// Copyright © 2014 Steve Francia <spf@spf13.com>.

//

// 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

import (

	"fmt"

	"log"

	"os"

	"path/filepath"

	"strings"

	"sync"

	"time"

	"github.com/spf13/afero/mem"

)

const chmodBits = os.ModePerm | os.ModeSetuid | os.ModeSetgid | os.ModeSticky // Only a subset of bits are allowed to be changed. Documented under os.Chmod()

type MemMapFs struct {

	mu   sync.RWMutex

	data map[string]*mem.FileData

	init sync.Once

}

func NewMemMapFs() Fs {

	return &MemMapFs{}

}

func (m *MemMapFs) getData() map[string]*mem.FileData {

	m.init.Do(func() {

		m.data = make(map[string]*mem.FileData)

		// Root should always exist, right?

		// TODO: what about windows?

		root := mem.CreateDir(FilePathSeparator)

		mem.SetMode(root, os.ModeDir|0755)

		m.data[FilePathSeparator] = root

	})

	return m.data

}

func (*MemMapFs) Name() string { return "MemMapFS" }

func (m *MemMapFs) Create(name string) (File, error) {

	name = normalizePath(name)

	m.mu.Lock()

	file := mem.CreateFile(name)

	m.getData()[name] = file

	m.registerWithParent(file, 0)

	m.mu.Unlock()

	return mem.NewFileHandle(file), nil

}

func (m *MemMapFs) unRegisterWithParent(fileName string) error {

	f, err := m.lockfreeOpen(fileName)

	if err != nil {

		return err

	}

	parent := m.findParent(f)

	if parent == nil {

		log.Panic("parent of ", f.Name(), " is nil")

	}

	parent.Lock()

	mem.RemoveFromMemDir(parent, f)

	parent.Unlock()

	return nil

}

func (m *MemMapFs) findParent(f *mem.FileData) *mem.FileData {

	pdir, _ := filepath.Split(f.Name())

	pdir = filepath.Clean(pdir)

	pfile, err := m.lockfreeOpen(pdir)

	if err != nil {

		return nil

	}

	return pfile

}

func (m *MemMapFs) registerWithParent(f *mem.FileData, perm os.FileMode) {

	if f == nil {

		return

	}

	parent := m.findParent(f)

	if parent == nil {

		pdir := filepath.Dir(filepath.Clean(f.Name()))

		err := m.lockfreeMkdir(pdir, perm)

		if err != nil {

			//log.Println("Mkdir error:", err)

			return

		}

		parent, err = m.lockfreeOpen(pdir)

		if err != nil {

			//log.Println("Open after Mkdir error:", err)

			return

		}

	}

	parent.Lock()

	mem.InitializeDir(parent)

	mem.AddToMemDir(parent, f)

	parent.Unlock()

}

func (m *MemMapFs) lockfreeMkdir(name string, perm os.FileMode) error {

	name = normalizePath(name)

	x, ok := m.getData()[name]

	if ok {

		// Only return ErrFileExists if it's a file, not a directory.

		i := mem.FileInfo{FileData: x}

		if !i.IsDir() {

			return ErrFileExists

		}

	} else {

		item := mem.CreateDir(name)

		mem.SetMode(item, os.ModeDir|perm)

		m.getData()[name] = item

		m.registerWithParent(item, perm)

	}

	return nil

}

func (m *MemMapFs) Mkdir(name string, perm os.FileMode) error {

	perm &= chmodBits

	name = normalizePath(name)

	m.mu.RLock()

	_, ok := m.getData()[name]

	m.mu.RUnlock()

	if ok {

		return &os.PathError{Op: "mkdir", Path: name, Err: ErrFileExists}

	}

	m.mu.Lock()

	item := mem.CreateDir(name)

	mem.SetMode(item, os.ModeDir|perm)

	m.getData()[name] = item

	m.registerWithParent(item, perm)

	m.mu.Unlock()

	return m.setFileMode(name, perm|os.ModeDir)

}

func (m *MemMapFs) MkdirAll(path string, perm os.FileMode) error {

	err := m.Mkdir(path, perm)

	if err != nil {

		if err.(*os.PathError).Err == ErrFileExists {

			return nil

		}

		return err

	}

	return nil

}

// Handle some relative paths

func normalizePath(path string) string {

	path = filepath.Clean(path)

	switch path {

	case ".":

		return FilePathSeparator

	case "..":

		return FilePathSeparator

	default:

		return path

	}

}

func (m *MemMapFs) Open(name string) (File, error) {

	f, err := m.open(name)

	if f != nil {

		return mem.NewReadOnlyFileHandle(f), err

	}

	return nil, err

}

func (m *MemMapFs) openWrite(name string) (File, error) {

	f, err := m.open(name)

	if f != nil {

		return mem.NewFileHandle(f), err

	}

	return nil, err

}

func (m *MemMapFs) open(name string) (*mem.FileData, error) {

	name = normalizePath(name)

	m.mu.RLock()

	f, ok := m.getData()[name]

	m.mu.RUnlock()

