3 files changed, 80 insertions, 0 deletions
diff --git a/hazwaz/__init__.py b/hazwaz/__init__.py
index 883ffe2..e328bee 100644
--- a/hazwaz/__init__.py
+++ b/hazwaz/__init__.py
@@ -1 +1,2 @@
+from . import mixins  # noqa: F401
 from .command import Command, MainCommand  # noqa: F401
diff --git a/hazwaz/mixins.py b/hazwaz/mixins.py
new file mode 100644
index 0000000..5720a38
--- /dev/null
+++ b/hazwaz/mixins.py
@@ -0,0 +1,42 @@
+import logging
+import os
+import subprocess
+
+
+class ExternalEditorMixin:
+    """
+    Add facilities to open a file in an external editor to a Command.
+    """
+    editors = [
+        (os.environ.get("EDITOR"), "$EDITOR (set to {editor})"),
+        ("sensible-editor", "sensible-editor"),
+        ("vi", "vi"),
+    ]
+
+    def edit_file_in_external_editor(self, filepath):
+        """
+        Open filepath in an external editor and wait for it to be closed.
+
+        Return whether opening the file was succesful.
+        This tries to cycle through all editors listed in self.editors.
+        """
+        for editor, e_name in self.editors:
+            if editor:
+                try:
+                    res = subprocess.call([editor, filepath])
+                except FileNotFoundError as e:
+                    if editor in str(e):
+                        logging.info('Could not open file {} with {}'.format(
+                            filepath, e_name
+                        ))
+                    else:
+                        logging.warning("Could not open file {}".format(
+                            filepath
+                        ))
+                        return False
+                else:
+                    if res == 0:
+                        return True
+                    else:
+                        return False
+        return False
diff --git a/tests/test_mixins.py b/tests/test_mixins.py
new file mode 100644
index 0000000..1e2f91d
--- /dev/null
+++ b/tests/test_mixins.py
@@ -0,0 +1,37 @@
+import unittest
+
+import hazwaz
+
+
+class testEditorMixin(unittest.TestCase):
+    def test_open_with_cat_existing_file(self):
+        subcmd = hazwaz.mixins.ExternalEditorMixin()
+        subcmd.editors = [("cat", "cat")]
+        # TODO: suppress this output in the tests (we can't use
+        # contextlib.redirect_stdout because that doesn't redirect the
+        # stdout used by subprocess.
+        res = subcmd.edit_file_in_external_editor("/bin/fgrep")
+        self.assertTrue(res)
+
+    def test_open_with_cat_missing_file(self):
+        subcmd = hazwaz.mixins.ExternalEditorMixin()
+        subcmd.editors = [("cat", "cat")]
+        # TODO: suppress this output in the tests (we can't use
+        # contextlib.redirect_stderr because that doesn't redirect the
+        # stderr used by subprocess.
+        res = subcmd.edit_file_in_external_editor("no_such_file")
+        self.assertFalse(res)
+
+    def test_open_with_non_existing_editor(self):
+        subcmd = hazwaz.mixins.ExternalEditorMixin()
+        subcmd.editors = [("no_such_command", "no_such_command")]
+        with self.assertLogs() as cm:
+            subcmd.edit_file_in_external_editor("no_such_file")
+        self.assertIn(
+            "Could not open file no_such_file with no_such_command",
+            cm.output[0]
+        )
+
+
+if __name__ == '__main__':
+    unittest.main()