package cbc

import (
	`bytes`
	gAes `crypto/aes`
	gCipher `crypto/cipher`
	`io`

	`r00t2.io/sshkeys/cipher`
	`r00t2.io/sshkeys/cipher/aes`
	`r00t2.io/sshkeys/cipher/aes/aes128`
	`r00t2.io/sshkeys/internal`
)

// Setup populates a Cipher from a key. The key must include the IV suffixed to the actual key.
func (c *Cipher) Setup(key []byte) (err error) {

	if key == nil || len(key) < aes128.KdfKeySize {
		err = cipher.ErrBadKeyLen
		return
	}

	if c == nil {
		c = &Cipher{}
	}

	c.key = key[0:aes128.KeySize]
	c.iv = key[aes128.KeySize:(aes128.KdfKeySize)]

	return
}

// Name returns the name as used in the key file bytes.
func (c *Cipher) Name() (name string) {

	name = Name

	return
}

// NameBytes returns the byte form of Cipher.Name with leading bytecount allocator.
func (c *Cipher) NameBytes() (name []byte) {

	var err error

	if name, err = internal.PackBytes(Name); err != nil {
		return
	}

	return
}

// BlockSize returns the blocksize of this Cipher.
func (c *Cipher) BlockSize() (size int) {

	size = aes.BlockSize

	return
}

// KdfKeySize returns the target key length from KDF to use with this Cipher.
func (c *Cipher) KdfKeySize() (size int) {

	size = aes128.KeySize

	return
}

/*
	Encrypt encrypts data (a string, []byte, byte, *bytes.Buffer, or *bytes.Reader) to the *bytes.Reader encrypted.

	NOTE: Padding IS applied automatically.

	NOTE: If data is a *bytes.Buffer, no bytes will be consumed -- the bytes are taken in entirety without consuming them (Buffer.Bytes()).
		  It is up to the caller to consume the buffer as desired beforehand or isolate to a specific sub-buffer beforehand to pass to Cipher.Encrypt.

	NOTE: If data is a *bytes.Reader, ALL bytes WILL be consumed.
*/
func (c *Cipher) Encrypt(data interface{}) (encrypted *bytes.Reader, err error) {

	var b []byte
	var cryptDst []byte
	var padded *bytes.Reader
	var cryptBlock gCipher.Block
	var crypter gCipher.BlockMode

	if b, err = internal.SerializeData(data); err != nil {
		return
	}

	if padded, err = c.Pad(b); err != nil {
		return
	}

	b = make([]byte, padded.Len())
	if b, err = io.ReadAll(padded); err != nil {
		return
	}

	cryptDst = make([]byte, len(b))

	if cryptBlock, err = gAes.NewCipher(c.key); err != nil {
		return
	}
	crypter = gCipher.NewCBCEncrypter(cryptBlock, c.iv)

	crypter.CryptBlocks(cryptDst, b)

	encrypted = bytes.NewReader(cryptDst)

	return
}

/*
	AllocateEncrypt is the same as Cipher.Encrypt but includes an unencrypted byte allocator prefix.

	NOTE: Padding IS applied automatically.

	NOTE: If data is a *bytes.Buffer, no bytes will be consumed -- the bytes are taken in entirety without consuming them (Buffer.Bytes()).
		  It is up to the caller to consume the buffer as desired beforehand or isolate to a specific sub-buffer beforehand to pass to Cipher.AllocateEncrypt.

	NOTE: If data is a *bytes.Reader, ALL bytes WILL be consumed.
*/
func (c *Cipher) AllocateEncrypt(data interface{}) (encrypted *bytes.Reader, err error) {

	var b *bytes.Reader
	var buf *bytes.Buffer = new(bytes.Buffer)
	var alloc []byte = make([]byte, 4)

	if b, err = c.Encrypt(data); err != nil {
		return
	}
	if alloc, err = internal.PackBytes(b); err != nil {
		return
	}

	if _, err = buf.Write(alloc); err != nil {
		return
	}
	if _, err = b.WriteTo(buf); err != nil {
		return
	}

	encrypted = bytes.NewReader(buf.Bytes())

	return
}

/*
	Pad will pad data (a string, []byte, byte, or *bytes.Buffer) to the Cipher.BlockSize (if necessary).
	The resulting padded buffer is returned.

	NOTE: If data is a *bytes.Buffer, no bytes will be consumed -- the bytes are taken in entirety without consuming them (Buffer.Bytes()).
		  It is up to the caller to consume the buffer as desired beforehand or isolate to a specific sub-buffer beforehand to pass to Cipher.Pad.

	NOTE: If data is a *bytes.Reader, ALL bytes WILL be consumed.
*/
func (c *Cipher) Pad(data interface{}) (paddedBuf *bytes.Reader, err error) {

	var b []byte
	var padNum int
	var pad []byte
	var buf *bytes.Buffer

	if b, err = internal.UnpackBytes(data); err != nil {
		return
	}
	buf = bytes.NewBuffer(b)

	for padIdx := 1; (buf.Len() % aes.BlockSize) != 0; padIdx++ {

		padNum = padIdx & cipher.PadMod
		pad = []byte{byte(uint32(padNum))}

		if _, err = buf.Write(pad); err != nil {
			return
		}
	}

	return
}

/*
	Decrypt takes a raw byte slice, a *bytes.Buffer, or a *bytes.Reader and returns a plain/decrypted *bytes.Reader.

	NOTE: The decrypted data contains padding. It is up to the caller to remove/strip.

	NOTE: If data is a *bytes.Buffer, no bytes will be consumed -- the bytes are taken in entirety without consuming them (Buffer.Bytes()).
		  It is up to the caller to consume the buffer as desired beforehand or isolate to a specific sub-buffer beforehand to pass to Cipher.Decrypt.

	NOTE: If data is a *bytes.Reader, ALL bytes WILL be consumed.
*/
func (c *Cipher) Decrypt(data interface{}) (decrypted *bytes.Reader, err error) {

	var b []byte
	var decryptDst []byte
	var cryptBlock gCipher.Block
	var decrypter gCipher.BlockMode

	if b, err = internal.SerializeData(data); err != nil {
		return
	}

	decryptDst = make([]byte, len(b))

	if cryptBlock, err = gAes.NewCipher(c.key); err != nil {
		return
	}
	decrypter = gCipher.NewCBCDecrypter(cryptBlock, c.iv)

	decrypter.CryptBlocks(decryptDst, b)

	decrypted = bytes.NewReader(decryptDst)

	return
}

/*
	AllocatedDecrypt is the same as Cipher.Decrypt but assumes that data includes an unencrypted uint32 byte allocator prefix.

	Be *extremely* certain of this, as things can get REALLY weird if you pass in data that doesn't actually have that prefix.

	NOTE: The decrypted data contains padding. It is up to the caller to remove/strip.

	NOTE: If data is a bytes.Buffer pointer, it will consume ONLY the leading prefix and the length of bytes the prefix indicates and no more.

	NOTE: If data is a *bytes.Reader, it will consume ONLY the leading prefix and the length of bytes the prefix indicates and no more.
*/
func (c *Cipher) AllocatedDecrypt(data interface{}) (decrypted *bytes.Reader, err error) {

	var b []byte

	if b, err = internal.UnpackBytes(data); err != nil {
		return
	}
	if decrypted, err = c.Decrypt(b); err != nil {
		return
	}

	return
}

/*
	IsPlain indicates if this Cipher is a plain/null encryption (cipher.null.Null).

	It will always return false. It is included for interface compatability.
*/
func (c *Cipher) IsPlain() (plain bool) {

	plain = false

	return
}