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package com.oracle.js.parser.ir;

import com.oracle.js.parser.ir.visitor.NodeVisitor;
import com.oracle.js.parser.ir.visitor.TranslatorNodeVisitor;

/**
 * A wrapper for an expression that is in a position to be a join predecessor.
 */
public class JoinPredecessorExpression extends Expression {

    private final Expression expression;

    /**
     * A no-arg constructor does not wrap any expression on its own, but can be used as a place to
     * contain a local variable conversion in a place where an expression can otherwise stand.
     */
    public JoinPredecessorExpression() {
        this(null);
    }

    /**
     * A constructor for wrapping an expression and making it a join predecessor. Typically used on
     * true and false subexpressions of the ternary node as well as on the operands of
     * short-circuiting logical expressions {@code &&} and {@code ||}.
     *
     * @param expression the expression to wrap
     */
    public JoinPredecessorExpression(final Expression expression) {
        super(expression == null ? 0L : expression.getToken(), expression == null ? 0 : expression.getStart(), expression == null ? 0 : expression.getFinish());
        this.expression = expression;
    }

    @Override
    public boolean isAlwaysFalse() {
        return expression != null && expression.isAlwaysFalse();
    }

    @Override
    public boolean isAlwaysTrue() {
        return expression != null && expression.isAlwaysTrue();
    }

    /**
     * Returns the underlying expression.
     *
     * @return the underlying expression.
     */
    public Expression getExpression() {
        return expression;
    }

    /**
     * Sets the underlying expression.
     *
     * @param expression the new underlying expression
     * @return this or modified join predecessor expression object.
     */
    public JoinPredecessorExpression setExpression(final Expression expression) {
        if (expression == this.expression) {
            return this;
        }
        return new JoinPredecessorExpression(expression);
    }

    @Override
    public Node accept(final NodeVisitor visitor) {
        if (visitor.enterJoinPredecessorExpression(this)) {
            final Expression expr = getExpression();
            return visitor.leaveJoinPredecessorExpression(expr == null ? this : setExpression((Expression) expr.accept(visitor)));
        }
        return this;
    }

    @Override
    public  R accept(TranslatorNodeVisitor visitor) {
        return visitor.enterJoinPredecessorExpression(this);
    }

    @Override
    public void toString(final StringBuilder sb, final boolean printType) {
        if (expression != null) {
            expression.toString(sb, printType);
        }
    }

}