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/*
 Copyright 2013 Red Hat, Inc. and/or its affiliates.

 This file is part of lightblue.

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see .
 */
package com.redhat.lightblue.assoc.ep;

/**
 * This class is used to refer to a source step. The source step of another step
 * is sometimes given as a definite step, and sometimes as the result step of an
 * execution block. However, during execution plan construction, not all
 * execution blocks have a result step yet. So, this class defers the
 * initialization of source until it is needed
 */
public final class Source {
    private ExecutionBlock sourceBlock;
    private Step sourceStep;

    public Source(ExecutionBlock sourceBlock) {
        this.sourceBlock = sourceBlock;
    }

    public Source(Step step) {
        this.sourceStep = step;
    }

    public Step getStep() {
        if (sourceStep == null) {
            sourceStep = (Step) sourceBlock.getResultStep();
        }
        return sourceStep;
    }

    public ExecutionBlock getBlock() {
        if (sourceBlock == null) {
            sourceBlock = sourceStep.getBlock();
        }
        return sourceBlock;
    }

    @Override
    public String toString() {
        return "Step:" + getStep() + " block:" + getBlock();
    }
}