WhatsApp Cloud API Integration

// server.js - Node.js 18+ (npm install express). Run: AVOX_API_KEY=... node server.js
import express from "express";
import { randomUUID, timingSafeEqual } from "node:crypto";

const app = express();

// Avox client: one Idempotency-Key per message, retries only what's safe to retry.
const RETRY_SAME_KEY = new Set(["rate_limited", "idempotency_in_progress", "internal_error", "network_error"]);
const RETRY_NEW_KEY = new Set(["meta_rate_limited"]);
const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
const backoffMs = (attempt) => Math.min(30_000, 1_000 * 2 ** (attempt - 1)) * (0.5 + Math.random() / 2);

async function sendWhatsApp(message, idempotencyKey = randomUUID(), maxAttempts = 5) {
  let key = idempotencyKey;
  for (let attempt = 1; ; attempt++) {
    const res = await fetch("https://api.avox.com/api/messages/send", {
      method: "POST",
      headers: {
        Authorization: `Bearer ${process.env.AVOX_API_KEY}`,
        "Content-Type": "application/json",
        "Idempotency-Key": key,
      },
      body: JSON.stringify(message),
      signal: AbortSignal.timeout(30_000),
    }).catch(() => null);

    const data = res ? await res.json().catch(() => null) : null;
    const requestId = res?.headers.get("X-Request-Id") ?? null;
    if (data?.ok) {
      console.info(`[avox] sent message_id=${data.message_id} request_id=${requestId}`);
      return data;
    }

    const code = data?.error?.code ?? (res ? `http_${res.status}` : "network_error");
    console.warn(`[avox] ${code} request_id=${requestId} attempt=${attempt}`);
    const retryable = RETRY_SAME_KEY.has(code) || RETRY_NEW_KEY.has(code);
    if (!retryable || attempt >= maxAttempts) {
      throw Object.assign(new Error(`Avox send failed: ${code}`), {
        code,
        status: res?.status ?? 502,
        requestId: data?.error?.request_id ?? requestId,
        details: data?.error?.details,
      });
    }
    if (RETRY_NEW_KEY.has(code)) key = randomUUID(); // WhatsApp's refusal is stored against the old key
    const retryAfter = Number(res?.headers.get("Retry-After"));
    await sleep(retryAfter > 0 ? retryAfter * 1000 : backoffMs(attempt));
  }
}

function safeEqual(a, b) {
  const x = Buffer.from(a ?? "");
  const y = Buffer.from(b ?? "");
  return x.length > 0 && x.length === y.length && timingSafeEqual(x, y);
}

// POST /notify  { "to": "15551234567", "template": "order_shipped", "params": ["A-1042"], "reference": "order-A-1042-shipped" }
// Your own apps call this with the x-internal-token header; the key never leaves this server.
app.post("/notify", express.json({ limit: "100kb" }), async (req, res) => {
  if (!safeEqual(req.get("x-internal-token"), process.env.INTERNAL_TOKEN)) return res.sendStatus(401);
  const { to, template, params = [], language = "en_US", reference } = req.body ?? {};
  if (!to || !template || !reference) return res.status(400).json({ error: "to, template and reference are required" });

  try {
    const result = await sendWhatsApp(
      {
        to,
        type: "template",
        template: {
          name: template,
          language: { code: language },
          ...(params.length ? { components: [{ type: "body", parameters: params.map((t) => ({ type: "text", text: String(t) })) }] } : {}),
        },
        biz_opaque_callback_data: reference,
      },
      reference // the same reference always means the same message: retries never send twice
    );
    res.json({ ok: true, message_id: result.message_id });
  } catch (err) {
    res.status(err.status >= 500 ? 502 : 422).json({ ok: false, code: err.code, request_id: err.requestId, details: err.details });
  }
});

app.listen(process.env.PORT ?? 3000, () => console.log("Listening"));

// app/api/notify/route.ts - Next.js (App Router)
import { randomUUID, timingSafeEqual } from "node:crypto";
import { NextResponse, type NextRequest } from "next/server";

export const runtime = "nodejs";

