/*!
 * minerblock.js - miner block object for bcoin (because we can)
 * Copyright (c) 2014-2015, Fedor Indutny (MIT License)
 * Copyright (c) 2014-2016, Christopher Jeffrey (MIT License).
 * https://github.com/bcoin-org/bcoin
 */

'use strict';

var utils = require('../utils/utils');
var co = require('../utils/co');
var crypto = require('../crypto/crypto');
var assert = require('assert');
var constants = require('../protocol/constants');
var Network = require('../protocol/network');
var BN = require('bn.js');
var EventEmitter = require('events').EventEmitter;
var TX = require('../primitives/tx');
var Block = require('../primitives/block');
var Input = require('../primitives/input');
var Output = require('../primitives/output');
var time = require('../net/timedata');
var mine = require('./mine');
var workers = require('../workers/workers');

/**
 * MinerBlock
 * @exports MinerBlock
 * @constructor
 * @param {Object} options
 * @param {ChainEntry} options.tip
 * @param {Number} options.height
 * @param {Number} options.target - Compact form.
 * @param {Base58Address} options.address - Payout address.
 * @param {Boolean} options.witness - Allow witness
 * transactions, mine a witness block.
 * @param {String} options.coinbaseFlags
 * @property {Block} block
 * @property {TX} coinbase
 * @property {BN} hashes - Number of hashes attempted.
 * @property {Number} rate - Hash rate.
 * @emits MinerBlock#status
 */

function MinerBlock(options) {
  if (!(this instanceof MinerBlock))
    return new MinerBlock(options);

  EventEmitter.call(this);

  this.tip = options.tip;
  this.version = options.version;
  this.height = options.tip.height + 1;
  this.bits = options.bits;
  this.target = utils.fromCompact(this.bits).toArrayLike(Buffer, 'le', 32);
  this.flags = options.flags;
  this.extraNonce = new BN(0);
  this.iterations = 0;
  this.coinbaseFlags = options.coinbaseFlags;
  this.witness = options.witness;
  this.address = options.address;
  this.network = Network.get(options.network);
  this.destroyed = false;

  this.sigops = 0;
  this.weight = 0;

  this.coinbase = new TX();
  this.coinbase.mutable = true;

  this.block = new Block();
  this.block.mutable = true;

  this._init();
}

utils.inherits(MinerBlock, EventEmitter);

/**
 * Nonce range interval.
 * @const {Number}
 * @default
 */

MinerBlock.INTERVAL = 0xffffffff / 1500 | 0;

MinerBlock.prototype.__defineGetter__('hashes', function() {
  return this.iterations * 0xffffffff + this.block.nonce;
});

MinerBlock.prototype.__defineGetter__('rate', function() {
  return (this.block.nonce / (utils.now() - this.begin)) | 0;
});

/**
 * Initialize the block.
 * @private
 */

MinerBlock.prototype._init = function _init() {
  var block = this.block;
  var cb = this.coinbase;
  var input, output, hash, witnessNonce;

  // Coinbase input.
  input = new Input();

  // Height (required in v2+ blocks)
  input.script.set(0, new BN(this.height));

  // extraNonce - incremented when
  // the nonce overflows.
  input.script.set(1, this.extraNonce);

  // Add a nonce to ensure we don't
  // collide with a previous coinbase
  // of ours. This isn't really
  // necessary nowdays due to bip34
  // (used above).
  input.script.set(2, utils.nonce());

  // Let the world know this little
  // miner succeeded.
  input.script.set(3, this.coinbaseFlags);

  input.script.compile();

  cb.inputs.push(input);

  // Reward output.
  output = new Output();
  output.script.fromAddress(this.address);

  cb.outputs.push(output);

  // If we're using segwit, we need to
  // set up the nonce and commitment.
  if (this.witness) {
    // Our witness nonce is the hash256
    // of the previous block hash.
    hash = new Buffer(this.tip.hash, 'hex');
    witnessNonce = crypto.hash256(hash);

    // Set up the witness nonce.
    input.witness.set(0, witnessNonce);
    input.witness.compile();

