1 files changed, 70 insertions, 0 deletions
diff --git a/src/policies/reference_update.rs b/src/policies/reference_update.rs
new file mode 100644
index 0000000..deb7b8f
--- /dev/null
+++ b/src/policies/reference_update.rs
@@ -0,0 +1,70 @@
+use crate::error::CapnError;
+use git2::Oid;
+use std::error::Error;
+
+pub enum ReferenceUpdate {
+    New {
+        new_commit_id: Oid,
+        ref_name: String,
+    },
+    Delete {
+        old_commit_id: Oid,
+        ref_name: String,
+    },
+    Update {
+        old_commit_id: Oid,
+        new_commit_id: Oid,
+        ref_name: String,
+    },
+}
+
+impl ReferenceUpdate {
+    pub fn from_git_hook_format(
+        old_commit_id: &str,
+        new_commit_id: &str,
+        ref_name: &str,
+    ) -> Result<ReferenceUpdate, Box<dyn Error>> {
+        let old_commit_id = Oid::from_str(old_commit_id)?;
+        let new_commit_id = Oid::from_str(new_commit_id)?;
+        let ref_name = ref_name.to_owned();
+        match (old_commit_id.is_zero(), new_commit_id.is_zero()) {
+            (false, false) => Ok(ReferenceUpdate::Update {
+                old_commit_id,
+                new_commit_id,
+                ref_name,
+            }),
+            (false, true) => Ok(ReferenceUpdate::Delete {
+                old_commit_id,
+                ref_name,
+            }),
+            (true, false) => Ok(ReferenceUpdate::New {
+                new_commit_id,
+                ref_name,
+            }),
+            (true, true) => Err(Box::new(CapnError::new("Invalid reference update specification, trying to update from a zero commit to another zero commit")))
+        }
+    }
+
+    pub fn old_commit_id(&self) -> Option<Oid> {
+        use self::ReferenceUpdate::*;
+        match self {
+            Delete { old_commit_id, .. } | Update { old_commit_id, .. } => Some(*old_commit_id),
+            _ => None,
+        }
+    }
+
+    pub fn new_commit_id(&self) -> Option<Oid> {
+        use self::ReferenceUpdate::*;
+        match self {
+            New { new_commit_id, .. } | Update { new_commit_id, .. } => Some(*new_commit_id),
+            _ => None,
+        }
+    }
+
+    pub fn ref_name(&self) -> &str {
+        use self::ReferenceUpdate::*;
+        match self {
+            New { ref_name, .. } | Delete { ref_name, .. } | Update { ref_name, .. } => ref_name,
+        }
+    }
+}