feat: expand forkChoiceUpdatedV3 with basic block building (#540)

**Motivation**

Add basic block building to forkChoiceUpdatedV3

<!-- Why does this pull request exist? What are its goals? -->

**Description**

* Expand engine_forkChoiceUpdated:
   - Add validations
   - Fix fork state update conditions
   - Add basic block building

With these changes hive engine tests no longer fail after calling
engine_forkChoiceUpdatedV3. We still need to implement engine_getPayload
to progress further
NOTE: Some fixes over this code have been included in #571 (Computing
the state root for newly built payloads instead of using the parent
state root)
<!-- A clear and concise general description of the changes this PR
introduces -->

<!-- Link to issues: Resolves #111, Resolves #222 -->

Closes None, is part of #344

crates/blockchain/Cargo.toml

@@ -8,8 +8,10 @@ edition = "2021"
 [dependencies]
 thiserror.workspace = true
 ethereum_rust-core.workspace = true
+ethereum_rust-rlp.workspace = true
 ethereum_rust-storage.workspace = true
 ethereum_rust-evm.workspace = true
+sha3.workspace = true
 
 
 [lib]

crates/blockchain/blockchain.rs

@@ -1,6 +1,8 @@
 pub mod constants;
 pub mod error;
 pub mod mempool;
+pub mod payload;
+
 use constants::{GAS_PER_BLOB, MAX_BLOB_GAS_PER_BLOCK, MAX_BLOB_NUMBER_PER_BLOCK};
 use error::{ChainError, InvalidBlockError};
 use ethereum_rust_core::types::{

crates/blockchain/constants.rs

@@ -55,3 +55,7 @@ pub const MAX_BLOB_GAS_PER_BLOCK: u64 = MAX_BLOB_NUMBER_PER_BLOCK * GAS_PER_BLOB
 
 // Minimum base fee per blob
 pub const MIN_BASE_FEE_PER_BLOB_GAS: u64 = 1;
+
+pub const GAS_LIMIT_BOUND_DIVISOR: u64 = 1024;
+
+pub const MIN_GAS_LIMIT: u64 = 5000;

