blockchain.js

function BlockChain(difficulty) {
	
	this.blocks = [];
	this.difficulty = difficulty;

	this.add = function(block) {  // a new kid on the blockchain
		this.blocks.push(block);
	}

	this.get = function(i) {  // get the block # i
		return this.blocks[i];
	}

	this.getDifficulty = function() {  // the the current difficulty level
		return this.difficulty;
	}

	this.size = function() {    // How many blocks ?
		return this.blocks.length;
	}

	this.getLast = function() {   // give me the latest
		return this.blocks.length > 0 ? this.blocks[this.blocks.length - 1] : null;
	}

	this.isValid = function(currentBlock, previousBlock, diffTarget) {  // A helper to validate the current Block with the previous in the blockchain
		currentHash = currentBlock.getHash();
		if( (currentHash.indexOf(diffTarget) < 0)  // the block has not been mined
			|| (currentHash != currentBlock.computeHash())   // the block hash has been altered
			|| (currentBlock.getPreviousHash() != previousBlock.getHash()))  { // the previous Block hash has changed
				return false;
		}	
		return true;
	}

	this.checkDataIntegrity = function() {   // Are you trying to cheat ?
		var curBlock,prevBlock,currentTarget;
		var difficultyTarget = Array(this.difficulty).join("0");

		for(var i = 1; i < this.blocks.length; i++) {
			curBlock = this.blocks[i];
			prevBlock = this.blocks[i-1];
			if(!this.isValid(curBlock , prevBlock, difficultyTarget)) {
				console.log("There is an incosistency in the blockchain, block # " + i);
				return false;
			}		
		}
		console.log("The Blockchain is valid!");
		return true;
	}
}

module.exports = BlockChain;