Add plugin API

1 files changed, 92 insertions, 0 deletions

diff --git a/coinfetch.py b/coinfetch.py
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+++ b/coinfetch.py
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+##
+##  coinfetch - plugin-based cryptocurrency price converter
+##  Copyright (C) 2015 Delwink, LLC
+##
+##  This program is free software: you can redistribute it and/or modify
+##  it under the terms of the GNU Affero General Public License as published by
+##  the Free Software Foundation, version 3 only.
+##
+##  This program is distributed in the hope that it will be useful,
+##  but WITHOUT ANY WARRANTY; without even the implied warranty of
+##  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+##  GNU Affero General Public License for more details.
+##
+##  You should have received a copy of the GNU Affero General Public License
+##  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+##
+
+from requests import get
+
+__version__ = '5.0.0'
+
+## A cryptocurrency exchange rate ticker.
+class Ticker():
+    ## Constructor for this class.
+    #  @param path The URL prefix for this ticker.
+    #  @param kind Which type of exchange rate to fetch.
+    def __init__(self, path, kind='avg'):
+        self.path = path
+        self.kind = kind
+
+    ## Defines how a currency pair is defined in the request URL.
+    #  @param a The first currency.
+    #  @param b The second currency.
+    #  @return A pair string to be used in the request URL.
+    def get_pair(a, b):
+        return '{}_{}'.format(a, b)
+
+    ## Extracts the exchange rate data from the server response.
+    #  @param response Original response from the ticker server.
+    #  @param The coin pair as a list/tuple.
+    #  @return The data for the selected pair.
+    def get_pair_data(response, pair):
+        return response.json()[self.get_pair(pair[0], pair[1])]
+
+    ## Calculates the exchange rate between two currencies.
+    #  @param a The first currency.
+    #  @param b The second currency.
+    #  @param amt The number quantity of 'a' currency.
+    def get_rate(a, b, amt=1):
+        r = get(self.path + self.get_pair(a, b))
+
+        try:
+            res = get_pair_data(r, (a, b))
+            return float(res[self.kind]) * amt
+        except (KeyError, TypeError):
+            try:
+                r = get(self.path + self.get_pair(b, a)) # reverse order
+
+                res = get_pair_data(r, (a, b))
+                return (float(res[self.kind]) ** -1) * amt
+            except TypeError as e:
+                raise ValueError(str(e)) # currency pair not found
+
+_INDEX = {
+    'description': 0,
+    'value': 1
+}
+
+_tickers = {}
+
+## Gets the registered tickers and their descriptions.
+#  @return A list of tuples containing the ticker name and description.
+def get_registered_tickers():
+    lst = []
+
+    for key in _tickers:
+        lst.append((key, _tickers[key][_INDEX['description']]))
+
+    return lst
+
+## Gets a particular ticker object.
+#  @param key Name of the desired ticker.
+#  @return The Ticker object specified by 'key'.
+def get_ticker(key):
+    return _tickers[key][_INDEX['value']]
+
+## Registers a new ticker API.
+#  @param name Name of this ticker.
+#  @param description A brief description of this ticker.
+#  @param obj An instance of the ticker's implementation class.
+def register_ticker(name, description, obj):
+    _tickers[name] = (description, obj)