const fs = require('fs');

const DB = require('./platform/db').default;
const Helpers = require('./util/helpers').default;
const Constant = require('./constant').default;
const Config = require('./config').default;

const options = {
  noMetaSync: true,
  noSync: true
};

const blockchainDB = new DB(Config.BLOCKCHAIN_DATABASE, options);
const blockchainReader = blockchainDB.initTxn();
const addressDB = new DB(Config.ADDRESS_DATABASE, options);

const getBlockTxs = (hash) => {
  const key = Buffer.concat([Buffer.from(Constant.BLOCK_TX_PREFIX), hash]);

  return blockchainDB.get(blockchainReader, key);
};

const saveFile = (filename, data) => {
  return new Promise((resolve, reject) => {
    fs.writeFile(filename, data, 'utf8', (error) => {
      if (error) {
        return reject(error);
      }

      return resolve(true);
    });
  });
};

const getBlockByHash = async (hash) => {
  const key = Buffer.concat([
    Buffer.from(Constant.BLOCK_PREFIX),
    hash,
    Buffer.from(Constant.BLOCK_SUFFIX)
  ]);
  const data = blockchainDB.get(blockchainReader, key);

  if (!data) {
    return null;
  }

  const block = Helpers.JSONToObject(data.toString());

  const txs = getBlockTxs(hash);

  block.data = await Helpers.decompressData(txs, 'array');
  delete block.txCount;
  return block;
};

const fillBalances = async () => {
  const toAddress = {};
  const fromAddress = {};
  const cursor = blockchainDB.initCursor(blockchainReader);
  const prefix = Buffer.from(Constant.CHAIN_PREFIX);
  const startKey = Buffer.concat([
    prefix,
    Helpers.writeVarInt(0)
  ]);

  let cursorValue = cursor.goToRange(startKey);

  while (cursorValue) {
    const key = blockchainDB.get(
      blockchainReader,
      cursorValue
    );
    const block = await getBlockByHash(key);

    if (!block) {
      break;
    }

    block.data.forEach((tx) => {
      if (tx.type === 'regular') {
        // populate from and to objects
      }
    });

    cursorValue = cursor.goToNext();
    console.log(`Scanned block: ${block.index}`);
  }

  cursor.close();
  blockchainReader.abort();
  addressDB.close();
  blockchainDB.close();

  await saveFile('fromAddress.json', JSON.stringify(fromAddress, null, 2));
  await saveFile('toAddress.json', JSON.stringify(toAddress, null, 2));
};

fillBalances().then(() => {
  console.log('Completed');
});