From 0ea94aefd110db1a64741b53256b515b3c6904ca Mon Sep 17 00:00:00 2001
From: Christian Vidal Wolf <christianvidalwolf@gmail.com>
Date: Wed, 28 Jan 2026 15:17:58 +0100
Subject: [PATCH] Implement Smart Seasonality blending for products with sparse
 history (fixes 0-forecast issue)

---
 services/dataProcessor.ts | 45 ++++++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/services/dataProcessor.ts b/services/dataProcessor.ts
index 34e49bb..42d5b43 100644
--- a/services/dataProcessor.ts
+++ b/services/dataProcessor.ts
@@ -1625,16 +1625,18 @@ export const calculateForecastViewData = (
     const data2026 = rawData.filter(r => r.year === 2026);
 
     // Calculate Seasonality weights for 2025
-    const getWeights = (records: SalesRecord[]): number[] | null => {
+    const getWeightsInfo = (records: SalesRecord[]): { weights: number[]; monthsCount: number } | null => {
         const weights = new Array(12).fill(0);
         let total = 0;
+        const seenMonths = new Set<string>();
 
         records.forEach(r => {
             const m = r.month.split('-')[0];
             const idx = MONTH_ORDER.indexOf(m);
-            if (idx !== -1) {
+            if (idx !== -1 && r.units > 0) {
                 weights[idx] += r.units;
                 total += r.units;
+                seenMonths.add(m);
             }
         });
 
@@ -1642,7 +1644,10 @@ export const calculateForecastViewData = (
         // Return null ONLY if there's no data at all for this ASIN in 2025.
         if (total === 0) return null;
 
-        return weights.map(w => w / total);
+        return {
+            weights: weights.map(w => w / total),
+            monthsCount: seenMonths.size
+        };
     };
 
     // 1. Determine Global/Default Weights
@@ -1734,25 +1739,27 @@ export const calculateForecastViewData = (
 
         if (productRecords2025.length > 0) {
             if (isUkOnly) {
-                // For UK Only, we try to be strict, but fallback to global UK weights if needed
                 const ukProd = productRecords2025.filter(r => r.customer === 'Amazon UK');
-                // We use hybrid approach only if we have PanEU data for this product too
-                const peProd = productRecords2025.filter(r => PAN_EU_COUNTRIES.includes(r.customer));
-
-                // If we have solid data for this product, use Hybrid or UK weights
-                const specificWeights = getHybridWeights(peProd, ukProd);
-                // Wait, getHybridWeights calls getGlobalWeightsInner which never returns null.
-                // We need to check if specific product data is sparse.
-
-                // Let's simplify: Check if we have enough UK history
-                const ukWeights = getWeights(ukProd);
-                if (ukWeights) {
-                    productWeights = ukWeights;
+                const info = getWeightsInfo(ukProd);
+                if (info) {
+                    if (info.monthsCount < 6) {
+                        // Smart Blending: 50% specific, 50% global
+                        productWeights = info.weights.map((w, i) => (w * 0.5) + (globalWeights[i] * 0.5));
+                    } else {
+                        productWeights = info.weights;
+                    }
                 }
             } else {
-                const w = getWeights(productRecords2025);
-                if (w) productWeights = w;
-                // If w is null (sparse data), productWeights remains globalWeights (Default)
+                const info = getWeightsInfo(productRecords2025);
+                if (info) {
+                    if (info.monthsCount < 6) {
+                        // Smart Blending: 50% specific, 50% global
+                        productWeights = info.weights.map((w, i) => (w * 0.5) + (globalWeights[i] * 0.5));
+                    } else {
+                        productWeights = info.weights;
+                    }
+                }
+                // If info is null (sparse data), productWeights remains globalWeights (Default)
             }
         }