Caching ClearSky requests

Signed-off-by: Markus Birth <markus@birth-online.de>

main.py

@@ -1,4 +1,5 @@
 import configparser
+import json
 import requests
 import os.path
 import pickle
@@ -65,8 +66,15 @@ class ClearSky():
             url = self.BASE_URL + "/api/v1/" + uri
             if page > 1:
                 url += f"/{page}"
-            r = requests.get(url).json()
-            sleep(0.20)    # Poor man's way of making sure to not go over 5 requests per second
+            cachefile = "cs_" + url[len(self.BASE_URL)+8:].replace("/", "_") + ".json"
+            if os.path.isfile(cachefile):
+                with open(cachefile, "rt") as f:
+                    r = json.load(f)
+            else:
+                r = requests.get(url).json()
+                with open(cachefile, "wt") as f:
+                    json.dump(r, f)
+                sleep(0.20)    # Poor man's way of making sure to not go over 5 requests per second
             data_len = len(r["data"][data_key]) if data_key else len(r["data"])
             result += r["data"][data_key] if data_key else r["data"]
             if data_len < 100: