From a54046f51ec00aab7a4f3a35e67b7422d92db98b Mon Sep 17 00:00:00 2001
From: littleblack111 <littleblack11111@gmail.com>
Date: Wed, 22 Oct 2025 11:37:35 +0800
Subject: feat: actual hash_chain

---
 src/hash_chain.rs | 71 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs        |  2 ++
 2 files changed, 73 insertions(+)
 create mode 100644 src/hash_chain.rs

diff --git a/src/hash_chain.rs b/src/hash_chain.rs
new file mode 100644
index 0000000..2079e1c
--- /dev/null
+++ b/src/hash_chain.rs
@@ -0,0 +1,71 @@
+use std::ops::Deref;
+
+use bincode::Encode;
+use sha2::{Digest, Sha256};
+
+pub struct HashChain<T: Encode> {
+    data: Vec<(Vec<u8>, T)>, // Vector of (hash, value) pairs
+}
+
+impl<T: Encode> HashChain<T> {
+    fn push(&mut self, data: T) {
+        let prev_hash = self
+            .data
+            .last()
+            .map(|p| {
+                p.0.clone()
+            })
+            .unwrap_or_default();
+        self.data
+            .push((Self::hash(&prev_hash, &data), data));
+    }
+
+    fn insert(&mut self, data: T, base_hash: &[u8]) {
+        let pos = self
+            .data
+            .iter()
+            .position(|x| x.0 == base_hash)
+            .unwrap();
+        self.data
+            .insert(pos, (Self::hash(base_hash, &data), data));
+    }
+
+    fn verify(&self, from_hash: &[u8]) -> bool {
+        let start_idx = self
+            .data
+            .iter()
+            .position(|x| x.0 == from_hash)
+            .unwrap();
+        (start_idx
+            ..self
+                .data
+                .len())
+            .all(|i| {
+                Self::hash(
+                    if i == 0 {
+                        &Vec::default()
+                    } else {
+                        &self.data[i - 1].0
+                    },
+                    &self.data[i].1,
+                ) == self.data[i].0
+            })
+    }
+
+    fn hash(prev_hash: &[u8], data: &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()
+    }
+}
+
+impl<T: Encode> Deref for HashChain<T> {
+    type Target = Vec<(Vec<u8>, T)>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.data
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 9cdbdcd..1ee9fc2 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,5 @@
+pub mod hash_chain;
+
 pub mod blocks;
 
 pub mod transaction;
-- 
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