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BlockChain.js
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BlockChain.js
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'use strict';
const SHA256 = require('crypto-js/sha256');
const LevelSandbox = require('./LevelSandbox.js');
const Block = require('./Block.js');
/**
* Stores and validates blockchain using LevelDB
*/
class BlockChain {
constructor() {
const story = Buffer.from('Genesis Star').toString('hex');
this.genesisStar = JSON.parse(`{ "address": "13Ps1qPQALKwXKYNPDi2enycoYEN2hZbGu", "star": { "dec": "25° 29' 23.9", "ra": "12h 50m 26.0s"}}`);
this.genesisStar.star.story = story;
this.bd = new LevelSandbox();
}
generateGenesisBlock(){
const genesisBlock = new Block(this.genesisStar);
genesisBlock.time = this.getCurrentTime();
genesisBlock.hash = SHA256(JSON.stringify(genesisBlock)).toString();
return genesisBlock;
}
getBlockHeight() {
const self = this;
return this.bd.getBlocksCount()
.then((height) => {
if (height === 0) {
return self.bd.saveBlock(0, self.generateGenesisBlock())
.then(() => {
return 1;
});
}
return height;
});
}
addBlock(block) {
const self = this;
return self.getBlockHeight()
.then((it) => self.getBlockByHeight(it - 1))
.then((previousBlock) => {
block.height = previousBlock.height + 1;
block.previousBlockHash = previousBlock.hash;
block.time = self.getCurrentTime();
block.hash = SHA256(JSON.stringify(block)).toString();
return self.bd.saveBlock(block.height, block);
});
}
getCurrentTime() {
return new Date().getTime().toString().slice(0, -3);
}
getBlockByHash(hash){
return this.bd.getBlockByHash(hash);
}
getBlocksByAddress(address){
return this.bd.getBlocksByAddress(address);
}
getBlockByHeight(height) {
const self = this;
return this.getBlockHeight()
.then((blockchainHeight) => {
if (height < blockchainHeight) {
return self.bd.getBlockByHeight(height);
}
return null;
});
}
validateBlock(height) {
return this.getBlockByHeight(height)
.then((block) => {
const originalHash = block.hash;
block.hash = '';
const blockHash = SHA256(JSON.stringify(block)).toString();
return [block.height, blockHash === originalHash];
});
}
validateBlockInChain(height) {
const blocks = [
this.getBlockByHeight(height),
this.getBlockByHeight(height + 1)
];
return Promise.all(blocks)
.then((results) => {
results[0].hash = '';
const blockHash = SHA256(JSON.stringify(results[0])).toString();
return [results[0].height, (results[1].previousBlockHash === blockHash)];
});
}
validateChain() {
const self = this;
return this.getBlockHeight().then((height) => {
const validations = [];
for (let i = 0; i < height; ++i){
if (i < height - 1){
validations.push(self.validateBlockInChain(i));
}
else {
validations.push(self.validateBlock(i));
}
}
return Promise.all(validations).then((results) => {
const errorLog = [];
results.forEach((element) => {
if (!element[1]) {
errorLog.push(element[0]);
}
});
return errorLog;
});
});
}
_modifyBlock(height, block) {
const self = this;
return new Promise((resolve, reject) => {
self.bd.saveBlock(height, block)
.then((blockModified) => {
resolve(blockModified);
})
.catch((err) => {
console.log(err);
reject(err);
});
});
}
}
module.exports = BlockChain;