CoinDesk fetch.

src/pricehist/sources/CoinDesk.py

@@ -30,3 +30,21 @@ class CoinDesk():
         data = json.loads(response.content)
         symbols = sorted([item['currency'] for item in data])
         return symbols
+
+    def fetch(self, pair, start, end):
+        base, quote = pair.split('/')
+        if base not in self.bases():
+            exit(f'Invalid base {base}')
+        if quote not in self.quotes():
+            exit(f'Invalid quote {quote}')
+
+        min_start = '2010-07-17'
+        if start < min_start:
+            exit(f'start {start} too early. The CoinDesk BPI only covers data from {min_start} onwards.')
+
+        url = f'https://api.coindesk.com/v1/bpi/historical/close.json?currency={quote}&start={start}&end={end}'
+        response = requests.get(url)
+        data = json.loads(response.content)
+        bpi = data['bpi']
+
+        return bpi