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    //! Bitcoin trainsaction.
    //! https://en.bitcoin.it/wiki/Protocol_documentation#tx

    use std::io;
    use heapsize::HeapSizeOf;
    use hex::FromHex;
    use bytes::Bytes;
    use ser::{deserialize, serialize, serialize_with_flags, SERIALIZE_TRANSACTION_WITNESS};
    use crypto::dhash256;
    use hash::H256;
    use constants::{SEQUENCE_FINAL, LOCKTIME_THRESHOLD};
    use ser::{Error, Serializable, Deserializable, Stream, Reader};

    /// Must be zero.
    const WITNESS_MARKER: u8 = 0;
    /// Must be nonzero.
    const WITNESS_FLAG: u8 = 1;

    #[derive(Debug, PartialEq, Eq, Clone, Default, Serializable, Deserializable)]
    pub struct OutPoint {
    	pub hash: H256,
    	pub index: u32,
    }

    impl OutPoint {
    	pub fn null() -> Self {
    		OutPoint {
    			hash: H256::default(),
    			index: u32::max_value(),
    		}
    	}

    	pub fn is_null(&self) -> bool {
    		self.hash.is_zero() && self.index == u32::max_value()
    	}
    }

    #[derive(Debug, PartialEq, Default, Clone)]
    pub struct TransactionInput {
    	pub previous_output: OutPoint,
    	pub script_sig: Bytes,
    	pub sequence: u32,
    	pub script_witness: Vec<Bytes>,
    }

    impl TransactionInput {
    	pub fn coinbase(script_sig: Bytes) -> Self {
    		TransactionInput {
    			previous_output: OutPoint::null(),
    			script_sig: script_sig,
    			sequence: SEQUENCE_FINAL,
    			script_witness: vec![],
    		}
    	}

    	pub fn is_final(&self) -> bool {
    		self.sequence == SEQUENCE_FINAL
    	}

    	pub fn has_witness(&self) -> bool {
    		!self.script_witness.is_empty()
    	}
    }

    impl HeapSizeOf for TransactionInput {
    	fn heap_size_of_children(&self) -> usize {
    		self.script_sig.heap_size_of_children() +
    			self.script_witness.heap_size_of_children()
    	}
    }

    #[derive(Debug, PartialEq, Clone, Serializable, Deserializable)]
    pub struct TransactionOutput {
    	pub value: u64,
    	pub script_pubkey: Bytes,
    }

    impl Default for TransactionOutput {
    	fn default() -> Self {
    		TransactionOutput {
    			value: 0xffffffffffffffffu64,
    			script_pubkey: Bytes::default(),
    		}
    	}
    }

    impl HeapSizeOf for TransactionOutput {
    	fn heap_size_of_children(&self) -> usize {
    		self.script_pubkey.heap_size_of_children()
    	}
    }

    #[derive(Debug, PartialEq, Default, Clone)]
    pub struct Transaction {
    	pub version: i32,
    	pub inputs: Vec<TransactionInput>,
    	pub outputs: Vec<TransactionOutput>,
    	pub lock_time: u32,
    }

    impl From<&'static str> for Transaction {
    	fn from(s: &'static str) -> Self {
    		deserialize(&s.from_hex::<Vec<u8>>().unwrap() as &[u8]).unwrap()
    	}
    }

    impl HeapSizeOf for Transaction {
    	fn heap_size_of_children(&self) -> usize {
    		self.inputs.heap_size_of_children() + self.outputs.heap_size_of_children()
    	}
    }

    impl Transaction {
    	pub fn hash(&self) -> H256 {
    		dhash256(&serialize(self))
    	}

    	pub fn witness_hash(&self) -> H256 {
    		dhash256(&serialize_with_flags(self, SERIALIZE_TRANSACTION_WITNESS))
    	}

    	pub fn inputs(&self) -> &[TransactionInput] {
    		&self.inputs
    	}

    	pub fn outputs(&self) -> &[TransactionOutput] {
    		&self.outputs
    	}

    	pub fn is_empty(&self) -> bool {
    		self.inputs.is_empty() || self.outputs.is_empty()
    	}

    	pub fn is_null(&self) -> bool {
    		self.inputs.iter().any(|input| input.previous_output.is_null())
    	}

    	pub fn is_coinbase(&self) -> bool {
    		self.inputs.len() == 1 && self.inputs[0].previous_output.is_null()
    	}

    	pub fn is_final(&self) -> bool {
    		// if lock_time is 0, transaction is final
    		if self.lock_time == 0 {
    			return true;
    		}
    		// setting all sequence numbers to 0xffffffff disables the time lock, so if you want to use locktime,
    		// at least one input must have a sequence number below the maximum.
    		self.inputs.iter().all(TransactionInput::is_final)
    	}

