Refactor the kittens framework

Make it possible to perform arbitrary actions with the kittens output
and also allow running kittens from standalone python files.

kittens/runner.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+# License: GPL v3 Copyright: 2018, Kovid Goyal <kovid at kovidgoyal.net>
+
+
+import importlib
+import os
+import sys
+from functools import partial
+
+
+def import_kitten_main_module(config_dir, kitten):
+    if kitten.endswith('.py'):
+        path = os.path.expanduser(kitten)
+        if not os.path.isabs(path):
+            path = os.path.join(config_dir, path)
+        path = os.path.abspath(path)
+        if os.path.dirname(path):
+            sys.path.insert(0, os.path.dirname(path))
+        with open(path) as f:
+            src = f.read()
+        code = compile(src, path, 'exec')
+        g = {'__name__': 'kitten'}
+        exec(code, g)
+        return {'start': g['main'], 'end': g['handle_result']}
+    else:
+        m = importlib.import_module('kittens.{}.main'.format(kitten))
+        return {'start': m.main, 'end': m.handle_result}
+
+
+def create_kitten_handler(kitten, orig_args):
+    from kitty.constants import config_dir
+    m = import_kitten_main_module(config_dir, kitten)
+    return partial(m['end'], [kitten] + orig_args)
+
+
+def launch(args):
+    config_dir, kitten = args[:2]
+    del args[:2]
+    args = [kitten] + args
+    os.environ['KITTY_CONFIG_DIRECTORY'] = config_dir
+    from kittens.tui.operations import clear_screen, reset_mode
+    m = import_kitten_main_module(config_dir, kitten)
+    result = m['start'](args)
+    print(reset_mode('ALTERNATE_SCREEN') + clear_screen(), end='')
+    if result is not None:
+        import json
+        print('OK:', json.dumps(result))
+
+
+def main():
+    try:
+        args = sys.argv[1:]
+        launch(args)
+    except Exception:
+        print('Unhandled exception running kitten:')
+        import traceback
+        traceback.print_exc()
+        input('Press Enter to quit...')