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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;

import com.fasterxml.jackson.databind.JsonNode;

import com.redhat.lightblue.util.JsonUtils;

/**
 * Base class for execution step. Each execution step is associated with an
 * execution block. When the step is created, it registers itself with its
 * block. Step contains the getResults api that computes the
 * results of this step, and returns it for processing by the next step.
 *
 */
public abstract class Step {

    protected final ExecutionBlock block;

    public Step(ExecutionBlock block) {
        this.block = block;
        block.registerStep(this);
    }

    /**
     * Compute and return a result stream
     */
    public abstract StepResult getResults(ExecutionContext ctx);

    public abstract JsonNode toJson();

    public void initialize() {
    }

    public JsonNode explain(ExecutionContext ctx) {
        return toJson();
    }

    /**
     * Returns the associated block of this step
     */
    public ExecutionBlock getBlock() {
        return block;
    }

    @Override
    public String toString() {
        return JsonUtils.prettyPrint(toJson());
    }
}