Create new thread when product is available again (#28)

Instead of spamming a twitter thread with generic replies confusing the
community because the original message was posted long time ago, the bot now
creates a new thread with all product information and an incrementing counter
for uniqueness.

notifier_twitter.go

@@ -23,6 +23,7 @@ type Tweet struct {
 	TweetID     int64   `gorm:"not null;unique"`
 	Hash        string  `gorm:"unique"`
 	LastTweetID int64   `gorm:"index"`
+	Counter     int64   `gorm:"not null;default:1"`
 	ProductURL  string  `gorm:"index"`
 	Product     Product `gorm:"not null;references:URL"`
 }
@@ -143,7 +144,7 @@ func (c *TwitterNotifier) buildHashtags(productName string) string {
 func (c *TwitterNotifier) NotifyWhenAvailable(shopName string, productName string, productPrice float64, productCurrency string, productURL string) error {
 	// format message
 	hashtags := c.buildHashtags(productName)
-	message := formatAvailableTweet(shopName, productName, productPrice, productCurrency, productURL, hashtags)
+	message := formatAvailableTweet(shopName, productName, productPrice, productCurrency, productURL, hashtags, 0)
 
 	// compute message checksum to avoid duplicates
 	var tweet Tweet
@@ -164,7 +165,7 @@ func (c *TwitterNotifier) NotifyWhenAvailable(shopName string, productName strin
 		log.Infof("tweet %d sent for product '%s'", tweetID, productURL)
 
 		// save thread to database
-		tweet = Tweet{TweetID: tweetID, ProductURL: productURL, Hash: hash}
+		tweet = Tweet{TweetID: tweetID, ProductURL: productURL, Hash: hash, Counter: 1}
 		trx = c.db.Create(&tweet)
 		if trx.Error != nil {
 			return fmt.Errorf("could not save tweet %d to database for product '%s': %s", tweet.TweetID, productURL, trx.Error)
@@ -173,48 +174,49 @@ func (c *TwitterNotifier) NotifyWhenAvailable(shopName string, productName strin
 
 	} else {
 
-		if !c.enableReplies {
+		// tweet already has been sent in the past
-			log.Debugf("twitter replies are disabled, skipping available notification for product '%s'", productURL)
+		// creating new thread with a counter
-			return nil
+		tweet.Counter++
-		}
+		message = formatAvailableTweet(shopName, productName, productPrice, productCurrency, productURL, hashtags, tweet.Counter)
-
+		tweetID, err := c.createTweet(message)
-		// select tweet to reply
-		lastTweetID := CoalesceInt64(tweet.LastTweetID, tweet.TweetID)
-		if lastTweetID == 0 {
-			return fmt.Errorf("could not find original tweet ID to create reply for product '%s'", productURL)
-		}
-
-		// tweet already has been sent in the past and replies are enabled
-		// continuing thread
-		tweetID, err := c.replyToTweet(lastTweetID, "Good news, it's available again!")
 		if err != nil {
-			return fmt.Errorf("could not reply to tweet %d for product '%s': %s", lastTweetID, productURL, err)
+			return fmt.Errorf("could not create new twitter thread for product '%s': %s", productURL, err)
 		}
-		log.Infof("reply to tweet %d sent with id %d for product '%s'", lastTweetID, tweetID, productURL)
+		log.Infof("tweet %d sent for product '%s'", tweetID, productURL)
 
 		// save thread to database
 		tweet.LastTweetID = tweetID
 		if trx = c.db.Save(&tweet); trx.Error != nil {
 			return fmt.Errorf("could not save tweet %d to database for product '%s': %s", tweet.TweetID, productURL, trx.Error)
 		}
-		log.Debugf("tweet %d saved in database", tweet.TweetID)
+		log.Debugf("tweet %d saved to database", tweet.TweetID)
 	}
 
 	return nil
 }
 
 // formatAvailableTweet creates a message based on product characteristics
-func formatAvailableTweet(shopName string, productName string, productPrice float64, productCurrency string, productURL string, hashtags string) string {
+func formatAvailableTweet(shopName string, productName string, productPrice float64, productCurrency string, productURL string, hashtags string, counter int64) string {
 	// format message
 	formattedPrice := formatPrice(productPrice, productCurrency)
 	message := fmt.Sprintf("%s: %s for %s is available at %s %s", shopName, productName, formattedPrice, productURL, hashtags)
+	if counter > 1 {
+		message = fmt.Sprintf("%s (%d)", message, counter)
+	}
 
