package rpc

import (
	"context"
	"errors"
	"fmt"
	"log"
	"net"
	"sync"
	"time"

	"github.com/jinzhu/copier"
	geoipx "github.com/nezhahq/nezha/pkg/geoip"
	"github.com/nezhahq/nezha/pkg/grpcx"
	"github.com/nezhahq/nezha/pkg/tsdb"

	"github.com/nezhahq/nezha/model"
	pb "github.com/nezhahq/nezha/proto"
	"github.com/nezhahq/nezha/service/singleton"
)

var _ pb.NezhaServiceServer = (*NezhaHandler)(nil)

var NezhaHandlerSingleton *NezhaHandler

type NezhaHandler struct {
	Auth          *authHandler
	ioStreams     map[string]*ioStreamContext
	ioStreamMutex *sync.RWMutex
}

func NewNezhaHandler() *NezhaHandler {
	return &NezhaHandler{
		Auth:          &authHandler{},
		ioStreamMutex: new(sync.RWMutex),
		ioStreams:     make(map[string]*ioStreamContext),
	}
}

// attachRequestTaskStream resolves the server for clientID and publishes the
// task stream. It mirrors the !ok || server == nil guard the other RPC entry
// points use: the server can be deleted between CheckRequestTask and this
// lookup, in which case Get returns a nil *Server and SetTaskStream would
// panic.
func attachRequestTaskStream(clientID uint64, stream pb.NezhaService_RequestTaskServer) (*model.Server, bool) {
	server, ok := singleton.ServerShared.Get(clientID)
	if !ok || server == nil {
		return nil, false
	}
	server.SetTaskStream(stream)
	return server, true
}

// clearRequestTaskStream detaches the dropped stream from whichever *Server is
// currently published for clientID. Edit and transfer rotation publish a new
// *Server that adopts the same stream holder, so cleanup must target the live
// map entry; the captured server is only the fallback for a removed entry.
func clearRequestTaskStream(clientID uint64, captured *model.Server, stream pb.NezhaService_RequestTaskServer) {
	if current, ok := singleton.ServerShared.Get(clientID); ok && current != nil {
		current.ClearTaskStreamIfCurrent(stream)
		return
	}
	captured.ClearTaskStreamIfCurrent(stream)
}

func (s *NezhaHandler) RequestTask(stream pb.NezhaService_RequestTaskServer) error {
	var clientID uint64
	var err error
	if clientID, err = s.Auth.CheckRequestTask(stream.Context()); err != nil {
		return err
	}

