package com.walker.etaa.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class AlgorithmUtils {

    private static final Logger logger = LoggerFactory.getLogger(AlgorithmUtils.class);
    private static final Random random = new Random();

    /**
     * 返回给定数据的 HashCode 值集合。
     * @param prefix 字符串前缀，如：math
     * @param indexList 数据记录索引集合，如：[1,3,5,7,...]
     * @return
     * @date 2023-03-08
     */
    public static final List<Integer> getHashCode(String prefix, int[] indexList){
        if(indexList == null || indexList.length == 0){
            return null;
        }
        List<Integer> resultList = new ArrayList<>(indexList.length + 8);
        String s = null;
        for(int i=0; i<indexList.length; i++){
            s = prefix + indexList[i];
            resultList.add(s.hashCode());
        }
        return resultList;
    }

    /**
     * 返回给定范围可用的（随机）数据索引编号集合，如：
     * <pre>
     *     [1,8,5,12,33,...]
     * </pre>
     * @param existTotal
     * @param requiredTotal
     * @return
     */
    public static final int[] getRandomIndexArray(int existTotal, int requiredTotal){
        int span = existTotal / requiredTotal;
        int offset = 1;
        if(span > 1){
            offset = Math.abs(random.nextInt(span));
        } else {
            offset = Math.abs(random.nextInt(requiredTotal-1));
        }
        if(offset >= existTotal || offset <= 0){
            offset = 1;
        }
        int count = 0;
        List<Integer> data = new ArrayList<>();
        while (count < requiredTotal){
            if(offset >= existTotal || offset <= 0){
                offset = Math.abs(random.nextInt(requiredTotal-1));
//                logger.debug("------> offset = {}", offset);
            }
            if(!data.contains(offset)){
//                logger.debug(".......... offset = {}", offset);
                data.add(offset);
//                offset = random.nextInt(requiredTotal-1) + span;
                offset = Math.abs(random.nextInt(existTotal-1)) + span;
                count ++;
                logger.debug("count = {}, offset = {}", count, offset);
            } else {
                // 已有重复了，
//                offset = count + 1;
                offset = Math.abs(random.nextInt(existTotal-1));
                logger.debug("重复了，offset = {}", offset);
            }
        }
        if(data.size() > 0){
            int[] resultList = new int[data.size()];
            for(int i=0; i<data.size(); i++){
                resultList[i] = data.get(i);
            }
            return resultList;
        }
        return null;
    }

    /**
     * 返回给定范围可用的（平均分布）数据索引编号集合，如：
     * <pre>
     *     [1,3,5,7,9,...]
     * </pre>
     * @param existTotal
     * @param requiredTotal
     * @return
     */
    public static final int[] getAverageIndexArray(int existTotal, int requiredTotal){
        int[] result = new int[requiredTotal];
        int span = existTotal / requiredTotal;
        int offset = Math.abs(random.nextInt(10));
        logger.debug("offset = " + offset);
        if(span == 1){
            for(int i=0; i<requiredTotal; i++){
//                System.out.println("get " + (i+1));
                result[i] = i+1;
            }
        } else if(span > 1){
            int current = offset;
            if(current == 0){
                current = 1;
            }

            int last = AlgorithmUtils.getAverageLastIndex(current, span, requiredTotal);
            while(last > existTotal){
                logger.debug("最后元素超过了'existTotal'，last = " + last);
                if(span > 1){
                    span --;
                } else if(offset > 1){
                    offset --;
                } else {
                    logger.warn("已经无法降低抽取间隔了，退出循环");
                    break;
                }
                last = AlgorithmUtils.getAverageLastIndex(current, span, requiredTotal);
            }

            for(int i=0; i<requiredTotal; i++){
                if(i > 0){
                    current += span;
                }
//                System.out.println("get " + (current));
                result[i] = current;
            }
        }
        return result;
    }

    /**
     * 返回平均分布方式抽取时，计算最后元素的索引值（计数值，是否超过题库最大值）
     * @param first 第一个元素索引，从
     * @param span
     * @param requiredTotal
     * @return
     */
    public static final int getAverageLastIndex(int first, int span, int requiredTotal){
        int current = first;
        for(int i=0; i<requiredTotal; i++){
            if(i > 0){
                current += span;
            }
//            System.out.println("get " + (current));
        }
        return current;
    }
}