package server

import (
	"fmt"
	"log/slog"
	"time"

	"github.com/prometheus/client_golang/prometheus"
)

type Metrics struct {
	logger   *slog.Logger
	notes    prometheus.Gauge
	db       *Database
	reg      *prometheus.Registry
	interval int
}

func NewMetrics(logger *slog.Logger, reg *prometheus.Registry, config *Config, db *Database) (*Metrics, error) {
	l := logger.With("module", "metrics")
	m := &Metrics{
		logger: l,
		db:     db,
		notes: prometheus.NewGauge(prometheus.GaugeOpts{
			Name: config.PrometheusNotesMetric,
		}),
		reg:      reg,
		interval: config.ObservationInterval,
	}
	if err := reg.Register(m.notes); err != nil {
		return nil, err
	}

	go m.ObserveThread()

	return m, nil
}

func (m *Metrics) ObserveThread() {
	m.logger.Debug("starting observations")
	for {
		m.logger.Debug("counting notes")
		var count int64
		m.db.db.Model(&Note{}).Count(&count)
		m.notes.Set(float64(count))
		m.logger.Debug("counted notes", slog.Any("count", count))

		wording := "second"
		if m.interval > 1 {
			wording += "s"
		}
		m.logger.Debug(fmt.Sprintf("waiting for %d %s before next observation", m.interval, wording))
		time.Sleep(time.Duration(m.interval) * time.Second)
	}
}