/**
 * 产品资料系统数据库连接模块（PostgreSQL）
 *
 * 数据来源：系统库 database_configs 表中 name = 'product_information_database' 的配置。
 * 典型配置：postgres / 218.93.9.38:25432 / furniture3d_prod / external_full_reader / ssl=1
 *
 * 该库用于 MKH-BOM 资料页面的商品资料匹配：
 *   external.intake_sku_items_ready_v1
 *     —— 真实可用的 SKU 明细视图（约 4.6 万行）
 *     —— source_sku_id 为聚水潭原始 SKU 编码（即业务库 BOM 的配件编码）
 *     —— sku_code 为商品编码，barcode 为条码
 *   external.warehouse_locations_v1 —— 库位主数据（当前仅 1 行：A-01 成品区）
 *
 * 说明：external.product_bom_v1 / product_skus_v1 当前为空视图，不可用。
 */

const { Pool } = require('pg');
const database = require('./database');

const CONFIG_NAME = 'product_information_database';
const READY_VIEW = 'external.intake_sku_items_ready_v1';
const LOCATION_VIEW = 'external.warehouse_locations_v1';

const parsePositiveInt = (value, fallback) => {
  const parsed = Number.parseInt(value, 10);
  return Number.isFinite(parsed) && parsed > 0 ? parsed : fallback;
};

const POOL_MAX = parsePositiveInt(process.env.PRODUCT_DB_POOL_MAX, 4);

let pool = null;
let cachedSignature = '';

const truthy = (value) => (
  value === true || value === 1 || String(value || '').toLowerCase() === 'true' || String(value || '') === '1'
);

async function loadStoredConfig() {
  const rows = await database.local.query(
    `SELECT id, host, port, database_name, username, password, \`ssl\`, driver, status
     FROM database_configs WHERE name = ? LIMIT 1`,
    [CONFIG_NAME]
  );

  const config = rows[0];
  if (!config) {
    const error = new Error('产品资料系统数据库尚未配置，请在「系统设置 - 数据库配置」中完成配置');
    error.statusCode = 503;
    error.code = 'PRODUCT_DB_NOT_CONFIGURED';
    throw error;
  }

  if (String(config.driver || '').toLowerCase() !== 'postgres') {
    const error = new Error('产品资料系统数据库需要选择 PostgreSQL 类型');
    error.statusCode = 503;
    error.code = 'PRODUCT_DB_DRIVER_MISMATCH';
    throw error;
  }

  return {
    id: config.id,
    host: String(config.host || '').trim(),
    port: Number(config.port) || 5432,
    database: String(config.database_name || '').trim(),
    user: String(config.username || '').trim(),
    password: config.password || '',
    ssl: truthy(config.ssl),
  };
}

const buildSignature = (config) => [
  config.id,
  config.host,
  config.port,
  config.database,
  config.user,
  config.ssl ? 'ssl' : 'nossl',
].join('::');

async function getPool() {
  const config = await loadStoredConfig();
  const signature = buildSignature(config);

  if (pool && signature === cachedSignature) {
    return pool;
  }

  if (pool) {
    await pool.end().catch(() => {});
    pool = null;
  }

  pool = new Pool({
    host: config.host,
    port: config.port,
    database: config.database,
    user: config.user,
    password: config.password,
    ssl: config.ssl ? { rejectUnauthorized: false } : false,
    max: POOL_MAX,
    idleTimeoutMillis: 30000,
    connectionTimeoutMillis: 20000,
    query_timeout: 180000,
    statement_timeout: 180000,
  });

  pool.on('error', (error) => {
    console.warn('[ProductDB] 连接池异常:', error.message);
  });

  cachedSignature = signature;
  return pool;
}

/**
 * 执行查询，返回行数组。
 * @param {string} sqlText PostgreSQL 语句（使用 $1/$2 占位）
 * @param {Array} params 参数数组
 */
async function query(sqlText, params = []) {
  const maxAttempts = 2;
  let lastError = null;

  for (let attempt = 1; attempt <= maxAttempts; attempt += 1) {
    try {
      const activePool = await getPool();
      const result = await activePool.query(sqlText, params);
      return result.rows;
    } catch (error) {
      lastError = error;
      if (error.code === 'PRODUCT_DB_NOT_CONFIGURED' || error.code === 'PRODUCT_DB_DRIVER_MISMATCH') {
        throw error;
      }
      if (attempt < maxAttempts) {
        console.warn(`[ProductDB] 查询失败，准备重连后重试 (${attempt}/${maxAttempts}): ${error.message}`);
        await reset();
      }
    }
  }

  throw lastError;
}

async function reset() {
  if (pool) {
    await pool.end().catch(() => {});
  }
  pool = null;
  cachedSignature = '';
}

async function test() {
  try {
    const rows = await query('SELECT 1 AS test');
    return { success: true, message: '产品资料系统数据库连接成功', data: rows };
  } catch (error) {
    return { success: false, message: `连接失败: ${error.message}` };
  }
}

module.exports = {
  query,
  test,
  reset,
  getPool,
  CONFIG_NAME,
  READY_VIEW,
  LOCATION_VIEW,
};