impl: start on OpenAPI prototype (#59)

While we prefer protos as an input into the generator, we want to prototype
using OpenAPI as an alternative input. This PR introduces a new "translator"
for OpenAPI, a rough implementation for messages and field, and some initial
tests.

.typos.toml

@@ -0,0 +1,20 @@
+# Copyright 2024 Google LLC
+#
+# 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
+#
+#     https://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.
+
+[files]
+extend-exclude = [
+    # The test data have typos, or at least uncommon spelling. We do not care
+    # about them as they are not customer visible.
+    "generator/**/testdata/**",
+]

generator/cmd/openapi/main.go

@@ -0,0 +1,80 @@
+// Copyright 2024 Google LLC
+//
+// 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
+//
+//     https://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 (
+	"flag"
+	"io"
+	"log"
+	"log/slog"
+	"os"
+
+	"github.com/googleapis/google-cloud-rust/generator/internal/genclient"
+	"github.com/googleapis/google-cloud-rust/generator/internal/genclient/translator/openapi"
+)
+
+func main() {
+	inputPath := flag.String("input-path", "", "the path to a file with an OpenAPI v3 JSON object")
+	outDir := flag.String("out-dir", "", "the path to the output directory")
+	language := flag.String("language", "", "the generated language")
+	templateDir := flag.String("template-dir", "templates/", "the path to the template directory")
+	flag.Parse()
+
+	if err := run(*inputPath, *language, *outDir, *templateDir); err != nil {
+		log.Fatal(err)
+		os.Exit(1)
+	}
+	slog.Info("Generation Completed Successfully")
+}
+
+func run(inputPath, language, outDir, templateDir string) error {
+	var (
+		contents []byte
+		err      error
+	)
+	if inputPath == "" {
+		contents, err = io.ReadAll(os.Stdin)
+		if err != nil {
+			return err
+		}
+	} else {
+		contents, err = os.ReadFile(inputPath)
+		if err != nil {
+			return err
+		}
+	}
+	return generateFrom(contents, language, outDir, templateDir)
+}
+
+func generateFrom(contents []byte, language, outDir, templateDir string) error {
+	translator, err := openapi.NewTranslator(contents, &openapi.Options{
+		Language:    language,
+		OutDir:      outDir,
+		TemplateDir: templateDir,
+	})
+	if err != nil {
+		return err
+	}
+	req, err := translator.Translate()
+	if err != nil {
+		return err
+	}
+
+	if _, err := genclient.Generate(req); err != nil {
+		return err
+	}
+
+	return nil
+}