Improved handling of errors and included manual refreshing

Signed-off-by: Marcus Noble <github@marcusnoble.co.uk>

main.go

@@ -28,24 +28,58 @@ func init() {
 
 func main() {
 	latestBooks := map[string]*storygraph.Book{}
-	go func() {
-		var err error
-		for {
-			latestBooks, err = storygraph.GetLatestBooks()
-			if err != nil {
-				fmt.Println("Error fetching latest books:", err)
-				return
+	refreshingBooks := true
+	var lastUpdated *time.Time
+
+	updateBooks := func() {
+		refreshingBooks = true
+		defer func() { refreshingBooks = false }()
+		newBookList, err := storygraph.GetLatestBooks()
+		if err != nil {
+			fmt.Println("Error fetching latest books:", err)
+			return
+		}
+
+		// Update each category individually with books we have managed to find
+		for cat, book := range newBookList {
+			if b, ok := newBookList[cat]; ok && b != nil {
+				latestBooks[cat] = book
 			}
+		}
+		now := time.Now()
+		lastUpdated = &now
+		fmt.Println("Updated latest book recommendations")
+	}
 
-			fmt.Println("Updated latest book recommendations")
-
+	go func() {
+		for {
+			updateBooks()
 			time.Sleep(1 * time.Hour)
 		}
 	}()
 
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		type data struct {
+			Books       map[string]*storygraph.Book
+			LastUpdated string
+			Refreshing  bool
+		}
+		d := data{
+			Books:       latestBooks,
+			LastUpdated: "",
+			Refreshing:  refreshingBooks,
+		}
+		if lastUpdated != nil {
+			d.LastUpdated = lastUpdated.Format(time.RFC1123)
+		}
 		tmpl := template.Must(template.ParseFiles("templates/index.html"))
-		tmpl.Execute(w, latestBooks)
+		tmpl.Execute(w, d)
+	})
+	http.HandleFunc("/refresh", func(w http.ResponseWriter, r *http.Request) {
+		go updateBooks()
+		w.Header().Set("Location", "/")
+		w.Header().Set("Refresh", "0; url=/")
+		w.Write([]byte("Refreshing..."))
 	})
 	http.Handle("/assets/", http.StripPrefix("/assets/", http.FileServer(http.Dir("assets"))))
 	http.ListenAndServe(fmt.Sprintf(":%s", port), nil)