	server, ok := attachRequestTaskStream(clientID, stream)
	if !ok {
		return nil
	}
	defer clearRequestTaskStream(clientID, server, stream)
	// If a transfer is mid-flight for this server, the agent has just brought
	// up a fresh bidi stream — this is the moment to (re)deliver the
	// ApplyConfig task carrying the new owner's AgentSecret. Pushes from
	// dashboard mutation time are best-effort; this hook is the reliable
	// re-delivery point that closes the offline-during-transfer gap.
	if singleton.ServerTransferShared != nil {
		singleton.ServerTransferShared.OnAgentReconnect(clientID)
	}
	var result *pb.TaskResult
	for {
		result, err = stream.Recv()
		if err != nil {
			log.Printf("NEZHA>> RequestTask error: %v, clientID: %d\n", err, clientID)
			return err
		}
		switch result.GetType() {
		case model.TaskTypeCommand:
			// 处理上报的计划任务
			cr, _ := singleton.CronShared.Get(result.GetId())
			// 任务结果 ID 来自 agent，必须确认该 cron 本应派发给当前 reporter。
			if singleton.CanReportCronResult(cr, server) {
				// 保存当前服务器状态信息
				var curServer model.Server
				copier.Copy(&curServer, server)
				if cr.PushSuccessful && result.GetSuccessful() {
					singleton.NotificationShared.SendNotification(cr.NotificationGroupID, fmt.Sprintf("[%s] %s, %s\n%s", singleton.Localizer.T("Scheduled Task Executed Successfully"),
						cr.Name, server.Name, result.GetData()), "", &curServer)
				}
				if !result.GetSuccessful() {
					singleton.NotificationShared.SendNotification(cr.NotificationGroupID, fmt.Sprintf("[%s] %s, %s\n%s", singleton.Localizer.T("Scheduled Task Executed Failed"),
						cr.Name, server.Name, result.GetData()), "", &curServer)
				}
				singleton.DB.Model(cr).Updates(model.Cron{
					LastExecutedAt: time.Now().Add(time.Second * -1 * time.Duration(result.GetDelay())),
					LastResult:     result.GetSuccessful(),
				})
			}
		case model.TaskTypeReportConfig:
			if len(server.ConfigCache) < 1 {
				if !result.GetSuccessful() {
					server.ConfigCache <- errors.New(result.Data)
					continue
				}
				server.ConfigCache <- result.Data
			}
		case model.TaskTypeServerTransferApply:
			// Authorization: TaskResult.Id is attacker-controlled. Without
			// the pending.ID == result.Id check below, agent A could cancel
			// server B's in-flight transfer by spoofing B's transfer ID —
			// same class of bug as commit 02129f1 in the cron path.
			// Successful=true here is best-effort only; the authoritative
			// verification is the agent's reconnect under the new secret.
			if singleton.ServerTransferShared == nil {
				continue
			}
			pending, ok := singleton.ServerTransferShared.LookupPending(clientID)
			if !ok || pending.ID != result.GetId() {
				log.Printf("NEZHA>> ServerTransferApply result ignored: clientID=%d reported transferID=%d but no matching pending transfer", clientID, result.GetId())
				continue
			}
			if result.GetSuccessful() {
				continue
			}
			if _, err := singleton.ServerTransferShared.MarkFailed(result.GetId(), result.GetData()); err != nil {
				log.Printf("NEZHA>> ServerTransfer MarkFailed(%d) failed: %v", result.GetId(), err)
			}
		default:
			if model.IsMCPRPCResult(result.GetType()) {
				deliverMCPResultFromReporter(result, clientID)
				continue
			}
			if model.IsServiceSentinelNeeded(result.GetType()) {
				singleton.ServiceSentinelShared.Dispatch(singleton.ReportData{
					Data:     result,
					Reporter: clientID,
				})
			}
		}
	}
}

func (s *NezhaHandler) ReportSystemState(stream pb.NezhaService_ReportSystemStateServer) error {
	clientID, err := s.Auth.Check(stream.Context())
	if err != nil {
		return err
	}
	var state *pb.State
	for {
		state, err = stream.Recv()
		if err != nil {
			log.Printf("NEZHA>> ReportSystemState error: %v, clientID: %d\n", err, clientID)
			return err
		}
		innerState := model.PB2State(state)

		server, ok := singleton.ServerShared.Get(clientID)
		if !ok || server == nil {
			return errors.New("server not found")
		}

		server.LastActive = time.Now()
		server.State = &innerState

		if singleton.TSDBEnabled() {
			maxTemp := 0.0
			for _, t := range innerState.Temperatures {
				if t.Temperature > maxTemp {
					maxTemp = t.Temperature
				}
			}
			maxGPU := 0.0
			for _, g := range innerState.GPU {
				if g > maxGPU {
					maxGPU = g
				}
			}
			if err := singleton.TSDBShared.WriteServerMetrics(&tsdb.ServerMetrics{
				ServerID:       clientID,
				Timestamp:      time.Now(),
				CPU:            innerState.CPU,
				MemUsed:        innerState.MemUsed,
				SwapUsed:       innerState.SwapUsed,
				DiskUsed:       innerState.DiskUsed,
				NetInSpeed:     innerState.NetInSpeed,
				NetOutSpeed:    innerState.NetOutSpeed,
				NetInTransfer:  innerState.NetInTransfer,
				NetOutTransfer: innerState.NetOutTransfer,
				Load1:          innerState.Load1,
				Load5:          innerState.Load5,
				Load15:         innerState.Load15,
				TCPConnCount:   innerState.TcpConnCount,
				UDPConnCount:   innerState.UdpConnCount,
				ProcessCount:   innerState.ProcessCount,
				Temperature:    maxTemp,
				Uptime:         innerState.Uptime,
				GPU:            maxGPU,
			}); err != nil {
				log.Printf("NEZHA>> Failed to write server metrics to TSDB: %v", err)
			}
		}

