type Cache interface {
	Set(ctx context.Context, key, value []byte) error
	Get(ctx context.Context, key []byte) (value []byte, err error)
}

type CacheTracer struct {
	next   Cache
	prefix string
}

func NewCacheTracer(next Cache, prefix string) *CacheTracer {
	return &CacheTracer{
		next:   next,
		prefix: prefix,
	}
}

func (t *CacheTracer) Get(in context.Context, in1 []byte) (out []byte, out1 error) {
	span, in := opentracing.StartSpanFromContext(in, t.prefix+".Cache.Get")
	defer func() {
		if out1 != nil {
			ext.Error.Set(span, true)
			span.LogFields(
				log.String("event", "error"),
				log.String("message", out1.Error()),
			)
		}
		span.Finish()
	}()

	return t.next.Get(in, in1)
}

func (t *CacheTracer) Set(in context.Context, in1 []byte, in2 []byte) (out error) {
	span, in := opentracing.StartSpanFromContext(in, t.prefix+".Cache.Set")
	defer func() {
		if out != nil {
			ext.Error.Set(span, true)
			span.LogFields(
				log.String("event", "error"),
				log.String("message", out.Error()),
			)
		}
		span.Finish()
	}()

	return t.next.Set(in, in1, in2)
}