currencyrate: new plugin to do currency conversions.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

currencyrate/Makefile

@@ -0,0 +1,7 @@
+#! /usr/bin/make
+
+check:
+	@# E501 line too long (N > 79 characters)
+	@# E731 do not assign a lambda expression, use a def
+	@# W503: line break before binary operator
+	@flake8 --ignore=E501,E731,W503 *.py

currencyrate/README.md

@@ -0,0 +1,41 @@
+# Currencyrate plugin
+
+This plugin provides Bitcoin currency conversion functions using various
+different backends and taking the median.  It caches results for an hour.
+
+## Installation
+
+For general plugin installation instructions see the repos main
+[README.md](https://github.com/lightningd/plugins/blob/master/README.md#Installation)
+
+## Options:
+
+* --add-source: Add a source, of form NAME,URL,MEMBERS where URL and MEMBERS
+  can have `{currency}` and `{currency_lc}` to substitute for upper-case and
+  lower-case currency names.  MEMBERS is how to deconstruct the result, for
+  example if the result is `{"USD": {"last_trade": 12456.79}}` then MEMBERS
+  would be "USD,last_trade".
+* --disable-source: Disable the source with this name.
+
+## Commands
+
+`currencyrate` returns the number of msats per unit from every backend, eg:
+
+```
+$ lightning-cli currencyrate USD
+{
+   "localbitcoins": "5347227msat",
+   "bitstamp": "5577515msat",
+   "coingecko": "5579273msat",
+}
+```
+
+`currencyconvert` converts the given amount and currency into msats, using the
+median from the above results. eg:
+
+```
+$ lightning-cli currencyconvert 100 USD
+{
+   "msat": "515941800msat"
+}
+```

currencyrate/currencyrate.py

@@ -0,0 +1,119 @@
+#!/usr/bin/env python3
+from pyln.client import Plugin
+from collections import namedtuple
+from pyln.client import Millisatoshi
+from cachetools import cached, TTLCache
+import requests
+import statistics
+import time
+
+plugin = Plugin()
+
+Source = namedtuple('Source', ['name', 'urlformat', 'replymembers'])
+
+sources = [
+    # e.g. {"GBP": {"volume_btc": "24.36647424", "rates": {"last": "13667.63"}, "avg_1h": "13786.86", "avg_6h": "13723.65", "avg_12h": "13680.23", "avg_24h": "13739.56"}, "USD": {"volume_btc": "27.97517017", "rates": {"last": "18204.21"}, "avg_1h": "19349.46", "avg_6h": "18621.72", "avg_12h": "18642.28", "avg_24h": "18698.94"}
+    # ...
+    # "GTQ": {"volume_btc": "0.03756101", "rates": {"last": "148505.46"}, "avg_1h": "148505.46", "avg_6h": "162463.69", "avg_12h": "162003.10", "avg_24h": "162003.10"}, "DKK": {"volume_btc": "0.00339923", "rates": {"last": "139737.53"}, "avg_12h": "139737.53", "avg_24h": "139737.53"}, "HTG": {"volume_btc": "0.00024758", "rates": {"last": "2019549.24"}, "avg_6h": "2019549.24", "avg_12h": "2019549.24", "avg_24h": "2019549.24"}, "NAD": {"volume_btc": "0.00722222", "rates": {"last": "360000.11"}, "avg_12h": "360000.11", "avg_24h": "360000.11"}}
+    Source('localbitcoins',
+           'https://localbitcoins.com/bitcoinaverage/ticker-all-currencies/',
+           ['{currency}', "avg_6h"]),
+    # e.g. {"high": "18502.56", "last": "17970.41", "timestamp": "1607650787", "bid": "17961.87", "vwap": "18223.42", "volume": "7055.63066541", "low": "17815.92", "ask": "17970.41", "open": "18250.30"}
+    Source('bitstamp',
+           'https://www.bitstamp.net/api/v2/ticker/btc{currency_lc}/',
+           ['last']),
+    # e.g. {"bitcoin":{"usd":17885.84}}
+    Source('coingecko',
+           'https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies={currency_lc}',
+           ['bitcoin', '{currency_lc}']),
+]
+
+
+def get_currencyrate(plugin, currency, req_template, response_members):
+    # NOTE: Bitstamp has a DNS/Proxy issues that can return 404
+    # Workaround: retry up to 5 times with a delay
+    currency_lc = currency.lower()
+    url = req_template.format(currency_lc=currency_lc, currency=currency)
+    for _ in range(5):
+        r = requests.get(url, proxies=plugin.proxies)
+        if r.status_code != 200:
+            time.sleep(1)
+            continue
+        break
+
+    if r.status_code != 200:
+        plugin.log(level='info', message='{}: bad response {}'.format(url, r.status_code))
+        return None
+
+    json = r.json()
+    for m in response_members:
+        expanded = m.format(currency_lc=currency_lc, currency=currency)
+        if expanded not in json:
+            plugin.log(level='debug', message='{}: {} not in {}'.format(url, expanded, json))
+            return None
+        json = json[expanded]
+
+    try:
+        return Millisatoshi(int(10**11 / float(json)))
+    except Exception:
+        plugin.log(level='info', message='{}: could not convert {} to msat'.format(url, json))
+        return None
+
+
+def set_proxies(plugin):
+    config = plugin.rpc.listconfigs()
+    if 'always-use-proxy' in config and config['always-use-proxy']:
+        paddr = config['proxy']
+        # Default port in 9050
+        if ':' not in paddr:
+            paddr += ':9050'
+        plugin.proxies = {'https': 'socks5h://' + paddr,
+                          'http': 'socks5h://' + paddr}
+    else:
+        plugin.proxies = None
+
+
+# Don't grab these more than once per hour.                        
+@cached(cache=TTLCache(maxsize=1024, ttl=3600))
+def get_rates(plugin, currency):
+    rates = {}
+    for s in sources:
+        r = get_currencyrate(plugin, currency, s.urlformat, s.replymembers)
+        if r is not None:
+            rates[s.name] = r
+
+    return rates
+
+
+@plugin.method("currencyrate")
+def currencyrate(plugin, currency):
+    """Gets currency from given APIs."""
+
+    return get_rates(plugin, currency.upper())
+
+
+@plugin.method("currencyconvert")
+def currencyconvert(plugin, amount, currency):
+    """Converts currency using given APIs."""
+    val = statistics.median([m.millisatoshis for m in get_rates(plugin, currency.upper()).values()]) * float(amount)
+    return {"msat": Millisatoshi(round(val))}
+
+
+@plugin.init()
+def init(options, configuration, plugin):
+    set_proxies(plugin)
+
+    if options['add-source'] != '':
+        parts = options['add-source'].split(',')
+        sources.append(Source(parts[0], parts[1], parts[2:]))
+
+    if options['disable-source'] != '':
+        for s in sources[:]:
+            if s.name == options['disable-source']:
+                sources.remove(s)
+
+
+# As a bad example: binance,https://api.binance.com/api/v3/ticker/price?symbol=BTC{currency}T,price
+plugin.add_option(name='add-source', default='', description='Add source name,urlformat,resultmembers...')
+plugin.add_option(name='disable-source', default='', description='Disable source by name')
+plugin.run()

currencyrate/requirements.txt

@@ -0,0 +1,5 @@
+pyln-client>=0.7.3
+requests>=2.10.0
+requests[socks]>=2.10.0
+packaging>=14.1
+cachetools