🔨 Add Rule type + module to durin_primitives

crates/primitives/src/lib.rs

@@ -11,3 +11,6 @@ pub use dispute_game::{Claim, GameStatus, GameType};
 
 mod traits;
 pub use traits::{DisputeGame, DisputeSolver};
+
+#[cfg(test)]
+pub mod rule;

crates/primitives/src/rule.rs

@@ -0,0 +1,84 @@
+//! This module contains the [Rule] type as well as several helper macros for applying
+//! rules on top of one another.
+
+type Rule<T> = Box<dyn Fn(T) -> anyhow::Result<T>>;
+
+#[macro_export]
+macro_rules! chain_rules {
+    ($state:expr, $($rule:expr),+) => {{
+        let mut result = Ok($state);
+
+        $(
+            result = match result {
+                Ok(val) => $rule(val),
+                err @ Err(_) => err,
+            };
+        )+
+
+        result
+    }};
+}
+
+mod test {
+    use super::*;
+
+    #[test]
+    fn apply_sequential_rules() {
+        let state = 5;
+
+        let rule_lt_10: Rule<u32> = Box::new(|state: u32| {
+            if state < 10 {
+                Ok(state)
+            } else {
+                Err(anyhow::anyhow!("state must be less than 10"))
+            }
+        });
+        let rule_double_10: Rule<u32> = Box::new(|state: u32| {
+            if state * 2 == 10 {
+                Ok(state)
+            } else {
+                Err(anyhow::anyhow!("state must be half of 10"))
+            }
+        });
+        let rule_bitwise: Rule<u32> = Box::new(|state: u32| {
+            if state & 0xF == 0b0101 {
+                Ok(state)
+            } else {
+                Err(anyhow::anyhow!("state must be 5"))
+            }
+        });
+
+        let result = chain_rules!(state, rule_lt_10, rule_double_10, rule_bitwise);
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn fail_sequential_rules() {
+        let state = 5;
+
+        let rule_lt_10: Rule<u32> = Box::new(|state: u32| {
+            if state < 10 {
+                Ok(state)
+            } else {
+                Err(anyhow::anyhow!("state must be less than 10"))
+            }
+        });
+        let rule_double_11: Rule<u32> = Box::new(|state: u32| {
+            if state * 2 == 11 {
+                Ok(state)
+            } else {
+                Err(anyhow::anyhow!("state must be half of 11"))
+            }
+        });
+        let rule_bitwise: Rule<u32> = Box::new(|state: u32| {
+            if state & 0xF == 0b0101 {
+                Ok(state)
+            } else {
+                Err(anyhow::anyhow!("state must be 5"))
+            }
+        });
+
+        let result = chain_rules!(state, rule_lt_10, rule_double_11, rule_bitwise);
+        assert!(result.is_err());
+    }
+}