From e8b9ff4a9f2ea31d7822833dc21c86bba813942c Mon Sep 17 00:00:00 2001
From: MoneroOcean <support@moneroocean.stream>
Date: Fri, 30 Oct 2020 22:42:21 +0000
Subject: [PATCH] Draft implementation of Ravencoin utils

---
 index.js | 136 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 133 insertions(+), 3 deletions(-)

diff --git a/index.js b/index.js
index 1642e66..68ab1d8 100644
--- a/index.js
+++ b/index.js
@@ -1,5 +1,135 @@
-module.exports = function () {
-    let obj = require('bindings')('cryptoforknote.node')();
-    return obj;
+module.exports = require('bindings')('cryptoforknote.node');
+
+const SHA3    = require('sha3');
+const bignum  = require('bignum');
+const bitcoin = require('bitcoinjs-lib');
+const promise = require('promise');
+const merklebitcoin = promise.denodeify(require('merkle-bitcoin'));
+
+function scriptCompile(addrHash) {
+  return bitcoin.script.compile([
+    bitcoin.opcodes.OP_DUP,
+    bitcoin.opcodes.OP_HASH160,
+    addrHash,
+    bitcoin.opcodes.OP_EQUALVERIFY,
+    bitcoin.opcodes.OP_CHECKSIG
+  ]);
+}
+
+function reverseBuffer(buff) {
+  let reversed = new Buffer(buff.length);
+  for (var i = buff.length - 1; i >= 0; i--) reversed[buff.length - i - 1] = buff[i];
+  return reversed;
+}
+
+function getMerkleRoot(rpcData, generateTxRaw) {
+  hashes = [ reverseBuffer(new Buffer(generateTxRaw, 'hex')).toString('hex') ];
+  rpcData.transactions.forEach(function (value) {
+    if (value.txid !== undefined) {
+      hashes.push(value.txid);
+    } else {
+      hashes.push(value.hash);
+    }
+  });
+  if (hashes.length === 1) return hashes[0];
+  return Object.values(merklebitcoin(hashes))[2].root;
 };
 
+function varIntBuffer(n) {
+  if (n < 0xfd) {
+    return new Buffer([n]);
+  } else if (n <= 0xffff) {
+    let buff = new Buffer(3);
+    buff[0] = 0xfd;
+    buff.writeUInt16LE(n, 1);
+    return buff;
+  } else if (n <= 0xffffffff) {
+    let buff = new Buffer(5);
+    buff[0] = 0xfe;
+    buff.writeUInt32LE(n, 1);
+    return buff;
+  } else {
+    let buff = new Buffer(9);
+    buff[0] = 0xff;
+    buff.writeUInt64LE(n, 1);
+    return buff;
+  }
+};
+
+module.exports.RavenBlockTemplate = function(rpcData, poolAddress) {
+  // epoch length
+  const EPOCH_LENGTH = 7500;
+  const poolAddrHash = bitcoin.address.fromBase58Check(poolAddress).hash;
+  let txCoinbase = new bitcoin.Transaction();
+  { // input for coinbase tx
+    let blockHeightSerial = rpcData.height.toString(16).length % 2 === 0 ?
+                            rpcData.height.toString(16) :
+                            '0' + rpcData.height.toString(16);
+    const bytesHeight = Math.ceil((rpcData.height << 1).toString(2).length / 8);
+    const lengthDiff  = blockHeightSerial.length/2 - bytesHeight;
+    for (let i = 0; i < lengthDiff; i++) blockHeightSerial = blockHeightSerial + '00';
+    const serializedBlockHeight = new Buffer.concat([
+      new Buffer('0' + bytesHeight, 'hex'),
+      reverseBuffer(new Buffer(blockHeightSerial, 'hex')),
+      new Buffer('00', 'hex') // OP_0
+    ]);
+
+    txCoinbase.addInput(
+      new Buffer('0000000000000000000000000000000000000000000000000000000000000000', 'hex'),
+      0xFFFFFFFF, 0xFFFFFFFF,
+      new Buffer.concat([serializedBlockHeight, Buffer('6b6177706f77', 'hex')])
+    );
+
+    txCoinbase.addOutput(scriptCompile(poolAddrHash), Math.floor(rpcData.coinbasevalue));
+
+    if (rpcData.default_witness_commitment !== undefined) {
+      txCoinbase.addOutput(new Buffer(rpcData.default_witness_commitment, 'hex'), 0);
+    }
+  }
+  const merkleRoot = getMerkleRoot(rpcData, txCoinbase.getHash().toString('hex'));
+
+  let header = new Buffer(80);
+  { let position = 0;
+    header.writeUInt32BE(rpcData.height, position, 4);                  // height         42-46
+    header.write(rpcData.bits, position += 4, 4, 'hex');                // bits           47-50
+    header.writeUInt32BE(rpcData.curtime, position += 4, 4, 'hex');     // nTime          51-54
+    header.write(merkleRoot, position += 4, 32, 'hex');                 // merkelRoot     55-87
+    header.write(rpcData.previousblockhash, position += 32, 32, 'hex'); // prevblockhash  88-120
+    header.writeUInt32BE(rpcData.version, position += 32, 4);           // version        121-153
+    header = reverseBuffer(header);
+  }
+  
+  let blob = new Buffer.concat([
+    header, // 80 bytes
+    new Buffer('EEEEEEEEEEEEEEEE', 'hex'), // 8 bytes
+    new Buffer('EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE', 'hex'), // 32 bytes
+    varIntBuffer(rpcData.transactions.length + 1)
+  ]);
+  const offset1 = blob.length; 
+  blob = new Buffer.concat([ blob, new Buffer(txCoinbase.toHex(), 'hex') ]);
+
+  rpcData.transactions.forEach(function (value) {
+    blob = new Buffer.concat([ blob, new Buffer(value.data, 'hex') ]);
+  });
+
+  let sha3 = new SHA3.SHA3Hash(256);
+  let seedhash_buf = new Buffer(32, 0);
+  const epoch_number = Math.floor(rpcData.height / EPOCH_LENGTH);
+  for (let i=0; i < epoch_number; i++) {
+    seedhash_buf = sha3.update(seedhash_buf).digest();
+    sha3.reset();
+  }
+  const seed_hash = seedhash_buf.toString('hex');
+
+  const diff1 = 0x00000000ff000000000000000000000000000000000000000000000000000000;
+  const difficulty = parseFloat((diff1 / bignum(rpcData.target, 16).toNumber()).toFixed(9))
+
+  return {
+    blocktemplate_blob: blob,
+    reserved_offset:    offset1 + 4 /* txCoinbase.version */ + 1 /* txCoinbase.marker */ + 1 /* txCoinbase.flag */ + 1 /* txCoinbase.vinLen */,
+    seed_hash:          seed_hash,
+    difficulty:         difficulty,
+    height:             rpcData.height,
+    rpc:                rpcData,
+  };
+};