// Package signaler implements a signaler server.
package signaler

import (
	"context"
	"encoding/base64"
	"fmt"
	"strings"
	"sync"
	"time"

	"connectrpc.com/connect"
	pb "github.com/chathaway-codes/home-sensors/v2/gen"
	internalpb "github.com/chathaway-codes/home-sensors/v2/gen/token"
	"github.com/gofrs/uuid/v5"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
	"google.golang.org/protobuf/proto"
)

type camera struct {
	id string
}

type session struct {
	id         string
	cameraID   string
	createTime time.Time
	toCamera   chan *pb.IceMessage
	toClient   chan *pb.IceMessage
}

type Server struct {
	mu            sync.Mutex
	camerasByHome map[string]map[string]*camera

	sessionsByCamera map[string]chan *session
	sessionsById     map[string]*session
}

func New() *Server {
	s := &Server{
		camerasByHome:    make(map[string]map[string]*camera),
		sessionsByCamera: make(map[string]chan *session),
		sessionsById:     make(map[string]*session),
	}
	go s.cleanup()
	return s
}

func (s *Server) CreateAuthToken(ctx context.Context, request *connect.Request[pb.CreateAuthTokenRequest]) (*connect.Response[pb.AuthToken], error) {
	req := request.Msg

	var id string
	switch req.Type.(type) {
	case *pb.CreateAuthTokenRequest_Camera_:
		id = req.GetCamera().GetId()
		s.mu.Lock()
		thisCamera := &camera{
			id: id,
		}
		home := req.GetHome()
		if _, ok := s.camerasByHome[home]; !ok {
			s.camerasByHome[home] = make(map[string]*camera)
		}
		s.camerasByHome[home][id] = thisCamera
		if _, ok := s.sessionsByCamera[id]; !ok {
			s.sessionsByCamera[id] = make(chan *session, 100)
		}
		s.mu.Unlock()
	case *pb.CreateAuthTokenRequest_Client_:
		myUUID, err := uuid.NewV4()
		if err != nil {
			return nil, fmt.Errorf("error creating UUID: %v", err)
		}
		id = myUUID.String()
	}

	token := &internalpb.AuthToken{
		Uid:  id,
		Home: req.GetHome(),
	}
	bytes, err := proto.Marshal(token)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "failed to generate token: %v", err)
	}
	outToken := base64.URLEncoding.EncodeToString(bytes)
	return connect.NewResponse(&pb.AuthToken{
		Token: outToken,
	}), nil
}

func (s *Server) ListCameras(ctx context.Context, request *connect.Request[pb.ListCamerasRequest]) (*connect.Response[pb.ListCamerasResponse], error) {
	authToken, err := getAuthToken(request)
	if err != nil {
		return nil, err
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	var cameras []*pb.Camera
	for _, camera := range s.camerasByHome[authToken.Home] {
		cameras = append(cameras, &pb.Camera{
			Identifier: &pb.Camera_Identifier{
				Id: camera.id,
			},
		})
	}
	return connect.NewResponse(&pb.ListCamerasResponse{Cameras: cameras}), nil
}

// CreateSession creates a new session that can be seen bv the provided Camera and Peer.
//
// Optionally, wait_for_update can be set to prevent returning until the Camera has seen the
// session request, populated candidates, and returned a session offer.
func (s *Server) CreateSession(ctx context.Context, request *connect.Request[pb.CreateSessionRequest]) (*connect.Response[pb.Session], error) {
	thisSession := request.Msg.Session
	if thisSession == nil {
		return nil, status.Errorf(codes.InvalidArgument, "nil session")
	}

	myUUID, err := uuid.NewV4()
	if err != nil {
		return nil, fmt.Errorf("error creating UUID: %v", err)
	}
	id := myUUID.String()
	thisSession.Id = &pb.Session_Identifier{Id: id}
	cameraID := thisSession.GetCamera().GetId()
	s.mu.Lock()
	defer s.mu.Unlock()

	sess := &session{
		id:         id,
		cameraID:   cameraID,
		createTime: time.Now(),
		toCamera:   make(chan *pb.IceMessage, 100),
		toClient:   make(chan *pb.IceMessage, 100),
	}
	s.sessionsByCamera[cameraID] <- sess
	s.sessionsById[id] = sess

	return connect.NewResponse(thisSession), nil
}

func (s *Server) PopSession(ctx context.Context, request *connect.Request[pb.PopSessionRequest]) (*connect.Response[pb.Session], error) {
	authToken, err := getAuthToken(request)
	if err != nil {
		return nil, err
	}

