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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/>.

    //! Block header.

    use util::*;
    use basic_types::{LogBloom, Seal, ZERO_LOGBLOOM};
    use time::get_time;
    use rlp::*;

    use std::cell::RefCell;

    /// Type for Block number
    pub type BlockNumber = u64;

    /// A block header.
    ///
    /// Reflects the specific RLP fields of a block in the chain with additional room for the seal
    /// which is non-specific.
    ///
    /// Doesn't do all that much on its own.
    #[derive(Debug, Clone, Eq)]
    pub struct Header {
    	/// Parent hash.
    	parent_hash: H256,
    	/// Block timestamp.
    	timestamp: u64,
    	/// Block number.
    	number: BlockNumber,
    	/// Block author.
    	author: Address,

    	/// Transactions root.
    	transactions_root: H256,
    	/// Block uncles hash.
    	uncles_hash: H256,
    	/// Block extra data.
    	extra_data: Bytes,

    	/// State root.
    	state_root: H256,
    	/// Block receipts root.
    	receipts_root: H256,
    	/// Block bloom.
    	log_bloom: LogBloom,
    	/// Gas used for contracts execution.
    	gas_used: U256,
    	/// Block gas limit.
    	gas_limit: U256,

    	/// Block difficulty.
    	difficulty: U256,
    	/// Vector of post-RLP-encoded fields.
    	seal: Vec<Bytes>,

    	/// The memoized hash of the RLP representation *including* the seal fields.
    	hash: RefCell<Option<H256>>,
    	/// The memoized hash of the RLP representation *without* the seal fields.
    	bare_hash: RefCell<Option<H256>>,
    }

    impl PartialEq for Header {
    	fn eq(&self, c: &Header) -> bool {
    		self.parent_hash == c.parent_hash &&
    		self.timestamp == c.timestamp &&
    		self.number == c.number &&
    		self.author == c.author &&
    		self.transactions_root == c.transactions_root &&
    		self.uncles_hash == c.uncles_hash &&
    		self.extra_data == c.extra_data &&
    		self.state_root == c.state_root &&
    		self.receipts_root == c.receipts_root &&
    		self.log_bloom == c.log_bloom &&
    		self.gas_used == c.gas_used &&
    		self.gas_limit == c.gas_limit &&
    		self.difficulty == c.difficulty &&
    		self.seal == c.seal
    	}
    }

    impl Default for Header {
    	fn default() -> Self {
    		Header {
    			parent_hash: H256::default(),
    			timestamp: 0,
    			number: 0,
    			author: Address::default(),

    			transactions_root: SHA3_NULL_RLP,
    			uncles_hash: SHA3_EMPTY_LIST_RLP,
    			extra_data: vec![],

    			state_root: SHA3_NULL_RLP,
    			receipts_root: SHA3_NULL_RLP,
    			log_bloom: ZERO_LOGBLOOM.clone(),
    			gas_used: U256::default(),
    			gas_limit: U256::default(),

    			difficulty: U256::default(),
    			seal: vec![],
    			hash: RefCell::new(None),
    			bare_hash: RefCell::new(None),
    		}
    	}
    }

    impl Header {
    	/// Create a new, default-valued, header.
    	pub fn new() -> Self {
    		Self::default()
    	}

    	/// Get the parent_hash field of the header.
    	pub fn parent_hash(&self) -> &H256 { &self.parent_hash }
    	/// Get the timestamp field of the header.
    	pub fn timestamp(&self) -> u64 { self.timestamp }
    	/// Get the number field of the header.
    	pub fn number(&self) -> BlockNumber { self.number }
    	/// Get the author field of the header.
    	pub fn author(&self) -> &Address { &self.author }

    	/// Get the extra data field of the header.
    	pub fn extra_data(&self) -> &Bytes { &self.extra_data }
    	/// Get a mutable reference to extra_data
    	pub fn extra_data_mut(&mut self) -> &mut Bytes { self.note_dirty(); &mut self.extra_data }

