Simplified validate_header func in post-merge forks (#1163)

* Simplified validate_header func in post-merge forks

* Simplified parent hash calculation in post-merge forks

* validate_header modification in paris and prague forks

* fix formatting

---------

Co-authored-by: Guruprasad Kamath <[email protected]>

Author: Antrikshgwal

src/ethereum/cancun/fork.py

@@ -310,19 +310,8 @@ def validate_header(chain: BlockChain, header: Header) -> None:
     """
     if header.number < Uint(1):
         raise InvalidBlock
-    parent_header_number = header.number - Uint(1)
-    first_block_number = chain.blocks[0].header.number
-    last_block_number = chain.blocks[-1].header.number
 
-    if (
-        parent_header_number < first_block_number
-        or parent_header_number > last_block_number
-    ):
-        raise InvalidBlock
-
-    parent_header = chain.blocks[
-        parent_header_number - first_block_number
-    ].header
+    parent_header = chain.blocks[-1].header
 
     excess_blob_gas = calculate_excess_blob_gas(parent_header)
     if header.excess_blob_gas != excess_blob_gas:

src/ethereum/paris/fork.py

@@ -284,19 +284,8 @@ def validate_header(chain: BlockChain, header: Header) -> None:
     """
     if header.number < Uint(1):
         raise InvalidBlock
-    parent_header_number = header.number - Uint(1)
-    first_block_number = chain.blocks[0].header.number
-    last_block_number = chain.blocks[-1].header.number
-
-    if (
-        parent_header_number < first_block_number
-        or parent_header_number > last_block_number
-    ):
-        raise InvalidBlock
 
-    parent_header = chain.blocks[
-        parent_header_number - first_block_number
-    ].header
+    parent_header = chain.blocks[-1].header
 
     if header.gas_used > header.gas_limit:
         raise InvalidBlock

src/ethereum/prague/fork.py

@@ -333,19 +333,8 @@ def validate_header(chain: BlockChain, header: Header) -> None:
     """
     if header.number < Uint(1):
         raise InvalidBlock
-    parent_header_number = header.number - Uint(1)
-    first_block_number = chain.blocks[0].header.number
-    last_block_number = chain.blocks[-1].header.number
 
-    if (
-        parent_header_number < first_block_number
-        or parent_header_number > last_block_number
-    ):
-        raise InvalidBlock
-
-    parent_header = chain.blocks[
-        parent_header_number - first_block_number
-    ].header
+    parent_header = chain.blocks[-1].header
 
     excess_blob_gas = calculate_excess_blob_gas(parent_header)
     if header.excess_blob_gas != excess_blob_gas:

src/ethereum/shanghai/fork.py

@@ -289,19 +289,8 @@ def validate_header(chain: BlockChain, header: Header) -> None:
     """
     if header.number < Uint(1):
         raise InvalidBlock
-    parent_header_number = header.number - Uint(1)
-    first_block_number = chain.blocks[0].header.number
-    last_block_number = chain.blocks[-1].header.number
-
-    if (
-        parent_header_number < first_block_number
-        or parent_header_number > last_block_number
-    ):
-        raise InvalidBlock
 
-    parent_header = chain.blocks[
-        parent_header_number - first_block_number
-    ].header
+    parent_header = chain.blocks[-1].header
 
     if header.gas_used > header.gas_limit:
         raise InvalidBlock