	if !ok {

		return nil, &os.PathError{Op: "open", Path: name, Err: ErrFileNotFound}

	}

	return f, nil

}

func (m *MemMapFs) lockfreeOpen(name string) (*mem.FileData, error) {

	name = normalizePath(name)

	f, ok := m.getData()[name]

	if ok {

		return f, nil

	} else {

		return nil, ErrFileNotFound

	}

}

func (m *MemMapFs) OpenFile(name string, flag int, perm os.FileMode) (File, error) {

	perm &= chmodBits

	chmod := false

	file, err := m.openWrite(name)

	if err == nil && (flag&os.O_EXCL > 0) {

		return nil, &os.PathError{Op: "open", Path: name, Err: ErrFileExists}

	}

	if os.IsNotExist(err) && (flag&os.O_CREATE > 0) {

		file, err = m.Create(name)

		chmod = true

	}

	if err != nil {

		return nil, err

	}

	if flag == os.O_RDONLY {

		file = mem.NewReadOnlyFileHandle(file.(*mem.File).Data())

	}

	if flag&os.O_APPEND > 0 {

		_, err = file.Seek(0, os.SEEK_END)

		if err != nil {

			file.Close()

			return nil, err

		}

	}

	if flag&os.O_TRUNC > 0 && flag&(os.O_RDWR|os.O_WRONLY) > 0 {

		err = file.Truncate(0)

		if err != nil {

			file.Close()

			return nil, err

		}

	}

	if chmod {

		return file, m.setFileMode(name, perm)

	}

	return file, nil

}

func (m *MemMapFs) Remove(name string) error {

	name = normalizePath(name)

	m.mu.Lock()

	defer m.mu.Unlock()

	if _, ok := m.getData()[name]; ok {

		err := m.unRegisterWithParent(name)

		if err != nil {

			return &os.PathError{Op: "remove", Path: name, Err: err}

		}

		delete(m.getData(), name)

	} else {

		return &os.PathError{Op: "remove", Path: name, Err: os.ErrNotExist}

	}

	return nil

}

func (m *MemMapFs) RemoveAll(path string) error {

	path = normalizePath(path)

	m.mu.Lock()

	m.unRegisterWithParent(path)

	m.mu.Unlock()

	m.mu.RLock()

	defer m.mu.RUnlock()

	for p := range m.getData() {

			m.mu.RUnlock()

			m.mu.Lock()

			delete(m.getData(), p)

			m.mu.Unlock()

			m.mu.RLock()

		}

	}

	return nil

}

func (m *MemMapFs) Rename(oldname, newname string) error {

	oldname = normalizePath(oldname)

	newname = normalizePath(newname)

	if oldname == newname {

		return nil

	}

	m.mu.RLock()

	defer m.mu.RUnlock()

	if _, ok := m.getData()[oldname]; ok {

		m.mu.RUnlock()

		m.mu.Lock()

		m.unRegisterWithParent(oldname)

		fileData := m.getData()[oldname]

		delete(m.getData(), oldname)

		mem.ChangeFileName(fileData, newname)

		m.getData()[newname] = fileData

		m.registerWithParent(fileData, 0)

		m.mu.Unlock()

		m.mu.RLock()

	} else {

		return &os.PathError{Op: "rename", Path: oldname, Err: ErrFileNotFound}

	}

	return nil

}

func (m *MemMapFs) LstatIfPossible(name string) (os.FileInfo, bool, error) {

	fileInfo, err := m.Stat(name)

	return fileInfo, false, err

}

func (m *MemMapFs) Stat(name string) (os.FileInfo, error) {

	f, err := m.Open(name)

	if err != nil {

		return nil, err

	}

	fi := mem.GetFileInfo(f.(*mem.File).Data())

	return fi, nil

}

func (m *MemMapFs) Chmod(name string, mode os.FileMode) error {

	mode &= chmodBits

	m.mu.RLock()

	f, ok := m.getData()[name]

	m.mu.RUnlock()

	if !ok {

		return &os.PathError{Op: "chmod", Path: name, Err: ErrFileNotFound}

	}

	prevOtherBits := mem.GetFileInfo(f).Mode() & ^chmodBits

	mode = prevOtherBits | mode

	return m.setFileMode(name, mode)

}

func (m *MemMapFs) setFileMode(name string, mode os.FileMode) error {

	name = normalizePath(name)

	m.mu.RLock()

	f, ok := m.getData()[name]

	m.mu.RUnlock()

	if !ok {

		return &os.PathError{Op: "chmod", Path: name, Err: ErrFileNotFound}

	}

	m.mu.Lock()

	mem.SetMode(f, mode)

	m.mu.Unlock()

	return nil

}

func (m *MemMapFs) Chown(name string, uid, gid int) error {

	name = normalizePath(name)

	m.mu.RLock()

	f, ok := m.getData()[name]

	m.mu.RUnlock()

	if !ok {

		return &os.PathError{Op: "chown", Path: name, Err: ErrFileNotFound}

	}

	mem.SetUID(f, uid)

	mem.SetGID(f, gid)

	return nil

}

func (m *MemMapFs) Chtimes(name string, atime time.Time, mtime time.Time) error {

	name = normalizePath(name)

	m.mu.RLock()