# Architecture diagrams

Visual cross-cuts of `apf_portal`'s architecture. Each diagram summarises decisions that are spread across several ADRs and exists to help a contributor (or auditor, RSSI, IT contact) build a mental model fast. Decisions themselves live in [decisions/](decisions/); diagrams reflect the current accepted state.

Diagrams are written in [Mermaid](https://mermaid.js.org/) — text in markdown, rendered natively by Gitea, GitHub, and most IDE markdown viewers. Updating a diagram is an ordinary text edit reviewable in PR.

When a diagram is the _content_ of a single decision (e.g. a sequence diagram that captures a flow described by one ADR), it lives **inside that ADR**, not here. This file holds the _cross-cutting_ views.

---

## 1. System context (C4 level 1)

The portal as a black box, with the actors that interact with it and the external systems it depends on.

Sources: [ADR-0008](decisions/0008-identity-model-entra-workforce-dual-audience.md) (identity model), [ADR-0014](decisions/0014-downstream-api-access-obo-pattern.md) (downstream APIs), [ADR-0013](decisions/0013-audit-trail-separated-postgres-append-only.md) (audit access).

```mermaid
flowchart TB
  workforce([Workforce user<br/>employee])
  customer([Customer user<br/>external<br/>future])
  it([IT / Identity admin])
  rssi([RSSI / SOC analyst])

  portal[apf_portal<br/>web portal centralising<br/>access to existing apps]

  entra[(Microsoft Entra ID<br/>workforce tenant<br/>+ M365 Developer dev tenant)]
  extid[(Microsoft Entra External ID<br/>customer tenant<br/>future)]
  downstream[(Downstream APIs<br/>existing applications<br/>integrated by the portal)]

  workforce -->|browser HTTPS| portal
  customer -.->|browser HTTPS<br/>future| portal
  portal -->|OIDC Auth Code + PKCE| entra
  portal -.->|OIDC Auth Code + PKCE<br/>future| extid
  portal -->|OBO or signed assertion| downstream
  it -->|configures<br/>tenant + Conditional Access<br/>+ B2B invitations| entra
  rssi -->|reads audit events<br/>via audit_reader role| portal

  classDef future stroke-dasharray: 5 5,opacity:0.7
  class customer,extid future
```

Dashed = future scope (not v1). The customer audience is _designed for_ but not implemented (per the dual-audience design in ADR-0008); it is shown to make the future expansion legible.

---

## 2. Containers (C4 level 2)

The runtime artefacts and their conversations. One step deeper than system context: what is actually deployed.

Sources: [ADR-0002](decisions/0002-adopt-nx-monorepo-apps-preset.md) (Nx layout), [ADR-0004](decisions/0004-frontend-stack-angular-csr-zoneless-signals.md) (Angular SPA), [ADR-0005](decisions/0005-backend-stack-nestjs.md) (NestJS BFF), [ADR-0006](decisions/0006-persistence-postgresql-prisma.md) (Postgres + Prisma), [ADR-0009](decisions/0009-auth-flow-oidc-pkce-msal-node.md) (auth flow), [ADR-0010](decisions/0010-session-management-redis.md) (sessions in Redis), [ADR-0012](decisions/0012-observability-pino-opentelemetry.md) (OTel collector), [ADR-0014](decisions/0014-downstream-api-access-obo-pattern.md) (downstream calls).

```mermaid
flowchart TB
  user([Workforce user])

  subgraph Browser["Browser"]
    spa["portal-shell<br/>Angular 21 SPA<br/>zoneless / Signals / Tailwind 4"]
  end

  subgraph OnPrem["On-prem deployment"]
    bff["portal-bff<br/>NestJS 11 / Node 24<br/>Express adapter"]
    pg[("Postgres 17<br/>schemas: public + audit<br/>RLS for dual-audience")]
    redis[("Redis<br/>sessions + OBO token cache<br/>AES-256-GCM at rest")]
    otel["OTel Collector<br/>local sidecar<br/>(OTLP → backend, future)"]
  end

  entra[(Microsoft Entra ID)]
  downstream[(Downstream APIs)]

  user -->|HTTPS| spa
  spa -->|"HTTPS<br/>__Host-portal_session<br/>X-CSRF-Token<br/>traceparent"| bff
  spa -. "OTLP / HTTP<br/>(browser spans)" .-> otel
  bff -->|"OIDC Auth Code + PKCE<br/>via @azure/msal-node"| entra
  bff -->|Prisma 7| pg
  bff -->|"ioredis<br/>(opaque session id<br/>→ encrypted blob)"| redis
  bff -->|"OBO token (Entra-protected)<br/>or signed X-User-Assertion JWT<br/>+ traceparent"| downstream
  bff -. "OTLP / HTTP<br/>(server spans + Pino logs)" .-> otel
```

Notes embedded in the diagram:

- The SPA carries no token. Only the opaque session id cookie (`__Host-portal_session`) plus the CSRF cookie (`__Host-portal_csrf`, read by JS for double-submit).
- `traceparent` (W3C) propagates from the browser through the BFF to the downstream APIs — same `trace_id` end-to-end.
- The OTel Collector is the only piece coupled to the eventual on-prem observability backend. Choice of backend (Grafana Loki + Tempo, ELK, …) is deferred to the on-prem infrastructure ADR.

---

## 3. Nx module boundaries

Which projects are allowed to depend on which. Encoded in `eslint.config.mjs` via `@nx/enforce-module-boundaries` with the `depConstraints` from [ADR-0003](decisions/0003-workspace-and-app-naming-convention.md).

Each project carries two tags:

- **`scope:`** — `portal-shell`, `portal-bff`, or `shared` (for libs consumable by both apps).
- **`type:`** — `app`, `feature`, or `shared`.

