main.go

package main

import (
	"flag"
	"fmt"
	"strings"

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

func main() {
	var flags flag.FlagSet

	protogen.Options{
		ParamFunc: flags.Set,
	}.Run(func(gen *protogen.Plugin) error {
		gen.SupportedFeatures = uint64(pluginpb.CodeGeneratorResponse_FEATURE_PROTO3_OPTIONAL)

		for _, f := range gen.Files {
			if !f.Generate {
				continue
			}
			generateFile(gen, f)
		}
		return nil
	})
}

func getBaseName(name string) string {
	base_filename := name
	base_filename = base_filename[0 : len(base_filename)-6]
	return base_filename
}

func generateFile(gen *protogen.Plugin, file *protogen.File) *protogen.GeneratedFile {
	base_filename := getBaseName(file.Proto.GetName())

	filename := fmt.Sprintf("%s_grpc_async.ts", base_filename)

	m := make(map[string]bool)
	m[base_filename] = true
	for _, service := range file.Services {
		for _, method := range service.Methods {
			m[getBaseName(method.Input.Location.SourceFile)] = true
			m[getBaseName(method.Output.Location.SourceFile)] = true
		}
	}

	g := gen.NewGeneratedFile(filename, "")
	g.P("// Code generated by protoc-gen-grpc-async. DO NOT EDIT.")
	g.P()
	g.P("import * as grpc from \"@grpc/grpc-js\";")
	g.P("import * as gpb from \"./", base_filename, "_grpc_pb\";")
	for k, _ := range m {
		g.P("import * as ", k, "_pb from \"./", k, "_pb\";")
	}
	g.P()

	for _, service := range file.Services {
		g.P("export class Async", service.GoName, "Client {")
		g.P("  private readonly client: gpb.", service.GoName, "Client;")
		g.P()
		g.P("  constructor(client: gpb.", service.GoName, "Client) {")
		g.P("    this.client = client;")
		g.P("  }")
		for _, method := range service.Methods {
			name := method.GoName
			name = fmt.Sprintf("%s%s", strings.ToLower(name[0:1]), name[1:])

			ins := fmt.Sprintf("%s_pb", getBaseName(method.Input.Location.SourceFile))
			ons := fmt.Sprintf("%s_pb", getBaseName(method.Output.Location.SourceFile))

			g.P()
			g.P("  public async ", name, "(request: ", ins, ".", method.Input.GoIdent.GoName, "): Promise<", ons, ".", method.Output.GoIdent.GoName, "> {")
			g.P("    return new Promise((resolve, reject) => {")
			g.P("      this.client.", name, "(")
			g.P("        request,")
			g.P("        (err: grpc.ServiceError | null, value?: ", ons, ".", method.Output.GoIdent.GoName, ") => {")
			g.P("          if (err) {")
			g.P("            reject(err);")
			g.P("          } else {")
			g.P("            resolve(value!);")
			g.P("          }")
			g.P("        });")
			g.P("    });")
			g.P("  }")
		}
		g.P("}")
	}

	return g
}