package metric

import (
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"time"

	"github.com/prometheus/client_golang/prometheus"

	"edge-infra.dev/pkg/edge/datasync/internal/config"
	"edge-infra.dev/pkg/edge/datasync/internal/outbox"
	"edge-infra.dev/pkg/lib/fog"
)

var outboxMessagesGauge = prometheus.NewGaugeVec(
	prometheus.GaugeOpts{
		Name: "data_sync_messaging_num_of_messages_in_outbox_gauge",
		Help: "number of messages in data-sync-messaging outboxes",
	},
	[]string{"outbox"})

var outboxMessagesSizeHistogram = prometheus.NewHistogramVec(
	prometheus.HistogramOpts{
		Name: "data_sync_messaging_size_of_messages_in_outbox",
		Help: "size of messages in data-sync-messaging outboxes by message type",
		// Buckets of 1KB 10KB 100KB 1MB 10MB
		Buckets: prometheus.ExponentialBuckets(1024, 10, 5),
	},
	[]string{"outbox", "type", "partition"})

type outboxMessagesMetric struct {
	chirpConfig *config.Config
}

func NewOutboxMessagesMetric(chirpConfig *config.Config) Metric {
	prometheus.MustRegister(outboxMessagesGauge)
	prometheus.MustRegister(outboxMessagesSizeHistogram)

	return &outboxMessagesMetric{chirpConfig: chirpConfig}
}

func (s *outboxMessagesMetric) StartRecording() {
	logger := fog.New()

	logger.Info("starting to record metrics...")
	outboxPath := config.GetOutboxPath(s.chirpConfig)
	messageTypes := config.GetRoutes(s.chirpConfig)

	for {
		// TODO: we might need to rework this logic down the road
		outboxMessagesSizeHistogram.Reset()
		for _, messageType := range messageTypes {
			count := countMessages(outboxPath, messageType)
			outboxMessagesGauge.WithLabelValues(messageType).Set(float64(count))
		}

		time.Sleep(15 * time.Second)
	}
}

func countMessages(outboxPath, messageType string) int {
	rootPath := fmt.Sprintf("%s/%s", outboxPath, messageType)
	logger := fog.New()

	count := 0

	err := filepath.Walk(rootPath, func(path string, f os.FileInfo, _ error) error {
		if f != nil && !f.IsDir() {
			r, err := regexp.MatchString(".msg", f.Name())
			if err == nil && r {
				count++
				partition := filepath.Base(filepath.Dir(path))
				outboxMessagesSizeHistogram.
					WithLabelValues(messageType, outbox.GetFileMessageType(f), partition).
					Observe(float64(f.Size()))
			}
		}
		return nil
	})

	if err != nil {
		logger.Error(err, "failed to count .dsm messages")
	}

	return count
}