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 * (a) the Software, and
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package com.oracle.truffle.js.nodes.control;

import java.util.ArrayList;
import java.util.Arrays;

import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.nodes.BlockNode;
import com.oracle.truffle.js.nodes.JSNodeUtil;
import com.oracle.truffle.js.nodes.JavaScriptNode;
import com.oracle.truffle.js.nodes.access.JSConstantNode.JSConstantUndefinedNode;
import com.oracle.truffle.js.nodes.binary.DualNode;

public abstract class AbstractBlockNode extends StatementNode implements SequenceNode, BlockNode.ElementExecutor {
    @Child protected BlockNode block;

    @SuppressWarnings("this-escape")
    protected AbstractBlockNode(JavaScriptNode[] statements) {
        this.block = BlockNode.create(statements, this);
    }

    @Override
    public final JavaScriptNode[] getStatements() {
        return block.getElements();
    }

    @Override
    public void executeVoid(VirtualFrame frame) {
        block.executeVoid(frame, BlockNode.NO_ARGUMENT);
    }

    @Override
    public Object execute(VirtualFrame frame) {
        return block.executeGeneric(frame, BlockNode.NO_ARGUMENT);
    }

    @Override
    public void executeVoid(VirtualFrame frame, JavaScriptNode node, int index, int argument) {
        node.executeVoid(frame);
    }

    @Override
    public Object executeGeneric(VirtualFrame frame, JavaScriptNode node, int index, int argument) {
        return node.execute(frame);
    }

    /**
     * Filter out empty statements, unwrap void nodes, and inline block nodes.
     *
     * If creating an expression block, for the last statement, only inline expression block nodes.
     */
    protected static JavaScriptNode filterStatements(JavaScriptNode[] originalStatements, boolean exprBlock) {
        ArrayList filteredStatements = null;
        boolean returnExprBlock = exprBlock;
        for (int i = 0; i < originalStatements.length; i++) {
            JavaScriptNode statement = originalStatements[i];
            if ((statement instanceof EmptyNode ||
                            statement instanceof AbstractBlockNode ||
                            statement instanceof DualNode ||
                            statement instanceof DiscardResultNode ||
                            statement instanceof JSConstantUndefinedNode) &&
                            !JSNodeUtil.hasImportantTag(statement)) {
                if (filteredStatements == null) {
                    filteredStatements = newListFromRange(originalStatements, 0, i);
                }
                if (statement instanceof AbstractBlockNode) {
                    filteredStatements.addAll(Arrays.asList(((AbstractBlockNode) statement).getStatements()));
                } else if (statement instanceof DualNode) {
                    DualNode dualNode = (DualNode) statement;
                    filteredStatements.add(dualNode.getLeft());
                    filteredStatements.add(dualNode.getRight());
                } else if (statement instanceof DiscardResultNode) {
                    DiscardResultNode voidNode = (DiscardResultNode) statement;
                    filteredStatements.add(voidNode.getOperand());
                    transferSourceSectionAndTags(statement, voidNode.getOperand());
                } else {
                    assert statement instanceof EmptyNode || statement instanceof JSConstantUndefinedNode;
                }
                if (exprBlock && i == originalStatements.length - 1 &&
                                !(statement instanceof ExprBlockNode || statement instanceof DualNode || statement instanceof EmptyNode)) {
                    // last statement would have returned undefined, so we need a void block node
                    returnExprBlock = false;
                }
            } else {
                if (filteredStatements != null) {
                    filteredStatements.add(statement);
                }
            }
        }

        JavaScriptNode[] finalStatements = filteredStatements == null ? originalStatements : filteredStatements.toArray(new JavaScriptNode[filteredStatements.size()]);

        if (returnExprBlock) {
            if (finalStatements.length == 0) {
                return EmptyNode.create();
            } else if (finalStatements.length == 1) {
                return finalStatements[0];
            } else if (finalStatements.length == 2) {
                return DualNode.create(finalStatements[0], finalStatements[1]);
            } else {
                return new ExprBlockNode(finalStatements);
            }
        } else {
            if (finalStatements.length == 0) {
                return EmptyNode.create();
            } else if (finalStatements.length == 1) {
                return DiscardResultNode.create(finalStatements[0]);
            } else {
                return new VoidBlockNode(finalStatements);
            }
        }
    }

    protected static ArrayList newListFromRange(JavaScriptNode[] statements, int from, int to) {
        return new ArrayList<>(Arrays.asList(statements).subList(from, to));
    }
}