Reply to WhatsApp customers by replying to an email

import re, base64
from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build
from clickruntime import on_trigger, credentials, http, notify, report_fetched

WA = "https://graph.facebook.com/v20.0/your-phone-number-id/messages"
gmail = lambda: build("gmail", "v1", credentials=Credentials(credentials.connection("google", "work")), cache_discovery=False).users()
LABEL = "Label_sent_to_whatsapp"  # Gmail label ID for "Sent to WhatsApp"
QUERY = 'in:sent subject:"WhatsApp from" -label:sent-to-whatsapp newer_than:2d'

def plain_body(payload):
    parts = payload.get("parts") or [payload]
    for p in parts:
        if p.get("mimeType") == "text/plain" and p["body"].get("data"):
            return base64.urlsafe_b64decode(p["body"]["data"]).decode(errors="ignore")
        if p.get("parts"):
            found = plain_body(p)
            if found:
                return found
    return ""

def strip_quote(text):
    lines = []
    for line in text.splitlines():
        if line.startswith(">") or re.match(r"^On .+wrote:$", line.strip()):
            break
        lines.append(line)
    return "\n".join(lines).strip()

@on_trigger
def run(event):
    ids = [m["id"] for m in gmail().messages().list(userId="me", q=QUERY, maxResults=20).execute().get("messages", [])]
    report_fetched(len(ids))
    sent = 0
    for i in ids:
        m = gmail().messages().get(userId="me", id=i, format="full").execute()
        subject = next(h["value"] for h in m["payload"]["headers"] if h["name"] == "Subject")
        number = re.search(r"\(\+(\d{7,15})\)", subject)
        text = strip_quote(plain_body(m["payload"]))
        if number and text:
            r = http.post(WA, headers={"Authorization": f"Bearer {credentials.secret('WHATSAPP_TOKEN')}"},
                          json={"messaging_product": "whatsapp", "to": number.group(1), "type": "text", "text": {"body": text[:4000]}})
            if r.status_code >= 400:
                notify.email_me(f"WhatsApp reply not sent to +{number.group(1)}",
                                f"WhatsApp said: {r.json().get('error', {}).get('message')}\n\nYour reply:\n{text}")
            else:
                sent += 1
        gmail().messages().modify(userId="me", id=i, body={"addLabelIds": [LABEL]}).execute()
    return {"sent": sent}