A dependency is allowed only if both axes permit it.

```mermaid
flowchart LR
  subgraph Apps["apps · type:app"]
    shell["portal-shell<br/>scope:portal-shell"]
    bff["portal-bff<br/>scope:portal-bff"]
  end

  subgraph FeatureLibs["libs · type:feature"]
    fauth["feature-auth<br/>scope:portal-shell"]
  end

  subgraph SharedShellLibs["libs · type:shared · scope:portal-shell"]
    sui["shared-ui<br/>Angular components<br/>(spartan-style on CDK)"]
  end

  subgraph SharedAnyLibs["libs · type:shared · scope:shared"]
    stokens["shared-tokens<br/>design tokens (a11y)"]
    sutil["shared-util<br/>cross-runtime TS helpers"]
  end

  shell --> fauth
  shell --> sui
  shell --> stokens
  shell --> sutil

  bff --> stokens
  bff --> sutil

  fauth --> sui
  fauth --> stokens
  fauth --> sutil

  sui --> stokens

  classDef forbidden stroke:#c00,stroke-dasharray: 4 4
```

Forbidden by the depConstraints (and lint-enforced) — examples:

- `portal-bff` ⟶ `shared-ui` (back imports Angular code: scope clash).
- `portal-bff` ⟶ `feature-auth` (back imports a frontend feature).
- `shared-tokens` ⟶ `shared-ui` (a `type:shared` lib cannot reach a `type:shared` lib in a narrower scope, nor a feature lib).
- Any lib ⟶ any app.

---

## 4. CI/CD pipeline

How a change moves from a developer's keyboard to `main`. Reflects [ADR-0007](decisions/0007-pre-commit-hooks-and-conventional-commits.md) (local hooks), [ADR-0015](decisions/0015-cicd-gitea-actions.md) (Gitea Actions, trunk-based + squash-merge), [ADR-0016](decisions/0016-accessibility-baseline-wcag-aa-targeted-aaa.md) (a11y gate), [ADR-0017](decisions/0017-performance-budgets-lighthouse-ci.md) (perf gate).

```mermaid
flowchart TB
  edit[Edit on feat/*, fix/*, chore/*, docs/* branch]
  pre[".husky/pre-commit<br/>lint-staged → prettier on staged"]
  msg[".husky/commit-msg<br/>commitlint → Conventional Commits"]
  push[git push origin feat/*]
  pr[Open PR → main]

  subgraph PRJobs["CI on PR · .gitea/workflows/ci.yml · all blocking"]
    direction LR
    j1["check<br/>nx affected -t<br/>format / lint / test / build"]
    j2["scan<br/>pnpm audit + Trivy + gitleaks"]
    j3["commits<br/>commitlint on PR range"]
    j4["perf<br/>Lighthouse CI<br/>CWV thresholds (ADR-0017)"]
    j5["a11y<br/>axe-core via Playwright<br/>(placeholder until first screens)"]
  end

  protection{"Branch protection on main<br/>· all 5 jobs green<br/>· ≥0 reviewers (v1, →≥1 with 2nd contributor)<br/>· linear history<br/>· no direct push, no force push"}
  squash[Squash-merge<br/>subject = Conventional Commits<br/>(becomes the commit on main)]
  tag[Tag vX.Y.Z]
  release[".gitea/workflows/release.yml<br/>(stub today, populated with on-prem deploy ADR)"]

  edit --> pre --> msg --> push --> pr
  pr --> PRJobs --> protection -->|all green| squash --> tag --> release

  cron["Weekly cron · Mon 04:00 UTC"]
  sched[".gitea/workflows/security-scheduled.yml<br/>full-tree Trivy + gitleaks<br/>+ Lighthouse on prod (when LHCI_PROD_URL set)"]
  cron --> sched
```

Note the parallelism: the five PR jobs run **in parallel**. The diagram shows the gate as one square because branch protection requires _all five_ before squash-merge is allowed.

---

## To be added

As features land, the following diagrams will be added — either here, or inline in the ADR they belong to (per the convention stated at the top: _cross-cutting → here, single-decision → in the ADR_).

| Diagram                                                                                    | Where it will land                                                                             | Triggered by                                          |
| ------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------- | ----------------------------------------------------- |
| **OIDC Auth Code + PKCE sequence**                                                         | inline in [ADR-0009](decisions/0009-auth-flow-oidc-pkce-msal-node.md)                          | already useful — added at the same time as this file  |
| **Trace context propagation** (SPA → BFF → DB → downstream)                                | here                                                                                           | first observability instrumentation lands             |
| **Dual-audience flow** (token validation, claim → enum, RLS filtering)                     | here or split between ADRs 0008/0009/0013                                                      | first authz code that touches the audience            |
| **Step-up MFA flow** (claims challenge round-trip)                                         | inline in [ADR-0011](decisions/0011-mfa-enforcement-entra-conditional-access.md)               | first `@RequireMfa()` route                           |
| **Database ERD**                                                                           | inline in [ADR-0006](decisions/0006-persistence-postgresql-prisma.md) or a dedicated `data.md` | first business model in `schema.prisma`               |
| **Audit event lifecycle** (writer → store → archiver → reader)                             | inline in [ADR-0013](decisions/0013-audit-trail-separated-postgres-append-only.md)             | audit module shipped                                  |
| **Downstream call lifecycle** (audience pre-check → strategy → cache → resilience → trace) | inline in [ADR-0014](decisions/0014-downstream-api-access-obo-pattern.md)                      | first downstream integration                          |
| **Trust boundaries** (security review view)                                                | here                                                                                           | when the RSSI requests a security architecture review |