luno · YinYin-blip · Jul 8, 2019 · Jul 9, 2019 · Jul 9, 2019 · Jul 9, 2019
diff --git a/README.md b/README.md
@@ -23,9 +23,9 @@ from luno_python.client import Client
 c = Client(api_key_id='key_id', api_key_secret='key_secret')
 try:
   res = c.get_ticker(pair='XBTZAR')
-  print res
+  print(res)
 except Exception as e:
-  print e
+  print(e)
 ```
 
 ### License

diff --git a/examples/stream.py b/examples/stream.py
@@ -0,0 +1,21 @@
+import asyncio
+
+from luno_python.stream_client import stream_market
+from luno_python.api_types import format_state
+
+def handle_update(pair, state, update):
+    print(format_state(pair, state))
+    if update is not None:
+        print(update)
+
+async def main():
+    await stream_market(
+        pair="XBTZAR",
+        api_key_id="", # API Key goes here
+        api_key_secret="", # and API Secret goes here
+        update_callback=handle_update,
+    )
+
+
+if __name__ == "__main__":
+    asyncio.run(main())
diff --git a/luno_python/api_types.py b/luno_python/api_types.py
@@ -0,0 +1,26 @@
+from collections import namedtuple
+from decimal import Decimal
+from typing import List
+
+DEC_0 = Decimal("0")
+
+Order = namedtuple("Order", "order_id price volume")
+
+MarketState = namedtuple("MarketState", "sequence asks bids status")
+
+Pair = namedtuple("Pair", "base counter")
+
+def format_orderbook(pair: Pair, asks: List[Order], bids: List[Order]):
+    if not bids or not asks:
+        return "Empty Orderbook"
+
+    bid_sum = sum((o.price * o.volume for o in bids), DEC_0)
+    ask_sum = sum((o.volume for o in asks), DEC_0)
+
+    mid = (asks[0].price + bids[0].price) / 2
+
+    return f"{bid_sum} {pair.counter} - {mid} - {ask_sum} {pair.base}"
+
+def format_state(pair: Pair, state: MarketState):
+    orderbook = format_orderbook(pair, state.asks, state.bids)
+    return f"[{state.sequence}] {orderbook}"
diff --git a/luno_python/client.py b/luno_python/client.py
@@ -13,9 +13,9 @@ class Client(BaseClient):
       c = Client(api_key_id='key_id', api_key_secret='key_secret')
       try:
         res = c.get_ticker(pair='XBTZAR')
-        print res
+        print(res)
       except Exception as e:
-        print e
+        print(e)
     """
 
     def cancel_withdrawal(self, id):

diff --git a/luno_python/stream_client.py b/luno_python/stream_client.py
@@ -0,0 +1,203 @@
+"""
+The stream client can be used to receive live updates to the orderbook.
+It also maintains a representation of the Luno orderbook correctly updated for each event.
+
+For example usage see examples/stream.py
+"""
+
+import asyncio
+from decimal import Decimal
+import json
+from typing import Callable, Dict, List
+import websockets
+
+from .api_types import DEC_0, Order, MarketState, Pair
+
+DEFAULT_URL = "wss://ws.luno.com"
+
+StateUpdate = Callable[[Pair, MarketState, dict], None]
+
+class OutOfOrderMessageException(Exception):
+    pass
+
+class MarketInitialisationException(Exception):
+    pass
+
+
+def _flatten_orders(orders, reverse):
+    return sorted(orders.values(), key=lambda o: o.price, reverse=reverse)
+
+
+def _decrement_trade(orders: Dict[str, Order], order_id: str, volume: Decimal):
+    order = orders.pop(order_id, None)
+    if order is None:
+        return
+
+    new_order = order._replace(volume=order.volume - volume)
+    if new_order.volume > DEC_0:
+        orders[order_id] = new_order
+
+
+class _MarketStreamState:
+    def __init__(self, first: dict):
+        if first is None:
+            raise MarketInitialisationException("Unable to initialise market state from an empty message")
+
+        def conv_message(msg):
+            return Order(
+                msg['id'],
+                Decimal(msg['price']),
+                Decimal(msg['volume']),
+            )
+
+        bids = [conv_message(m) for m in first['bids']]
+        asks = [conv_message(m) for m in first['asks']]
+        self._bids = {b.order_id: b for b in bids}
+        self._asks = {a.order_id: a for a in asks}
+        self._sequence = first['sequence']
+        self._trades = []
+        self._status = first['status']
+
+    def get_asks(self):
+        return _flatten_orders(self._asks, False)
+
+    def get_bids(self):
+        return _flatten_orders(self._bids, True)
+
+    def get_status(self):
+        return self._status
+
+    def get_sequence(self):
