Commit Graph

2 Commits

Author SHA1 Message Date
Suriya
30d6d1080f Give every terminal its own identity, and report fleet presence
Answers "which of my 100 tills are alive and healthy", and fixes three things
that were fine on one device and broken on a hundred.

Terminal identity (lib/data/local/terminal_identity.dart)
- Every device mints a UUID on first run, stored in its own database, plus a
  short code (T4A9) derived from it. Renaming keeps the device id, so history
  keeps pointing at the same physical till.
- Replaces the literal 'TERM-01', which was hardcoded in five places. The whole
  fleet reported as one terminal: shift reports merged, MQTT topics collided,
  and a second connection with the same client id evicts the first from the
  broker — so two tills would have knocked each other offline in a loop.

Invoice numbers now carry the terminal code
- INV-2608-T4A9-00042. The sequence counter lives in each till's own database
  and starts at 1, so without this every terminal in the fleet minted
  INV-2608-00001 for its first sale of the month. The order UUID kept the data
  distinct; the number a customer quotes on a receipt was not.

SQLite pragmas
- WAL, so the product grid refreshing does not block the sale being written,
  and the file is never left mid-rewrite by a power cut.
- busy_timeout 5s, so a contended lock waits instead of throwing "database is
  locked" — which at checkout is a failed sale with a customer standing there.
- synchronous NORMAL, the right trade under WAL for a till.

Fleet presence (lib/data/sync/presence_reporter.dart)
- Retained status record on connect and once a minute: device id, code, name,
  app version, pending bill count, last upload, catalogue revision, sync halt
  state. Retained so a dashboard connecting at noon gets all 100 terminals
  immediately rather than a blank board.
- The Last Will already said "reachable". A till can be connected and still be
  holding 200 unsent bills or running last month's prices; only pending_bills
  and catalogue_revision say so.

NATS
- The MQTT gateway maps / to . so the existing transport works unchanged.
  SyncConfig.asNatsSubject() exposes the translation, and the contract doc
  gives the JetStream subjects (pos.*.*.order, pos.*.*.status) plus the two
  server-side requirements: a file-backed stream, and the ack published by the
  consumer after commit rather than by the ingest handler.

Tests: 129 -> 140. New coverage for identity minting and stability, per-device
invoice uniqueness, topic and client-id separation, NATS subject mapping, and
the two pragmas. Suite run three times clean.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-08-01 11:17:23 +05:30
Suriya
0a49323858 Drain bills to the back office automatically, over MQTT or HTTP
Turns the orders table into a queue that empties itself. Bills were only
uploaded when a cashier pressed Sync at end of day; a till that was never
pressed held a day's takings indefinitely.

Drain engine (lib/data/sync/sync_engine.dart)
- Triggers on sale committed, network regained, 5-minute poll, head-office
  request, and the manual button.
- Single flight: a busy till firing a trigger per sale would otherwise have
  several passes reading the same pending rows and send every bill twice.
  A trigger arriving mid-drain is queued and replayed, so nothing is dropped.
- Exponential backoff with +/-20% jitter to a 5-minute ceiling. The jitter
  matters: a store's terminals all fail at the same instant when the line
  drops, and would retry in lockstep without it.
- Halts rather than loops on a failure retrying cannot fix (bad credential,
  refused batch). Pressing Sync clears the halt.

Transports (lib/data/remote/)
- OrderTransport interface; MQTT, HTTP and simulated implementations. The
  repository does not know which is in use.
- MQTT: QoS 1 uplink, application-level ACK correlated by batch_id on a return
  topic, retained Last Will for terminal-offline detection, downlink for
  catalogue pushes and remote sync requests.
- A broker PUBACK is never treated as acceptance. It means the broker holds
  the bytes, not that the ledger took the sale. Only ids the back office names
  are marked synced; silence leaves a bill pending.
- HTTP carries a stable idempotency key across retries of the same bills.

Retention
- Accepted bills are kept 7 days instead of deleted, so a batch the back
  office later loses can be re-sent in full. Purged after that; archived
  totals stay forever.
- forBusinessDate now reads pending rows only. A retained bill exists in both
  the orders table and day_archive, and summing both would overstate the day.

Fixes found while building this
- SyncEngine._refreshPending wrote state.copyWith(pending: await ...). Dart
  evaluates the receiver before the awaited argument, so a connectivity drop
  during the wait was silently overwritten by the stale snapshot. Caught by
  the first run of the new engine tests.
- PrinterSettingsController wrote state after four awaits with no mounted
  check, throwing "used after dispose" when Settings was left mid-load. This
  was pre-existing and reached the cashier as a red screen.

Also
- Header pill now reports real sync state: LIVE / n QUEUED / SYNCING /
  SYNC HALTED, with an explanation of where the bills are.
- Settings shows the route, last upload, next retry and retention window.
- docs/sync-contract.md states what the back office must implement, including
  the idempotency requirement that at-least-once delivery makes mandatory.

Tests: 90 -> 129 passing. New coverage for backoff shape and jitter band,
single flight, halting, ACK correlation and partial acceptance, at-least-once
duplicate handling, retention and purge, and no double-counting after a sync.
Suite run six times clean.

Not addressed: bills already synced by an older build went up overstated and
still need server-side reconciliation. Broker credentials have no Settings
editor yet.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-08-01 10:57:29 +05:30