from typing import List, Dict, Any, Optional
from sqlalchemy.orm import Session
from datetime import datetime, timedelta
import logging
import json

from app.models.alert import (
    Alert, AlertRule, WhitelistedMAC,
    AlertType, AlertSeverity, AlertStatus
)
from app.models.network import Network, IPAddress
from app.models.snmp import NetworkDevice, ARPEntry

logger = logging.getLogger(__name__)


class AlertService:
    """告警检测与管理服务"""

    @staticmethod
    def create_alert(db: Session,
                    alert_type: AlertType,
                    title: str,
                    message: str = "",
                    severity: AlertSeverity = AlertSeverity.WARNING,
                    network_id: Optional[int] = None,
                    ip_address_id: Optional[int] = None,
                    device_id: Optional[int] = None,
                    ip_address_str: Optional[str] = None,
                    mac_address: Optional[str] = None,
                    conflicting_mac: Optional[str] = None,
                    usage_percent: Optional[float] = None) -> Alert:
        """创建告警"""
        # 检查是否已有相同的活跃告警，避免重复告警
        existing = db.query(Alert).filter(
            Alert.alert_type == alert_type,
            Alert.status == AlertStatus.ACTIVE
        )

        if ip_address_str:
            existing = existing.filter(Alert.ip_address_str == ip_address_str)
        if network_id:
            existing = existing.filter(Alert.network_id == network_id)
        if device_id:
            existing = existing.filter(Alert.device_id == device_id)

        existing = existing.first()

        if existing:
            logger.debug(f"已有相同的活跃告警: {alert_type} - {ip_address_str or network_id or device_id}")
            return existing

        alert = Alert(
            alert_type=alert_type,
            title=title,
            message=message,
            severity=severity,
            network_id=network_id,
            ip_address_id=ip_address_id,
            device_id=device_id,
            ip_address_str=ip_address_str,
            mac_address=mac_address,
            conflicting_mac=conflicting_mac,
            usage_percent=usage_percent
        )

        db.add(alert)
        db.commit()
        db.refresh(alert)

        logger.info(f"创建告警: {alert_type} - {title}")
        return alert

    @staticmethod
    def detect_ip_conflicts(db: Session) -> List[Dict[str, Any]]:
        """检测 IP 冲突"""
        conflicts = []

        # 检查 ARP 表中同一个 IP 对应多个不同 MAC 的情况
        subquery = db.query(
            ARPEntry.ip_address
        ).group_by(ARPEntry.ip_address).having(
            db.func.count(db.func.distinct(ARPEntry.mac_address)) > 1
        ).subquery()

        conflict_entries = db.query(ARPEntry).filter(
            ARPEntry.ip_address.in_(subquery)
        ).order_by(ARPEntry.ip_address).all()

        # 按 IP 分组
        ip_macs = {}
        for entry in conflict_entries:
            if entry.ip_address not in ip_macs:
                ip_macs[entry.ip_address] = set()
            ip_macs[entry.ip_address].add(entry.mac_address)

        # 为每个冲突创建告警
        for ip, macs in ip_macs.items():
            if len(macs) > 1:
                mac_list = list(macs)
                conflict_info = {
                    'ip_address': ip,
                    'mac_addresses': mac_list
                }
                conflicts.append(conflict_info)

                # 创建告警
                AlertService.create_alert(
                    db=db,
                    alert_type=AlertType.IP_CONFLICT,
                    title=f"IP 冲突检测: {ip}",
                    message=f"IP 地址 {ip} 检测到多个 MAC 地址: {', '.join(mac_list)}",
                    severity=AlertSeverity.ERROR,
                    ip_address_str=ip,
                    mac_address=mac_list[0],
                    conflicting_mac=mac_list[1] if len(mac_list) > 1 else None
                )

        return conflicts

    @staticmethod
    def detect_unauthorized_access(db: Session) -> List[Dict[str, Any]]:
        """检测未授权接入（新 MAC 地址不在白名单中）"""
        unauthorized = []

