saveImage host function

src/runtime-js.ts

@@ -101,6 +101,22 @@ export const _rt = {
         const printed = prettyPrint(ast);
         return printed;
     },
+    saveImage: () => {
+        const saved: Record<string, string> = {};
+        for (const [name, ast] of definitions) {
+            const source = prettyPrint({ kind: 'definition', name, body: ast });
+            saved[name] = source;
+       }
+       const content = Object.values(saved).join('\n\n');
+       const blob = new Blob([content], { type: 'text/plain' });
+       const url = URL.createObjectURL(blob);
+       const a = document.createElement('a');
+       a.href = url;
+       a.download = `cg-image-${new Date().toISOString().slice(0, 19).replace(/[T:]/g, '-')}.cg`;
+       a.click();
+       URL.revokeObjectURL(url);
+       return { _tag: 'Ok' };
+    },
     rebind: (name: string, pathOrValue: any, maybeValue?: any) => {
         if (maybeValue === undefined) {
             store[name] = pathOrValue;