[MS-1444] Reset accumulators upon scanner disconnect to prevent lefto…

[BurningAXE]

…ver bytes from corrupting parsing on next connection

JIRA ticket
Will be released in: 2026.2.0

Root cause analysis (for bugfixes only)

First known affected version: since forever

• See ticket for reproduction steps
• What happens upon timeout is that the Accumulator's buffer is not cleared so there are some leftover bytes from the previous connection when a new one is established. This leads to parsing errors that then lead to consistent timeouts and reconnections. Since the whole thing is a singleton, the only way to recover is to kill the app.

Notable changes

• Added an explicit reset in the Accumulator that is called upon disconnect. This should be safe since there is no use case where we want state preservation through reconnects.

Testing guidance

• Test a few normal/happy paths
• Check out the ticket for reproduction steps of the bug

Additional work checklist

• Effect on other features and security has been considered
• Design document marked as "In development" (if applicable)
• External (Gitbook) and internal (Confluence) Documentation is up to date (or ticket created)
• Test cases in Testiny are up to date (or ticket created)
• Other teams notified about the changes (if applicable)

[Copilot]

Pull request overview

This PR addresses a scanner reconnection edge case in the fingerprint scanner v2 pipeline by ensuring accumulator state is cleared on disconnect, preventing partial/leftover bytes from corrupting parsing after a reconnect.

Changes:

• Add a reset() API to the generic Accumulator to restore its initial empty state.
• Invoke accumulator resets during disconnect flows in RootMessageInputStream, PacketRouter, and MainMessageInputStream.
• Add/extend unit tests to validate resets happen on disconnect and that reset prevents partial-header contamination.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
fingerprint/infra/scanner/src/test/java/com/simprints/fingerprint/infra/scanner/v2/tools/accumulator/AccumulatorTest.kt	Adds coverage proving reset() clears partial state so subsequent elements parse correctly.
fingerprint/infra/scanner/src/test/java/com/simprints/fingerprint/infra/scanner/v2/incoming/root/RootMessageInputStreamTest.kt	Verifies root accumulator is reset on disconnect.
fingerprint/infra/scanner/src/test/java/com/simprints/fingerprint/infra/scanner/v2/incoming/main/packet/PacketRouterTest.kt	Verifies packet accumulator is reset on disconnect.
fingerprint/infra/scanner/src/test/java/com/simprints/fingerprint/infra/scanner/v2/incoming/main/MainMessageInputStreamTest.kt	Verifies all main-mode message accumulators are reset on disconnect.
fingerprint/infra/scanner/src/main/java/com/simprints/fingerprint/infra/scanner/v2/tools/accumulator/Accumulator.kt	Introduces reset() and stores the initial collection to support resetting.
fingerprint/infra/scanner/src/main/java/com/simprints/fingerprint/infra/scanner/v2/incoming/root/RootMessageInputStream.kt	Resets root response accumulator on disconnect.
fingerprint/infra/scanner/src/main/java/com/simprints/fingerprint/infra/scanner/v2/incoming/main/packet/PacketRouter.kt	Resets byte-array-to-packet accumulator on disconnect.
fingerprint/infra/scanner/src/main/java/com/simprints/fingerprint/infra/scanner/v2/incoming/main/MainMessageInputStream.kt	Resets all message accumulators on disconnect in addition to disconnecting the packet router.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud