Refactor search_exchange_by_data_token to get the events in chunks (#532)

* Added a tweak for search function and used get_event_log. Fixed a typo in the FRE README.

* Fixed typo. Added from_block parameter to find easier the events.

* Fixed unit test for search function.

* Refactored search function to use data_token address again.

* Added black formatting.

Co-authored-by: Călina Cenan <calina@kaolin.tech>

Author: mariacarmina

READMEs/fixed-rate-exchange-flow.md

@@ -130,7 +130,7 @@ data_token.approve(ocean.exchange._exchange_address, to_wei(100), alice_wallet)
 In the same python console:
 ```python
 bob_private_key = os.getenv('TEST_PRIVATE_KEY2')
-bob_wallet = Wallet(ocean.web3, bob_private_key, config.block_confirmations. config transaction_timeout)
+bob_wallet = Wallet(ocean.web3, bob_private_key, config.block_confirmations, config.transaction_timeout)
 print(f"bob_wallet.address = '{bob_wallet.address}'")
 
 #Verify that Bob has ganache ETH
@@ -155,7 +155,8 @@ exchanges for a certain data token, it can be searched by
 providing the data token address.
 
 ```python
-#Search for exchange_id for a certain data token address (e.g. token_address).
+#Search for exchange_id from a specific block retrieved at 3rd step
+#for a certain data token address (e.g. token_address).
 logs = ocean.exchange.search_exchange_by_data_token(token_address)
 print(logs)
 #E.g. First exchange is the wanted one.

ocean_lib/ocean/ocean_exchange.py

@@ -11,7 +11,9 @@
 from ocean_lib.config import Config
 from ocean_lib.exceptions import InsufficientBalance, VerifyTxFailed
 from ocean_lib.models.data_token import DataToken
+from ocean_lib.models.dtfactory import DTFactory
 from ocean_lib.models.fixed_rate_exchange import FixedRateExchange
+from ocean_lib.ocean.util import get_dtfactory_address
 from ocean_lib.web3_internal.currency import pretty_ether_and_wei
 from ocean_lib.web3_internal.wallet import Wallet
 from web3.exceptions import ValidationError
@@ -63,15 +65,24 @@ def get_exchange_id_fallback_dt_and_owner(
 
     @enforce_types
     def search_exchange_by_data_token(self, data_token: str) -> List[AttributeDict]:
+        dtfactory_address = get_dtfactory_address(
+            self._config.address_file, web3=self._web3
+        )
+        dtfactory = DTFactory(self._web3, dtfactory_address)
+        token_registered_log = dtfactory.get_token_registered_event(
+            0, self._web3.eth.block_number, data_token
+        )
+        assert (
+            token_registered_log
+        ), f"No token with '{data_token}' address was created before."
+        from_block = token_registered_log.blockNumber
         fre = self._exchange_contract()
-        events = fre.events
-        exchange_event = getattr(events, "ExchangeCreated")
         filter_args = {"dataToken": data_token}
-        logs = fre.getLogs(
-            exchange_event,
-            argument_filters=filter_args,
-            fromBlock=0,
-            toBlock=self._web3.eth.block_number,
+        logs = fre.get_event_logs(
+            event_name="ExchangeCreated",
+            from_block=from_block,
+            to_block=self._web3.eth.block_number,
+            filters=filter_args,
         )
         return logs
 

ocean_lib/ocean/test/test_ocean_exchange.py

@@ -21,6 +21,18 @@ def _get_exchange_address(config):
     ]
 
 
+def test_search_exchange_by_nonexistent_data_token(publisher_ocean_instance):
+    """Tests searching exchanges with a nonexistent data token address."""
+    ocn = publisher_ocean_instance
+    foo_data_token = "0xcd2a3d9f938e13cd947ec05abc7fe734df8dd826"
+    with pytest.raises(AssertionError) as err:
+        ocn.exchange.search_exchange_by_data_token(foo_data_token)
+    assert (
+        err.value.args[0]
+        == f"No token with '{foo_data_token}' address was created before."
+    )
+
+
 def test_search_exchange_by_data_token(publisher_ocean_instance):
     """Tests searching exchanges which have matching data token address."""
     ocn = publisher_ocean_instance