import org.springframework.util.CollectionUtils;
import java.lang.reflect.Field;
import java.sql.Date;
import java.text.NumberFormat;
import java.util.*;
import java.util.stream.Collectors;

/**
 * @author yaoguanquan
 * @creote 2020-08-06-15:36
 */
public class MemoryPagination {

    /**
     * 給list的每個屬性都指定是升序還是降序
     * list元素的屬性可以是數字（byte、short、int、long、float、double等，支援正數、負數、0）、char、String、java.util.Date
     *
     * 
 
@param list 資料集合
     * @param pageNum 第幾頁
     * @param pageSize 每頁多少條
     * @param isSort 是否排序
     * @param sortNameArr  引數陣列
     * @param sortArr      每個屬性對應的升降序陣列， true升序，false降序
     */
    public static <E> List<E> sortMemoryPagination(List<E> list, int pageNum, int pageSize,final
 
 boolean isSort , final String[] sortNameArr, final boolean[] sortArr) {
       if(isSort){
           if (sortNameArr.length != sortArr.length) {
               throw new RuntimeException("屬性陣列元素個數和升降序陣列元素個數不相等");
           }
           Collections.sort(list, new Comparator<E>() {
               
 
public int compare(E a, E b) {
                   int ret = 0;
                   try {
                       for (int i = 0; i < sortNameArr.length; i++) {
                           ret = MemoryPagination.compareObject(sortNameArr[i], sortArr[i], a, b);
                           if (0 != ret) {
                               break;
                           }
                       }
                   } catch (Exception e) {
                       e.printStackTrace();
                   }
                   return ret;
               }
           });

       }
        return pagination(list,pageNum,pageSize);
    }

    /**
     * 記憶體分頁
     *
     * @param records  待分頁的資料
     * @param pageNum  當前頁碼
     * @param pageSize 每頁顯示的條數
     * @return 分頁之後的資料
     */
    private static <T> List<T> pagination(List<T> records, int pageNum, int pageSize) {
        if (CollectionUtils.isEmpty(records)) {
            return Collections.emptyList();
        }
        int totalCount = records.size();
        int remainder = totalCount % pageSize;
        int pageCount = (remainder > 0) ? totalCount/pageSize + 1 : totalCount/pageSize;
        if (remainder == 0) {
            return records.stream().skip((pageNum - 1) * pageSize).limit(pageSize).collect(Collectors.toList());
        } else {
            if (pageNum == pageCount) {
                return records.stream().skip((pageNum - 1) * pageSize).limit(totalCount).collect(Collectors.toList());
            } else {
                return records.stream().skip((pageNum - 1) * pageSize).limit(pageSize).collect(Collectors.toList());
            }
        }
    }

    /**
     * 對2個物件按照指定屬性名稱進行排序
     *
     * @param sortname
     *            屬性名稱
     * @param isAsc
     *            true升序，false降序
     * @param a
     * @param b
     * @return
     * @throws Exception
     */
    private static <E> int compareObject(final String sortname, final boolean isAsc, E a, E b) throws Exception {
        int ret;
        Object value1 = MemoryPagination.forceGetFieldValue(a, sortname);
        Object value2 = MemoryPagination.forceGetFieldValue(b, sortname);
        String str1 = value1.toString();
        String str2 = value2.toString();
        if (value1 instanceof Number && value2 instanceof Number) {
            int maxlen = Math.max(str1.length(), str2.length());
            str1 = MemoryPagination.addZero2Str((Number) value1, maxlen);
            str2 = MemoryPagination.addZero2Str((Number) value2, maxlen);
        } else if (value1 instanceof java.sql.Date && value2 instanceof java.sql.Date) {
            long time1 = ((java.sql.Date) value1).getTime();
            long time2 = ((Date) value2).getTime();
            int maxlen = Long.toString(Math.max(time1, time2)).length();
            str1 = MemoryPagination.addZero2Str(time1, maxlen);
            str2 = MemoryPagination.addZero2Str(time2, maxlen);
        }
        if (isAsc) {
            ret = str1.compareTo(str2);
        } else {
            ret = str2.compareTo(str1);
        }
        return ret;
    }

    /**
     * 獲取指定物件的指定屬性值（去除private,protected的限制）
     *
     * @param obj
     *            屬性名稱所在的物件
     * @param fieldName
     *            屬性名稱
     * @return
     * @throws Exception
     */
    public static Object forceGetFieldValue(Object obj, String fieldName) throws Exception {
        Field field = obj.getClass().getDeclaredField(fieldName);
        Object object = null;
        boolean accessible = field.isAccessible();
        if (!accessible) {
            // 如果是private,protected修飾的屬性，需要修改為可以訪問的
            field.setAccessible(true);
            object = field.get(obj);
            // 還原private,protected屬性的訪問性質
            field.setAccessible(accessible);
            return object;
        }
        object = field.get(obj);
        return object;
    }

    /**
     * 給數字物件按照指定長度在左側補0.
     *
     * 使用案例: addZero2Str(11,4) 返回 "0011", addZero2Str(-18,6)返回 "-000018"
     *
     * @param numObj
     *            數字物件
     * @param length
     *            指定的長度
     * @return
     */
    public static String addZero2Str(Number numObj, int length) {
        NumberFormat nf = NumberFormat.getInstance();
        // 設定是否使用分組
        nf.setGroupingUsed(false);
        // 設定最大整數位數
        nf.setMaximumIntegerDigits(length);
        // 設定最小整數位數
        nf.setMinimumIntegerDigits(length);
        return nf.format(numObj);
    }

    public static void main(String[] args) {
        List<SysDict> list = new ArrayList<>();
        list.add(new SysDict(1,"test1","1",1,3.32));
        list.add(new SysDict(3,"test3","3",3,4.13));
        list.add(new SysDict(2,"test2","11",2,4.11));
        list.add(new SysDict(4,"test4","4",4,23.23));
        list.add(new SysDict(5,"test5","5",5,0.23));
        list.add(new SysDict(6,"test6","22",6,0.23));
        list.add(new SysDict(7,"test7","3",7,0.23));
        list.add(new SysDict(8,"test8","0.2",8,0.23));


        String[] sortnameArr = {"ss","sort"};
        boolean[] typeArr = {true,false};
        List<SysDict> ss = sortMemoryPagination(list, 1, 2, true, sortnameArr,typeArr);
        System.out.println(ss.toString());

    }

}


//class SysDict {
//    private Integer id;
//    private String name;
//    private String value;
//    private Integer sort;
//    private Double ss;
//
//    public SysDict(Integer id, String name, String value, Integer sort,Double ss) {
//        this.id = id;
//        this.name = name;
//        this.value = value;
//        this.sort = sort;
//        this.ss = ss;
//    }
//
//    public Double getSs() {
//        return ss;
//    }
//
//    public void setSs(Double ss) {
//        this.ss = ss;
//    }
//
//    public Integer getId() {
//        return id;
//    }
//
//    public void setId(Integer id) {
//        this.id = id;
//    }
//
//    public String getName() {
//        return name;
//    }
//
//    public void setName(String name) {
//        this.name = name;
//    }
//
//    public String getValue() {
//        return value;
//    }
//
//    public void setValue(String value) {
//        this.value = value;
//    }
//
//    public Integer getSort() {
//        return sort;
//    }
//
//    public void setSort(Integer sort) {
//        this.sort = sort;
//    }
//
//    @Override
//    public String toString() {
//        return "SysDict{" +
//                "id=" + id +
//                ", name='" + name + '\'' +
//                ", value='" + value + '\'' +
//                ", sort=" + sort +
//                ", ss=" + ss +
//                '}';
//    }
//
//}