    // Commitment output.
    cb.outputs.push(new Output());
  }

  // Setup our block.
  block.version = this.version;
  block.prevBlock = this.tip.hash;
  block.merkleRoot = constants.NULL_HASH;
  block.ts = Math.max(time.now(), this.tip.ts + 1);
  block.bits = this.bits;
  block.nonce = 0;
  block.height = this.height;

  block.addTX(cb);

  // Update coinbase since our coinbase was added.
  this.updateCoinbase();

  // Create our merkle root.
  this.updateMerkle();
};

/**
 * Update the commitment output for segwit.
 */

MinerBlock.prototype.updateCommitment = function updateCommitment() {
  var output = this.coinbase.outputs[1];
  var flags = this.coinbaseFlags;
  var hash;

  // Recalculate witness merkle root.
  hash = this.block.getCommitmentHash();

  // Update commitment.
  output.script.clear();
  output.script.fromCommitment(hash, flags);
};

/**
 * Update the extra nonce and coinbase reward.
 */

MinerBlock.prototype.updateCoinbase = function updateCoinbase() {
  var input = this.coinbase.inputs[0];
  var output = this.coinbase.outputs[0];

  // Update extra nonce.
  input.script.set(1, this.extraNonce);
  input.script.compile();

  // Update reward.
  output.value = this.block.getReward(this.network);
};

/**
 * Increment the extraNonce.
 */

MinerBlock.prototype.updateNonce = function updateNonce() {
  this.block.ts = Math.max(time.now(), this.tip.ts + 1);

  // Overflow the nonce and increment the extraNonce.
  this.block.nonce = 0;
  this.extraNonce.iaddn(1);

  // We incremented the extraNonce, need to update coinbase.
  this.updateCoinbase();

  // We changed the coinbase, need to update merkleRoot.
  this.updateMerkle();
};

/**
 * Rebuild the merkle tree and update merkle root as well as the
 * timestamp (also calls {@link MinerBlock#updateCommitment}
 * if segwit is enabled).
 */

MinerBlock.prototype.updateMerkle = function updateMerkle() {
  // Always update commitment before updating merkle root.
  // The updated commitment output will change the merkle root.
  if (this.witness)
    this.updateCommitment();

  // Update timestamp.
  this.block.ts = Math.max(time.now(), this.tip.ts + 1);

  // Recalculate merkle root.
  this.block.merkleRoot = this.block.getMerkleRoot('hex');
};

/**
 * Add a transaction to the block. Rebuilds the merkle tree,
 * updates coinbase and commitment.
 * @param {TX} tx
 * @returns {Boolean} Whether the transaction was successfully added.
 */

MinerBlock.prototype.addTX = function addTX(tx) {
  var weight, sigops;

  assert(!tx.mutable, 'Cannot add mutable TX to block.');

  if (this.block.hasTX(tx))
    return false;

  weight = tx.getWeight();
  sigops = tx.getSigopsWeight(this.flags);

  if (this.weight + weight > constants.block.MAX_WEIGHT)
    return false;

  if (this.sigops + sigops > constants.block.MAX_SIGOPS_WEIGHT)
    return false;

  if (!this.witness && tx.hasWitness())
    return false;

  // Add the tx to our block
  this.block.addTX(tx.clone());

  // Update coinbase value
  this.updateCoinbase();

  // Update merkle root for new coinbase and new tx
  this.updateMerkle();

  return true;
};

/**
 * Fill the block with sorted mempool entries.
 * @param {MempoolEntry[]} entries
 */

MinerBlock.prototype.build = function build(entries) {
  var len = Math.min(entries.length, constants.block.MAX_SIZE);
  var i, entry, tx, weight, sigops;

  this.weight = this.block.getWeight() + 28;
  this.sigops = this.coinbase.getSigopsWeight(this.flags);

  for (i = 0; i < len; i++) {
    entry = entries[i];
    tx = entry.tx;

    weight = tx.getWeight();
    sigops = tx.getSigopsWeight(this.flags);

    if (this.weight + weight > constants.block.MAX_WEIGHT)
      break;

    if (this.sigops + sigops > constants.block.MAX_SIGOPS_WEIGHT)
      break;

    this.weight += weight;
    this.sigops += sigops;

