// Package crypt provides wrappers for Fs and Object which implement encryption
package crypt

import (
	"fmt"
	"io"
	"path"
	"strings"
	"time"

	"github.com/ncw/rclone/fs"
	"github.com/ncw/rclone/fs/accounting"
	"github.com/ncw/rclone/fs/config/configmap"
	"github.com/ncw/rclone/fs/config/configstruct"
	"github.com/ncw/rclone/fs/config/obscure"
	"github.com/ncw/rclone/fs/hash"
	"github.com/pkg/errors"
)

// Globals
// Register with Fs
func init() {
	fs.Register(&fs.RegInfo{
		Name:        "crypt",
		Description: "Encrypt/Decrypt a remote",
		NewFs:       NewFs,
		Options: []fs.Option{{
			Name:     "remote",
			Help:     "Remote to encrypt/decrypt.\nNormally should contain a ':' and a path, eg \"myremote:path/to/dir\",\n\"myremote:bucket\" or maybe \"myremote:\" (not recommended).",
			Required: true,
		}, {
			Name:    "filename_encryption",
			Help:    "How to encrypt the filenames.",
			Default: "standard",
			Examples: []fs.OptionExample{
				{
					Value: "off",
					Help:  "Don't encrypt the file names.  Adds a \".bin\" extension only.",
				}, {
					Value: "standard",
					Help:  "Encrypt the filenames see the docs for the details.",
				}, {
					Value: "obfuscate",
					Help:  "Very simple filename obfuscation.",
				},
			},
		}, {
			Name:    "directory_name_encryption",
			Help:    "Option to either encrypt directory names or leave them intact.",
			Default: true,
			Examples: []fs.OptionExample{
				{
					Value: "true",
					Help:  "Encrypt directory names.",
				},
				{
					Value: "false",
					Help:  "Don't encrypt directory names, leave them intact.",
				},
			},
		}, {
			Name:       "password",
			Help:       "Password or pass phrase for encryption.",
			IsPassword: true,
		}, {
			Name:       "password2",
			Help:       "Password or pass phrase for salt. Optional but recommended.\nShould be different to the previous password.",
			IsPassword: true,
		}, {
			Name:     "show_mapping",
			Help:     "For all files listed show how the names encrypt.",
			Default:  false,
			Hide:     fs.OptionHideConfigurator,
			Advanced: true,
		}},
	})
}

// newCipherForConfig constructs a Cipher for the given config name
func newCipherForConfig(opt *Options) (Cipher, error) {
	mode, err := NewNameEncryptionMode(opt.FilenameEncryption)
	if err != nil {
		return nil, err
	}
	if opt.Password == "" {
		return nil, errors.New("password not set in config file")
	}
	password, err := obscure.Reveal(opt.Password)
	if err != nil {
		return nil, errors.Wrap(err, "failed to decrypt password")
	}
	var salt string
	if opt.Password2 != "" {
		salt, err = obscure.Reveal(opt.Password2)
		if err != nil {
			return nil, errors.Wrap(err, "failed to decrypt password2")
		}
	}
	cipher, err := newCipher(mode, password, salt, opt.DirectoryNameEncryption)
	if err != nil {
		return nil, errors.Wrap(err, "failed to make cipher")
	}
	return cipher, nil
}

// NewCipher constructs a Cipher for the given config
func NewCipher(m configmap.Mapper) (Cipher, error) {
	// Parse config into Options struct
	opt := new(Options)
	err := configstruct.Set(m, opt)
	if err != nil {
		return nil, err
	}
	return newCipherForConfig(opt)
}

