package asterisk

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"github.com/CyCoreSystems/ari/v5"
)

// awaitStasisStart only marks the exact originated channel answered after it
// enters our ARI application. A generic Up event is not proof of media setup.
func awaitStasisStart(ctx context.Context, subscription ari.Subscription, channelID string) error {
	if ctx == nil || subscription == nil || channelID == "" {
		return errors.New("ARI answer subscription and channel identity required")
	}
	recent := make([]string, 0, 8)
	for {
		select {
		case <-ctx.Done():
			return fmt.Errorf("ARI answer deadline or cancellation (recent_events=%s): %w", strings.Join(recent, ","), ctx.Err())
		case event, open := <-subscription.Events():
			if !open {
				return errors.New("ARI event subscription closed before answer")
			}
			if event == nil {
				return errors.New("ARI answer subscription delivered an empty event")
			}
			typ := event.GetType()
			if len(recent) == cap(recent) {
				recent = recent[1:]
			}
			recent = append(recent, typ)
			if !eventBelongsToChannel(event, channelID) {
				continue
			}
			switch typ {
			case "StasisStart":
				if _, ok := event.(*ari.StasisStart); ok {
					return nil
				}
			case "StasisEnd":
				return errors.New("ARI channel left the application before StasisStart")
			case "ChannelHangupRequest":
				if hangup, ok := event.(*ari.ChannelHangupRequest); ok {
					return fmt.Errorf("ARI channel ended before StasisStart: hangup_cause=%d", hangup.Cause)
				}
				return errors.New("ARI channel ended before StasisStart: hangup request")
			case "ChannelDestroyed":
				if destroyed, ok := event.(*ari.ChannelDestroyed); ok {
					return fmt.Errorf("ARI channel ended before StasisStart: destroy_cause=%d", destroyed.Cause)
				}
				return errors.New("ARI channel ended before StasisStart: destroyed")
			}
		}
	}
}

func eventBelongsToChannel(event ari.Event, channelID string) bool {
	for _, key := range event.Keys() {
		if key != nil && key.Kind == "channel" && key.ID == channelID {
			return true
		}
	}
	return false
}