move the main decision tree to __main__

url2markdown/__main__.py

@@ -5,12 +5,22 @@ from url2markdown.file import write_to_file
 from url2markdown.header import Header
 
 
-def main():
-    args = cli()
-    article = downloader(args.URL)
-    header = Header(article, args.topics)
+def main(url, topics):
+    article = downloader(url)
+    header = Header(article, topics)
     write_to_file(article, header.build_header())
 
 
 if __name__ == "__main__":
-    main()
+    args = cli()
+    if args.url:
+        main(args.url, args.topics)
+    if args.file:
+        with args.file as input_file:
+            for line in input_file:
+                try:
+                    url, topics = line.split(' ')
+                except ValueError:
+                    url = line
+                    topics = []
+                main(url, topics)