package signal_server

import (
	"bytes"
	"context"
	"encoding/json"
	"io"
	"log"
	"strings"

	proto "git.jeffthecoder.xyz/guochao/meow-signaling.jeffthecoder.xyz/pkg/proto/signal-server"

	"github.com/redis/go-redis/v9"
	"golang.org/x/sync/errgroup"
)

type SignalingServer struct {
	proto.UnimplementedSignalingServer

	redisKeyPrefix string

	redis redis.UniversalClient
}

type Options struct {
	RedisServers  []string
	RedisDatabase int

	RedisKeyPrefix string
}

func New(options Options) (*SignalingServer, error) {
	redisClient := redis.NewUniversalClient(&redis.UniversalOptions{
		Addrs: options.RedisServers,
		DB:    options.RedisDatabase,
	})

	if err := redisClient.Ping(context.Background()).Err(); err != nil {
		return nil, err
	}

	return &SignalingServer{
		redis: redisClient,

		redisKeyPrefix: options.RedisKeyPrefix,
	}, nil
}

func (signalingServer SignalingServer) handleStream(ctx context.Context, errGroup *errgroup.Group, stream proto.Signaling_ConnectServer) func() error {
	return func() error {
		for {
			msg, err := stream.Recv()
			if err == io.EOF {
				return nil
			} else if err == nil {
				switch innerMsg := msg.Message.(type) {
				case *proto.SignalingMessage_DiscoverRequest:
					// ignore msg.Receiver, from sender to whole channel
					if received, err := signalingServer.redis.Publish(ctx, signalingServer.redisKeyPrefix+":"+msg.Room+":discover", msg.Sender).Result(); err != nil {
						return err
					} else {
						log.Printf("peers received discover request: %v", received)
					}
					errGroup.Go(signalingServer.handleRedisPubSub(ctx, msg.Sender, msg.Room, stream))
				case *proto.SignalingMessage_DiscoverResponse:
					if received, err := signalingServer.redis.Publish(ctx, signalingServer.redisKeyPrefix+":"+msg.Room+":discover:"+*msg.Receiver, msg.Sender).Result(); err != nil {
						return err
					} else {
						log.Printf("peers received discover response: %v", received)
					}
				case *proto.SignalingMessage_SessionOffer:
					payload := &bytes.Buffer{}
					json.NewEncoder(payload).Encode(innerMsg.SessionOffer)

					if received, err := signalingServer.redis.Publish(ctx, signalingServer.redisKeyPrefix+":"+msg.Room+":offer:"+*msg.Receiver, payload.String()).Result(); err != nil {
						return err
					} else {
						log.Printf("peers received discover response: %v", received)
					}
				case *proto.SignalingMessage_SessionAnswer:
					payload := &bytes.Buffer{}
					json.NewEncoder(payload).Encode(innerMsg.SessionAnswer)

					if received, err := signalingServer.redis.Publish(ctx, signalingServer.redisKeyPrefix+":"+msg.Room+":answer:"+*msg.Receiver, payload.String()).Result(); err != nil {
						return err
					} else {
						log.Printf("peers received discover response: %v", received)
					}
				}
			} else {
				return err
			}
		}
	}
}

func (signalingServer SignalingServer) handleRedisPubSub(ctx context.Context, name, room string, stream proto.Signaling_ConnectServer) func() error {
	return func() error {
		pubsub := signalingServer.redis.Subscribe(ctx,
			signalingServer.redisKeyPrefix+":"+room+":discover",
			signalingServer.redisKeyPrefix+":"+room+":discover:"+name,
			signalingServer.redisKeyPrefix+":"+room+":offer:"+name,
			signalingServer.redisKeyPrefix+":"+room+":answer:"+name,
		)
		defer pubsub.Close()

		ch := pubsub.Channel()
		for msg := range ch {
			switch msg.Channel {
			case signalingServer.redisKeyPrefix + ":" + room + ":discover":
				stream.Send(&proto.SignalingMessage{
					Room:    room,
					Sender:  name,
					Message: &proto.SignalingMessage_DiscoverRequest{},
				})
			case signalingServer.redisKeyPrefix + ":" + room + ":discover:" + name:
				stream.Send(&proto.SignalingMessage{
					Room:     room,
					Sender:   name,
					Receiver: &msg.Payload,
					Message:  &proto.SignalingMessage_DiscoverResponse{},
				})
			case signalingServer.redisKeyPrefix + ":" + room + ":offer:" + name:
				sdpMessage := &proto.SDPMessage{}
				json.NewDecoder(strings.NewReader(msg.Payload)).Decode(sdpMessage)

				stream.Send(&proto.SignalingMessage{
					Room:     room,
					Sender:   name,
					Receiver: &msg.Payload,
					Message: &proto.SignalingMessage_SessionOffer{
						SessionOffer: sdpMessage,
					},
				})
			case signalingServer.redisKeyPrefix + ":" + room + ":answer:" + name:
				sdpMessage := &proto.SDPMessage{}
				json.NewDecoder(strings.NewReader(msg.Payload)).Decode(sdpMessage)

				stream.Send(&proto.SignalingMessage{
					Room:     room,
					Sender:   name,
					Receiver: &msg.Payload,
					Message: &proto.SignalingMessage_SessionOffer{
						SessionOffer: sdpMessage,
					},
				})
			}
		}

		return nil
	}
}

func (signalingServer SignalingServer) Connect(stream proto.Signaling_ConnectServer) error {
	ctx, cancel := context.WithCancel(stream.Context())
	defer cancel()

	errGroup := &errgroup.Group{}

	errGroup.Go(signalingServer.handleStream(ctx, errGroup, stream))

	return errGroup.Wait()
}