---
phase: 01-driver-sidecar-migration
plan: 01
subsystem: driver
tags: [openvr, threading, command-queue, cmake, ctest, cpp17]

requires: []
provides:
  - "micmap::driver::CommandQueue — thread-safe bounded (depth=8, drop-oldest) PressCommand queue"
  - "micmap::driver::PressCommand primitive with Kind::{Down,Up}"
  - "micmap::driver::VRInputErrorName — stringifier for 21 vr::EVRInputError enumerants"
  - "test_command_queue — CTest-registered unit test asserting push/try_pop/drop-oldest/depth-8 contract"
affects: [01-driver-sidecar-migration/03-device-provider-rewrite, 01-driver-sidecar-migration/04-http-server-rewrite]

tech-stack:
  added: []
  patterns:
    - "Header-only driver primitives under driver/src/ (not added to driver/CMakeLists.txt sources; consumed via #include)"
    - "Framework-less CTest unit test using <cassert> + main(), matching existing test_placeholder convention"
    - "Switch without default: return 'Unknown' after the switch so adding a new SDK enumerant triggers -Wswitch (compile-time flag for maintenance)"

key-files:
  created:
    - driver/src/command_queue.hpp
    - driver/src/vr_error.hpp
    - tests/test_command_queue.cpp
  modified:
    - tests/CMakeLists.txt

key-decisions:
  - "CommandQueue depth fixed at 8 with drop-oldest (SVR-05) — worst-case memory = 8 * sizeof(PressCommand) bytes"
  - "VRInputErrorName omits default: label in switch; 'Unknown' fallthrough sits after the switch to preserve -Wswitch coverage"
  - "Test harness does not link OpenVR — CommandQueue header is pure stdlib, so the test target stays simple and fast"

patterns-established:
  - "Header-only cross-thread primitives live in driver/src/ with namespace micmap::driver and are NOT added to driver_micmap source list (downstream .cpp files pull them in transitively)"
  - "Unit tests for header-only driver primitives live in tests/ and include via target_include_directories(... ${CMAKE_SOURCE_DIR}/driver/src)"

requirements-completed: [SVR-05, SVR-10]

duration: ~11 min
completed: 2026-04-23
---

# Phase 01 Plan 01: Driver Primitives + Unit Test Summary

**CommandQueue (mutex-guarded std::deque, depth=8, drop-oldest) and VRInputErrorName (21-enumerant stringifier) landed as header-only `micmap::driver` primitives, with a framework-less CTest unit test that asserts push/try_pop/drop-oldest/depth-8 semantics and passes locally.**

## Performance

- **Duration:** ~11 min
- **Started:** 2026-04-23T08:02:30Z (approx — plan execution entry)
- **Completed:** 2026-04-23T08:13:30Z
- **Tasks:** 2
- **Files modified:** 4 (3 created + 1 modified)

## Accomplishments

- Landed `driver/src/command_queue.hpp` — `micmap::driver::CommandQueue` + `PressCommand{Kind::Down|Up}`, `kMaxDepth = 8`, mutex-guarded `push()` (returns `true` on drop-oldest overflow) and `try_pop()` (non-blocking, returns `std::optional`).
- Landed `driver/src/vr_error.hpp` — `inline const char* VRInputErrorName(vr::EVRInputError)` covering 21 SDK enumerants in order, with the `"Unknown"` fallthrough after the switch (preserves `-Wswitch` coverage for future SDK additions).
- Landed `tests/test_command_queue.cpp` — framework-less `main()` that exercises empty-pop-nullopt, push-then-pop round-trip, drop-oldest-on-9th-push, and `static_assert(kMaxDepth == 8)`.
- Registered `test_command_queue` in `tests/CMakeLists.txt` with `target_include_directories` pointing at `${CMAKE_SOURCE_DIR}/driver/src`; no OpenVR link; `test_placeholder` stanza preserved.

