chore: add depth to GasInspector (#1922)

* chore: Simplify GasInspector

* fmt

* chore: add depth to GasInspector

* rm doc

crates/inspector/src/gas.rs

@@ -1,13 +1,14 @@
 //! GasIspector. Helper Inspector to calculate gas for others.
-
 use revm::interpreter::{CallOutcome, CreateOutcome, Gas};
 
-/// Helper [Inspector] that keeps track of gas.
+/// Helper that keeps track of gas.
 #[allow(dead_code)]
 #[derive(Clone, Copy, Debug)]
 pub struct GasInspector {
     gas_remaining: u64,
     last_gas_cost: u64,
+    /// depth
+    depth: usize,
 }
 
 impl Default for GasInspector {
@@ -29,11 +30,10 @@ impl GasInspector {
         Self {
             gas_remaining: 0,
             last_gas_cost: 0,
+            depth: 0,
         }
     }
-}
 
-impl GasInspector {
     #[inline]
     pub fn initialize_interp(&mut self, gas: &Gas) {
         self.gas_remaining = gas.limit();
@@ -66,6 +66,24 @@ impl GasInspector {
             self.gas_remaining = 0;
         }
     }
+
+    /// Returns depth
+    #[inline]
+    pub fn depth(&self) -> usize {
+        self.depth
+    }
+
+    /// Increment depth
+    #[inline]
+    pub fn incr_depth(&mut self) {
+        self.depth += 1;
+    }
+
+    /// Decrement depth
+    #[inline]
+    pub fn decr_depth(&mut self) {
+        self.depth -= 1;
+    }
 }
 
 // #[cfg(test)]