crates/blockchain/payload.rs

@@ -0,0 +1,129 @@
+use std::cmp::min;
+
+use ethereum_rust_core::{
+    types::{
+        calculate_base_fee_per_gas, compute_receipts_root, compute_transactions_root,
+        compute_withdrawals_root, Block, BlockBody, BlockHash, BlockHeader, Withdrawal,
+        DEFAULT_OMMERS_HASH,
+    },
+    Address, Bloom, Bytes, H256, U256,
+};
+use ethereum_rust_rlp::encode::RLPEncode;
+use ethereum_rust_storage::{error::StoreError, Store};
+use sha3::{Digest, Keccak256};
+
+use crate::constants::{GAS_LIMIT_BOUND_DIVISOR, MIN_GAS_LIMIT, TARGET_BLOB_GAS_PER_BLOCK};
+
+pub struct BuildPayloadArgs {
+    pub parent: BlockHash,
+    pub timestamp: u64,
+    pub fee_recipient: Address,
+    pub random: H256,
+    pub withdrawals: Vec<Withdrawal>,
+    pub beacon_root: Option<H256>,
+    pub version: u8,
+}
+
+impl BuildPayloadArgs {
+    /// Computes an 8-byte identifier by hashing the components of the payload arguments.
+    pub fn id(&self) -> u64 {
+        let mut hasher = Keccak256::new();
+        hasher.update(self.parent);
+        hasher.update(self.timestamp.to_be_bytes());
+        hasher.update(self.random);
+        hasher.update(self.fee_recipient);
+        hasher.update(self.withdrawals.encode_to_vec());
+        if let Some(beacon_root) = self.beacon_root {
+            hasher.update(beacon_root);
+        }
+        let res = &mut hasher.finalize()[..8];
+        res[0] = self.version;
+        u64::from_be_bytes(res.try_into().unwrap())
+    }
+}
+
+/// Builds a new payload based on the payload arguments
+// Basic payload block building, can and should be improved
+pub fn build_payload(args: &BuildPayloadArgs, storage: &Store) -> Result<Block, StoreError> {
+    // TODO: check where we should get builder values from
+    const DEFAULT_BUILDER_GAS_CEIL: u64 = 30_000_000;
+    // Presence of a parent block should have been checked or guaranteed before calling this function
+    // So we can treat a missing parent block as an internal storage error
+    let parent_block = storage
+        .get_block_header_by_hash(args.parent)?
+        .ok_or_else(|| StoreError::Custom("unexpected missing parent block".to_string()))?;
+    let chain_config = storage.get_chain_config()?;
+    let gas_limit = calc_gas_limit(parent_block.gas_limit, DEFAULT_BUILDER_GAS_CEIL);
+    Ok(Block {
+        header: BlockHeader {
+            parent_hash: args.parent,
+            ommers_hash: *DEFAULT_OMMERS_HASH,
+            coinbase: args.fee_recipient,
+            state_root: parent_block.state_root,
+            transactions_root: compute_transactions_root(&[]),
+            receipts_root: compute_receipts_root(&[]),
+            logs_bloom: Bloom::default(),
+            difficulty: U256::zero(),
+            number: parent_block.number.saturating_add(1),
+            gas_limit,
+            gas_used: 0,
+            timestamp: args.timestamp,
+            // TODO: should use builder config's extra_data
+            extra_data: Bytes::new(),
+            prev_randao: args.random,
+            nonce: 0,
+            base_fee_per_gas: calculate_base_fee_per_gas(
+                gas_limit,
+                parent_block.gas_limit,
+                parent_block.gas_used,
+                parent_block.base_fee_per_gas.unwrap_or_default(),
+            ),
+            withdrawals_root: chain_config
+                .is_shanghai_activated(args.timestamp)
+                .then_some(compute_withdrawals_root(&args.withdrawals)),
+            blob_gas_used: Some(0),
+            excess_blob_gas: chain_config.is_cancun_activated(args.timestamp).then_some(
+                calc_excess_blob_gas(
+                    parent_block.excess_blob_gas.unwrap_or_default(),
+                    parent_block.blob_gas_used.unwrap_or_default(),
+                ),
+            ),
+            parent_beacon_block_root: args.beacon_root,
+        },
+        // Empty body as we just created this payload
+        body: BlockBody {
+            transactions: Vec::new(),
+            ommers: Vec::new(),
+            withdrawals: Some(args.withdrawals.clone()),
+        },
+    })
+}
+
+fn calc_gas_limit(parent_gas_limit: u64, desired_limit: u64) -> u64 {
+    let delta = parent_gas_limit / GAS_LIMIT_BOUND_DIVISOR - 1;
+    let mut limit = parent_gas_limit;
+    let desired_limit = min(desired_limit, MIN_GAS_LIMIT);
+    if limit < desired_limit {
+        limit = parent_gas_limit + delta;
+        if limit > desired_limit {
+            limit = desired_limit
+        }
+        return limit;
+    }
+    if limit > desired_limit {
+        limit = parent_gas_limit - delta;
+        if limit < desired_limit {
+            limit = desired_limit
+        }
+    }
+    limit
+}
+
+fn calc_excess_blob_gas(parent_excess_blob_gas: u64, parent_blob_gas_used: u64) -> u64 {
+    let excess_blob_gas = parent_excess_blob_gas + parent_blob_gas_used;
+    if excess_blob_gas < TARGET_BLOB_GAS_PER_BLOCK {
+        0
+    } else {
+        excess_blob_gas - TARGET_BLOB_GAS_PER_BLOCK
+    }
+}

crates/core/serde_utils.rs

@@ -99,10 +99,7 @@ pub mod u64 {
         where
             D: Deserializer<'de>,
         {
-            let value = String::deserialize(d)?;
-            let res = u64::from_str_radix(value.trim_start_matches("0x"), 16)
-                .map_err(|_| D::Error::custom("Failed to deserialize u64 value"));
-            res
+            super::hex_str::deserialize(d)
         }
 
         pub fn serialize<S>(value: &u64, serializer: S) -> Result<S::Ok, S::Error>
@@ -139,6 +136,25 @@ pub mod u64 {
         }
     }
 
+    pub mod hex_str_opt_padded {
+        use serde::Serialize;
+
+        use super::*;
+        pub fn serialize<S>(value: &Option<u64>, serializer: S) -> Result<S::Ok, S::Error>
+        where
+            S: Serializer,
+        {
+            Option::<String>::serialize(&value.map(|v| format!("{:#018x}", v)), serializer)
+        }
+
+        pub fn deserialize<'de, D>(d: D) -> Result<Option<u64>, D::Error>
+        where
+            D: Deserializer<'de>,
+        {
+            super::hex_str_opt::deserialize(d)
+        }
+    }
+
     pub fn deser_dec_str<'de, D>(d: D) -> Result<u64, D::Error>
     where
         D: Deserializer<'de>,

crates/core/types/block.rs

@@ -339,7 +339,7 @@ fn fake_exponential(factor: u64, numerator: u64, denominator: u64) -> u64 {
 
 // Calculates the base fee for the current block based on its gas_limit and parent's gas and fee
 // Returns None if the block gas limit is not valid in relation to its parent's gas limit
-fn calculate_base_fee_per_gas(
+pub fn calculate_base_fee_per_gas(
     block_gas_limit: u64,
     parent_gas_limit: u64,
     parent_gas_used: u64,