# `middleware/domain-resolver.ts`

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## Purpose

Factory that builds a Hono middleware which resolves the incoming request's `Host` header to a `site` + `organization` and injects them into the request context. The middleware is the canonical hook applications install at the top of their route stack so downstream handlers can use `c.get("site")` / `c.get("organization")` without re-resolving on every endpoint. It is exposed as a service (`domainResolverMiddleware`) by the plugin's `onInit` so unrelated plugins can install it positionally without importing the package directly.

The middleware never errors on miss — it falls through with no context keys set. This matches the upstream behaviour and keeps the same instance reusable on route trees containing both site-bound and unbound endpoints.

## Features

- Reads `Host` then `X-Forwarded-Host` so reverse-proxied deployments work.
- Strips the port via `host.split(":")` before lookup.
- Normalises through `normalizeDomain` so the value passed to the resolver is canonical.
- Injects `site`, `organization`, `siteId`, `organizationId` on success.
- Silent fall-through on miss — downstream is free to 404 or render maintenance.

## Usage: Basic

```ts
import { createDomainResolverMiddleware } from "@suaveplan/api-plugin-site/middleware/domain-resolver";

const middleware = createDomainResolverMiddleware(resolver);
app.use("*", middleware);
```

## Usage: Advanced

```ts
import { createDomainResolverMiddleware } from "@suaveplan/api-plugin-site/middleware/domain-resolver";

// Wrap to enforce site presence on a specific subtree.
const middleware = createDomainResolverMiddleware(resolver);
app.use("/site", async (c, next) => {
    await middleware(c, next);
    if (c.get("site") === undefined) {
        return c.json({ error: "Site not found for host" }, 404);
    }
});
```

## API Reference

- `type DomainResolverMiddleware = (c: Context, next: Next) => Promise<void | Response>`.
- `createDomainResolverMiddleware(resolver: DomainResolverService): DomainResolverMiddleware`.

## Implementation Notes

- The middleware does not throw on a resolver error — the resolver's own error path already records the `error` outcome on the OTel counter. Throwing here would force every consumer to wrap the entire request in try/catch.
- `X-Forwarded-Host` is consulted only when `Host` is absent; if both are present we trust the proxy by deferring to the inner header set, matching the upstream convention.
- The four injected context keys are typed via the `hono` `ContextVariableMap` augmentation (consumers can re-declare for their app), but the middleware itself does not augment the global declaration to avoid namespace collisions with siblings.