package service

import (
	"errors"
	"sync"
	"time"

	"src.dualinventive.com/go/dinet"
	"src.dualinventive.com/go/dinet/rpc"
	"src.dualinventive.com/go/lib/dilog"
)

// HeartbeatInterval is the heartbeat interval for the services
const HeartbeatInterval = time.Minute

// Compile-time interface validation
var _ dinet.Device = &Device{}
var _ dinet.ParentDevice = &Device{}

// Device is a service device
type Device struct {
	uid        string
	conn       dinet.DeviceConn
	router     *dinet.Router
	logger     dilog.Logger
	endpoint   string
	appVersion string

	childrenLock sync.RWMutex
	children     map[string]dinet.Device
}

// NewDevice creates a new device which is a service. BackendURI is the URI of SMP to connect to
func NewDevice(logger dilog.Logger, backendURI string, devPrefix string, appVersion string) (*Device, error) {
	con, err := dinet.NewDeviceConn(dinet.TransportLowlevel)
	if err != nil {
		return nil, err
	}

	if err = con.Connect(backendURI); err != nil {
		return nil, err
	}
	uid, err := GenerateUIDFromMac(devPrefix)
	if err != nil {
		return nil, err
	}

	dLogger := logger.WithField("device:uid", uid)
	dLogger.Info("authenticating at SMP")
	if err = con.DeviceHandshake(uid); err != nil {
		dLogger.WithError(err).Error("handshake failed")
		if err2 := con.Close(); err2 != nil {
			dLogger.WithError(err2).Error("failed to close the connection")
		}
		return nil, err
	}

	rtr, err := dinet.NewRouter(logger, con)
	if err != nil {
		return nil, err
	}
	dev := &Device{
		uid:        uid,
		conn:       con,
		router:     rtr,
		logger:     dLogger,
		endpoint:   backendURI,
		appVersion: appVersion,
		children:   make(map[string]dinet.Device),
	}
	rtr.Subscribe(uid, rpc.ClassMethodDeviceData, rpc.MsgTypeRequest, dev.requestDeviceData)
	rtr.Subscribe(uid, rpc.ClassMethodDeviceInfo, rpc.MsgTypeRequest, dev.deviceInfo)
	rtr.Subscribe(uid, rpc.ClassMethodConnectionInfo, rpc.MsgTypeRequest, dev.connectionInfo)
	dev.startBackgroundTasks()
	return dev, nil
}

func (d *Device) startBackgroundTasks() {
	ticker := time.NewTicker(HeartbeatInterval)
	go func() {
		for range ticker.C {
			err := d.sendDeviceData()
			if err != nil {
				d.logger.Fatal("device ping failed")
				return
			}
		}
	}()
	go func() {
		if err := d.router.ListenAndServe(); err != nil {
			d.logger.WithError(err).Error("service: listenAndServe failed")
		}
		err := d.Close()
		if err != nil {
			d.logger.WithError(err).Error("service: cannot close device")
		}
	}()

}

// RegisterUID registers the uid on the connection (dinetlowlevel message type Register)
// DONT use this function, this is for internal use only. Use childdevice.Handshake()
func (d *Device) RegisterUID(uid string) error {
	return d.conn.DeviceRegister(uid)
}

// UnregisterUID unregisters the uid on the connection (dinetlowlevel message type Unregister)
// DONT use this function, this is for internal use only. Use childdevice.Close()
func (d *Device) UnregisterUID(uid string) error {
	d.router.UnsubscribeDevice(uid)
	return d.conn.DeviceUnregister(uid)
}

// RegisterDevice registers a new device on behalf of the current device. The children will be updated with the given
// device
// DONT use this function, this is for internal use only. Use childdevice.Handshake()
func (d *Device) RegisterDevice(device dinet.Device) error {
	d.childrenLock.Lock()
	d.children[device.UID()] = device
	d.childrenLock.Unlock()
	return d.conn.DeviceRegister(device.UID())
}

// UnregisterDevice unregisters a device on behalf of the current device. The children will be updated with the given
// device
// DONT use this function, this is for internal use only. Use childdevice.Close()
func (d *Device) UnregisterDevice(uid string) error {
	d.childrenLock.Lock()
	delete(d.children, uid)
	d.childrenLock.Unlock()
	return d.conn.DeviceUnregister(uid)
}

// Logger returns the logger
func (d *Device) Logger() dilog.Logger {
	return d.logger
}

// send transfers a message for this device to the remote host
func (d *Device) send(m *rpc.Msg) error {
	m.DeviceUID = d.uid
	return d.router.Send(m)
}

// Router returns the router
func (d *Device) Router() *dinet.Router {
	return d.router
}

// requestDeviceData is the callback for device:data
func (d *Device) requestDeviceData(req *rpc.Msg) *rpc.Msg {
	rep := req.CreateReply()
	rep.Result = rpc.NewResult([]rpc.DeviceData{{
		State: rpc.DeviceStateIdle,
		Error: false,
	}})
	return rep
}

// deviceInfo is the callback for device:info
func (d *Device) deviceInfo(req *rpc.Msg) *rpc.Msg {
	rep := req.CreateReply()
	rep.Result = rpc.NewResult([]rpc.DeviceInfo{{
		Type:    rpc.DeviceTypeService,
		Version: rpc.VersionMap{rpc.VersionKeyFwService: d.appVersion},
	}})
	return rep
}

// connectionInfo is the callback for connection:info
func (d *Device) connectionInfo(req *rpc.Msg) *rpc.Msg {
	rep := req.CreateReply()
	rep.Result = rpc.NewResult([]rpc.ConnectionInfo{{
		Timeout:   uint32(HeartbeatInterval.Seconds()),
		Transport: rpc.ConnectionTransportService,
		Service:   &rpc.ConnectionInfoService{Endpoint: d.endpoint},
	}})
	return rep
}

// sendDeviceData publishes the device:data
func (d *Device) sendDeviceData() error {
	return d.send(&rpc.Msg{
		ClassMethod: rpc.ClassMethodDeviceData,
		Type:        rpc.MsgTypePublish,
		Result: rpc.NewResult([]rpc.DeviceData{{
			State: rpc.DeviceStateIdle,
			Error: false,
		}}),
	})
}

// UID returns the UID of this service device
func (d *Device) UID() string {
	return d.uid
}

// Search will search for the UID in the tree below this device
func (d *Device) Search(uid string) (dinet.Device, error) {
	if uid == d.UID() {
		return d, nil
	}

	d.childrenLock.RLock()
	defer d.childrenLock.RUnlock()
	// First find via the direct children (fastest solution)
	for pUID, dev := range d.children {
		if pUID == uid {
			return dev, nil
		}
	}
	// Not found als direct child. Now find in the sub children
	for _, dev := range d.children {
		pDev, ok := dev.(dinet.ParentDevice)
		if !ok {
			continue
		}
		fDev, err := pDev.Search(uid)
		if err == nil {
			return fDev, nil
		}
	}
	return nil, errors.New("not found")
}

// Close closes all the children and closes the connection to SMP
func (d *Device) Close() error {
	d.childrenLock.RLock()
	for _, c := range d.children {
		if err := c.Close(); err != nil {
			d.logger.WithError(err).WithField("child", c.UID()).Error("cannot close child")
		}
	}
	d.childrenLock.RUnlock()
	return d.conn.Close()
}