package pulsar

import (
	"context"

	"github.com/apache/pulsar-client-go/pulsar"

	"github.com/milvus-io/milvus/pkg/v2/streaming/util/types"
	"github.com/milvus-io/milvus/pkg/v2/streaming/walimpls"
	"github.com/milvus-io/milvus/pkg/v2/streaming/walimpls/helper"
)

const (
	truncateCursorSubscriptionName = "truncate-cursor"
)

var _ walimpls.OpenerImpls = (*openerImpl)(nil)

// openerImpl is the opener for pulsar wal.
type openerImpl struct {
	c pulsar.Client
}

// Open opens a wal instance.
func (o *openerImpl) Open(ctx context.Context, opt *walimpls.OpenOption) (walimpls.WALImpls, error) {
	if err := opt.Validate(); err != nil {
		return nil, err
	}
	var p pulsar.Producer
	if opt.Channel.AccessMode == types.AccessModeRW {
		var err error
		p, err = o.c.CreateProducer(pulsar.ProducerOptions{
			Topic: opt.Channel.Name,
			// TODO: current go pulsar client does not support fencing, we should enable it after go pulsar client supports it.
			// ProducerAccessMode: pulsar.ProducerAccessModeExclusiveWithFencing,
		})
		if err != nil {
			return nil, err
		}

		// Initialize a persistent cursor to protect the topic from being retention.
		cursor, err := o.c.Subscribe(pulsar.ConsumerOptions{
			Topic:                       opt.Channel.Name,
			SubscriptionName:            truncateCursorSubscriptionName,
			Type:                        pulsar.Exclusive,
			MaxPendingChunkedMessage:    1,
			SubscriptionInitialPosition: pulsar.SubscriptionPositionEarliest,
		})
		if err != nil {
			return nil, err
		}
		cursor.Close()
	}
	return &walImpl{
		WALHelper: helper.NewWALHelper(opt),
		p:         p,
		c:         o.c,
	}, nil
}

// Close closes the opener resources.
func (o *openerImpl) Close() {
	o.c.Close()
}