import crypto from "node:crypto";

const API = process.env.MPESA_ENV === "prod"
  ? "https://api.safaricom.co.ke"
  : "https://sandbox.safaricom.co.ke";
const AUTH_PATH = "/oauth/v1/generate";
const STK_PATH = "/mpesa/stkpush/v1/processrequest";
const AUTH_QS = "grant_type=client_credentials";

const KEY = process.env.MPESA_KEY ?? "";
const SECRET = process.env.MPESA_SECRET ?? "";
const SHORTCODE = process.env.MPESA_SHORTCODE ?? "";
const PASSKEY = process.env.MPESA_PASSKEY ?? "";
const CB_URL = process.env.MPESA_CB_URL ?? "";

type StkParams = {
  amount: number;
  phone: string;
  accountRef: string;
  desc?: string;
};

function normalize(phone: string): string {
  const digits = phone.replace(/\D/g, "");
  if (digits.startsWith("0")) {
    return "254" + digits.slice(1);
  }
  return digits;
}

function stamp(): string {
  const d = new Date();
  const p = (n: number) => String(n).padStart(2, "0");
  let s = String(d.getFullYear());
  s += p(d.getMonth() + 1) + p(d.getDate());
  s += p(d.getHours()) + p(d.getMinutes());
  s += p(d.getSeconds());
  return s;
}

function password(time: string): string {
  const raw = SHORTCODE + PASSKEY + time;
  return Buffer.from(raw).toString("base64");
}

async function getToken(): Promise<string> {
  const raw = KEY + ":" + SECRET;
  const creds = Buffer.from(raw).toString("base64");
  const url = API + AUTH_PATH + "?" + AUTH_QS;
  const res = await fetch(url, {
    headers: { Authorization: "Basic " + creds },
  });
  if (!res.ok) {
    throw new Error("Token failed: " + res.status);
  }
  return (await res.json()).access_token;
}

export async function stkPush(p: StkParams) {
  const at = await getToken();
  const time = stamp();
  const payload = {
    BusinessShortCode: SHORTCODE,
    Password: password(time),
    Timestamp: time,
    TransactionType: "CustomerPayBillOnline",
    Amount: p.amount,
    PartyA: normalize(p.phone),
    PartyB: SHORTCODE,
    PhoneNumber: normalize(p.phone),
    CallBackURL: CB_URL,
    AccountReference: p.accountRef,
    TransactionDesc: p.desc ?? "",
  };

  const res = await fetch(API + STK_PATH, {
    method: "POST",
    headers: {
      Authorization: "Bearer " + at,
      "Content-Type": "application/json",
    },
    body: JSON.stringify(payload),
  });
  if (!res.ok) {
    const text = await res.text();
    throw new Error(res.status + ": " + text);
  }
  return res.json();
}

import { createMpesa } from
  "@singularity-payments/core";

// Reads MPESA_* env vars for you.
const mpesa = createMpesa();
const res = await mpesa.stkPush({
  amount: 100,
  phoneNumber: "254708374149",
  accountReference: "ORDER-123",
});