[OpenAPI Generator](https://openapi-generator.tech) is used to generate protobuf schema (`.proto3`) files from OpenAPI specifications of MEC015 Traffic Management APIs.
>**NOTE:** At the time of writing, the tool does not support OAS 3.1 version and we have to first convert the [Traffic Management APIs](./BwManagementApi.yaml and ./TrafficSteeringApi.yaml) to OAS 3.0 for generating protobuf schema.
1. Convert OAS for [Traffic Management APIs](./BwManagementApi.yaml and ./TrafficSteeringApi.yaml) from 3.1 to 3.0
- Change the value of `openapi` field from 3.1.0 to 3.0.0
- Use this [VS code extension](https://marketplace.visualstudio.com/items?itemName=42Crunch.vscode-openapi) to see the errors in the downgraded YAML (v3.0)
- Manually fix the errors
- mostly related to `examples`<-->`example` interchange
- or some 3.1 fields that are not supported in 3.0 (comment them out)
2. Generate proto files
- Install the `openapi-generator-cli.jar` using the installation procedure mentioned [here](https://openapi-generator.tech/docs/installation#jar).
- Generate the proto files using the following commands:
3. Carefully inspect the generated `.proto` files for any inconsistencies. Some of the things to look out for:
- Proto3 generated files for enumerations, structures containing allOf, oneOf, anyOf etc. may need to be touched manually
- Check that all the nested models are being _imported_ correctly in their parent models
- Remove redundant proto files
4. Validate protobuf schema by generating code from proto3 descriptions in different languages. See [this section](#code-generation-from-proto3) for more details.
# Code Generation from proto3
Below are some code generation examples for Python, Go and Ruby. For other languages, please refer to https://grpc.io/docs/quickstart/.
### Python
1. Install the grpcio-tools package
```sh
$ pip install grpcio-tools
```
2. Create a directory for generated Python stubs
```sh
$ mkdir python-stubs
```
3. Run the following commands from the root of the directory containing this README that you are reading.
The above commands will generate two files for the BWM and MTS service:
- _bwm_service_pb2.py_: containing the python data models used in the BWM service file
- _bwm_service_pb2_grpc.py_: containing all the classes and functions needed for the supported HTTP methods in the BWM API
And two files for the MTS service:
- _mts_service_pb2.py_: containing the python data models used in the MTS service file
- _mts_service_pb2_grpc.py_: containing all the classes and functions needed for the supported HTTP methods in the MTS API
### Go
1. Install protocol buffer compiler
```sh
$ apt install-y protobuf-compiler
```
2. Install Go plugins for `protoc`
```sh
$ go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.28.1
```
```sh
$ go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@v1.2.0
```
3. Update `PATH` so `protoc` can find the plugins
```sh
$ export PATH="$PATH:$(go env GOPATH)/bin"
```
4. Define a go package by appending `option go_package = "./mec015.services.bwmservice";` or `option go_package = "./mec015.services.mtsservice";` in .proto files like this:
> The generated `<data_model>.pb.go` files will contain all the protocol buffer code to populate, serialize, and retrieve request and response message types defined in the `models` folder.
> The `bwm_service_grpc.pb.go` will contain the stubs for the methods defined in the `bwm_service.proto` file. And The `mts_service_grpc.pb.go` will contain the stubs for the methods defined in the `mts_service.proto` file.
### Ruby
1. Install gRPC Ruby Plugin and required tools
```sh
$ gem install grpc
$ sudo apt install ruby-grpc-tools
```
2. Generate code
```sh
$ mkdir ruby-stubs
```
Run the following commands to create Ruby modules for all the data models defined in the proto files.
Run the following commands to generate `bwm_service_pb.rb`, `bwm_service_services_pb.rb` and `mts_service_pb.rb`, `mts_service_services_pb.rb` files, containing stub and service classes for the endpoints and methods defined in MEC015 Traffic Management APIs.
