Introduce equivalence classes for gas speed names

nucypher/utilities/datafeeds.py

@@ -14,12 +14,14 @@
  You should have received a copy of the GNU Affero General Public License
  along with nucypher.  If not, see <https://www.gnu.org/licenses/>.
 """
+
 from abc import ABC, abstractmethod
+from difflib import get_close_matches
 from typing import Optional
 
 import requests
+from constant_sorrow.constants import SLOW, MEDIUM, FAST, FASTEST
 from web3 import Web3
-from web3.gas_strategies.rpc import rpc_gas_price_strategy
 from web3.types import Wei, TxParams
 
 
@@ -54,6 +56,13 @@ class EthereumGasPriceDatafeed(Datafeed):
     _speed_names = NotImplemented
     _default_speed = NotImplemented
 
+    _speed_equivalence_classes = {
+        SLOW: ('slow', 'safeLow', 'low'),
+        MEDIUM: ('medium', 'standard', 'average'),
+        FAST: ('fast', 'high'),
+        FASTEST: ('fastest', )
+    }
+
     @abstractmethod
     def _parse_gas_prices(self):
         return NotImplementedError
@@ -72,6 +81,22 @@ class EthereumGasPriceDatafeed(Datafeed):
             return gas_price
         return gas_price_strategy
 
+    @classmethod
+    def get_canonical_speed(cls, speed: str):
+        for canonical_speed, speed_names in cls._speed_equivalence_classes.items():
+            if speed.lower() in map(str.lower, speed_names):
+                return canonical_speed
+        else:
+            all_speed_names = [name for names in cls._speed_equivalence_classes.values() for name in names]
+            suggestion = get_close_matches(speed, all_speed_names, n=1)
+            if not suggestion:
+                message = f"'{speed}' is not a valid speed name."
+            else:
+                suggestion = suggestion.pop()
+                message = f"'{speed}' is not a valid speed name. Did you mean '{suggestion}'?"
+            raise LookupError(message)
+
+
 
 class EtherchainGasPriceDatafeed(EthereumGasPriceDatafeed):
     """Gas price datafeed from Etherchain"""

tests/unit/test_datafeeds.py

@@ -18,14 +18,15 @@ along with nucypher.  If not, see <https://www.gnu.org/licenses/>.
 from unittest.mock import patch
 
 import pytest
+from constant_sorrow.constants import SLOW, MEDIUM, FAST, FASTEST
 from requests.exceptions import ConnectionError
 from web3 import Web3
 
 from nucypher.utilities.datafeeds import (
     EtherchainGasPriceDatafeed,
     Datafeed,
-    UpvestGasPriceDatafeed
-)
+    UpvestGasPriceDatafeed,
+    EthereumGasPriceDatafeed)
 from nucypher.utilities.gas_strategies import datafeed_fallback_gas_price_strategy
 
 etherchain_json = {
@@ -76,6 +77,41 @@ def test_probe_datafeed(mocker):
         assert feed._raw_data == json
 
 
+def test_canonical_speed_names():
+    # Valid speed names, grouped in equivalence classes
+    speed_equivalence_classes = {
+        SLOW: ('slow', 'SLOW', 'Slow',
+               'safeLow', 'safelow', 'SafeLow', 'SAFELOW',
+               'low', 'LOW', 'Low'),
+        MEDIUM: ('medium', 'MEDIUM', 'Medium',
+                 'standard', 'STANDARD', 'Standard',
+                 'average', 'AVERAGE', 'Average'),
+        FAST: ('fast', 'FAST', 'Fast',
+               'high', 'HIGH', 'High'),
+        FASTEST: ('fastest', 'FASTEST', 'Fastest')
+    }
+
+    for canonical_speed, equivalence_class in speed_equivalence_classes.items():
+        for speed_name in equivalence_class:
+            assert canonical_speed == EthereumGasPriceDatafeed.get_canonical_speed(speed_name)
+
+    # Invalid speed names, but that are somewhat similar to a valid one so we can give a suggestion
+    similarities = (
+        ('hihg', 'high'),
+        ('zlow', 'low'),
+    )
+
+    for wrong_name, suggestion in similarities:
+        message = f"'{wrong_name}' is not a valid speed name. Did you mean '{suggestion}'?"
+        with pytest.raises(LookupError, match=message):
+            EthereumGasPriceDatafeed.get_canonical_speed(wrong_name)
+
+    # Utterly wrong speed names. Shame on you.
+    wrong_name = "🙈"
+    with pytest.raises(LookupError, match=f"'{wrong_name}' is not a valid speed name."):
+        EthereumGasPriceDatafeed.get_canonical_speed(wrong_name)
+
+
 def test_etherchain():
     feed = EtherchainGasPriceDatafeed()