Adding is_descendent_of defenitions and fork tree testing with blockq…

…ueues (#1198)

* Adding fork-tree to worker

* Cargo fmt and clippy

* taplo fmt

* adding in default impl for clippy and removing senseless comments

* minor fmt

* Cherry picking and merging

* Cherry picking test of is_descendent_builder

* Removing comments and cleanup

* Adding in build_queue_header helper

* Adding in imports for SidechainBlockBuilderTrait

* Cargo fmt taplo fmt and clippy

* Adding some documentation to new structures

* cargo fmt

* Addressing comments

* Refactoring for pr

* Fix incorrect comment

* fixing docstring

* cargo fmt

* Moving errors to correct file

* refactor from comments half

* Refactoring for Chris comments

* Missing import

* cargo fmt

* Minor fixes for `is_descendant_builder` (#1206)

* properly feature gate the `is_descendant_of_builder`

* [header_db] improve traitbounds

* Update sidechain/consensus/common/src/is_descendant_of_builder.rs

Co-authored-by: clangenb <37865735+clangenb@users.noreply.github.com>

* Update sidechain/consensus/common/src/is_descendant_of_builder.rs

Co-authored-by: clangenb <37865735+clangenb@users.noreply.github.com>

* Update sidechain/consensus/common/src/is_descendant_of_builder.rs

Co-authored-by: clangenb <37865735+clangenb@users.noreply.github.com>

* Update sidechain/consensus/common/src/is_descendant_of_builder.rs

Co-authored-by: clangenb <37865735+clangenb@users.noreply.github.com>

---------

Co-authored-by: clangenb <37865735+clangenb@users.noreply.github.com>

sidechain/consensus/common/src/header_db.rs

@@ -0,0 +1,44 @@
+/*
+	Copyright 2021 Integritee AG and Supercomputing Systems AG
+
+	Licensed under the Apache License, Version 2.0 (the "License");
+	you may not use this file except in compliance with the License.
+	You may obtain a copy of the License at
+
+		http://www.apache.org/licenses/LICENSE-2.0
+
+	Unless required by applicable law or agreed to in writing, software
+	distributed under the License is distributed on an "AS IS" BASIS,
+	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+	See the License for the specific language governing permissions and
+	limitations under the License.
+
+*/
+use itp_types::H256;
+use its_primitives::traits::Header as HeaderT;
+use std::{collections::HashMap, convert::From, hash::Hash as HashT};
+
+/// Normally implemented on the `client` in substrate.
+/// Is a trait which can offer methods for interfacing with a block Database.
+pub trait HeaderDbTrait {
+	type Header: HeaderT;
+	/// Retrieves Header for the corresponding block hash.
+	fn header(&self, hash: &H256) -> Option<Self::Header>;
+}
+
+/// A mocked Header Database which allows you to take a Block Hash and Query a Block Header.
+pub struct HeaderDb<Hash, Header>(pub HashMap<Hash, Header>);
+
+impl<Hash, Header> HeaderDbTrait for HeaderDb<Hash, Header>
+where
+	// TODO: the H256 trait bounds are needed because: #1203
+	Hash: PartialEq + HashT + Into<H256> + From<H256> + core::cmp::Eq + Clone,
+	Header: HeaderT + Clone,
+{
+	type Header = Header;
+
+	fn header(&self, hash: &H256) -> Option<Self::Header> {
+		let header = self.0.get(&Hash::from(*hash))?;
+		Some(header.clone())
+	}
+}

