New constants/config merge system

src/lib/constants.js

@@ -1,7 +1,20 @@
-module.exports = {
-	image_cache_control: `public, max-age=${7*24*60*60}`,
-	resource_cache_time: 30*60*1000,
+/*
+	Welcome to the constants file!
+	Copy a key and provide a new value in /config.js to override the value here.
+	Please read the comments above every section!
+*/
 
+let constants = {
+	// Things that server owners _should_ change!
+	website_origin: "http://localhost:10407",
+
+	// Things that server owners _could_ change if they want to.
+	caching: {
+		image_cache_control: `public, max-age=${7*24*60*60}`,
+		resource_cache_time: 30*60*1000
+	},
+
+	// Instagram uses this stuff. This shouldn't be changed, except to fix a bug that hasn't yet been fixed upstream.
 	external: {
 		timeline_query_hash: "e769aa130647d2354c40ea6a439bfc08",
 		shortcode_query_hash: "2b0673e0dc4580674a88d426fe00ea90",
@@ -10,6 +23,7 @@ module.exports = {
 		shortcode_regex: "[\\w-]+"
 	},
 
+	// My code uses this stuff. Server owners have no reason to change it.
 	symbols: {
 		NO_MORE_PAGES: Symbol("NO_MORE_PAGES"),
 		TYPE_IMAGE: Symbol("TYPE_IMAGE"),
@@ -21,3 +35,9 @@ module.exports = {
 		NO_SHARED_DATA: Symbol("NO_SHARED_DATA")
 	}
 }
+
+// Override values from config and export the result
+const md = require("mixin-deep")
+const config = require("../../config")
+constants = md(constants, config)
+module.exports = constants