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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
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