telegram-notifier/notifier/listener/listener.go

package listener

import (
	"context"
	"errors"
	"fmt"
	"io/ioutil"
	"net"
	"net/http"
	"os"
)

type Listener struct {
	ctx        context.Context
	cancel     context.CancelFunc
	httpSrv    *http.Server
	exportChan chan string
	errorChan  chan error
	listener   net.Listener
	handler    *http.ServeMux
}

func New(sockPath string) (*Listener, error) {
	if err := os.Remove(sockPath); err != nil && !errors.Is(err, os.ErrNotExist) {
		return nil, fmt.Errorf("failed to cleanup previously existing socket: %w", err)
	}

	sock, err := net.Listen("unix", sockPath)
	if err != nil {
		return nil, fmt.Errorf("failed to create unix socket: %w", err)
	}
	if err := os.Chmod(sockPath, 0o777); err != nil {
		return nil, fmt.Errorf("failed to set permissions to unix socket: %w", err)
	}

	m := http.NewServeMux()

	return &Listener{
		handler: m,
		httpSrv: &http.Server{
			Handler: m,
		},
		listener:   sock,
		exportChan: make(chan string, 10),
		errorChan:  make(chan error, 10),
	}, nil
}

func (l *Listener) initMux() {
	l.handler.HandleFunc("/", l.sendMessageHandler)
}

func (l *Listener) Run(ctx context.Context) {
	l.ctx, l.cancel = context.WithCancel(ctx)
	l.initMux()
	if err := l.httpSrv.Serve(l.listener); err != nil {
		l.errorChan <- fmt.Errorf("failed to serve HTTP server: %w", err)
	}
}

func (l *Listener) sendMessage(message string) {
	l.exportChan <- message
}

func (l *Listener) sendMessageHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		w.WriteHeader(http.StatusMethodNotAllowed)
		return
	}

	// TODO: use max length instead of writing everything
	bod, err := ioutil.ReadAll(r.Body)
	if err != nil {
		l.errorChan <- fmt.Errorf("failed to read body: %w", err)
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	l.sendMessage(string(bod))
	w.WriteHeader(http.StatusOK)
}

func (l *Listener) ExportChan() <-chan string {
	return l.exportChan
}

func (l *Listener) ErrorChan() <-chan error {
	return l.errorChan
}