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/*
* Copyright (c) 2013-2016 GraphAware
*
* This file is part of the GraphAware Framework.
*
* GraphAware Framework 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.graphaware.reco.generic.engine;
import com.graphaware.reco.generic.context.Context;
import com.graphaware.reco.generic.result.Recommendations;
/**
* A {@link RecommendationEngine} that reads pre-computed recommendations and their scores from an external source.
*
* {@link com.graphaware.reco.generic.context.Context#allow(Object, String)} is still consulted filter out recommendations
* for which the situation has changed since they were pre-computed.
*
* Once a pre-computed recommendation has been read, it is disallowed by calling {@link com.graphaware.reco.generic.context.Context#disallow(Object)}
* so that other recommendation engines do not discover it again.
*
* @param type of the precomputed recommendation source. Could be an object from cache, a graph relationship, etc.
*/
public abstract class PrecomputedEngine extends BaseRecommendationEngine {
/**
* {@inheritDoc}
*/
@Override
public String name() {
return "Precomputed Engine @" + this.hashCode();
}
/**
* {@inheritDoc}
*/
@Override
public Recommendations doRecommend(IN input, Context context) {
Recommendations result = new Recommendations<>();
for (SOURCE source : produce(input)) {
OUT recommendation = extract(source);
if (context.allow(recommendation, name())) {
addToResult(result, recommendation, source);
context.disallow(recommendation);
}
}
return result;
}
/**
* Produce pre-computed recommendation sources.
*
* @param input for which to read pre-computed recommendations.
* @return sources.
*/
protected abstract Iterable produce(IN input);
/**
* Extract a recommendation out of a source.
*
* @param source to extract a recommendation from.
* @return recommendation.
*/
protected abstract OUT extract(SOURCE source);
/**
* Add a recommendation to the overall recommendations.
*
* @param recommendations to add to.
* @param recommendation to add.
* @param source source of the recommendation.
*/
protected abstract void addToResult(Recommendations recommendations, OUT recommendation, SOURCE source);
}
