/**
 * NAC知识引擎 — 规则版本管理模块 (v15)
 *
 * 功能：
 * 1. 规则更新时自动保存历史版本快照
 * 2. 查询规则的版本历史列表
 * 3. 对比两个版本的差异（字段级别diff）
 * 4. 版本回滚（管理员权限）
 */

import { getMongoDb, COLLECTIONS } from "./mongodb";
import { ObjectId } from "mongodb";

// ─── 类型定义 ──────────────────────────────────────────────────────
export interface RuleVersion {
  _id?: ObjectId;
  ruleId: string;           // 原始规则ID
  version: number;          // 版本号（从1开始递增）
  snapshot: Record<string, unknown>;  // 规则完整快照
  changedFields: string[];  // 本次变更的字段列表
  changeSummary: string;    // 变更摘要（中文描述）
  operatorId: number;       // 操作人ID
  operatorEmail: string;    // 操作人邮箱
  createdAt: Date;
}

export interface FieldDiff {
  field: string;
  label: string;
  oldValue: unknown;
  newValue: unknown;
  changeType: "added" | "removed" | "modified";
}

// ─── 字段中文标签映射 ─────────────────────────────────────────────
const FIELD_LABELS: Record<string, string> = {
  ruleName: "规则名称",
  description: "规则描述",
  jurisdiction: "司法辖区",
  assetType: "资产类型",
  status: "状态",
  required: "强制要求",
  tags: "标签",
  ruleNameI18n: "多语言名称",
  descriptionI18n: "多语言描述",
};

// ─── 生成变更摘要 ──────────────────────────────────────────────────
function buildChangeSummary(changedFields: string[]): string {
  if (changedFields.length === 0) return "无变更";
  const labels = changedFields.map(f => FIELD_LABELS[f] || f);
  if (labels.length === 1) return `更新了${labels[0]}`;
  if (labels.length <= 3) return `更新了${labels.join("、")}`;
  return `更新了${labels.slice(0, 2).join("、")}等${labels.length}个字段`;
}

// ─── 比较两个值是否相等（深度比较） ──────────────────────────────
function deepEqual(a: unknown, b: unknown): boolean {
  if (a === b) return true;
  if (typeof a !== typeof b) return false;
  if (a === null || b === null) return false;
  if (typeof a === "object") {
    return JSON.stringify(a) === JSON.stringify(b);
  }
  return false;
}

// ─── 保存版本快照（规则更新时调用） ──────────────────────────────
export async function saveRuleVersion(
  ruleId: string,
  oldSnapshot: Record<string, unknown>,
  updatedFields: Record<string, unknown>,
  operatorId: number,
  operatorEmail: string
): Promise<number> {
  const db = await getMongoDb();
  if (!db) return 0;

  // 计算变更字段
  const changedFields = Object.keys(updatedFields).filter(key => {
    if (key === "updatedAt" || key === "_embeddingUpdatedAt" || key === "_embedding") return false;
    return !deepEqual(oldSnapshot[key], updatedFields[key]);
  });

  if (changedFields.length === 0) return 0; // 无实质变更，不保存

  // 获取当前最大版本号
  const lastVersion = await db.collection(COLLECTIONS.RULE_VERSIONS)
    .find({ ruleId })
    .sort({ version: -1 })
    .limit(1)
    .toArray() as any[];

  const nextVersion = (lastVersion[0]?.version || 0) + 1;

  const versionDoc: RuleVersion = {
    ruleId,
    version: nextVersion,
    snapshot: { ...oldSnapshot },
    changedFields,
    changeSummary: buildChangeSummary(changedFields),
    operatorId,
    operatorEmail,
    createdAt: new Date(),
  };

  await db.collection(COLLECTIONS.RULE_VERSIONS).insertOne(versionDoc);
  return nextVersion;
}

// ─── 查询规则版本历史 ──────────────────────────────────────────────
export async function getRuleVersionHistory(
  ruleId: string,
  limit = 20
): Promise<RuleVersion[]> {
  const db = await getMongoDb();
  if (!db) return [];

  const docs = await db.collection(COLLECTIONS.RULE_VERSIONS)
    .find({ ruleId })
    .sort({ version: -1 })
    .limit(limit)
    .toArray();
  return docs as unknown as RuleVersion[];
}

// ─── 对比两个版本的差异 ────────────────────────────────────────────
export async function compareRuleVersions(
  ruleId: string,
  versionA: number,
  versionB: number
): Promise<{
  diffs: FieldDiff[];
  versionA: RuleVersion | null;
  versionB: RuleVersion | null;
}> {
  const db = await getMongoDb();
  if (!db) return { diffs: [], versionA: null, versionB: null };

  const [docA, docB] = await Promise.all([
    db.collection(COLLECTIONS.RULE_VERSIONS).findOne({ ruleId, version: versionA }) as Promise<any>,
    db.collection(COLLECTIONS.RULE_VERSIONS).findOne({ ruleId, version: versionB }) as Promise<any>,
  ]);

  if (!docA || !docB) return { diffs: [], versionA: docA, versionB: docB };

  const snapshotA = docA.snapshot || {};
  const snapshotB = docB.snapshot || {};

  // 比较所有字段
  const allFields = new Set([
    ...Object.keys(snapshotA),
    ...Object.keys(snapshotB),
  ].filter(f => !["_id", "_embedding", "_embeddingUpdatedAt"].includes(f)));

  const diffs: FieldDiff[] = [];

  for (const field of Array.from(allFields)) {
    const valA = snapshotA[field];
    const valB = snapshotB[field];

    if (deepEqual(valA, valB)) continue;

    let changeType: "added" | "removed" | "modified" = "modified";
    if (valA === undefined || valA === null) changeType = "added";
    else if (valB === undefined || valB === null) changeType = "removed";

    diffs.push({
      field,
      label: FIELD_LABELS[field] || field,
      oldValue: valA,
      newValue: valB,
      changeType,
    });
  }

  return { diffs, versionA: docA, versionB: docB };
}

// ─── 版本回滚（恢复到指定版本的快照） ────────────────────────────
export async function rollbackRuleToVersion(
  ruleId: string,
  targetVersion: number,
  operatorId: number,
  operatorEmail: string
): Promise<{ success: boolean; restoredFields: string[] }> {
  const db = await getMongoDb();
  if (!db) return { success: false, restoredFields: [] };

  const versionDoc = await db.collection(COLLECTIONS.RULE_VERSIONS)
    .findOne({ ruleId, version: targetVersion }) as any;

  if (!versionDoc) return { success: false, restoredFields: [] };

  // 获取当前规则
  const currentRule = await db.collection(COLLECTIONS.COMPLIANCE_RULES)
    .findOne({ _id: new ObjectId(ruleId) }) as any;

  if (!currentRule) return { success: false, restoredFields: [] };

  // 先保存当前版本快照
  await saveRuleVersion(ruleId, currentRule, versionDoc.snapshot, operatorId, operatorEmail);

  // 恢复快照（保留_id，去除快照中的_id）
  const { _id: _snapId, ...restoreData } = versionDoc.snapshot;
  const restoredFields = Object.keys(restoreData).filter(k => !["_embedding", "_embeddingUpdatedAt"].includes(k));

  await db.collection(COLLECTIONS.COMPLIANCE_RULES).updateOne(
    { _id: new ObjectId(ruleId) },
    { $set: { ...restoreData, updatedAt: new Date(), _rollbackFrom: targetVersion } }
  );

  return { success: true, restoredFields };
}