		// 应对 dashboard / agent 重启的情况，如果从未记录过，先打点，等到小时时间点时入库
		if server.PrevTransferInSnapshot == 0 || server.PrevTransferOutSnapshot == 0 {
			server.PrevTransferInSnapshot = state.NetInTransfer
			server.PrevTransferOutSnapshot = state.NetOutTransfer
		}

		if err = stream.Send(&pb.Receipt{Proced: true}); err != nil {
			return err
		}
	}
}

func (s *NezhaHandler) onReportSystemInfo(c context.Context, r *pb.Host) error {
	var clientID uint64
	var err error
	if clientID, err = s.Auth.Check(c); err != nil {
		return err
	}
	host := model.PB2Host(r)

	server, ok := singleton.ServerShared.Get(clientID)
	if !ok || server == nil {
		return errors.New("server not found")
	}

	/**
	 * 这里的 singleton 中的数据都是关机前的旧数据
	 * 当 agent 重启时，bootTime 变大，agent 端会先上报 host 信息，然后上报 state 信息
	 * 这时可以借助上报顺序的空档，立即记录停机前的数据并重置 Prev* 数据，并由接下来的 state 方法重新赋值
	 */
	if !server.LastActive.IsZero() && host.BootTime > server.Host.BootTime {
		singleton.RecordTransferHourlyUsage(server)
		server.PrevTransferInSnapshot = 0
		server.PrevTransferOutSnapshot = 0
	}

	server.Host = &host
	return nil
}

func (s *NezhaHandler) ReportSystemInfo(c context.Context, r *pb.Host) (*pb.Receipt, error) {
	if err := s.onReportSystemInfo(c, r); err != nil {
		return nil, err
	}
	return &pb.Receipt{Proced: true}, nil
}

func (s *NezhaHandler) ReportSystemInfo2(c context.Context, r *pb.Host) (*pb.Uint64Receipt, error) {
	if err := s.onReportSystemInfo(c, r); err != nil {
		return nil, err
	}
	return &pb.Uint64Receipt{Data: singleton.DashboardBootTime}, nil
}

func (s *NezhaHandler) IOStream(stream pb.NezhaService_IOStreamServer) error {
	clientID, err := s.Auth.Check(stream.Context())
	if err != nil {
		return err
	}
	id, err := stream.Recv()
	if err != nil {
		return err
	}

	// ff05ff05 是 Nezha 的魔数，用于标识流 ID。校验由 isValidIOStreamMagic 完成，
	// 历史 inline 检查曾因 && 短路放过几乎全部非魔数 payload (byte0==0xff 即通过)。
	if id == nil || !isValidIOStreamMagic(id.Data) {
		return fmt.Errorf("invalid stream id")
	}

	streamId := string(id.Data[4:])

	// agent 侧归属校验：只有 createTerminal / createFM / ServeNAT 选定的目标 server
	// 才能接管该 stream。漏掉这一步等同于把 terminal / fm / NAT 会话向所有合法 agent
	// 开放（任何获得 streamId 的 agent 都能抢答），构成 session-hijack RCE 中介。
	// 这是 commit 6661d6a（user 侧归属校验）的对偶补丁。先校验后启 keepalive，
	// 避免未授权 agent 触发悬空 goroutine 持续向其发心跳。
	if !s.IsStreamAuthorizedForAgent(streamId, clientID) {
		return fmt.Errorf("stream not authorized for agent")
	}

	if _, err := s.GetStream(streamId); err != nil {
		return err
	}
	iw := grpcx.NewIOStreamWrapper(stream)