// NewFs contstructs an Fs from the path, container:path
func NewFs(name, rpath string, m configmap.Mapper) (fs.Fs, error) {
	// Parse config into Options struct
	opt := new(Options)
	err := configstruct.Set(m, opt)
	if err != nil {
		return nil, err
	}
	cipher, err := newCipherForConfig(opt)
	if err != nil {
		return nil, err
	}
	remote := opt.Remote
	if strings.HasPrefix(remote, name+":") {
		return nil, errors.New("can't point crypt remote at itself - check the value of the remote setting")
	}
	// Look for a file first
	remotePath := path.Join(remote, cipher.EncryptFileName(rpath))
	wrappedFs, err := fs.NewFs(remotePath)
	// if that didn't produce a file, look for a directory
	if err != fs.ErrorIsFile {
		remotePath = path.Join(remote, cipher.EncryptDirName(rpath))
		wrappedFs, err = fs.NewFs(remotePath)
	}
	if err != fs.ErrorIsFile && err != nil {
		return nil, errors.Wrapf(err, "failed to make remote %q to wrap", remotePath)
	}
	f := &Fs{
		Fs:     wrappedFs,
		name:   name,
		root:   rpath,
		opt:    *opt,
		cipher: cipher,
	}
	// the features here are ones we could support, and they are
	// ANDed with the ones from wrappedFs
	f.features = (&fs.Features{
		CaseInsensitive:         cipher.NameEncryptionMode() == NameEncryptionOff,
		DuplicateFiles:          true,
		ReadMimeType:            false, // MimeTypes not supported with crypt
		WriteMimeType:           false,
		BucketBased:             true,
		CanHaveEmptyDirectories: true,
	}).Fill(f).Mask(wrappedFs).WrapsFs(f, wrappedFs)

	doChangeNotify := wrappedFs.Features().ChangeNotify
	if doChangeNotify != nil {
		f.features.ChangeNotify = func(notifyFunc func(string, fs.EntryType), pollInterval time.Duration) chan bool {
			wrappedNotifyFunc := func(path string, entryType fs.EntryType) {
				decrypted, err := f.DecryptFileName(path)
				if err != nil {
					fs.Logf(f, "ChangeNotify was unable to decrypt %q: %s", path, err)
					return
				}
				notifyFunc(decrypted, entryType)
			}
			return doChangeNotify(wrappedNotifyFunc, pollInterval)
		}
	}

	return f, err
}

// Options defines the configuration for this backend
type Options struct {
	Remote                  string `config:"remote"`
	FilenameEncryption      string `config:"filename_encryption"`
	DirectoryNameEncryption bool   `config:"directory_name_encryption"`
	Password                string `config:"password"`
	Password2               string `config:"password2"`
	ShowMapping             bool   `config:"show_mapping"`
}

// Fs represents a wrapped fs.Fs
type Fs struct {
	fs.Fs
	name     string
	root     string
	opt      Options
	features *fs.Features // optional features
	cipher   Cipher
}

// Name of the remote (as passed into NewFs)
func (f *Fs) Name() string {
	return f.name
}

// Root of the remote (as passed into NewFs)
func (f *Fs) Root() string {
	return f.root
}

// Features returns the optional features of this Fs
func (f *Fs) Features() *fs.Features {
	return f.features
}

// String returns a description of the FS
func (f *Fs) String() string {
	return fmt.Sprintf("Encrypted drive '%s:%s'", f.name, f.root)
}

// Encrypt an object file name to entries.
func (f *Fs) add(entries *fs.DirEntries, obj fs.Object) {
	remote := obj.Remote()
	decryptedRemote, err := f.cipher.DecryptFileName(remote)
	if err != nil {
		fs.Debugf(remote, "Skipping undecryptable file name: %v", err)
		return
	}
	if f.opt.ShowMapping {
		fs.Logf(decryptedRemote, "Encrypts to %q", remote)
	}
	*entries = append(*entries, f.newObject(obj))
}

// Encrypt an directory file name to entries.
func (f *Fs) addDir(entries *fs.DirEntries, dir fs.Directory) {
	remote := dir.Remote()
	decryptedRemote, err := f.cipher.DecryptDirName(remote)
	if err != nil {
		fs.Debugf(remote, "Skipping undecryptable dir name: %v", err)
		return
	}
	if f.opt.ShowMapping {
		fs.Logf(decryptedRemote, "Encrypts to %q", remote)
	}
	*entries = append(*entries, f.newDir(dir))
}