sidechain/consensus/common/src/is_descendant_of_builder.rs

@@ -0,0 +1,133 @@
+/*
+	Copyright 2021 Integritee AG and Supercomputing Systems AG
+
+	Licensed under the Apache License, Version 2.0 (the "License");
+	you may not use this file except in compliance with the License.
+	You may obtain a copy of the License at
+
+		http://www.apache.org/licenses/LICENSE-2.0
+
+	Unless required by applicable law or agreed to in writing, software
+	distributed under the License is distributed on an "AS IS" BASIS,
+	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+	See the License for the specific language governing permissions and
+	limitations under the License.
+
+*/
+use crate::header_db::HeaderDbTrait;
+use core::{hash::Hash as HashT, marker::PhantomData};
+use itp_types::H256;
+use its_primitives::traits::Header as HeaderT;
+
+pub struct IsDescendantOfBuilder<Hash, HeaderDb, Error>(PhantomData<(Hash, HeaderDb, Error)>);
+
+impl<'a, Hash, HeaderDb, Error> IsDescendantOfBuilder<Hash, HeaderDb, Error>
+where
+	Error: From<()>,
+	Hash: PartialEq + HashT + Default + Into<H256> + From<H256> + Clone,
+	HeaderDb: HeaderDbTrait,
+{
+	/// Builds the `is_descendant_of` closure for the fork-tree
+	/// used when adding and removing nodes from the tree.
+	pub fn build_is_descendant_of(
+		current: Option<(&'a Hash, &'a Hash)>,
+		header_db: &'a HeaderDb,
+	) -> impl Fn(&Hash, &Hash) -> Result<bool, Error> + 'a {
+		move |base, head| {
+			// If the base is equal to the proposed head, then the head is for sure not a descendant of the base.
+			if base == head {
+				return Ok(false)
+			}
+
+			let mut head = head;
+			if let Some((current_hash, current_parent_hash)) = current {
+				// If the current hash is equal to the base, then it will not be a descendant of base.
+				if current_hash == base {
+					return Ok(false)
+				}
+
+				// If the current hash is the head and the parent is the base, then we know that
+				// this current hash is the descendant of the parent. Otherwise we can set the
+				// head to the parent and find the lowest common ancestor between `head`
+				/// and `base` in the tree.
+				if current_hash == head {
+					if current_parent_hash == base {
+						return Ok(true)
+					} else {
+						head = current_parent_hash;
+					}
+				}
+			}
+
+			let ancestor =
+				<LowestCommonAncestorFinder<Hash, HeaderDb>>::find_lowest_common_ancestor(
+					head, base, header_db,
+				)?;
+			Ok(ancestor == *base)
+		}
+	}
+}
+
+pub struct LowestCommonAncestorFinder<Hash, HeaderDb>(PhantomData<(Hash, HeaderDb)>);
+
+impl<Hash, HeaderDb> LowestCommonAncestorFinder<Hash, HeaderDb>
+where
+	Hash: PartialEq + Default + Into<H256> + From<H256> + Clone,
+	HeaderDb: HeaderDbTrait,
+{
+	/// Used by the `build_is_descendant_of` to find the LCA of two nodes in the fork-tree.
+	fn find_lowest_common_ancestor(a: &Hash, b: &Hash, header_db: &HeaderDb) -> Result<Hash, ()> {
+		let header_1 = header_db.header(&a.clone().into()).ok_or(())?;
+		let header_2 = header_db.header(&b.clone().into()).ok_or(())?;
+		let mut blocknum_1 = header_1.block_number();
+		let mut blocknum_2 = header_2.block_number();
+		let mut parent_1 = Hash::from(header_1.parent_hash());
+		let mut parent_2 = Hash::from(header_2.parent_hash());
+
+		if *a == parent_2 {
+			// Then a is the common ancestor of b and it means it is itself the ancestor
+			return Ok(parent_2)
+		}
+
+		if *b == parent_1 {
+			// Then b is the common ancestor of a and it means it is itself the ancestor
+			return Ok(parent_1)
+		}
+
+		while blocknum_1 > blocknum_2 {
+			// This means block 1 is further down in the tree than block 2
+			let new_parent = header_db.header(&parent_1.clone().into()).ok_or(())?;
+
+			if new_parent.block_number() >= blocknum_2 {
+				blocknum_1 = new_parent.block_number();
+				parent_1 = Hash::from(new_parent.parent_hash());
+			} else {
+				break
+			}
+		}
+
+		while blocknum_2 > blocknum_1 {
+			// This means block 2 is further down in the tree than block 1
+			let new_parent = header_db.header(&parent_2.clone().into()).ok_or(())?;
+
+			if new_parent.block_number() >= blocknum_1 {
+				blocknum_2 = new_parent.block_number();
+				parent_2 = Hash::from(new_parent.parent_hash());
+			} else {
+				break
+			}
+		}
+
+		// At this point will be at equal height
+		while parent_1 != parent_2 {
+			// go up on both nodes
+			let new_header_1 = header_db.header(&parent_1.into()).ok_or(())?;
+			let new_header_2 = header_db.header(&parent_2.into()).ok_or(())?;
+			parent_1 = Hash::from(new_header_1.parent_hash());
+			parent_2 = Hash::from(new_header_2.parent_hash());
+		}
+
+		// Return any Parent node Hash as in worst case scenario it is the root which is shared amongst all
+		Ok(parent_1)
+	}
+}

sidechain/consensus/common/src/lib.rs

@@ -36,9 +36,13 @@ mod block_import;
 mod block_import_confirmation_handler;
 mod block_import_queue_worker;
 mod error;
-mod is_descendent_of_builder;
+mod header_db;
 mod peer_block_sync;
 
+// The feature flag will be removed once we use the module outside of tests.
+#[cfg(test)]
+mod is_descendant_of_builder;
+
 #[cfg(test)]
 mod test;