage
    Object readMember(String name,
                    @CachedLibrary("this.scope") DynamicObjectLibrary access,
                    @Cached ExportValueNode exportValueNode) throws UnknownIdentifierException {
        Object value = access.getOrDefault(scope, name, null);
        if (value == null || value == Dead.instance()) {
            throw UnknownIdentifierException.create(name);
        } else {
            return exportValueNode.execute(value);
        }
    }

    @ExportMessage
    void writeMember(String name, Object value,
                    @CachedLibrary("this.scope") DynamicObjectLibrary access) throws UnsupportedMessageException, UnknownIdentifierException {
        Object curValue = access.getOrDefault(scope, name, null);
        if (curValue == null || curValue == Dead.instance()) {
            throw UnknownIdentifierException.create(name);
        } else if (!isConst(name, access)) {
            access.putIfPresent(scope, name, value);
        } else {
            throw UnsupportedMessageException.create();
        }
    }
}