// Encrypt some directory entries.  This alters entries returning it as newEntries.
func (f *Fs) encryptEntries(entries fs.DirEntries) (newEntries fs.DirEntries, err error) {
	newEntries = entries[:0] // in place filter
	for _, entry := range entries {
		switch x := entry.(type) {
		case fs.Object:
			f.add(&newEntries, x)
		case fs.Directory:
			f.addDir(&newEntries, x)
		default:
			return nil, errors.Errorf("Unknown object type %T", entry)
		}
	}
	return newEntries, nil
}

// List the objects and directories in dir into entries.  The
// entries can be returned in any order but should be for a
// complete directory.
//
// dir should be "" to list the root, and should not have
// trailing slashes.
//
// This should return ErrDirNotFound if the directory isn't
// found.
func (f *Fs) List(dir string) (entries fs.DirEntries, err error) {
	entries, err = f.Fs.List(f.cipher.EncryptDirName(dir))
	if err != nil {
		return nil, err
	}
	return f.encryptEntries(entries)
}

// ListR lists the objects and directories of the Fs starting
// from dir recursively into out.
//
// dir should be "" to start from the root, and should not
// have trailing slashes.
//
// This should return ErrDirNotFound if the directory isn't
// found.
//
// It should call callback for each tranche of entries read.
// These need not be returned in any particular order.  If
// callback returns an error then the listing will stop
// immediately.
//
// Don't implement this unless you have a more efficient way
// of listing recursively that doing a directory traversal.
func (f *Fs) ListR(dir string, callback fs.ListRCallback) (err error) {
	return f.Fs.Features().ListR(f.cipher.EncryptDirName(dir), func(entries fs.DirEntries) error {
		newEntries, err := f.encryptEntries(entries)
		if err != nil {
			return err
		}
		return callback(newEntries)
	})
}

// NewObject finds the Object at remote.
func (f *Fs) NewObject(remote string) (fs.Object, error) {
	o, err := f.Fs.NewObject(f.cipher.EncryptFileName(remote))
	if err != nil {
		return nil, err
	}
	return f.newObject(o), nil
}

type putFn func(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error)

// put implements Put or PutStream
func (f *Fs) put(in io.Reader, src fs.ObjectInfo, options []fs.OpenOption, put putFn) (fs.Object, error) {
	// Encrypt the data into wrappedIn
	wrappedIn, err := f.cipher.EncryptData(in)
	if err != nil {
		return nil, err
	}

	// Find a hash the destination supports to compute a hash of
	// the encrypted data
	ht := f.Fs.Hashes().GetOne()
	var hasher *hash.MultiHasher
	if ht != hash.None {
		hasher, err = hash.NewMultiHasherTypes(hash.NewHashSet(ht))
		if err != nil {
			return nil, err
		}
		// unwrap the accounting
		var wrap accounting.WrapFn
		wrappedIn, wrap = accounting.UnWrap(wrappedIn)
		// add the hasher
		wrappedIn = io.TeeReader(wrappedIn, hasher)
		// wrap the accounting back on
		wrappedIn = wrap(wrappedIn)
	}

	// Transfer the data
	o, err := put(wrappedIn, f.newObjectInfo(src), options...)
	if err != nil {
		return nil, err
	}

	// Check the hashes of the encrypted data if we were comparing them
	if ht != hash.None && hasher != nil {
		srcHash := hasher.Sums()[ht]
		var dstHash string
		dstHash, err = o.Hash(ht)
		if err != nil {
			return nil, errors.Wrap(err, "failed to read destination hash")
		}
		if srcHash != "" && dstHash != "" && srcHash != dstHash {
			// remove object
			err = o.Remove()
			if err != nil {
				fs.Errorf(o, "Failed to remove corrupted object: %v", err)
			}
			return nil, errors.Errorf("corrupted on transfer: %v crypted hash differ %q vs %q", ht, srcHash, dstHash)
		}
	}

	return f.newObject(o), nil
}

// Put in to the remote path with the modTime given of the given size
//
// May create the object even if it returns an error - if so
// will return the object and the error, otherwise will return
// nil and the error
func (f *Fs) Put(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
	return f.put(in, src, options, f.Fs.Put)
}

