const ChainUtil = require('../chain-util');
const { DIFFICULTY, MINE_RATE } = require('../config');

class Block {
  constructor(timestamp,BlockNum, lastHash, hash, data, nonce, 
              difficulty) {
    this.timestamp = timestamp;
    this.BlockNum  = BlockNum;
    this.lastHash = lastHash;
    this.hash = hash;
    this.data = data;
    this.nonce = nonce;
    this.difficulty = difficulty || DIFFICULTY;
  }
  toString() {
    return `Block -
      Timestamp : ${this.timestamp}
      BlockNum  : ${this.BlockNum}
      Last Hash : ${this.lastHash.substring(0, 10)}
      Hash      : ${this.hash.substring(0, 10)}
      Nonce     : ${this.nonce}
      Difficulty: ${this.difficulty}
      Data      : ${this.data[0].length}`;
  }
  static genesis() {
    return new this('Genesis-time',0, '-----', 'First-Hash', 
                    [], 0, DIFFICULTY);
  }
  static mineBlock(lastBlock, data) {
    let hash, timestamp;
    const lastHash = lastBlock.hash;
    let { difficulty } = lastBlock;
    let nonce = 0;
    let BlockNum = lastBlock.BlockNum + 1;
    do {
      nonce++;
      timestamp = Date.now();
      difficulty = Block.adjustDifficulty(lastBlock, timestamp);
      hash = Block.hash(timestamp, lastHash, data, nonce, difficulty);
    } while (hash.substring(0, difficulty) !== '0'.repeat(difficulty));
      return new this(timestamp,BlockNum, lastHash, hash, data, nonce, 
      difficulty);}
  static hash(timestamp,lastHash, data, nonce, difficulty) {
    return ChainUtil.hash(`${timestamp}${lastHash}${data}${nonce}
                           ${difficulty}`).toString();
  }
  static blockHash(block) {
    const { timestamp, lastHash, data, nonce, difficulty } = block;
    return Block.hash(timestamp, lastHash, data, nonce, difficulty);
  }
  static adjustDifficulty(lastBlock, currentTime) {
    let { difficulty } = lastBlock;
    difficulty = lastBlock.timestamp + MINE_RATE > currentTime ?
      difficulty + 1 : difficulty - 1;
    return difficulty;
  }
}
module.exports = Block;