hswro-alarm-bot/sender_worker.go

package main

import (
	"strings"
	"sync"
	"time"
)

type GenericMessage struct {
	chat_id int64
	msg     string
}

type Sender interface {
	Send(msg GenericMessage) error
}

func tg_sender_worker(tg_events <-chan GenericMessage, s Sender, wg *sync.WaitGroup, messageNotMoreOftenThan time.Duration) {
	wg.Add(1)
	defer wg.Done()
	messagesToSend := make(map[int64]*strings.Builder)
	waitingStarted := false
	timeoutEvents := make(chan interface{})

loop:
	for {
		select {
		case ev, ok := <-tg_events:
			if !ok {
				break loop
			}
			// Collect all messages to send them at once
			_, messageBuilderExists := messagesToSend[ev.chat_id]
			if !messageBuilderExists {
				messagesToSend[ev.chat_id] = &strings.Builder{}
			}
			messagesToSend[ev.chat_id].WriteString(ev.msg)
			messagesToSend[ev.chat_id].WriteRune('\n')
			if !waitingStarted {
				waitingStarted = true
				go func() {
					time.Sleep(messageNotMoreOftenThan)
					timeoutEvents <- nil
				}()
			}
		case <-timeoutEvents:
			waitingStarted = false
			for chat_id, msgBuilder := range messagesToSend {
				err := s.Send(GenericMessage{chat_id, msgBuilder.String()})
				if err != nil {
					// TODO: handle it better
					panic(err)
				}
				delete(messagesToSend, chat_id)
			}
		}
	}

	// If anything is left to be sent, send it now
	for chat_id, msgBuilder := range messagesToSend {
		err := s.Send(GenericMessage{chat_id, msgBuilder.String()})
		if err != nil {
			// TODO: handle it better
			panic(err)
		}
	}
}