    // Add the tx to our block
    this.block.addTX(tx.clone());
  }

  // Update coinbase value
  this.updateCoinbase();

  // Update merkle root for new coinbase and new tx
  this.updateMerkle();

  assert(this.block.getWeight() <= this.weight);
};

/**
 * Hash until the nonce overflows.
 * @returns {Boolean} Whether the nonce was found.
 */

MinerBlock.prototype.findNonce = function findNonce() {
  var block = this.block;
  var target = this.target;
  var data = block.abbr();
  var interval = MinerBlock.INTERVAL;
  var min = 0;
  var max = interval;
  var nonce;

  while (max <= 0xffffffff) {
    nonce = mine(data, target, min, max);

    if (nonce !== -1)
      break;

    block.nonce = max;

    min += interval;
    max += interval;

    this.sendStatus();
  }

  return nonce;
};

/**
 * Hash until the nonce overflows.
 * @returns {Boolean} Whether the nonce was found.
 */

MinerBlock.prototype.findNonceAsync = co(function* findNonceAsync() {
  var block = this.block;
  var target = this.target;
  var interval = MinerBlock.INTERVAL;
  var min = 0;
  var max = interval;
  var data, nonce;

  while (max <= 0xffffffff) {
    data = block.abbr();
    nonce = yield workers.pool.mine(data, target, min, max);

    if (nonce !== -1)
      break;

    if (this.destroyed)
      return nonce;

    block.nonce = max;

    min += interval;
    max += interval;

    this.sendStatus();
  }

  return nonce;
});

/**
 * Mine synchronously until the block is found.
 * @returns {Block}
 */

MinerBlock.prototype.mine = function mine() {
  var nonce;

  // Track how long we've been at it.
  this.begin = utils.now();

  assert(this.block.ts > this.tip.ts);

  for (;;) {
    nonce = this.findNonce();

    if (nonce !== -1)
      break;

    this.iterate();
  }

  this.block.nonce = nonce;
  this.block.mutable = false;
  this.coinbase.mutable = false;

  return this.block;
};

/**
 * Mine asynchronously until the block is found.
 * @returns {Promise} - Returns {@link Block}.
 */

MinerBlock.prototype.mineAsync = co(function* mineAsync() {
  var nonce;

  // Track how long we've been at it.
  this.begin = utils.now();

  assert(this.block.ts > this.tip.ts);

  for (;;) {
    nonce = yield this.findNonceAsync();

    if (nonce !== -1)
      break;

    if (this.destroyed)
      return;

    this.iterate();
  }

  this.block.nonce = nonce;
  this.block.mutable = false;
  this.coinbase.mutable = false;

  return this.block;
});

/**
 * Increment extraNonce, rebuild merkletree.
 */

MinerBlock.prototype.iterate = function iterate() {
  var block = this.block;
  var tip = this.tip;
  var now = time.now();

  // Keep track of our iterations.
  this.iterations++;

  // Send progress report.
  this.sendStatus();

  // If we took more a second or more (likely),
  // skip incrementing the extra nonce and just
  // update the timestamp. This improves
  // performance because we do not have to
  // recalculate the merkle root.
  if (now > block.ts && now > tip.ts) {
    block.ts = now;
    // Overflow the nonce
    block.nonce = 0;
    return;
  }

  // Overflow the nonce and increment the extraNonce.
  this.updateNonce();
};

/**
 * Send a progress report (emits `status`).
 */

MinerBlock.prototype.sendStatus = function sendStatus() {
  this.emit('status', {
    block: this.block,
    target: this.block.bits,
    hashes: this.hashes,
    hashrate: this.rate,
    height: this.height,
    best: utils.revHex(this.tip.hash)
  });
};

/**
 * Destroy the minerblock. Stop mining.
 */

MinerBlock.prototype.destroy = function destroy() {
  this.destroyed = true;
};

/*
 * Expose
 */

module.exports = MinerBlock;