added locks for databases; refactoring

jsondb.go

@@ -8,6 +8,7 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
+	"time"
 
 	"git.0x0001f346.de/andreas/utils"
 )
@@ -18,62 +19,81 @@ 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(name string) error {
-	_, databaseAlreadyExists := cluster[name]
+func CreateDatabase(nameOfDatabase string) error {
+	_, databaseAlreadyExists := cluster[nameOfDatabase]
 	if databaseAlreadyExists {
 		return nil
 	}
 
-	err := safeDatabase(name, Database{})
+	err := safeDatabase(nameOfDatabase, Database{})
 	if err != nil {
 		return err
 	}
 
+	unlockDatabase(nameOfDatabase)
+
 	return nil
 }
 
 // DeleteDatabase deletes a database
 func DeleteDatabase(nameOfDatabase string) error {
-	err := os.Remove(getFullPathToDatabase(nameOfDatabase))
+	_, databaseExists := cluster[nameOfDatabase]
+	if !databaseExists {
+		return nil
+	}
+
+	lockDatabase(nameOfDatabase)
+
+	err := deleteDatabase(nameOfDatabase)
 	if err != nil {
 		return err
 	}
 
-	delete(cluster, nameOfDatabase)
-
 	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(name string) (Database, error) {
-	database, err := getDeepCopyOfDatabase(name)
+func GetDatabase(nameOfDatabase string) (Database, error) {
+	database, err := getDeepCopyOfDatabase(nameOfDatabase)
 	if err != nil {
 		return nil, err
 	}
@@ -127,64 +147,89 @@ func LoadCluster() error {
 		}
 
 		cluster[databaseName] = database
+		databaseIsLocked[databaseName] = false
 	}
 
 	return nil
 }
 
 // ReloadDatabase reloads a database from file
-func ReloadDatabase(name string) error {
-	_, databaseExists := cluster[name]
+func ReloadDatabase(nameOfDatabase string) error {
+	_, databaseExists := cluster[nameOfDatabase]
 	if !databaseExists {
 		return errors.New("database does not exist")
 	}
 
-	database, err := loadDatabase(name)
+	database, err := loadDatabase(nameOfDatabase)
 	if err != nil {
 		return err
 	}
 
-	cluster[name] = database
+	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)
+	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
 	}
 
@@ -192,50 +237,67 @@ func RenameKeyInDatabase(nameOfDatabase string, keyOld string, keyNew string) er
 	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(name string, database Database) error {
-	_, databaseExists := cluster[name]
+func SetDatabase(nameOfDatabase string, database Database) error {
+	_, databaseExists := cluster[nameOfDatabase]
 	if !databaseExists {
 		return errors.New("database does not exist")
 	}
 
-	err := safeDatabase(name, database)
+	lockDatabase(nameOfDatabase)
+
+	err := safeDatabase(nameOfDatabase, database)
 	if err != nil {
+		unlockDatabase(nameOfDatabase)
 		return err
 	}
 
-	cluster[name] = database
+	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
 }
@@ -262,6 +324,50 @@ func SetNameOfCluster(name string) error {
 	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,
@@ -269,10 +375,10 @@ func getFullPathToCluster() string {
 	)
 }
 
-func getFullPathToDatabase(name string) string {
+func getFullPathToDatabase(nameOfDatabase string) string {
 	return filepath.Join(
 		getFullPathToCluster(),
-		fmt.Sprintf("%s%s", name, databaseExtension),
+		fmt.Sprintf("%s%s", nameOfDatabase, databaseExtension),
 	)
 }
 
@@ -294,22 +400,9 @@ func isValidName(s string) bool {
 	return !utils.DoesStringContainsNonWhitelistedSubstrings(s, whitelist)
 }
 
-func createCluster() error {
-	if utils.DoesFolderExist(getFullPathToCluster()) {
-		return nil
-	}
-
-	err := utils.CreateFolder(getFullPathToCluster())
-	if err != nil {
-		return err
-	}
-
-	return nil
-}
-
-func loadDatabase(name string) (Database, error) {
+func loadDatabase(nameOfDatabase string) (Database, error) {
 	dbContentAsString, err := utils.LoadStringFromFile(
-		getFullPathToDatabase(name),
+		getFullPathToDatabase(nameOfDatabase),
 	)
 	if err != nil {
 		return Database{}, err
@@ -324,30 +417,43 @@ func loadDatabase(name string) (Database, error) {
 	return database, nil
 }
 
-func safeDatabase(name string, database Database) error {
-	databaseAsJSONBytes, err := json.MarshalIndent(database, "", "\t")
-	if err != nil {
-		return errors.New("could not marshal database: " + name)
+func lockDatabase(nameOfDatabase string) {
+	waitForDatabaseToUnlock(nameOfDatabase)
+
+	databaseIsLocked[nameOfDatabase] = true
 }
 
-	err = utils.WriteStringToFile(getFullPathToDatabase(name), string(databaseAsJSONBytes))
+func safeDatabase(nameOfDatabase string, database Database) error {
+	databaseAsJSONBytes, err := json.MarshalIndent(database, "", "\t")
 	if err != nil {
-		return errors.New("could not write to file: " + getFullPathToDatabase(name))
+		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 getDeepCopyOfDatabase(name string) (Database, error) {
-	originalDatabase, databaseExists := cluster[name]
+func unlockDatabase(nameOfDatabase string) {
+	databaseIsLocked[nameOfDatabase] = false
+}
+
+func waitForDatabaseToUnlock(nameOfDatabase string) {
+	isLocked, databaseExists := databaseIsLocked[nameOfDatabase]
 	if !databaseExists {
-		return nil, errors.New("database does not exist")
+		return
 	}
 
-	copyOfDatabase := make(Database)
-	for key, value := range originalDatabase {
-		copyOfDatabase[key] = value
+	for {
+		if !isLocked {
+			break
 		}
 
-	return copyOfDatabase, nil
+		time.Sleep(5 * time.Millisecond)
+
+		isLocked = databaseIsLocked[nameOfDatabase]
+	}
 }