Derive gas price estimate from previous transactions

Return the 50th percentile lowest gas price of the previous 20 blocks.

app/scripts/controllers/blacklist.js

@@ -57,3 +57,4 @@ class BlacklistController {
 }
 
 module.exports = BlacklistController
+

app/scripts/controllers/transactions.js

@@ -32,6 +32,7 @@ module.exports = class TransactionController extends EventEmitter {
     this.provider = opts.provider
     this.blockTracker = opts.blockTracker
     this.signEthTx = opts.signTransaction
+    this.getGasPrice = opts.getGasPrice
 
     this.memStore = new ObservableStore({})
     this.query = new EthQuery(this.provider)
@@ -179,7 +180,7 @@ module.exports = class TransactionController extends EventEmitter {
     // ensure value
     txMeta.gasPriceSpecified = Boolean(txParams.gasPrice)
     txMeta.nonceSpecified = Boolean(txParams.nonce)
-    const gasPrice = txParams.gasPrice || await this.query.gasPrice()
+    const gasPrice = txParams.gasPrice || this.getGasPrice()
     txParams.gasPrice = ethUtil.addHexPrefix(gasPrice.toString(16))
     txParams.value = txParams.value || '0x0'
     // set gasLimit

app/scripts/metamask-controller.js

@@ -35,13 +35,15 @@ const accountImporter = require('./account-import-strategies')
 const getBuyEthUrl = require('./lib/buy-eth-url')
 const Mutex = require('await-semaphore').Mutex
 const version = require('../manifest.json').version
+const BN = require('ethereumjs-util').BN
+const GWEI_BN = new BN('1000000000')
+const percentile = require('percentile')
 
 module.exports = class MetamaskController extends EventEmitter {
 
   constructor (opts) {
     super()
 
-
     this.sendUpdate = debounce(this.privateSendUpdate.bind(this), 200)
 
     this.opts = opts
@@ -139,6 +141,7 @@ module.exports = class MetamaskController extends EventEmitter {
       provider: this.provider,
       blockTracker: this.blockTracker,
       ethQuery: this.ethQuery,
+      getGasPrice: this.getGasPrice.bind(this),
     })
     this.txController.on('newUnapprovedTx', opts.showUnapprovedTx.bind(opts))
 
@@ -484,6 +487,22 @@ module.exports = class MetamaskController extends EventEmitter {
     this.emit('update', this.getState())
   }
 
+  getGasPrice () {
+    const { recentBlocksController } = this
+    console.dir(recentBlocksController)
+    const { recentBlocks } = recentBlocksController.store.getState()
+    console.dir(recentBlocks)
+    const lowestPrices = recentBlocks.map((block) => {
+      return block.transactions
+      .sort((a, b) => {
+        return a.gt(b) ? 1 : -1
+      })[0]
+    })
+    .map(number => number.div(GWEI_BN).toNumber())
+    console.dir({ lowestPrices })
+    return percentile(50, lowestPrices)
+  }
+
   //
   // Vault Management
   //

package.json

@@ -119,6 +119,7 @@
     "obj-multiplex": "^1.0.0",
     "obs-store": "^3.0.0",
     "once": "^1.3.3",
+    "percentile": "^1.2.0",
     "ping-pong-stream": "^1.0.0",
     "pojo-migrator": "^2.1.0",
     "polyfill-crypto.getrandomvalues": "^1.0.0",