package scheduler

import (
    "context"
    "log"
    "time"

    "github.com/robfig/cron/v3"
)

// Start runs the cron scheduler until ctx is done.
func Start(ctx context.Context, spec string, job func(now time.Time), logger *log.Logger) error {
    c := cron.New(cron.WithParser(cron.NewParser(cron.SecondOptional|cron.Minute|cron.Hour|cron.Dom|cron.Month|cron.Dow|cron.Descriptor)))
    _, err := c.AddFunc(spec, func() {
        job(time.Now())
    })
    if err != nil {
        return err
    }
    if logger != nil {
        logger.Printf("scheduler started: %s", spec)
    }
    c.Start()
    go func() {
        <-ctx.Done()
        c.Stop()
    }()
    return nil
}