    	/// Get the state root field of the header.
    	pub fn state_root(&self) -> &H256 { &self.state_root }
    	/// Get the receipts root field of the header.
    	pub fn receipts_root(&self) -> &H256 { &self.receipts_root }
    	/// Get the log bloom field of the header.
    	pub fn log_bloom(&self) -> &LogBloom { &self.log_bloom }
    	/// Get the transactions root field of the header.
    	pub fn transactions_root(&self) -> &H256 { &self.transactions_root }
    	/// Get the uncles hash field of the header.
    	pub fn uncles_hash(&self) -> &H256 { &self.uncles_hash }
    	/// Get the gas used field of the header.
    	pub fn gas_used(&self) -> &U256 { &self.gas_used }
    	/// Get the gas limit field of the header.
    	pub fn gas_limit(&self) -> &U256 { &self.gas_limit }

    	/// Get the difficulty field of the header.
    	pub fn difficulty(&self) -> &U256 { &self.difficulty }
    	/// Get the seal field of the header.
    	pub fn seal(&self) -> &[Bytes] { &self.seal }

    	// TODO: seal_at, set_seal_at &c.

    	/// Set the number field of the header.
    	pub fn set_parent_hash(&mut self, a: H256) { self.parent_hash = a; self.note_dirty(); }
    	/// Set the uncles hash field of the header.
    	pub fn set_uncles_hash(&mut self, a: H256) { self.uncles_hash = a; self.note_dirty(); }
    	/// Set the state root field of the header.
    	pub fn set_state_root(&mut self, a: H256) { self.state_root = a; self.note_dirty(); }
    	/// Set the transactions root field of the header.
    	pub fn set_transactions_root(&mut self, a: H256) { self.transactions_root = a; self.note_dirty() }
    	/// Set the receipts root field of the header.
    	pub fn set_receipts_root(&mut self, a: H256) { self.receipts_root = a; self.note_dirty() }
    	/// Set the log bloom field of the header.
    	pub fn set_log_bloom(&mut self, a: LogBloom) { self.log_bloom = a; self.note_dirty() }
    	/// Set the timestamp field of the header.
    	pub fn set_timestamp(&mut self, a: u64) { self.timestamp = a; self.note_dirty(); }
    	/// Set the timestamp field of the header to the current time.
    	pub fn set_timestamp_now(&mut self, but_later_than: u64) { self.timestamp = max(get_time().sec as u64, but_later_than + 1); self.note_dirty(); }
    	/// Set the number field of the header.
    	pub fn set_number(&mut self, a: BlockNumber) { self.number = a; self.note_dirty(); }
    	/// Set the author field of the header.
    	pub fn set_author(&mut self, a: Address) { if a != self.author { self.author = a; self.note_dirty(); } }

    	/// Set the extra data field of the header.
    	pub fn set_extra_data(&mut self, a: Bytes) { if a != self.extra_data { self.extra_data = a; self.note_dirty(); } }

    	/// Set the gas used field of the header.
    	pub fn set_gas_used(&mut self, a: U256) { self.gas_used = a; self.note_dirty(); }
    	/// Set the gas limit field of the header.
    	pub fn set_gas_limit(&mut self, a: U256) { self.gas_limit = a; self.note_dirty(); }

    	/// Set the difficulty field of the header.
    	pub fn set_difficulty(&mut self, a: U256) { self.difficulty = a; self.note_dirty(); }
    	/// Set the seal field of the header.
    	pub fn set_seal(&mut self, a: Vec<Bytes>) { self.seal = a; self.note_dirty(); }

    	/// Get the hash of this header (sha3 of the RLP).
    	pub fn hash(&self) -> H256 {
     		let mut hash = self.hash.borrow_mut();
     		match &mut *hash {
     			&mut Some(ref h) => h.clone(),
     			hash @ &mut None => {
    				let h = self.rlp_sha3(Seal::With);
     				*hash = Some(h.clone());
     				h
     			}
    		}
    	}

    	/// Get the hash of the header excluding the seal
    	pub fn bare_hash(&self) -> H256 {
    		let mut hash = self.bare_hash.borrow_mut();
    		match &mut *hash {
    			&mut Some(ref h) => h.clone(),
    			hash @ &mut None => {
    				let h = self.rlp_sha3(Seal::Without);
    				*hash = Some(h.clone());
    				h
    			}
    		}
    	}

