package logmower

import (
	"context"
	"log"
	"time"

	ms "git.k-space.ee/k-space/logmower-shipper/pkg/mongo_struct"
	"github.com/jtagcat/util"
	prom "github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
	"go.mongodb.org/mongo-driver/mongo"
)

var (
	promShipperQueued = promauto.NewGaugeVec(prom.GaugeOpts{
		Namespace: PrometheusPrefix,
		// Subsystem: "shipper",
		Name: "shipper_record", //      "queued",
		Help: "Log records in queue to be batched and sent to database",
	}, []string{"filename"})
	promShipperDbSent = promauto.NewCounterVec(prom.CounterOpts{
		Namespace: PrometheusPrefix,
		// Subsystem: "shipper",
		Name: "record", // "sent",
		Help: "Log records successfully committed to database",
	}, []string{"filename"})
	promShipperBatchSizeResult = promauto.NewHistogram(prom.HistogramOpts{
		Namespace: PrometheusPrefix,
		// Subsystem: "shipper",
		Name:    "bulk_submission_message", // "items_in_batch"
		Help:    "Batch size for database submissions",
		Buckets: []float64{1, 5, 10, 50, 100, 500, 1000, 5000, 10000},
	})
	promShipperDbSendError = promauto.NewCounterVec(prom.CounterOpts{
		Namespace: PrometheusPrefix,
		// Subsystem: "shipper",
		Name: "insertion_error",                     // "errors",
		Help: "Errors while submitting to database", // TODO:
	}, []string{"filename"})
	promShipperSynced = promauto.NewGaugeVec(prom.GaugeOpts{
		Namespace: PrometheusPrefix,
		Subsystem: "shipper",
		Name:      "batches_synced",
		Help:      "All batches available have been committed database (0 or 1)",
	}, []string{"filename"})
)

const (
	MaxBatchItems = 10000
	MaxBatchTime  = 5 * time.Second
)

type queueT <-chan ms.Record

func (queue queueT) sender(db *mongo.Collection, metricsFilename string) {
	batched := make(chan []ms.Record)

	// batcher and queue metrics
	go func() {
		ctx, cancel := context.WithCancel(context.Background())
		defer cancel()

		go func() {
			for {
				promShipperQueued.WithLabelValues(metricsFilename).Set(float64(
					len(queue)))

				timer := time.NewTimer(time.Second)
				select {
				case <-ctx.Done():
					return
				case <-timer.C:
				}
			}
		}()

		util.Batch(MaxBatchItems, MaxBatchTime, queue, batched)
		// returns when sendQueue is closed
	}()

	for {
		promShipperSynced.WithLabelValues(metricsFilename).Set(1)

		batch, ok := <-batched
		if !ok {
			return
		}
		promShipperBatchSizeResult.Observe(float64(len(batch)))

		promShipperSynced.WithLabelValues(metricsFilename).Set(0)

		var batchBson []interface{} // mongo does not like typing
		for _, b := range batch {
			batchBson = append(batchBson, b.ToBson())
		}

		result, err := db.InsertMany(mongoTimeoutCtx(context.Background()), batchBson, nil)
		if err != nil {
			promShipperDbSendError.WithLabelValues(metricsFilename).Add(1)
			log.Printf("failure in batch submit to database: %e", err) // TODO: add some selective retry here or something, better error handling
			continue
		}

		promShipperDbSent.WithLabelValues(metricsFilename).Add(float64(
			len(result.InsertedIDs)))
	}
}