// Copyright © 2015 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 mem

import (

	"bytes"

	"errors"

	"io"

	"os"

	"path/filepath"

	"sync"

	"sync/atomic"

)

const FilePathSeparator = string(filepath.Separator)

type File struct {

	// atomic requires 64-bit alignment for struct field access

	at           int64

	readDirCount int64

	closed       bool

	readOnly     bool

	fileData     *FileData

}

func NewFileHandle(data *FileData) *File {

	return &File{fileData: data}

}

func NewReadOnlyFileHandle(data *FileData) *File {

	return &File{fileData: data, readOnly: true}

}

func (f File) Data() *FileData {

	return f.fileData

}

type FileData struct {

	sync.Mutex

	name    string

	data    []byte

	memDir  Dir

	dir     bool

	mode    os.FileMode

	modtime time.Time

}

func (d *FileData) Name() string {

	d.Lock()

	defer d.Unlock()

	return d.name

}

func CreateFile(name string) *FileData {

	return &FileData{name: name, mode: os.ModeTemporary, modtime: time.Now()}

}

func CreateDir(name string) *FileData {

	return &FileData{name: name, memDir: &DirMap{}, dir: true}

}

func ChangeFileName(f *FileData, newname string) {

	f.Lock()

	f.name = newname

	f.Unlock()

}

func SetMode(f *FileData, mode os.FileMode) {

	f.Lock()

	f.mode = mode

	f.Unlock()

}

func SetModTime(f *FileData, mtime time.Time) {

	f.Lock()

	setModTime(f, mtime)

	f.Unlock()

}

func setModTime(f *FileData, mtime time.Time) {

	f.modtime = mtime

}

func GetFileInfo(f *FileData) *FileInfo {

	return &FileInfo{f}

}

func (f *File) Open() error {

	atomic.StoreInt64(&f.at, 0)

	atomic.StoreInt64(&f.readDirCount, 0)

	f.fileData.Lock()

	f.closed = false

	f.fileData.Unlock()

	return nil

}

func (f *File) Close() error {

	f.fileData.Lock()

	f.closed = true

	if !f.readOnly {

		setModTime(f.fileData, time.Now())

	}

	f.fileData.Unlock()

	return nil

}

func (f *File) Name() string {

	return f.fileData.Name()

}

func (f *File) Stat() (os.FileInfo, error) {

	return &FileInfo{f.fileData}, nil

}

func (f *File) Sync() error {

	return nil

}

func (f *File) Readdir(count int) (res []os.FileInfo, err error) {

	if !f.fileData.dir {

		return nil, &os.PathError{Op: "readdir", Path: f.fileData.name, Err: errors.New("not a dir")}

	}

	var outLength int64

	f.fileData.Lock()

	files := f.fileData.memDir.Files()[f.readDirCount:]

	if count > 0 {

		if len(files) < count {

			outLength = int64(len(files))

		} else {

			outLength = int64(count)

		}

		if len(files) == 0 {

			err = io.EOF

		}

	} else {

		outLength = int64(len(files))

	}

	f.readDirCount += outLength

	f.fileData.Unlock()

	res = make([]os.FileInfo, outLength)

	for i := range res {

		res[i] = &FileInfo{files[i]}

	}

	return res, err

}

func (f *File) Readdirnames(n int) (names []string, err error) {

	fi, err := f.Readdir(n)

	names = make([]string, len(fi))

	for i, f := range fi {

		_, names[i] = filepath.Split(f.Name())

	}

	return names, err

}

func (f *File) Read(b []byte) (n int, err error) {

	f.fileData.Lock()

	defer f.fileData.Unlock()

	if f.closed == true {

		return 0, ErrFileClosed

	}

	if len(b) > 0 && int(f.at) == len(f.fileData.data) {

		return 0, io.EOF

	}

	if int(f.at) > len(f.fileData.data) {

		return 0, io.ErrUnexpectedEOF

	}

	if len(f.fileData.data)-int(f.at) >= len(b) {

		n = len(b)

	} else {

		n = len(f.fileData.data) - int(f.at)

	}

	copy(b, f.fileData.data[f.at:f.at+int64(n)])

	atomic.AddInt64(&f.at, int64(n))

	return

}

func (f *File) ReadAt(b []byte, off int64) (n int, err error) {

	atomic.StoreInt64(&f.at, off)

}

func (f *File) Truncate(size int64) error {

	if f.closed == true {

		return ErrFileClosed

	}

	if f.readOnly {

		return &os.PathError{Op: "truncate", Path: f.fileData.name, Err: errors.New("file handle is read only")}

	}

	if size < 0 {

		return ErrOutOfRange

	}

	if size > int64(len(f.fileData.data)) {

		diff := size - int64(len(f.fileData.data))

		f.fileData.data = append(f.fileData.data, bytes.Repeat([]byte{00}, int(diff))...)

	} else {

		f.fileData.data = f.fileData.data[0:size]

	}

	setModTime(f.fileData, time.Now())

	return nil

}

func (f *File) Seek(offset int64, whence int) (int64, error) {

	if f.closed == true {

		return 0, ErrFileClosed

	}

	switch whence {

		atomic.StoreInt64(&f.at, offset)

		atomic.StoreInt64(&f.at, int64(len(f.fileData.data))+offset)

	}

	return f.at, nil

}

func (f *File) Write(b []byte) (n int, err error) {

	if f.readOnly {

		return 0, &os.PathError{Op: "write", Path: f.fileData.name, Err: errors.New("file handle is read only")}

	}

	n = len(b)

	cur := atomic.LoadInt64(&f.at)

	f.fileData.Lock()

	defer f.fileData.Unlock()

	diff := cur - int64(len(f.fileData.data))

	var tail []byte

	if n+int(cur) < len(f.fileData.data) {

		tail = f.fileData.data[n+int(cur):]

	}

	if diff > 0 {

		f.fileData.data = append(f.fileData.data, tail...)

	} else {

		f.fileData.data = append(f.fileData.data[:cur], b...)

		f.fileData.data = append(f.fileData.data, tail...)

	}

	setModTime(f.fileData, time.Now())

	return

}

func (f *File) WriteAt(b []byte, off int64) (n int, err error) {

	atomic.StoreInt64(&f.at, off)

	return f.Write(b)

}

func (f *File) WriteString(s string) (ret int, err error) {

	return f.Write([]byte(s))

}

func (f *File) Info() *FileInfo {

	return &FileInfo{f.fileData}

}

type FileInfo struct {

	*FileData

}

// Implements os.FileInfo

func (s *FileInfo) Name() string {

	s.Lock()

	_, name := filepath.Split(s.name)

	s.Unlock()

	return name

}

func (s *FileInfo) Mode() os.FileMode {

	s.Lock()

	defer s.Unlock()

	return s.mode

}

func (s *FileInfo) ModTime() time.Time {

	s.Lock()

	defer s.Unlock()

	return s.modtime

}

func (s *FileInfo) IsDir() bool {

	s.Lock()

	defer s.Unlock()

	return s.dir

}

func (s *FileInfo) Sys() interface{} { return nil }

func (s *FileInfo) Size() int64 {

	if s.IsDir() {

		return int64(42)

	}

	s.Lock()

	defer s.Unlock()

	return int64(len(s.data))

}

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

)