feat: Some rudimentary nsfw and hashtag spam filtering

A very nsfw post (not tagged as such) popped into my Norwegian feed. No
good! Added some hashtag and nsfw filtering based around common phrases
to hopefully weed out new occurrences.

firehose/firehose.go

@@ -86,6 +86,87 @@ func HasEnoughNorwegianLetters(text string) bool {
 	return ratio > 0.30
 }
 
+// Rename and update the function to handle both NSFW and spam detection
+func containsSpamContent(text string) bool {
+	// Convert to lowercase for case-insensitive matching
+	lowerText := strings.ToLower(text)
+
+	// Common spam patterns
+	spamPatterns := []string{
+		"onlyfans.com",
+		"join my vip",
+		"subscribe to my",
+		"check my profile",
+		"check my bio",
+		"link in bio",
+		"link in profile",
+		"follow me",
+		"follow back",
+		"follow for follow",
+		"f4f",
+	}
+
+	// NSFW terms - keep this minimal to avoid false positives
+	nsfwTerms := []string{
+		"porn",
+		"xxx",
+		"nsfw",
+		"18+",
+	}
+
+	// Check for spam patterns
+	for _, pattern := range spamPatterns {
+		if strings.Contains(lowerText, pattern) {
+			return true
+		}
+	}
+
+	// Check for NSFW terms
+	for _, term := range nsfwTerms {
+		if strings.Contains(lowerText, term) {
+			return true
+		}
+	}
+
+	// Check for excessive emoji spam (common in NSFW spam)
+	emojiCount := 0
+	for _, r := range text {
+		if r >= 0x1F300 { // Start of emoji range
+			emojiCount++
+			if emojiCount > 8 { // Threshold for spam
+				return true
+			}
+		}
+	}
+
+	// Count hashtags
+	hashtagCount := strings.Count(text, "#")
+	// If more than 5 hashtags, consider it spam
+	if hashtagCount > 5 {
+		log.Infof("Skipping spam post with many hashtags: %s", text)
+		return true
+	}
+
+	// Check for repeated hashtags (common spam pattern)
+	if strings.Count(text, "##") > 0 {
+		log.Infof("Skipping spam post with repeated hashtags: %s", text)
+		return true
+	}
+
+	// Check for hashtag ratio
+	words := strings.Fields(text)
+	if len(words) > 0 {
+		hashtagRatio := float64(hashtagCount) / float64(len(words))
+		// If more than 40% of words are hashtags, consider it spam
+		if hashtagRatio > 0.4 {
+			log.Infof("Skipping spam post with high hashtag ratio: %s", text)
+			return true
+		}
+	}
+
+	return false
+}
+
 // Subscribe to the firehose using the Firehose struct as a receiver
 func Subscribe(ctx context.Context, postChan chan interface{}, ticker *time.Ticker, seq int64, detectFalseNegatives bool) {
 
@@ -276,12 +357,16 @@ func (p *PostProcessor) processPost(evt *atproto.SyncSubscribeRepos_Commit, op *
 		shouldProcess, langs = p.DetectNorwegianLanguage(record.Text, record.Langs)
 	}
 
-	log.Infof("Should process: %t, langs: %v", shouldProcess, langs)
-
 	if !shouldProcess {
 		return nil
 	}
 
+	// Check for spam content after confirming it's Norwegian
+	if containsSpamContent(record.Text) {
+		log.Debugf("Skipping spam post: %s", uri)
+		return nil
+	}
+
 	// Process the post
 	p.ticker.Reset(5 * time.Minute)