require('dotenv').config();
const express = require('express');
const cors = require('cors');
const fs = require('fs');
const path = require('path');

const app = express();
const PORT = process.env.PORT || 3003;

app.use(cors());
app.use(express.json());

// 数据文件路径
const dbPath = path.join(__dirname, '..', '..', 'data', 'inventory-data.json');

function loadDB() {
  try {
    if (fs.existsSync(dbPath)) {
      return JSON.parse(fs.readFileSync(dbPath, 'utf-8'));
    }
  } catch (e) {
    console.error('加载数据库失败:', e.message);
  }
  return { products: [], stockRecords: [], platforms: [] };
}

function saveDB(data) {
  try {
    const dir = path.dirname(dbPath);
    if (!fs.existsSync(dir)) {
      fs.mkdirSync(dir, { recursive: true });
    }
    fs.writeFileSync(dbPath, JSON.stringify(data, null, 2), 'utf-8');
    console.log('💾 数据已保存:', dbPath);
  } catch (e) {
    console.error('保存数据库失败:', e.message);
  }
}

// 初始化
let db = loadDB();
console.log('📊 数据文件:', dbPath);
console.log('📦 商品数:', db.products.length);

// 健康检查
app.get('/api/health', (req, res) => {
  res.json({ status: 'ok', service: 'Inventory API', products: db.products.length });
});

// ============ 商品管理 ============

// 获取商品列表
app.get('/api/products', (req, res) => {
  try {
    const { status, keyword } = req.query;
    let products = db.products;
    
    if (status) {
      products = products.filter(p => p.status === status);
    }
    if (keyword) {
      const k = keyword.toLowerCase();
      products = products.filter(p => 
        p.name.toLowerCase().includes(k) || 
        p.sku.toLowerCase().includes(k)
      );
    }
    
    products.sort((a, b) => new Date(b.created_at) - new Date(a.created_at));
    res.json({ success: true, data: products });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// 获取商品详情
app.get('/api/products/:id', (req, res) => {
  try {
    const product = db.products.find(p => p.id == req.params.id);
    if (!product) {
      return res.status(404).json({ success: false, error: '商品不存在' });
    }
    res.json({ success: true, data: product });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// 创建商品
app.post('/api/products', (req, res) => {
  try {
    const { name, sku, category, price, cost, minStock, description } = req.body;
    
    if (!name || !sku) {
      return res.status(400).json({ success: false, error: '商品名称和 SKU 必填' });
    }
    
    const product = {
      id: Date.now(),
      name,
      sku,
      category: category || '',
      price: parseFloat(price) || 0,
      cost: parseFloat(cost) || 0,
      minStock: parseInt(minStock) || 10,
      description: description || '',
      status: 'active',
      totalStock: 0,
      created_at: new Date().toISOString(),
      updated_at: new Date().toISOString()
    };
    
    db.products.push(product);
    saveDB(db);
    
    res.json({ success: true, data: { id: product.id }, message: '商品创建成功' });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// 更新商品
app.put('/api/products/:id', (req, res) => {
  try {
    const index = db.products.findIndex(p => p.id == req.params.id);
    if (index === -1) {
      return res.status(404).json({ success: false, error: '商品不存在' });
    }
    
    const { name, sku, category, price, cost, minStock, description, status } = req.body;
    db.products[index] = {
      ...db.products[index],
      name, sku, category, price, cost, minStock, description, status,
      updated_at: new Date().toISOString()
    };
    
    saveDB(db);
    res.json({ success: true, message: '商品更新成功' });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// 删除商品
app.delete('/api/products/:id', (req, res) => {
  try {
    const index = db.products.findIndex(p => p.id == req.params.id);
    if (index === -1) {
      return res.status(404).json({ success: false, error: '商品不存在' });
    }
    
    db.products.splice(index, 1);
    db.stockRecords = db.stockRecords.filter(r => r.product_id != req.params.id);
    saveDB(db);
    
    res.json({ success: true, message: '商品删除成功' });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// ============ 库存管理 ============

// 获取库存记录
app.get('/api/stock-records', (req, res) => {
  try {
    const { product_id, type, platform } = req.query;
    let records = db.stockRecords;
    
    if (product_id) {
      records = records.filter(r => r.product_id == product_id);
    }
    if (type) {
      records = records.filter(r => r.type === type);
    }
    if (platform) {
      records = records.filter(r => r.platform === platform);
    }
    
    records.sort((a, b) => new Date(b.created_at) - new Date(a.created_at));
    res.json({ success: true, data: records.slice(0, 100) });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// 添加入库
app.post('/api/stock-in', (req, res) => {
  try {
    const { product_id, quantity, platform, note } = req.body;
    
    if (!product_id || !quantity) {
      return res.status(400).json({ success: false, error: '商品 ID 和数量必填' });
    }
    
    const product = db.products.find(p => p.id == product_id);
    if (!product) {
      return res.status(404).json({ success: false, error: '商品不存在' });
    }
    
    // 添加入库记录
    const record = {
      id: Date.now(),
      product_id,
      type: 'in',
      quantity: parseInt(quantity),
      platform: platform || '总仓',
      note: note || '',
      created_at: new Date().toISOString()
    };
    
    db.stockRecords.push(record);
    
