🚧 Web UI

README.md

@@ -156,6 +156,33 @@ terminal, in `docker logs`, and in `journalctl` alike. Read vs write
 mappings are annotated correctly per the manual's Tables 119/120
 (e.g. word address `0x0000` reads as `%IW0` but writes to `%QW0`).
 
+## Web UI
+
+`serve` starts a browser UI alongside the Modbus server (spec §10):
+
+```bash
+wago-sim serve --node config/pump_node.yaml --port 5020
+# Web UI on http://127.0.0.1:8080 — default login: admin / simu
+```
+
+- **Overview**: realistic DIN-rail view of the coupler + modules with
+  per-channel LEDs for digital I/O and bar/numeric indicators for
+  analog values; updates live via WebSocket — including changes made
+  by the PLC over Modbus.
+- **Manipulation**: click a DI/DO LED to toggle it (field side), or
+  force DO/AO master-side; AI values can be set directly. All writes
+  go through the simulator's internal data paths — never via Modbus
+  TCP — while keeping read-back mirrors and statistics consistent.
+- **Diagnostics**: watchdog status, statistics with reset, and
+  LED/module fault injection for FAT fault cases.
+
+Configuration options: `--no-web`, `--web-port <n>` or env
+`WAGO_SIM_WEB_PORT` (default 8080); credentials via
+`WAGO_SIM_WEB_USER` / `WAGO_SIM_WEB_PASSWORD` (defaults
+`admin` / `simu`); `WAGO_SIM_WEB_READONLY=1` for observation-only
+benches (all mutating endpoints answer 403). Plain HTTP — keep the
+port inside the bench network.
+
 ## Documentation
 
 - `docs/spec/software-spec.md` — the software specification
@@ -261,6 +288,47 @@ requirement ID for each item in parentheses.
       protocol tracing, diagnostics and fault injection (FR-14.2.5–
       14.2.6); scoping questions to answer before planning (§14.3).
 
+### Web UI (spec §10) — in implementation
+
+- [x] Spec §10.3–10.6 updated with binding implementation decisions:
+      FastAPI/Uvicorn in-process on the Modbus server's asyncio loop;
+      vanilla single-page front-end (no build step) with realistic
+      DIN-rail graphics and per-channel LEDs; session-cookie auth with
+      default credentials `admin`/`simu` (env-overridable,
+      read-only mode); backend API uses **only internal memory
+      handlers** (`WagoDatastore`, `VirtualNode`, registers,
+      watchdog, statistics) — never Modbus TCP; WebSocket live
+      updates; milestones M1–M6.
+- [x] M1: webui package (`src/wago_sim/webui/`: `app.py`, `auth.py`,
+      `state.py`, `api.py`, static SPA); session auth with scrypt
+      hashing, lockout after 5 failed logins, read-only mode
+      (`WAGO_SIM_WEB_READONLY`); `GET /api/node` with `DI0.1`-style
+      and Modbus addresses; CLI wiring `--web/--no-web`,
+      `--web-port`, env `WAGO_SIM_WEB_USER/PASSWORD/READONLY/
+      NO_WEB/WEB_PORT`; login page + SPA shell.
+- [x] M2: node overview page — DIN-rail strip with coupler block
+      (MS/NS/BF/SF LEDs), module bezels with article numbers,
+      per-channel LEDs for DI/DO, bar+numeric indicators for AI/AO,
+      live values via WebSocket (`/api/ws`, 10 Hz delta push),
+      `GET /api/values` snapshot.
+- [x] M3: manipulation — DI/DO toggle (field side via
+      `set_digital_input_channel`, master side via internal
+      `write_bits`/`write_words` dispatch so mirrors/statistics stay
+      consistent), AI value entry (raw counts), AO force;
+      unknown-channel → 404, kind-mismatch → 400, read-only → 403.
+- [x] M4: diagnostics — watchdog status card (0x1006/0x100A),
+      statistics table (0x1029 words) with reset, LED-error
+      (0x1020/0x1021) and module-diagnosis (0x1050) fault injection
+      and clear; SF LED on the coupler reflects injected LED errors.
+- [x] M5: configuration — coupler settings forms (watchdog time/masks/type/close-on-timeout via 0x1000–0x100B, response delay 0x1037, idle timeout 0x1030) with the device's own validation surfaced (writes refused while the watchdog runs → field error); module list editor over the 13-article catalog with SAVE CONFIG → live process-image rebuild (`rebuild_node`: datastore survives, values clear like a KBUS reset, 0x1022–0x1025 and 0x2030+ updated) + persistence to the node-config YAML via a comment-preserving custom emitter.
+- [ ] M6: scenario run view + alias-ownership rejection (FR-10.2.6,
+      FR-10.2.9) — deferred.
+- [x] Tests: 28 web-UI tests (`tests/test_webui.py`) via httpx
+      `ASGITransport` (in-process, no socket) + live verification:
+      browser SAVE CONFIG rebuilds the node and persists YAML; Modbus
+      master reads the module description (0x2030) correctly after the
+      loader-overlap register fix. Full suite: 206 passing.
+
 ### Framework gaps (spec §4 — Scenario & Macro Engine)
 
 - [ ] State machines: `states:` with entry actions, transitions on