fix Last-Modified bc apparently that was broken

1 files changed, 19 insertions, 16 deletions

diff --git a/repos/base.py b/repos/base.py
index 220a30f..1bd4ae3 100644
--- a/repos/base.py
+++ b/repos/base.py
@@ -1,9 +1,7 @@
 from dataclasses import dataclass, asdict as dataclass_asdict
-import datetime
 from functools import total_ordering
 import gzip
 import json
-import os
 from pathlib import Path
 import re
 from typing import Any, Callable, Mapping
@@ -73,30 +71,35 @@ class Repository:
 
     def get_versions(self) -> Mapping[str, Version]:
         self._cache_dir().mkdir(parents=True, exist_ok=True)
+        headers = dict()
+
         downloaded_file = self._cache_file('downloaded')
-        if downloaded_file.exists():
-            mtime = downloaded_file.stat().st_mtime
-        else:
-            mtime = 0
-        mtime = datetime.datetime.fromtimestamp(mtime, datetime.timezone.utc)
-        mtime = mtime.strftime(HTTP_DATE)
 
-        parsed_file = self._cache_file('parsed.json.gz')
+        mtime_file = self._cache_file('last-modified')
+        if mtime_file.exists():
+            mtime = mtime_file.read_text()
+            headers['If-Modified-Since'] = mtime
 
-        response = requests.get(self.index_url, headers={
-            'If-Modified-Since': mtime,
-        }, stream=True)
+        etag_file = self._cache_file('etag')
+        if etag_file.exists():
+            etag = etag_file.read_text()
+            headers['If-None-Match'] = etag
+
+        response = requests.get(self.index_url, headers=headers, stream=True)
         if response.status_code != requests.codes.not_modified:
             response.raise_for_status()
             print('Re-downloading', self._full_name())
-            set_mtime = response.headers.get('Last-Modified', '')
             with downloaded_file.open('wb') as f:
                 for chunk in response.iter_content(chunk_size=256):
                     f.write(chunk)
-            if len(set_mtime) > 0:
-                set_mtime = datetime.datetime.strptime(set_mtime, HTTP_DATE)
-                os.utime(downloaded_file, (datetime.datetime.now().timestamp(), set_mtime.timestamp()))
+            if 'Last-Modified' in response.headers:
+                set_mtime = response.headers['Last-Modified']
+                mtime_file.write_text(set_mtime)
+            if 'ETag' in response.headers:
+                set_etag = response.headers['ETag']
+                etag_file.write_text(set_etag)
 
+        parsed_file = self._cache_file('parsed.json.gz')
         if response.status_code != requests.codes.not_modified or not parsed_file.exists():
             parsed_data = self.parse(downloaded_file)
             with gzip.open(parsed_file, 'wt') as f: