// inventory.js
import express from "express";
import { pool } from "./db.js"; // pg pool
const router = express.Router();

// Calculate how many server units are in this cart
const serverIds = new Set(["server1", "server2", "server3"]);

router.post("/api/reserve", async (req, res) => {
    const { items } = req.body;               // [{id, qty, price}]
    const want = items.filter(i => serverIds.has(i.id))
        .reduce((a, i) => a + i.qty, 0);

    if (want === 0) return res.json({ ok: true, remaining: await currentRemaining() });

    const client = await pool.connect();
    try {
        await client.query("BEGIN");
        const { rows } = await client.query("SELECT value_int FROM inventory_state WHERE key='server_slots_remaining' FOR UPDATE");
        const remaining = rows[0].value_int;

        if (remaining < want) {
            await client.query("ROLLBACK");
            return res.status(409).json({ ok: false, reason: "sold_out", remaining });
        }

        await client.query(
            "UPDATE inventory_state SET value_int = value_int - $1 WHERE key='server_slots_remaining'",
            [want]
        );
        await client.query("COMMIT");
        res.json({ ok: true, remaining: remaining - want });
    } catch (e) {
        await client.query("ROLLBACK"); throw e;
    } finally {
        client.release();
    }
});

async function currentRemaining() {
    const { rows } = await pool.query("SELECT value_int FROM inventory_state WHERE key='server_slots_remaining'");
    return rows[0].value_int;
}

router.get("/api/inventory", async (req, res) => {
    res.json({ remaining: await currentRemaining() });
});

export default router;