add simple call

multicall/call.py

@@ -0,0 +1,27 @@
+from dataclasses import dataclass
+from eth_utils import to_checksum_address
+from web3.auto import w3
+from multicall.signature import Signature
+
+
+class Call:
+    def __init__(self, target, function, returns):
+        self.target = to_checksum_address(target)
+        if isinstance(function, list):
+            self.function, *self.args = function
+        else:
+            self.function = function
+            self.args = None
+        self.signature = Signature(self.function)
+        self.returns = returns
+
+    def __call__(self, args=None):
+        args = args or self.args
+        calldata = self.signature.encode_data(args)
+        output = w3.eth.call({'to': self.target, 'data': calldata})
+        decoded = self.signature.decode_data(output)
+        return {
+            name: handler(value) if handler else value
+            for (name, handler), value
+            in zip(self.returns, decoded)
+        }

tests/test_call.py

@@ -0,0 +1,22 @@
+from multicall.call import Call
+
+CHAI = '0x06AF07097C9Eeb7fD685c692751D5C66dB49c215'
+
+
+def from_wei(value):
+    return value / 1e18
+
+
+def test_call():
+    call = Call(CHAI, 'name()(string)', [['name', None]])
+    assert call() == {'name': 'Chai'}
+
+
+def test_call_with_args():
+    call = Call(CHAI, 'balanceOf(address)(uint256)', [['balance', from_wei]])
+    assert isinstance(call([CHAI])['balance'], float)
+
+
+def test_call_with_predefined_args():
+    call = Call(CHAI, ['balanceOf(address)(uint256)', CHAI], [['balance', from_wei]])
+    assert isinstance(call()['balance'], float)