Safe head

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "sw-utils"
-version = "v0.6.21"
+version = "v0.6.22"
 description = "StakeWise Python utils"
 authors = ["StakeWise Labs <[email protected]>"]
 license = "GPL-3.0-or-later"

sw_utils/consensus.py

@@ -208,10 +208,9 @@ def get_consensus_client(
 async def get_chain_finalized_head(
     consensus_client: ExtendedAsyncBeacon,
     slots_per_epoch: int,
-    state: str = 'finalized',
 ) -> ChainHead:
-    """Fetches the fork safe chain head."""
-    block_data = await consensus_client.get_block(state)
+    """Fetches the fork finalized chain head."""
+    block_data = await consensus_client.get_block('finalized')
     slot = int(block_data['data']['message']['slot'])
 
     return ChainHead(
@@ -226,14 +225,42 @@ async def get_chain_finalized_head(
     )
 
 
+async def get_chain_justified_head(
+    consensus_client: ExtendedAsyncBeacon,
+    slots_per_epoch: int,
+) -> ChainHead:
+    """Fetches the fork safe chain head."""
+    checkpoints = await consensus_client.get_finality_checkpoint()
+    epoch: int = int(checkpoints['data']['current_justified']['epoch'])
+    last_slot_id: int = epoch * slots_per_epoch
+    for i in range(slots_per_epoch):
+        try:
+            slot = await consensus_client.get_block(str(last_slot_id - i))
+        except ClientResponseError as e:
+            if hasattr(e, 'status') and e.status == 404:
+                # slot was not proposed, try the previous one
+                continue
+            raise e
+
+        execution_payload = slot['data']['message']['body']['execution_payload']
+        return ChainHead(
+            epoch=epoch,
+            slot=last_slot_id - i,
+            block_number=BlockNumber(int(execution_payload['block_number'])),
+            execution_ts=Timestamp(int(execution_payload['timestamp'])),
+        )
+
+    raise RuntimeError(f'Failed to fetch slot for epoch {epoch}')
+
+
 async def get_chain_epoch_head(
     epoch: int,
     slots_per_epoch: int,
     execution_client: AsyncWeb3,
     consensus_client: ExtendedAsyncBeacon,
 ) -> ChainHead:
     """Fetches the epoch chain head."""
-    slot_id: int = (epoch * slots_per_epoch) + slots_per_epoch - 1
+    slot_id: int = epoch * slots_per_epoch
     for i in range(slots_per_epoch):
         try:
             slot = await consensus_client.get_block(str(slot_id - i))

sw_utils/typings.py

@@ -24,14 +24,6 @@ class ChainHead:
     block_number: BlockNumber
     execution_ts: Timestamp
 
-    @property
-    def consensus_block(self) -> int:
-        return self.slot
-
-    @property
-    def execution_block(self) -> BlockNumber:
-        return self.block_number
-
 
 @dataclass
 class Oracle: