From fc4e2985d55d49835cfc13708d3a3d12203efbef Mon Sep 17 00:00:00 2001
From: Antioch Peverell <apeverell@protonmail.com>
Date: Thu, 26 Sep 2019 14:59:03 +0100
Subject: [PATCH] add block_hash to head_info so we can easily use them later
 (#3060)

---
 chain/src/store.rs         |  1 +
 core/src/consensus.rs      |  7 +++++++
 core/tests/consensus.rs    |  1 +
 servers/src/grin/server.rs | 19 ++-----------------
 4 files changed, 11 insertions(+), 17 deletions(-)

diff --git a/chain/src/store.rs b/chain/src/store.rs
index 673d39f6d..2d100dd62 100644
--- a/chain/src/store.rs
+++ b/chain/src/store.rs
@@ -562,6 +562,7 @@ impl<'a> Iterator for DifficultyIter<'a> {
 			let scaling = header.pow.secondary_scaling;
 
 			Some(HeaderInfo::new(
+				header.hash(),
 				header.timestamp.timestamp() as u64,
 				difficulty,
 				scaling,
diff --git a/core/src/consensus.rs b/core/src/consensus.rs
index f62ba2d8b..7067cbe59 100644
--- a/core/src/consensus.rs
+++ b/core/src/consensus.rs
@@ -21,6 +21,7 @@
 use std::cmp::{max, min};
 
 use crate::core::block::HeaderVersion;
+use crate::core::hash::{Hash, ZERO_HASH};
 use crate::global;
 use crate::pow::Difficulty;
 
@@ -219,6 +220,8 @@ pub const INITIAL_DIFFICULTY: u64 = 1_000_000 * UNIT_DIFFICULTY;
 /// take place
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct HeaderInfo {
+	/// Block hash, ZERO_HASH when this is a sythetic entry.
+	pub block_hash: Hash,
 	/// Timestamp of the header, 1 when not used (returned info)
 	pub timestamp: u64,
 	/// Network difficulty or next difficulty to use
@@ -232,12 +235,14 @@ pub struct HeaderInfo {
 impl HeaderInfo {
 	/// Default constructor
 	pub fn new(
+		block_hash: Hash,
 		timestamp: u64,
 		difficulty: Difficulty,
 		secondary_scaling: u32,
 		is_secondary: bool,
 	) -> HeaderInfo {
 		HeaderInfo {
+			block_hash,
 			timestamp,
 			difficulty,
 			secondary_scaling,
@@ -249,6 +254,7 @@ impl HeaderInfo {
 	/// PoW factor
 	pub fn from_ts_diff(timestamp: u64, difficulty: Difficulty) -> HeaderInfo {
 		HeaderInfo {
+			block_hash: ZERO_HASH,
 			timestamp,
 			difficulty,
 			secondary_scaling: global::initial_graph_weight(),
@@ -261,6 +267,7 @@ impl HeaderInfo {
 	/// timestamp
 	pub fn from_diff_scaling(difficulty: Difficulty, secondary_scaling: u32) -> HeaderInfo {
 		HeaderInfo {
+			block_hash: ZERO_HASH,
 			timestamp: 1,
 			difficulty,
 			secondary_scaling,
diff --git a/core/tests/consensus.rs b/core/tests/consensus.rs
index 7d933ceb0..0a819ac4a 100644
--- a/core/tests/consensus.rs
+++ b/core/tests/consensus.rs
@@ -86,6 +86,7 @@ fn repeat(interval: u64, diff: HeaderInfo, len: u64, cur_time: Option<u64>) -> V
 	pairs
 		.map(|(t, d)| {
 			HeaderInfo::new(
+				diff.block_hash,
 				cur_time + t as u64,
 				d.clone(),
 				diff.secondary_scaling,
diff --git a/servers/src/grin/server.rs b/servers/src/grin/server.rs
index 414a8f56c..8e1757358 100644
--- a/servers/src/grin/server.rs
+++ b/servers/src/grin/server.rs
@@ -40,7 +40,7 @@ use crate::common::stats::{
 	ChainStats, DiffBlock, DiffStats, PeerStats, ServerStateInfo, ServerStats, TxStats,
 };
 use crate::common::types::{Error, ServerConfig, StratumServerConfig};
-use crate::core::core::hash::{Hashed, ZERO_HASH};
+use crate::core::core::hash::Hashed;
 use crate::core::core::verifier_cache::{LruVerifierCache, VerifierCache};
 use crate::core::ser::ProtocolVersion;
 use crate::core::{consensus, genesis, global, pow};
@@ -436,9 +436,6 @@ impl Server {
 			let tip_height = self.head()?.height as i64;
 			let mut height = tip_height as i64 - last_blocks.len() as i64 + 1;
 
-			let header_pmmr = self.chain.header_pmmr();
-			let header_pmmr = header_pmmr.read();
-
 			let diff_entries: Vec<DiffBlock> = last_blocks
 				.windows(2)
 				.map(|pair| {
@@ -447,21 +444,9 @@ impl Server {
 
 					height += 1;
 
-					// Use header hash if real header.
-					// Default to "zero" hash if synthetic header_info.
-					let hash = if height >= 0 {
-						if let Ok(hash) = header_pmmr.get_header_hash_by_height(height as u64) {
-							hash
-						} else {
-							ZERO_HASH
-						}
-					} else {
-						ZERO_HASH
-					};
-
 					DiffBlock {
 						block_height: height,
-						block_hash: hash,
+						block_hash: next.block_hash,
 						difficulty: next.difficulty.to_num(),
 						time: next.timestamp,
 						duration: next.timestamp - prev.timestamp,