// Copyright 2017-2018 DERO Project. All rights reserved.
// Use of this source code in any form is governed by RESEARCH license.
// license can be found in the LICENSE file.
// GPG: 0F39 E425 8C65 3947 702A  8234 08B2 0360 A03A 9DE8
//
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package transaction

//import "fmt"
import "bytes"

//import "encoding/binary"

import "github.com/romana/rlog"

import "github.com/deroproject/derosuite/crypto"

// refer https://cryptonote.org/cns/cns005.txt to understand slightly more ( it DOES NOT cover everything)
// much of these constants are understood from tx_extra.h and cryptonote_format_utils.cpp
// TODO pending test case
type EXTRA_TAG byte

const TX_EXTRA_PADDING EXTRA_TAG = 0 // followed by 1 byte of size, and then upto 255 bytes of padding
const TX_PUBLIC_KEY EXTRA_TAG = 1    // follwed by 32 bytes of tx public key
const TX_EXTRA_NONCE EXTRA_TAG = 2   // followed by 1 byte of size, and then upto 255 bytes of empty nonce

// TX_EXTRA_MERGE_MINING_TAG  we do NOT suppport merged mining at all
// TX_EXTRA_MYSTERIOUS_MINERGATE_TAG  as the name says mysterious we will not bring it

// these 2 fields have complicated parsing of extra, other the code was really simple
const TX_EXTRA_NONCE_PAYMENT_ID EXTRA_TAG = 0           // extra nonce within a non coinbase tx, can be unencrypted, is 32 bytes in size
const TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID EXTRA_TAG = 1 // this is encrypted and is 9 bytes in size

// the field is just named extra and contains CRITICAL information, though some is optional
// parse extra data such as
// tx public key must
// payment id optional
// encrypted payment id optional
func (tx *Transaction) Parse_Extra() bool {
	var err error
	// var length uint64
	var length_int int

	buf := bytes.NewReader(tx.Extra)

	tx.Extra_map = map[EXTRA_TAG]interface{}{}
	tx.PaymentID_map = map[EXTRA_TAG]interface{}{}

	b := make([]byte, 1)
	//var r uint64
	var n int
	for i := 0; ; i++ {
		if buf.Len() == 0 {
			return true
		}
		n, err = buf.Read(b)
		if err != nil {
			return false
		}

		switch EXTRA_TAG(b[0]) {
		case TX_EXTRA_PADDING: // this is followed by 1 byte length, then length bytes of padding
			n, err = buf.Read(b)
			if err != nil {
				rlog.Tracef(1, "Extra padding length could not be parsed txhash %s", tx.GetHash())
				return false
			}
			length_int = int(b[0])
			padding := make([]byte, length_int, length_int)
			n, err = buf.Read(padding)
			if err != nil || n != int(length_int) {
				rlog.Tracef(1, "Extra padding could not be read  txhash %s", tx.GetHash())
				return false
			}

			// Padding is not added to the extra map

		case TX_PUBLIC_KEY: // next 32 bytes are tx public key
			var pkey crypto.Key
			n, err = buf.Read(pkey[:])
			if err != nil || n != 32 {
				rlog.Tracef(1, "Tx public key could not be parsed len=%d err=%s txhash %s", n, err, tx.GetHash())
				return false
			}
			tx.Extra_map[TX_PUBLIC_KEY] = pkey
		case TX_EXTRA_NONCE: // this is followed by 1 byte length, then length bytes of data
			n, err = buf.Read(b)
			if err != nil {
				rlog.Tracef(1, "Extra nonce length could not be parsed txhash %s", tx.GetHash())
				return false
			}

			length_int = int(b[0])

			extra_nonce := make([]byte, length_int, length_int)
			n, err = buf.Read(extra_nonce)
			if err != nil || n != int(length_int) {
				rlog.Tracef(1, "Extra Nonce could not be read  txhash %s", tx.GetHash())
				return false
			}

			switch length_int {
			case 33: // unencrypted 32 byte  payment id
				if extra_nonce[0] == byte(TX_EXTRA_NONCE_PAYMENT_ID) {
					tx.PaymentID_map[TX_EXTRA_NONCE_PAYMENT_ID] = extra_nonce[1:]
				} else {
					rlog.Tracef(1, "Extra Nonce contains invalid payment id  txhash %s", tx.GetHash())
				}

			case 9: // encrypted 9 byte payment id
				if extra_nonce[0] == byte(TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID) {
					tx.PaymentID_map[TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID] = extra_nonce[1:]
				} else {
					rlog.Tracef(1, "Extra Nonce contains invalid encrypted payment id  txhash %s", tx.GetHash())
				}

			default: // consider it as general nonce
				// ignore anything else
			}

			tx.Extra_map[TX_EXTRA_NONCE] = extra_nonce

			// NO MORE TAGS are present

		default: // ignore any other unknown tag or data
			rlog.Tracef(1, "Unhandled TAG %d in tx %s\n", b[0], tx.GetHash())
			return true

		}
	}

	// we should not reach here
	//return true
}

// serialize an extra, this is only required while creating new transactions ( both miner and normal)
// doing this on existing transaction will cause them to fail ( due to different placement order )
func (tx *Transaction) Serialize_Extra() []byte {

	buf := bytes.NewBuffer(nil)

	// this is mandatory
	if _, ok := tx.Extra_map[TX_PUBLIC_KEY]; ok {
		buf.WriteByte(byte(TX_PUBLIC_KEY)) // write marker
		key := tx.Extra_map[TX_PUBLIC_KEY].(crypto.Key)
		buf.Write(key[:]) // write the key
	} else {
		rlog.Tracef(1, "TX does not contain a Public Key, not possible, the transaction will be rejected")
	}

	// if payment id are set, they replace nonce
	// first place unencrypted payment id
	if _, ok := tx.PaymentID_map[TX_EXTRA_NONCE_PAYMENT_ID]; ok {
		data_bytes := tx.PaymentID_map[TX_EXTRA_NONCE_PAYMENT_ID].([]byte)
		if len(data_bytes) == 32 { // payment id is valid
			header := append([]byte{byte(TX_EXTRA_NONCE_PAYMENT_ID)}, data_bytes...)
			tx.Extra_map[TX_EXTRA_NONCE] = header // overwrite extra nonce with this
		}
		rlog.Tracef(1, "unencrypted payment id size mismatch expected = %d actual %d", 32, len(data_bytes))
	}

	if _, ok := tx.PaymentID_map[TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID]; ok {
		data_bytes := tx.PaymentID_map[TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID].([]byte)
		if len(data_bytes) == 8 { // payment id is valid
			header := append([]byte{byte(TX_EXTRA_NONCE_ENCRYPTED_PAYMENT_ID)}, data_bytes...)
			tx.Extra_map[TX_EXTRA_NONCE] = header // overwrite extra nonce with this
		}
		rlog.Tracef(1, "unencrypted payment id size mismatch expected = %d actual %d", 8, len(data_bytes))
	}

	// TX_EXTRA_NONCE is optional
	// if payment is present, it is packed as extra nonce
	if _, ok := tx.Extra_map[TX_EXTRA_NONCE]; ok {
		buf.WriteByte(byte(TX_EXTRA_NONCE)) // write marker
		data_bytes := tx.Extra_map[TX_EXTRA_NONCE].([]byte)

		if len(data_bytes) > 255 {
			rlog.Tracef(1, "TX extra none is spilling, trimming the nonce to 255 bytes")
			data_bytes = data_bytes[:]
		}
		buf.WriteByte(byte(len(data_bytes))) // write length of extra nonce single byte
		buf.Write(data_bytes[:])             // write the nonce data
	}

	// NOTE: we do not support adding padding for the sake of it

	return buf.Bytes()

}

// resize the nonce by this much bytes,
// positive means add  byte
// negative means decrease size
// this is only required during miner tx to solve chicken and problem
/*
func (tx *Transaction) Resize_Extra_Nonce(int resize_amount) {

    nonce_bytes := tx.Extra_map[TX_EXTRA_NONCE].([]byte)
    nonce_bytes = make([]byte, len(nonce_bytes)+resize_amount, len(nonce_bytes)+resize_amount)
    tx.Extra_map[TX_EXTRA_NONCE] = nonce_bytes

    tx.Extra = tx.Serialize_Extra()

}
*/