package com.gxwebsoft.gxmu.service;

import com.gxwebsoft.common.core.exception.BusinessException;
import com.gxwebsoft.gxmu.entity.ReviewFlow;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/**
 * 审批链层级连续性校验（spec #58 行为约定：层级从 1 连续升序）。
 *
 * <p>一条审批链的层级必须恰好是 1..N，缺级会让申报卡在半路，重复级会让两个人拿到同一条待办。
 * 按 title 分组校验，纯函数，不依赖数据库。
 *
 * @author Codex
 * @since 2026-11-03
 */
public final class ReviewFlowLevelValidator {

    private ReviewFlowLevelValidator() {
    }

    /**
     * 校验一组审批流节点的层级；不合法时抛出 {@link BusinessException}。
     *
     * @param flows 同一轮保存涉及的节点，可包含多条审批链（按 title 分组）
     */
    public static void validate(List<ReviewFlow> flows) {
        if (flows == null || flows.isEmpty()) {
            return;
        }
        Map<String, List<Integer>> levelsByTitle = new LinkedHashMap<>();
        for (ReviewFlow flow : flows) {
            if (flow == null) {
                continue;
            }
            levelsByTitle.computeIfAbsent(titleOf(flow), key -> new ArrayList<>()).add(flow.getLevel());
        }
        for (Map.Entry<String, List<Integer>> entry : levelsByTitle.entrySet()) {
            validateOne(entry.getKey(), entry.getValue());
        }
    }

    private static void validateOne(String title, List<Integer> levels) {
        for (Integer level : levels) {
            if (level == null) {
                throw new BusinessException("审批链「" + displayTitle(title) + "」存在未填写层级的节点，层级必须从 1 连续升序");
            }
        }
        List<Integer> sorted = new ArrayList<>(levels);
        Collections.sort(sorted);
        for (int index = 0; index < sorted.size(); index++) {
            if (sorted.get(index) != index + 1) {
                throw new BusinessException("审批链「" + displayTitle(title) + "」的层级必须从 1 连续升序，当前层级为 "
                        + join(sorted) + "，请调整后再保存");
            }
        }
    }

    private static String titleOf(ReviewFlow flow) {
        return flow.getTitle() == null ? "" : flow.getTitle().trim();
    }

    private static String displayTitle(String title) {
        return title.isEmpty() ? "未命名" : title;
    }

    private static String join(List<Integer> levels) {
        StringBuilder builder = new StringBuilder();
        for (int index = 0; index < levels.size(); index++) {
            if (index > 0) {
                builder.append(", ");
            }
            builder.append(levels.get(index));
        }
        return builder.toString();
    }
}