Add new fields to page to use it better

vrobbler/apps/books/models.py

@@ -1,4 +1,5 @@
 import logging
+from datetime import timedelta
 from uuid import uuid4
 
 import requests
@@ -182,9 +183,11 @@ class Book(LongPlayScrobblableMixin):
 
 
 class Page(TimeStampedModel):
+    user = models.ForeignKey(User, on_delete=models.CASCADE)
     book = models.ForeignKey(Book, on_delete=models.CASCADE)
     number = models.IntegerField()
     start_time = models.DateTimeField(**BNULL)
+    end_time = models.DateTimeField(**BNULL)
     duration_seconds = models.IntegerField(**BNULL)
 
     class Meta:
@@ -195,3 +198,74 @@ class Page(TimeStampedModel):
 
     def __str__(self):
         return f"Page {self.number} of {self.book.pages} in {self.book.title}"
+
+    def save(self, *args, **kwargs):
+        if not self.end_time and self.duration_seconds:
+            self._set_end_time()
+
+        return super(Page, self).save(*args, **kwargs)
+
+    @property
+    def next(self):
+        page = self.book.page_set.filter(number=self.number + 1).first()
+        if not page:
+            page = (
+                self.book.page_set.filter(created__gt=self.created)
+                .order_by("created")
+                .first()
+            )
+        return page
+
+    @property
+    def previous(self):
+        page = self.book.page_set.filter(number=self.number - 1).first()
+        if not page:
+            page = (
+                self.book.page_set.filter(created__lt=self.created)
+                .order_by("-created")
+                .first()
+            )
+        return page
+
+    @property
+    def seconds_to_next_page(self) -> int:
+        seconds = 0
+        if not self.end_time:
+            self._set_end_time()
+        if self.next:
+            seconds = (self.next.start_time - self.end_time).seconds
+        return seconds
+
+    @property
+    def is_scrobblable(self) -> bool:
+        """A page defines the start of a scrobble if the seconds to next page
+        are greater than an hour, or 3600 seconds, and it's not a single page,
+        so the next seconds to next_page is less than an hour as well.
+
+        As a special case, the first recorded page is a scrobble, so we establish
+        when the book was started.
+
+        """
+        is_scrobblable = False
+        over_an_hour_since_last_page = False
+        if not self.previous:
+            is_scrobblable = True
+
+        if self.previous:
+            over_an_hour_since_last_page = (
+                self.previous.seconds_to_next_page >= 3600
+            )
+        blip = self.seconds_to_next_page >= 3600
+
+        if over_an_hour_since_last_page and not blip:
+            is_scrobblable = True
+        return is_scrobblable
+
+    def _set_end_time(self) -> None:
+        if self.end_time:
+            return self.end_time
+
+        self.end_time = self.start_time + timedelta(
+            seconds=self.duration_seconds
+        )
+        self.save(update_fields=["end_time"])