implement visualcrossing.com weather API (backend)

.env.example

@@ -33,4 +33,12 @@ export SENDER_EMAIL=
 # export STATICMAP_SUBDOMAINS=
 # export MAP_ATTRIBUTION=
 # export DEFAULT_STATICMAP=False
+
+# Define one of the following API key values to lookup weather conditions
+# for the start and end of each workout:
+
+# DarkSky weather API key (deprecated):
 # export WEATHER_API_KEY=
+
+# VisualCrossing.com weather API key:
+# export VC_WEATHER_API_KEY=

fittrackee/workouts/utils/weather.py

@@ -1,40 +1,111 @@
 import os
-from typing import Dict, Optional
+from typing import Dict, Optional, Union
 
 import forecastio
+import requests
 import pytz
+from datetime import datetime, timedelta
 from gpxpy.gpx import GPXTrackPoint
 
 from fittrackee import appLog
 
 API_KEY = os.getenv('WEATHER_API_KEY')
+VC_API_KEY = os.getenv('VC_WEATHER_API_KEY')
 
 
 def get_weather(point: GPXTrackPoint) -> Optional[Dict]:
-    if not API_KEY or not point.time:
-        return None
     try:
-        point_time = (
-            pytz.utc.localize(point.time)
-            if point.time.tzinfo is None
-            else point.time.astimezone(pytz.utc)
-        )
-        forecast = forecastio.load_forecast(
-            API_KEY,
-            point.latitude,
-            point.longitude,
-            time=point_time,
-            units='si',
-        )
-        weather = forecast.currently()
-        return {
-            'summary': weather.summary,
-            'icon': weather.icon,
-            'temperature': weather.temperature,
-            'humidity': weather.humidity,
-            'wind': weather.windSpeed,
-            'windBearing': weather.windBearing,
-        }
+        if not point.time:
+            # if there's no time associated with the point; we cannot get weather
+            return None
+        else:
+            point_time = (
+                pytz.utc.localize(point.time)
+                if point.time.tzinfo is None
+                else point.time.astimezone(pytz.utc)
+            )
+            if API_KEY:
+                # if darksky api key is present, use that
+                forecast = forecastio.load_forecast(
+                    API_KEY,
+                    point.latitude,
+                    point.longitude,
+                    time=point_time,
+                    units='si',
+                )
+                weather = forecast.currently()
+                return {
+                    'summary': weather.summary,
+                    'icon': weather.icon,
+                    'temperature': weather.temperature,
+                    'humidity': weather.humidity,
+                    'wind': weather.windSpeed,
+                    'windBearing': weather.windBearing,
+                }
+            elif VC_API_KEY:
+                # if visualcrossing API key is present, use that
+                return get_visual_crossing_weather(VC_API_KEY, point.latitude, 
+                                                   point.longitude, point.time)
+            else:
+                return None
+
     except Exception as e:
         appLog.error(e)
         return None
+
+
+def get_visual_crossing_weather(api_key: str, 
+                                latitude: float, 
+                                longitude: float, 
+                                time: datetime) -> Dict[str, Union[str, float]]:
+    # All requests to the Timeline Weather API use the following the form:
+
+    # https://weather.visualcrossing.com/VisualCrossingWebServices/rest/services
+    # /timeline/[location]/[date1]/[date2]?key=YOUR_API_KEY 
+
+    # location (required) – is the address, partial address or latitude,longitude location for 
+    # which to retrieve weather data. You can also use US ZIP Codes.
+
+    # date1 (optional) – is the start date for which to retrieve weather data. 
+    # You can also request the information for a specific time for a single date by 
+    # including time into the date1 field using the format yyyy-MM-ddTHH:mm:ss. 
+    # For example 2020-10-19T13:00:00.
+
+    # The results are returned in the ‘currentConditions’ field and are truncated to the 
+    # hour requested (i.e. 2020-10-19T13:59:00 will return data at 2020-10-19T13:00:00).
+    
+    # first, round datetime to nearest hour by truncating, and then adding an hour if
+    # the "real" time's number of minutes is 30 or more (we do this since the API only truncates)
+    trunc_time = (time.replace(second=0, microsecond=0, minute=0, hour=time.hour) + 
+        timedelta(hours=time.minute//30))
+    appLog.debug(f'VC_weather: truncated time {time} ({time.timestamp()}) to '
+                 f'{trunc_time} ({trunc_time.timestamp()})')
+
+    base_url = 'https://weather.visualcrossing.com/VisualCrossingWebServices/rest/services'
+    url = f"{base_url}/timeline/{latitude},{longitude}/{int(trunc_time.timestamp())}?key={api_key}"
+    params = {
+        "unitGroup": "metric", 
+        "contentType": "json", 
+        "elements": "datetime,datetimeEpoch,temp,humidity,windspeed,winddir,conditions,description,icon",
+        "include": "current"
+    }
+    appLog.debug(f'VC_weather: getting weather from {url}'.replace(api_key, '*****'))
+    r = requests.get(url, params=params)
+    r.raise_for_status()
+    res = r.json()
+    weather = res['currentConditions']
+    # FitTrackee expects the following units:
+    #   temp: Celsius, 
+    #   humidity: in fraction (rather than percent)
+    #   windSpeed: m/s
+    #   windBearing: direction wind is from in degrees (0 is north)
+    # VC provides humidity in percent, wind in km/h
+    data =  {
+        'summary': weather['conditions'],
+        'icon': f"vc-{weather['icon']}",
+        'temperature': weather['temp'],
+        'humidity': weather['humidity'] / 100,
+        'wind': weather['windspeed'] * 1000 / (60 * 60), # km/h to m/s
+        'windBearing': weather['winddir'],
+    }
+    return data