    	/// Note that some fields have changed. Resets the memoised hash.
    	pub fn note_dirty(&self) {
     		*self.hash.borrow_mut() = None;
     		*self.bare_hash.borrow_mut() = None;
    	}

    	// TODO: make these functions traity
    	/// Place this header into an RLP stream `s`, optionally `with_seal`.
    	pub fn stream_rlp(&self, s: &mut RlpStream, with_seal: Seal) {
    		s.begin_list(13 + match with_seal { Seal::With => self.seal.len(), _ => 0 });
    		s.append(&self.parent_hash);
    		s.append(&self.uncles_hash);
    		s.append(&self.author);
    		s.append(&self.state_root);
    		s.append(&self.transactions_root);
    		s.append(&self.receipts_root);
    		s.append(&self.log_bloom);
    		s.append(&self.difficulty);
    		s.append(&self.number);
    		s.append(&self.gas_limit);
    		s.append(&self.gas_used);
    		s.append(&self.timestamp);
    		s.append(&self.extra_data);
    		if let Seal::With = with_seal {
    			for b in &self.seal {
    				s.append_raw(b, 1);
    			}
    		}
    	}

    	/// Get the RLP of this header, optionally `with_seal`.
    	pub fn rlp(&self, with_seal: Seal) -> Bytes {
    		let mut s = RlpStream::new();
    		self.stream_rlp(&mut s, with_seal);
    		s.out()
    	}

    	/// Get the SHA3 (Keccak) of this header, optionally `with_seal`.
    	pub fn rlp_sha3(&self, with_seal: Seal) -> H256 { self.rlp(with_seal).sha3() }
    }

    impl Decodable for Header {
    	fn decode<D>(decoder: &D) -> Result<Self, DecoderError> where D: Decoder {
    		let r = decoder.as_rlp();

    		let mut blockheader = Header {
    			parent_hash: r.val_at(0)?,
    			uncles_hash: r.val_at(1)?,
    			author: r.val_at(2)?,
    			state_root: r.val_at(3)?,
    			transactions_root: r.val_at(4)?,
    			receipts_root: r.val_at(5)?,
    			log_bloom: r.val_at(6)?,
    			difficulty: r.val_at(7)?,
    			number: r.val_at(8)?,
    			gas_limit: r.val_at(9)?,
    			gas_used: r.val_at(10)?,
    			timestamp: r.val_at(11)?,
    			extra_data: r.val_at(12)?,
    			seal: vec![],
    			hash: RefCell::new(Some(r.as_raw().sha3())),
    			bare_hash: RefCell::new(None),
    		};

    		for i in 13..r.item_count() {
    			blockheader.seal.push(r.at(i)?.as_raw().to_vec())
    		}

    		Ok(blockheader)
    	}
    }

    impl Encodable for Header {
    	fn rlp_append(&self, s: &mut RlpStream) {
    		self.stream_rlp(s, Seal::With);
    	}
    }

    impl HeapSizeOf for Header {
    	fn heap_size_of_children(&self) -> usize {
    		self.extra_data.heap_size_of_children() + self.seal.heap_size_of_children()
    	}
    }

    #[cfg(test)]
    mod tests {
    	use rustc_serialize::hex::FromHex;
    	use rlp;
    	use super::Header;

    	#[test]
    	fn test_header_seal_fields() {
    		// that's rlp of block header created with ethash engine.
    		let header_rlp = " ".from_hex().unwrap();
    		let mix_hash = "a0a0349d8c3df71f1a48a9df7d03fd5f14aeee7d91332c009ecaff0a71ead405bd".from_hex().unwrap();
    		let nonce = "88ab4e252a7e8c2a23".from_hex().unwrap();

    		let header: Header = rlp::decode(&header_rlp);
    		let seal_fields = header.seal;
    		assert_eq!(seal_fields.len(), 2);
    		assert_eq!(seal_fields[0], mix_hash);
    		assert_eq!(seal_fields[1], nonce);
    	}

    	#[test]
    	fn decode_and_encode_header() {
    		// that's rlp of block header created with ethash engine.
    		let header_rlp = " ".from_hex().unwrap();

    		let header: Header = rlp::decode(&header_rlp);
    		let encoded_header = rlp::encode(&header).to_vec();

    		assert_eq!(header_rlp, encoded_header);
    	}
    }

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