+        return self._sequence
+
+    def get_snapshot(self):
+        return MarketState(
+            sequence=self.get_sequence(),
+            asks=self.get_asks(),
+            bids=self.get_bids(),
+            status=self.get_status(),
+        )
+
+    def process_update(self, update: dict):
+        if update is None:
+            return
+
+        seq = update['sequence']
+        if int(seq) != int(self._sequence)+1:
+            raise OutOfOrderMessageException()
+
+        trades = update.get('trade_updates')
+        if trades:
+            self._process_trades(trades)
+
+        create = update.get('create_update')
+        if create:
+            self._process_create(create)
+
+        delete_upd = update.get('delete_update')
+        if delete_upd:
+            self._process_delete(delete_upd)
+
+        status_upd = update.get('status_update')
+        if status_upd:
+            self._process_status(status_upd)
+
+        self._sequence = seq
+
+    def _process_trades(self, trade_updates: List[dict]):
+        for t in trade_updates:
+            maker_id = t['maker_order_id']
+            volume = Decimal(t['base'])
+
+            _decrement_trade(self._asks, maker_id, volume)
+            _decrement_trade(self._bids, maker_id, volume)
+
+    def _process_create(self, create_update: dict):
+        o = Order(
+            create_update['order_id'],
+            Decimal(create_update['price']),
+            Decimal(create_update['volume']),
+        )
+        if create_update['type'] == "ASK":
+            self._asks[o.order_id] = o
+        elif create_update['type'] == "BID":
+            self._bids[o.order_id] = o
+
+    def _process_delete(self, delete_update: dict):
+        order_id = delete_update['order_id']
+        self._asks.pop(order_id, None)
+        self._bids.pop(order_id, None)
+
+    def _process_status(self, status_update: dict):
+        self._status = status_update['status']
+
+
+async def _read_from_websocket(ws, pair: Pair, update_f: StateUpdate):
+    state = None
+    is_first = True
+
+    async for message in ws:
+        try:
+            body = json.loads(message)
+        except ValueError as e:
+            raise ValueError(f"Invalid JSON received: {message}") from e
+
+        if body == "": # Empty update, used as keepalive
+            body = None
+
+        if is_first:
+            is_first = False
+            state = _MarketStreamState(body)
+            update_f(pair, state.get_snapshot(), None)
+            continue
+
+        #could raise OutOfOrderMessageException
+        state.process_update(body)
+
+        update_f(pair, state.get_snapshot(), body)
+
+
+async def _write_keep_alive(ws):
+    while True:
+        await ws.send('""')
+        await asyncio.sleep(60)
+
+
+async def stream_market(
+        pair: str,
+        api_key_id: str,
+        api_key_secret: str,
+        update_callback: StateUpdate,
+        base_url: str = DEFAULT_URL,
+):
+    """Opens a stream to /api/1/stream/...
+
+        Stream orderbook information and maintain an orderbook state.
+
+        :param pair: str Amount to buy or sell in the pair base currency.
-        :param pair: str Amount to buy or sell in the pair base currency.
+        :param pair: str Currency pair code (for example, "XBTZAR").
-        :param pair: str Amount to buy or sell in the pair base currency.
+        :param pair: str Currency pair code (for example, "XBTZAR").
+        :param api_key_id: str
+        :param api_key_secret: str
+        :param update_callback: an StateUpdate function that will be called with new updates.
+    """
+    if len(pair) != 6:
+        raise ValueError(f"pair must be length 6, got '{pair}'")
+
+    p = Pair(pair[:3].upper(), pair[3:].upper())
+    url = '/'.join([base_url, 'api/1/stream', p.base + p.counter])
+
+    async with websockets.connect(
+            url,
+            origin='http://localhost/',
+            ping_interval=None,
+            max_size=2**21,
+    ) as websocket:
+
+        auth = json.dumps({
+            'api_key_id': api_key_id,
+            'api_key_secret': api_key_secret,
+        })
+        await websocket.send(auth)
+
+        async with asyncio.TaskGroup() as tg:
+            tg.create_task(_read_from_websocket(websocket, p, update_callback))
+            tg.create_task(_write_keep_alive(websocket))