package replayhandler

import (
	"context"
	"fmt"
	"log"
	"time"

	"github.com/ituoga/iot/gen"
	"github.com/nats-io/nats.go"
	"google.golang.org/protobuf/proto"
)

// interface
type ReplayHandler interface {
	ApplyEvent(m *gen.EventEnvelope) error
	ApplyCommand(ctx context.Context, m *gen.CommandEnvelope) ([]*gen.EventEnvelope, error)
}

func Replay(ctx context.Context, js nats.JetStreamContext, aggregate, id string, fn ReplayHandler) {
	lctx, cancel := context.WithCancel(ctx)
	msgs := make(chan *nats.Msg, 128)
	sub, _ := js.ChanSubscribe(fmt.Sprintf("events.%s.%s.>", aggregate, id), msgs, nats.DeliverAll(), nats.ManualAck())
	defer close(msgs)
	defer sub.Unsubscribe()
	delay := 1000 * time.Millisecond

	go func() {
		waiter := time.NewTimer(delay)
		for {
			select {
			case <-ctx.Done():
				cancel()
				return
			case <-waiter.C:
				cancel()
				return
			case msg := <-msgs:
				waiter.Reset(200 * time.Second)
				if msg == nil {
					continue
				}
				var event = &gen.EventEnvelope{}
				err := proto.Unmarshal(msg.Data, event)
				if err != nil {
					log.Printf("Replay handler error: %v", err)
				}
				fn.ApplyEvent(event)
				msg.Ack()
			}
		}
	}()
	<-lctx.Done()
}