const express = require('express');
const db = require('../db');
const config = require('../config');
const logger = require('../utils/logger');
const {
  parseCSVLine,
  AppError,
  validateNumber,
  validateInList,
  validateIsoDate,
  optionalString
} = require('../utils/helpers');

const router = express.Router();

function emptyToNull(value) {
  return value === undefined || value === null || value === '' ? null : value;
}

function nullableDbValue(value) {
  return value === undefined || value === null || value === '' ? null : value;
}

// 导出数据
router.get('/export', (req, res, next) => {
  try {
    const format = req.query.format;
    if (!format || !['json', 'csv'].includes(format)) {
      throw new AppError('请指定格式: json 或 csv', 400);
    }

    const records = db.prepare(
      'SELECT type, category, amount, quantity, unit_price, rebate, boss, partner, source, destination, note, created_at FROM records WHERE user_id = ? ORDER BY created_at DESC'
    ).all(req.user.id);

    const timestamp = new Date().toISOString().replace(/[:.]/g, '-').slice(0, 19);
    const filename = `gamer-export-${timestamp}`;

    if (format === 'json') {
      const exportData = {
        exportVersion: 1,
        exportedAt: new Date().toISOString(),
        username: req.user.username,
        recordCount: records.length,
        records
      };
      logger.info(`用户 ${req.user.username} 导出 JSON 数据: ${records.length} 条`);
      res.setHeader('Content-Type', 'application/json; charset=utf-8');
      res.setHeader('Content-Disposition', `attachment; filename="${filename}.json"`);
      return res.send(JSON.stringify(exportData, null, 2));
    }

    // CSV with UTF-8 BOM
    const BOM = '\uFEFF';
    const cols = ['type', 'category', 'amount', 'quantity', 'unit_price', 'rebate', 'boss', 'partner', 'source', 'destination', 'note', 'created_at'];
    const csvRows = records.map(r => {
      return cols.map(col => {
        const val = r[col];
        if (val === null || val === undefined) return '';
        const str = String(val);
        if (str.includes(',') || str.includes('"') || str.includes('\n')) {
          return '"' + str.replace(/"/g, '""') + '"';
        }
        return str;
      }).join(',');
    });
    logger.info(`用户 ${req.user.username} 导出 CSV 数据: ${records.length} 条`);
    res.setHeader('Content-Type', 'text/csv; charset=utf-8');
    res.setHeader('Content-Disposition', `attachment; filename="${filename}.csv"`);
    res.send(BOM + cols.join(',') + '\n' + csvRows.join('\n'));
  } catch (err) {
    next(err);
  }
});

// 导入数据
router.post('/import', express.text({ type: '*/*', limit: '10mb' }), (req, res, next) => {
  try {
    const raw = req.body;
    if (!raw || typeof raw !== 'string') {
      throw new AppError('未收到文件内容', 400);
    }

    let records = [];
    const requiredFields = ['type', 'category', 'amount', 'created_at'];
    const allFields = ['type', 'category', 'amount', 'quantity', 'unit_price', 'rebate', 'boss', 'partner', 'source', 'destination', 'note', 'created_at'];
    const trimmed = raw.replace(/^\uFEFF/, '').trim();

    if (trimmed.startsWith('{')) {
      const data = JSON.parse(trimmed);
      if (!data.exportVersion || !Array.isArray(data.records)) {
        throw new AppError('无效的JSON导出文件格式', 400);
      }
      records = data.records;
    } else {
      const lines = trimmed.split('\n').map(l => l.replace(/\r$/, ''));
      if (lines.length < 2) {
        throw new AppError('CSV文件为空或格式不正确', 400);
      }
      if (lines[0] !== allFields.join(',')) {
        throw new AppError('CSV列头不匹配，请使用本系统导出的文件', 400);
      }
      const csvHeaders = lines[0].split(',');
      for (let i = 1; i < lines.length; i++) {
        if (!lines[i].trim()) continue;
        const values = parseCSVLine(lines[i]);
        const record = {};
        csvHeaders.forEach((h, idx) => { record[h] = emptyToNull(values[idx]); });
        if (record.amount !== null) record.amount = parseFloat(record.amount);
        if (record.quantity !== null) record.quantity = parseInt(record.quantity, 10);
        if (record.unit_price !== null) record.unit_price = parseFloat(record.unit_price);
        if (record.rebate !== null) record.rebate = parseFloat(record.rebate);
        records.push(record);
      }
    }

