refactor: add test and checked APIs for slot calculator

Cargo.toml

@@ -4,7 +4,7 @@ name = "init4-bin-base"
 description = "Internal utilities for binaries produced by the init4 team"
 keywords = ["init4", "bin", "base"]
 
-version = "0.5.1"
+version = "0.5.2"
 edition = "2021"
 rust-version = "1.81"
 authors = ["init4", "James Prestwich"]

src/perms/builders.rs

@@ -135,29 +135,36 @@ impl Builders {
 
     /// Get the builder permissioned at a specific timestamp.
     pub fn builder_at_timestamp(&self, timestamp: u64) -> &Builder {
-        self.builder_at(self.index(timestamp) as usize)
+        self.builder_at(self.index(timestamp))
     }
 
     /// Get the index of the builder that is allowed to sign a block for a
     /// particular timestamp.
-    pub fn index(&self, timestamp: u64) -> u64 {
-        self.config.calc().calculate_slot(timestamp) % self.builders.len() as u64
+    pub fn index(&self, timestamp: u64) -> usize {
+        self.config
+            .calc()
+            .slot_containing(timestamp)
+            .expect("host chain has started")
+            % self.builders.len()
     }
 
     /// Get the index of the builder that is allowed to sign a block at the
     /// current timestamp.
-    pub fn index_now(&self) -> u64 {
+    pub fn index_now(&self) -> usize {
         self.index(now())
     }
 
     /// Get the builder that is allowed to sign a block at the current timestamp.
     pub fn current_builder(&self) -> &Builder {
-        self.builder_at(self.index_now() as usize)
+        self.builder_at(self.index_now())
     }
 
     /// Check the query bounds for the current timestamp.
     fn check_query_bounds(&self) -> Result<(), BuilderPermissionError> {
-        let current_slot_time = self.calc().current_timepoint_within_slot();
+        let current_slot_time = self
+            .calc()
+            .current_point_within_slot()
+            .expect("host chain has started");
         if current_slot_time < self.config.block_query_start() {
             return Err(BuilderPermissionError::ActionAttemptTooEarly);
         }

src/perms/middleware.rs

@@ -162,8 +162,11 @@ where
                 permissioned_builder = this.builders.current_builder().sub(),
                 requesting_builder = tracing::field::Empty,
                 current_slot = this.builders.calc().current_slot(),
-                current_timepoint_within_slot =
-                    this.builders.calc().current_timepoint_within_slot(),
+                current_timepoint_within_slot = this
+                    .builders
+                    .calc()
+                    .current_point_within_slot()
+                    .expect("host chain has started"),
                 permissioning_error = tracing::field::Empty,
             );