Add progress indicator/animation

main.go

@@ -1,6 +1,6 @@
 // Meetup Invite 2000
 // @author: Abner Coimbre <abner@handmadecities.com>
-// Copyright (c) 2024 Handmade Cities
+// Copyright (c) Handmade Cities LLC
 
 // Based off News Blaster 2000 from the Handmade Network: https://git.handmade.network/hmn/newsblaster2000
 
@@ -12,7 +12,7 @@
 //  Jack Punter (@TarriestPython)
 //
 // Emotional Support
-//  Cucui Ganon Rosario
+//  Cucui Ganon Rosario: https://www.youtube.com/watch?v=bvCsTca0uBc
 // =========================================================================
 
 package main
@@ -113,7 +113,7 @@ func retrieveSubscribers(cfg *Config) ([]string, error) {
 		return nil, errors.New("response format error: 'emails' field not found")
 	}
 
-    /* De-duplicate emails using a map */
+	/* De-duplicate emails using a map */
 	/* *** */
 	emailMap := make(map[string]bool)
 	for _, email := range emails {
@@ -282,12 +282,12 @@ func blastMail(cfg *Config, logFile string, trackingFile string, audience []stri
 		}
 	}
 
-    existingReaderCount := len(sentToAddresses)
-    newReaderCount := 0
+	existingReaderCount := len(sentToAddresses)
+	newReaderCount := 0
 
-    if existingReaderCount > 0 {
-        fmt.Println("Same email file specified: Sending only to new subscribers...")
-    }
+	if existingReaderCount > 0 {
+		fmt.Println("Same email file specified: Sending only to new subscribers...")
+	}
 
 	var group []string
 	for _, a := range audience {
@@ -306,15 +306,19 @@ func blastMail(cfg *Config, logFile string, trackingFile string, audience []stri
 			if len(group) == cfg.BatchSize {
 				results, err := sendMail(cfg, group, subject, body)
 				if err != nil {
-					fmt.Printf("Error while sending mail: %v\n", err)
 					return
 				}
 				sentToAddresses = append(sentToAddresses, group...)
 				os.WriteFile(trackingFile, []byte(strings.Join(sentToAddresses, "\n")), 0666)
+				var failed []string
 				for i, res := range results {
 					log.WriteString(fmt.Sprintf("%s: %s\n", group[i], res.Message))
+					if res.ErrorCode != 0 {
+						failed = append(failed, group[i])
+					}
 				}
-                newReaderCount += len(group)
+				printBatchSummary(group, failed)
+				newReaderCount += len(group)
 				group = group[0:0]
 			}
 		}
@@ -322,25 +326,29 @@ func blastMail(cfg *Config, logFile string, trackingFile string, audience []stri
 	if len(group) > 0 {
 		results, err := sendMail(cfg, group, subject, body)
 		if err != nil {
-			fmt.Printf("Error while sending mail: %v\n", err)
 			return
 		}
 		sentToAddresses = append(sentToAddresses, group...)
 		os.WriteFile(trackingFile, []byte(strings.Join(sentToAddresses, "\n")), 0666)
+		var failed []string
 		for i, res := range results {
 			log.WriteString(fmt.Sprintf("%s: %s\n", group[i], res.Message))
+			if res.ErrorCode != 0 {
+				failed = append(failed, group[i])
+			}
 		}
-        newReaderCount += len(group)
+		printBatchSummary(group, failed)
+		newReaderCount += len(group)
 	}
 
-    if newReaderCount > 0 {
-        newSubscribers := existingReaderCount > 0
-        if newSubscribers {
-            fmt.Printf("Sent to %d new subscribers!\n", newReaderCount)
-        }
-    } else {
-        fmt.Printf("Not sent (no new subscribers)\n")
-    }
+	if newReaderCount > 0 {
+		newSubscribers := existingReaderCount > 0
+		if newSubscribers {
+			fmt.Printf("Sent to %d new subscribers!\n", newReaderCount)
+		}
+	} else {
+		fmt.Printf("Not sent (no new subscribers)\n")
+	}
 }
 
 var postmarkClient = http.Client{}
@@ -369,8 +377,47 @@ type PostmarkBatchResult struct {
 	Message   string `json:"Message"`
 }
 
