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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/>.

    //! Trie interface and implementation.

    use std::fmt;
    use hash::H256;
    use hashdb::{HashDB, DBValue};

    /// Export the standardmap module.
    pub mod standardmap;
    /// Export the node module.
    pub mod node;
    /// Export the triedb module.
    pub mod triedb;
    /// Export the triedbmut module.
    pub mod triedbmut;
    /// Export the sectriedb module.
    pub mod sectriedb;
    /// Export the sectriedbmut module.
    pub mod sectriedbmut;
    /// Trie query recording.
    pub mod recorder;

    mod fatdb;
    mod fatdbmut;
    mod lookup;

    pub use self::standardmap::{Alphabet, StandardMap, ValueMode};
    pub use self::triedbmut::TrieDBMut;
    pub use self::triedb::{TrieDB, TrieDBIterator};
    pub use self::sectriedbmut::SecTrieDBMut;
    pub use self::sectriedb::SecTrieDB;
    pub use self::fatdb::{FatDB, FatDBIterator};
    pub use self::fatdbmut::FatDBMut;
    pub use self::recorder::Recorder;

    /// Trie Errors.
    ///
    /// These borrow the data within them to avoid excessive copying on every
    /// trie operation.
    #[derive(Debug, PartialEq, Eq, Clone)]
    pub enum TrieError {
    	/// Attempted to create a trie with a state root not in the DB.
    	InvalidStateRoot(H256),
    	/// Trie item not found in the database,
    	IncompleteDatabase(H256),
    }

    impl fmt::Display for TrieError {
    	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    		match *self {
    			TrieError::InvalidStateRoot(ref root) => write!(f, "Invalid state root: {}", root),
    			TrieError::IncompleteDatabase(ref missing) =>
    				write!(f, "Database missing expected key: {}", missing),
    		}
    	}
    }

    /// Trie result type. Boxed to avoid copying around extra space for `H256`s on successful queries.
    pub type Result<T> = ::std::result::Result<T, Box<TrieError>>;

    /// Trie-Item type.
    pub type TrieItem<'a> = Result<(Vec<u8>, DBValue)>;

    /// Description of what kind of query will be made to the trie.
    ///
    /// This is implemented for any &mut recorder (where the query will return
    /// a DBValue), any function taking raw bytes (where no recording will be made),
    /// or any tuple of (&mut Recorder, FnOnce(&[u8]))
    pub trait Query {
    	/// Output item.
    	type Item;

    	/// Decode a byte-slice into the desired item.
    	fn decode(self, &[u8]) -> Self::Item;

    	/// Record that a node has been passed through.
    	fn record(&mut self, &H256, &[u8], u32) { }
    }

    impl<'a> Query for &'a mut Recorder {
    	type Item = DBValue;

    	fn decode(self, value: &[u8]) -> DBValue { DBValue::from_slice(value) }
    	fn record(&mut self, hash: &H256, data: &[u8], depth: u32) {
    		(&mut **self).record(hash, data, depth);
    	}
    }

    impl<F, T> Query for F where F: for<'a> FnOnce(&'a [u8]) -> T {
    	type Item = T;

    	fn decode(self, value: &[u8]) -> T { (self)(value) }
    }

    impl<'a, F, T> Query for (&'a mut Recorder, F) where F: FnOnce(&[u8]) -> T {
    	type Item = T;

    	fn decode(self, value: &[u8]) -> T { (self.1)(value) }
    	fn record(&mut self, hash: &H256, data: &[u8], depth: u32) {
    		self.0.record(hash, data, depth)
    	}
    }

    /// A key-value datastore implemented as a database-backed modified Merkle tree.
    pub trait Trie {
    	/// Return the root of the trie.
    	fn root(&self) -> &H256;

    	/// Is the trie empty?
    	fn is_empty(&self) -> bool { *self.root() == ::sha3::SHA3_NULL_RLP }

    	/// Does the trie contain a given key?
    	fn contains(&self, key: &[u8]) -> Result<bool> {
    		self.get(key).map(|x| x.is_some())
    	}

    	/// What is the value of the given key in this trie?
    	fn get<'a, 'key>(&'a self, key: &'key [u8]) -> Result<Option<DBValue>> where 'a: 'key {
    		self.get_with(key, DBValue::from_slice)
    	}

    	/// Search for the key with the given query parameter. See the docs of the `Query`
    	/// trait for more details.
    	fn get_with<'a, 'key, Q: Query>(&'a self, key: &'key [u8], query: Q)
    		-> Result<Option<Q::Item>> where 'a: 'key;

    	/// Returns a depth-first iterator over the elements of trie.
    	fn iter<'a>(&'a self) -> Result<Box<TrieIterator<Item = TrieItem> + 'a>>;
    }

    /// A key-value datastore implemented as a database-backed modified Merkle tree.
    pub trait TrieMut {
    	/// Return the root of the trie.
    	fn root(&mut self) -> &H256;

    	/// Is the trie empty?
    	fn is_empty(&self) -> bool;

