Fix block-level cache contamination

[KTibow]

As reported in #216 (this PR fixes #216) and suffered by me and other transit apps, if any trip on a block had GTFS‑RT data, the cache returned a non‑empty location list, and predicted=true leaked to every trip on that block even if they had no RT data.

The fix adds a realtimeTripId field to BlockLocation - it records which trip the GTFS‑RT data actually belongs to. Then in applyRealTimeToStopTimeInstance, it checks isBlockLocationApplicableToInstance:

// Before: if locations was non-empty, ALL trips got predicted=true
if (locations.isEmpty()) { ... fall back to scheduled ... }

// After: only trips that actually match the RT data get predicted=true
if (!hasApplicableLocation) { ... fall back to scheduled ... }

The check says: a BlockLocation is "applicable" to a trip if either:

• It has a timepoint prediction for this specific trip, or
• Its realtimeTripId matches this trip

Otherwise the trip falls through to the scheduled‑only path, which produces predicted=false. No more schedule data wearing the predicted=true badge just because a different trip on the same block has real‑time data.

Disclosure: Generated by GPT-5.5.

Summary by CodeRabbit

• Bug Fixes
  • Improved real-time arrival/departure handling so predictions are applied only to the correct trip and do not leak to later trips in the same block.
  • Prevented duplicate trip instances in multi-vehicle scenarios, keeping arrivals and departures aligned with the intended vehicle.
  • Real-time trip matching is now more precise when evaluating whether a vehicle location should affect a stop prediction.

[CLAassistant]

All committers have signed the CLA.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a realtimeTripId field to BlockLocation, populated from VehicleLocationRecord data, and introduces applicability filtering in ArrivalAndDepartureServiceImpl so only realtime locations matching a StopTimeInstance's trip are applied, preventing prediction propagation into unrelated trips. Tests are updated and added accordingly.

Changes

Realtime trip applicability filtering

Layer / File(s)	Summary
BlockLocation realtimeTripId field and accessors .../services/realtime/BlockLocation.java, .../impl/realtime/AbstractBlockLocationServiceImpl.java	Adds a realtimeTripId field with getter/setter to BlockLocation, populated from VehicleLocationRecord.getTripId() during cache-based location construction.
Applicability check in ArrivalAndDepartureServiceImpl .../impl/ArrivalAndDepartureServiceImpl.java	Adds isBlockLocationApplicableToInstance and hasTimepointPredictionForTrip helpers, tracks a hasApplicableLocation flag while filtering realtime locations, and changes the fallback trigger from locations.isEmpty() to !hasApplicableLocation.
Test coverage for applicability filtering .../impl/ArrivalAndDepartureServiceImplTest.java	Updates propagation assertions to prevent prediction leakage into subsequent trips, adds a new test verifying no duplicate trip instances occur for a two-vehicle block, and adds supporting helper methods (getArrivalsAndDeparturesForTwoVehicleBlock, addVehicleLocationRecord, countArrivalsAndDeparturesForTrip).

Estimated code review effort: 3 (Moderate) | ~25 minutes

Sequence Diagram(s)

sequenceDiagram
  participant AbstractBlockLocationServiceImpl
  participant BlockLocation
  participant ArrivalAndDepartureServiceImpl
  participant StopTimeInstance

  AbstractBlockLocationServiceImpl->>BlockLocation: setRealtimeTripId(record.getTripId())
  ArrivalAndDepartureServiceImpl->>BlockLocation: getRealtimeTripId()
  ArrivalAndDepartureServiceImpl->>ArrivalAndDepartureServiceImpl: isBlockLocationApplicableToInstance(location, instance)
  ArrivalAndDepartureServiceImpl->>StopTimeInstance: compare trip id / check timepoint predictions
  alt location applicable
    ArrivalAndDepartureServiceImpl->>ArrivalAndDepartureServiceImpl: apply realtime prediction to instance
  else no applicable location
    ArrivalAndDepartureServiceImpl->>ArrivalAndDepartureServiceImpl: fall back to schedule-based instance
  end

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title matches the main fix: preventing cached block-level realtime data from leaking across trips.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[KTibow]

This CLA is wrong - it's currently displaying the default SAP SE corporate template.

[KTibow]

cc @aaronbrethorst - seems you added CONTRIBUTING.md referencing the CLA, but the CLA is wrong ("to SAP"):

Copyright License. You hereby grant, and agree to grant, to SAP a non-exclusive, perpetual, irrevocable, worldwide, fully-paid, royalty-free, transferable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, and distribute your Contributions and such derivative works, with the right to sublicense the foregoing rights through multiple tiers of sublicensees.