From 94255721bbedc55a1b84dde90bdab5686c4b4d36 Mon Sep 17 00:00:00 2001
From: Elias Rohrer <ero@tnull.de>
Date: Tue, 6 Dec 2022 13:54:23 +0100
Subject: [PATCH] Add `best_tip_hash` field to `BlockStatus`

We add the tip of the best chain known to the block status endpoint.

This useful in order to allow a client issuing a sequence of queries to
check whether a reorg happened in-between, i.e., to detect any possible
inconsistencies.
---
 src/new_index/schema.rs | 12 +++++++-----
 src/rest.rs             |  3 ++-
 src/util/block.rs       | 11 +++++++++--
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/new_index/schema.rs b/src/new_index/schema.rs
index 35e49f8de..f0fac286b 100644
--- a/src/new_index/schema.rs
+++ b/src/new_index/schema.rs
@@ -889,7 +889,7 @@ impl ChainQuery {
             .map(BlockId::from)
     }
 
-    pub fn get_block_status(&self, hash: &BlockHash) -> BlockStatus {
+    pub fn get_block_status(&self, hash: &BlockHash, best_tip_hash: &BlockHash) -> BlockStatus {
         // TODO differentiate orphaned and non-existing blocks? telling them apart requires
         // an additional db read.
 
@@ -897,16 +897,18 @@ impl ChainQuery {
 
         // header_by_blockhash only returns blocks that are part of the best chain,
         // or None for orphaned blocks.
-        headers
-            .header_by_blockhash(hash)
-            .map_or_else(BlockStatus::orphaned, |header| {
+        headers.header_by_blockhash(hash).map_or_else(
+            || BlockStatus::orphaned(*best_tip_hash),
+            |header| {
                 BlockStatus::confirmed(
                     header.height(),
                     headers
                         .header_by_height(header.height() + 1)
                         .map(|h| *h.hash()),
+                    *best_tip_hash,
                 )
-            })
+            },
+        )
     }
 
     #[cfg(not(feature = "liquid"))]
diff --git a/src/rest.rs b/src/rest.rs
index 108215634..4d28b903a 100644
--- a/src/rest.rs
+++ b/src/rest.rs
@@ -673,7 +673,8 @@ fn handle_request(
         }
         (&Method::GET, Some(&"block"), Some(hash), Some(&"status"), None, None) => {
             let hash = BlockHash::from_hex(hash)?;
-            let status = query.chain().get_block_status(&hash);
+            let best_tip_hash = query.chain().best_hash();
+            let status = query.chain().get_block_status(&hash, &best_tip_hash);
             let ttl = ttl_by_depth(status.height, query);
             json_response(status, ttl)
         }
diff --git a/src/util/block.rs b/src/util/block.rs
index 1f6b98508..93965221c 100644
--- a/src/util/block.rs
+++ b/src/util/block.rs
@@ -256,22 +256,29 @@ pub struct BlockStatus {
     pub in_best_chain: bool,
     pub height: Option<usize>,
     pub next_best: Option<BlockHash>,
+    pub best_tip_hash: BlockHash,
 }
 
 impl BlockStatus {
-    pub fn confirmed(height: usize, next_best: Option<BlockHash>) -> BlockStatus {
+    pub fn confirmed(
+        height: usize,
+        next_best: Option<BlockHash>,
+        best_tip_hash: BlockHash,
+    ) -> BlockStatus {
         BlockStatus {
             in_best_chain: true,
             height: Some(height),
             next_best,
+            best_tip_hash,
         }
     }
 
-    pub fn orphaned() -> BlockStatus {
+    pub fn orphaned(best_tip_hash: BlockHash) -> BlockStatus {
         BlockStatus {
             in_best_chain: false,
             height: None,
             next_best: None,
+            best_tip_hash,
         }
     }
 }