Station icons: Basic station icon caching

Storage path for the station icon cache is: ~/.ycast/cache/icons

ycast/generic.py

@@ -1,6 +1,9 @@
 import logging
+import os
 
 USER_AGENT = 'YCast'
+VAR_PATH = os.path.expanduser("~") + '/.ycast'
+CACHE_PATH = VAR_PATH + '/cache'
 
 
 class Directory:
@@ -31,3 +34,15 @@ def get_stationid_without_prefix(uid):
         logging.error("Could not extract stationid (Invalid station id length)")
         return None
     return uid[3:]
+
+
+def get_cache_path(cache_name):
+    cache_path = CACHE_PATH + '/' + cache_name
+    try:
+        os.makedirs(cache_path)
+    except FileExistsError:
+        pass
+    except PermissionError:
+        logging.error("Could not create cache folders (%s) because of access permissions", cache_path)
+        return None
+    return cache_path

ycast/server.py

@@ -262,9 +262,9 @@ def get_station_icon():
     if not hasattr(station, 'icon') or not station.icon:
         logging.warning("No icon information found for station with id '%s'", stationid)
         abort(404)
-    station_icon = station_icons.get_icon_from_url(station.icon)
+    station_icon = station_icons.get_icon(station)
     if not station_icon:
-        logging.error("Could not convert station icon for station with id '%s'", stationid)
+        logging.error("Could not get station icon for station with id '%s'", stationid)
         abort(404)
     response = make_response(station_icon)
     response.headers.set('Content-Type', 'image/jpeg')

ycast/station_icons.py

@@ -1,6 +1,7 @@
 import logging
 import requests
 import io
+import os
 
 from PIL import Image
 
@@ -8,31 +9,42 @@ import ycast.generic as generic
 from ycast import __version__
 
 MAX_SIZE = 290
+CACHE_NAME = 'icons'
 
 
-def get_icon_from_url(iconurl):
+def get_icon(station):
-    # TODO cache icons on disk
+    cache_path = generic.get_cache_path(CACHE_NAME)
-    headers = {'User-Agent': generic.USER_AGENT + '/' + __version__}
+    if not cache_path:
-    try:
-        response = requests.get(iconurl, headers=headers)
-    except requests.exceptions.ConnectionError as err:
-        logging.error("Connection to station icon URL failed (%s)", err)
-        return None
-    if response.status_code != 200:
-        logging.error("Could not get station icon data from %s (HTML status %s)", iconurl, response.status_code)
         return None
+    station_icon_file = cache_path + '/' + station.id
+    if not os.path.exists(station_icon_file):
+        logging.debug("Station icon cache miss. Fetching and converting station icon for station id '%s'", station.id)
+        headers = {'User-Agent': generic.USER_AGENT + '/' + __version__}
+        try:
+            response = requests.get(station.icon, headers=headers)
+        except requests.exceptions.ConnectionError as err:
+            logging.error("Connection to station icon URL failed (%s)", err)
+            return None
+        if response.status_code != 200:
+            logging.error("Could not get station icon data from %s (HTML status %s)", station.icon, response.status_code)
+            return None
+        try:
+            image = Image.open(io.BytesIO(response.content))
+            image = image.convert("RGB")
+            if image.size[0] > image.size[1]:
+                ratio = MAX_SIZE / image.size[0]
+            else:
+                ratio = MAX_SIZE / image.size[1]
+            image = image.resize((int(image.size[0] * ratio), int(image.size[1] * ratio)), Image.ANTIALIAS)
+            image.save(station_icon_file, format="JPEG")
+        except Exception as e:
+            logging.error("Station icon conversion error (%s)", e)
+            return None
     try:
-        image = Image.open(io.BytesIO(response.content))
+        with open(station_icon_file, 'rb') as file:
-        image = image.convert("RGB")
+            image_conv = file.read()
-        if image.size[0] > image.size[1]:
+    except PermissionError:
-            ratio = MAX_SIZE / image.size[0]
+        logging.error("Could not access station icon file in cache (%s) because of access permissions",
-        else:
+                      station_icon_file)
-            ratio = MAX_SIZE / image.size[1]
-        image = image.resize((int(image.size[0] * ratio), int(image.size[1] * ratio)), Image.ANTIALIAS)
-        with io.BytesIO() as output_img:
-            image.save(output_img, format="JPEG")
-            image_conv = output_img.getvalue()
-    except Exception as e:
-        logging.error("Station icon conversion error (%s)", e)
         return None
     return image_conv