From 63a4aee524b55b2954fe3968ddf2e1d7b8e8b923 Mon Sep 17 00:00:00 2001
From: Matthias Seitz <matthias.seitz@outlook.de>
Date: Fri, 20 Sep 2024 11:41:29 +0200
Subject: [PATCH] feat: add SystemCaller helper type

---
 crates/evm/src/system_calls/mod.rs | 76 ++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/crates/evm/src/system_calls/mod.rs b/crates/evm/src/system_calls/mod.rs
index 50d5c4c857ff..ec91779e7c71 100644
--- a/crates/evm/src/system_calls/mod.rs
+++ b/crates/evm/src/system_calls/mod.rs
@@ -1,7 +1,9 @@
 //! System contract call functions.
 
 mod eip2935;
+
 pub use eip2935::*;
+use revm_primitives::ResultAndState;
 
 mod eip4788;
 pub use eip4788::*;
@@ -11,3 +13,77 @@ pub use eip7002::*;
 
 mod eip7251;
 pub use eip7251::*;
+use reth_execution_errors::BlockExecutionError;
+
+/// A hook that is called after each state change.
+// TODO impl for &mut
+pub trait OnStateHook {
+    /// Invoked with the result and state after each system call.
+    fn on_state(&mut self, state: &ResultAndState);
+}
+
+impl<F> OnStateHook for F
+where
+    F: FnMut(&ResultAndState),
+{
+    fn on_state(&mut self, state: &ResultAndState) {
+        self(state)
+    }
+}
+
+/// An [`OnStateHook`] that does nothing.
+#[derive(Default, Debug, Clone)]
+#[non_exhaustive]
+pub struct NoopHook;
+
+impl OnStateHook for NoopHook {
+    fn on_state(&mut self, _state: &ResultAndState) {}
+}
+
+/// An ephemeral helper type for executing system calls.
+///
+/// This can be used to chain system transaction calls.
+#[derive(Debug)]
+pub struct SystemCaller<EvmConfig, DB, Chainspec, Hook = NoopHook> {
+    evm_config: EvmConfig,
+    db: DB,
+    chain_spec: Chainspec,
+    /// Optional hook to be called after each state change.
+    // TODO do we want this optional?
+    hook: Option<Hook>,
+}
+
+impl<EvmConfig, DB, Chainspec> SystemCaller<EvmConfig, DB, Chainspec> {
+    /// Create a new system caller with the given EVM config, database, and chain spec.
+    pub fn new(evm_config: EvmConfig, db: DB, chain_spec: Chainspec) -> Self {
+        Self { evm_config, db, chain_spec, hook: None }
+    }
+}
+
+impl<EvmConfig, DB, Chainspec, Hook> SystemCaller<EvmConfig, DB, Chainspec, Hook> {
+    /// Installs a custom hook to be called after each state change.
+    pub fn with_state_hook<H: OnStateHook>(
+        self,
+        hook: H,
+    ) -> SystemCaller<EvmConfig, DB, Chainspec, H> {
+        let Self { evm_config, db, chain_spec, .. } = self;
+        SystemCaller { evm_config, db, chain_spec, hook: Some(hook) }
+    }
+    /// Convenience type to consume the type and drop borrowed fields
+    pub fn finish(self) {}
+}
+
+impl<EvmConfig, DB, Chainspec, Hook> SystemCaller<EvmConfig, DB, Chainspec, Hook> {
+    // TODO add apply functions that are chainable
+
+    /// Applies the pre-block call to the EIP-2935 blockhashes contract.
+    pub fn pre_block_blockhashes_contract_call(self) -> Result<Self, BlockExecutionError> {
+        // TODO:
+        // transact
+        // apply hook
+        // commit
+        todo!()
+    }
+
+    // TODO add other system calls
+}