I need a small, reusable engine that turns each of my retail clients’ Google Sheets stock list into a WhatsApp Business bot. How it should work • Google Sheets is the single source of truth. A Zap (or webhook) watches the “Quantity” column. • When any SKU falls below five units, the bot immediately sends a plain-text WhatsApp message to the shop’s customer list: “Out of <product> – back soon!”. • When the quantity rises from 0-4 to 5+, a second WhatsApp message goes out: “New <product> just arrived!”. • Product photos live in Google Drive; the bot pulls the matching image via SKU link and posts it to the shop’s Status once per restock. • All messaging runs through each client’s own Twilio WhatsApp Business account—no shared numbers. I’ll drop their SID, auth token and phone number into an .env (or Zapier connection) and it must work without code edits. Essential deliverables 1. Clean, well-commented code or low-code Zapier template that: – Authenticates with Twilio through environment variables. – Reads Google Sheets rows and stores last-sent state (DB, hidden sheet or Zapier storage). – Sends text-only low-stock and restock WhatsApp messages. – Uploads the matching Drive image to Status on restock. 2. A step-by-step setup guide so I can spin up a new shop in under 15 minutes: connect sheet, paste Twilio keys, map Drive folder, done. 3. Brief testing instructions I can follow to prove messages fire at the correct thresholds. Acceptance criteria • No hard-coded credentials, sheet IDs or phone numbers. • Latency from stock change to WhatsApp alert under 2 minutes. • Module passes a live test on one demo sheet and one real client sheet. Preferred stack is Node.js or Python, but I’m open to your Zapier-centric approach if it meets every requirement above and keeps future maintenance minimal.