Archive snapshots of websites locally (#672)

* Add basic HTML snapshots

* Implement asset list

* Add snapshot creation tests

* Add deletion tests

* Show file size

* Remove snapshots

* Create new snapshots

* Switch to single-file

* CSS tweak

* Remove auto refresh

* Show delete link when there is no file yet

* Add current date to display name

* Add flag for snapshot support

* Add option for disabling automatic snapshots

* Make snapshots sharable

* Document image variants

* Update README.md

* Add migrations

* Fix tests

bookmarks/services/singlefile.py

@@ -0,0 +1,33 @@
+import gzip
+import os
+import shutil
+import subprocess
+
+from django.conf import settings
+
+
+class SingeFileError(Exception):
+    pass
+
+
+def create_snapshot(url: str, filepath: str):
+    singlefile_path = settings.LD_SINGLEFILE_PATH
+    singlefile_options = settings.LD_SINGLEFILE_OPTIONS
+    temp_filepath = filepath + ".tmp"
+
+    try:
+        command = f"{singlefile_path} '{url}' {singlefile_options} {temp_filepath}"
+        subprocess.run(command, check=True, shell=True)
+
+        # single-file doesn't return exit codes apparently, so check if the file was created
+        if not os.path.exists(temp_filepath):
+            raise SingeFileError("Failed to create snapshot")
+
+        with open(temp_filepath, "rb") as raw_file, gzip.open(
+            filepath, "wb"
+        ) as gz_file:
+            shutil.copyfileobj(raw_file, gz_file)
+
+        os.remove(temp_filepath)
+    except subprocess.CalledProcessError as error:
+        raise SingeFileError(f"Failed to create snapshot: {error.stderr}")