julien
7ee7b2dadf
## Summary
Records the decision to use **D3 + Observable Plot**, wrapped in a new `libs/shared/charts/`, as the chart toolkit shared by `portal-shell` and `portal-admin`. ADR-only — implementation lands as the next chantier(s).
This is staged as a 3-PR chantier per the agreed plan:
| PR | Périmètre |
| --- | --- |
| **PR 1 (this one)** | ADR-0023 — decision + a11y contract + bundle plan. |
| PR 2 | `libs/shared/charts/` foundations + 3 starter components (`<lib-bar-chart>`, `<lib-donut-chart>`, `<lib-stacked-bar-chart>`). |
| PR 3 | Integration on the `/audit` page — daily-volume bar + outcome-breakdown donut + event-type-over-time stacked bar. |
## What lands
### [`docs/decisions/0023-charts-d3-observable-plot.md`](docs/decisions/0023-charts-d3-observable-plot.md)
Full MADR 4.0.0 record. Highlights:
- **Choice**: D3 + Observable Plot, both from Mike Bostock / Observable Inc., both MIT, both past 1.0. Plot covers ~80 % of standard charts in declarative one-liners; D3 stays the escape hatch for bespoke viz (heatmap, sankey, …) inside the same lib.
- **Why not D3 alone**: ~250 LOC per chart × 4-5 types × a11y discipline = sustained code investment before the first dashboard ships.
- **Why not ECharts / Chart.js**: 600 KB minified + canvas-rendered + an `aria` plugin afterthought (ECharts), or narrower vocabulary + brittle dark-mode (Chart.js). Both furthest from the Angular-Signals-zoneless idiom the rest of the workspace runs on.
- **A11y contract** is baked into `_internal/` (palette, tabular fallback, SVG `<title>` / `<desc>` builders) so every chart inherits WCAG 2.2 AA + AAA-targeted compliance from the lib, not from contributor discipline. Six commitments, each unit-tested per chart component.
- **Bundle plan**: ~65 KB gzip added to a chart-bearing lazy chunk (d3 modules tree-shaken + Plot + thin wrapper) — well under [ADR-0017](docs/decisions/0017-performance-budgets-lighthouse-ci.md)'s 100 KB cap.
- **Component contract**: every `<lib-*-chart>` exposes the same Signal-based input shape (`[data]`, `[caption]`, `[description]`, `[ariaLabel]`, `[colorScheme]`) regardless of whether Plot or raw D3 powers the rendering.
### [`docs/decisions/README.md`](docs/decisions/README.md)
ADR-0023 added to the index table.
### [`CLAUDE.md`](CLAUDE.md)
- "Architecture (recorded in ADRs)" gains a "Charts + dashboards" bullet describing the lib + a11y baseline + bundle posture.
- "Repository status" bumps the ADR range to `0001 → 0023`.
- "Still on the roadmap" gains the charts implementation entry pointing at this ADR.
## Notes for the reviewer
- **Why honour the user's D3 preference rather than recommend pure ECharts?** D3 (and by extension Plot) is the closest match to the project's tech bar ("stable, recognized, battle-tested") for data-viz on the web; it's also the user's stated preference, and Plot's higher-level layer eliminates the "250 LOC per chart" cost that would otherwise push us toward an alternative. The ADR explicitly walks through ECharts + Chart.js as runners-up so future challengers see the trade-offs we chose against.
- **Why a single shared lib rather than per-app charts?** Both SPAs (portal-shell + portal-admin) will host dashboards. The chart vocabulary, a11y contract, palette, and theme integration are identical between the two — duplicating into app-local code would invite drift. The lib stays at `libs/shared/charts/` next to `libs/shared/ui/`.
- **Why the `_internal/` folder for cross-cutting code?** Single source of truth for the colour palette and the a11y plumbing. A lint rule (added in PR 2) will ban consumers from importing `d3-scale-chromatic` directly so the colour-blind-safe palette stays the only path.
- **Why no ADR amendment to ADR-0016 / ADR-0017?** Both are binding constraints, not superseded. The new ADR operationalises both for the chart surface; cross-references in the "Related ADRs" section make that explicit.
## Test plan
- [x] ADR validates as MADR 4.0.0 (frontmatter, section order, tag vocabulary).
- [x] No code touched — lint / test / build matrix unaffected.
- [x] `docs/decisions/README.md` index updated in the same change per the [ADR conventions](docs/decisions/README.md#conventions).
- [ ] Review for trade-off accuracy: are the bundle estimates fair? Is the "Plot covers ~80 % of standard charts" framing defensible against the user's mental model of D3?
- [ ] Implementation chantier (PR 2) lands directly behind this if accepted: `pnpm add -w d3 @observablehq/plot @types/d3`, `libs/shared/charts/` scaffold via `pnpm nx g @nx/angular:library --name=shared-charts --directory=libs/shared/charts --standalone=true --unitTestRunner=vitest-analog --tags="scope:shared,type:shared" --no-interactive`, then the 3 starter components.
## What's next
If accepted as-is, PR 2 (lib foundations + 3 starter components) follows. If a reviewer wants to push back on D3-vs-ECharts or on the a11y contract's strictness, this is the right PR to surface that — no implementation has started.
---------
Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #170
Architectural Decision Records
This project records architecturally-significant decisions as ADRs in the MADR 4.0.0 format. References: adr.github.io.
Why ADRs
ADRs capture the why behind a decision — context, drivers, options considered, trade-offs accepted — at the moment the decision is made. They make architecture reviewable, onboarding faster, and prevent the same debate from being re-litigated later.
Conventions
- Format: MADR 4.0.0. Start from template.md.
- Filename:
NNNN-kebab-case-title.md, e.g.0007-adopt-tailwind-for-design-tokens.md. - Numbering: globally sequential 4-digit prefix. Numbers never reset, never get reused — even when an ADR is superseded or deprecated.
- Layout: flat folder. ADRs are not nested into category subfolders; topical organization happens via tags.
- Tags: every ADR carries a
tags:array in the MADR frontmatter, drawn from the tag vocabulary below. An ADR may carry several tags. Propose new tags (or renames) in the same PR that needs them; never invent ad-hoc tags inline. - Status lifecycle:
proposed→accepted→ optionallydeprecatedorsuperseded by [ADR-NNNN](NNNN-other.md). Update the YAML frontmatter; never delete an ADR. - Index maintenance: every ADR addition or status change must update the Index below in the same commit.
When to write an ADR
Write one whenever a development decision is non-trivial: tool or library choice, framework pattern, security control, perf budget, a11y target, naming convention, deprecation, breaking change, or any choice that future contributors would benefit from understanding the why of.
Tag vocabulary
The vocabulary below is the source of truth. It is intentionally coarse — propose extensions only when an existing tag genuinely doesn't fit, and avoid overly narrow tags.
| Tag | Scope |
|---|---|
frontend |
UI, Angular, components, design system, client-side state |
backend |
API, BFF, server-side services |
security |
AuthN, AuthZ, sessions, CSP, dependency scanning, secret management |
performance |
Perf budgets, caching, bundle size, Lighthouse |
accessibility |
WCAG, a11y testing, keyboard, ARIA, contrast |
infrastructure |
CI/CD, hosting, deployment, runtime |
observability |
Logs, metrics, traces, correlation IDs, monitoring |
data |
Persistence, schemas, migrations, data flow |
process |
Team conventions, workflows, repo policy |
Status: starter vocabulary, to be refined as ADRs accumulate. Update this table whenever a tag is added, renamed, or retired.
Index
ADRs are listed in numerical order. To slice by topic, filter on the Tags column.
| # | Title | Status | Tags | Date |
|---|---|---|---|---|
| 0001 | Use ADRs to record architectural decisions | accepted | process |
2026-04-29 |
| 0002 | Adopt Nx monorepo with the apps preset |
accepted | infrastructure, frontend, backend |
2026-04-29 |
| 0003 | Workspace and app naming convention | accepted | process |
2026-04-29 |
| 0004 | Frontend stack — Angular (latest LTS), standalone, zoneless, Signals, CSR-only, Vitest | accepted | frontend |
2026-04-29 |
| 0005 | Backend stack — NestJS over Express, Fastify, Hono | accepted | backend |
2026-04-29 |
| 0006 | Persistence — PostgreSQL with Prisma | accepted | data, backend |
2026-04-29 |
| 0007 | Pre-commit hooks and Conventional Commits | accepted | process |
2026-04-29 |
| 0008 | Identity model — multi-tenant Entra ID for workforce, dual-audience design for future External ID | accepted | security, data |
2026-04-29 |
| 0009 | Authentication flow — OIDC Authorization Code + PKCE via MSAL Node, BFF session pattern | accepted | security, backend |
2026-04-29 |
| 0010 | Session management — opaque session IDs in cookies, payload in self-hosted Redis with AES-GCM at rest | accepted | security, backend, infrastructure |
2026-04-29 |
| 0011 | MFA enforcement — Entra ID Conditional Access baseline, BFF claim sanity-check, step-up hooks designed-in | accepted | security |
2026-04-29 |
| 0012 | Observability — Pino structured logs + OpenTelemetry tracing, W3C Trace Context propagation, stdout + collector | accepted | observability, backend, frontend |
2026-04-29 |
| 0013 | Audit trail — separated append-only Postgres schema, decoupled from app logs | accepted | security, observability, data |
2026-04-29 |
| 0014 | Downstream API access — On-Behalf-Of pattern, unified DownstreamApiClient, audience-aware authorization |
accepted | security, backend |
2026-04-29 |
| 0015 | CI/CD pipeline — Gitea Actions, trunk-based + squash-merge, thin YAML over portable scripts | accepted | infrastructure, process |
2026-04-30 |
| 0016 | Accessibility baseline — WCAG 2.2 AA + targeted AAA, Angular CDK + spartan-ng + Tailwind, APF panel testing | accepted | accessibility, frontend, process |
2026-04-30 |
| 0017 | Performance budgets — Core Web Vitals + Lighthouse CI gates, bundle budgets, BFF p95/p99 SLOs | accepted | performance, frontend, backend, process |
2026-04-30 |
| 0018 | Environment configuration — Angular environment.ts, BFF env vars, audit pool split |
accepted | frontend, backend, infrastructure, process |
2026-05-10 |
| 0019 | Internationalisation — @angular/localize, build-time per-locale bundles, /fr + /en path-based routing |
accepted | frontend, accessibility, performance, process |
2026-05-11 |
| 0020 | portal-admin — dedicated SPA for portal administration, sharing the existing BFF |
accepted | frontend, backend, security, infrastructure, process |
2026-05-11 |
| 0021 | Phase-2 security baseline — helmet, CORS allowlist, double-submit CSRF, rate limiting, structured error envelope | accepted | security, backend |
2026-05-13 |
| 0022 | Documentation site — VitePress + Mermaid plugin, separate static deployment | accepted | process, infrastructure |
2026-05-15 |
| 0023 | Charts + dashboards — D3 + Observable Plot wrapped in libs/shared/charts |
accepted | frontend, accessibility, performance |
2026-05-16 |