//! Blockchain DB extras.

use util::*;
use header::BlockNumber;
use rocksdb::{DB, Writable};

/// Represents index of extra data in database
#[derive(Copy, Debug, Hash, Eq, PartialEq, Clone)]
pub enum ExtrasIndex {
	/// TODO [debris] Please document me
	BlockDetails = 0,
	/// TODO [debris] Please document me
	BlockHash = 1,
	/// TODO [debris] Please document me
	TransactionAddress = 2,
	/// TODO [debris] Please document me
	BlockLogBlooms = 3,
	/// TODO [debris] Please document me
	BlocksBlooms = 4
} 

/// trait used to write Extras data to db
pub trait ExtrasWritable {
	/// TODO [debris] Please document me
	fn put_extras<K, T>(&self, hash: &K, value: &T) where
		T: ExtrasIndexable + Encodable, 
		K: ExtrasSliceConvertable;
}

/// trait used to read Extras data from db
pub trait ExtrasReadable {
	/// TODO [debris] Please document me
	fn get_extras<K, T>(&self, hash: &K) -> Option<T> where
		T: ExtrasIndexable + Decodable,
		K: ExtrasSliceConvertable;

	/// TODO [debris] Please document me
	fn extras_exists<K, T>(&self, hash: &K) -> bool where
		T: ExtrasIndexable,
		K: ExtrasSliceConvertable;
}

impl<W> ExtrasWritable for W where W: Writable {
	fn put_extras<K, T>(&self, hash: &K, value: &T) where
		T: ExtrasIndexable + Encodable, 
		K: ExtrasSliceConvertable {
		
		self.put(&hash.to_extras_slice(T::extras_index()), &encode(value)).unwrap()
	}
}

impl ExtrasReadable for DB {
	fn get_extras<K, T>(&self, hash: &K) -> Option<T> where
		T: ExtrasIndexable + Decodable,
		K: ExtrasSliceConvertable {

		self.get(&hash.to_extras_slice(T::extras_index())).unwrap()
			.map(|v| decode(&v))
	}

	fn extras_exists<K, T>(&self, hash: &K) -> bool where
		T: ExtrasIndexable,
		K: ExtrasSliceConvertable {

		self.get(&hash.to_extras_slice(T::extras_index())).unwrap().is_some()
	}
}

/// Implementations should convert arbitrary type to database key slice
pub trait ExtrasSliceConvertable {
	/// Convert self, with `i` (the index), to a 264-bit extras DB key.
	fn to_extras_slice(&self, i: ExtrasIndex) -> H264;
	/// Interpret self as a 256-bit hash, if natively `H256`.
	fn as_h256(&self) -> Option<&H256> { None }
}

impl ExtrasSliceConvertable for H256 {
	fn to_extras_slice(&self, i: ExtrasIndex) -> H264 {
		let mut slice = H264::from_slice(self);
		slice[32] = i as u8;
		slice
	}
	fn as_h256(&self) -> Option<&H256> { Some(self) }
}

impl ExtrasSliceConvertable for U256 {
	fn to_extras_slice(&self, i: ExtrasIndex) -> H264 {
		H256::from(self).to_extras_slice(i)
	}
}

// NICE: make less horrible.
impl ExtrasSliceConvertable for BlockNumber {
	fn to_extras_slice(&self, i: ExtrasIndex) -> H264 {
		U256::from(*self).to_extras_slice(i)
	}
}

/// Types implementing this trait can be indexed in extras database
pub trait ExtrasIndexable {
	/// TODO [debris] Please document me
	fn extras_index() -> ExtrasIndex;
}

impl ExtrasIndexable for H256 {
	fn extras_index() -> ExtrasIndex {
		ExtrasIndex::BlockHash
	}
}

