package deliver

import (
	"context"
	"fmt"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
	"google.golang.org/protobuf/proto"
	"sonet/api/gen/postal"
	"sonet/pkg/grpc/balancer"
	"sonet/pkg/grpc/discovery"
	"sonet/pkg/utils/logger"
	"sync"
)

type GroupLoader interface {
	Load(uid string) (groupIds []string)
}

type GroupDeliver struct {
	svcName           string
	groupLoader       GroupLoader
	resolver          discovery.Resolver
	postal            postal.PostalClient // postal consistent hash client
	postalDialOptions []grpc.DialOption
	postals           map[string]*Postal
	lock              *sync.RWMutex
}

func NewGroupDeliver(
	msgInServiceName string,
	groupLoader GroupLoader,
	resolver discovery.Resolver,
	postalDialOptions []grpc.DialOption,
) *GroupDeliver {
	return &GroupDeliver{
		svcName:           msgInServiceName,
		groupLoader:       groupLoader,
		resolver:          resolver,
		postalDialOptions: postalDialOptions,
	}
}

func (d *GroupDeliver) Init(ctx context.Context, grpcResolver discovery.GrpcResolver, opts ...grpc.DialOption) (err error) {
	err = d.initPostal(ctx, grpcResolver, opts...)
	if err != nil {
		return
	}

	// initial all postal direct clients
	servers, err := d.resolver.ResolveAll(ctx, postal.Postal_ServiceDesc.ServiceName)
	if err != nil {
		return
	}
	d.buildPostals(servers)

	// watch postal server instance
	err = d.watchPostal(ctx)
	if err != nil {
		return
	}
	return
}

func (d *GroupDeliver) initPostal(ctx context.Context, resolver discovery.GrpcResolver, opts ...grpc.DialOption) (err error) {
	balancer.InitConsistentHashBuilder()
	rb, err := resolver.Resolver()
	if err != nil {
		return
	}

	postalUrl := resolver.DialUrl(postal.Postal_ServiceDesc.ServiceName)
	var options []grpc.DialOption
	// consistent hash lb
	options = append(options, grpc.WithDefaultServiceConfig(fmt.Sprintf(`{"loadBalancingPolicy":"%s"}`, balancer.ConsistentHash)))
	options = append(options, grpc.WithResolvers(rb))
	options = append(options, grpc.WithTransportCredentials(insecure.NewCredentials()))
	options = append(options, opts...)
	conn, err := grpc.DialContext(ctx, postalUrl, options...)
	if err != nil {
		return
	}
	d.postal = postal.NewPostalClient(conn)
	return
}

// watchPostal watch postal service list
func (d *GroupDeliver) watchPostal(ctx context.Context) (err error) {
	ch, err := d.resolver.Watch(ctx, postal.Postal_ServiceDesc.ServiceName)
	if err != nil {
		return
	}
	go func() {
		for {
			select {
			case <-ctx.Done():
				return
			case servers := <-ch:
				d.buildPostals(servers)
			}
		}
	}()
	return
}

func (d *GroupDeliver) buildPostals(servers []discovery.Server) {
	postals := make(map[string]*Postal)
	for _, server := range servers {
		if p, ok := d.postals[server.Addr]; ok {
			postals[server.Addr] = p
			continue
		}
		// new connection
		conn, err := grpc.DialContext(context.Background(), server.Addr, d.postalDialOptions...)
		if err != nil {
			logger.Errorf("dial postal server %+v error: %v", server.Addr, err)
			continue
		}
		postals[server.Addr] = NewPostal(conn)
	}

	// close old connection
	oldPostals := d.postals
	d.postals = postals
	for addr, p := range oldPostals {
		if _, ok := d.postals[addr]; !ok {
			p.Close()
		}
	}
}

func (d *GroupDeliver) DeliverGroup(ctx context.Context, gid string, msg proto.Message, options ...Option) (err error) {
	// deliver to all postal
	message, err := protoMessage2Deliver(d.svcName, msg)
	if err != nil {
		return
	}
	req := postal.ReqDeliverGroup{Gid: gid, Msg: message}
	for _, p := range d.postals {
		p.DeliverGroup(&req)
	}
	return
}

func (d *GroupDeliver) GroupDissolve(gid string) {
	req := postal.ReqGroupDissolve{Gid: gid}
	for _, p := range d.postals {
		p.GroupDissolve(&req)
	}
}

func (d *GroupDeliver) GroupJoin(ctx context.Context, uid string, gids []string) (err error) {
	req := &postal.ReqGroupJoin{Uid: uid, Gids: gids}

	ctx = context.WithValue(ctx, balancer.ConsistentHashKey, uid)
	_, err = d.postal.GroupJoin(ctx, req)
	return
}

func (d *GroupDeliver) GroupLeave(ctx context.Context, uid string, gids []string) (err error) {
	req := &postal.ReqGroupLeave{Uid: uid, Gids: gids}

	ctx = context.WithValue(ctx, balancer.ConsistentHashKey, uid)
	_, err = d.postal.GroupLeave(ctx, req)
	return
}