package ocsql

import (
	"context"
	"database/sql"
	"sync"
	"time"

	"go.opencensus.io/stats"
)

func RecordStats(db *sql.DB, interval time.Duration) (fnStop func()) {
	var (
		closeOnce sync.Once
		ctx       = context.Background()
		ticker    = time.NewTicker(interval)
		done      = make(chan struct{})
	)

	go func() {
		for {
			select {
			case <-ticker.C:
				dbStats := db.Stats()
				stats.Record(ctx,
					MeasureOpenConnections.M(int64(dbStats.OpenConnections)),
					MeasureIdleConnections.M(int64(dbStats.Idle)),
					MeasureActiveConnections.M(int64(dbStats.InUse)),
					MeasureWaitCount.M(dbStats.WaitCount),
					MeasureWaitDuration.M(float64(dbStats.WaitDuration.Nanoseconds())/1e6),
					MeasureIdleClosed.M(dbStats.MaxIdleClosed),
					MeasureLifetimeClosed.M(dbStats.MaxLifetimeClosed),
				)
			case <-done:
				ticker.Stop()
				return
			}
		}
	}()

	return func() {
		closeOnce.Do(func() {
			close(done)
		})
	}