feat: add extraction monitoring and metrics logging

src/facebook.ts

@@ -554,6 +554,41 @@ function extractFacebookMarketplaceData(
 	return marketplaceData.feed_units.edges.map((edge) => ({ node: edge.node }));
 }
 
+/**
+ * Monitor API extraction success/failure for detecting changes
+ */
+let extractionStats = {
+	totalExtractions: 0,
+	successfulExtractions: 0,
+	failedExtractions: 0,
+	lastApiChangeDetected: null as Date | null,
+};
+
+/**
+ * Log extraction metrics for monitoring API stability
+ */
+function logExtractionMetrics(success: boolean, itemId?: string) {
+	extractionStats.totalExtractions++;
+	if (success) {
+		extractionStats.successfulExtractions++;
+	} else {
+		extractionStats.failedExtractions++;
+	}
+
+	// Log warning if extraction success rate drops below 80%
+	const successRate = extractionStats.successfulExtractions / extractionStats.totalExtractions;
+	if (extractionStats.totalExtractions > 10 && successRate < 0.8 && !extractionStats.lastApiChangeDetected) {
+		console.warn("⚠️  Facebook Marketplace API extraction success rate dropped below 80%. This may indicate API changes.");
+		extractionStats.lastApiChangeDetected = new Date();
+	}
+
+	if (success) {
+		console.log(`📊 Facebook API extraction stats: ${extractionStats.successfulExtractions}/${extractionStats.totalExtractions} successful`);
+	} else {
+		console.warn(`❌ Facebook API extraction failed for item ${itemId || 'unknown'}`);
+	}
+}
+
 /**
  * Turns cents to localized currency string.
  */