// Command protoc-gen-gitaly-lint is designed to be used as a protobuf compiler
// plugin to verify Gitaly processes are being followed when writing RPC's.
//
// # Usage
//
// The protoc-gen-gitaly linter can be chained into any protoc workflow that
// requires verification that Gitaly RPC guidelines are followed. Typically
// this can be done by adding the following argument to an existing protoc
// command:
//
//	--gitaly_lint_out=.
//
// For example, you may add the linter as an argument to the command responsible
// for generating Go code:
//
//	protoc --go_out=. --gitaly_lint_out=. *.proto
//
// Or, you can run the Gitaly linter by itself. To try out, run the following
// command while in the project root:
//
//	protoc --gitaly_lint_out=. ./go/internal/cmd/protoc-gen-gitaly-lint/testdata/incomplete.proto
//
// You should see some errors printed to screen for improperly written
// RPC's in the incomplete.proto file.
//
// # Prerequisites
//
// The protobuf compiler (protoc) can be obtained from the GitHub page:
// https://github.com/protocolbuffers/protobuf/releases
//
// # Background
//
// The protobuf compiler accepts plugins to analyze protobuf files and generate
// language specific code.
//
// These plugins require the following executable naming convention:
//
//	protoc-gen-$NAME
//
// Where $NAME is the plugin name of the compiler desired. The protobuf compiler
// will search the PATH until an executable with that name is found for a
// desired plugin. For example, the following protoc command:
//
//	protoc --gitaly_lint_out=. *.proto
//
// # The above will search the PATH for an executable named protoc-gen-gitaly-lint
//
// The plugin accepts a protobuf message in STDIN that describes the parsed
// protobuf files. A response is sent back on STDOUT that contains any errors.
package main

import (
	"fmt"
	"io"
	"log"
	"os"
	"strings"

	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/types/pluginpb"
)

func main() {
	data, err := io.ReadAll(os.Stdin)
	if err != nil {
		log.Fatalf("reading input: %s", err)
	}

	req := &pluginpb.CodeGeneratorRequest{}

	if err := proto.Unmarshal(data, req); err != nil {
		log.Fatalf("parsing input proto: %s", err)
	}

	if err := lintProtos(req); err != nil {
		log.Fatal(err)
	}
}

func lintProtos(req *pluginpb.CodeGeneratorRequest) error {
	var errMsgs []string
	for _, pf := range req.GetProtoFile() {
		errs := LintFile(pf, req)
		for _, err := range errs {
			errMsgs = append(errMsgs, err.Error())
		}
	}

	resp := &pluginpb.CodeGeneratorResponse{}

	if len(errMsgs) > 0 {
		errMsg := strings.Join(errMsgs, "\n\t")
		resp.Error = &errMsg
	}

	// Send back the results.
	data, err := proto.Marshal(resp)
	if err != nil {
		return fmt.Errorf("failed to marshal output proto: %w", err)
	}

	_, err = os.Stdout.Write(data)
	if err != nil {
		return fmt.Errorf("failed to write output proto: %w", err)
	}
	return nil
}
