kompress_eshop/docs/integrations/README.md

# Carrier integrations

This eshop manages **delivery options** as plain rows in the `shipping_methods`
table (admin UI at `/admin/shipping` — add / edit price + toggle / remove). A
delivery option is just a name, a price, and two flags. **None of that talks to
a carrier yet** — it only decides what the customer can pick and how much they
pay.

Integrating a real carrier (Packeta, DPD, DHL) means wiring two *separate*
concerns on top of an existing delivery option:

1. **Pickup-point selection** (checkout, browser-side) — only for carriers that
   deliver to pickup points / lockers. The customer picks a point via the
   carrier's JS map widget; the chosen id + name land in the order.
2. **Shipment creation** (server-side, after the order is placed) — you call the
   carrier's HTTP API to register the parcel, then store the returned tracking
   number and print the label.

These are independent: you can ship to a Packeta pickup point manually (no API)
just by enabling the pickup widget, and you can create DHL labels via API for a
home-delivery option that has no pickup point at all.

> ❗ This is **not** a many-to-many / database relationship between your tables.
> A carrier is an **external HTTP API** you call from the server. The only
> schema you add is a few columns (which carrier a method maps to; a tracking
> number on the order) — see "Shared groundwork" below.

## What already exists in the codebase

| Piece | Where | Status |
|---|---|---|
| Delivery option CRUD | `src/controllers/admin_shipping.rs`, `assets/views/admin/shipping/index.html` | ✅ done |
| `shipping_methods` table (`code`, `name`, `price_cents`, `requires_pickup_point`, `enabled`, `position`) | `migration/.../m20260616_150755_shipping_methods.rs` | ✅ done |
| Carrier choice + pickup fields on checkout | `assets/views/shop/checkout.html` (`carrier_code`, `pickup_point_id`, `pickup_point_name`) | ✅ done |
| Order stores carrier + pickup point | `orders` table (`carrier_code`, `carrier_name`, `pickup_point_id`, `pickup_point_name`, `shipping_cents`) | ✅ done |
| Settings lookup | `src/shared/settings.rs` → reads `settings.*` from `config/*.yaml` | ✅ done |
| Packeta pickup-point widget | `assets/views/shop/checkout.html` (loads when `packeta_api_key` set) | ✅ scaffolded |
| `shipping_methods.carrier` (which API a method maps to) | `migration/.../m20260617_000001_*` + admin add-form dropdown | ✅ done |
| Tracking / shipment id / label on order | `migration/.../m20260617_000002_*` (`orders.tracking_number`, `shipment_id`, `label_url`) | ✅ done |
| Manual "Send to carrier" admin action | `src/controllers/admin_orders.rs` (`ship`), order detail page | ✅ done |
| Carrier client dispatch | `src/integrations/` (`create_shipment`) | ✅ done |
| Packeta shipment client | `src/integrations/packeta.rs` (real `createPacket`) | ✅ done |
| DPD / DHL shipment clients | `src/integrations/dpd.rs`, `dhl.rs` | 🟡 credential-guarded stub — fill in HTTP call per contract |

**Shipments are created only when an admin clicks "Send to carrier" on the order
page** — never automatically at checkout. Packeta is wired end-to-end (needs
just the API password + sender label). DPD/DHL run through the same flow but
their HTTP body must be finalised against your contract (clearly marked TODOs in
each file).

## Shared groundwork (do this once, before any carrier's API step)

The pickup-widget half needs nothing new. The **shipment-creation** half needs:

1. **An HTTP client dependency.** Add to `Cargo.toml`:
   ```toml
   reqwest = { version = "0.12", features = ["json"] }
   ```
   (Loco already pulls `tokio`/`serde`/`serde_json`.)

2. **A place for carrier clients.** Create `src/integrations/mod.rs` and a file
   per carrier (`packeta.rs`, `dpd.rs`, `dhl.rs`). Register `pub mod integrations;`
   in `src/lib.rs` (next to `pub mod controllers;` etc.).

3. **Map a delivery option to a carrier.** Add a `carrier` column to
   `shipping_methods` so each admin-created option knows which API (if any) to
   call. Generate the migration:
   ```bash
   cargo loco generate migration add_carrier_to_shipping_methods carrier:string
   ```
   Values: `none` (manual, the default), `packeta`, `dpd`, `dhl`. Then add a
   `<select name="carrier">` to the add-form in
   `assets/views/admin/shipping/index.html` and persist it in
   `admin_shipping::create`.

4. **Store the tracking number / label on the order.** Generate:
   ```bash
   cargo loco generate migration add_tracking_to_orders \
     tracking_number:string shipment_id:string label_url:string
   ```

5. **A "Create shipment" admin action.** In the admin order detail
   (`src/controllers/admin_orders.rs`), add a button/handler that: looks up the
   order's `carrier_code` → finds the `shipping_methods.carrier` → calls the
   matching `integrations::<carrier>::create_shipment(...)` → saves
   `tracking_number` + `label_url` back onto the order. Optionally do this
   automatically in `orders::place`, but a manual admin trigger is safer to
   start (you can review the order first).

After the groundwork, each carrier file implements one async function roughly
like:

```rust
pub struct ShipmentRequest<'a> {
    pub order_number: &'a str,
    pub recipient_name: &'a str,
    pub email: &'a str,
    pub phone: Option<&'a str>,
    pub address: Option<&'a str>,
    pub city: Option<&'a str>,
    pub zip: Option<&'a str>,
    pub country: Option<&'a str>,
    pub pickup_point_id: Option<&'a str>,
    pub cod_cents: i64,         // 0 unless cash-on-delivery
    pub currency: &'a str,
    pub weight_grams: i32,
}

pub struct ShipmentResult {
    pub shipment_id: String,
    pub tracking_number: String,
    pub label_url: Option<String>,
}

pub async fn create_shipment(ctx: &AppContext, req: ShipmentRequest<'_>) -> loco_rs::Result<ShipmentResult> { ... }
```

## Read next

- [`packeta.md`](packeta.md) — Packeta / Zásilkovna (pickup points + home, SK/CZ-centric)
- [`dpd.md`](dpd.md) — DPD (home delivery + Pickup parcelshops)
- [`dhl.md`](dhl.md) — DHL (international, Parcel/Express)

> ⚠️ Carrier APIs change. Treat the endpoint names, field names, and auth
> details here as a **map of the moving parts**, and confirm exact request
> formats against each carrier's current developer portal before coding.