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    use std::cmp::min;
    use bit_vec::BitVec;
    use chain::merkle_node_hash;
    use primitives::hash::H256;

    /// Partial merkle tree
    pub struct PartialMerkleTree {
    	/// Total number of transactions
    	pub tx_count: usize,
    	/// Nodes hashes
    	pub hashes: Vec<H256>,
    	/// Match flags
    	pub flags: BitVec,
    }

    /// Partial merkle tree parse result
    #[cfg(test)]
    pub struct ParsedPartialMerkleTree {
    	/// Merkle root
    	pub root: H256,
    	/// Matched hashes
    	pub hashes: Vec<H256>,
    	/// Match flags
    	pub flags: BitVec,
    }

    /// Build partial merkle tree
    pub fn build_partial_merkle_tree(tx_hashes: Vec<H256>, tx_matches: BitVec) -> PartialMerkleTree {
    	PartialMerkleTreeBuilder::build(tx_hashes, tx_matches)
    }

    /// Parse partial merkle tree
    #[cfg(test)]
    pub fn parse_partial_merkle_tree(tree: PartialMerkleTree) -> Result<ParsedPartialMerkleTree, String> {
    	PartialMerkleTreeBuilder::parse(tree)
    }

    /// Service structure to construct `merkleblock` message.
    struct PartialMerkleTreeBuilder {
    	/// All transactions length.
    	all_len: usize,
    	/// All transactions hashes.
    	all_hashes: Vec<H256>,
    	/// Match flags for all transactions.
    	all_matches: BitVec,
    	/// Partial hashes.
    	hashes: Vec<H256>,
    	/// Partial match flags.
    	matches: BitVec,
    }

    impl PartialMerkleTree {
    	/// Create new merkle tree with given data
    	pub fn new(tx_count:usize, hashes: Vec<H256>, flags: BitVec) -> Self {
    		PartialMerkleTree {
    			tx_count: tx_count,
    			hashes: hashes,
    			flags: flags,
    		}
    	}
    }

    #[cfg(test)]
    impl ParsedPartialMerkleTree {
    	pub fn new(root: H256, hashes: Vec<H256>, flags: BitVec) -> Self {
    		ParsedPartialMerkleTree {
    			root: root,
    			hashes: hashes,
    			flags: flags,
    		}
    	}
    }

    impl PartialMerkleTreeBuilder {
    	/// Build partial merkle tree as described here:
    	/// https://bitcoin.org/en/developer-reference#creating-a-merkleblock-message
    	pub fn build(all_hashes: Vec<H256>, all_matches: BitVec) -> PartialMerkleTree {
    		let mut partial_merkle_tree = PartialMerkleTreeBuilder {
    			all_len: all_hashes.len(),
    			all_hashes: all_hashes,
    			all_matches: all_matches,
    			hashes: Vec::new(),
    			matches: BitVec::new(),
    		};
    		partial_merkle_tree.build_tree();
    		PartialMerkleTree::new(partial_merkle_tree.all_len, partial_merkle_tree.hashes, partial_merkle_tree.matches)
    	}

    	#[cfg(test)]
    	/// Parse partial merkle tree as described here:
    	/// https://bitcoin.org/en/developer-reference#parsing-a-merkleblock-message
    	pub fn parse(tree: PartialMerkleTree) -> Result<ParsedPartialMerkleTree, String> {
    		let mut partial_merkle_tree = PartialMerkleTreeBuilder {
    			all_len: tree.tx_count,
    			all_hashes: Vec::new(),
    			all_matches: BitVec::from_elem(tree.tx_count, false),
    			hashes: tree.hashes,
    			matches: tree.flags,
    		};

    		let merkle_root = try!(partial_merkle_tree.parse_tree());
    		Ok(ParsedPartialMerkleTree::new(merkle_root, partial_merkle_tree.all_hashes, partial_merkle_tree.all_matches))
    	}

    	fn build_tree(&mut self) {
    		let tree_height = self.tree_height();
    		self.build_branch(tree_height, 0)
    	}

    	#[cfg(test)]
    	fn parse_tree(&mut self) -> Result<H256, String> {
    		if self.all_len == 0 {
    			return Err("no transactions".into());
    		}
    		if self.hashes.len() > self.all_len {
    			return Err("too many hashes".into());
    		}
    		if self.matches.len() < self.hashes.len() {
    			return Err("too few matches".into());
    		}

    		// parse tree
    		let mut matches_used = 0usize;
    		let mut hashes_used = 0usize;
    		let tree_height = self.tree_height();
    		let merkle_root = try!(self.parse_branch(tree_height, 0, &mut matches_used, &mut hashes_used));

    		if matches_used != self.matches.len() {
    			return Err("not all matches used".into());
    		}
    		if hashes_used != self.hashes.len() {
    			return Err("not all hashes used".into());
    		}

