Sort gallery media by capture date instead of file name

photologue/models.py

@@ -4,7 +4,6 @@
 import logging
 import os
 import unicodedata
-from datetime import datetime
 from functools import partial
 from importlib import import_module
 from inspect import isclass
@@ -39,6 +38,19 @@ LATEST_LIMIT = getattr(settings, "PHOTOLOGUE_GALLERY_LATEST_LIMIT", None)
 # max_length setting for the ImageModel ImageField
 IMAGE_FIELD_MAX_LENGTH = getattr(settings, "PHOTOLOGUE_IMAGE_FIELD_MAX_LENGTH", 100)
 
+# Where a capture date comes from, from the most to the least trustworthy. An
+# empty value means the date was never determined.
+DATE_FROM_EXIF = "exif"
+DATE_FROM_VIDEO = "video"
+DATE_FROM_FILE = "file"
+DATE_MANUAL = "manual"
+DATE_SOURCE_CHOICES = (
+    (DATE_FROM_EXIF, _("EXIF metadata")),
+    (DATE_FROM_VIDEO, _("video metadata")),
+    (DATE_FROM_FILE, _("file date at upload")),
+    (DATE_MANUAL, _("set by hand")),
+)
+
 # Modify image file buffer size.
 ImageFile.MAXBLOCK = getattr(settings, "PHOTOLOGUE_MAXBLOCK", 256 * 2**10)
 
@@ -265,6 +277,20 @@ class MediaModel(models.Model):
     )
     thumbnail_width = models.PositiveIntegerField(editable=False, null=True)
     thumbnail_height = models.PositiveIntegerField(editable=False, null=True)
+    date_taken = models.DateTimeField(
+        _("date taken"),
+        null=True,
+        blank=True,
+        help_text=_("Date the media was captured; read from its metadata."),
+    )
+    date_source = models.CharField(
+        _("date source"),
+        max_length=10,
+        blank=True,
+        editable=False,
+        choices=DATE_SOURCE_CHOICES,
+        help_text=_("Where the capture date comes from."),
+    )
 
     is_video = False
 
@@ -288,9 +314,32 @@ class MediaModel(models.Model):
     def get_download_url(self):
         raise NotImplementedError
 
+    @property
+    def date_is_approximate(self):
+        """True when the date was deduced rather than read from the capture itself."""
+        return self.date_source == DATE_FROM_FILE
+
+    def set_capture_date(self, value, source):
+        """Record a capture date read from the file, and where it comes from."""
+        self.date_taken = value
+        self.date_source = source
+        self._date_read_from_file = True
+
     def save(self, *args, **kwargs):
         if not self.slug:
             self.slug = slugify(self.title)
+        if self.pk and not getattr(self, "_date_read_from_file", False):
+            # A date changed by anything but our own readers was set by a human,
+            # and must survive a later re-read of the metadata.
+            stored = (
+                type(self)
+                .objects.filter(pk=self.pk)
+                .values_list("date_taken", flat=True)
+                .first()
+            )
+            if stored != self.date_taken:
+                self.date_source = DATE_MANUAL
+        self._date_read_from_file = False
         super().save(*args, **kwargs)
 
 
@@ -302,12 +351,6 @@ class Photo(MediaModel):
         width_field="thumbnail_width",
         height_field="thumbnail_height",
     )
-    date_taken = models.DateTimeField(
-        _("date taken"),
-        null=True,
-        blank=True,
-        help_text=_("Date image was taken; is obtained from the image EXIF data."),
-    )
     view_count = models.PositiveIntegerField(_("view count"), default=0, editable=False)
     crop_from = models.CharField(
         _("crop from"),
@@ -577,21 +620,15 @@ class Photo(MediaModel):
         if (self.date_taken is None or image_has_changed) and self.image:
             # Attempt to get the date the photo was taken from the EXIF data.
             try:
+                from .utils import capture_date_from_exif
+
                 exif_date = self.exif(self.image.file).get(
                     "EXIF DateTimeOriginal", None
                 )
                 if exif_date is not None:
-                    d, t = exif_date.values.split()
-                    year, month, day = d.split(":")
-                    hour, minute, second = t.split(":")
-                    self.date_taken = datetime(
-                        int(year),
-                        int(month),
-                        int(day),
-                        int(hour),
-                        int(minute),
-                        int(second),
-                    )
+                    taken = capture_date_from_exif(exif_date.values)
+                    if taken is not None:
+                        self.set_capture_date(taken, DATE_FROM_EXIF)
             except Exception:
                 logger.error("Failed to read EXIF DateTimeOriginal", exc_info=True)
         # If crop_from property has been changed on existing image,