From d737e29c6f9c3fcbdafce5f184b8cb3b234db006 Mon Sep 17 00:00:00 2001
From: Yehuda Deutsch <yeh@uda.co.il>
Date: Fri, 31 Jul 2020 22:54:23 +0300
Subject: [PATCH] Add timezone option

---
 time_app/helpers/datetime.py | 19 ++++++++++++++++---
 time_app/helpers/views.py    | 11 +++++++++++
 time_app/views/api.py        | 12 ++++++------
 time_app/views/main.py       | 13 +++++++++----
 4 files changed, 42 insertions(+), 13 deletions(-)
 create mode 100644 time_app/helpers/views.py

diff --git a/time_app/helpers/datetime.py b/time_app/helpers/datetime.py
index 69b5afa..a872a5e 100644
--- a/time_app/helpers/datetime.py
+++ b/time_app/helpers/datetime.py
@@ -1,8 +1,21 @@
 from datetime import datetime
-from zoneinfo import ZoneInfo
+from zoneinfo import ZoneInfo, available_timezones
 
-utc = ZoneInfo('UTC')
+ALLOWED_TIMEZONES = available_timezones()
+DATETIME_FORMAT = '%Y-%m-%d %H:%M:%S'
+
+
+def tz_aware_now(zone: str) -> datetime:
+    """
+    :param str zone: Zone name in DB
+    :return: A timezone aware datetime object
+    :raises: ValueError When zone name is not supported
+    """
+    # ZoneInfo uses a weak cache, no need to implement a local cache
+    if zone not in ALLOWED_TIMEZONES:
+        raise ValueError(f'Unsupported timezone "{zone}"')
+    return datetime.now(tz=ZoneInfo(zone))
 
 
 def real_utc_now() -> datetime:
-    return datetime.now(tz=utc)
+    return tz_aware_now('UTC')
diff --git a/time_app/helpers/views.py b/time_app/helpers/views.py
new file mode 100644
index 0000000..6789841
--- /dev/null
+++ b/time_app/helpers/views.py
@@ -0,0 +1,11 @@
+from fastapi import HTTPException
+
+from .datetime import tz_aware_now
+
+
+def get_now_in_view(zone: str = 'UTC'):
+    try:
+        now = tz_aware_now(zone=zone)
+    except ValueError:
+        raise HTTPException(status_code=400, detail=f'Zone "{zone}" is unsupported')
+    return now
diff --git a/time_app/views/api.py b/time_app/views/api.py
index deb03f4..3bf64eb 100644
--- a/time_app/views/api.py
+++ b/time_app/views/api.py
@@ -1,16 +1,16 @@
 from fastapi import APIRouter
 
-from time_app.helpers.datetime import real_utc_now
+from time_app.helpers.views import get_now_in_view
 from time_app.models.main import Now
 
 router = APIRouter()
 
 
-@router.get('/', name='Now', response_model=Now)
-def now_view() -> dict:
-    return {"time": real_utc_now().strftime('%Y-%m-%d %H:%M:%S')}
+@router.get('/now', name='Now', response_model=Now)
+def now_view(zone: str = 'UTC') -> dict:
+    return {"time": f'{get_now_in_view(zone):%Y-%m-%d %H:%M:%S}'}
 
 
 @router.get('/diy', name='Day in year', response_model=Now)
-def day_in_year_view() -> dict:
-    return {"time": real_utc_now().strftime('%y%j')[-4:]}
+def day_in_year_view(zone: str = 'UTC') -> dict:
+    return {"time": f'{get_now_in_view(zone):%y%j}'[-4:]}
diff --git a/time_app/views/main.py b/time_app/views/main.py
index 9e10152..2fa9dad 100644
--- a/time_app/views/main.py
+++ b/time_app/views/main.py
@@ -1,15 +1,20 @@
 from fastapi import APIRouter
 
-from time_app.helpers.datetime import real_utc_now
+from time_app.helpers.views import get_now_in_view
 
 router = APIRouter()
 
 
 @router.get('/', name='Now')
 def now_view() -> str:
-    return real_utc_now().strftime('%Y-%m-%d %H:%M:%S')
+    return f'{get_now_in_view():%Y-%m-%d %H:%M:%S}'
+
+
+@router.get('/now', name='Now')
+def now_view(zone: str = 'UTC') -> str:
+    return f'{get_now_in_view(zone):%Y-%m-%d %H:%M:%S}'
 
 
 @router.get('/diy', name='Day in year')
-def day_in_year_view() -> str:
-    return real_utc_now().strftime('%y%j')[-4:]
+def day_in_year_view(zone: str = 'UTC') -> str:
+    return f'{get_now_in_view(zone):%y%j}'[-4:]