const mongoose = require('mongoose');

// 检查模型是否已经存在，如果存在则直接返回
if (mongoose.models.Notification) {
  module.exports = mongoose.models.Notification;
  return;
}

const notificationSchema = new mongoose.Schema({
  title: {
    type: String,
    required: true,
    trim: true,
    maxlength: 100
  },
  content: {
    type: String,
    required: true,
    trim: true,
    maxlength: 5000
  },
  type: {
    type: String,
    enum: ['info', 'warning', 'success', 'error', 'announcement'],
    default: 'info'
  },
  priority: {
    type: String,
    enum: ['low', 'medium', 'high', 'urgent'],
    default: 'medium'
  },
  status: {
    type: String,
    enum: ['draft', 'published', 'archived'],
    default: 'draft'
  },
  targetUsers: {
    type: String,
    enum: ['all', 'admin', 'vip', 'regular'],
    default: 'all'
  },
  createdBy: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'User',
    required: true
  },
  publishDate: {
    type: Date,
    default: Date.now
  },
  expiryDate: {
    type: Date,
    default: function() {
      // 默认30天后过期
      const date = new Date();
      date.setDate(date.getDate() + 30);
      return date;
    }
  },
  readBy: [{
    user: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'User'
    },
    readAt: {
      type: Date,
      default: Date.now
    }
  }]
}, {
  timestamps: true
});

// 添加索引以提高查询性能
notificationSchema.index({ status: 1, publishDate: -1 });
notificationSchema.index({ targetUsers: 1, status: 1 });
notificationSchema.index({ expiryDate: 1 }, { expireAfterSeconds: 0 }); // TTL索引，过期自动删除

const Notification = mongoose.model('Notification', notificationSchema);

module.exports = Notification;