From 2a699bdb298532226a39d2ba4466d9cf1c79d4e0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tam=C3=A1s=20Gul=C3=A1csi?= <tamas@gulacsi.eu>
Date: Thu, 31 Oct 2024 14:59:06 +0100
Subject: [PATCH] begin protoc-gen-oracall

---
 lib/objects/objects.go                   |   5 +
 protoc-gen-oracall/protoc_gen_oracall.go | 136 +++++++++++++++++++++++
 2 files changed, 141 insertions(+)
 create mode 100644 protoc-gen-oracall/protoc_gen_oracall.go

diff --git a/lib/objects/objects.go b/lib/objects/objects.go
index 1ed9590..e6f1026 100644
--- a/lib/objects/objects.go
+++ b/lib/objects/objects.go
@@ -477,6 +477,11 @@ func (p protoImports) String() string {
 	return buf.String()
 }
 
+const (
+	MessageTypeExtension = 79396128
+	FieldTypeExtension   = 79396128
+)
+
 // a number between 1 and 536,870,911 with the following restrictions:
 // The given number must be unique among all fields for that message.
 // Field numbers 19,000 to 19,999 are reserved for the Protocol Buffers implementation. The protocol buffer compiler will complain if you use one of these reserved field numbers in your message.
diff --git a/protoc-gen-oracall/protoc_gen_oracall.go b/protoc-gen-oracall/protoc_gen_oracall.go
new file mode 100644
index 0000000..35b1b05
--- /dev/null
+++ b/protoc-gen-oracall/protoc_gen_oracall.go
@@ -0,0 +1,136 @@
+// Copyright 2024 Tamás Gulácsi. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"io"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+
+	oracall "github.com/tgulacsi/oracall/lib"
+	"google.golang.org/protobuf/compiler/protogen"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/pluginpb"
+)
+
+func main() {
+	if err := Main(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func Main() error {
+	// Protoc passes pluginpb.CodeGeneratorRequest in via stdin
+	// marshalled with Protobuf
+	input, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		return fmt.Errorf("slurp stdin: %w", err)
+	}
+	var req pluginpb.CodeGeneratorRequest
+	proto.Unmarshal(input, &req)
+
+	// Initialise our plugin with default options
+	opts := protogen.Options{}
+	plugin, err := opts.New(&req)
+	if err != nil {
+		panic(err)
+	}
+
+	// Protoc passes a slice of File structs for us to process
+	for _, file := range plugin.Files {
+		// log.Printf("? %q", file.GoImportPath.String())
+		if strings.HasPrefix(file.GoImportPath.String(), `"google.golang.org/`) {
+			log.Println("skip", file.GoImportPath.String())
+			continue
+		}
+		// var messageOption, fieldOption *protogen.Message
+		// for _, e := range file.Extensions {
+		// 	switch e.Extendee.Desc.FullName() {
+		// 	case "google.protobuf.MessageOptions":
+		// 		messageOption = e.Extendee
+		// 	case "google.protobuf.FieldOptions":
+		// 		fieldOption = e.Extendee
+		// 	}
+		// }
+
+		// Time to generate code...!
+		var buf bytes.Buffer
+
+		// 2. Write the package name
+		fmt.Fprintf(&buf, "// Code generated by protoc-gen-oracall. DO NOT EDIT!\n\npackage %s\n\n", file.GoPackageName)
+
+		for _, msg := range file.Proto.MessageType {
+			// FIXME[tgulacs]: this is a hack, but I couldn't find out how to get the extensions' options' values
+			optS := msg.Options.String()
+			opts, err := parseOption(optS)
+			if err != nil {
+				return fmt.Errorf("parse %q: %w", optS, err)
+			}
+			objectType := opts["objects.oracall_object_type"]
+			fmt.Fprintf(&buf, "\n// %q=%q\nfunc(%s) ObjecTypeName() string { return %q }\n",
+				*msg.Name, objectType,
+				*msg.Name, objectType,
+			)
+			fmt.Fprintf(&buf, "func (%s) FieldTypeName(f string) string{\n\tswitch f {\n", msg.GetName())
+			for _, f := range msg.Field {
+				optS := f.Options.String()
+				opts, err := parseOption(optS)
+				if err != nil {
+					return fmt.Errorf("parse %q: %w", optS, err)
+				}
+				fieldType := opts["objects.oracall_field_type"]
+				if fieldType == "" {
+					log.Printf("opts=%q fields=%+v", optS, opts)
+				}
+				fmt.Fprintf(&buf, "\t\t// %q.%q = %q\n\t\tcase %q, %q: return %q\n",
+					*msg.Name, oracall.CamelCase(f.GetName()), fieldType,
+					f.GetName(), oracall.CamelCase(f.GetName()), fieldType,
+				)
+			}
+			fmt.Fprintf(&buf, "}\n\treturn \"\"\n}\n")
+		}
+
+		// 4. Specify the output filename, in this case test.foo.go
+		filename := file.GeneratedFilenamePrefix + ".oracall.go"
+		file := plugin.NewGeneratedFile(filename, ".")
+
+		// 5. Pass the data from our buffer to the plugin file struct
+		out, err := format.Source(buf.Bytes())
+		if err != nil {
+			return err
+		}
+		file.Write(out)
+	}
+
+	// Generate a response from our plugin and marshall as protobuf
+	stdout := plugin.Response()
+	out, err := proto.Marshal(stdout)
+	if err != nil {
+		return err
+	}
+
+	// Write the response to stdout, to be picked up by protoc
+	_, err = os.Stdout.Write(out)
+	return err
+}
+
+// parseOption parses the [option.name]:"value" stringified option.
+func parseOption(s string) (map[string]string, error) {
+	k, v, ok := strings.Cut(s, ":")
+	if !ok {
+		return nil, fmt.Errorf("no : in %q", s)
+	}
+	if w, err := strconv.Unquote(v); err != nil {
+		return nil, fmt.Errorf("unquote %q: %w", v, err)
+	} else {
+		v = w
+	}
+	return map[string]string{strings.Trim(k, "[]"): v}, nil
+}