package common

import (
	"io"
	"os"
	"strings"
)

const BACKEND_NIL = "_nothing_"

var Backend = NewDriver()

func NewDriver() Driver {
	return Driver{make(map[string]IBackend)}
}

type Driver struct {
	ds map[string]IBackend
}

func (d *Driver) Register(name string, driver IBackend) {
	if driver == nil {
		panic("backend: register invalid nil backend")
	}
	if d.ds[name] != nil {
		panic("backend: register already exist")
	}
	d.ds[name] = driver
}

func (d *Driver) Get(name string) IBackend {
	b := d.ds[name]
	if b == nil || name == BACKEND_NIL {
		return Nothing{}
	}
	return b
}

type Nothing struct {}

func (b Nothing) Init(params map[string]string, app *App) (IBackend, error) {
	return &Nothing{}, nil
}
func (b Nothing) Info() string {
	return "N/A"
}
func (b Nothing) Ls(path string) ([]os.FileInfo, error) {
	return nil, NewError("", 401)
}
func (b Nothing) Cat(path string) (io.Reader, error) {
	return strings.NewReader(""), NewError("", 401)
}
func (b Nothing) Mkdir(path string) error {
	return NewError("", 401)
}
func (b Nothing) Rm(path string) error {
	return NewError("", 401)
}
func (b Nothing) Mv(from string, to string) error {
	return NewError("", 401)
}
func (b Nothing) Touch(path string) error {
	return NewError("", 401)
}
func (b Nothing) Save(path string, file io.Reader) error {
	return NewError("", 401)
}