/// Familial details concerning a block
#[derive(Debug, Clone)]
pub struct BlockDetails {
	/// TODO [debris] Please document me
	pub number: BlockNumber,
	/// TODO [debris] Please document me
	pub total_difficulty: U256,
	/// TODO [debris] Please document me
	pub parent: H256,
	/// TODO [debris] Please document me
	pub children: Vec<H256>
}

impl ExtrasIndexable for BlockDetails {
	fn extras_index() -> ExtrasIndex {
		ExtrasIndex::BlockDetails
	}
}

impl HeapSizeOf for BlockDetails {
	fn heap_size_of_children(&self) -> usize {
		self.children.heap_size_of_children()
	}
}

impl Decodable for BlockDetails {
	fn decode<D>(decoder: &D) -> Result<Self, DecoderError> where D: Decoder {
		let d = decoder.as_rlp();
		let details = BlockDetails {
			number: try!(d.val_at(0)),
			total_difficulty: try!(d.val_at(1)),
			parent: try!(d.val_at(2)),
			children: try!(d.val_at(3)),
		};
		Ok(details)
	}
}

impl Encodable for BlockDetails {
	fn rlp_append(&self, s: &mut RlpStream) {
		s.begin_list(4);
		s.append(&self.number);
		s.append(&self.total_difficulty);
		s.append(&self.parent);
		s.append(&self.children);
	}
}

/// Log blooms of certain block
#[derive(Clone)]
pub struct BlockLogBlooms {
	/// TODO [debris] Please document me
	pub blooms: Vec<H2048>
}

impl ExtrasIndexable for BlockLogBlooms {
	fn extras_index() -> ExtrasIndex {
		ExtrasIndex::BlockLogBlooms
	}
}

impl HeapSizeOf for BlockLogBlooms {
	fn heap_size_of_children(&self) -> usize {
		self.blooms.heap_size_of_children()
	}
}

impl Decodable for BlockLogBlooms {
	fn decode<D>(decoder: &D) -> Result<Self, DecoderError> where D: Decoder {
		let block_blooms = BlockLogBlooms {
			blooms: try!(Decodable::decode(decoder))
		};

		Ok(block_blooms)
	}
}

impl Encodable for BlockLogBlooms {
	fn rlp_append(&self, s: &mut RlpStream) {
		s.append(&self.blooms);
	}
}

/// Neighboring log blooms on certain level
pub struct BlocksBlooms {
	/// TODO [debris] Please document me
	pub blooms: [H2048; 16]
}

impl ExtrasIndexable for BlocksBlooms {
	fn extras_index() -> ExtrasIndex {
		ExtrasIndex::BlocksBlooms
	}
}

impl HeapSizeOf for BlocksBlooms {
	fn heap_size_of_children(&self) -> usize { 0 }
}

impl Clone for BlocksBlooms {
	fn clone(&self) -> Self {
		let mut blooms: [H2048; 16] = unsafe { ::std::mem::uninitialized() };

		for i in 0..self.blooms.len() {
			blooms[i] = self.blooms[i].clone();
		}

		BlocksBlooms {
			blooms: blooms
		}
	}
}

impl Decodable for BlocksBlooms {
	fn decode<D>(decoder: &D) -> Result<Self, DecoderError> where D: Decoder {
		let blocks_blooms = BlocksBlooms {
			blooms: try!(Decodable::decode(decoder))
		};

		Ok(blocks_blooms)
	}
}

impl Encodable for BlocksBlooms {
	fn rlp_append(&self, s: &mut RlpStream) {
		let blooms_ref: &[H2048] = &self.blooms;
		s.append(&blooms_ref);
	}
}

/// Represents address of certain transaction within block
#[derive(Clone)]
pub struct TransactionAddress {
	/// TODO [debris] Please document me
	pub block_hash: H256,
	/// TODO [debris] Please document me
	pub index: u64
}

impl ExtrasIndexable for TransactionAddress {
	fn extras_index() -> ExtrasIndex {
		ExtrasIndex::TransactionAddress
	}
}

impl HeapSizeOf for TransactionAddress {
	fn heap_size_of_children(&self) -> usize { 0 }
}

impl Decodable for TransactionAddress {
	fn decode<D>(decoder: &D) -> Result<Self, DecoderError> where D: Decoder {
		let d = decoder.as_rlp();
		let tx_address = TransactionAddress {
			block_hash: try!(d.val_at(0)),
			index: try!(d.val_at(1)),
		};

		Ok(tx_address)
	}
}

impl Encodable for TransactionAddress {
	fn rlp_append(&self, s: &mut RlpStream) {
		s.begin_list(2);
		s.append(&self.block_hash);
		s.append(&self.index);
	}
}