Implement caching of calendar files

TODO:
- Documentation
- Adjust README

.gitignore

@@ -131,4 +131,4 @@ dmypy.json
 # Pyre type checker
 .pyre/
 app/config/calendar.json
-app/config/calendar.json
+/app/cache/

app/server.py

@@ -1,4 +1,5 @@
 from tools.tools import *
+from tools.caching import *
 from flask import Flask, make_response
 
 app = Flask(__name__)
@@ -10,10 +11,18 @@ def main(calendar):
 
     print("Opening " + conf)
 
-    result = str(process(conf))
-    response = make_response(result, 200)
-    response.headers["Content-Disposition"] = "attachment; filename=calendar.ics"
+    try:
+        result = str(process(conf))
+        response = make_response(result, 200)
+        response.headers["Content-Disposition"] = "attachment; filename=calendar.ics"
+    except FileNotFoundError:
+        response = make_response("Calendar not cached", 425)
+
     return response
 
 
+# TODO find better way to launch periodic caching
+#   Maybe try with https://docs.python.org/3/library/sched.html
+thread = CacheThread()
+thread.start()
 app.run(host='0.0.0.0', port=8088)

app/tools/caching.py

@@ -0,0 +1,91 @@
+import json
+import os
+import threading
+import time
+from hashlib import sha256
+
+import arrow
+import requests
+from ics import Calendar
+
+
+def cache(entry: dict) -> None:
+    if not os.path.isdir('cache'):
+        os.mkdir('cache')
+
+    url = entry['url']
+    path = "cache/" + sha256(url.encode()).hexdigest() + ".ics"
+
+    r = requests.get(entry["url"], allow_redirects=True)
+    if "encoding" in entry:
+        cal = Calendar(imports=r.content.decode(encoding=entry["encoding"]))
+    else:
+        cal = Calendar(imports=r.content.decode())
+
+    cal = horodate(cal, 'Cached at')
+    open(path, 'w').writelines(cal)
+
+
+def get_from_cache(entry: dict) -> Calendar:
+    url = entry['url']
+    path = "cache/" + sha256(url.encode()).hexdigest() + ".ics"
+    if not os.path.isfile(path):
+        print("Not cached")
+        raise FileNotFoundError("The calendar is not cached")
+
+    with open(path, 'r') as file:
+        data = file.read()
+
+    return Calendar(imports=data)
+
+
+def load_cal(entry: dict) -> Calendar:
+    if "cache" in entry and entry["cache"]:
+        print("Getting", entry["name"], "from cache")
+        return get_from_cache(entry)
+
+    else:
+        print("Getting", entry["name"], "from remote")
+        r = requests.get(entry["url"], allow_redirects=True)
+        if "encoding" in entry:
+            cal = Calendar(imports=r.content.decode(encoding=entry["encoding"]))
+        else:
+            cal = Calendar(imports=r.content.decode())
+
+        cal = horodate(cal, 'Downloaded at')
+        return cal
+
+
+def horodate(cal: Calendar, prefix='') -> Calendar:
+    now = arrow.now().format("YYYY-MM-DD HH:mm:ss")
+    for event in cal.events:
+        event.description = event.description + '\n' + prefix + ' ' + now \
+            if event.description is not None else prefix + ' ' + now
+
+    return cal
+
+
+def background_cache() -> None:
+    path = "config"
+    files = [os.path.join(path, f) for f in os.listdir(path)
+             if os.path.isfile(os.path.join(path, f)) and f.endswith('.json')]
+
+    for file in files:
+        with open(file, 'r') as config_file:
+            config = json.loads(config_file.read())
+
+        for entry in config:
+            if 'cache' in entry and entry['cache']:
+                cache(entry)
+    print('Cache renewed', arrow.now().format("YYYY-MM-DD HH:mm:ss"))
+
+
+class CacheThread(threading.Thread):
+    def __init__(self):
+        threading.Thread.__init__(self)
+
+    def run(self):
+        print("Starting cache process")
+        while True:
+            background_cache()
+            time.sleep(10*60)

app/tools/tools.py

@@ -73,11 +73,11 @@ Only the url and the name field are mandatory.
 
 import json
 import re
+from typing import List
 
-import requests
 from ics import Calendar
 from pathvalidate import sanitize_filename
-from typing import List
+from tools.caching import load_cal
 
 
 def filtering(cal: Calendar, filters: dict, field_name: str) -> Calendar:
@@ -241,11 +241,11 @@ def modify_text(cal: Calendar, modify: dict, field_name: str) -> Calendar:
                         if event.name is not None else change["addSuffix"]
 
                 elif field_name == "description":
-                    event.name = event.description + change["addSuffix"] \
+                    event.description = event.description + change["addSuffix"] \
                         if event.description is not None else change["addSuffix"]
 
                 elif field_name == "location":
-                    event.name = event.location + change["addSuffix"] \
+                    event.location = event.location + change["addSuffix"] \
                         if event.location is not None else change["addSuffix"]
 
     return cal
@@ -321,12 +321,8 @@ def process(path: str) -> Calendar:
     data = []
 
     for entry in config:
-        print("Getting " + entry["name"])
-        r = requests.get(entry["url"], allow_redirects=True)
-        if "encoding" in entry:
-            cal = Calendar(imports=r.content.decode(encoding=entry["encoding"]))
-        else:
-            cal = Calendar(imports=r.content.decode())
+
+        cal = load_cal(entry)
 
         if "filters" in entry:
             cal = apply_filters(cal, entry["filters"])

requirements.txt

@@ -2,3 +2,4 @@ requests~=2.22.0
 ics~=0.7
 pathvalidate~=2.3.0
 flask~=1.1.1
+arrow~=0.14.7