    		Ok(merkle_root)
    	}

    	fn build_branch(&mut self, height: usize, pos: usize) {
    		// determine whether this node is the parent of at least one matched txid
    		let transactions_begin = pos << height;
    		let transactions_end = min(self.all_len, (pos + 1) << height);
    		let flag = (transactions_begin..transactions_end).any(|idx| self.all_matches[idx]);
    		// remember flag
    		self.matches.push(flag);
    		// proceeed with descendants
    		if height == 0 || !flag {
    			// we're at the leaf level || there is no match
    			let hash = self.branch_hash(height, pos);
    			self.hashes.push(hash);
    		} else {
    			// proceed with left child
    			self.build_branch(height - 1, pos << 1);
    			// proceed with right child if any
    			if (pos << 1) + 1 < self.level_width(height - 1) {
    				self.build_branch(height - 1, (pos << 1) + 1);
    			}
    		}
    	}

    	#[cfg(test)]
    	fn parse_branch(&mut self, height: usize, pos: usize, matches_used: &mut usize, hashes_used: &mut usize) -> Result<H256, String> {
    		if *matches_used >= self.matches.len() {
    			return Err("all matches used".into());
    		}

    		let flag = self.matches[*matches_used];
    		*matches_used += 1;

    		if height == 0 || !flag {
    			// we're at the leaf level || there is no match
    			if *hashes_used > self.hashes.len() {
    				return Err("all hashes used".into());
    			}

    			// get node hash
    			let ref hash = self.hashes[*hashes_used];
    			*hashes_used += 1;

    			// on leaf level && matched flag set => mark transaction as matched
    			if height == 0 && flag {
    				self.all_hashes.push(hash.clone());
    				self.all_matches.set(pos, true);
    			}

    			Ok(hash.clone())
    		} else {
    			// proceed with left child
    			let left = try!(self.parse_branch(height - 1, pos << 1, matches_used, hashes_used));
    			// proceed with right child if any
    			let has_right_child = (pos << 1) + 1 < self.level_width(height - 1);
    			let right = if has_right_child {
    				try!(self.parse_branch(height - 1, (pos << 1) + 1, matches_used, hashes_used))
    			} else {
    				left.clone()
    			};

    			if has_right_child && left == right {
    				Err("met same hash twice".into())
    			} else {
    				Ok(merkle_node_hash(&left, &right))
    			}
    		}
    	}

    	fn tree_height(&self) -> usize {
    		let mut height = 0usize;
    		while self.level_width(height) > 1 {
    			height += 1;
    		}
    		height
    	}

    	fn level_width(&self, height: usize) -> usize {
    		(self.all_len + (1 << height) - 1) >> height
    	}

    	fn branch_hash(&self, height: usize, pos: usize) -> H256 {
    		if height == 0 {
    			self.all_hashes[pos].clone()
    		} else {
    			let left = self.branch_hash(height - 1, pos << 1);
    			let right = if (pos << 1) + 1 < self.level_width(height - 1) {
    				self.branch_hash(height - 1, (pos << 1) + 1)
    			} else {
    				left.clone()
    			};

    			merkle_node_hash(&left, &right)
    		}
    	}
    }

    #[cfg(test)]
    mod tests {
    	extern crate test_data;

    	use chain::{Transaction, merkle_root};
    	use primitives::hash::H256;
    	use super::{build_partial_merkle_tree, parse_partial_merkle_tree};

    	#[test]
    	// test from core implementation (slow)
    	// https://github.com/bitcoin/bitcoin/blob/master/src/test/pmt_tests.cpp
    	fn test_build_merkle_block() {
    		use bit_vec::BitVec;
    		use rand::{Rng, SeedableRng, StdRng};

    		let rng_seed: &[_] = &[0, 0, 0, 0];
    		let mut rng: StdRng = SeedableRng::from_seed(rng_seed);

    		// for some transactions counts
    		let tx_counts: Vec<usize> = vec![1, 4, 7, 17, 56, 100, 127, 256, 312, 513, 1000, 4095];
    		for tx_count in tx_counts {
    			// build block with given transactions number
    			let transactions: Vec<Transaction> = (0..tx_count).map(|n| test_data::TransactionBuilder::with_version(n as i32).into()).collect();
    			let hashes: Vec<_> = transactions.iter().map(|t| t.hash()).collect();
    			let merkle_root = merkle_root(&hashes);

    			// mark different transactions as matched
    			for seed_tweak in 1..15 {
    				let mut matches: BitVec = BitVec::with_capacity(tx_count);
    				let mut matched_hashes: Vec<H256> = Vec::with_capacity(tx_count);
    				for i in 0usize..tx_count {
    					let is_match = (rng.gen::<u32>() & ((1 << (seed_tweak / 2)) - 1)) == 0;
    					matches.push(is_match);
    					if is_match {
    						matched_hashes.push(hashes[i].clone());
    					}
    				}

    				// build partial merkle tree
    				let partial_tree = build_partial_merkle_tree(hashes.clone(), matches.clone());
    				// parse tree back
    				let parsed_tree = parse_partial_merkle_tree(partial_tree).expect("no error");

    				assert_eq!(matched_hashes, parsed_tree.hashes);
    				assert_eq!(matches, parsed_tree.flags);
    				assert_eq!(merkle_root, parsed_tree.root);
    			}
    		}
    	}
    }

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