// Copyright © 2014 Steve Francia <spf@spf13.com>.
// Copyright 2013 tsuru authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package afero provides types and methods for interacting with the filesystem,
// as an abstraction layer.

// Afero also provides a few implementations that are mostly interoperable. One that
// uses the operating system filesystem, one that uses memory to store files
// (cross platform) and an interface that should be implemented if you want to
// provide your own filesystem.

package afero

import (
	"errors"
	"io"
	"os"
	"sort"
)

// File represents a file in the filesystem.
type File interface {
	io.Closer
	io.Reader
	io.ReaderAt
	io.Seeker
	io.Writer
	io.WriterAt
	//Fd() uintptr
	Stat() (os.FileInfo, error)
	Readdir(count int) ([]os.FileInfo, error)
	Readdirnames(n int) ([]string, error)
	WriteString(s string) (ret int, err error)
	Truncate(size int64) error
	Name() string
}

// Fs is the filesystem interface.
//
// Any simulated or real filesystem should implement this interface.
type Fs interface {
	// Create creates a file in the filesystem, returning the file and an
	// error, if any happens.
	Create(name string) (File, error)

	// Mkdir creates a directory in the filesystem, return an error if any
	// happens.
	Mkdir(name string, perm os.FileMode) error

	// MkdirAll creates a directory path and all parents that does not exist
	// yet.
	MkdirAll(path string, perm os.FileMode) error

	// Open opens a file, returning it or an error, if any happens.
	Open(name string) (File, error)

	// OpenFile opens a file using the given flags and the given mode.
	OpenFile(name string, flag int, perm os.FileMode) (File, error)

	// Remove removes a file identified by name, returning an error, if any
	// happens.
	Remove(name string) error

	// RemoveAll removes a directory path and all any children it contains. It
	// does not fail if the path does not exist (return nil).
	RemoveAll(path string) error

	// Rename renames a file.
	Rename(oldname, newname string) error

	// Stat returns a FileInfo describing the named file, or an error, if any
	// happens.
	Stat(name string) (os.FileInfo, error)

	// The name of this FileSystem
	Name() string
}

var (
	ErrFileClosed        = errors.New("File is closed")
	ErrOutOfRange        = errors.New("Out of range")
	ErrTooLarge          = errors.New("Too large")
	ErrFileNotFound      = os.ErrNotExist
	ErrFileExists        = os.ErrExist
	ErrDestinationExists = os.ErrExist
)

// ReadDir reads the directory named by dirname and returns
// a list of sorted directory entries.
func ReadDir(dirname string, fs Fs) ([]os.FileInfo, error) {
	f, err := fs.Open(dirname)
	if err != nil {
		return nil, err
	}
	list, err := f.Readdir(-1)
	f.Close()
	if err != nil {
		return nil, err
	}
	sort.Sort(byName(list))
	return list, nil
}

// byName implements sort.Interface.
type byName []os.FileInfo

func (f byName) Len() int           { return len(f) }
func (f byName) Less(i, j int) bool { return f[i].Name() < f[j].Name() }
func (f byName) Swap(i, j int)      { f[i], f[j] = f[j], f[i] }