implement 'mtime' post-processor (#332)

This can set a file's modification time according to a UNIX timestamp
or a datetime object from its metadata.

docs/configuration.rst

@@ -1290,6 +1290,23 @@ Description Custom format string to build content of metadata files.
 =========== =====
 
 
+mtime
+-----
+
+Set file modification time according to its metadata
+
+mtime.key
+---------
+=========== =====
+Type        ``string``
+Default     ``"date"``
+Description Name of the metadata field whose value should be used.
+
+            This value must either be a UNIX timestamp or a
+            |datetime|_ object.
+=========== =====
+
+
 ugoira
 ------
 
@@ -1648,6 +1665,7 @@ Description An object with the ``name`` of a post-processor and its options.
 .. |verify| replace:: ``verify``
 .. |mature_content| replace:: ``mature_content``
 .. |webbrowser.open()| replace:: ``webbrowser.open()``
+.. |datetime| replace:: ``datetime``
 .. |datetime.max| replace:: ``datetime.max``
 .. |Path| replace:: ``Path``
 .. |Last-Modified| replace:: ``Last-Modified``
@@ -1673,6 +1691,7 @@ Description An object with the ``name`` of a post-processor and its options.
 .. _strptime:          https://docs.python.org/3/library/datetime.html#strftime-strptime-behavior
 .. _mature_content:    https://www.deviantart.com/developers/http/v1/20160316/object/deviation
 .. _webbrowser.open(): https://docs.python.org/3/library/webbrowser.html
+.. _datetime:          https://docs.python.org/3/library/datetime.html#datetime-objects
 .. _datetime.max:      https://docs.python.org/3/library/datetime.html#datetime.datetime.max
 .. _Authentication:    https://github.com/mikf/gallery-dl#5authentication
 .. _youtube-dl:        https://github.com/ytdl-org/youtube-dl

gallery_dl/downloader/http.py

@@ -160,9 +160,7 @@ class HttpDownloader(DownloaderBase):
         if adj_ext:
             pathfmt.set_extension(adj_ext)
         if self.mtime:
-            filetime = response.headers.get("Last-Modified")
-            if filetime:
-                pathfmt.keywords["_filetime"] = filetime
+            pathfmt.keywords["_mtime"] = response.headers.get("Last-Modified")
         return True
 
     def receive(self, response, file):

gallery_dl/option.py

@@ -322,6 +322,12 @@ def build_parser():
         action="append_const", const={"name": "metadata", "mode": "tags"},
         help="Write image tags to separate text files",
     )
+    postprocessor.add_argument(
+        "--mtime-from-date",
+        dest="postprocessors",
+        action="append_const", const={"name": "mtime"},
+        help="Set file modification times according to 'date' metadata",
+    )
 
     parser.add_argument(
         "urls",

gallery_dl/postprocessor/__init__.py

@@ -15,6 +15,7 @@ modules = [
     "classify",
     "exec",
     "metadata",
+    "mtime",
     "ugoira",
     "zip",
 ]

gallery_dl/postprocessor/mtime.py

@@ -0,0 +1,27 @@
+# -*- coding: utf-8 -*-
+
+# Copyright 2019 Mike Fährmann
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+
+"""Use metadata as file modification time"""
+
+from .common import PostProcessor
+from ..text import parse_int
+
+
+class MtimePP(PostProcessor):
+
+    def __init__(self, pathfmt, options):
+        PostProcessor.__init__(self)
+        self.key = options.get("key", "date")
+
+    def run(self, pathfmt):
+        mtime = pathfmt.keywords.get(self.key)
+        ts = getattr(mtime, "timestamp", None)
+        pathfmt.keywords["_mtime"] = ts() if ts else parse_int(mtime)
+
+
+__postprocessor__ = MtimePP

gallery_dl/util.py

@@ -20,8 +20,8 @@ import sqlite3
 import datetime
 import operator
 import itertools
-import email.utils
 import urllib.parse
+from email.utils import mktime_tz, parsedate_tz
 from . import text, exception
 
 
@@ -639,15 +639,16 @@ class PathFormat():
                 shutil.copyfile(self.temppath, self.realpath)
                 os.unlink(self.temppath)
 
-        if "_filetime" in self.keywords:
-            # try to set file times
-            try:
-                filetime = email.utils.mktime_tz(email.utils.parsedate_tz(
-                    self.keywords["_filetime"]))
-                if filetime:
-                    os.utime(self.realpath, (time.time(), filetime))
-            except Exception:
-                pass
+        if "_mtime" in self.keywords:
+            # set file modification time
+            mtime = self.keywords["_mtime"]
+            if mtime:
+                try:
+                    if isinstance(mtime, str):
+                        mtime = mktime_tz(parsedate_tz(mtime))
+                    os.utime(self.realpath, (time.time(), mtime))
+                except Exception:
+                    pass
 
     @staticmethod
     def adjust_path(path):