// ServerDriver handles the authentication and ClientHandlingDriver selection
type ServerDriver interface {
	// Load some general settings around the server setup
	GetSettings() *Settings

	// WelcomeUser is called to send the very first welcome message
	WelcomeUser(cc ClientContext) (string, error)

	// UserLeft is called when the user disconnects, even if he never authenticated
	UserLeft(cc ClientContext)

	// AuthUser authenticates the user and selects an handling driver
	AuthUser(cc ClientContext, user, pass string) (ClientHandlingDriver, error)

	// GetCertificate returns a TLS Certificate to use
	// The certificate could frequently change if we use something like "let's encrypt"
	GetTLSConfig() (*tls.Config, error)
}

// ClientHandlingDriver handles the file system access logic
type ClientHandlingDriver interface {
	// ChangeDirectory changes the current working directory
	ChangeDirectory(cc ClientContext, directory string) error

	// MakeDirectory creates a directory
	MakeDirectory(cc ClientContext, directory string) error

	// ListFiles lists the files of a directory
	ListFiles(cc ClientContext) ([]os.FileInfo, error)

	// OpenFile opens a file in 3 possible modes: read, write, appending write (use appropriate flags)
	OpenFile(cc ClientContext, path string, flag int) (FileStream, error)

	// DeleteFile deletes a file or a directory
	DeleteFile(cc ClientContext, path string) error

	// GetFileInfo gets some info around a file or a directory
	GetFileInfo(cc ClientContext, path string) (os.FileInfo, error)

	// RenameFile renames a file or a directory
	RenameFile(cc ClientContext, from, to string) error

	// CanAllocate gives the approval to allocate some data
	CanAllocate(cc ClientContext, size int) (bool, error)
}

// ClientContext is implemented on the server side to provide some access to few data around the client
type ClientContext interface {
	// Get current path
	Path() string

	// SetDebug activates the debugging of this connection commands
	SetDebug(debug bool)

	// Debug returns the current debugging status of this connection commands
	Debug() bool
	
	// Client's ID on the server
	ID() uint32

	// Client's address
	RemoteAddr() net.Addr
}

// FileStream is a read or write closeable stream
type FileStream interface {
	io.Writer
	io.Reader
	io.Closer
	io.Seeker // <-- Will be used for "REST" command
}

// Settings define all the server settings
type Settings struct {
	ListenHost     string     // Host to receive connections on
	ListenPort     int        // Port to listen on
	PublicHost     string     // Public IP to expose (only an IP address is accepted at this stage)
	MaxConnections int        // Max number of connections to accept
	DataPortRange  *PortRange // Port Range for data connections. Random one will be used if not specified
}