package com.yunhai.userbase.utils;

import java.util.HashMap;
import java.util.Map;

/**
 * 课程节点 64 bit 复合 ID 工具类（无实体、纯静态）
 * rootType  根节点类别【资源，辅导，题库，试卷，专项】
 * nodeType  虚拟节点类型【根节点，教材（辅）目录节点，年级节点，教材知识树节点，真实节点】
 * stage   学段【2小学 3初中 4高中】
 * grade  年级 1-12
 */

public final class NodeIdUtil {

    /* ===================== 位宽 ===================== */
    private static final int ROOT_BITS  = 4;
    private static final int TYPE_BITS  = 4;   // 原 biz
    private static final int SUBJ_BITS  = 20;
    private static final int STAGE_BITS = 4;
    private static final int GRADE_BITS = 4;
    private static final int NODE_BITS  = 28;

    private static final long ROOT_MASK  = mask(ROOT_BITS);
    private static final long TYPE_MASK  = mask(TYPE_BITS);
    private static final long SUBJ_MASK  = mask(SUBJ_BITS);
    private static final long STAGE_MASK = mask(STAGE_BITS);
    private static final long GRADE_MASK = mask(GRADE_BITS);
    private static final long NODE_MASK  = mask(NODE_BITS);

    /* ===================== 编码 ===================== */
    public static long encode(Integer rootType,
                              String subject,
                              Integer stage,
                              Integer nodeType,
                              Integer grade,
                              Integer nodeId) {
        int subNum = subjectToInt(subject);
        long root  = (rootType == null ? 0 : rootType) & ROOT_MASK;
        long type  = (nodeType == null ? 0 : nodeType) & TYPE_MASK;
        long stageVal = (stage == null ? 0 : stage) & STAGE_MASK;
        long gradeVal = (grade == null ? 0 : grade) & GRADE_MASK;
        long nodeVal  = (nodeId == null ? 0 : nodeId) & NODE_MASK;

        return root  << (TYPE_BITS + SUBJ_BITS + STAGE_BITS + GRADE_BITS + NODE_BITS)
                | type  << (SUBJ_BITS + STAGE_BITS + GRADE_BITS + NODE_BITS)
                | (long) subNum << (STAGE_BITS + GRADE_BITS + NODE_BITS)
                | stageVal << (GRADE_BITS + NODE_BITS)
                | gradeVal << NODE_BITS
                | nodeVal;
    }

    /* ===================== 解码 ===================== */
    public static Map<String, Object> decode(long compositeId) {
        Map<String, Object> map = new HashMap<>(6);
        int root   = (int) ((compositeId >>> (TYPE_BITS + SUBJ_BITS + STAGE_BITS + GRADE_BITS + NODE_BITS)) & ROOT_MASK);
        int type   = (int) ((compositeId >>> (SUBJ_BITS + STAGE_BITS + GRADE_BITS + NODE_BITS)) & TYPE_MASK);
        int subNum = (int) ((compositeId >>> (STAGE_BITS + GRADE_BITS + NODE_BITS)) & SUBJ_MASK);
        int stage  = (int) ((compositeId >>> (GRADE_BITS + NODE_BITS)) & STAGE_MASK);
        int grade  = (int) ((compositeId >>> (NODE_BITS)) & GRADE_MASK);
        int nodeId = (int) (compositeId & NODE_MASK);

        map.put("rootType", root == 0 ? null : root);
        map.put("nodeType", type == 0 ? null : type);
        map.put("subject",  intToSubject(subNum));
        map.put("stage",    stage == 0 ? null : stage);
        map.put("grade",    grade == 0 ? null : grade);
        map.put("nodeId",   nodeId == 0 ? null : nodeId);
        return map;
    }

    /* ===================== subject 工具 ===================== */
    private static int subjectToInt(String subject) {
        if (subject == null || !subject.startsWith("SUB")) return 0;
        return Integer.parseUnsignedInt(subject.substring(3));
    }

    private static String intToSubject(int n) {
        if (n == 0) return null;
        return (n <= 6) ? "SUB0" + n : "SUB" + n;
    }

    private static long mask(int bits) { return (1L << bits) - 1; }

    private NodeIdUtil() {}
}