Session dan state machine alur pesanan

import Database from "better-sqlite3";

export const db = new Database("data/bot.db");

db.exec(
  "CREATE TABLE IF NOT EXISTS sessions(" +
  "  phone TEXT PRIMARY KEY," +
  "  state TEXT NOT NULL DEFAULT 'START'," +
  "  data  TEXT NOT NULL DEFAULT '{}'," +
  "  updated_at INTEGER);" +
  "CREATE TABLE IF NOT EXISTS processed(" +
  "  message_id TEXT PRIMARY KEY);"
);

export function getSession(phone) {
  const row = db
    .prepare("SELECT * FROM sessions WHERE phone = ?")
    .get(phone);
  if (!row) return { phone, state: "START", data: {} };
  return { phone, state: row.state, data: JSON.parse(row.data) };
}

export function saveSession(s) {
  db.prepare(
    "INSERT INTO sessions(phone, state, data, updated_at) " +
    "VALUES (?, ?, ?, unixepoch()) " +
    "ON CONFLICT(phone) DO UPDATE SET " +
    "state = excluded.state, data = excluded.data, " +
    "updated_at = excluded.updated_at",
  ).run(s.phone, s.state, JSON.stringify(s.data));
}

const MENU =
  "Halo! Balas dengan angka ya:\n" +
  "1. Menu & harga\n2. Buat pesanan\n3. Chat admin";

const PRICES = { A: 85000, B: 120000 };

export function step(session, text) {
  const t = text.trim().toLowerCase();
  if (t === "admin") return go("HUMAN", "Oke, admin akan membalas di sini ya.");

  switch (session.state) {
    case "START":
      return go("MENU", MENU);
    case "MENU":
      if (t === "1") return go("MENU", "Paket A Rp 85.000, Paket B Rp 120.000. Balas 2 untuk pesan.");
      if (t === "2") return go("ITEM", "Mau Paket A atau Paket B?");
      if (t === "3") return go("HUMAN", "Oke, admin akan membalas di sini ya.");
      return go("MENU", MENU);
    case "ITEM": {
      const item = t === "a" || t === "paket a" ? "A"
                 : t === "b" || t === "paket b" ? "B" : null;
      if (!item) return go("ITEM", "Balas A atau B ya.");
      session.data.item = item;
      return go("QTY", "Berapa box?");
    }
    case "QTY": {
      const qty = parseInt(t, 10);
      if (!qty || qty < 1 || qty > 500)
        return go("QTY", "Tulis angka saja ya, contoh: 2");
      session.data.qty = qty;
      session.data.total = qty * PRICES[session.data.item];
      return go("ADDRESS", "Alamat pengirimannya ke mana?");
    }
    case "ADDRESS":
      session.data.address = text.trim();
      return go(
        "CONFIRM",
        session.data.qty + " box Paket " + session.data.item +
        " ke " + session.data.address +
        ". Total Rp " + session.data.total.toLocaleString("id-ID") +
        ". Balas YA untuk lanjut bayar, atau UBAH."
      );
    case "CONFIRM":
      if (t === "ya") return go("PAYMENT", null, "create_invoice");
      if (t === "ubah") return go("MENU", MENU);
      return go("CONFIRM", "Balas YA atau UBAH ya.");
    default:
      return go("MENU", MENU);
  }

  function go(state, reply, action) {
    session.state = state;
    return { session, reply, action };
  }
}

// server.js
import { getSession, saveSession } from "./db.js";
import { step } from "./flow.js";
import { sendText } from "./wa.js";

app.post("/webhook", async (req, res) => {
  res.sendStatus(200);
  const msg = req.body?.entry?.[0]?.changes?.[0]?.value?.messages?.[0];
  if (!msg || msg.type !== "text") return;

  const session = getSession(msg.from);
  if (session.state === "HUMAN") return; // a person owns this chat now

  const { reply } = step(session, msg.text.body);
  saveSession(session);
  if (reply) await sendText(msg.from, reply);
});