	// Keepalive MUST go through the wrapper so it shares the same sendMu as
	// MCP fs.transfer / terminal / fm Writers. Calling stream.Send directly
	// here used to race those Writers — grpc-go forbids concurrent SendMsg
	// on the same stream. The wrapper's sendMu is the dashboard-side dual
	// of agent/cmd/agent/mcp_fs_transfer.go's serialIOStreamSender.
	keepaliveDone := make(chan struct{})
	go func() {
		defer close(keepaliveDone)
		ticker := time.NewTicker(time.Second * 30)
		defer ticker.Stop()
		for {
			select {
			case <-iw.Context().Done():
				return
			case <-iw.Done():
				// 业务侧（CloseStream / RevokeStreamsForPurpose）调过
				// iw.Close()。即便底层 gRPC stream context 尚未取消，也
				// 必须立刻收手——否则要再等一整个 30s tick，handler 在
				// iw.Wait() 之后又得多等一拍 keepaliveDone 才能返回。
				return
			case <-ticker.C:
				if err := iw.SendKeepalive(); err != nil {
					log.Printf("NEZHA>> IOStream keepAlive error: %v\n", err)
					return
				}
			}
		}
	}()

	if err := s.AgentConnected(streamId, iw); err != nil {
		return err
	}
	iw.Wait()
	<-keepaliveDone
	return nil
}

func (s *NezhaHandler) ReportGeoIP(c context.Context, r *pb.GeoIP) (*pb.GeoIP, error) {
	var clientID uint64
	var err error
	if clientID, err = s.Auth.Check(c); err != nil {
		return nil, err
	}

	geoip := model.PB2GeoIP(r)
	use6 := r.GetUse6()

	if geoip.IP.IPv4Addr == "" && geoip.IP.IPv6Addr == "" {
		ip, _ := c.Value(model.CtxKeyRealIP{}).(string)
		if ip == "" {
			ip, _ = c.Value(model.CtxKeyConnectingIP{}).(string)
		}
		geoip.IP.IPv4Addr = ip
	}

	joinedIP := geoip.IP.Join()

	server, ok := singleton.ServerShared.Get(clientID)
	if !ok || server == nil {
		return nil, fmt.Errorf("server not found")
	}

	// 检查并更新DDNS
	if server.EnableDDNS && joinedIP != "" &&
		(server.GeoIP == nil || server.GeoIP.IP != geoip.IP) {
		ipv4 := geoip.IP.IPv4Addr
		ipv6 := geoip.IP.IPv6Addr

		if err := singleton.ServerShared.UpdateDDNS(server, &model.IP{IPv4Addr: ipv4, IPv6Addr: ipv6}); err != nil {
			log.Printf("NEZHA>> Failed to update DDNS for server %d: %v", err, server.ID)
		}
	}

	// 发送IP变动通知
	if server.GeoIP != nil && singleton.Conf.EnableIPChangeNotification &&
		((singleton.Conf.Cover == model.ConfigCoverAll && !singleton.Conf.IgnoredIPNotificationServerIDs[clientID]) ||
			(singleton.Conf.Cover == model.ConfigCoverIgnoreAll && singleton.Conf.IgnoredIPNotificationServerIDs[clientID])) &&
		server.GeoIP.IP.Join() != "" &&
		joinedIP != "" &&
		server.GeoIP.IP != geoip.IP {

		singleton.NotificationShared.SendNotification(singleton.Conf.IPChangeNotificationGroupID,
			fmt.Sprintf(
				"[%s] %s, %s => %s",
				singleton.Localizer.T("IP Changed"),
				server.Name, singleton.IPDesensitize(server.GeoIP.IP.Join()),
				singleton.IPDesensitize(joinedIP),
			),
			"")
	}

	// 根据内置数据库查询 IP 地理位置
	var ip string
	if geoip.IP.IPv6Addr != "" && (use6 || geoip.IP.IPv4Addr == "") {
		ip = geoip.IP.IPv6Addr
	} else {
		ip = geoip.IP.IPv4Addr
	}

	netIP := net.ParseIP(ip)
	location, err := geoipx.Lookup(netIP)
	if err != nil {
		log.Printf("NEZHA>> geoip.Lookup: %v", err)
	}
	geoip.CountryCode = location

	// 将地区码写入到 Host
	server.GeoIP = &geoip

	return &pb.GeoIP{Ip: nil, CountryCode: location, DashboardBootTime: singleton.DashboardBootTime}, nil
}