garmin gfdi v2 wire format

[abdulsaheel]

cobs + mlr multiplexing + gfdi frame/crc for garmin watches. covers the
close_all/register_ml handshake, the device-information push, current-time
answer, status ack, and a minimal protobuf reader/writer for one battery
round trip (Smart.device_status_service.remote_device_battery_status_*).

no ble here, bytes only. everything else in the protobuf container and the
numbered real-time streaming services are untouched.

Summary by Sourcery

Add experimental byte-level Garmin GFDI v2 protocol support for session setup, device identification, time synchronization, acknowledgements, and battery status exchange.

New Features:

• Add experimental Garmin GFDI v2 byte-level protocol support, including Multi-Link multiplexing, COBS framing, CRC validation, GFDI messages, device information, current-time responses, status acknowledgements, and battery-status protobuf exchange.

Enhancements:

• Expose the Garmin protocol through the package barrel while keeping BLE integration and unsupported streaming services out of scope.

Tests:

• Add coverage for Garmin framing, multiplexing, device information, time responses, acknowledgements, and battery protobuf parsing.

[sourcery-ai]

Reviewer's Guide

Introduces an experimental, BLE-independent Garmin GFDI v2 byte protocol stack: MLR session multiplexing, COBS transport framing, CRC-validated GFDI messages, selected device/session responses, and a minimal battery-status protobuf round trip, with comprehensive unit tests while leaving unrelated protobuf and streaming services untouched.

Sequence diagram for Garmin GFDI battery-status round trip

sequenceDiagram
    participant Host
    participant Watch

    Host->>Watch: garminCloseAllRequest()
    Watch-->>Host: GarminCloseAllAck
    Host->>Watch: garminRegisterMlRequest(kGarminServiceGfdi)
    Watch-->>Host: GarminRegisterMlResponse
    Watch-->>Host: GarminGfdiFrame DEVICE_INFORMATION
    Host->>Watch: garminBuildStatusAck(kGarminMsgDeviceInformation)
    Watch->>Host: garminBuildProtobufRequest()
    Host-->>Watch: garminBuildStatusAck(kGarminMsgProtobufRequest)
    Watch-->>Host: GarminGfdiFrame PROTOBUF_RESPONSE
    Host->>Host: garminParseBatteryResponseProto()
    Host->>Watch: garminBuildStatusAck(kGarminMsgProtobufResponse)

Loading

File-Level Changes

Change	Details	Files
Add a public, bytes-only Garmin GFDI v2 protocol implementation covering session setup, framing, selected control messages, and battery status exchange.	Export the new Garmin protocol API from the package barrel. Implement Multi-Link routing, CLOSE_ALL/REGISTER_ML handshake messages, and response decoding. Implement COBS encoding/decoding and notification reassembly. Implement Garmin nibble-table CRC16 and validated little-endian GFDI frame construction/parsing. Build and parse status acknowledgements, current-time responses, device-information pushes, and system events. Add a limited protobuf envelope and wire reader/writer for the Smart device-status battery request/response path, explicitly leaving chunked messages and other services unsupported.	lib/openstrap_protocol.dart lib/src/garmin.dart
Add unit coverage for the new Garmin wire-format layers and supported message paths.	Test COBS round trips, edge cases, and notification reassembly. Test CRC, GFDI validation, status acknowledgements, and time responses. Test MLR handshake/data decoding and device-information parsing. Test battery protobuf encoding/decoding and its GFDI envelope.	test/garmin_test.dart

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📥 Commits

Reviewing files that changed from the base of the PR and between c78c176 and d8f073b.

📒 Files selected for processing (3)

• lib/openstrap_protocol.dart
• lib/src/garmin.dart
• test/garmin_test.dart

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