Twilio (SMS)

Send SMS messages via Twilio's Programmable Messaging API. You can use the official SDK or hit the REST endpoint directly with fetch.

Account setup

From the Twilio Console grab:

• TWILIO_ACCOUNT_SID
• TWILIO_AUTH_TOKEN
• TWILIO_FROM_NUMBER (in E.164 format, e.g. +15551234567)

Installation (SDK)

pnpm add twilio

Configure the client

src/clients/twilio.ts

import twilio from "twilio";

export const twilioClient = twilio(
  process.env.TWILIO_ACCOUNT_SID!,
  process.env.TWILIO_AUTH_TOKEN!
);

Define the effect

From/to numbers are baked in. The handler hands the effect raw values; the SMS body is built inside.

src/effects/twilio.ts

import { createEffect, S } from "envio";
import { twilioClient } from "../clients/twilio";

const FROM = process.env.TWILIO_FROM_NUMBER!;
const TO = process.env.TWILIO_TO_NUMBER!;

const formatUnits = (value: bigint, decimals = 18) => {
  const base = 10n ** BigInt(decimals);
  const whole = value / base;
  const frac = value % base;
  if (frac === 0n) return whole.toString();
  return `${whole}.${frac.toString().padStart(decimals, "0").replace(/0+$/, "")}`;
};

export const notifyTransfer = createEffect(
  {
    name: "notifyTransfer",
    input: { value: S.bigint },
    rateLimit: { calls: 1, per: "second" }, // Twilio default trial = 1 msg/sec
    mode: "orderedAfterCommit",
  },
  async ({ input }) => {
    await twilioClient.messages.create({
      from: FROM,
      to: TO,
      body: `Transfer detected: ${formatUnits(input.value)} RETH`,
    });
  }
);

Raw fetch alternative

If you'd rather skip the SDK:

const auth = Buffer.from(
  `${process.env.TWILIO_ACCOUNT_SID}:${process.env.TWILIO_AUTH_TOKEN}`
).toString("base64");

await fetch(
  `https://api.twilio.com/2010-04-01/Accounts/${process.env.TWILIO_ACCOUNT_SID}/Messages.json`,
  {
    method: "POST",
    headers: {
      Authorization: `Basic ${auth}`,
      "Content-Type": "application/x-www-form-urlencoded",
    },
    body: new URLSearchParams({
      From: process.env.TWILIO_FROM_NUMBER!,
      To: input.to,
      Body: input.body,
    }),
  }
);

Call it from a handler

The rindexer config…

chat:
  twilio:
    - account_sid: ${TWILIO_ACCOUNT_SID}
      auth_token: ${TWILIO_AUTH_TOKEN}
      from_number: ${TWILIO_FROM_NUMBER}
      to_number: ${TWILIO_TO_NUMBER}
      messages:
        - event_name: Transfer
          filter_expression: "value >= 10"
          template_inline: "Transfer detected: {{value}} tokens"

…becomes:

src/handlers/RocketPoolETH.ts

import { indexer } from "envio";
import { notifyTransfer } from "../effects/twilio";

indexer.onEvent(
  { contract: "RocketPoolETH", event: "Transfer" },
  async ({ event, context }) => {
    const { value } = event.params;
    if (value < 10n) return;

    context.effect(notifyTransfer, { value });
  },
);

SMS is rate-limited and expensive — keep your conditions strict. For time-sensitive alerts, switch the effect to mode: "ordered" so the SMS is dispatched inline rather than after the DB commit.