// Avox client: one Idempotency-Key per message, retries only what's safe to retry.
const RETRY_SAME_KEY = new Set(["rate_limited", "idempotency_in_progress", "internal_error", "network_error"]);
const RETRY_NEW_KEY = new Set(["meta_rate_limited"]);
const sleep = (ms: number) => new Promise((resolve) => setTimeout(resolve, ms));
const backoffMs = (attempt: number) => Math.min(30_000, 1_000 * 2 ** (attempt - 1)) * (0.5 + Math.random() / 2);

type AvoxFailure = Error & { code: string; status: number; requestId: string | null; details?: unknown };

async function sendWhatsApp(message: Record<string, unknown>, idempotencyKey: string = randomUUID(), maxAttempts = 5) {
  let key = idempotencyKey;
  for (let attempt = 1; ; attempt++) {
    const res = await fetch("https://api.avox.com/api/messages/send", {
      method: "POST",
      headers: {
        Authorization: `Bearer ${process.env.AVOX_API_KEY}`,
        "Content-Type": "application/json",
        "Idempotency-Key": key,
      },
      body: JSON.stringify(message),
      cache: "no-store",
      signal: AbortSignal.timeout(30_000),
    }).catch(() => null);

    const data = res ? await res.json().catch(() => null) : null;
    const requestId = res?.headers.get("X-Request-Id") ?? null;
    if (data?.ok) {
      console.info(`[avox] sent message_id=${data.message_id} request_id=${requestId}`);
      return data as { ok: true; request_id: string; message_id: string | null; result: unknown };
    }

    const code: string = data?.error?.code ?? (res ? `http_${res.status}` : "network_error");
    console.warn(`[avox] ${code} request_id=${requestId} attempt=${attempt}`);
    const retryable = RETRY_SAME_KEY.has(code) || RETRY_NEW_KEY.has(code);
    if (!retryable || attempt >= maxAttempts) {
      throw Object.assign(new Error(`Avox send failed: ${code}`), {
        code,
        status: res?.status ?? 502,
        requestId: data?.error?.request_id ?? requestId,
        details: data?.error?.details,
      }) as AvoxFailure;
    }
    if (RETRY_NEW_KEY.has(code)) key = randomUUID(); // WhatsApp's refusal is stored against the old key
    const retryAfter = Number(res?.headers.get("Retry-After"));
    await sleep(retryAfter > 0 ? retryAfter * 1000 : backoffMs(attempt));
  }
}

function safeEqual(a: string | null, b: string | undefined) {
  const x = Buffer.from(a ?? "");
  const y = Buffer.from(b ?? "");
  return x.length > 0 && x.length === y.length && timingSafeEqual(x, y);
}

// POST /api/notify  { "to": "15551234567", "template": "order_shipped", "params": ["A-1042"], "reference": "order-A-1042-shipped" }
// Your own apps call this with the x-internal-token header; the key never leaves the server.
export async function POST(request: NextRequest) {
  if (!safeEqual(request.headers.get("x-internal-token"), process.env.INTERNAL_TOKEN)) {
    return NextResponse.json({ error: "unauthorized" }, { status: 401 });
  }
  const body = await request.json().catch(() => null);
  const { to, template, params = [], language = "en_US", reference } = body ?? {};
  if (!to || !template || !reference) {
    return NextResponse.json({ error: "to, template and reference are required" }, { status: 400 });
  }

  try {
    const result = await sendWhatsApp(
      {
        to,
        type: "template",
        template: {
          name: template,
          language: { code: language },
          ...(params.length ? { components: [{ type: "body", parameters: params.map((t: unknown) => ({ type: "text", text: String(t) })) }] } : {}),
        },
        biz_opaque_callback_data: reference,
      },
      reference // the same reference always means the same message: retries never send twice
    );
    return NextResponse.json({ ok: true, message_id: result.message_id });
  } catch (err) {
    const e = err as AvoxFailure;
    return NextResponse.json({ ok: false, code: e.code, request_id: e.requestId, details: e.details }, { status: e.status >= 500 ? 502 : 422 });
  }
}

