edge/pkg/module/cast/registry.go

package cast

import (
	"context"
	"sync"

	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

type Service interface {
	Scan(ctx context.Context) ([]Device, error)
	Find(ctx context.Context, deviceID string) (Device, error)
	NewClient(ctx context.Context, device Device) (Client, error)
}

type Registry struct {
	index map[DeviceType]Service
}

func (r *Registry) NewClient(ctx context.Context, device Device) (Client, error) {
	deviceType := device.DeviceType()

	srv, exists := r.index[deviceType]
	if !exists {
		return nil, errors.Wrapf(ErrUnknownDeviceType, "device type '%s' is not registered", deviceType)
	}

	client, err := srv.NewClient(ctx, device)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return client, nil
}

func (r *Registry) Find(ctx context.Context, deviceID string) (Device, error) {
	for _, srv := range r.index {
		device, err := srv.Find(ctx, deviceID)
		if err != nil {
			logger.Error(ctx, "could not get device", logger.CapturedE(errors.WithStack(err)))
			continue
		}

		if device != nil {
			return device, nil
		}
	}

	return nil, errors.WithStack(ErrDeviceNotFound)
}

func (r *Registry) Scan(ctx context.Context) ([]Device, error) {
	results := make([]Device, 0)
	errs := make([]error, 0)

	var (
		lock sync.Mutex
		wg   sync.WaitGroup
	)

	wg.Add(len(r.index))

	for _, srv := range r.index {
		func(srv Service) {
			go func() {
				defer wg.Done()

				devices, err := srv.Scan(ctx)
				if err != nil {
					lock.Lock()
					errs = append(errs, errors.WithStack(err))
					lock.Unlock()
				}

				lock.Lock()
				results = append(results, devices...)
				lock.Unlock()
			}()
		}(srv)
	}

	wg.Wait()

	for _, err := range errs {
		logger.Error(ctx, "error occured while scanning", logger.CapturedE(errors.WithStack(err)))
	}

	return results, nil
}

func (r *Registry) Register(deviceType DeviceType, service Service) {
	r.index[deviceType] = service
}

func NewRegistry() *Registry {
	return &Registry{
		index: make(map[DeviceType]Service),
	}
}

var defaultRegistry = NewRegistry()

func NewClient(ctx context.Context, device Device) (Client, error) {
	client, err := defaultRegistry.NewClient(ctx, device)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return client, nil
}

func Scan(ctx context.Context) ([]Device, error) {
	devices, err := defaultRegistry.Scan(ctx)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return devices, nil
}

func Find(ctx context.Context, deviceID string) (Device, error) {
	device, err := defaultRegistry.Find(ctx, deviceID)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return device, nil
}

func Register(deviceType DeviceType, service Service) {
	defaultRegistry.Register(deviceType, service)
}