apf_portal/docs/architecture.md

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/; diagrams reflect the current accepted state.

Diagrams are written in Mermaid — 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.

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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 (identity model), ADR-0014 (downstream APIs), ADR-0013 (audit access).

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.

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2. Containers (C4 level 2)

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

Sources: ADR-0002 (Nx layout), ADR-0004 (Angular SPA), ADR-0005 (NestJS BFF), ADR-0006 (Postgres + Prisma), ADR-0009 (auth flow), ADR-0010 (sessions in Redis), ADR-0012 (OTel collector), ADR-0014 (downstream calls).

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.

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.

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.

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4. CI/CD pipeline

How a change moves from a developer's keyboard to main. Reflects ADR-0007 (local hooks), ADR-0015 (Gitea Actions, trunk-based + squash-merge), ADR-0016 (a11y gate), ADR-0017 (perf gate).

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.

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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	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	first @RequireMfa() route
Database ERD	inline in ADR-0006 or a dedicated data.md	first business model in schema.prisma
Audit event lifecycle (writer → store → archiver → reader)	inline in ADR-0013	audit module shipped
Downstream call lifecycle (audience pre-check → strategy → cache → resilience → trace)	inline in ADR-0014	first downstream integration
Trust boundaries (security review view)	here	when the RSSI requests a security architecture review