/**
 * 每日进销存 —— 本地库存快照库访问
 *
 * 背景：业务库（MSSQL / JSReportReplica）只有「当前」实时库存 jst_inventoryInfo，
 *       没有按天的历史库存结存表，因此「期初数量」无法回溯。
 *       解决办法：项目本地 MySQL 每天落一份按仓库存的快照，
 *       今日期初 = 上一业务日快照，期末 = 实时库存。
 *
 * 连接复用 LOCAL_DB_* 配置（与项目其它本地表同库）。
 */
const path = require('path');
const dotenv = require('dotenv');
const mysql = require('mysql2/promise');

dotenv.config();
dotenv.config({ path: path.resolve(__dirname, '../../.env') });

const TABLE = 'daily_inventory_snapshot';

const CREATE_SQL = `
CREATE TABLE IF NOT EXISTS ${TABLE} (
  id           BIGINT AUTO_INCREMENT PRIMARY KEY,
  biz_date     DATE          NOT NULL COMMENT '业务日期（T-1）',
  wms_co_id    BIGINT        NOT NULL COMMENT '聚水潭仓库 ID',
  warehouse    VARCHAR(128)  NOT NULL COMMENT '仓库名（主仓）',
  db_warehouse VARCHAR(128)  NULL     COMMENT '监控表仓库名',
  closing_qty  DECIMAL(18,2) NOT NULL DEFAULT 0 COMMENT '该业务日期末数量',
  sku_count    INT           NOT NULL DEFAULT 0 COMMENT '有库存 SKU 数',
  taken_at     DATETIME      NULL     COMMENT '源库库存数据更新时间',
  created_at   DATETIME      NOT NULL DEFAULT CURRENT_TIMESTAMP,
  updated_at   DATETIME      NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  UNIQUE KEY uk_date_wh (biz_date, wms_co_id),
  KEY idx_date (biz_date)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='每日进销存-按仓库存快照';`;

let pool = null;

function getPool() {
  if (pool) return pool;
  pool = mysql.createPool({
    host: process.env.LOCAL_DB_HOST,
    port: Number(process.env.LOCAL_DB_PORT || 3306),
    user: process.env.LOCAL_DB_USER,
    password: process.env.LOCAL_DB_PASSWORD,
    database: process.env.LOCAL_DB_NAME,
    waitForConnections: true,
    connectionLimit: 5,
    connectTimeout: 10000,
    // DATE/DATETIME 直接返回字符串，避免 JS Date 按本地时区回读时整体偏移一天
    dateStrings: true,
  });
  return pool;
}

async function ensureTable() {
  await getPool().query(CREATE_SQL);
}

/**
 * 写入某业务日的期末快照（幂等，重复执行覆盖）
 * @param {string} bizDate YYYY-MM-DD
 * @param {Array<{wmsCoId:number, warehouse:string, dbWarehouse?:string, closingQty:number, skuCount:number, takenAt?:Date|null}>} rows
 */
async function upsertSnapshot(bizDate, rows) {
  if (!bizDate || !rows.length) return 0;
  await ensureTable();
  const conn = await getPool().getConnection();
  try {
    for (const r of rows) {
      await conn.query(
        `INSERT INTO ${TABLE} (biz_date, wms_co_id, warehouse, db_warehouse, closing_qty, sku_count, taken_at)
         VALUES (?, ?, ?, ?, ?, ?, ?)
         ON DUPLICATE KEY UPDATE warehouse = VALUES(warehouse), db_warehouse = VALUES(db_warehouse),
           closing_qty = VALUES(closing_qty), sku_count = VALUES(sku_count), taken_at = VALUES(taken_at)`,
        [bizDate, r.wmsCoId, r.warehouse, r.dbWarehouse || null, r.closingQty, r.skuCount, r.takenAt || null]
      );
    }
    return rows.length;
  } finally {
    conn.release();
  }
}

/**
 * 读取某业务日的期末快照
 * @returns {Promise<Map<string, {closingQty:number, skuCount:number, takenAt:Date|null}>>} key = wmsCoId 字符串
 */
async function fetchSnapshot(bizDate) {
  const map = new Map();
  if (!bizDate) return map;
  try {
    await ensureTable();
    const [rows] = await getPool().query(
      `SELECT wms_co_id AS wmsCoId, closing_qty AS closingQty, sku_count AS skuCount, taken_at AS takenAt
         FROM ${TABLE} WHERE biz_date = ?`,
      [bizDate]
    );
    rows.forEach((r) => map.set(String(r.wmsCoId), {
      closingQty: Number(r.closingQty),
      skuCount: Number(r.skuCount),
      takenAt: r.takenAt || null,
    }));
  } catch (error) {
    console.error('[daily-inventory-snapshot] 读取快照失败:', error.message);
  }
  return map;
}

/** 已有快照的业务日（倒序，最多 n 条） */
async function listSnapshotDates(limit = 10) {
  try {
    await ensureTable();
    const [rows] = await getPool().query(
      `SELECT DISTINCT biz_date AS d FROM ${TABLE} ORDER BY biz_date DESC LIMIT ?`,
      [Number(limit) || 10]
    );
    return rows.map((r) => {
      if (typeof r.d === 'string') return r.d.slice(0, 10);
      const v = new Date(r.d);
      const pad = (n) => String(n).padStart(2, '0');
      return `${v.getFullYear()}-${pad(v.getMonth() + 1)}-${pad(v.getDate())}`;
    });
  } catch (error) {
    console.error('[daily-inventory-snapshot] 读取快照日期失败:', error.message);
    return [];
  }
}

module.exports = {
  TABLE,
  CREATE_SQL,
  getPool,
  ensureTable,
  upsertSnapshot,
  fetchSnapshot,
  listSnapshotDates,
};