julian
23919164ee
The device pushes button events to the backend via its Input Link URL feature;
the backend decides. No polling — the chosen entry architecture.
packages/devices:
- dingtian driver: configureInputPush() writes the device's input_link_url
config (per-input server/port/path, en=1, active-LOW, plain HTTP) so each
input HTTP-GETs the backend on press/release. Extracted #readConfig/#writeConfig
(with the required command:setconfig injection + post-write reset tolerance).
apps/server:
- routes/devices.ts: public GET/POST
/api/devices/dingtian/:deviceId/input/:n/{on,off} — translates a device push
into an internal device event. Not behind cookie/CSRF (machine call from the
device); trust comes from the signed event log, not this request.
- device-events.ts: internal EventEmitter bus so the entry flow subscribes to
input events without coupling to HTTP. Wired into the server.
Verified on hardware: configured the device, then real presses on all 4 inputs
pushed to the backend (input N on+off, source = device IP). No polling.
wiki: device-input-flow concept (path + trust model for the flat/no-VLAN
network); dingtian-relay updated; index + log.
54 lines
2.7 KiB
Markdown
54 lines
2.7 KiB
Markdown
---
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type: concept
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tags: [parking, architecture, devices, entry-flow]
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sources: []
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updated: 2026-06-15
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---
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# Device Input Flow (button → backend → relay)
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How a physical button press drives the entry lane. The **backend is the source of truth**: the
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device only *reports* the press; the host decides and commands the relay. This is the host-in-the-
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loop flow the [[dingtian-relay]] makes possible (and the [[uhppote-controller]] could not).
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## The path (no polling)
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```
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car arrives → driver presses button (input I_N, dry contact to GND)
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→ device HTTP-pushes GET …/api/devices/dingtian/<deviceId>/input/<N>/on
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→ backend: emit internal device event (device-events bus)
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→ backend entry flow: create + sign an entry event, print the ticket
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→ backend: pulseOpen(N) over UDP → barrier opens
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→ (on release) device pushes …/input/<N>/off
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```
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- **Push, not poll.** The device's `input_link_url` feature is configured (by the driver's
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`configureInputPush()`) to call the backend on each input edge — see [[dingtian-relay]]. The
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driver's poll path remains only as a dev/fallback aid.
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- **Per-input path** carries the input number in the URL (`…/input/3/on`), so routing needs no
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body parsing. Both edges (`on`/`off`) are sent.
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- **Internal event bus** (`device-events.ts`, a Node `EventEmitter`) decouples the HTTP/transport
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layer from business logic — drivers/pushes emit; the entry flow subscribes. Keeps the app
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[[device-adapter-pattern|device-agnostic]].
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## Trust model (important — flat network, no VLAN)
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The relay-control direction (host → device) is **unauthenticated UDP**, and the site is a **flat
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network with no VLAN** ([[network-isolation]] is not yet enforceable here). So we do **not** trust
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the device or the network. Instead:
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- **Every barrier open is a host decision, recorded as a signed event BEFORE the relay fires**
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([[append-only-event-chain]]). If anyone opens the relay out-of-band (which the flat network
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allows), there is **no matching signed event → a detectable anomaly**. The anti-fraud guarantee
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is the **signed log**, not device/network auth.
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- The inbound push endpoint is intentionally **not behind the SPA's cookie/CSRF auth** (it's a
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machine call from the device). A **shared-secret / Basic-auth** on the push is available as
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defence-in-depth (the device supports it) — worth adding, but it is *not* the security boundary.
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- This sharpens under the [[autonomous-direction|unmanned]] roadmap: with no operator, tamper
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detection via the signed log matters more than perimeter auth.
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## Status
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Input push **verified on hardware** (all 4 inputs, real presses reaching the backend). The entry
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flow itself (signed event + ticket print + `pulseOpen`) is the next build — see [[dingtian-relay]].
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