const ObservableStore = require('obs-store') const extend = require('xtend') const BN = require('ethereumjs-util').BN const EthQuery = require('eth-query') class RecentBlocksController { constructor (opts = {}) { const { blockTracker, provider } = opts this.blockTracker = blockTracker this.ethQuery = new EthQuery(provider) this.historyLength = opts.historyLength || 40 const initState = extend({ recentBlocks: [], }, opts.initState) this.store = new ObservableStore(initState) this.blockTracker.on('block', this.processBlock.bind(this)) this.backfill() } resetState () { this.store.updateState({ recentBlocks: [], }) } processBlock (newBlock) { const block = this.mapTransactionsToPrices(newBlock) const state = this.store.getState() state.recentBlocks.push(block) while (state.recentBlocks.length > this.historyLength) { state.recentBlocks.shift() } this.store.updateState(state) } backfillBlock (newBlock) { const block = this.mapTransactionsToPrices(newBlock) const state = this.store.getState() if (state.recentBlocks.length < this.historyLength) { state.recentBlocks.unshift(block) } this.store.updateState(state) } mapTransactionsToPrices (newBlock) { const block = extend(newBlock, { gasPrices: newBlock.transactions.map((tx) => { return tx.gasPrice }), }) delete block.transactions return block } async backfill() { this.blockTracker.once('block', async (block) => { let blockNum = block.number let recentBlocks let state = this.store.getState() recentBlocks = state.recentBlocks while (recentBlocks.length < this.historyLength) { try { let blockNumBn = new BN(blockNum.substr(2), 16) const newNum = blockNumBn.subn(1).toString(10) const newBlock = await this.getBlockByNumber(newNum) if (newBlock) { this.backfillBlock(newBlock) blockNum = newBlock.number } state = this.store.getState() recentBlocks = state.recentBlocks } catch (e) { log.error(e) } await this.wait() } }) } async wait () { return new Promise((resolve) => { setTimeout(resolve, 100) }) } async getBlockByNumber (number) { const bn = new BN(number) return new Promise((resolve, reject) => { this.ethQuery.getBlockByNumber('0x' + bn.toString(16), true, (err, block) => { if (err) reject(err) resolve(block) }) }) } } module.exports = RecentBlocksController