package filepb

import (
	"errors"
	"fmt"
	"os"
	"strings"

	"google.golang.org/protobuf/encoding/protojson"
	"google.golang.org/protobuf/encoding/prototext"
	"google.golang.org/protobuf/proto"
)

var ErrEmpty error = fmt.Errorf("config file was empty")
var ErrMarshal error = fmt.Errorf("protobuf parse error")

// print the protobuf in human form
func IdentifyPB(filename string) (string, string, error) {
	data, err := os.ReadFile(filename)
	if err != nil {
		// log.Info("open config file :", err)
		return "", "", err
	}

	var pb *FakeFile
	pb = new(FakeFile)
	if err := pb.Unmarshal(data); err != nil {
		return "", "", err
	}
	// log.Info("Identify protobuf file uuid =", pb.Uuid, "version =", pb.Version)
	return pb.Uuid, pb.Version, nil
}

func (pb *FakeFile) loadFromFilename(fullname string) error {
	if strings.HasSuffix(fullname, ".text") {
		return loadTEXT(pb, fullname)
	}
	if strings.HasSuffix(fullname, ".json") {
		return loadJSON(pb, fullname)
	}
	if strings.HasSuffix(fullname, ".pb") {
		return loadPB(pb, fullname)
	}

	return fmt.Errorf("unknown filetype '%s'", fullname)
}

func loadPB(pb proto.Message, fullname string) error {
	data, err := loadFile(fullname)
	if err != nil {
		// set pb.Filename that was attempted
		return err
	}

	if err = proto.Unmarshal(data, pb); err != nil {
		return err
	}

	return nil
}

func loadTEXT(pb proto.Message, fullname string) error {
	var data []byte
	var err error
	if data, err = loadFile(fullname); err != nil {
		return err
	}

	// don't even bother with Marshal()
	if data == nil {
		return ErrEmpty // file is empty
	}

	// Unmarshal()
	if err = prototext.Unmarshal(data, pb); err != nil {
		return ErrMarshal
	}
	return nil
}

// json files are backup Marshal() data in case .text Unmarshal() fails
// they always should have the ".text" filename in them
func loadJSON(pb proto.Message, fullname string) error {
	var data []byte
	var err error
	if data, err = loadFile(fullname); err != nil {
		return err
	}

	// don't even bother with Marshal()
	if data == nil {
		return ErrEmpty // file is empty
	}

	// Unmarshal()
	if err = protojson.Unmarshal(data, pb); err != nil {
		return ErrMarshal
	}
	return nil
}

func loadFile(fullname string) ([]byte, error) {
	data, err := os.ReadFile(fullname)
	if errors.Is(err, os.ErrNotExist) {
		// if file does not exist, just return nil. this
		return nil, err
	}
	if err != nil {
		return nil, err
	}
	if len(data) == 0 {
		return data, ErrEmpty
	}
	return data, nil
}