        # 获取白名单 MAC
        whitelist = set()
        whitelist_entries = db.query(WhitelistedMAC).filter(
            WhitelistedMAC.is_active == True
        ).all()
        for entry in whitelist_entries:
            whitelist.add(entry.mac_address.upper())

        # 获取所有 ARP 表中的 MAC 地址
        arp_entries = db.query(ARPEntry).all()

        for entry in arp_entries:
            if not entry.mac_address:
                continue

            mac = entry.mac_address.upper()
            if mac and mac not in whitelist:
                # 检查是否是最近发现的（1小时内）
                is_recent = entry.discovered_at >= datetime.utcnow() - timedelta(hours=1)

                if is_recent:
                    unauth_info = {
                        'ip_address': entry.ip_address,
                        'mac_address': mac,
                        'discovered_at': entry.discovered_at
                    }
                    unauthorized.append(unauth_info)

                    # 创建告警
                    AlertService.create_alert(
                        db=db,
                        alert_type=AlertType.UNAUTHORIZED_ACCESS,
                        title=f"未授权接入: {mac}",
                        message=f"检测到未授权设备接入: IP {entry.ip_address}, MAC {mac}",
                        severity=AlertSeverity.WARNING,
                        ip_address_str=entry.ip_address,
                        mac_address=mac
                    )

        return unauthorized

    @staticmethod
    def detect_subnet_exhaustion(db: Session) -> List[Dict[str, Any]]:
        """检测网段耗尽"""
        exhausted = []

        # 获取所有网段的统计信息
        networks = db.query(Network).all()

        for network in networks:
            if network.total_ips == 0:
                continue

            # 计算使用中的 IP 数量（在线或已分配）
            used_count = db.query(IPAddress).filter(
                IPAddress.network_id == network.id
            ).filter(
                (IPAddress.mac_address.isnot(None)) |
                (IPAddress.hostname.isnot(None))
            ).count()

            usage_percent = (used_count / network.total_ips) * 100

            # 默认阈值 90%
            threshold = 90.0

            if usage_percent >= threshold:
                exhaustion_info = {
                    'network_id': network.id,
                    'cidr': network.cidr,
                    'name': network.name,
                    'total_ips': network.total_ips,
                    'used_ips': used_count,
                    'usage_percent': round(usage_percent, 2)
                }
                exhausted.append(exhaustion_info)

                # 创建告警
                AlertService.create_alert(
                    db=db,
                    alert_type=AlertType.SUBNET_FULL,
                    title=f"网段使用率告警: {network.cidr}",
                    message=f"网段 {network.cidr} ({network.name}) 使用率达到 {round(usage_percent, 2)}%，总IP {network.total_ips}，已使用 {used_count}",
                    severity=AlertSeverity.WARNING if usage_percent < 95 else AlertSeverity.CRITICAL,
                    network_id=network.id,
                    usage_percent=usage_percent
                )

        return exhausted

    @staticmethod
    def detect_new_devices(db: Session) -> List[Dict[str, Any]]:
        """检测新发现的设备"""
        new_devices = []

        # 查找最近 1 小时内发现的新 MAC 地址
        one_hour_ago = datetime.utcnow() - timedelta(hours=1)

        recent_entries = db.query(ARPEntry).filter(
            ARPEntry.discovered_at >= one_hour_ago
        ).all()

        for entry in recent_entries:
            # 检查此 MAC 是否是新出现的
            older_entries = db.query(ARPEntry).filter(
                ARPEntry.mac_address == entry.mac_address,
                ARPEntry.discovered_at < one_hour_ago
            ).count()

            if older_entries == 0 and entry.mac_address:
                device_info = {
                    'ip_address': entry.ip_address,
                    'mac_address': entry.mac_address,
                    'discovered_at': entry.discovered_at
                }
                new_devices.append(device_info)

