ttrpc/cmd/protoc-gen-go-ttrpc/generator.go

/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package main

import (
	"strings"

	"google.golang.org/protobuf/compiler/protogen"
)

// generator is a Go code generator that uses ttrpc.Server and ttrpc.Client.
// Unlike the original gogo version, this doesn't generate serializers for message types and
// let protoc-gen-go handle them.
type generator struct {
	out *protogen.GeneratedFile

	ident struct {
		context string
		server  string
		client  string
		method  string
	}
}

func newGenerator(out *protogen.GeneratedFile) *generator {
	gen := generator{out: out}
	gen.ident.context = out.QualifiedGoIdent(protogen.GoIdent{
		GoImportPath: "context",
		GoName:       "Context",
	})
	gen.ident.server = out.QualifiedGoIdent(protogen.GoIdent{
		GoImportPath: "github.com/containerd/ttrpc",
		GoName:       "Server",
	})
	gen.ident.client = out.QualifiedGoIdent(protogen.GoIdent{
		GoImportPath: "github.com/containerd/ttrpc",
		GoName:       "Client",
	})
	gen.ident.method = out.QualifiedGoIdent(protogen.GoIdent{
		GoImportPath: "github.com/containerd/ttrpc",
		GoName:       "Method",
	})
	return &gen
}

func generate(plugin *protogen.Plugin, input *protogen.File) error {
	file := plugin.NewGeneratedFile(input.GeneratedFilenamePrefix+"_ttrpc.pb.go", input.GoImportPath)
	file.P("// Code generated by protoc-gen-go-ttrpc. DO NOT EDIT.")
	file.P("// source: ", input.Desc.Path())
	file.P("package ", input.GoPackageName)

	gen := newGenerator(file)
	for _, service := range input.Services {
		gen.genService(service)
	}
	return nil
}

func (gen *generator) genService(service *protogen.Service) {
	fullName := service.Desc.FullName()
	p := gen.out

	serviceName := service.GoName + "Service"
	p.P("type ", serviceName, " interface{")
	for _, method := range service.Methods {
		p.P(method.GoName,
			"(ctx ", gen.ident.context, ",",
			"req *", method.Input.GoIdent, ")",
			"(*", method.Output.GoIdent, ", error)")
	}
	p.P("}")

	// registration method
	p.P("func Register", serviceName, "(srv *", gen.ident.server, ", svc ", serviceName, "){")
	p.P(`srv.Register("`, fullName, `", map[string]`, gen.ident.method, "{")
	for _, method := range service.Methods {
		p.P(`"`, method.GoName, `": func(ctx `, gen.ident.context, ", unmarshal func(interface{}) error)(interface{}, error){")
		p.P("var req ", method.Input.GoIdent)
		p.P("if err := unmarshal(&req); err != nil {")
		p.P("return nil, err")
		p.P("}")
		p.P("return svc.", method.GoName, "(ctx, &req)")
		p.P("},")
	}
	p.P("})")
	p.P("}")

	clientType := service.GoName + "Client"
	clientStructType := strings.ToLower(clientType[:1]) + clientType[1:]
	p.P("type ", clientStructType, " struct{")
	p.P("client *", gen.ident.client)
	p.P("}")
	p.P("func New", clientType, "(client *", gen.ident.client, ")", serviceName, "{")
	p.P("return &", clientStructType, "{")
	p.P("client:client,")
	p.P("}")
	p.P("}")

	for _, method := range service.Methods {
		p.P("func (c *", clientStructType, ")", method.GoName, "(",
			"ctx ", gen.ident.context, ",",
			"req *", method.Input.GoIdent, ")",
			"(*", method.Output.GoIdent, ", error){")
		p.P("var resp ", method.Output.GoIdent)
		p.P(`if err := c.client.Call(ctx, "`, fullName, `", "`, method.Desc.Name(), `", req, &resp); err != nil {`)
		p.P("return nil, err")
		p.P("}")
		p.P("return &resp, nil")
		p.P("}")
	}
}