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 * The Universal Permissive License (UPL), Version 1.0
 *
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 * (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
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 * 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.
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 * 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
 * portions of the Software.
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package com.oracle.truffle.js.runtime.interop;

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

import com.oracle.truffle.api.CompilerAsserts;
import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
import com.oracle.truffle.api.frame.Frame;
import com.oracle.truffle.api.frame.FrameDescriptor;
import com.oracle.truffle.api.frame.FrameSlot;
import com.oracle.truffle.api.frame.FrameUtil;
import com.oracle.truffle.api.interop.InteropLibrary;
import com.oracle.truffle.api.interop.InvalidArrayIndexException;
import com.oracle.truffle.api.interop.TruffleObject;
import com.oracle.truffle.api.interop.UnsupportedMessageException;
import com.oracle.truffle.api.library.ExportLibrary;
import com.oracle.truffle.api.library.ExportMessage;
import com.oracle.truffle.api.nodes.BlockNode;
import com.oracle.truffle.api.nodes.Node;
import com.oracle.truffle.api.nodes.NodeVisitor;
import com.oracle.truffle.api.source.SourceSection;
import com.oracle.truffle.js.nodes.FrameDescriptorProvider;
import com.oracle.truffle.js.nodes.JavaScriptNode;
import com.oracle.truffle.js.nodes.access.JSWriteFrameSlotNode;
import com.oracle.truffle.js.nodes.access.ScopeFrameNode;
import com.oracle.truffle.js.nodes.function.JSBuiltin;
import com.oracle.truffle.js.runtime.JSArguments;
import com.oracle.truffle.js.runtime.JSFrameUtil;
import com.oracle.truffle.js.runtime.objects.Dead;

@ExportLibrary(InteropLibrary.class)
final class ScopeMembers implements TruffleObject {

    private final Frame frame;
    
FrameBlockScopeNode or RootNode. /** FrameBlockScopeNode or RootNode. */
    private final Node blockOrRoot;
    private Object[] members;

    ScopeMembers(Frame frame, /* FrameBlockScopeNode or RootNode */ Node blockOrRoot) {
        this.frame = frame;
        this.blockOrRoot = blockOrRoot;
    }

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

    @ExportMessage
    Object readArrayElement(long index) throws InvalidArrayIndexException {
        Object[] allMembers = getAllMembers();
        if (0 <= index && index < allMembers.length) {
            return allMembers[(int) index];
        } else {
            throw InvalidArrayIndexException.create(index);
        }
    }

    @ExportMessage
    long getArraySize() {
        return getAllMembers().length;
    }

    @ExportMessage
    boolean isArrayElementReadable(long index) {
        return 0 <= index && index < getAllMembers().length;
    }

    private Object[] getAllMembers() {
        if (CompilerDirectives.injectBranchProbability(CompilerDirectives.SLOWPATH_PROBABILITY, members == null)) {
            members = collectAllMembers();
        }
        return members;
    }

    @TruffleBoundary
    private Object[] collectAllMembers() {
        List<Object> membersList = new ArrayList<>();
        if (frame == null) {
            Node descNode = blockOrRoot;
            while (descNode != null) {
                if (!(descNode instanceof FrameDescriptorProvider)) {
                    break;
                }
                FrameDescriptor desc = ((FrameDescriptorProvider) descNode).getFrameDescriptor();
                for (FrameSlot slot : desc.getSlots()) {
                    if (JSFrameUtil.isInternal(slot)) {
                        continue;
                    }
                    membersList.add(new Key(slot.getIdentifier().toString(), descNode, slot));
                }

                descNode = JavaScriptNode.findBlockScopeNode(descNode.getParent());
            }
        } else {
            Node descNode = blockOrRoot;
            Frame outerFrame = frame;
            for (;;) { // frameLevel
                Frame outerScope = outerFrame;
                for (;;) { // scopeLevel
                    for (FrameSlot slot : outerScope.getFrameDescriptor().getSlots()) {
                        if (JSFrameUtil.isInternal(slot)) {
                            continue;
                        }
                        if (isUnsetFrameSlot(outerScope, slot)) {
                            continue;
                        }
                        membersList.add(new Key(slot.getIdentifier().toString(), descNode, slot));
                    }

                    FrameSlot parentSlot = outerScope.getFrameDescriptor().findFrameSlot(ScopeFrameNode.PARENT_SCOPE_IDENTIFIER);
                    if (parentSlot == null) {
                        membersList.add(new Key(ScopeVariables.RECEIVER_MEMBER, descNode, null));
                        break;
                    }
                    outerScope = (Frame) FrameUtil.getObjectSafe(outerScope, parentSlot);

                    if (descNode != null) {
                        descNode = JavaScriptNode.findBlockScopeNode(descNode.getParent());
                    }
                }

                outerFrame = JSArguments.getEnclosingFrame(outerFrame.getArguments());
                if (outerFrame == JSFrameUtil.NULL_MATERIALIZED_FRAME) {
                    break;
                }
            }
        }
        return membersList.toArray();
    }

    static boolean isUnsetFrameSlot(Frame frame, FrameSlot slot) {
        if (frame != null && frame.isObject(slot)) {
            Object value = FrameUtil.getObjectSafe(frame, slot);
            if (value == null || value == Dead.instance() || value instanceof Frame) {
                return true;
            }
        }
        return false;
    }

    
Representation of a scope member key with an optional source location.
/**
     * Representation of a scope member key with an optional source location.
     */
    @ExportLibrary(InteropLibrary.class)
    static final class Key implements TruffleObject {

        private final String name;
        private final Node blockOrRoot;
        private final FrameSlot slot;
        private SourceSection sourceLocation;

        Key(String name, Node blockOrRoot, FrameSlot slot) {
            this.name = name;
            this.slot = slot;
            this.blockOrRoot = blockOrRoot;
        }

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

        @ExportMessage
        String asString() {
            return name;
        }

        @Override
        public String toString() {
            return asString();
        }

        @ExportMessage
        @TruffleBoundary
        boolean hasSourceLocation() {
            return getOrFindSourceLocation().isAvailable();
        }

        @ExportMessage
        @TruffleBoundary
        SourceSection getSourceLocation() throws UnsupportedMessageException {
            if (!hasSourceLocation()) {
                throw UnsupportedMessageException.create();
            }
            return sourceLocation;
        }

        private SourceSection getOrFindSourceLocation() {
            CompilerAsserts.neverPartOfCompilation();
            if (sourceLocation == null && blockOrRoot != null) {
                sourceLocation = findSourceLocation();
            }
            if (sourceLocation == null) {
                // unavailable source section
                sourceLocation = JSBuiltin.createSourceSection();
            }
            return sourceLocation;
        }

        private SourceSection findSourceLocation() {
            if (slot != null) {
                class DeclarationFinder implements NodeVisitor {
                    JavaScriptNode found;

                    @Override
                    public boolean visit(Node node) {
                        if (node instanceof JavaScriptNode) {
                            if (node instanceof JSWriteFrameSlotNode) {
                                JSWriteFrameSlotNode write = (JSWriteFrameSlotNode) node;
                                if (write.getFrameSlot() == slot && write.hasSourceSection()) {
                                    found = write;
                                    return false;
                                }
                            }
                            return true;
                        } else if (node == blockOrRoot) {
                            return true;
                        } else if (node instanceof BlockNode) {
                            return true;
                        } else {
                            return false;
                        }
                    }
                }

                DeclarationFinder finder = new DeclarationFinder();
                blockOrRoot.accept(finder);
                if (finder.found != null) {
                    return finder.found.getSourceSection();
                }
            }
            return blockOrRoot.getEncapsulatingSourceSection();
        }
    }
}