From 24df2644b74197440c3c663f62deb38b4ab563e9 Mon Sep 17 00:00:00 2001
From: rustaceanrob <rob.netzke@gmail.com>
Date: Mon, 3 Jun 2024 14:39:16 -1000
Subject: [PATCH] chain: extend fn MSRV

---
 src/chain/header_chain.rs | 41 ++++++++++++++++-----------------------
 src/lib.rs                |  4 ++--
 2 files changed, 19 insertions(+), 26 deletions(-)

diff --git a/src/chain/header_chain.rs b/src/chain/header_chain.rs
index 1f0a6a9..bc4177c 100644
--- a/src/chain/header_chain.rs
+++ b/src/chain/header_chain.rs
@@ -154,7 +154,7 @@ impl HeaderChain {
         locators
     }
 
-    // Extend the current chain, potentially rewriting history
+    // Extend the current chain, potentially rewriting history. Higher order functions should decide what we extend
     pub(crate) fn extend(&mut self, batch: &[Header]) -> Vec<DisconnectedHeader> {
         let mut reorged = Vec::new();
         // We cannot extend from nothing
@@ -180,38 +180,31 @@ impl HeaderChain {
                     .expect("cannot extend from empty batch")
                     .prev_blockhash
             ));
-            while let Some((height, header)) = self.headers.iter_mut().next_back() {
+            // Supporting MSRV of 1.63 requires this round-about way of removing the headers instead of `pop_last`
+            // Find the header that matches the new batch prev block hash, collecting the disconnected headers
+            for (height, header) in self.headers.iter().rev() {
                 if header.block_hash().ne(&batch
                     .first()
                     .expect("cannot extend from empty batch")
                     .prev_blockhash)
                 {
-                    reorged.push(DisconnectedHeader::new(*height, *header));
+                    reorged.push(DisconnectedHeader::new(*height, header.block_hash()));
                 } else {
-                    let anchor_height = self.height();
-                    for (index, header) in batch.iter().enumerate() {
-                        self.headers
-                            .insert(anchor_height + 1 + index as u32, *header);
-                    }
+                    break;
                 }
             }
-            // // Remove items from the top of the chain until they link.
-            // while self.tip().ne(&batch
-            //     .first()
-            //     .expect("cannot extend from empty batch")
-            //     .prev_blockhash)
-            // {
-            //     if let Some((height, header)) = self.headers.pop_last() {
-            //         reorged.push(DisconnectedHeader::new(height, header));
-            //     }
-            // }
-            // let current_anchor = self.height();
-            // for (index, header) in batch.iter().enumerate() {
-            //     self.headers
-            //         .insert(current_anchor + 1 + index as u32, *header);
-            // }
+            // Actually remove anything that should no longer be connected
+            for removal in reorged.iter() {
+                self.remove(&removal.height);
+            }
+            // Add back the new headers, starting at the proper link
+            let current_anchor = self.height();
+            for (index, header) in batch.iter().enumerate() {
+                self.headers
+                    .insert(current_anchor + 1 + index as u32, *header);
+            }
         }
-        reorged.iter().rev().copied().collect()
+        reorged
     }
 
     fn remove(&mut self, height: &u32) {
diff --git a/src/lib.rs b/src/lib.rs
index b4e6ab1..e7c6f57 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -45,11 +45,11 @@ pub struct DisconnectedHeader {
     /// The height where this header used to be in the chain.
     pub height: u32,
     /// The reorganized header.
-    pub header: Header,
+    pub header: BlockHash,
 }
 
 impl DisconnectedHeader {
-    pub(crate) fn new(height: u32, header: Header) -> Self {
+    pub(crate) fn new(height: u32, header: BlockHash) -> Self {
         Self { height, header }
     }
 }