 	// truncate tweet if too big
 	if utf8.RuneCountInString(message) > tweetMaxSize {
+		messageWithoutProduct := fmt.Sprintf("%s:  for %s is available at %s %s", shopName, formattedPrice, productURL, hashtags)
+		if counter > 1 {
+			messageWithoutProduct = fmt.Sprintf("%s (%d)", messageWithoutProduct, counter)
+		}
 		// maximum tweet size - other characters - additional "…" to say product name has been truncated
-		productNameSize := tweetMaxSize - utf8.RuneCountInString(fmt.Sprintf("%s:  for %s is available at %s %s", shopName, formattedPrice, productURL, hashtags)) - 1
+		productNameSize := tweetMaxSize - utf8.RuneCountInString(messageWithoutProduct) - 1
 		format := fmt.Sprintf("%%s: %%.%ds… for %%s is available at %%s %%s", productNameSize)
 		message = fmt.Sprintf(format, shopName, productName, formattedPrice, productURL, hashtags)
+		if counter > 1 {
+			message = fmt.Sprintf("%s (%d)", message, counter)
+		}
 	}
 
 	return message

notifier_twitter_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"testing"
+	"unicode/utf8"
 )
 
 func TestBuildHashtags(t *testing.T) {
@@ -64,19 +65,68 @@ func TestFormatAvailableTweet(t *testing.T) {
 		productCurrency string
 		productURL      string
 		hashtags        string
+		counter         int64
 		expected        string
 	}{
-		{"shop.com", "my awesome product", 999.99, "USD", "https://shop.com/awesome", "#awesome #product", "shop.com: my awesome product for $999.99 is available at https://shop.com/awesome #awesome #product"},
+		{
-		{"shop.com", "my awesome product with very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very long name", 999.99, "USD", "https://shop.com/awesome", "#awesome #product", "shop.com: my awesome product with very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very… for $999.99 is available at https://shop.com/awesome #awesome #product"},
+			// short product name
+			"shop.com",
+			"my awesome product",
+			999.99,
+			"USD",
+			"https://shop.com/awesome",
+			"#awesome #product",
+			0,
+			"shop.com: my awesome product for $999.99 is available at https://shop.com/awesome #awesome #product",
+		},
+		{
+			// long product name
+			"shop.com",
+			"my awesome product with very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very long name",
+			999.99,
+			"USD",
+			"https://shop.com/awesome",
+			"#awesome #product",
+			0,
+			"shop.com: my awesome product with very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very… for $999.99 is available at https://shop.com/awesome #awesome #product",
+		},
+		{
+			// short product name with a counter
+			"shop.com",
+			"my awesome product",
+			999.99,
+			"USD",
+			"https://shop.com/awesome",
+			"#awesome #product",
+			2,
+			"shop.com: my awesome product for $999.99 is available at https://shop.com/awesome #awesome #product (2)",
+		},
+		{
+			// long product name with a counter
+			"shop.com",
+			"my awesome product with very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very long name",
+			999.99,
+			"USD",
+			"https://shop.com/awesome",
+			"#awesome #product",
+			2,
+			"shop.com: my awesome product with very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very … for $999.99 is available at https://shop.com/awesome #awesome #product (2)",
+		},
 	}
 	for i, tc := range tests {
 		t.Run(fmt.Sprintf("TestFormatAvailableTweet#%d", i), func(t *testing.T) {
-			got := formatAvailableTweet(tc.shopName, tc.productName, tc.productPrice, tc.productCurrency, tc.productURL, tc.hashtags)
+			got := formatAvailableTweet(tc.shopName, tc.productName, tc.productPrice, tc.productCurrency, tc.productURL, tc.hashtags, tc.counter)
 			if got != tc.expected {
 				t.Errorf("for %s, got '%s', want '%s'", tc.productName, got, tc.expected)
 			} else {
 				t.Logf("for %s, got '%s', want '%s'", tc.productName, got, tc.expected)
 			}
+
+			// ensure generated tweet doesn't exceed maximum length
+			if utf8.RuneCountInString(got) > tweetMaxSize {
+				t.Errorf("for %s, got '%s' which exceeed tweet maximum lenght of %d chars", tc.productName, got, tweetMaxSize)
+			}
+
 		})
 	}
 }