                # 创建告警
                AlertService.create_alert(
                    db=db,
                    alert_type=AlertType.NEW_DEVICE_DETECTED,
                    title=f"新设备发现: {entry.ip_address}",
                    message=f"检测到新设备: IP {entry.ip_address}, MAC {entry.mac_address}",
                    severity=AlertSeverity.INFO,
                    ip_address_str=entry.ip_address,
                    mac_address=entry.mac_address
                )

        return new_devices

    @staticmethod
    def detect_device_offline(db: Session) -> List[Dict[str, Any]]:
        """检测设备离线"""
        offline_devices = []

        # 检查网络设备是否长时间没有成功轮询
        threshold_time = datetime.utcnow() - timedelta(hours=2)

        offline_network_devices = db.query(NetworkDevice).filter(
            NetworkDevice.is_active == True,
            (NetworkDevice.last_successful_poll < threshold_time) |
            (NetworkDevice.last_successful_poll == None)
        ).all()

        for device in offline_network_devices:
            offline_info = {
                'device_id': device.id,
                'device_name': device.name,
                'ip_address': device.ip_address,
                'last_polled_at': device.last_polled_at,
                'last_successful_poll': device.last_successful_poll
            }
            offline_devices.append(offline_info)

            # 创建告警
            AlertService.create_alert(
                db=db,
                alert_type=AlertType.DEVICE_OFFLINE,
                title=f"设备离线: {device.name}",
                message=f"网络设备 {device.name} ({device.ip_address}) 已超过 2 小时未成功轮询",
                severity=AlertSeverity.ERROR,
                device_id=device.id
            )

        return offline_devices

    @staticmethod
    def run_all_detections(db: Session) -> Dict[str, Any]:
        """运行所有检测"""
        results = {}

        logger.info("开始运行告警检测...")

        # 检测 IP 冲突
        conflicts = AlertService.detect_ip_conflicts(db)
        results['ip_conflicts'] = {
            'count': len(conflicts),
            'items': conflicts
        }

        # 检测未授权接入
        unauthorized = AlertService.detect_unauthorized_access(db)
        results['unauthorized_access'] = {
            'count': len(unauthorized),
            'items': unauthorized
        }

        # 检测网段耗尽
        subnet_exhaustion = AlertService.detect_subnet_exhaustion(db)
        results['subnet_exhaustion'] = {
            'count': len(subnet_exhaustion),
            'items': subnet_exhaustion
        }

        # 检测新设备
        new_devices = AlertService.detect_new_devices(db)
        results['new_devices'] = {
            'count': len(new_devices),
            'items': new_devices
        }

        # 检测设备离线
        offline_devices = AlertService.detect_device_offline(db)
        results['offline_devices'] = {
            'count': len(offline_devices),
            'items': offline_devices
        }

        total_alerts = sum(v['count'] for v in results.values())
        logger.info(f"告警检测完成，共发现 {total_alerts} 个问题")

        return results

    @staticmethod
    def get_alerts(db: Session,
                  status: Optional[AlertStatus] = None,
                  severity: Optional[AlertSeverity] = None,
                  alert_type: Optional[AlertType] = None,
                  skip: int = 0,
                  limit: int = 100) -> tuple[int, List[Alert]]:
        """获取告警列表"""
        query = db.query(Alert)

        if status:
            query = query.filter(Alert.status == status)
        if severity:
            query = query.filter(Alert.severity == severity)
        if alert_type:
            query = query.filter(Alert.alert_type == alert_type)

        total = query.count()
        items = query.order_by(Alert.created_at.desc()).offset(skip).limit(limit).all()

        return total, items

    @staticmethod
    def acknowledge_alert(db: Session, alert_id: int, acknowledged_by: str = "system") -> Optional[Alert]:
        """确认告警"""
        alert = db.query(Alert).filter(Alert.id == alert_id).first()
        if not alert:
            return None

        alert.status = AlertStatus.ACKNOWLEDGED
        alert.acknowledged_by = acknowledged_by
        alert.acknowledged_at = datetime.utcnow()
        db.commit()
        db.refresh(alert)