	s.mu.Lock()

	if _, ok := s.camerasByHome[authToken.Home]; !ok {
		return nil, status.Errorf(codes.NotFound, "home %q not found", authToken.Home)
	}
	if _, ok := s.camerasByHome[authToken.Home][authToken.Uid]; !ok {
		return nil, status.Errorf(codes.Unauthenticated, "you are not a camera")
	}

	ch := s.sessionsByCamera[authToken.Uid]
	s.mu.Unlock()

	sess := <-ch

	return connect.NewResponse(&pb.Session{
		Id: &pb.Session_Identifier{
			Id: sess.id,
		},
	}), nil
}

func (s *Server) CreateIceMessage(ctx context.Context, request *connect.Request[pb.CreateIceMessageRequest]) (*connect.Response[pb.IceMessage], error) {
	authToken, err := getAuthToken(request)
	if err != nil {
		return nil, err
	}
	req := request.Msg

	s.mu.Lock()
	defer s.mu.Unlock()

	session, ok := s.sessionsById[req.GetSessionIdentifier().GetId()]
	if !ok {
		return nil, status.Errorf(codes.NotFound, "unknown session")
	}

	if _, ok := s.camerasByHome[authToken.Home]; !ok {
		return nil, status.Errorf(codes.NotFound, "home %q not found", authToken.Home)
	}
	_, isCamera := s.camerasByHome[authToken.Home][authToken.Uid]

	session.createTime = time.Now()
	msg := req.GetIceMessage()
	if isCamera {
		session.toClient <- msg
	} else {
		session.toCamera <- msg
	}
	return connect.NewResponse(msg), nil
}

func (s *Server) PopIceMessage(ctx context.Context, request *connect.Request[pb.PopIceMessageRequest]) (*connect.Response[pb.IceMessage], error) {
	authToken, err := getAuthToken(request)
	if err != nil {
		return nil, err
	}
	req := request.Msg

	s.mu.Lock()

	if _, ok := s.camerasByHome[authToken.Home]; !ok {
		return nil, status.Errorf(codes.NotFound, "home %q not found", authToken.Home)
	}
	_, isCamera := s.camerasByHome[authToken.Home][authToken.Uid]
	session := s.sessionsById[req.GetSessionIdentifier().GetId()]
	session.createTime = time.Now()
	s.mu.Unlock()

	var msg *pb.IceMessage
	if isCamera {
		msg = <-session.toCamera
	} else {
		msg = <-session.toClient
	}
	return connect.NewResponse(msg), nil
}

func (s *Server) cleanup() {
	ticker := time.NewTicker(time.Minute * 5)
	for t := range ticker.C {
		func() {
			s.mu.Lock()
			defer s.mu.Unlock()

			// Look for any stale sessions
			staleSessionsByCamera := make(map[string]*session)
			for _, session := range s.sessionsById {
				if t.Sub(session.createTime) > time.Minute {
					if prev, ok := staleSessionsByCamera[session.cameraID]; ok {
						// Only use this session if it was created after the previous one
						if prev.createTime.Before(session.createTime) {
							staleSessionsByCamera[session.cameraID] = session
						}
					} else {
						staleSessionsByCamera[session.cameraID] = session
					}
				}
			}

			for camera, lastSession := range staleSessionsByCamera {
				// Consume from the chanel until we remove all stale sessions
				for sess := range s.sessionsByCamera[camera] {
					if sess == lastSession {
						// We consumed all stale channels; break
						break
					}
				}
			}
		}()
	}
}

func getAuthToken[T any](req *connect.Request[T]) (*internalpb.AuthToken, error) {
	authHeader := req.Header().Get("Authorization")
	if !strings.HasPrefix(authHeader, "Bearer ") {
		return nil, fmt.Errorf("invalid authorization token")
	}
	authHeader = authHeader[len("Bearer "):]
	bytes, err := base64.URLEncoding.DecodeString(authHeader)
	if err != nil {
		return nil, status.Errorf(codes.InvalidArgument, "malformed authorization header (extract)")
	}
	authToken := &internalpb.AuthToken{}
	if err := proto.Unmarshal(bytes, authToken); err != nil {
		return nil, status.Errorf(codes.InvalidArgument, "malformed authorization header (parse)")
	}
	return authToken, nil
}