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    // Copyright 2015-2017 Parity Technologies (UK) Ltd.
    // This file is part of Parity.

    // Parity is free software: you can redistribute it and/or modify
    // it under the terms of the GNU General Public License as published by
    // the Free Software Foundation, either version 3 of the License, or
    // (at your option) any later version.

    // Parity is distributed in the hope that it will be useful,
    // but WITHOUT ANY WARRANTY; without even the implied warranty of
    // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    // GNU General Public License for more details.

    // You should have received a copy of the GNU General Public License
    // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

    use hash::H256;
    use sha3::Hashable;
    use hashdb::HashDB;
    use super::{TrieDB, Trie, TrieDBIterator, TrieItem, TrieIterator, Query};

    /// A `Trie` implementation which hashes keys and uses a generic `HashDB` backing database.
    /// Additionaly it stores inserted hash-key mappings for later retrieval.
    ///
    /// Use it as a `Trie` or `TrieMut` trait object.
    pub struct FatDB<'db> {
    	raw: TrieDB<'db>,
    }

    impl<'db> FatDB<'db> {
    	/// Create a new trie with the backing database `db` and empty `root`
    	/// Initialise to the state entailed by the genesis block.
    	/// This guarantees the trie is built correctly.
    	pub fn new(db: &'db HashDB, root: &'db H256) -> super::Result<Self> {
    		let fatdb = FatDB {
    			raw: TrieDB::new(db, root)?
    		};

    		Ok(fatdb)
    	}

    	/// Get the backing database.
    	pub fn db(&self) -> &HashDB {
    		self.raw.db()
    	}
    }

    impl<'db> Trie for FatDB<'db> {
    	fn iter<'a>(&'a self) -> super::Result<Box<TrieIterator<Item = TrieItem> + 'a>> {
    		FatDBIterator::new(&self.raw).map(|iter| Box::new(iter) as Box<_>)
    	}

    	fn root(&self) -> &H256 {
    		self.raw.root()
    	}

    	fn contains(&self, key: &[u8]) -> super::Result<bool> {
    		self.raw.contains(&key.sha3())
    	}

    	fn get_with<'a, 'key, Q: Query>(&'a self, key: &'key [u8], query: Q) -> super::Result<Option<Q::Item>>
    		where 'a: 'key
    	{
    		self.raw.get_with(&key.sha3(), query)
    	}
    }

    /// Itarator over inserted pairs of key values.
    pub struct FatDBIterator<'db> {
    	trie_iterator: TrieDBIterator<'db>,
    	trie: &'db TrieDB<'db>,
    }

    impl<'db> FatDBIterator<'db> {
    	/// Creates new iterator.
    	pub fn new(trie: &'db TrieDB) -> super::Result<Self> {
    		Ok(FatDBIterator {
    			trie_iterator: TrieDBIterator::new(trie)?,
    			trie: trie,
    		})
    	}
    }

    impl<'db> TrieIterator for FatDBIterator<'db> {
    	fn seek(&mut self, key: &[u8]) -> super::Result<()> {
    		self.trie_iterator.seek(&key.sha3())
    	}
    }

    impl<'db> Iterator for FatDBIterator<'db> {
    	type Item = TrieItem<'db>;

    	fn next(&mut self) -> Option<Self::Item> {
    		self.trie_iterator.next()
    			.map(|res|
    				res.map(|(hash, value)| {
    					let aux_hash = hash.sha3();
    					(self.trie.db().get(&aux_hash).expect("Missing fatdb hash").to_vec(), value)
    				})
    			)
    	}
    }

    #[test]
    fn fatdb_to_trie() {
    	use memorydb::MemoryDB;
    	use hashdb::DBValue;
    	use trie::{FatDBMut, TrieMut};

    	let mut memdb = MemoryDB::new();
    	let mut root = H256::default();
    	{
    		let mut t = FatDBMut::new(&mut memdb, &mut root);
    		t.insert(&[0x01u8, 0x23], &[0x01u8, 0x23]).unwrap();
    	}
    	let t = FatDB::new(&memdb, &root).unwrap();
    	assert_eq!(t.get(&[0x01u8, 0x23]).unwrap().unwrap(), DBValue::from_slice(&[0x01u8, 0x23]));
    	assert_eq!(t.iter().unwrap().map(Result::unwrap).collect::<Vec<_>>(), vec![(vec![0x01u8, 0x23], DBValue::from_slice(&[0x01u8, 0x23] as &[u8]))]);
    }

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