RELEASE PLAN — PHASE 14

VietGara — Advanced Printing & Templates

Version 14.0 — October 9, 2026 · Cloud: Google Cloud Platform (GCP) · Backend: Go

1. Introduction

• Counter: print a receipt on the thermal printer next to the till, from the phone or from the web.
• Stock room: print barcode labels for received goods.
• Garage owner: design the quote, voucher and slip templates without a developer.

Web browsers cannot discover printers, so the web uses the print dialog (Release 10.0) or the print agent below; the mobile apps discover printers on the garage Wi-Fi.

2. Overview of the 3 Releases

Release	Name	Main Modules	Demoable Value
14.0	Thermal & LAN Printing	Document/Print, mobile apps	K80/K57 receipts and labels from the phone to a network thermal printer
14.1	Print Agent	Print agent, Document/Print	Silent printing from the web console to the garage’s printers
14.2	Template Designer	Document/Print, web console	A garage designs its own quote, voucher and slip templates

3. Release Details

Release 14.0 — Thermal & LAN Printing

• Thermal templates (FR-DOC-06): K80 (80 mm) and K57 (57 mm) roll-paper templates for payment vouchers and quick quotes, rendered as ESC/POS from the same print model as Release 10.0.
• Mobile LAN printing (FR-DOC-07):
  • the Flutter apps discover printers by mDNS (_ipp._tcp, _pdl-datastream._tcp, _printer._tcp) and always offer manual IP entry, because many inexpensive printers do not advertise;
  • printers are stored per garage (name, address, protocol, paper size, default document types) and tested per device;
  • thermal printers receive ESC/POS over TCP 9100, A4 printers receive IPP;
  • iOS needs the local-network permission and declared Bonjour services.
• Web: browsers cannot discover printers, so the web keeps the print dialog (Release 10.0) or uses the agent of Release 14.1.
• Definition of Done: from a phone on the garage Wi-Fi, a payment voucher prints on a K80 thermal printer found automatically and on one entered by IP; a K57 template prints without clipping.
• Barcode labels (FR-INV-13). Small-label templates (for example 50 x 30 mm) print a part’s name, SKU and barcode on the thermal printer, from the part and from a goods receipt, so received goods can be labelled.

Release 14.1 — Print Agent

• Agent (FR-DOC-08): a small Go service installed on a garage PC (Windows first). It lists the PC’s printers from the operating system’s spooler, keeps an outbound secure WebSocket to VietGara, signs in with a garage-bound key, and prints jobs (PDF or ESC/POS) without a dialog.
• Backend and web console: agent pairing, the printers it reports, a “print to” choice per document type, job status and failure messages.
• Security review: the agent only accepts jobs for its own garage over an authenticated connection, never opens an inbound port, and stores nothing but its key and a short job queue. The review is part of the release.
• Definition of Done: from the web console a voucher prints silently on the thermal printer attached to the counter PC; a lost connection queues the job and prints it on reconnection; revoking the agent key stops it.

Release 14.2 — Template Designer

• Renderer. Add an HTML renderer behind the template interface of Release 10.0: a headless-Chromium PDF service (for example Gotenberg) rendering sanitized HTML produced from the template, so the web preview and the PDF are identical. The built-in Go templates keep working.
• Designer (FR-DOC-09, FR-DOC-03). A constrained block designer, not free HTML:
  • blocks: header with logo and legal details, party block, items table with chosen columns, totals, payment details, notes, footer;
  • fields come only from a whitelist of the print model; fonts, sizes, margins and colours are options;
  • paper size A4 or A5 (K80/K57 stay built-in);
  • templates are versioned; publishing creates an immutable version and printed documents keep the version they used;
  • a live preview with sample data, and “restore the default”.
• Security. The layout is stored as validated JSON and rendered through an escaping engine; no scripts, external URLs or arbitrary CSS are accepted.
• Definition of Done: a garage designs a quote template with its logo, a different column set and footer, previews it, publishes it, and a quote prints with it on A4; an older quote reprinted keeps its original template version.

4. Dependency Diagram

flowchart TD
  P13(["Phase 13 complete"]) --> R140["Release 14.0<br/>Thermal + LAN printing"]
  R140 --> R141["Release 14.1<br/>Print agent"]
  P13 --> R142["Release 14.2<br/>Template designer"]
  R141 --> DONE(["Phase 14 complete"])
  R142 --> DONE

The agent follows the thermal templates because it carries the same ESC/POS output to the web. The designer is independent and builds on the template registry of Release 10.0.