http-boot-server/bootserver/services/services.go

package services

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"time"

	"git.faercol.me/faercol/http-boot-server/bootserver/bootoption"
	"git.faercol.me/faercol/http-boot-server/bootserver/filelock"
	"github.com/google/uuid"
	"github.com/sirupsen/logrus"
)

var ErrUnknownClient = errors.New("unknown client")
var ErrUnselectedBootOption = errors.New("unselected boot option")
var ErrUnknownBootOption = errors.New("unknown boot option")

const defaultLockTimeout = 1 * time.Second

type ClientHandlerService struct {
	filepath    string
	fileLock    *filelock.FileLock
	lockTimeout time.Duration
	logger      *logrus.Logger
}

func NewClientHandlerService(filepath string, logger *logrus.Logger) *ClientHandlerService {
	return &ClientHandlerService{
		filepath:    filepath,
		fileLock:    filelock.New(filepath),
		lockTimeout: defaultLockTimeout,
		logger:      logger,
	}
}

func (chs *ClientHandlerService) init() {
	if _, err := os.Open(chs.filepath); errors.Is(err, os.ErrNotExist) {
		if err := os.WriteFile(chs.filepath, nil, 0o644); err != nil {
			panic(fmt.Errorf("failed to init data file: %w", err))
		}
	}
}

func (chs *ClientHandlerService) unload(conf map[uuid.UUID]*bootoption.Client) error {
	dat, err := json.Marshal(conf)
	if err != nil {
		return fmt.Errorf("failed to marshal data to JSON: %w", err)
	}

	if err := os.WriteFile(chs.filepath, dat, 0o644); err != nil {
		return fmt.Errorf("failed to commit to the data file: %w", err)
	}
	if err := chs.fileLock.Unlock(); err != nil {
		return fmt.Errorf("failed to release the lock to data file: %w", err)
	}
	return nil
}

func (chs *ClientHandlerService) load() (map[uuid.UUID]*bootoption.Client, error) {
	conf := make(map[uuid.UUID]*bootoption.Client)

	if err := chs.fileLock.Lock(chs.lockTimeout); err != nil {
		return nil, fmt.Errorf("failed to obtain a lock to the data file: %w", err)
	}

	dat, err := os.ReadFile(chs.filepath)
	if err != nil {
		return nil, fmt.Errorf("failed to read data file: %w", err)
	}
	if err := json.Unmarshal(dat, &conf); err != nil {
		return nil, fmt.Errorf("failed to parse data file: %w", err)
	}
	return conf, nil
}

func (chs *ClientHandlerService) unloadNoCommmit(conf map[uuid.UUID]*bootoption.Client) {
	if err := chs.unload(conf); err != nil {
		chs.logger.Errorf("Failed to unload config: %q", err.Error())
	}
}

func (chs *ClientHandlerService) AddClient(client *bootoption.Client) (uuid.UUID, error) {
	clients, err := chs.load()
	if err != nil {
		return uuid.Nil, fmt.Errorf("failed to load current config: %w", err)
	}

	client.ID = uuid.New()
	clients[client.ID] = client

	if err := chs.unload(clients); err != nil {
		return uuid.Nil, fmt.Errorf("failed to save current config: %w", err)
	}
	return client.ID, nil
}

func (chs *ClientHandlerService) GetClientSelectedBootOption(client uuid.UUID) (*bootoption.EFIApp, error) {
	clients, err := chs.load()
	if err != nil {
		return nil, fmt.Errorf("failed to load current config: %w", err)
	}
	defer chs.unloadNoCommmit(clients)

	clientDetails, ok := clients[client]
	if !ok {
		return nil, ErrUnknownClient
	}

	if clientDetails.SelectedOption == "" {
		return nil, ErrUnselectedBootOption
	}

	if option, ok := clientDetails.Options[clientDetails.SelectedOption]; !ok {
		return nil, ErrUnknownBootOption
	} else {
		return &option, nil
	}
}

func (chs *ClientHandlerService) SetClientBootOption(client uuid.UUID, option string) error {
	var err error

	clients, err := chs.load()
	if err != nil {
		return fmt.Errorf("failed to load current config: %w", err)
	}

	clientDetails, ok := clients[client]
	if !ok {
		err = ErrUnknownClient
	} else {
		if _, ok := clientDetails.Options[option]; !ok {
			err = ErrUnknownBootOption
		} else {
			clientDetails.SelectedOption = option
		}
	}

	if err != nil {
		defer chs.unloadNoCommmit(clients)
		return err
	}

	if err := chs.unload(clients); err != nil {
		return fmt.Errorf("failed to save current config: %w", err)
	}
	return nil
}