refactor(proxy): improve proxy factory implementation with lazy loading (#97)

* refactor(proxy): improve proxy factory implementation with lazy loading

* refactor(proxy): rename proxy factory variables for clarity

* chore(format): run code formatter

Author: Vincentdevreede

lib/proxy-factory.js

@@ -1,29 +1,37 @@
 'use strict'
 
-const fastProxy = require('fast-proxy-lite')
+module.exports = (() => {
+  let fastProxyLite, httpLambdaProxy, fastProxyLegacy
 
-module.exports = ({ proxyType, opts, route }) => {
-  let proxy
+  return ({ proxyType, opts, route }) => {
+    const base = opts.targetOverride || route.target
+    const config = route.proxyConfig || {}
 
-  if (proxyType === 'http') {
-    proxy = fastProxy({
-      base: opts.targetOverride || route.target,
-      ...route.proxyConfig
-    }).proxy
-  } else if (proxyType === 'lambda') {
-    proxy = require('http-lambda-proxy')({
-      target: opts.targetOverride || route.target,
-      region: 'eu-central-1',
-      ...route.proxyConfig
-    })
-  } else if (proxyType === 'http-legacy') {
-    proxy = require('fast-proxy')({
-      base: opts.targetOverride || route.target,
-      ...route.proxyConfig
-    }).proxy
-  } else {
-    throw new Error(`Unsupported proxy type: ${proxyType}!`)
-  }
+    switch (proxyType) {
+      case 'http':
+        fastProxyLite = fastProxyLite || require('fast-proxy-lite')
+        return fastProxyLite({
+          base,
+          ...config
+        }).proxy
+
+      case 'lambda':
+        httpLambdaProxy = httpLambdaProxy || require('http-lambda-proxy')
+        return httpLambdaProxy({
+          target: base,
+          region: 'eu-central-1',
+          ...config
+        })
 
-  return proxy
-}
+      case 'http-legacy':
+        fastProxyLegacy = fastProxyLegacy || require('fast-proxy')
+        return fastProxyLegacy({
+          base,
+          ...config
+        }).proxy
+
+      default:
+        throw new Error(`Unsupported proxy type: ${proxyType}!`)
+    }
+  }
+})()