add last_read_date column

based on the metadata file modify time

action.py

@@ -4,8 +4,10 @@
 from functools import partial
 import io
 import json
+import os
 import re
 import sys
+import time
 from zoneinfo import ZoneInfo
 
 from PyQt5.Qt import QUrl  # pylint: disable=no-name-in-module
@@ -273,11 +275,11 @@ def get_sidecar(self, device, path):
                 return None
 
             debug_print('parsing {}'.format(path))
-            parsed_contents = self.parse_sidecar_lua(decoded_contents)
+            parsed_contents = self.parse_sidecar_lua(decoded_contents, path)
 
         return parsed_contents
 
-    def parse_sidecar_lua(self, sidecar_lua):
+    def parse_sidecar_lua(self, sidecar_lua, path):
         """Parses a sidecar Lua file into a Python dict
 
         :param sidecar_lua: the contents of a sidecar Lua as a str
@@ -311,6 +313,15 @@ def parse_sidecar_lua(self, sidecar_lua):
                     'last_bookmark': max(bookmark_dates),
                 }
 
+        if os.path.exists(path):
+            modify_time = os.path.getmtime(path)
+            last_read = time.strftime('%Y-%m-%d %H:%M:%S',
+                                      time.localtime(modify_time))
+            if 'calculated' not in decoded_lua.keys():
+                decoded_lua['calculated'] = {}
+
+            decoded_lua['calculated']['last_read_date'] = last_read
+
         return decoded_lua
 
     def update_metadata(self, uuid, keys_values_to_update):

config.py

@@ -48,6 +48,13 @@
                'stopped reading at.',
     'type': 'text',
     'sidecar_property': ['last_xpointer'],
+}, {
+    'name': 'column_last_read_date',
+    'label': 'Last read date column:',
+    'tooltip': 'A “Date” column to store the date on which the book was last\n'
+               'read. (based on the modify date of the KOReader metadata file)',
+    'type': 'datetime',
+    'sidecar_property': ['calculated', 'last_read_date']
 }, {
     'name': 'column_rating',
     'label': 'Rating column:',