import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang3.reflect.FieldUtils;

import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.List;

/**
 * 樹形表格工具類
 */
public class TreeTableUtils {

    /**
     * 把列表轉(zhuǎn)換為樹結(jié)構(gòu)
     *
     * @param originalList      原始list數(shù)據(jù)
     * @param idFieldName       作為唯一標(biāo)示的字段名稱
     * @param pidFieldName      父節(jié)點(diǎn)標(biāo)識字段名
     * @param childrenFieldName 子節(jié)點(diǎn)（列表）標(biāo)識字段名
     * @return 樹結(jié)構(gòu)列表
     */
    public static <T> List<T> list2TreeList(List<T> originalList, String idFieldName, String pidFieldName,
                                            String childrenFieldName) {
        // 獲取根節(jié)點(diǎn)，即找出父節(jié)點(diǎn)為空的對象
        List<T> rootNodeList = new ArrayList<>();
        for (T t : originalList) {
            String parentId = null;
            try {
                parentId = BeanUtils.getProperty(t, pidFieldName);
            } catch (IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
                e.printStackTrace();
            }
            if (StringUtils.isBlank(parentId)) {
                rootNodeList.add(0, t);
            }
        }

        // 將根節(jié)點(diǎn)從原始list移除，減少下次處理數(shù)據(jù)
        originalList.removeAll(rootNodeList);

        // 遞歸封裝樹
        try {
            packTree(rootNodeList, originalList, idFieldName, pidFieldName, childrenFieldName);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return rootNodeList;
    }

    /**
     * 封裝樹（向下遞歸）
     *
     * @param parentNodeList    要封裝為樹的父節(jié)點(diǎn)對象集合
     * @param originalList      原始list數(shù)據(jù)
     * @param keyName           作為唯一標(biāo)示的字段名稱
     * @param pidFieldName      父節(jié)點(diǎn)標(biāo)識字段名
     * @param childrenFieldName 子節(jié)點(diǎn)（列表）標(biāo)識字段名
     */
    private static <T> void packTree(List<T> parentNodeList, List<T> originalList, String keyName,
                                     String pidFieldName, String childrenFieldName) throws Exception {
        for (T parentNode : parentNodeList) {
            // 找到當(dāng)前父節(jié)點(diǎn)的子節(jié)點(diǎn)列表
            List<T> children = packChildren(parentNode, originalList, keyName, pidFieldName, childrenFieldName);
            if (children.isEmpty()) {
                continue;
            }

            // 將當(dāng)前父節(jié)點(diǎn)的子節(jié)點(diǎn)從原始list移除，減少下次處理數(shù)據(jù)
            originalList.removeAll(children);

            // 開始下次遞歸
            packTree(children, originalList, keyName, pidFieldName, childrenFieldName);
        }
    }

    /**
     * 封裝子對象
     *
     * @param parentNode        父節(jié)點(diǎn)對象
     * @param originalList      原始list數(shù)據(jù)
     * @param keyName           作為唯一標(biāo)示的字段名稱
     * @param pidFieldName      父節(jié)點(diǎn)標(biāo)識字段名
     * @param childrenFieldName 子節(jié)點(diǎn)（列表）標(biāo)識字段名
     */
    private static <T> List<T> packChildren(T parentNode, List<T> originalList, String keyName, String pidFieldName,
                                            String childrenFieldName) throws Exception {
        // 找到當(dāng)前父節(jié)點(diǎn)下的子節(jié)點(diǎn)列表
        List<T> childNodeList = new ArrayList<>();
        String parentId = BeanUtils.getProperty(parentNode, keyName);
        for (T t : originalList) {
            String childNodeParentId = BeanUtils.getProperty(t, pidFieldName);
            if (parentId.equals(childNodeParentId)) {
                childNodeList.add(t);
            }
        }

        // 將當(dāng)前父節(jié)點(diǎn)下的子節(jié)點(diǎn)列表寫入到當(dāng)前父節(jié)點(diǎn)下（給子節(jié)點(diǎn)列表字段賦值）
        if (!childNodeList.isEmpty()) {
            FieldUtils.writeDeclaredField(parentNode, childrenFieldName, childNodeList, true);
        }

        return childNodeList;
    }
}