    // 更新商品总库存
    const platformStock = db.stockRecords
      .filter(r => r.product_id == product_id && r.platform === record.platform)
      .reduce((sum, r) => sum + (r.type === 'in' ? r.quantity : -r.quantity), 0);
    
    product.totalStock = db.stockRecords
      .filter(r => r.product_id == product_id)
      .reduce((sum, r) => sum + (r.type === 'in' ? r.quantity : -r.quantity), 0);
    
    product.updated_at = new Date().toISOString();
    saveDB(db);
    
    res.json({ 
      success: true, 
      data: { id: record.id, totalStock: product.totalStock, platformStock },
      message: '入库成功'
    });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// 出库
app.post('/api/stock-out', (req, res) => {
  try {
    const { product_id, quantity, platform, note } = req.body;
    
    if (!product_id || !quantity) {
      return res.status(400).json({ success: false, error: '商品 ID 和数量必填' });
    }
    
    const product = db.products.find(p => p.id == product_id);
    if (!product) {
      return res.status(404).json({ success: false, error: '商品不存在' });
    }
    
    // 检查库存是否充足
    const currentStock = db.stockRecords
      .filter(r => r.product_id == product_id)
      .reduce((sum, r) => sum + (r.type === 'in' ? r.quantity : -r.quantity), 0);
    
    if (currentStock < quantity) {
      return res.status(400).json({ success: false, error: '库存不足' });
    }
    
    // 添加出库记录
    const record = {
      id: Date.now(),
      product_id,
      type: 'out',
      quantity: parseInt(quantity),
      platform: platform || '总仓',
      note: note || '',
      created_at: new Date().toISOString()
    };
    
    db.stockRecords.push(record);
    
    // 更新商品总库存
    product.totalStock = currentStock - quantity;
    product.updated_at = new Date().toISOString();
    saveDB(db);
    
    res.json({ 
      success: true, 
      data: { id: record.id, totalStock: product.totalStock },
      message: '出库成功'
    });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// ============ 平台库存同步 ============

// 获取平台库存
app.get('/api/platform-stock/:product_id', (req, res) => {
  try {
    const product = db.products.find(p => p.id == req.params.product_id);
    if (!product) {
      return res.status(404).json({ success: false, error: '商品不存在' });
    }
    
    const platforms = ['淘宝', '京东', '拼多多', '抖音', '总仓'];
    const stockByPlatform = {};
    
    platforms.forEach(platform => {
      const stock = db.stockRecords
        .filter(r => r.product_id == req.params.product_id && r.platform === platform)
        .reduce((sum, r) => sum + (r.type === 'in' ? r.quantity : -r.quantity), 0);
      stockByPlatform[platform] = stock;
    });
    
    res.json({ 
      success: true, 
      data: { 
        product_id: product.id,
        name: product.name,
        sku: product.sku,
        totalStock: product.totalStock,
        byPlatform: stockByPlatform
      }
    });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// 同步平台库存
app.post('/api/sync-platform/:product_id', (req, res) => {
  try {
    const { platform, quantity } = req.body;
    
    if (!platform || quantity === undefined) {
      return res.status(400).json({ success: false, error: '平台和数量必填' });
    }
    
    const product = db.products.find(p => p.id == req.params.product_id);
    if (!product) {
      return res.status(404).json({ success: false, error: '商品不存在' });
    }
    
    // 获取当前该平台库存
    const currentPlatformStock = db.stockRecords
      .filter(r => r.product_id == req.params.product_id && r.platform === platform)
      .reduce((sum, r) => sum + (r.type === 'in' ? r.quantity : -r.quantity), 0);
    
    const diff = quantity - currentPlatformStock;
    
    // 添加调整记录
    const record = {
      id: Date.now(),
      product_id: product.id,
      type: diff > 0 ? 'in' : 'out',
      quantity: Math.abs(diff),
      platform,
      note: `平台库存同步 (目标：${quantity}, 当前：${currentPlatformStock})`,
      created_at: new Date().toISOString()
    };
    
    db.stockRecords.push(record);
    
    // 更新总库存
    product.totalStock = db.stockRecords
      .filter(r => r.product_id == product.id)
      .reduce((sum, r) => sum + (r.type === 'in' ? r.quantity : -r.quantity), 0);
    
    product.updated_at = new Date().toISOString();
    saveDB(db);
    
    res.json({ 
      success: true, 
      data: { totalStock: product.totalStock, platformStock: quantity },
      message: `库存同步成功 (调整：${diff > 0 ? '+' : ''}${diff})`
    });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// ============ 统计数据 ============

app.get('/api/stats', (req, res) => {
  try {
    const totalProducts = db.products.length;
    const activeProducts = db.products.filter(p => p.status === 'active').length;
    const lowStock = db.products.filter(p => p.totalStock <= p.minStock).length;
    const totalValue = db.products.reduce((sum, p) => sum + (p.cost * p.totalStock), 0);
    
    // 今日出入库
    const today = new Date().toDateString();
    const todayIn = db.stockRecords
      .filter(r => r.type === 'in' && new Date(r.created_at).toDateString() === today)
      .reduce((sum, r) => sum + r.quantity, 0);
    
    const todayOut = db.stockRecords
      .filter(r => r.type === 'out' && new Date(r.created_at).toDateString() === today)
      .reduce((sum, r) => sum + r.quantity, 0);
    
    res.json({
      success: true,
      data: {
        totalProducts,
        activeProducts,
        lowStock,
        totalValue,
        todayIn,
        todayOut
      }
    });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

// 库存预警
app.get('/api/alerts', (req, res) => {
  try {
    const alerts = db.products
      .filter(p => p.totalStock <= p.minStock)
      .map(p => ({
        product_id: p.id,
        name: p.name,
        sku: p.sku,
        currentStock: p.totalStock,
        minStock: p.minStock,
        level: p.totalStock === 0 ? 'critical' : 'warning'
      }));
    
    res.json({ success: true, data: alerts });
  } catch (error) {
    res.status(500).json({ success: false, error: error.message });
  }
});

app.listen(PORT, () => {
  console.log(`🚀 库存管理 API 已启动：http://localhost:${PORT}`);
});