Infer country from timezone when only tz received by chat API

Timezone is easier to infer using clients system clock. This can be
used to infer user country name, country code, even if ip based
location cannot be inferred.

This makes using location data to contextualize Khoj's responses more
robust. For example, online search results are retrieved for user's
country, even if call to ipapi.co for ip based location fails

src/khoj/routers/api_chat.py

@@ -55,6 +55,8 @@ from khoj.utils.helpers import (
     ConversationCommand,
     command_descriptions,
     convert_image_to_webp,
+    get_country_code_from_timezone,
+    get_country_name_from_timezone,
     get_device,
     is_none_or_empty,
 )
@@ -556,8 +558,8 @@ async def chat(
     conversation_id = body.conversation_id
     city = body.city
     region = body.region
-    country = body.country
-    country_code = body.country_code
+    country = body.country or get_country_name_from_timezone(body.timezone)
+    country_code = body.country_code or get_country_code_from_timezone(body.timezone)
     timezone = body.timezone
     image = body.image
 

src/khoj/utils/helpers.py

@@ -9,6 +9,7 @@ import random
 import uuid
 from collections import OrderedDict
 from enum import Enum
+from functools import lru_cache
 from importlib import import_module
 from importlib.metadata import version
 from itertools import islice
@@ -24,6 +25,7 @@ import torch
 from asgiref.sync import sync_to_async
 from magika import Magika
 from PIL import Image
+from pytz import country_names, country_timezones
 
 from khoj.utils import constants
 
@@ -431,3 +433,24 @@ def convert_image_to_webp(image_bytes):
         webp_image_bytes = webp_image_io.getvalue()
         webp_image_io.close()
         return webp_image_bytes
+
+
+@lru_cache
+def tz_to_cc_map() -> dict[str, str]:
+    """Create a mapping of timezone to country code"""
+    timezone_country = {}
+    for countrycode in country_timezones:
+        timezones = country_timezones[countrycode]
+        for timezone in timezones:
+            timezone_country[timezone] = countrycode
+    return timezone_country
+
+
+def get_country_code_from_timezone(tz: str) -> str:
+    """Get country code from timezone"""
+    return tz_to_cc_map().get(tz, "US")
+
+
+def get_country_name_from_timezone(tz: str) -> str:
+    """Get country name from timezone"""
+    return country_names.get(get_country_code_from_timezone(tz), "United States")