From d548915efc836536e4b961ccabc3a3ca4fb9e60a Mon Sep 17 00:00:00 2001
From: Tom Kirkpatrick <tkp@kirkdesigns.co.uk>
Date: Wed, 4 Jul 2018 20:32:19 +0200
Subject: [PATCH] feat(api): redundant block explorer api backends

Call out to 3 different block explorers to get the current block height
and use the result from whichever responds quickest.

Fix #463
---
 app/api/index.js                | 32 +++++++++++++++++++++++++++-----
 app/reducers/lnd.js             |  4 ++--
 webpack.config.renderer.dev.js  | 10 ++++++++++
 webpack.config.renderer.prod.js |  4 +++-
 4 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/app/api/index.js b/app/api/index.js
index 63b95429..27e1dfd2 100644
--- a/app/api/index.js
+++ b/app/api/index.js
@@ -29,11 +29,33 @@ export function requestTickers(ids) {
 }
 
 export function requestBlockHeight() {
-  const BASE_URL = `${scheme}testnet-api.smartbit.com.au/v1/blockchain/blocks?limit=1`
-  return axios({
-    method: 'get',
-    url: BASE_URL
-  }).then(response => response.data)
+  const sources = [
+    {
+      baseUrl: `${scheme}testnet-api.smartbit.com.au/v1/blockchain/blocks?limit=1`,
+      path: 'blocks[0].height'
+    },
+    {
+      baseUrl: `${scheme}tchain.api.btc.com/v3/block/latest`,
+      path: 'data.height'
+    },
+    {
+      baseUrl: `${scheme}api.blockcypher.com/v1/btc/test3`,
+      path: 'height'
+    }
+  ]
+  const fetchData = (baseUrl, path) => {
+    return axios({
+      method: 'get',
+      timeout: 5000,
+      url: baseUrl
+    })
+      .then(response => path.split('.').reduce((a, b) => a[b], response.data))
+      .catch(() => null)
+  }
+
+  const promises = []
+  sources.forEach(source => promises.push(fetchData(source.baseUrl, source.path)))
+  return Promise.race(promises)
 }
 
 export function requestSuggestedNodes() {
diff --git a/app/reducers/lnd.js b/app/reducers/lnd.js
index e63a8bd6..5ee4595b 100644
--- a/app/reducers/lnd.js
+++ b/app/reducers/lnd.js
@@ -84,8 +84,8 @@ export function receiveBlockHeight(blockHeight) {
 // Fetch current block height
 export const fetchBlockHeight = () => async dispatch => {
   dispatch(getBlockHeight())
-  const blockData = await requestBlockHeight()
-  dispatch(receiveBlockHeight(blockData.blocks[0].height))
+  const blockHeight = await requestBlockHeight()
+  dispatch(receiveBlockHeight(blockHeight))
 }
 
 // ------------------------------------
diff --git a/webpack.config.renderer.dev.js b/webpack.config.renderer.dev.js
index 4a5695ae..c98452c7 100644
--- a/webpack.config.renderer.dev.js
+++ b/webpack.config.renderer.dev.js
@@ -298,6 +298,16 @@ export default merge.smart(baseConfig, {
         target: 'https://testnet-api.smartbit.com.au',
         pathRewrite: { '^/proxy/testnet-api.smartbit.com.au': '' },
         changeOrigin: true
+      },
+      '/proxy/tchain.api.btc.com': {
+        target: 'https://tchain.api.btc.com',
+        pathRewrite: { '^/proxy/tchain.api.btc.com': '' },
+        changeOrigin: true
+      },
+      '/proxy/api.blockcypher.com': {
+        target: 'https://api.blockcypher.com',
+        pathRewrite: { '^/proxy/api.blockcypher.com': '' },
+        changeOrigin: true
       }
     },
     historyApiFallback: {
diff --git a/webpack.config.renderer.prod.js b/webpack.config.renderer.prod.js
index f295db31..baeacb21 100644
--- a/webpack.config.renderer.prod.js
+++ b/webpack.config.renderer.prod.js
@@ -159,7 +159,9 @@ export default merge.smart(baseConfig, {
         "'self'",
         'https://api.coinmarketcap.com',
         'https://zap.jackmallers.com',
-        'https://testnet-api.smartbit.com.au'
+        'https://testnet-api.smartbit.com.au',
+        'https://tchain.api.btc.com',
+        'https://api.blockcypher.com'
       ],
       'script-src': ["'self'"],
       'font-src': [