    if (records.length > config.import.maxRecords) {
      throw new AppError(`单次最多导入 ${config.import.maxRecords} 条记录`, 400);
    }

    const allCategories = [...config.categories.income, ...config.categories.expense];
    const normalizedRecords = records.map((r, index) => {
      for (const f of requiredFields) {
        if (!r[f] && r[f] !== 0) {
          throw new AppError(`第 ${index + 1} 条记录缺少必填字段: ${f}`, 400);
        }
      }
      validateInList(r.type, 'type', ['income', 'expense']);
      validateInList(r.category, 'category', allCategories);
      const amount = r.category === '派单'
        ? validateNumber(r.amount, '金额')
        : validateNumber(r.amount, '金额', 0);
      return {
        type: r.type,
        category: r.category,
        amount,
        quantity: r.quantity === undefined || r.quantity === null || r.quantity === '' ? null : validateNumber(r.quantity, '数量', 0),
        unit_price: r.unit_price === undefined || r.unit_price === null || r.unit_price === '' ? null : validateNumber(r.unit_price, '单价', 0),
        rebate: r.rebate === undefined || r.rebate === null || r.rebate === '' ? null : validateNumber(r.rebate, '返点'),
        boss: optionalString(r.boss, '老板', 100),
        partner: optionalString(r.partner, '陪玩', 100),
        source: optionalString(r.source, '来源', 100),
        destination: optionalString(r.destination, '去向', 100),
        note: optionalString(r.note, '备注', 500),
        created_at: validateIsoDate(r.created_at, '创建时间')
      };
    });

    const existingCheck = db.prepare(`
      SELECT id FROM records
      WHERE user_id = ?
        AND type = ?
        AND category = ?
        AND amount = ?
        AND COALESCE(quantity, '') = COALESCE(?, '')
        AND COALESCE(unit_price, '') = COALESCE(?, '')
        AND COALESCE(rebate, '') = COALESCE(?, '')
        AND COALESCE(boss, '') = COALESCE(?, '')
        AND COALESCE(partner, '') = COALESCE(?, '')
        AND COALESCE(source, '') = COALESCE(?, '')
        AND COALESCE(destination, '') = COALESCE(?, '')
        AND COALESCE(note, '') = COALESCE(?, '')
        AND created_at = ?
    `);
    const insertStmt = db.prepare(`
      INSERT INTO records (user_id, type, category, amount, quantity, unit_price, rebate, boss, partner, source, destination, note, created_at)
      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
    `);

    let imported = 0, skipped = 0;
    const insertMany = db.transaction((recs) => {
      for (const r of recs) {
        const values = [
          req.user.id,
          r.type,
          r.category,
          r.amount,
          r.quantity,
          r.unit_price,
          r.rebate,
          r.boss,
          r.partner,
          r.source,
          r.destination,
          r.note,
          r.created_at
        ];
        if (existingCheck.get(...values)) {
          skipped++; continue;
        }
        insertStmt.run(req.user.id, r.type, r.category, r.amount,
          nullableDbValue(r.quantity), nullableDbValue(r.unit_price), nullableDbValue(r.rebate),
          nullableDbValue(r.boss), nullableDbValue(r.partner),
          nullableDbValue(r.source), nullableDbValue(r.destination),
          nullableDbValue(r.note), r.created_at);
        imported++;
      }
    });
    insertMany(normalizedRecords);

    logger.info(`用户 ${req.user.username} 导入数据: ${imported} 条, 跳过 ${skipped} 条`);
    res.json({ imported, skipped, total: normalizedRecords.length });
  } catch (err) {
    if (err instanceof SyntaxError) {
      next(new AppError('文件解析失败: ' + err.message, 400));
    } else {
      next(err);
    }
  }
});

module.exports = router;