package actor

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

	messages "git.k6n.net/go-cart-actor/pkg/messages"
	"go.opentelemetry.io/contrib/bridges/otelslog"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/metric"
	"google.golang.org/grpc"
	"google.golang.org/grpc/reflection"
)

// ControlServer implements the ControlPlane gRPC services.
// It delegates to a grain pool and cluster operations to a synced pool.
type ControlServer[V any] struct {
	messages.UnimplementedControlPlaneServer
	pool GrainPool[V]
}

const name = "grpc_server"

var (
	tracer                 = otel.Tracer(name)
	meter                  = otel.Meter(name)
	logger                 = otelslog.NewLogger(name)
	pingCalls              metric.Int64Counter
	negotiateCalls         metric.Int64Counter
	getLocalActorIdsCalls  metric.Int64Counter
	announceOwnershipCalls metric.Int64Counter
	announceExpiryCalls    metric.Int64Counter
	closingCalls           metric.Int64Counter
)

func init() {
	var err error
	pingCalls, err = meter.Int64Counter("grpc.ping_calls",
		metric.WithDescription("Number of ping calls"),
		metric.WithUnit("{calls}"))
	if err != nil {
		panic(err)
	}
	negotiateCalls, err = meter.Int64Counter("grpc.negotiate_calls",
		metric.WithDescription("Number of negotiate calls"),
		metric.WithUnit("{calls}"))
	if err != nil {
		panic(err)
	}
	getLocalActorIdsCalls, err = meter.Int64Counter("grpc.get_local_actor_ids_calls",
		metric.WithDescription("Number of get local actor ids calls"),
		metric.WithUnit("{calls}"))
	if err != nil {
		panic(err)
	}
	announceOwnershipCalls, err = meter.Int64Counter("grpc.announce_ownership_calls",
		metric.WithDescription("Number of announce ownership calls"),
		metric.WithUnit("{calls}"))
	if err != nil {
		panic(err)
	}
	announceExpiryCalls, err = meter.Int64Counter("grpc.announce_expiry_calls",
		metric.WithDescription("Number of announce expiry calls"),
		metric.WithUnit("{calls}"))
	if err != nil {
		panic(err)
	}
	closingCalls, err = meter.Int64Counter("grpc.closing_calls",
		metric.WithDescription("Number of closing calls"),
		metric.WithUnit("{calls}"))
	if err != nil {
		panic(err)
	}
}

func (s *ControlServer[V]) AnnounceOwnership(ctx context.Context, req *messages.OwnershipAnnounce) (*messages.OwnerChangeAck, error) {
	ctx, span := tracer.Start(ctx, "grpc_announce_ownership")
	defer span.End()
	span.SetAttributes(
		attribute.String("component", "controlplane"),
		attribute.String("host", req.Host),
		attribute.Int("id_count", len(req.Ids)),
	)
	logger.InfoContext(ctx, "announce ownership", "host", req.Host, "id_count", len(req.Ids))
	announceOwnershipCalls.Add(ctx, 1, metric.WithAttributes(attribute.String("host", req.Host)))

	err := s.pool.HandleOwnershipChange(req.Host, req.Ids)
	if err != nil {
		span.RecordError(err)
		return &messages.OwnerChangeAck{
			Accepted: false,
			Message:  "owner change failed",
		}, err
	}

	log.Printf("Ack count: %d", len(req.Ids))
	return &messages.OwnerChangeAck{
		Accepted: true,
		Message:  "ownership announced",
	}, nil
}

func (s *ControlServer[V]) AnnounceExpiry(ctx context.Context, req *messages.ExpiryAnnounce) (*messages.OwnerChangeAck, error) {
	ctx, span := tracer.Start(ctx, "grpc_announce_expiry")
	defer span.End()
	span.SetAttributes(
		attribute.String("component", "controlplane"),
		attribute.String("host", req.Host),
		attribute.Int("id_count", len(req.Ids)),
	)
	logger.InfoContext(ctx, "announce expiry", "host", req.Host, "id_count", len(req.Ids))
	announceExpiryCalls.Add(ctx, 1, metric.WithAttributes(attribute.String("host", req.Host)))

	err := s.pool.HandleRemoteExpiry(req.Host, req.Ids)
	if err != nil {
		span.RecordError(err)
	}
	return &messages.OwnerChangeAck{
		Accepted: err == nil,
		Message:  "expiry acknowledged",
	}, nil
}