        return alert

    @staticmethod
    def resolve_alert(db: Session, alert_id: int, resolved_by: str = "system", notes: str = "") -> Optional[Alert]:
        """解决告警"""
        alert = db.query(Alert).filter(Alert.id == alert_id).first()
        if not alert:
            return None

        alert.status = AlertStatus.RESOLVED
        alert.resolved_by = resolved_by
        alert.resolved_at = datetime.utcnow()
        alert.resolution_notes = notes
        db.commit()
        db.refresh(alert)

        return alert

    @staticmethod
    def ignore_alert(db: Session, alert_id: int) -> Optional[Alert]:
        """忽略告警"""
        alert = db.query(Alert).filter(Alert.id == alert_id).first()
        if not alert:
            return None

        alert.status = AlertStatus.IGNORED
        db.commit()
        db.refresh(alert)

        return alert

    @staticmethod
    def get_statistics(db: Session) -> Dict[str, Any]:
        """获取告警统计"""
        active_count = db.query(Alert).filter(Alert.status == AlertStatus.ACTIVE).count()
        acknowledged_count = db.query(Alert).filter(Alert.status == AlertStatus.ACKNOWLEDGED).count()
        resolved_count = db.query(Alert).filter(Alert.status == AlertStatus.RESOLVED).count()

        # 按严重级别统计
        critical_count = db.query(Alert).filter(
            Alert.status == AlertStatus.ACTIVE,
            Alert.severity == AlertSeverity.CRITICAL
        ).count()
        error_count = db.query(Alert).filter(
            Alert.status == AlertStatus.ACTIVE,
            Alert.severity == AlertSeverity.ERROR
        ).count()
        warning_count = db.query(Alert).filter(
            Alert.status == AlertStatus.ACTIVE,
            Alert.severity == AlertSeverity.WARNING
        ).count()
        info_count = db.query(Alert).filter(
            Alert.status == AlertStatus.ACTIVE,
            Alert.severity == AlertSeverity.INFO
        ).count()

        # 按类型统计
        type_stats = {}
        for alert_type in AlertType:
            count = db.query(Alert).filter(
                Alert.status == AlertStatus.ACTIVE,
                Alert.alert_type == alert_type
            ).count()
            type_stats[alert_type.value] = count

        return {
            'by_status': {
                'active': active_count,
                'acknowledged': acknowledged_count,
                'resolved': resolved_count
            },
            'by_severity': {
                'critical': critical_count,
                'error': error_count,
                'warning': warning_count,
                'info': info_count
            },
            'by_type': type_stats
        }

    @staticmethod
    def add_mac_to_whitelist(db: Session, mac_address: str, description: str = "", owner: str = "") -> WhitelistedMAC:
        """添加 MAC 地址到白名单"""
        existing = db.query(WhitelistedMAC).filter(WhitelistedMAC.mac_address == mac_address.upper()).first()
        if existing:
            existing.is_active = True
            if description:
                existing.description = description
            if owner:
                existing.owner = owner
            db.commit()
            db.refresh(existing)
            return existing

        whitelisted_mac = WhitelistedMAC(
            mac_address=mac_address.upper(),
            description=description,
            owner=owner
        )
        db.add(whitelisted_mac)
        db.commit()
        db.refresh(whitelisted_mac)

        return whitelisted_mac

    @staticmethod
    def get_mac_whitelist(db: Session, skip: int = 0, limit: int = 100) -> tuple[int, List[WhitelistedMAC]]:
        """获取 MAC 白名单"""
        query = db.query(WhitelistedMAC).filter(WhitelistedMAC.is_active == True)
        total = query.count()
        items = query.order_by(WhitelistedMAC.id.desc()).offset(skip).limit(limit).all()
        return total, items

    @staticmethod
    def remove_mac_from_whitelist(db: Session, mac_id: int) -> bool:
        """从白名单移除 MAC 地址"""
        mac = db.query(WhitelistedMAC).filter(WhitelistedMAC.id == mac_id).first()
        if not mac:
            return False

        mac.is_active = False
        db.commit()
        return True