HC_APTBS/.claude/skills/kwp-review/SKILL.md

KWP/FTDI edit checklist

You are about to edit timing-sensitive K-Line communication code in one of:

• Infrastructure/Kwp/KwpCommon.cs
• Infrastructure/Kwp/KW1281Connection.cs
• Infrastructure/Kwp/FtdiInterface.cs
• Services/Impl/KwpService.cs

Read the relevant file(s) first, then apply the following checks before and after your edit.

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Timing constraints

KW1281Connection.SendPacket calls Thread.Sleep(5) after each byte written. This is the mandatory KWP inter-byte gap. Do not remove or reduce it.

KwpCommon.WakeUp implements the 5-baud slow-init sequence. Any change to Sleep durations here will break ECU connection. Leave it alone unless you are explicitly fixing a timing bug and have the KW1281 spec in front of you.

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FtdiInterface lifetime

KwpService constructs a FtdiInterface at the start of each operation and disposes it at the end. This is intentional — the ECU expects a fresh session per dialog. Do not try to hold FtdiInterface open across multiple KwpService calls.

FtdiInterface._buf is a reused byte[1] field for single-byte reads/writes. Do not allocate a new array inside ReadByte() or WriteByteRaw().

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Error handling invariant

Every KwpService method that opens an FtdiInterface must dispose it in all code paths:

FtdiInterface? iface = null;
try
{
    iface = new FtdiInterface(port, KLineBaudRate);
    // ... work ...
}
catch (Exception ex) { /* log */ }
finally { iface?.Dispose(); }

If you add a new KwpService method, verify it follows this pattern. K-Line errors throw InvalidOperationException or TimeoutException. Do not catch and swallow these inside the method body — the ViewModel catch block depends on seeing them.

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Allocation patterns (known debt — do not worsen)

KW1281Connection uses List<byte> for packet buffers throughout. If you want to reduce allocations, convert the entire packet path at once. Converting one method in isolation creates a mixed pattern that is harder to reason about.

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After your edit, verify:

1. Search for new FtdiInterface — every occurrence has a matching finally { iface?.Dispose(); }
2. Thread.Sleep(5) in SendPacket is still present
3. ProgressChanged is still called with increasing percent values so the progress dialog updates
4. No new Thread.Sleep, Console.Write, or Logger.WriteLine was added inside a per-byte loop