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/*
 * @(#)ServiceBootstrap.java	2021-8-20
 *
 * Copyright (c) 2021. All Rights Reserved.
 *
 */

package com.github.javaclub.configcenter.spring.utils;

import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.ServiceLoader;

import org.springframework.core.Ordered;

import com.google.common.collect.Lists;

/**
 * ServiceBootstrap
 *
 * @author Gerald Chen
 * @version $Id: ServiceBootstrap.java 2021-8-20 14:30:54 Exp $
 */
public class ServiceBootstrap {

	public static  S loadFirst(Class clazz) {
	    Iterator iterator = loadAll(clazz);
	    if (!iterator.hasNext()) {
	      throw new IllegalStateException(String.format(
	          "No implementation defined in /META-INF/services/%s, please check whether the file exists and has the right implementation class!",
	          clazz.getName()));
	    }
	    return iterator.next();
	  }

	  public static  Iterator loadAll(Class clazz) {
	    ServiceLoader loader = ServiceLoader.load(clazz);

	    return loader.iterator();
	  }

	  public static  List loadAllOrdered(Class clazz) {
	    Iterator iterator = loadAll(clazz);

	    if (!iterator.hasNext()) {
	      throw new IllegalStateException(String.format(
	          "No implementation defined in /META-INF/services/%s, please check whether the file exists and has the right implementation class!",
	          clazz.getName()));
	    }

	    List candidates = Lists.newArrayList(iterator);
	    Collections.sort(candidates, new Comparator() {
	      @Override
	      public int compare(S o1, S o2) {
	        // the smaller order has higher priority
	        return Integer.compare(o1.getOrder(), o2.getOrder());
	      }
	    });

	    return candidates;
	  }

	  public static  S loadPrimary(Class clazz) {
	    List candidates = loadAllOrdered(clazz);

	    return candidates.get(0);
	  }

}