From 237940861f474fcea14407603bf715c19a64c079 Mon Sep 17 00:00:00 2001
From: Dominik Roth <dominik.roth.dev@gmail.com>
Date: Sat, 30 Oct 2021 14:18:14 +0200
Subject: [PATCH] Included a cache

---
 .gitignore |  1 +
 meuro.py   | 66 +++++++++++++++++++++++++++++++++++-------------------
 2 files changed, 44 insertions(+), 23 deletions(-)

diff --git a/.gitignore b/.gitignore
index bee8a64..666886f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 __pycache__
+cache.json
diff --git a/meuro.py b/meuro.py
index d208e5e..bf582b1 100755
--- a/meuro.py
+++ b/meuro.py
@@ -1,34 +1,53 @@
 #!/usr/bin/python3
-import requests
+import requests, json, os.path
 from datetime import datetime
 from dateutil import relativedelta
 from dateutil import parser as dparser
 from dateutil.parser._parser import ParserError as DateParserError
 
-# Ugly code thats outside of any function
-url = 'https://sdw.ecb.europa.eu/quickviewexport.do?SERIES_KEY=122.ICP.M.U2.N.000000.4.ANR&type=csv'
-resp = requests.get(url)
-lines = resp.text.split('\n')[6:]
-years = {} # Will later contain the monthly factor of inflation (~1.0016667) for every month
-for line in lines:
-    vals = line.split(',')
-    year = int(vals[0][:4])
-    month = datetime.strptime(vals[0][4:],'%b').month
-    inflation = float(vals[1])
-    if not year in years:
-        years[year] = {}
-    years[year][month] = 1 + (inflation/100)/12
+_years = None
 
-for year in years:
-    months = years[year]
-    for month in range(1,13):
-        if month not in months:
-            years[year][month] = 1 + 0.02/12 # Lets say the ECB archives their target
+def _loadYearsTable(maxCacheSeconds=3600):
+    if os.path.isfile('cache.json'):
+        with open('cache.json', 'r') as f:
+            cacheUpdate, cacheYears = json.loads(f.read())
+        if (datetime.now() - dparser.isoparse(cacheUpdate)).total_seconds() < maxCacheSeconds:
+            # JSON does not allow integers as keys; so we convert them back here...
+            cacheYears = {int(y):{int(m):float(n) for m,n in ms.items()} for y,ms in cacheYears.items()}
+            return cacheYears
+    return _loadYearsTableWeb()
+
+def _loadYearsTableWeb():
+    print('[i] Fetching new data from ECB-Servers...')
+    url = 'https://sdw.ecb.europa.eu/quickviewexport.do?SERIES_KEY=122.ICP.M.U2.N.000000.4.ANR&type=csv'
+    resp = requests.get(url)
+    lines = resp.text.split('\n')[6:]
+    years = {} # Will later contain the monthly factor of inflation (~1.0016667) for every month
+    for line in lines:
+        vals = line.split(',')
+        year = int(vals[0][:4])
+        month = datetime.strptime(vals[0][4:],'%b').month
+        inflation = float(vals[1])
+        if not year in years:
+            years[year] = {}
+        years[year][month] = 1 + (inflation/100)/12
+
+    for year in years:
+        months = years[year]
+        for month in range(1,13):
+            if month not in months:
+                years[year][month] = 1 + 0.02/12 # Lets say the ECB archives their target
+    with open('cache.json', 'w') as f:
+        f.write(json.dumps([datetime.now().isoformat(),years]))
+    return years
 
 # Gives you the exchange rate between euros and meuros for the given date.
 # (Should always be a float < 1)
 # date should be either a datetime-object or None (= current date)
 def exchangeRate(date=None):
+    global _years
+    if _years==None:
+        _years = _loadYearsTable()
     if date==None:
         date = datetime.now()
     month, year = date.month, date.year
@@ -37,23 +56,24 @@ def exchangeRate(date=None):
     akk = 1
     for fullYear in range(2001, year):
         yearlyInf = 1
-        for m in years[fullYear]:
-            monthlyInf = years[fullYear][m]
+        for m in _years[fullYear]:
+            monthlyInf = _years[fullYear][m]
             yearlyInf *= monthlyInf
         akk *= yearlyInf
 
     for fullMonth in range(1, month):
-        monthlyInf = years[year][fullMonth]
+        monthlyInf = _years[year][fullMonth]
         akk *= monthlyInf
 
     beginningOfMonth = date.replace(hour=0, minute=0, second=0, microsecond=0, day=1)
     endOfMonth = beginningOfMonth + relativedelta.relativedelta(months=1)
     fracOfMonth = (date - beginningOfMonth).total_seconds() / (endOfMonth - beginningOfMonth).total_seconds()
-    inflationThisMonth = 1 + fracOfMonth * (years[year][month]-1)
+    inflationThisMonth = 1 + fracOfMonth * (_years[year][month]-1)
 
     akk *= inflationThisMonth
 
     return 1/akk
+
 # Converts the given amount of euros to meuros for the given date. (wholeCents means it rounds to two decimal places)
 # date should be either a datetime-object or None (= current date)
 def euroToMeuro(eur,date=None,wholeCents=True):