Add APP__PROXY_DOMAIN environment variable (#23)

* fix(config.js): add `APP__PROXY_DOMAIN` environment variable

You can change the `proxyDomain` value through environment variables without directly modifying the source code.

* docs(readme.md): add `APP__PROXY_DOMAIN` environment variable description

* fix(Dockerfile): add environment variables

Changed so that setting information can be changed using environment variables during build.

* docs(readme.md): update `APP__PROXY_DOMAIN` environment variable description

* Revert "fix(Dockerfile): add environment variables"

This reverts commit 9250088.

config.js

@@ -1,6 +1,7 @@
 const MATCH_EVERYTHING_STRING = '.*';
 const env = process.env.APP__ENV_NAME || "local";
 const isLocal = env === "local" || env === "test";
+const proxyDomain = process.env.APP__PROXY_DOMAIN || '';
 const strippedPath = process.env.APP__STRIPPED_PATH || '';
 const hostsWhitelistRegex = (() => {
     try {
@@ -12,7 +13,8 @@ const hostsWhitelistRegex = (() => {
 })();
 
 console.log("Environment variables:");
-console.log(`APP__STRIPPED_PATH=${strippedPath} (path added to original host in analytics scripts)`);
+console.log(`APP__PROXY_DOMAIN=${proxyDomain} (path added to original host replace proxy host`);
+console.log(`APP__STRIPPED_PATH=${strippedPath} (proxy domain added to replace original host in analytics scripts)`);
 console.log(`APP__ENV_NAME=${env} (should not be local nor test in production)`);
 console.log(`APP__HOSTS_WHITELIST_REGEX=${hostsWhitelistRegex}${hostsWhitelistRegex.toString() === `/${MATCH_EVERYTHING_STRING}/` ? ' (YAY!! Anyone can use your proxy!)' : ''}`);
 
@@ -21,9 +23,9 @@ export default {
     httpPort: process.env.PORT || 80,
     strippedPath,
     hostsWhitelistRegex: hostsWhitelistRegex,
-    proxyDomain: "",          // Domain to proxy calls through. Leave it empty to use the requested domain as a proxy domain
-    proxy: {                  // Proxy configuration is here
-        domains: [            // These domains are replaced in any proxied response (including scripts, URLs and redirects)
+    proxyDomain,        // Domain to proxy calls through. Leave it empty to use the requested domain as a proxy domain
+    proxy: {            // Proxy configuration is here
+        domains: [      // These domains are replaced in any proxied response (including scripts, URLs and redirects)
             "adservice.google.com",
             "www.google-analytics.com",
             "analytics.google.com",

readme.md

@@ -83,6 +83,13 @@ docker run -p 80:80 zitros/analytics-saviour
 Available environment variables:
 
 ```bash
+APP__PROXY_DOMAIN=(empty string)
+# The domain name used as a proxy for analytics scripts. 
+#
+# When set, the traffic will be proxied via this domain. 
+# When not set, the current request domain is used as a proxy domain
+# proxy URL requested by the browser is expected to be protocol://$APP__PROXY_DOMAIN$APP__STRIPPED_PATH/*(masked-url)*.
+
 APP__STRIPPED_PATH=/gtm-proxy
 # A prefix which has been stripped in the request path reaching analytics-saviour.
 # If your ingress/router/etc strips the prefix you are required to set this variable.