Add core physics manuscript: The Computability of Recursive Coherence

venv/lib/python3.12/site-packages/properdocs/utils/cache.py

@@ -0,0 +1,75 @@
+# Copyright (c) 2023 Oleh Prypin <oleh@pryp.in>
+
+from __future__ import annotations
+
+import datetime
+import hashlib
+import logging
+import os
+import random
+import urllib.request
+from typing import Callable
+
+import platformdirs
+
+import properdocs
+
+log = logging.getLogger(__name__)
+
+
+def download_url(url: str) -> bytes:
+    req = urllib.request.Request(
+        url, headers={"User-Agent": f"properdocs/{properdocs.__version__}"}
+    )
+    with urllib.request.urlopen(req) as resp:
+        return resp.read()
+
+
+def download_and_cache_url(
+    url: str,
+    cache_duration: datetime.timedelta,
+    *,
+    download: Callable[[str], bytes] = download_url,
+    comment: bytes = b"# ",
+) -> bytes:
+    """
+    Downloads a file from the URL, stores it under ~/.cache/, and returns its content.
+
+    For tracking the age of the content, a prefix is inserted into the stored file, rather than relying on mtime.
+
+    Args:
+        url: URL to use.
+        download: Callback that will accept the URL and actually perform the download.
+        cache_duration: How long to consider the URL content cached.
+        comment: The appropriate comment prefix for this file format.
+    """
+    directory = os.path.join(platformdirs.user_cache_dir("properdocs"), "properdocs_url_cache")
+    name_hash = hashlib.sha256(url.encode()).hexdigest()[:32]
+    path = os.path.join(directory, name_hash + os.path.splitext(url)[1])
+
+    now = int(datetime.datetime.now(datetime.timezone.utc).timestamp())
+    prefix = b"%s%s downloaded at timestamp " % (comment, url.encode())
+    # Check for cached file and try to return it
+    if os.path.isfile(path):
+        try:
+            with open(path, "rb") as f:
+                line = f.readline()
+                if line.startswith(prefix):
+                    line = line[len(prefix) :]
+                    timestamp = int(line)
+                    if datetime.timedelta(seconds=(now - timestamp)) <= cache_duration:
+                        log.debug(f"Using cached '{path}' for '{url}'")
+                        return f.read()
+        except (OSError, ValueError) as e:
+            log.debug(f"{type(e).__name__}: {e}")
+
+    # Download and cache the file
+    log.debug(f"Downloading '{url}' to '{path}'")
+    content = download(url)
+    os.makedirs(directory, exist_ok=True)
+    temp_filename = f"{path}.{random.randrange(1 << 32):08x}.part"
+    with open(temp_filename, "wb") as f:
+        f.write(b"%s%d\n" % (prefix, now))
+        f.write(content)
+    os.replace(temp_filename, path)
+    return content