mailer/delay/delay.go

package delay

import (
	"errors"
	"fmt"
	"sync/atomic"
	"time"
)

var GLOBAL_MAILCOUNT *mailqueue

type mailer struct {
	subject string
	to      string
	body    string
}

// probably easier to do this as sqlite storage selections
type mailqueue struct {
	dirty       atomic.Bool
	size        int
	instant     chan mailer // priority zero
	reminder    chan mailer // priority one
	maintenance chan mailer // priority two
	marketing   chan mailer // priority 3
	errors      int
	maxerrors   int
}

func init() {
	var err error
	GLOBAL_MAILCOUNT, err = NewMailqueue(100, 60, 90, 5)
	if err != nil {
		fmt.Println(err)
	}
}
func NewMailqueue(size int, resetseconds int, sendseconds int, maxerrors int) (*mailqueue, error) {
	m := mailqueue{
		size:        size,
		instant:     make(chan mailer, size),
		reminder:    make(chan mailer, size),
		maintenance: make(chan mailer, size),
		marketing:   make(chan mailer, size),
		maxerrors:   maxerrors,
	}
	if resetseconds < 60 {
		return nil, errors.New("too small of a value")
	}
	if sendseconds < 90 {
		return nil, errors.New("too large of a value")
	}
	go m.BucketDrip(resetseconds)
	go m.BackgroundMail(sendseconds)
	return &m, nil
}
func (m *mailqueue) BucketDrip(resetseconds int) {
	// every 60 seconds
	for range time.Tick(time.Second * time.Duration(resetseconds)) {
		m.dirty.Store(false)
	}
}

func (m *mailqueue) BackgroundMail(sendseconds int) {
	// every 90 seconds (.75*60*24, 1080)
	for range time.Tick(time.Second * time.Duration(sendseconds)) {
		if m.errors > m.maxerrors {
			fmt.Println("too many errors, not sending.")
			return
		}
		var err error
		if m.dirty.Load() != true {
			select {
			case e := <-m.maintenance:
				m.dirty.Store(true)
				err = Send(e)
			default:
				select {
				case e := <-m.maintenance:
					m.dirty.Store(true)
					err = Send(e)
				case e := <-m.reminder:
					m.dirty.Store(true)
					err = Send(e)
				default:
					select {
					case e := <-m.maintenance:
						m.dirty.Store(true)
						err = Send(e)
					case e := <-m.reminder:
						m.dirty.Store(true)
						err = Send(e)
					case e := <-m.marketing:
						m.dirty.Store(true)
						err = Send(e)
					default:
						fmt.Println("queue empty")
					}
				}
			}
		}
		if err != nil {
			// add to failed queue? store as failed?
			m.errors += 1
		}
		err = nil
	}
}
func (m *mailqueue) AddSend(mail mailer, queue string) error {
	var target chan mailer
	switch queue {
	case "maintenance":
		target = m.maintenance
	case "reminder":
		target = m.reminder
	case "marketing":
		target = m.marketing
	default:
		return errors.New("no valid queue")
	}
	if m.size-1 < len(target) {
		return errors.New("mail queue full!")
	}
	select {
	case target <- mail:
	default:
		return errors.New("mail queue full!")
	}
	return nil
}
func Send(m mailer) error {
	fmt.Println(m.to, m.subject, m.body)
	return nil
}