package rpc

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"net/netip"
	"time"

	"google.golang.org/grpc"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/peer"

	"github.com/hashicorp/go-uuid"
	"github.com/nezhahq/nezha/model"
	"github.com/nezhahq/nezha/pkg/utils"
	"github.com/nezhahq/nezha/proto"
	rpcService "github.com/nezhahq/nezha/service/rpc"
	"github.com/nezhahq/nezha/service/singleton"
)

func ServeRPC() *grpc.Server {
	server := grpc.NewServer(grpc.ChainUnaryInterceptor(getRealIp, waf))
	rpcService.NezhaHandlerSingleton = rpcService.NewNezhaHandler()
	proto.RegisterNezhaServiceServer(server, rpcService.NezhaHandlerSingleton)
	return server
}

func waf(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
	realip, _ := ctx.Value(model.CtxKeyRealIP{}).(string)
	if err := model.CheckIP(singleton.DB, realip); err != nil {
		return nil, err
	}
	return handler(ctx, req)
}

func getRealIp(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
	if singleton.Conf.RealIPHeader == "" {
		return handler(ctx, req)
	}

	var ip string

	if singleton.Conf.RealIPHeader == model.ConfigUsePeerIP {
		p, ok := peer.FromContext(ctx)
		if !ok {
			return nil, fmt.Errorf("peer not found")
		}
		addrPort, err := netip.ParseAddrPort(p.Addr.String())
		if err != nil {
			return nil, err
		}
		ip = addrPort.Addr().String()
	} else {
		vals := metadata.ValueFromIncomingContext(ctx, singleton.Conf.RealIPHeader)
		if len(vals) == 0 {
			return nil, fmt.Errorf("real ip header not found")
		}
		var err error
		ip, err = utils.GetIPFromHeader(vals[0])
		if err != nil {
			return nil, err
		}
	}

	if singleton.Conf.Debug {
		log.Printf("NEZHA>> gRPC Real IP: %s", ip)
	}

	ctx = context.WithValue(ctx, model.CtxKeyRealIP{}, ip)
	return handler(ctx, req)
}

func DispatchTask(serviceSentinelDispatchBus <-chan model.Service) {
	workedServerIndex := 0
	for task := range serviceSentinelDispatchBus {
		round := 0
		endIndex := workedServerIndex
		singleton.SortedServerLock.RLock()
		// 如果已经轮了一整圈又轮到自己，没有合适机器去请求，跳出循环
		for round < 1 || workedServerIndex < endIndex {
			// 如果到了圈尾，再回到圈头，圈数加一，游标重置
			if workedServerIndex >= len(singleton.SortedServerList) {
				workedServerIndex = 0
				round++
				continue
			}
			// 如果服务器不在线，跳过这个服务器
			if singleton.SortedServerList[workedServerIndex].TaskStream == nil {
				workedServerIndex++
				continue
			}
			// 如果此任务不可使用此服务器请求，跳过这个服务器（有些 IPv6 only 开了 NAT64 的机器请求 IPv4 总会出问题）
			if (task.Cover == model.ServiceCoverAll && task.SkipServers[singleton.SortedServerList[workedServerIndex].ID]) ||
				(task.Cover == model.ServiceCoverIgnoreAll && !task.SkipServers[singleton.SortedServerList[workedServerIndex].ID]) {
				workedServerIndex++
				continue
			}
			if task.Cover == model.ServiceCoverIgnoreAll && task.SkipServers[singleton.SortedServerList[workedServerIndex].ID] {
				singleton.SortedServerList[workedServerIndex].TaskStream.Send(task.PB())
				workedServerIndex++
				continue
			}
			if task.Cover == model.ServiceCoverAll && !task.SkipServers[singleton.SortedServerList[workedServerIndex].ID] {
				singleton.SortedServerList[workedServerIndex].TaskStream.Send(task.PB())
				workedServerIndex++
				continue
			}
		}
		singleton.SortedServerLock.RUnlock()
	}
}

func DispatchKeepalive() {
	singleton.Cron.AddFunc("@every 20s", func() {
		singleton.SortedServerLock.RLock()
		defer singleton.SortedServerLock.RUnlock()
		for i := 0; i < len(singleton.SortedServerList); i++ {
			if singleton.SortedServerList[i] == nil || singleton.SortedServerList[i].TaskStream == nil {
				continue
			}
			singleton.SortedServerList[i].TaskStream.Send(&proto.Task{Type: model.TaskTypeKeepalive})
		}
	})
}

func ServeNAT(w http.ResponseWriter, r *http.Request, natConfig *model.NAT) {
	singleton.ServerLock.RLock()
	server := singleton.ServerList[natConfig.ServerID]
	singleton.ServerLock.RUnlock()
	if server == nil || server.TaskStream == nil {
		w.WriteHeader(http.StatusServiceUnavailable)
		w.Write([]byte("server not found or not connected"))
		return
	}

	streamId, err := uuid.GenerateUUID()
	if err != nil {
		w.WriteHeader(http.StatusServiceUnavailable)
		w.Write([]byte(fmt.Sprintf("stream id error: %v", err)))
		return
	}

	rpcService.NezhaHandlerSingleton.CreateStream(streamId)
	defer rpcService.NezhaHandlerSingleton.CloseStream(streamId)

	taskData, err := utils.Json.Marshal(model.TaskNAT{
		StreamID: streamId,
		Host:     natConfig.Host,
	})
	if err != nil {
		w.WriteHeader(http.StatusServiceUnavailable)
		w.Write([]byte(fmt.Sprintf("task data error: %v", err)))
		return
	}

	if err := server.TaskStream.Send(&proto.Task{
		Type: model.TaskTypeNAT,
		Data: string(taskData),
	}); err != nil {
		w.WriteHeader(http.StatusServiceUnavailable)
		w.Write([]byte(fmt.Sprintf("send task error: %v", err)))
		return
	}

	wWrapped, err := utils.NewRequestWrapper(r, w)
	if err != nil {
		w.WriteHeader(http.StatusServiceUnavailable)
		w.Write([]byte(fmt.Sprintf("request wrapper error: %v", err)))
		return
	}

	if err := rpcService.NezhaHandlerSingleton.UserConnected(streamId, wWrapped); err != nil {
		w.WriteHeader(http.StatusServiceUnavailable)
		w.Write([]byte(fmt.Sprintf("user connected error: %v", err)))
		return
	}

	rpcService.NezhaHandlerSingleton.StartStream(streamId, time.Second*10)
}