[T4] Secondary proof of work difficulty adjustments (#1709)

* First pass at secondary proof of work difficulty adjustments
* Core and chain test fixes
* Next difficulty calc now needs a height. Scaling calculation fixes. Setting scaling on mined block.
* Change factor to u32 instead of u64.
* Cleanup structs used by next_difficulty
* Fix header size calc with u32 scaling

servers/src/common/types.rs

@@ -166,11 +166,10 @@ impl ServerConfig {
 		// check [server.p2p_config.capabilities] with 'archive_mode' in [server]
 		if let Some(archive) = self.archive_mode {
 			// note: slog not available before config loaded, only print here.
-			if archive
-				!= self
-					.p2p_config
-					.capabilities
-					.contains(p2p::Capabilities::FULL_HIST)
+			if archive != self
+				.p2p_config
+				.capabilities
+				.contains(p2p::Capabilities::FULL_HIST)
 			{
 				// if conflict, 'archive_mode' win
 				self.p2p_config

servers/src/grin/server.rs

@@ -30,7 +30,6 @@ use common::stats::{DiffBlock, DiffStats, PeerStats, ServerStateInfo, ServerStat
 use common::types::{Error, ServerConfig, StratumServerConfig, SyncState};
 use core::core::hash::Hashed;
 use core::core::verifier_cache::{LruVerifierCache, VerifierCache};
-use core::pow::Difficulty;
 use core::{consensus, genesis, global, pow};
 use grin::{dandelion_monitor, seed, sync};
 use mining::stratumserver;
@@ -397,14 +396,14 @@ impl Server {
 		// code clean. This may be handy for testing but not really needed
 		// for release
 		let diff_stats = {
-			let last_blocks: Vec<Result<(u64, Difficulty), consensus::TargetError>> =
+			let last_blocks: Vec<consensus::HeaderInfo> =
 				global::difficulty_data_to_vector(self.chain.difficulty_iter())
 					.into_iter()
 					.skip(consensus::MEDIAN_TIME_WINDOW as usize)
 					.take(consensus::DIFFICULTY_ADJUST_WINDOW as usize)
 					.collect();
 
-			let mut last_time = last_blocks[0].clone().unwrap().0;
+			let mut last_time = last_blocks[0].timestamp;
 			let tip_height = self.chain.head().unwrap().height as i64;
 			let earliest_block_height = tip_height as i64 - last_blocks.len() as i64;
 
@@ -414,15 +413,14 @@ impl Server {
 				.iter()
 				.skip(1)
 				.map(|n| {
-					let (time, diff) = n.clone().unwrap();
-					let dur = time - last_time;
+					let dur = n.timestamp - last_time;
 					let height = earliest_block_height + i + 1;
 					i += 1;
-					last_time = time;
+					last_time = n.timestamp;
 					DiffBlock {
 						block_number: height,
-						difficulty: diff.to_num(),
-						time: time,
+						difficulty: n.difficulty.to_num(),
+						time: n.timestamp,
 						duration: dur,
 					}
 				}).collect();

servers/src/grin/sync/syncer.rs

@@ -185,7 +185,7 @@ fn needs_syncing(
 			// sum the last 5 difficulties to give us the threshold
 			let threshold = chain
 				.difficulty_iter()
-				.filter_map(|x| x.map(|(_, x)| x).ok())
+				.map(|x| x.difficulty)
 				.take(5)
 				.fold(Difficulty::zero(), |sum, val| sum + val);
 

servers/src/mining/mine_block.rs

@@ -106,7 +106,7 @@ fn build_block(
 
 	// Determine the difficulty our block should be at.
 	// Note: do not keep the difficulty_iter in scope (it has an active batch).
-	let difficulty = consensus::next_difficulty(chain.difficulty_iter()).unwrap();
+	let difficulty = consensus::next_difficulty(1, chain.difficulty_iter());
 
 	// extract current transaction from the pool
 	// TODO - we have a lot of unwrap() going on in this fn...
@@ -126,13 +126,14 @@ fn build_block(
 	};
 
 	let (output, kernel, block_fees) = get_coinbase(wallet_listener_url, block_fees)?;
-	let mut b = core::Block::with_reward(&head, txs, output, kernel, difficulty.clone())?;
+	let mut b = core::Block::with_reward(&head, txs, output, kernel, difficulty.difficulty)?;
 
 	// making sure we're not spending time mining a useless block
 	b.validate(&head.total_kernel_offset, verifier_cache)?;
 
 	b.header.pow.nonce = thread_rng().gen();
-	b.header.timestamp = DateTime::<Utc>::from_utc(NaiveDateTime::from_timestamp(now_sec, 0), Utc);;
+	b.header.pow.scaling_difficulty = difficulty.secondary_scaling;
+	b.header.timestamp = DateTime::<Utc>::from_utc(NaiveDateTime::from_timestamp(now_sec, 0), Utc);
 
 	let b_difficulty = (b.header.total_difficulty() - head.total_difficulty()).to_num();
 	debug!(