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package com.oracle.js.parser.ir;

/**
 * A loop node, for example a while node, do while node or for node
 */
public abstract class LoopNode extends BreakableStatement {
    /** Loop test node, null if infinite */
    protected final JoinPredecessorExpression test;

    /** Loop body */
    protected final Block body;

    /** Can control flow escape from loop, e.g. through breaks or continues to outer loops? */
    protected final boolean controlFlowEscapes;

    /**
     * Constructor
     *
     * @param lineNumber lineNumber
     * @param token token
     * @param finish finish
     * @param body loop body
     * @param test test
     * @param controlFlowEscapes controlFlowEscapes
     */
    protected LoopNode(final int lineNumber, final long token, final int finish, final Block body, final JoinPredecessorExpression test, final boolean controlFlowEscapes) {
        super(lineNumber, token, finish);
        this.body = body;
        this.controlFlowEscapes = controlFlowEscapes;
        this.test = test;
    }

    /**
     * Constructor
     *
     * @param loopNode loop node
     * @param test new test
     * @param body new body
     * @param controlFlowEscapes controlFlowEscapes
     */
    protected LoopNode(final LoopNode loopNode, final JoinPredecessorExpression test, final Block body, final boolean controlFlowEscapes) {
        super(loopNode);
        this.test = test;
        this.body = body;
        this.controlFlowEscapes = controlFlowEscapes;
    }

    @Override
    public boolean isTerminal() {
        if (!mustEnter()) {
            return false;
        }
        // must enter but control flow may escape - then not terminal
        if (controlFlowEscapes) {
            return false;
        }
        // must enter, but body ends with return - then terminal
        if (body.isTerminal()) {
            return true;
        }
        // no breaks or returns, it is still terminal if we can never exit
        return test == null;
    }

    /**
     * Conservative check: does this loop have to be entered?
     *
     * @return true if body will execute at least once
     */
    public abstract boolean mustEnter();

    @Override
    public boolean isLoop() {
        return true;
    }

    /**
     * Get the body for this for node
     *
     * @return the body
     */
    public abstract Block getBody();

    /**
     * @param lc lexical context
     * @param body new body
     * @return new for node if changed or existing if not
     */
    public abstract LoopNode setBody(final LexicalContext lc, final Block body);

    /**
     * Get the test for this for node
     *
     * @return the test
     */
    public final JoinPredecessorExpression getTest() {
        return test;
    }

    /**
     * Set the test for this for node
     *
     * @param lc lexical context
     * @param test new test
     * @return same or new node depending on if test was changed
     */
    public abstract LoopNode setTest(final LexicalContext lc, final JoinPredecessorExpression test);

    /**
     * Set the control flow escapes flag for this node.
     *
     * @param lc lexical context
     * @param controlFlowEscapes control flow escapes value
     * @return new loop node if changed otherwise the same
     */
    public abstract LoopNode setControlFlowEscapes(final LexicalContext lc, final boolean controlFlowEscapes);

    /**
     * Does this loop have a LET declaration and hence require a per-iteration scope?
     *
     * @return true if a per-iteration scope is required.
     */
    public abstract boolean hasPerIterationScope();

    @Override
    public boolean isCompletionValueNeverEmpty() {
        return true;
    }
}