1 files changed, 60 insertions, 19 deletions

diff --git a/src/hash_chain.rs b/src/hash_chain.rs
index b87ac61..4a37c67 100644
--- a/src/hash_chain.rs
+++ b/src/hash_chain.rs
@@ -35,48 +35,89 @@ impl<T: Encode> HashChain<T> {
             })
             .unwrap_or_default();
         self.data
-            .push((Self::hash(&prev_hash, &data), data));
+            .push((Self::with_hash((&prev_hash, &data)), data));
     }
 
-    fn insert(&mut self, data: T, base_hash: &[u8]) {
+    // TODO: make try_last that does same as this but returns Err() if it's not the
+    // last one and/or refuse to insert
+    fn insert(&mut self, data: T, base_hash: &Vec<u8>) {
         let pos = self
             .data
             .iter()
-            .position(|x| x.0 == base_hash)
+            .position(|x| x.0 == *base_hash)
             .unwrap();
         self.data
-            .insert(pos, (Self::hash(base_hash, &data), data));
+            .insert(pos + 1, (Self::with_hash((base_hash, &data)), data));
+
+        // everything after that hash is invalidated
+        self.rehash(&base_hash);
+    }
+
+    fn verify(&self, until_hash: &[u8]) -> bool {
+        let pos = self
+            .data
+            .iter()
+            .position(|x| x.0 == until_hash)
+            .unwrap();
+        self.data[pos..=1]
+            .iter()
+            .enumerate()
+            .all(|(prev_hash, (pred_prev_hash, _))| {
+                let prev_hash = Self::with_hash({
+                    let prev_hash = &self.data[prev_hash - 1];
+                    (&prev_hash.0, &prev_hash.1)
+                });
+                prev_hash == *pred_prev_hash
+            })
     }
 
-    fn verify(&self, from_hash: &[u8]) -> bool {
-        let i = self
+    fn rehash(&mut self, from_hash: &[u8]) {
+        let pos = self
             .data
             .iter()
-            .position(|x| x.0 == from_hash)
+            .position(|x| x.0 == *from_hash)
             .unwrap();
-        (i..self
+
+        let prev_hashes: Vec<_> = (pos..self
             .data
             .len())
-            .all(|i| {
-                Self::hash(
-                    if i == 0 {
-                        &[]
-                    } else {
-                        &self.data[i - 1].0
-                    },
-                    &self.data[i].1,
-                ) == self.data[i].0
+            .map(|i| {
+                Self::with_hash({
+                    let prev_hash = &self.data[i - 1];
+                    (&prev_hash.0, &prev_hash.1)
+                })
             })
+            .collect();
+
+        self.data[pos..]
+            .iter_mut()
+            .enumerate()
+            .map(|(idx, item)| (item, prev_hashes[idx].clone()))
+            .for_each(|((pred_prev_hash, _), prev_hash)| {
+                if prev_hash != *pred_prev_hash {
+                    *pred_prev_hash = prev_hash;
+                }
+            });
     }
 
-    fn hash(prev_hash: &[u8], data: &T) -> Vec<u8> {
+    fn with_hash(data: (&Vec<u8>, &T)) -> Vec<u8> {
         let mut hasher = Sha256::new();
-        hasher.update(prev_hash);
         hasher.update(bincode::encode_to_vec(data, bincode::config::standard()).unwrap());
         hasher
             .finalize()
             .to_vec()
     }
+
+    fn hash_last(&self) -> Vec<u8> {
+        Self::with_hash({
+            let last = self
+                .data
+                .iter()
+                .last()
+                .unwrap();
+            (&last.0, &last.1)
+        })
+    }
 }
 
 impl<T: Encode> Deref for HashChain<T> {