    	pub fn is_final_in_block(&self, block_height: u32, block_time: u32) -> bool {
    		if self.lock_time == 0 {
    			return true;
    		}

    		let max_lock_time = if self.lock_time < LOCKTIME_THRESHOLD {
    			block_height
    		} else {
    			block_time
    		};

    		if self.lock_time < max_lock_time {
    			return true;
    		}

    		self.inputs.iter().all(TransactionInput::is_final)
    	}

    	pub fn has_witness(&self) -> bool {
    		self.inputs.iter().any(TransactionInput::has_witness)
    	}

    	pub fn total_spends(&self) -> u64 {
    		let mut result = 0u64;
    		for output in self.outputs.iter() {
    			if u64::max_value() - result < output.value {
    				return u64::max_value();
    			}
    			result += output.value;
    		}
    		result
    	}
    }

    impl Serializable for TransactionInput {
    	fn serialize(&self, stream: &mut Stream) {
    		stream
    			.append(&self.previous_output)
    			.append(&self.script_sig)
    			.append(&self.sequence);
    	}
    }

    impl Deserializable for TransactionInput {
    	fn deserialize<T>(reader: &mut Reader<T>) -> Result<Self, Error> where Self: Sized, T: io::Read {
    		Ok(TransactionInput {
    			previous_output: reader.read()?,
    			script_sig: reader.read()?,
    			sequence: reader.read()?,
    			script_witness: vec![],
    		})
    	}
    }

    impl Serializable for Transaction {
    	fn serialize(&self, stream: &mut Stream) {
    		let include_transaction_witness = stream.include_transaction_witness() && self.has_witness();
    		match include_transaction_witness {
    			false => stream
    				.append(&self.version)
    				.append_list(&self.inputs)
    				.append_list(&self.outputs)
    				.append(&self.lock_time),
    			true => {
    				stream
    					.append(&self.version)
    					.append(&WITNESS_MARKER)
    					.append(&WITNESS_FLAG)
    					.append_list(&self.inputs)
    					.append_list(&self.outputs);
    				for input in &self.inputs {
    					stream.append_list(&input.script_witness);
    				}
    				stream.append(&self.lock_time)
    			}
    		};
    	}
    }

    impl Deserializable for Transaction {
    	fn deserialize<T>(reader: &mut Reader<T>) -> Result<Self, Error> where Self: Sized, T: io::Read {
    		let version = reader.read()?;
    		let mut inputs: Vec<TransactionInput> = reader.read_list()?;
    		let read_witness = if inputs.is_empty() {
    			let witness_flag: u8 = reader.read()?;
    			if witness_flag != WITNESS_FLAG {
    				return Err(Error::MalformedData);
    			}

    			inputs = reader.read_list()?;
    			true
    		} else {
    			false
    		};
    		let outputs = reader.read_list()?;
    		if read_witness {
    			for input in inputs.iter_mut() {
    				input.script_witness = reader.read_list()?;
    			}
    		}

    		Ok(Transaction {
    			version: version,
    			inputs: inputs,
    			outputs: outputs,
    			lock_time: reader.read()?,
    		})
    	}
    }

    #[cfg(test)]
    mod tests {
    	use hash::H256;
    	use ser::{Serializable, serialize_with_flags, SERIALIZE_TRANSACTION_WITNESS};
    	use super::{Transaction, TransactionInput, OutPoint, TransactionOutput};

    	// real transaction from block 80000
    	// https://blockchain.info/rawtx/5a4ebf66822b0b2d56bd9dc64ece0bc38ee7844a23ff1d7320a88c5fdb2ad3e2
    	// https://blockchain.info/rawtx/5a4ebf66822b0b2d56bd9dc64ece0bc38ee7844a23ff1d7320a88c5fdb2ad3e2?format=hex
    	#[test]
    	fn test_transaction_reader() {
    		let t: Transaction = "0100000001a6b97044d03da79c005b20ea9c0e1a6d9dc12d9f7b91a5911c9030a439eed8f5000000004948304502206e21798a42fae0e854281abd38bacd1aeed3ee3738d9e1446618c4571d1090db022100e2ac980643b0b82c0e88ffdfec6b64e3e6ba35e7ba5fdd7d5d6cc8d25c6b241501ffffffff0100f2052a010000001976a914404371705fa9bd789a2fcd52d2c580b65d35549d88ac00000000".into();
    		assert_eq!(t.version, 1);
    		assert_eq!(t.lock_time, 0);
    		assert_eq!(t.inputs.len(), 1);
    		assert_eq!(t.outputs.len(), 1);
    		let tx_input = &t.inputs[0];
    		assert_eq!(tx_input.sequence, 4294967295);
    		assert_eq!(tx_input.script_sig, "48304502206e21798a42fae0e854281abd38bacd1aeed3ee3738d9e1446618c4571d1090db022100e2ac980643b0b82c0e88ffdfec6b64e3e6ba35e7ba5fdd7d5d6cc8d25c6b241501".into());
    		let tx_output = &t.outputs[0];
    		assert_eq!(tx_output.value, 5000000000);
    		assert_eq!(tx_output.script_pubkey, "76a914404371705fa9bd789a2fcd52d2c580b65d35549d88ac".into());
    		assert!(!t.has_witness());
    	}

