Allow diff file path to be customised

cmd/watcher/main.go

@@ -18,6 +18,7 @@ type flags struct {
 	ticketmasterConfigFile string
 	discordWebhookURL      string
 	diffMode               bool
+	diffFile               string
 }
 
 func main() {
@@ -38,7 +39,8 @@ func main() {
 	}
 
 	reader := ticketmaster.NewReader(f.apiKey)
-	watcher := watcher.NewWatcher(reader, f.ticketmasterConfigFile, artists, f.discordWebhookURL)
+	watcher := watcher.NewWatcher(reader, f.ticketmasterConfigFile, artists,
+		f.discordWebhookURL, f.diffFile)
 	events, err := watcher.FindEvents(f.diffMode)
 	if err != nil {
 		log.Fatalf("Error retrieving events: %v", err)
@@ -68,9 +70,10 @@ func parseFlags() *flags {
 	flag.StringVar(&f.discordWebhookURL, "discordWebhookURL", "", "Discord webhook URL")
 	flag.StringVar(&f.ticketmasterConfigFile, "ticketmasterConfig", "ticketmaster.yaml",
 		"Path to a file containing search criteria for ticketmaster event lookups")
-	flag.BoolVar(&f.diffMode, "diff", false, fmt.Sprintf("Run in diff mode which only notifies "+
-		"for events we haven't already seen. Notification history is stored in the %q file "+
-		"between runs", watcher.DIFF_FILE))
+	flag.BoolVar(&f.diffMode, "diff", false, "Run in diff mode which only notifies "+
+		"for events we haven't already seen.")
+	flag.StringVar(&f.diffFile, "diffFile", "previous-ids", "Path to a file that stores the list "+
+		"of events that we have previously sent notifications for")
 	flag.Parse()
 	return f
 }

internal/watcher/watcher.go

@@ -13,22 +13,22 @@ import (
 	"github.com/RyanConnell/concert-watcher/pkg/ticketmaster"
 )
 
-const DIFF_FILE = "previous-event-ids"
-
 type Watcher struct {
 	ticketmasterAPI        ticketmaster.API
 	ticketmasterConfigFile string
 	trackedArtists         *set.Set[string]
 	discordWebhookURL      string
+	diffFile               string
 }
 
 func NewWatcher(ticketmasterAPI ticketmaster.API, ticketmasterConfigFile string,
-	trackedArtists []string, discordWebhookURL string) *Watcher {
+	trackedArtists []string, discordWebhookURL string, diffFile string) *Watcher {
 	return &Watcher{
 		ticketmasterAPI:        ticketmasterAPI,
 		ticketmasterConfigFile: ticketmasterConfigFile,
 		trackedArtists:         set.New(trackedArtists...),
 		discordWebhookURL:      discordWebhookURL,
+		diffFile:               diffFile,
 	}
 }
 
@@ -126,7 +126,7 @@ func (w *Watcher) Notify(events []*ticketmaster.Event) error {
 
 // Query for a list of events that we've previously notiied on.
 func (w *Watcher) previousEventIDs() ([]string, error) {
-	file, err := os.Open(DIFF_FILE)
+	file, err := os.Open(w.diffFile)
 	if errors.Is(err, fs.ErrNotExist) {
 		return nil, nil
 	}
@@ -145,7 +145,7 @@ func (w *Watcher) previousEventIDs() ([]string, error) {
 
 // Save seen event IDs so that we don't send duplicate notifications each time we run.
 func (w *Watcher) saveEventIDs(ids []string) error {
-	file, err := os.Create(DIFF_FILE)
+	file, err := os.Create(w.diffFile)
 	if err != nil {
 		return err
 	}