var bcoin = require('../bcoin');
var utils = bcoin.utils;

function Block(data, subtype) {
  if (!(this instanceof Block))
    return new Block(data, subtype);

  this.type = 'block';
  this.subtype = subtype;
  this.version = data.version;
  this.prevBlock = utils.toHex(data.prevBlock);
  this.merkleRoot = utils.toHex(data.merkleRoot);
  this.ts = data.ts;
  this.bits = data.bits;
  this.nonce = data.nonce;
  this.totalTX = data.totalTX;
  this.hashes = (data.hashes || []).map(function(hash) {
    return utils.toHex(hash);
  });
  this.flags = data.flags || [];

  // List of matched TXs
  this.tx = [];
  this.invalid = false;

  if (this.subtype === 'block') {
    var self = this;
    this.txs = data.txs || [];
    this.txs = this.txs.map(function(tx) {
      tx = bcoin.tx(tx);
      tx.block = self.hash('hex');
      tx.ts = tx.ts || self.ts;
      return tx;
    });
    this.tx = this.txs.map(function(tx) {
      return tx.hash('hex');
    });
    this.invalid = !this._checkBlock();
    this.hashes = this.merkleTree;
  }

  this._hash = null;

  // Verify partial merkle tree and fill `ts` array
  this._verifyMerkle();
}
module.exports = Block;

Block.prototype.hash = function hash(enc) {
  // Hash it
  if (!this._hash)
    this._hash = utils.toHex(utils.dsha256(this.abbr()));
  return enc === 'hex' ? this._hash : utils.toArray(this._hash, 'hex');
};

Block.prototype.abbr = function abbr() {
  var res = new Array(80);
  utils.writeU32(res, this.version, 0);
  utils.copy(utils.toArray(this.prevBlock, 'hex'), res, 4);
  utils.copy(utils.toArray(this.merkleRoot, 'hex'), res, 36);
  utils.writeU32(res, this.ts, 68);
  utils.writeU32(res, this.bits, 72);
  utils.writeU32(res, this.nonce, 76);

  return res;
};

Block.prototype.verify = function verify() {
  return !this.invalid && utils.testTarget(this.bits, this.hash());
};

Block.prototype.render = function render() {
  return bcoin.protocol.framer.block(this, this.subtype);
};

Block.prototype.hasTX = function hasTX(hash) {
  return this.tx.indexOf(hash) !== -1;
};

Block.prototype._verifyMerkle = function verifyMerkle() {
  var height = 0;

  if (this.subtype === 'block')
    return;

  // Count leafs
  for (var i = this.totalTX; i > 0; i >>= 1)
    height++;
  if (this.totalTX > (1 << (height - 1)))
    height++;

  var tx = [];
  var i = 0;
  var j = 0;
  var hashes = this.hashes;
  var flags = this.flags;

  var root = visit(1);
  if (!root || root !== this.merkleRoot) {
    this.invalid = true;
    return;
  }
  this.tx = tx;
  function visit(depth) {
    if (i === flags.length * 8 || j === hashes.length)
      return null;

    var flag = (flags[i >> 3] >>> (i & 7)) & 1;
    i++;

    if (flag === 0 || depth === height) {
      if (depth === height)
        tx.push(hashes[j]);
      return hashes[j++];
    }

    // Go deeper
    var left = visit(depth + 1);
    if (!left)
      return null;
    var right = visit(depth + 1);
    if (right === left)
      return null;
    if (!right)
      right = left;
    return utils.toHex(utils.dsha256(left + right, 'hex'));
  }
};

Block.prototype._buildMerkle = function buildMerkle() {
  var merkleTree = [];
  for (var i = 0; i < this.txs.length; i++) {
    merkleTree.push(this.txs[i].hash('hex'));
  }
  var j = 0;
  for (var size = this.txs.length; size > 1; size = ((size + 1) / 2) | 0) {
    for (var i = 0; i < size; i += 2) {
      var i2 = Math.min(i + 1, size - 1);
      var hash = utils.dsha256(merkleTree[j+i] + merkleTree[j+i2], 'hex');
      merkleTree.push(utils.toHex(hash));
    }
    j += size;
  }
  return merkleTree;
};

// This mimics the behavior of CheckBlockHeader()
// and CheckBlock() in bitcoin/src/main.cpp.
Block.prototype._checkBlock = function checkBlock() {
  // Check proof of work matches claimed amount
  if (!utils.testTarget(this.bits, this.hash()))
    return false;

  // Check timestamp
  if (this.ts > (Date.now() / 1000) + 2 * 60 * 60)
    return false;

  // Size of all txs cant be bigger than MAX_BLOCK_SIZE
  if (this.txs.length > bcoin.protocol.constants.block.maxSize)
    return false;

  // First TX must be a coinbase
  if (!this.txs.length ||
      this.txs[0].inputs.length !== 1 ||
      +this.txs[0].inputs[0].out.hash !== 0)
    return false;

  // The rest of the txs must not be coinbases
  for (var i = 1; i < this.txs.length; i++) {
    if (this.txs[i].inputs.length === 1 &&
        +this.txs[i].inputs[0].out.hash === 0)
      return false;
  }

  // Build MerkleTree
  this.merkleTree = this._buildMerkle();

  // Check for duplicate tx ids
  var unique = {};
  for (var i = 0; i < this.txs.length; i++) {
    var hash = this.txs[i].hash('hex');
    if (unique[hash])
      return false;
    unique[hash] = true;
  }

  // Check merkle root
  return this.merkleTree[this.merkleTree.length - 1] === this.merkleRoot;
};

Block.prototype.toJSON = function toJSON() {
  return {
    v: '1',
    type: 'block',
    subtype: this.subtype,
    hash: this.hash('hex'),
    prevBlock: this.prevBlock,
    ts: this.ts,
    block: utils.toHex(bcoin.protocol.framer.block(this, this.subtype))
  };
};

Block.fromJSON = function fromJSON(json) {
  utils.assert.equal(json.v, 1);
  utils.assert.equal(json.type, 'block');

  var raw = utils.toArray(json.block, 'hex');

  var parser = new bcoin.protocol.parser();

  var data = json.subtype === 'merkleblock' ?
    parser.parseMerkleBlock(raw) :
    parser.parseBlock(raw);

  var block = new bcoin.block(data, json.subtype);

  block._hash = json.hash;

  return block;
};