add blockcypher [WIP]

lib/plugins/zero-conf/blockcypher/blockcypher.js

@@ -0,0 +1,28 @@
+const qs = require('querystring')
+const axios = require('axios')
+const _ = require('lodash/fp')
+
+module.exports = {authorize}
+
+function authorize (account, toAddress, cryptoAtoms, cryptoCode) {
+  return Promise.resolve()
+  .then(() => {
+    if (cryptoCode !== 'BTC') throw new Error('Unsupported crypto: ' + cryptoCode)
+
+    const query = qs.stringify({
+      token: account.token,
+      includeConfidence: true,
+      confidence: account.confidence
+    })
+
+    const url = `https://api.blockcypher.com/v1/btc/main/addrs/${toAddress}?${query}`
+
+    return axios.get(url)
+    .then(r => {
+      const data = r.data
+      const authorizedValue = _.sumBy('value', data.txrefs)
+
+      return cryptoAtoms.lte(authorizedValue)
+    })
+  })
+}