// PutStream uploads to the remote path with the modTime given of indeterminate size
func (f *Fs) PutStream(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
	return f.put(in, src, options, f.Fs.Features().PutStream)
}

// Hashes returns the supported hash sets.
func (f *Fs) Hashes() hash.Set {
	return hash.Set(hash.None)
}

// Mkdir makes the directory (container, bucket)
//
// Shouldn't return an error if it already exists
func (f *Fs) Mkdir(dir string) error {
	return f.Fs.Mkdir(f.cipher.EncryptDirName(dir))
}

// Rmdir removes the directory (container, bucket) if empty
//
// Return an error if it doesn't exist or isn't empty
func (f *Fs) Rmdir(dir string) error {
	return f.Fs.Rmdir(f.cipher.EncryptDirName(dir))
}

// Purge all files in the root and the root directory
//
// Implement this if you have a way of deleting all the files
// quicker than just running Remove() on the result of List()
//
// Return an error if it doesn't exist
func (f *Fs) Purge() error {
	do := f.Fs.Features().Purge
	if do == nil {
		return fs.ErrorCantPurge
	}
	return do()
}

// Copy src to this remote using server side copy operations.
//
// This is stored with the remote path given
//
// It returns the destination Object and a possible error
//
// Will only be called if src.Fs().Name() == f.Name()
//
// If it isn't possible then return fs.ErrorCantCopy
func (f *Fs) Copy(src fs.Object, remote string) (fs.Object, error) {
	do := f.Fs.Features().Copy
	if do == nil {
		return nil, fs.ErrorCantCopy
	}
	o, ok := src.(*Object)
	if !ok {
		return nil, fs.ErrorCantCopy
	}
	oResult, err := do(o.Object, f.cipher.EncryptFileName(remote))
	if err != nil {
		return nil, err
	}
	return f.newObject(oResult), nil
}

// Move src to this remote using server side move operations.
//
// This is stored with the remote path given
//
// It returns the destination Object and a possible error
//
// Will only be called if src.Fs().Name() == f.Name()
//
// If it isn't possible then return fs.ErrorCantMove
func (f *Fs) Move(src fs.Object, remote string) (fs.Object, error) {
	do := f.Fs.Features().Move
	if do == nil {
		return nil, fs.ErrorCantMove
	}
	o, ok := src.(*Object)
	if !ok {
		return nil, fs.ErrorCantMove
	}
	oResult, err := do(o.Object, f.cipher.EncryptFileName(remote))
	if err != nil {
		return nil, err
	}
	return f.newObject(oResult), nil
}

// DirMove moves src, srcRemote to this remote at dstRemote
// using server side move operations.
//
// Will only be called if src.Fs().Name() == f.Name()
//
// If it isn't possible then return fs.ErrorCantDirMove
//
// If destination exists then return fs.ErrorDirExists
func (f *Fs) DirMove(src fs.Fs, srcRemote, dstRemote string) error {
	do := f.Fs.Features().DirMove
	if do == nil {
		return fs.ErrorCantDirMove
	}
	srcFs, ok := src.(*Fs)
	if !ok {
		fs.Debugf(srcFs, "Can't move directory - not same remote type")
		return fs.ErrorCantDirMove
	}
	return do(srcFs.Fs, f.cipher.EncryptDirName(srcRemote), f.cipher.EncryptDirName(dstRemote))
}

// PutUnchecked uploads the object
//
// This will create a duplicate if we upload a new file without
// checking to see if there is one already - use Put() for that.
func (f *Fs) PutUnchecked(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
	do := f.Fs.Features().PutUnchecked
	if do == nil {
		return nil, errors.New("can't PutUnchecked")
	}
	wrappedIn, err := f.cipher.EncryptData(in)
	if err != nil {
		return nil, err
	}
	o, err := do(wrappedIn, f.newObjectInfo(src))
	if err != nil {
		return nil, err
	}
	return f.newObject(o), nil
}

// CleanUp the trash in the Fs
//
// Implement this if you have a way of emptying the trash or
// otherwise cleaning up old versions of files.
func (f *Fs) CleanUp() error {
	do := f.Fs.Features().CleanUp
	if do == nil {
		return errors.New("can't CleanUp")
	}
	return do()
}

