DPE Project Structure

Workspace Layout

modules/dpe/
├── core/             dpe-core          Pure domain (serde only)
├── telemetry/        dpe-telemetry     Telemetry types and validation (serde only)
├── api-oai/          dpe-api-oai       OAI-PMH 2.0 endpoint
├── web/              dpe-web           Leptos SSR + Datastar fragments
├── server/           dpe-server        Axum binary (composition root)
├── web-e2e-tests/                      Playwright E2E tests
├── public/                             Static assets
└── style/                              Tailwind CSS

Dependency Graph

dpe-core              ← pure domain, no framework deps
  ↑
  ├── dpe-api-oai     ← OAI-PMH endpoint
  ├── dpe-web         ← Leptos SSR pages + components
  └── dpe-server      ← composition root, Datastar fragment handlers
       ↑
       dpe-telemetry  ← telemetry types and validation (serde only)

Crate Responsibilities

dpe-core (core/)

Framework-free domain layer. Contains:

• Domain types: Project, Record, Person, Organization, Attribution, etc.
• Repository traits: ProjectRepository, RecordRepository
• Fs implementations: FsProjectRepository, FsRecordRepository (backed by in-memory caches)
• Data loading: Project and record caches (OnceLock<Vec<T>>) loaded from JSON on first access
• Utilities: lang_value(), get_data_dir()

Dependencies: serde, serde_json only.

dpe-api-oai (api-oai/)

OAI-PMH 2.0 Data Provider. Implements the six required verbs (Identify, ListMetadataFormats, ListSets, ListIdentifiers, ListRecords, GetRecord).

Depends on dpe-core for domain types — no Leptos or web framework dependency.

dpe-web (web/)

Leptos SSR web layer. Contains:

• Pages: home, about, project, projects (with filters and pagination)
• Components: navbar, footer, project cards, tab panels, search input
• Domain re-exports: domain/mod.rs re-exports dpe-core types for a single import path
• Server functions: #[server] wrappers around dpe-core functions

dpe-telemetry (telemetry/)

Telemetry types and validation logic. Extracted as a library crate so fuzz targets can test the real code. Contains:

• Beacon types: BeaconPayload, Signal, WebVitalSignal, ErrorSignal, etc. (serde deserialization for browser beacons)
• Origin validation: is_allowed_origin() — validates dasch.swiss subdomains
• URL normalization: normalize_page_url() — cardinality-safe page URL mapping
• Traceparent validation: is_valid_traceparent() — W3C traceparent format validation

Dependencies: serde only.

dpe-server (server/)

Composition root and Axum binary. Contains:

• Route wiring: Leptos SSR routes, OAI-PMH handler, Datastar fragment endpoints, /healthz, /telemetry/collect
• Fragment handlers: fragments.rs — pure Axum handlers that render Leptos components to HTML and return Datastar SSE events
• Telemetry collector: telemetry_collector.rs — converts browser beacons to OTel metrics and structured logs (uses types from dpe-telemetry)
• Configuration: config.rs — figment-based layered config (defaults → dpe.toml → DPE_* env vars)
• Logging: OTel-aware subscriber via init-tracing-opentelemetry

Key Patterns

• Domain types in dpe-core, not in web or API crates
• API crates depend on dpe-core only, never on each other or on dpe-web
• dpe-server contains no business logic — only route composition and fragment rendering
• Fragment handlers use Owner::new() + view! { ... }.to_html() to render Leptos components from pure Axum handlers