    	/// Does the trie contain a given key?
    	fn contains(&self, key: &[u8]) -> Result<bool> {
    		self.get(key).map(|x| x.is_some())
    	}

    	/// What is the value of the given key in this trie?
    	fn get<'a, 'key>(&'a self, key: &'key [u8]) -> Result<Option<DBValue>> where 'a: 'key;

    	/// Insert a `key`/`value` pair into the trie. An empty value is equivalent to removing
    	/// `key` from the trie. Returns the old value associated with this key, if it existed.
    	fn insert(&mut self, key: &[u8], value: &[u8]) -> Result<Option<DBValue>>;

    	/// Remove a `key` from the trie. Equivalent to making it equal to the empty
    	/// value. Returns the old value associated with this key, if it existed.
    	fn remove(&mut self, key: &[u8]) -> Result<Option<DBValue>>;
    }

    /// A trie iterator that also supports random access.
    pub trait TrieIterator : Iterator {
    	/// Position the iterator on the first element with key > `key`
    	fn seek(&mut self, key: &[u8]) -> Result<()>;
    }

    /// Trie types
    #[derive(Debug, PartialEq, Clone)]
    pub enum TrieSpec {
    	/// Generic trie.
    	Generic,
    	/// Secure trie.
    	Secure,
    	///	Secure trie with fat database.
    	Fat,
    }

    impl Default for TrieSpec {
    	fn default() -> TrieSpec {
    		TrieSpec::Secure
    	}
    }

    /// Trie factory.
    #[derive(Default, Clone)]
    pub struct TrieFactory {
    	spec: TrieSpec,
    }

    /// All different kinds of tries.
    /// This is used to prevent a heap allocation for every created trie.
    pub enum TrieKinds<'db> {
    	/// A generic trie db.
    	Generic(TrieDB<'db>),
    	/// A secure trie db.
    	Secure(SecTrieDB<'db>),
    	/// A fat trie db.
    	Fat(FatDB<'db>),
    }

    // wrapper macro for making the match easier to deal with.
    macro_rules! wrapper {
    	($me: ident, $f_name: ident, $($param: ident),*) => {
    		match *$me {
    			TrieKinds::Generic(ref t) => t.$f_name($($param),*),
    			TrieKinds::Secure(ref t) => t.$f_name($($param),*),
    			TrieKinds::Fat(ref t) => t.$f_name($($param),*),
    		}
    	}
    }

    impl<'db> Trie for TrieKinds<'db> {
    	fn root(&self) -> &H256 {
    		wrapper!(self, root,)
    	}

    	fn is_empty(&self) -> bool {
    		wrapper!(self, is_empty,)
    	}

    	fn contains(&self, key: &[u8]) -> Result<bool> {
    		wrapper!(self, contains, key)
    	}

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

    	fn iter<'a>(&'a self) -> Result<Box<TrieIterator<Item = TrieItem> + 'a>> {
    		wrapper!(self, iter,)
    	}
    }

    #[cfg_attr(feature="dev", allow(wrong_self_convention))]
    impl TrieFactory {
    	/// Creates new factory.
    	pub fn new(spec: TrieSpec) -> Self {
    		TrieFactory {
    			spec: spec,
    		}
    	}

    	/// Create new immutable instance of Trie.
    	pub fn readonly<'db>(&self, db: &'db HashDB, root: &'db H256) -> Result<TrieKinds<'db>> {
    		match self.spec {
    			TrieSpec::Generic => Ok(TrieKinds::Generic(TrieDB::new(db, root)?)),
    			TrieSpec::Secure => Ok(TrieKinds::Secure(SecTrieDB::new(db, root)?)),
    			TrieSpec::Fat => Ok(TrieKinds::Fat(FatDB::new(db, root)?)),
    		}
    	}

    	/// Create new mutable instance of Trie.
    	pub fn create<'db>(&self, db: &'db mut HashDB, root: &'db mut H256) -> Box<TrieMut + 'db> {
    		match self.spec {
    			TrieSpec::Generic => Box::new(TrieDBMut::new(db, root)),
    			TrieSpec::Secure => Box::new(SecTrieDBMut::new(db, root)),
    			TrieSpec::Fat => Box::new(FatDBMut::new(db, root)),
    		}
    	}

    	/// Create new mutable instance of trie and check for errors.
    	pub fn from_existing<'db>(&self, db: &'db mut HashDB, root: &'db mut H256) -> Result<Box<TrieMut + 'db>> {
    		match self.spec {
    			TrieSpec::Generic => Ok(Box::new(TrieDBMut::from_existing(db, root)?)),
    			TrieSpec::Secure => Ok(Box::new(SecTrieDBMut::from_existing(db, root)?)),
    			TrieSpec::Fat => Ok(Box::new(FatDBMut::from_existing(db, root)?)),
    		}
    	}

    	/// Returns true iff the trie DB is a fat DB (allows enumeration of keys).
    	pub fn is_fat(&self) -> bool { self.spec == TrieSpec::Fat }
    }

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