# Client Proto Generation

This document defines the stable protobuf inputs that official clients use to
generate language-specific gRPC bindings. The checked-in `.proto` files remain
the source of truth so clients do not drift from the gateway and worker
contracts.

## Stable Inputs

The stable client input manifest is `clients/proto/proto-inputs.json`. It
records:

- the public gateway protocol version,
- the worker IPC protocol version,
- the protobuf import root,
- the public and worker source files,
- the descriptor set path,
- golden fixture locations,
- behavior fixture locations,
- generated-code output directories for each planned client.

The source files listed by the manifest are:

- `src/MxGateway.Contracts/Protos/mxaccess_gateway.proto`
- `src/MxGateway.Contracts/Protos/mxaccess_worker.proto`

`mxaccess_gateway.proto` defines the public gRPC service and shared DTOs.
`mxaccess_worker.proto` is included in the descriptor because worker-aware
tests and fake-worker clients need the same command, reply, event, value, and
status shapes.

## Protocol Version

`GatewayContractInfo.GatewayProtocolVersion` is the public gateway protocol
version. `OpenSessionReply.gateway_protocol_version` returns the same value so
clients can compare their generated bindings against the gateway before issuing
MXAccess commands.

`GatewayContractInfo.WorkerProtocolVersion` remains the gateway-to-worker IPC
protocol version. It is also present in `OpenSessionReply` because parity
fixtures and fake-worker tests need to know the worker contract used by the
session.

## Descriptor Publishing

Run this command after changing either source `.proto` file or the client proto
manifest:

```powershell
scripts/publish-client-proto-inputs.ps1
```

The script writes
`clients/proto/descriptors/mxaccessgw-client-v1.protoset` with imports and
source information included. The descriptor is a generated artifact; do not edit
it by hand.

Use the check mode in CI or before committing:

```powershell
scripts/publish-client-proto-inputs.ps1 -Check
```

`-Check` rebuilds the descriptor in a temporary path and fails when the checked
in descriptor is stale.

## Output Directories

The manifest declares these generated-code directories:

| Client | Directory |
|--------|-----------|
| .NET | `clients/dotnet/generated` |
| Go | `clients/go/internal/generated` |
| Rust | `clients/rust/src/generated` |
| Python | `clients/python/src/mxgateway/generated` |
| Java | `clients/java/src/main/generated` |

Only generator output belongs in these directories. Handwritten client wrappers
belong in the language-specific source trees created by the client scaffold
issues.

## Language Generation Inputs

All generators use `src/MxGateway.Contracts/Protos` as the protobuf import
root. The checked-in descriptor is available when a language build prefers a
descriptor input, but the `.proto` files remain canonical.

.NET generation currently runs through the contracts project:

```powershell
dotnet build src/MxGateway.Contracts/MxGateway.Contracts.csproj
```

Future .NET client projects may either reference `MxGateway.Contracts` or
generate client-local files into `clients/dotnet/generated` with `Grpc.Tools`.

Go clients should generate `mxaccess_gateway.proto` and
`mxaccess_worker.proto` into `clients/go/internal/generated` with
`protoc-gen-go` and `protoc-gen-go-grpc`. Keep generated packages internal
unless the wrapper API intentionally exposes raw protobuf messages.

The Go scaffold provides a repo-local generation script:

```powershell
clients/go/generate-proto.ps1
```

The script maps both proto files into the internal Go package
`gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go/internal/generated` because
the source `.proto` files do not carry Go-specific `go_package` options. This
keeps language-specific packaging outside the public contract files.

Rust clients use `tonic-build` from `clients/rust/build.rs`. The build script
reads the shared `.proto` files and emits generated `tonic`/`prost` modules
into Cargo build output. `clients/rust/src/generated.rs` contains the module
declarations that include those generated files. `clients/rust/src/generated`
remains reserved for checked-in generator output if the crate later changes to
source-tree generation, and handwritten wrapper code stays outside that
directory.

Run the Rust workspace checks from `clients/rust`:

```powershell
cargo fmt --all --check
cargo test --workspace
cargo check --workspace
```

Python clients should use `grpc_tools.protoc` and write generated modules under
`clients/python/src/mxgateway/generated` so imports stay separate from
handwritten async wrappers.

The Python scaffold provides a repo-local generation script:

```powershell
clients/python/generate-proto.ps1
```

Java clients should use the Gradle protobuf plugin and write generated sources
under `clients/java/src/main/generated`. The Java client scaffold owns the
Gradle plugin versions and source-set wiring.

## Golden Fixtures

Golden protobuf JSON fixtures live in `clients/proto/fixtures/golden`. They
exercise payloads that every language client must parse:

- `open-session-reply.ok.json`
- `register-command-request.json`
- `on-data-change-event.json`

The fixtures use protobuf JSON field names and enum values. Contract tests parse
them with the generated C# types so schema drift is caught before client
generation work starts.

## Behavior Fixtures

Cross-language behavior fixtures live in
`clients/proto/fixtures/behavior`. The manifest
`clients/proto/fixtures/behavior/manifest.json` lists command replies, ordered
event stream samples, value conversion cases, status conversion cases, auth
error expectations, and timeout/cancel expectations.

The behavior fixtures let each generated client wrapper test the same
expectations without a live gateway. Protobuf message fixtures parse with the
generated types. Auth and timeout/cancel files describe wrapper behavior above
the generated transport layer, including credential redaction and the rule that
client cancellation does not abort an in-flight MXAccess COM call.

Run the focused validation script after changing these fixtures:

```powershell
scripts/validate-client-behavior-fixtures.ps1
```

## Related Documentation

- [Protobuf Contracts](./Contracts.md)
- [Client Libraries Detailed Design](./client-libraries-design.md)
- [Client Behavior Fixtures](./ClientBehaviorFixtures.md)
- [Client Libraries Implementation Plan](./implementation-plan-clients.md)
- [Protobuf Style Guide](./style-guides/ProtobufStyleGuide.md)