# Infrastructure
The shared [Hummingbird](https://github.com/hummingbird-project/hummingbird) toolkit the platform's services build on: declarative routing, hardened HTTP middlewares, pre-rendered and pre-compressed localized responses, and page and asset scaffolding.

## Overview
| Role | Types |
| --- | --- |
| Routing | `RouterController`, `RouteCollectionBuilder`, the `addController` extension on `RouterMethods` |
| Middlewares | `SecurityHeadersMiddleware`, `HTTPSRedirectMiddleware`, `TrailingSlashRedirectMiddleware`, `VaryMiddleware`, `CompressionMiddleware`, `RateLimitMiddleware`, `NotFoundMiddleware` |
| Pages and assets | `Page`, `Asset`, `AssetExtension`, `FingerprintAssets` |
| Link previews | `SocialCard`, its `locale` and the `alternateLocales` of its other language editions, its `Image` and `Style`, and the `Tag` meta tags it derives |
| Structured data | `StructuredData`, the `Node`, `Property`, and `Value` types of its schema.org graph, the open `Name` and `Kind` vocabularies, and the site-wide initializer building the `Organization`/`WebSite` pair |
| Analytics | `Analytics`, the `Event`s a page reports (with `tagging()` to apply one to any attribute-bearing HTML or SVG tag), the tracker script `Attribute`s it derives, the optional session `recorder` script paired with it, and the `origin` its preconnect hint targets |
| Responses | `CachedHTMLResponse` (rendered and gzipped once), `LocalizedHTMLCollectionResponse` (one of those per language) |
| Localization | The `Negotiate` extension resolving a request's language from its `lang` override, path prefix, and `Accept-Language` |
| Constants | The `HTTPField.Name` header names, `Int.RateLimit` limits, and `String.Security` header values the middlewares default to |

## Design rules
The package holds only what every service can reuse. Anything a service owns is injected, never referenced.
- **No site-specific content.** No page markup, no asset catalog, no `Bundle.module` lookups. What a type needs, it takes as a parameter: the `bundle:` whose String Catalog names the supported languages, the `document:` closure that builds a page for a locale, a `Page` conformer's `metadata` and its optional head concerns (`summary`, `canonicalURL`, `socialCard`, `structuredData`, `analytics`). URLs arrive absolute and fully formed — composing them stays with the page. The same holds for request semantics: only the caller knows whether it negotiates the language or pins it by route, so `variesOnAcceptLanguage:` declares whether the responses carry `Vary: Accept-Language`.
- **Types own their format; `Page` renders generically.** Each head concern derives its own render-ready form — `SocialCard.tags`, `StructuredData.payload`, `Analytics.attributes` — which `Page` applies without knowing the vocabulary. A page's `scripts` and the tracker render as `defer`red head tags, the tracker preceded by a `preconnect` to its cross-origin host.
- **Nodes are joined by `@id`, not repetition.** A node another page must point at gets its identifier from a helper rather than a hand-spelled fragment — `organizationID(forSiteURL:)` names the node the site-wide initializer builds, and that initializer's `founder` takes such an identifier back. A service adds the helper for any node it owns, so neither side can drift.
- **Services fill the gaps once, via extensions.** A service restores its convenient call sites retroactively — the Website's `*+Defaults` are the pattern. The open schema.org vocabularies work the same way: the package declares the shared `Property.Name` and `Node.Kind` constants, a service adds its own.
- **Method structs.** Single-operation types such as `FingerprintAssets` take lifetime-fixed configuration in `init` and per-call inputs in `callAsFunction`.
- **Wrap upstream, do not restate it.** Where a Hummingbird middleware is almost right, the package delegates to it and adds only the missing decision — `CompressionMiddleware` passes everything to `ResponseCompressionMiddleware` except responses that already name an encoding, which it would otherwise compress twice.
- **Ask where the answer is used.** Work every request pays for must be work every request needs. The request's language is negotiated by the responders that read it, not stamped onto a context on the way past.

## Layout
Sources are split by visibility, then by kind, one type per file:
```
Sources/
├── Public/                public API
│   ├── Builders/          RouteCollectionBuilder
│   ├── Enumerations/      AssetExtension
│   ├── Extensions/        addController, Analytics.Event tagging, and the request-language negotiation, plus the default header names, rate limits, and header values
│   ├── Methods/           FingerprintAssets
│   ├── Middlewares/       the seven HTTP middlewares
│   ├── Protocols/         Asset, Page, RouterController
│   ├── Responses/         CachedHTMLResponse, LocalizedHTMLCollectionResponse
│   └── Types/             Analytics, SocialCard, StructuredData — each nesting its own types in a folder of that name
└── Internal/
    ├── Extensions/        implementation details (the String separators)
    └── Types/             implementation details (FNV1aHash)
Tests/
├── Cases/                 the test suites, mirroring the Sources/ layout
├── Catalogs/              the String Catalog fixture, copied verbatim so it loads on Linux
└── Utils/                 stubs (StubAsset, StubPage, …) and the suite Tag constants
```

## Testing
Every suite carries a tag for the kind of API it exercises — `.asset`, `.extension`, `.middleware`, `.protocol`, `.type` — declared in `Tests/Utils/Extensions/Tag+Constants.swift`, so a run can be sliced by kind. A new suite takes the tag matching its subject, or adds one when none fits.

## Requirements
- Swift 6.3 toolchain (`swift-tools-version:6.3`).
- macOS 15, matching the sibling packages. The services deploy to Linux containers; the packages declare no UI platforms.
- Package dependencies: the local `Localization` package, `elementary`, `hummingbird`, and — for `CompressionMiddleware` and the responses' gzip — `hummingbird-compression` and `compress-nio`.