## Task Commits

Each task was committed atomically:

1. **Task 1: Create CommandQueue + VRInputErrorName headers** — `2798855` (feat)
2. **Task 2: Unit test for CommandQueue + register in CTest** — `26763c0` (test)

## Files Created/Modified

- `driver/src/command_queue.hpp` — created; thread-safe bounded command queue (depth=8, drop-oldest) + `PressCommand` primitive. Pure stdlib (`<deque>`, `<mutex>`, `<optional>`), namespace `micmap::driver`.
- `driver/src/vr_error.hpp` — created; `VRInputErrorName(vr::EVRInputError)` switch over 21 SDK enumerants returning stable short C-strings; `"Unknown"` after switch.
- `tests/test_command_queue.cpp` — created; framework-less `main()` with `<cassert>` exercising the CommandQueue contract.
- `tests/CMakeLists.txt` — modified; added `add_executable(test_command_queue ...)` + `target_compile_features` + `target_include_directories(... /driver/src)` + `add_test(NAME test_command_queue ...)`. `test_placeholder` stanza preserved intact.

## Verification

- `grep -q 'class CommandQueue' driver/src/command_queue.hpp` → PASS
- `grep -c 'case vr::VRInputError_' driver/src/vr_error.hpp` → `21` (PASS)
- `grep -E 'command_queue|vr_error' driver/CMakeLists.txt` → empty (PASS — header-only, not in driver source list)
- `grep -rn 'micmap/common/logger.hpp' driver/src/` → empty (PASS — driver/app log-sink separation intact)
- CMake configure + build of `test_command_queue` target succeeded (MSVC Debug; OpenVR SDK not present in worktree, driver build skipped — not required by this plan).
- CTest output (verbatim tail):
  ```
  Test project C:/Users/decid/Documents/projects/mic-map/.claude/worktrees/agent-a1454420/build
      Start 2: test_command_queue
  1/1 Test #2: test_command_queue ...............   Passed    0.03 sec

  100% tests passed, 0 tests failed out of 1
  ```

## Decisions Made

- None beyond those encoded in the plan. CommandQueue depth and drop-oldest semantics, switch style in `VRInputErrorName`, and the "no OpenVR link for the test" choice were all plan-specified; they are recorded in `key-decisions` above for downstream discoverability.

## Deviations from Plan

None — plan executed exactly as written. Both headers are verbatim copies of the plan's `<interfaces>` block content. The test file matches the plan's inline code example. `tests/CMakeLists.txt` gained exactly the new stanza specified in the plan's `<action>` block.

## Issues Encountered

- **Working-directory confusion at execution start:** The Bash tool resets cwd between invocations, and an initial pair of `Write` calls landed the headers in the parent repo (`C:/Users/decid/Documents/projects/mic-map`) instead of the worktree (`C:/Users/decid/Documents/projects/mic-map/.claude/worktrees/agent-a1454420`). Resolved by `git reset HEAD` + `rm` on the parent repo copies, then re-writing to the worktree-absolute paths. Zero impact on the final artifact set — the final committed files live in the worktree, and the main repo is clean of the accidental writes.

## Threat Flags

None — all surface introduced by this plan is in-scope for the plan's `<threat_model>` (T-01-01..T-01-04). No new network endpoints, auth paths, file access, or schema changes.

## Known Stubs

None.

## Next Phase Readiness

- **Wave 2 unblocked:** Plan 03 (`device_provider` rewrite) and Plan 04 (`http_server` rewrite) can now `#include "command_queue.hpp"` and `#include "vr_error.hpp"` without further plumbing. Both headers live on the driver include path already exposed via `target_include_directories(driver_micmap PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src)`.
- **Test infrastructure validated:** Framework-less `main()` tests work end-to-end through CMake + CTest. Future driver-primitive unit tests can reuse this pattern without adopting Google Test.
- **SVR-05 automated coverage:** The queue's depth-8 / drop-oldest contract is now runtime-asserted AND compile-time-asserted (`static_assert`). Any future refactor that changes the depth or drops the semantics will fail the build or the test.
- **No blockers.**

## Self-Check: PASSED

Claims verified:

- `driver/src/command_queue.hpp` — FOUND
- `driver/src/vr_error.hpp` — FOUND
- `tests/test_command_queue.cpp` — FOUND
- `tests/CMakeLists.txt` — modified (contains `add_executable(test_command_queue ...)` and `add_test(NAME test_command_queue ...)`)
- Commit `2798855` — FOUND in `git log`
- Commit `26763c0` — FOUND in `git log`
- CTest run — PASSED (1/1)

---
*Phase: 01-driver-sidecar-migration*
*Completed: 2026-04-23*