# PR#92: MatrixSource at a Mutation-CRAP of at Most 15

Version: patch

> **WARNING:** This document describes only the change applied in this PR.
> It may already be outdated once the next PR is merged.
> Historic PR documentation is not maintained along with new PRs; treat it as a snapshot.

## Related Links

- [werkregie PR#91](https://git.javagil.de/mi/werkregie/pulls/91), `matrix react`, which stops the relay for each reaction.

## Problem

`matrix react` needs `sync.lock`, which the running relay holds; an agent stops the relay for about 50 s per reaction.
The relay is to send the reaction itself, which changes `sources/MatrixSource.kt`.
A branch fails on each method above a Mutation-CRAP of 15 in a class it changes;
9 of its methods are above, `MatrixSource.message` at 812 on `main`, the highest of the nightly ratchet:
a complexity of 28 without a killed mutant, since only a homeserver could drive it.

## Non-Goals

- No change of behaviour.
- No reaction through the relay yet; that is the follow-up PR.

## Specification

None; the behaviour stays the same.

## Solution

The decisions move out of `MatrixSource` into functions that tests reach without a client;
what stays in `MatrixSource` is the glue to Trixnity, at a complexity of at most 3,
so that it stays at most 12 without a killed mutant (3² + 3).

- `MatrixEvents`, new: what `MatrixSource` takes from Trixnity, tested with Trixnity's own data classes:
  `incoming` decides which event is a message of someone else, `message` builds the `MatrixMessage`
  from event, room and members, `receiptTime` takes the newest read receipt,
  `baseUrl` and `isUrl` the homeserver, `crossSigned` the trust level of the device.
- `MatrixMessages`, free of the client library: `unread`, `roomOf`, `readIn`, `encrypted` and `decrypted`.
- `MatrixSource`: `decryptAgain` hands each row to `decrypted`;
  `login` and `verify` take the lock by `locked`, which the follow-up PR also uses;
  `verifyWith` takes its checks from `checkVerified`, `verifyBy`, `byRecoveryKey` and `byPassphrase`;
  `syncError` names the cause of an ended sync.
- New tests in [MatrixEventsTest](../../dashboard/src/test/kotlin/de/hoennig/werkregie/dashboard/sources/MatrixEventsTest.kt),
  [MatrixMessagesTest](../../dashboard/src/test/kotlin/de/hoennig/werkregie/dashboard/sources/MatrixMessagesTest.kt)
  and [MatrixSourceTest](../../dashboard/src/test/kotlin/de/hoennig/werkregie/dashboard/sources/MatrixSourceTest.kt).
- `pitestPartial mutationCrapCheck` against main: the highest Mutation-CRAP of `MatrixSource` is 12,
  of `MatrixEvents` 11 (`incoming`, all mutants killed).

The ratchet of the nightly run falls from 812 to 272, now `CodexSource.fetch`;
the change of `dashboard/build.gradle.kts` makes the check stricter, not weaker.

## Open Questions

None.

## Follow-up PRs

- [werkregie PR#93](https://git.javagil.de/mi/werkregie/pulls/93): `matrix react` no longer needs a stop of the relay.
  The relay, which holds `sync.lock`, sends the reaction with its own Matrix client, on request through a local socket.
  That PR changes `MatrixSource`, so it needs the limit of 15 that this PR reaches.