// About gets quota information from the Fs
func (f *Fs) About() (*fs.Usage, error) {
	do := f.Fs.Features().About
	if do == nil {
		return nil, errors.New("About not supported")
	}
	return do()
}

// UnWrap returns the Fs that this Fs is wrapping
func (f *Fs) UnWrap() fs.Fs {
	return f.Fs
}

// EncryptFileName returns an encrypted file name
func (f *Fs) EncryptFileName(fileName string) string {
	return f.cipher.EncryptFileName(fileName)
}

// DecryptFileName returns a decrypted file name
func (f *Fs) DecryptFileName(encryptedFileName string) (string, error) {
	return f.cipher.DecryptFileName(encryptedFileName)
}

// ComputeHash takes the nonce from o, and encrypts the contents of
// src with it, and calcuates the hash given by HashType on the fly
//
// Note that we break lots of encapsulation in this function.
func (f *Fs) ComputeHash(o *Object, src fs.Object, hashType hash.Type) (hashStr string, err error) {
	// Read the nonce - opening the file is sufficient to read the nonce in
	// use a limited read so we only read the header
	in, err := o.Object.Open(&fs.RangeOption{Start: 0, End: int64(fileHeaderSize) - 1})
	if err != nil {
		return "", errors.Wrap(err, "failed to open object to read nonce")
	}
	d, err := f.cipher.(*cipher).newDecrypter(in)
	if err != nil {
		_ = in.Close()
		return "", errors.Wrap(err, "failed to open object to read nonce")
	}
	nonce := d.nonce
	// fs.Debugf(o, "Read nonce % 2x", nonce)

	// Check nonce isn't all zeros
	isZero := true
	for i := range nonce {
		if nonce[i] != 0 {
			isZero = false
		}
	}
	if isZero {
		fs.Errorf(o, "empty nonce read")
	}

	// Close d (and hence in) once we have read the nonce
	err = d.Close()
	if err != nil {
		return "", errors.Wrap(err, "failed to close nonce read")
	}

	// Open the src for input
	in, err = src.Open()
	if err != nil {
		return "", errors.Wrap(err, "failed to open src")
	}
	defer fs.CheckClose(in, &err)

	// Now encrypt the src with the nonce
	out, err := f.cipher.(*cipher).newEncrypter(in, &nonce)
	if err != nil {
		return "", errors.Wrap(err, "failed to make encrypter")
	}

	// pipe into hash
	m, err := hash.NewMultiHasherTypes(hash.NewHashSet(hashType))
	if err != nil {
		return "", errors.Wrap(err, "failed to make hasher")
	}
	_, err = io.Copy(m, out)
	if err != nil {
		return "", errors.Wrap(err, "failed to hash data")
	}

	return m.Sums()[hashType], nil
}

// Object describes a wrapped for being read from the Fs
//
// This decrypts the remote name and decrypts the data
type Object struct {
	fs.Object
	f *Fs
}

func (f *Fs) newObject(o fs.Object) *Object {
	return &Object{
		Object: o,
		f:      f,
	}
}

// Fs returns read only access to the Fs that this object is part of
func (o *Object) Fs() fs.Info {
	return o.f
}

// Return a string version
func (o *Object) String() string {
	if o == nil {
		return "<nil>"
	}
	return o.Remote()
}

// Remote returns the remote path
func (o *Object) Remote() string {
	remote := o.Object.Remote()
	decryptedName, err := o.f.cipher.DecryptFileName(remote)
	if err != nil {
		fs.Debugf(remote, "Undecryptable file name: %v", err)
		return remote
	}
	return decryptedName
}

// Size returns the size of the file
func (o *Object) Size() int64 {
	size, err := o.f.cipher.DecryptedSize(o.Object.Size())
	if err != nil {
		fs.Debugf(o, "Bad size for decrypt: %v", err)
	}
	return size
}

// Hash returns the selected checksum of the file
// If no checksum is available it returns ""
func (o *Object) Hash(ht hash.Type) (string, error) {
	return "", hash.ErrUnsupported
}

// UnWrap returns the wrapped Object
func (o *Object) UnWrap() fs.Object {
	return o.Object
}

// Open opens the file for read.  Call Close() on the returned io.ReadCloser
func (o *Object) Open(options ...fs.OpenOption) (rc io.ReadCloser, err error) {
	var openOptions []fs.OpenOption
	var offset, limit int64 = 0, -1
	for _, option := range options {
		switch x := option.(type) {
		case *fs.SeekOption:
			offset = x.Offset
		case *fs.RangeOption:
			offset, limit = x.Decode(o.Size())
		default:
			// pass on Options to underlying open if appropriate
			openOptions = append(openOptions, option)
		}
	}
	rc, err = o.f.cipher.DecryptDataSeek(func(underlyingOffset, underlyingLimit int64) (io.ReadCloser, error) {
		if underlyingOffset == 0 && underlyingLimit < 0 {
			// Open with no seek
			return o.Object.Open(openOptions...)
		}
		// Open stream with a range of underlyingOffset, underlyingLimit
		end := int64(-1)
		if underlyingLimit >= 0 {
			end = underlyingOffset + underlyingLimit - 1
			if end >= o.Object.Size() {
				end = -1
			}
		}
		newOpenOptions := append(openOptions, &fs.RangeOption{Start: underlyingOffset, End: end})
		return o.Object.Open(newOpenOptions...)
	}, offset, limit)
	if err != nil {
		return nil, err
	}
	return rc, nil
}

// Update in to the object with the modTime given of the given size
func (o *Object) Update(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) error {
	update := func(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
		return o.Object, o.Object.Update(in, src, options...)
	}
	_, err := o.f.put(in, src, options, update)
	return err
}

// newDir returns a dir with the Name decrypted
func (f *Fs) newDir(dir fs.Directory) fs.Directory {
	newDir := fs.NewDirCopy(dir)
	remote := dir.Remote()
	decryptedRemote, err := f.cipher.DecryptDirName(remote)
	if err != nil {
		fs.Debugf(remote, "Undecryptable dir name: %v", err)
	} else {
		newDir.SetRemote(decryptedRemote)
	}
	return newDir
}

// ObjectInfo describes a wrapped fs.ObjectInfo for being the source
//
// This encrypts the remote name and adjusts the size
type ObjectInfo struct {
	fs.ObjectInfo
	f *Fs
}

func (f *Fs) newObjectInfo(src fs.ObjectInfo) *ObjectInfo {
	return &ObjectInfo{
		ObjectInfo: src,
		f:          f,
	}
}

// Fs returns read only access to the Fs that this object is part of
func (o *ObjectInfo) Fs() fs.Info {
	return o.f
}

// Remote returns the remote path
func (o *ObjectInfo) Remote() string {
	return o.f.cipher.EncryptFileName(o.ObjectInfo.Remote())
}

// Size returns the size of the file
func (o *ObjectInfo) Size() int64 {
	size := o.ObjectInfo.Size()
	if size < 0 {
		return size
	}
	return o.f.cipher.EncryptedSize(size)
}

// Hash returns the selected checksum of the file
// If no checksum is available it returns ""
func (o *ObjectInfo) Hash(hash hash.Type) (string, error) {
	return "", nil
}

// Check the interfaces are satisfied
var (
	_ fs.Fs              = (*Fs)(nil)
	_ fs.Purger          = (*Fs)(nil)
	_ fs.Copier          = (*Fs)(nil)
	_ fs.Mover           = (*Fs)(nil)
	_ fs.DirMover        = (*Fs)(nil)
	_ fs.PutUncheckeder  = (*Fs)(nil)
	_ fs.PutStreamer     = (*Fs)(nil)
	_ fs.CleanUpper      = (*Fs)(nil)
	_ fs.UnWrapper       = (*Fs)(nil)
	_ fs.ListRer         = (*Fs)(nil)
	_ fs.Abouter         = (*Fs)(nil)
	_ fs.ObjectInfo      = (*ObjectInfo)(nil)
	_ fs.Object          = (*Object)(nil)
	_ fs.ObjectUnWrapper = (*Object)(nil)
)