+func printBatchSummary(sent, failed []string) {
+	if len(failed) == 0 {
+		fmt.Printf("\033[32m✅ Sent %d messages\033[0m\n", len(sent))
+	} else {
+		successCount := len(sent) - len(failed)
+		if successCount < 0 {
+			successCount = 0
+		}
+		fmt.Printf("\033[31m❌ Sent %d, failed %d\033[0m\n", successCount, len(failed))
+		for _, f := range failed {
+			fmt.Printf("  - %s\n", f)
+		}
+	}
+}
+
 func sendMail(cfg *Config, recipients []string, subject, html string) ([]PostmarkBatchResult, error) {
-	fmt.Printf("Sending batch [%d recipients]...", len(recipients))
+	/* Start a tiny spinner while the HTTP call runs.
+	 * Uses \r to update the same line. Stops as soon as the network call returns.
+	 */
+
+	stop := make(chan struct{})
+	done := make(chan struct{})
+	go func() {
+		frames := []rune{'|', '/', '-', '\\'}
+		i := 0
+		for {
+			select {
+			case <-stop:
+				close(done)
+				return
+			default:
+				fmt.Printf("\rSending batch [%d recipients]... %c", len(recipients), frames[i%len(frames)])
+				i++
+				time.Sleep(120 * time.Millisecond)
+			}
+		}
+	}()
+
+	/*
+	 * Prepare and make the network call
+	 */
 
 	from := cfg.Postmark.SenderEmail
 	if cfg.Postmark.SenderName != "" {
@@ -400,13 +447,21 @@ func sendMail(cfg *Config, recipients []string, subject, html string) ([]Postmar
 
 	req, err := http.NewRequest(http.MethodPost, "https://api.postmarkapp.com/email/batchWithTemplates", bytes.NewReader(reqBody))
 	if err != nil {
+		// stop spinner before returning
+		close(stop)
+		<-done
+		fmt.Printf("\r")
 		return nil, err
 	}
+
 	req.Header.Set("Accept", "application/json")
 	req.Header.Set("Content-Type", "application/json")
 	req.Header.Set("X-Postmark-Server-Token", cfg.Postmark.ServerToken)
 	res, err := postmarkClient.Do(req)
 	if err != nil {
+		close(stop)
+		<-done
+		fmt.Printf("\r\033[31m❌ Sending batch [%d recipients]... error: %v\033[0m\n", len(recipients), err)
 		return nil, err
 	}
 
@@ -414,17 +469,30 @@ func sendMail(cfg *Config, recipients []string, subject, html string) ([]Postmar
 	resBody, err := io.ReadAll(res.Body)
 	res.Body.Close()
 	if err != nil {
+		close(stop)
+		<-done
+		fmt.Printf("\r")
 		return nil, err
 	}
+
 	if res.StatusCode != 200 {
+		close(stop)
+		<-done
+		fmt.Printf("\r\033[31m❌ Bad response from postmark: %d\033[0m\n", res.StatusCode)
 		return nil, fmt.Errorf("Bad response from postmark: %d", res.StatusCode)
 	}
+
 	err = json.Unmarshal(resBody, &results)
 	if err != nil {
-		fmt.Printf("Batch sent successfully, but failed to parse response from postmark.\n")
+		close(stop)
+		<-done
+		fmt.Printf("\r\033[33m⚠️  Batch sent but failed to parse Postmark response\033[0m\n")
 		return nil, nil
 	}
-	fmt.Printf("Done.\n")
+
+	close(stop)
+	<-done
+	fmt.Printf("\r\033[32m✅ Emailed batch of %d recipients\033[0m\n", len(recipients))
 	return results, nil
 }