package telemetry

import (
	"context"
	"errors"

	"galaxy/gateway/internal/push"

	"go.opentelemetry.io/otel/attribute"
)

// PushObserver adapts Runtime to the push.Observer interface.
type PushObserver struct {
	runtime *Runtime
}

// NewPushObserver constructs a push stream observer backed by runtime.
func NewPushObserver(runtime *Runtime) *PushObserver {
	return &PushObserver{runtime: runtime}
}

// Registered records one active push stream.
func (o *PushObserver) Registered(_ push.StreamBinding) {
	if o == nil || o.runtime == nil {
		return
	}

	o.runtime.AddActivePushStream(context.Background(), 1)
}

// Unregistered records one active-stream decrement and one closure reason for
// hub-enforced shutdown, overflow, or revocation.
func (o *PushObserver) Unregistered(_ push.StreamBinding, err error) {
	if o == nil || o.runtime == nil {
		return
	}

	o.runtime.AddActivePushStream(context.Background(), -1)

	switch {
	case errors.Is(err, push.ErrSubscriptionOverflow):
		o.runtime.RecordPushStreamClosure(context.Background(), attribute.String("reason", "overflow"))
	case errors.Is(err, push.ErrSubscriptionRevoked):
		o.runtime.RecordPushStreamClosure(context.Background(), attribute.String("reason", "revoked"))
	case errors.Is(err, push.ErrHubShuttingDown):
		o.runtime.RecordPushStreamClosure(context.Background(), attribute.String("reason", "shutdown"))
	}
}