package server

import (
	"context"
	"flag"
	"fmt"
	"net"
	"os"

	"google.golang.org/grpc"
	"google.golang.org/grpc/reflection"
	"k8s.io/klog/v2"

	"source.monogon.dev/cloud/bmaas/bmdb"
	apb "source.monogon.dev/cloud/bmaas/server/api"
	"source.monogon.dev/cloud/lib/component"
)

type Config struct {
	Component component.ComponentConfig
	BMDB      bmdb.BMDB

	// PublicListenAddress is the address at which the 'public' (agent-facing) gRPC
	// server listener will run.
	PublicListenAddress string
}

// TODO(q3k): factor this out to BMDB library?
func runtimeInfo() string {
	hostname, _ := os.Hostname()
	if hostname == "" {
		hostname = "UNKNOWN"
	}
	return fmt.Sprintf("host %s", hostname)
}

func (c *Config) RegisterFlags() {
	c.Component.RegisterFlags("srv")
	c.BMDB.ComponentName = "srv"
	c.BMDB.RuntimeInfo = runtimeInfo()
	c.BMDB.Database.RegisterFlags("bmdb")

	flag.StringVar(&c.PublicListenAddress, "srv_public_grpc_listen_address", ":8080", "Address to listen at for public/user gRPC connections for bmdbsrv")
}

type Server struct {
	Config Config

	// ListenGRPC will contain the address at which the internal gRPC server is
	// listening after .Start() has been called. This can differ from the configured
	// value if the configuration requests any port (via :0).
	ListenGRPC string
	// ListenPublic will contain the address at which the 'public' (agent-facing)
	// gRPC server is lsitening after .Start() has been called.
	ListenPublic string

	bmdb  *bmdb.Connection
	acsvc *agentCallbackService
}

func (s *Server) startPublic(ctx context.Context) {
	g := grpc.NewServer(s.Config.Component.GRPCServerOptionsPublic()...)
	lis, err := net.Listen("tcp", s.Config.PublicListenAddress)
	if err != nil {
		klog.Exitf("Could not listen: %v", err)
	}
	s.ListenPublic = lis.Addr().String()
	apb.RegisterAgentCallbackServer(g, s.acsvc)
	reflection.Register(g)

	klog.Infof("Public API listening on %s", s.ListenPublic)
	go func() {
		err := g.Serve(lis)
		if err != ctx.Err() {
			klog.Exitf("Public gRPC serve failed: %v", err)
		}
	}()
}

func (s *Server) startInternalGRPC(ctx context.Context) {
	g := grpc.NewServer(s.Config.Component.GRPCServerOptions()...)
	lis, err := net.Listen("tcp", s.Config.Component.GRPCListenAddress)
	if err != nil {
		klog.Exitf("Could not listen: %v", err)
	}
	s.ListenGRPC = lis.Addr().String()

	reflection.Register(g)
	klog.Infof("Internal gRPC listening on %s", s.ListenGRPC)
	go func() {
		err := g.Serve(lis)
		if err != ctx.Err() {
			klog.Exitf("Internal gRPC serve failed: %v", err)
		}
	}()
}

// Start the BMaaS Server in background goroutines. This should only be called
// once. The process will exit with debug logs if starting the server failed.
func (s *Server) Start(ctx context.Context) {
	conn, err := s.Config.BMDB.Open(true)
	if err != nil {
		klog.Exitf("Failed to connect to BMDB: %v", err)
	}
	s.acsvc = &agentCallbackService{
		s: s,
	}
	s.bmdb = conn
	s.startInternalGRPC(ctx)
	s.startPublic(ctx)
}