Closes Phase 7 Gap 5: VirtualTagEngine called IHistoryWriter.Record per evaluation
when Historize=true but Phase7EngineComposer always passed NullHistoryWriter, so
virtual-tag history was computed but never persisted.
The fix:
- New RingBufferHistoryWriter implements both IHistoryWriter (write port for the
evaluation pipeline) and IHistorianDataSource (read port for IHistoryRouter so
OPC UA HistoryRead on virtual-tag nodes resolves here). Maintains one bounded
ring buffer (1000 samples, configurable) per tag path; Record() is O(1) and
never blocks evaluation.
- Phase7EngineComposer.Compose now accepts IHistoryRouter? and, when any
VirtualTagDefinition.Historize=true, creates a RingBufferHistoryWriter, passes
it to VirtualTagEngine as historyWriter, adds it to the disposables list, and
registers it under the "virtual:" prefix in the router for HistoryRead dispatch.
- Phase7Composer accepts IHistoryRouter? from DI (already registered as singleton
in Program.cs) and threads it through to Phase7EngineComposer.Compose.
- NullHistoryWriter remains as fallback when no tags request historization.
- 16 new unit tests in RingBufferHistoryWriterTests.cs cover ring-buffer semantics,
eviction, per-tag isolation, ReadRawAsync windowing, IHistorianDataSource stubs,
router registration, and the Historize=false / null-router fallback paths.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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