Compute 4 Byte selector from SolError and SolFunction

crates/ast/src/util.rs

@@ -1,4 +1,7 @@
-use alloy_primitives::U256;
+use crate::ast::{SolError, SolFunction};
+use crate::Spanned;
+use alloy_dyn_abi::DynSolType;
+use alloy_primitives::{keccak256, FixedBytes, U256};
 use evm_glue::opcodes::Opcode;
 
 pub(crate) fn u256_as_push_data<const N: usize>(value: U256) -> Result<[u8; N], String> {
@@ -53,3 +56,34 @@ pub fn u256_as_push(value: U256) -> Opcode {
         _ => unreachable!(),
     }
 }
+
+type Selector = (FixedBytes<4>, FixedBytes<4>);
+
+pub fn compute_selector(name: &Spanned<&str>, args: &Box<[Spanned<DynSolType>]>) -> FixedBytes<4> {
+    let build_signature = |name: &Spanned<&str>, args: &Box<[Spanned<DynSolType>]>| -> Vec<u8> {
+        let arg_types: Vec<String> = args
+            .iter()
+            .map(|arg| {
+                let type_str = arg.0.to_string();
+                type_str
+            })
+            .collect();
+
+        let mut signature = String::new();
+        signature.push_str(name.0);
+        signature.push('(');
+        signature.push_str(&arg_types.join(","));
+        signature.push(')');
+
+        signature.into_bytes()
+    };
+
+    let signature = build_signature(name, args);
+
+    let hash = keccak256(signature);
+
+    let selector = FixedBytes::<4>::from_slice(&hash[..4]);
+
+    selector
+}
+