Add, test date filter regex and date parsing to get natural date range

src/search_filter/date_filter.py

@@ -1,8 +1,21 @@
 # Standard Packages
 import re
+from datetime import timedelta, datetime
+from dateutil.relativedelta import relativedelta, MO
+from math import inf
 
 # External Packages
 import torch
+import dateparser as dtparse
+
+
+# Date Range Filter Regexes
+# Example filter queries:
+#   - dt>=yesterday dt<"tomorrow"
+#   - dt>="last week"
+#   - dt:"next year"
+date_regex = r'(?:dt([:><=]{1,2})\"?([\w\-\/]+))?\"?'
+date_range_regex=f'.*?\s+{date_regex}\s*{date_regex}.*?'
 
 
 def date_filter(query, entries, embeddings):
@@ -30,4 +43,44 @@ def date_filter(query, entries, embeddings):
         del entries[id]
         embeddings = torch.cat((embeddings[:id], embeddings[id+1:]))
 
-    return query, entries, embeddings
+    return query, entries, embeddings
+
+def parse(date_str, relative_base=None):
+    "Parse date string passed in date filter of query to datetime object"
+    # clean date string to handle future date parsing by date parser
+    clean_date_str = re.sub(r'later|from now|from today', '', date_str)
+
+    # parse date passed in query date filter
+    parsed_date = dtparse.parse(
+        clean_date_str,
+        settings= {
+            'RELATIVE_BASE': relative_base or datetime.now(),
+            'PREFER_DAY_OF_MONTH': 'first',
+            'PREFER_DATES_FROM': 'future'
+        })
+
+    if parsed_date is None:
+        return None
+
+    return date_to_daterange(parsed_date, date_str)
+
+
+def date_to_daterange(parsed_date, date_str):
+    "Convert parsed date to date ranges at natural granularity (day, week, month or year)"
+
+    start_of_day = parsed_date.replace(hour=0, minute=0, second=0, microsecond=0)
+
+    if 'year' in date_str:
+        return (datetime(parsed_date.year, 1, 1, 0, 0, 0), datetime(parsed_date.year+1, 1, 1, 0, 0, 0))
+    if 'month' in date_str:
+        start_of_month = datetime(parsed_date.year, parsed_date.month, 1, 0, 0, 0)
+        next_month = start_of_month + relativedelta(months=1)
+        return (start_of_month, next_month)
+    if 'week' in date_str:
+        # if week in date string, dateparser parses it to next week start
+        # so today = end of this week
+        start_of_week = start_of_day - timedelta(days=7)
+        return (start_of_week, start_of_day)
+    else:
+        next_day = start_of_day + relativedelta(days=1)
+        return (start_of_day, next_day)