// ControlPlane: Ping
func (s *ControlServer[V]) Ping(ctx context.Context, _ *messages.Empty) (*messages.PingReply, error) {

	host := s.pool.Hostname()

	pingCalls.Add(ctx, 1, metric.WithAttributes(attribute.String("host", host)))

	// log.Printf("got ping")
	return &messages.PingReply{
		Host:     host,
		UnixTime: time.Now().Unix(),
	}, nil
}

// ControlPlane: Negotiate (merge host views)
func (s *ControlServer[V]) Negotiate(ctx context.Context, req *messages.NegotiateRequest) (*messages.NegotiateReply, error) {
	ctx, span := tracer.Start(ctx, "grpc_negotiate")
	defer span.End()
	span.SetAttributes(
		attribute.String("component", "controlplane"),
		attribute.Int("known_hosts_count", len(req.KnownHosts)),
	)
	logger.InfoContext(ctx, "negotiate", "known_hosts_count", len(req.KnownHosts))
	negotiateCalls.Add(ctx, 1)

	s.pool.Negotiate(req.KnownHosts)
	return &messages.NegotiateReply{Hosts: req.GetKnownHosts()}, nil
}

// ControlPlane: GetCartIds (locally owned carts only)
func (s *ControlServer[V]) GetLocalActorIds(ctx context.Context, _ *messages.Empty) (*messages.ActorIdsReply, error) {
	ctx, span := tracer.Start(ctx, "grpc_get_local_actor_ids")
	defer span.End()
	ids := s.pool.GetLocalIds()
	span.SetAttributes(
		attribute.String("component", "controlplane"),
		attribute.Int("id_count", len(ids)),
	)
	logger.InfoContext(ctx, "get local actor ids", "id_count", len(ids))
	getLocalActorIdsCalls.Add(ctx, 1)

	return &messages.ActorIdsReply{Ids: ids}, nil
}

// ControlPlane: Closing (peer shutdown notification)
func (s *ControlServer[V]) Closing(ctx context.Context, req *messages.ClosingNotice) (*messages.OwnerChangeAck, error) {
	ctx, span := tracer.Start(ctx, "grpc_closing")
	defer span.End()
	host := req.GetHost()
	span.SetAttributes(
		attribute.String("component", "controlplane"),
		attribute.String("host", host),
	)
	logger.InfoContext(ctx, "closing notice", "host", host)
	closingCalls.Add(ctx, 1, metric.WithAttributes(attribute.String("host", host)))

	if host != "" {
		s.pool.RemoveHost(host)
	}
	return &messages.OwnerChangeAck{
		Accepted: true,
		Message:  "removed host",
	}, nil
}

type ServerConfig struct {
	Addr    string
	Options []grpc.ServerOption
}

func NewServerConfig(addr string, options ...grpc.ServerOption) ServerConfig {
	return ServerConfig{
		Addr:    addr,
		Options: options,
	}
}

func DefaultServerConfig() ServerConfig {
	return NewServerConfig(":1337")
}

// StartGRPCServer configures and starts the unified gRPC server on the given address.
// It registers both the CartActor and ControlPlane services.
func NewControlServer[V any](config ServerConfig, pool GrainPool[V]) (*grpc.Server, error) {
	lis, err := net.Listen("tcp", config.Addr)
	if err != nil {
		return nil, fmt.Errorf("failed to listen: %w", err)
	}

	grpcServer := grpc.NewServer(config.Options...)
	server := &ControlServer[V]{
		pool: pool,
	}

	messages.RegisterControlPlaneServer(grpcServer, server)
	reflection.Register(grpcServer)

	log.Printf("gRPC server listening as %s on %s", pool.Hostname(), config.Addr)
	go func() {
		if err := grpcServer.Serve(lis); err != nil {
			log.Fatalf("failed to serve gRPC: %v", err)
		}
	}()

	return grpcServer, nil
}