# main.py - pip install fastapi uvicorn httpx ; run: uvicorn main:app --port 3000
import asyncio
import hmac
import logging
import os
import random
import uuid

import httpx
from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse, Response

log = logging.getLogger("avox")
app = FastAPI()
http = httpx.AsyncClient(timeout=30)

# Avox client: one Idempotency-Key per message, retries only what's safe to retry.
RETRY_SAME_KEY = {"rate_limited", "idempotency_in_progress", "internal_error", "network_error"}
RETRY_NEW_KEY = {"meta_rate_limited"}


class AvoxError(Exception):
    def __init__(self, code, status, request_id, details=None):
        super().__init__(f"Avox send failed: {code}")
        self.code, self.status, self.request_id, self.details = code, status, request_id, details


def backoff(attempt):
    return min(30.0, 2 ** (attempt - 1)) * (0.5 + random.random() / 2)


async def send_whatsapp(message: dict, idempotency_key: str | None = None, max_attempts: int = 5) -> dict:
    key = idempotency_key or str(uuid.uuid4())
    attempt = 0
    while True:
        attempt += 1
        res, data = None, None
        try:
            res = await http.post(
                "https://api.avox.com/api/messages/send",
                headers={"Authorization": f"Bearer {os.environ['AVOX_API_KEY']}", "Idempotency-Key": key},
                json=message,
            )
            data = res.json()
        except (httpx.TransportError, ValueError):
            pass

        request_id = res.headers.get("X-Request-Id") if res is not None else None
        if data and data.get("ok"):
            log.info("sent message_id=%s request_id=%s", data.get("message_id"), request_id)
            return data

        error = (data or {}).get("error") or {}
        code = error.get("code") or (f"http_{res.status_code}" if res is not None else "network_error")
        log.warning("%s request_id=%s attempt=%s", code, request_id, attempt)
        if code not in RETRY_SAME_KEY | RETRY_NEW_KEY or attempt >= max_attempts:
            raise AvoxError(code, res.status_code if res is not None else 502,
                            error.get("request_id", request_id), error.get("details"))
        if code in RETRY_NEW_KEY:
            key = str(uuid.uuid4())  # WhatsApp's refusal is stored against the old key
        retry_after = int(res.headers.get("Retry-After") or 0) if res is not None else 0
        await asyncio.sleep(retry_after if retry_after > 0 else backoff(attempt))


def avox_error_response(err: AvoxError):
    status = 502 if err.status >= 500 else 422
    return JSONResponse({"ok": False, "code": err.code, "request_id": err.request_id, "details": err.details},
                        status_code=status)


# POST /notify  {"to": "15551234567", "template": "order_shipped", "params": ["A-1042"], "reference": "order-A-1042-shipped"}
# Your own apps call this with the x-internal-token header; the key never leaves this server.
@app.post("/notify")
async def notify(request: Request):
    token = request.headers.get("x-internal-token", "")
    if not token or not hmac.compare_digest(token, os.environ.get("INTERNAL_TOKEN", "")):
        return Response(status_code=401)
    body = await request.json()
    to, name, reference = body.get("to"), body.get("template"), body.get("reference")
    if not (to and name and reference):
        return JSONResponse({"error": "to, template and reference are required"}, status_code=400)

    template = {"name": name, "language": {"code": body.get("language", "en_US")}}
    params = body.get("params") or []
    if params:
        template["components"] = [{"type": "body", "parameters": [{"type": "text", "text": str(p)} for p in params]}]

    try:
        # The same reference always means the same message: retries never send twice.
        result = await send_whatsapp(
            {"to": to, "type": "template", "template": template, "biz_opaque_callback_data": reference},
            idempotency_key=reference,
        )
        return {"ok": True, "message_id": result.get("message_id")}
    except AvoxError as err:
        return avox_error_response(err)