jsondb/jsondb.go

package jsondb

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path"
	"path/filepath"
	"strings"
	"time"

	"git.0x0001f346.de/andreas/utils"
)

type Cluster map[string]Database
type Database map[string]interface{}

var cluster Cluster = Cluster{}
var locationOfCluster string = utils.GetPathToParrentFolderOfThisExecutable()
var nameOfCluster string = "jsondb"
var databaseIsLocked map[string]bool = map[string]bool{}

const databaseExtension string = ".json"

// CreateDatabase creates a database or returns nil if it already exists
func CreateDatabase(nameOfDatabase string) error {
	_, databaseAlreadyExists := cluster[nameOfDatabase]
	if databaseAlreadyExists {
		return nil
	}

	err := safeDatabase(nameOfDatabase, Database{})
	if err != nil {
		return err
	}

	unlockDatabase(nameOfDatabase)

	return nil
}

// DeleteDatabase deletes a database
func DeleteDatabase(nameOfDatabase string) error {
	_, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return nil
	}

	lockDatabase(nameOfDatabase)

	err := deleteDatabase(nameOfDatabase)
	if err != nil {
		return err
	}

	return nil
}

// DeleteKeyFromDatabase deletes a key in a database and write it to file
func DeleteKeyFromDatabase(nameOfDatabase string, key string) error {
	_, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return errors.New("database does not exist")
	}

	lockDatabase(nameOfDatabase)

	err := ReloadDatabase(nameOfDatabase)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	database, err := getDeepCopyOfDatabase(nameOfDatabase)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	delete(database, key)
	err = safeDatabase(nameOfDatabase, database)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	cluster[nameOfDatabase] = database
	unlockDatabase(nameOfDatabase)

	return nil
}

// GetDatabase returns a database if it exists
func GetDatabase(nameOfDatabase string) (Database, error) {
	database, err := getDeepCopyOfDatabase(nameOfDatabase)
	if err != nil {
		return nil, err
	}

	return database, nil
}

// GetKeyFromDatabase returns a key from a database if both exist
func GetKeyFromDatabase(nameOfDatabase string, key string) (interface{}, error) {
	database, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return nil, errors.New("database does not exist")
	}

	value, keyExists := database[key]
	if !keyExists {
		return nil, errors.New("key does not exist")
	}

	return value, nil
}

// GetLocationOfCluster returns locationOfCluster
func GetLocationOfCluster() string {
	return locationOfCluster
}

// GetNameOfCluster returns nameOfCluster
func GetNameOfCluster() string {
	return nameOfCluster
}

// LoadCluster loads all databases from the current cluster
func LoadCluster() error {
	if !utils.DoesFolderExist(getFullPathToCluster()) {
		err := createCluster()
		if err != nil {
			return err
		}
	}

	for _, p := range utils.GetAllFilesInFolderByExtension(getFullPathToCluster(), databaseExtension) {
		databaseName := strings.TrimSuffix(path.Base(p), filepath.Ext(path.Base(p)))
		if !isValidName(databaseName) {
			continue
		}

		database, err := loadDatabase(databaseName)
		if err != nil {
			return err
		}

		cluster[databaseName] = database
		databaseIsLocked[databaseName] = false
	}

	return nil
}

// ReloadDatabase reloads a database from file
func ReloadDatabase(nameOfDatabase string) error {
	_, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return errors.New("database does not exist")
	}

	database, err := loadDatabase(nameOfDatabase)
	if err != nil {
		return err
	}

	cluster[nameOfDatabase] = database

	return nil
}

// RenameDatabase renames a database
func RenameDatabase(nameOfDatabase string, newNameOfDatabase string) error {
	_, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return errors.New("database does not exist")
	}

	lockDatabase(nameOfDatabase)

	err := ReloadDatabase(nameOfDatabase)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	database, err := getDeepCopyOfDatabase(nameOfDatabase)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	err = safeDatabase(newNameOfDatabase, database)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	cluster[newNameOfDatabase] = database
	lockDatabase(newNameOfDatabase)

	err = deleteDatabase(nameOfDatabase)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		unlockDatabase(newNameOfDatabase)
		return err
	}

	unlockDatabase(newNameOfDatabase)

	return nil
}

// RenameKeyInDatabase renames a key in a database and write it to file
func RenameKeyInDatabase(nameOfDatabase string, keyOld string, keyNew string) error {
	_, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return errors.New("database does not exist")
	}

	lockDatabase(nameOfDatabase)

	err := ReloadDatabase(nameOfDatabase)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	database, err := getDeepCopyOfDatabase(nameOfDatabase)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	database[keyNew] = database[keyOld]
	delete(database, keyOld)
	err = safeDatabase(nameOfDatabase, database)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	cluster[nameOfDatabase] = database
	unlockDatabase(nameOfDatabase)

	return nil
}

// SetDatabase sets a database and writes it to file
func SetDatabase(nameOfDatabase string, database Database) error {
	_, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return errors.New("database does not exist")
	}

	lockDatabase(nameOfDatabase)

	err := safeDatabase(nameOfDatabase, database)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	cluster[nameOfDatabase] = database
	unlockDatabase(nameOfDatabase)

	return nil
}

// SetKeyInDatabase sets a key from in a database and write it to file
func SetKeyInDatabase(nameOfDatabase string, key string, value interface{}) error {
	_, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return errors.New("database does not exist")
	}

	lockDatabase(nameOfDatabase)

	err := ReloadDatabase(nameOfDatabase)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	database, err := getDeepCopyOfDatabase(nameOfDatabase)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	database[key] = value
	err = safeDatabase(nameOfDatabase, database)
	if err != nil {
		unlockDatabase(nameOfDatabase)
		return err
	}

	cluster[nameOfDatabase] = database
	unlockDatabase(nameOfDatabase)

	return nil
}

// SetLocationOfCluster sets locationOfCluster if p is a valid folder
func SetLocationOfCluster(location string) error {
	if !utils.DoesFolderExist(location) {
		return errors.New("not a valid cluster location")
	}

	locationOfCluster = location

	return nil
}

// SetNameOfCluster sets nameOfCluster if s is a valid cluster name
func SetNameOfCluster(name string) error {
	if !isValidName(name) {
		return errors.New("not a valid cluster name")
	}

	nameOfCluster = name

	return nil
}

func createCluster() error {
	if utils.DoesFolderExist(getFullPathToCluster()) {
		return nil
	}

	err := utils.CreateFolder(getFullPathToCluster())
	if err != nil {
		return err
	}

	return nil
}

func deleteDatabase(nameOfDatabase string) error {
	_, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return nil
	}

	err := os.Remove(getFullPathToDatabase(nameOfDatabase))
	if err != nil {
		return err
	}

	delete(cluster, nameOfDatabase)
	delete(databaseIsLocked, nameOfDatabase)

	return nil
}

func getDeepCopyOfDatabase(nameOfDatabase string) (Database, error) {
	originalDatabase, databaseExists := cluster[nameOfDatabase]
	if !databaseExists {
		return nil, errors.New("database does not exist")
	}

	copyOfDatabase := make(Database)
	for key, value := range originalDatabase {
		copyOfDatabase[key] = value
	}

	return copyOfDatabase, nil
}

func getFullPathToCluster() string {
	return filepath.Join(
		locationOfCluster,
		nameOfCluster,
	)
}

func getFullPathToDatabase(nameOfDatabase string) string {
	return filepath.Join(
		getFullPathToCluster(),
		fmt.Sprintf("%s%s", nameOfDatabase, databaseExtension),
	)
}

func isValidName(s string) bool {
	if len(s) == 0 {
		return false
	}

	whitelist := utils.BuildWhitelistForStringSanitisation(
		[]string{
			"0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
			"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
			"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z",
			"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",
			"n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",
		},
	)

	return !utils.DoesStringContainsNonWhitelistedSubstrings(s, whitelist)
}

func loadDatabase(nameOfDatabase string) (Database, error) {
	dbContentAsString, err := utils.LoadStringFromFile(
		getFullPathToDatabase(nameOfDatabase),
	)
	if err != nil {
		return Database{}, err
	}

	var database Database
	err = json.Unmarshal([]byte(dbContentAsString), &database)
	if err != nil {
		return Database{}, err
	}

	return database, nil
}

func lockDatabase(nameOfDatabase string) {
	waitForDatabaseToUnlock(nameOfDatabase)

	databaseIsLocked[nameOfDatabase] = true
}

func safeDatabase(nameOfDatabase string, database Database) error {
	databaseAsJSONBytes, err := json.MarshalIndent(database, "", "\t")
	if err != nil {
		return errors.New("could not marshal database: " + nameOfDatabase)
	}

	err = utils.WriteStringToFile(getFullPathToDatabase(nameOfDatabase), string(databaseAsJSONBytes))
	if err != nil {
		return errors.New("could not write to file: " + getFullPathToDatabase(nameOfDatabase))
	}

	return nil
}

func unlockDatabase(nameOfDatabase string) {
	databaseIsLocked[nameOfDatabase] = false
}

func waitForDatabaseToUnlock(nameOfDatabase string) {
	isLocked, databaseExists := databaseIsLocked[nameOfDatabase]
	if !databaseExists {
		return
	}

	for {
		if !isLocked {
			break
		}

		time.Sleep(5 * time.Millisecond)

		isLocked = databaseIsLocked[nameOfDatabase]
	}
}