package etcdutil

import (
	"context"
	"time"

	"github.com/coreos/etcd/clientv3"
	"github.com/juju/errors"
	"github.com/ngaut/log"
)

const (
	requestTimeout  = 10 * time.Second
	slowRequestTime = 1 * time.Second
)

// SlowLogTxn wraps etcd transaction and log slow one.
type SlowLogTxn struct {
	clientv3.Txn
	cancel context.CancelFunc
}

// NewSlowLogTxn returns a SlowLogTxn
func NewSlowLogTxn(client *clientv3.Client) clientv3.Txn {
	ctx, cancel := context.WithTimeout(client.Ctx(), requestTimeout)
	return &SlowLogTxn{
		Txn:    client.Txn(ctx),
		cancel: cancel,
	}
}

// If implements clientv3.Txn If interface
func (t *SlowLogTxn) If(cs ...clientv3.Cmp) clientv3.Txn {
	return &SlowLogTxn{
		Txn:    t.Txn.If(cs...),
		cancel: t.cancel,
	}
}

// Then implements clientv3.Txn Then interface
func (t *SlowLogTxn) Then(ops ...clientv3.Op) clientv3.Txn {
	return &SlowLogTxn{
		Txn:    t.Txn.Then(ops...),
		cancel: t.cancel,
	}
}

// Commit implements clientv3.Txn Commit interface.
func (t *SlowLogTxn) Commit() (*clientv3.TxnResponse, error) {
	start := time.Now()
	resp, err := t.Txn.Commit()
	t.cancel()

	cost := time.Now().Sub(start)
	if cost > slowRequestTime {
		log.Warnf("txn runs too slow, resp: %v, err: %v, cost: %s", resp, err, cost)
	}

	return resp, errors.Trace(err)
}