main.go

package main

import (
	"flag"
	"os"
	"os/signal"
	"time"

	"github.com/ptgott/one-newsletter/scrape"
	"github.com/ptgott/one-newsletter/userconfig"

	"github.com/rs/zerolog"
	"github.com/rs/zerolog/log"
)

func main() {
	// Log with filename and line number. This writes to stderr, so it should
	// be thread safe.
	// https://github.com/rs/zerolog/blob/7ccd4c940bf8a02fcc5f10e5475f9d3daff04d57/log/log.go#L13
	log.Logger = log.With().Caller().Logger()

	// Intercept interrupts so we can get more visibility into them.
	// One goroutine listens exclusively for interrupts so we can
	// handle them before the main application loop in case of
	// setup issues.
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, os.Interrupt)
	go func(c chan os.Signal) {
		<-sigCh
		log.Info().Msg("interrupt: exiting")
		os.Exit(0)
	}(sigCh)

	configPath := flag.String(
		"config",
		"./config.yaml",
		"Path to a JSON or YAML file containing your configuration.",
	)
	testMode := flag.Bool(
		"test",
		false,
		"Print the HTML body of a single email to stdout and exit without sending it to test a configuration locally. Does not require an SMTP configuration or database.",
	)
	oneOff := flag.Bool(
		"oneoff",
		false,
		"Run the scrapers and send a single email. Used for testing a live One Newsletter deployment. Does not touch the database.",
	)
	level := flag.String(
		"level",
		"",
		`log level: "error", "info", "debug", or "warn"`,
	)
	flag.Parse()

	switch *level {
	case "debug":
		log.Logger = log.Logger.Level(zerolog.DebugLevel)
	case "warn":
		log.Logger = log.Logger.Level(zerolog.WarnLevel)
	case "error":
		log.Logger = log.Logger.Level(zerolog.ErrorLevel)
	case "info":
		log.Logger = log.Logger.Level(zerolog.InfoLevel)
	default:
		// Disable logging in test mode unless the user provides the
		// "level" flag.
		if *testMode {
			log.Logger = log.Logger.Level(zerolog.Disabled)
		} else {
			log.Logger = log.Logger.Level(zerolog.InfoLevel)
		}
	}

	log.Info().
		Str("configPath", *configPath).
		Msg("starting the application")

	f, err := os.Open(*configPath)

	if err != nil {
		log.Error().
			Str("config-path", *configPath).
			Err(err).
			Msg("We can't open the application config file")
		os.Exit(1)
	}

	config, err := userconfig.Parse(f)

	if err != nil {
		log.Error().
			Err(err).
			Msg("Problem parsing your config")
		os.Exit(1)
	}
	config.Scraping.OneOff = *oneOff
	config.Scraping.TestMode = *testMode

	checkedConfig, err := config.CheckAndSetDefaults()
	if err != nil {
		log.Error().
			Err(err).
			Msg("Problem validating your config")
		os.Exit(1)
	}

	log.Info().Str("configPath", *configPath).Msg("successfully validated the config")

	scrapeCadence := time.NewTicker(config.Scraping.Interval)
	scrapeConfig := scrape.Config{
		TickCh:   scrapeCadence.C,
		OutputWr: os.Stdout, // write to stdout if the -no-email flag is given
	}

	if err := scrape.StartLoop(&scrapeConfig, &checkedConfig); err != nil {
		log.Error().Err(err).Msg("error gathering links to email")
	}
}