prepare from trade generation

modules/trade-generator.js

@@ -1,8 +1,28 @@
 'use strict';
 
 window.Trade = (function () {
-  const defineTradeCenters = () => {
+  const defineCenters = () => {
     const {cells} = pack;
   };
-  return {defineTradeCenters};
+
+  const exportGoods = () => {
+    for (const burg of pack.burgs) {
+      if (!burg.i || burg.removed) continue;
+      const {population, production: resourcePool} = burg;
+      const localUsage = Math.ceil(population);
+
+      const surplus = {};
+      for (const resourceId in resourcePool) {
+        const production = resourcePool[resourceId];
+        const extraProduction = production - localUsage;
+        if (extraProduction > 0) surplus[resourceId] = extraProduction;
+      }
+
+      burg.export = surplus;
+    }
+  };
+
+  const importGoods = () => {};
+
+  return {defineCenters, exportGoods, importGoods};
 })();