    	#[test]
    	fn test_transaction_hash() {
    		let t: Transaction = "0100000001a6b97044d03da79c005b20ea9c0e1a6d9dc12d9f7b91a5911c9030a439eed8f5000000004948304502206e21798a42fae0e854281abd38bacd1aeed3ee3738d9e1446618c4571d1090db022100e2ac980643b0b82c0e88ffdfec6b64e3e6ba35e7ba5fdd7d5d6cc8d25c6b241501ffffffff0100f2052a010000001976a914404371705fa9bd789a2fcd52d2c580b65d35549d88ac00000000".into();
    		let hash = H256::from_reversed_str("5a4ebf66822b0b2d56bd9dc64ece0bc38ee7844a23ff1d7320a88c5fdb2ad3e2");
    		assert_eq!(t.hash(), hash);
    	}

    	#[test]
    	fn test_transaction_serialized_len() {
    		let raw_tx: &'static str = "0100000001a6b97044d03da79c005b20ea9c0e1a6d9dc12d9f7b91a5911c9030a439eed8f5000000004948304502206e21798a42fae0e854281abd38bacd1aeed3ee3738d9e1446618c4571d1090db022100e2ac980643b0b82c0e88ffdfec6b64e3e6ba35e7ba5fdd7d5d6cc8d25c6b241501ffffffff0100f2052a010000001976a914404371705fa9bd789a2fcd52d2c580b65d35549d88ac00000000";
    		let tx: Transaction = raw_tx.into();
    		assert_eq!(tx.serialized_size(), raw_tx.len() / 2);
    	}

    	#[test]
    	fn test_transaction_reader_with_witness() {
    		// test case from https://github.com/bitcoin/bips/blob/master/bip-0143.mediawiki
    		let actual: Transaction = " ".into();
    		let expected = Transaction {
    			version: 1,
    			inputs: vec![TransactionInput {
    				previous_output: OutPoint {
    					hash: "fff7f7881a8099afa6940d42d1e7f6362bec38171ea3edf433541db4e4ad969f".into(),
    					index: 0,
    				},
    				script_sig: "4830450221008b9d1dc26ba6a9cb62127b02742fa9d754cd3bebf337f7a55d114c8e5cdd30be022040529b194ba3f9281a99f2b1c0a19c0489bc22ede944ccf4ecbab4cc618ef3ed01".into(),
    				sequence: 0xffffffee,
    				script_witness: vec![],
    			}, TransactionInput {
    				previous_output: OutPoint {
    					hash: "ef51e1b804cc89d182d279655c3aa89e815b1b309fe287d9b2b55d57b90ec68a".into(),
    					index: 1,
    				},
    				script_sig: "".into(),
    				sequence: 0xffffffff,
    				script_witness: vec![
    					"304402203609e17b84f6a7d30c80bfa610b5b4542f32a8a0d5447a12fb1366d7f01cc44a0220573a954c4518331561406f90300e8f3358f51928d43c212a8caed02de67eebee01".into(),
    					"025476c2e83188368da1ff3e292e7acafcdb3566bb0ad253f62fc70f07aeee6357".into(),
    				],
    			}],
    			outputs: vec![TransactionOutput {
    				value: 0x0000000006b22c20,
    				script_pubkey: "76a9148280b37df378db99f66f85c95a783a76ac7a6d5988ac".into(),
    			}, TransactionOutput {
    				value: 0x000000000d519390,
    				script_pubkey: "76a9143bde42dbee7e4dbe6a21b2d50ce2f0167faa815988ac".into(),
    			}],
    			lock_time: 0x00000011,
    		};
    		assert_eq!(actual, expected);
    	}

    	#[test]
    	fn test_serialization_with_flags() {
    		let transaction_without_witness: Transaction = "000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000".into();
    		assert_eq!(serialize_with_flags(&transaction_without_witness, 0), serialize_with_flags(&transaction_without_witness, SERIALIZE_TRANSACTION_WITNESS));

    		let transaction_with_witness: Transaction = "0000000000010100000000000000000000000000000000000000000000000000000000000000000000000000000000000001010000000000".into();
    		assert!(serialize_with_flags(&transaction_with_witness, 0) != serialize_with_flags(&transaction_with_witness, SERIALIZE_TRANSACTION_WITNESS));
    	}

    	#[test]
    	fn test_witness_hash_differs() {
    		let transaction_without_witness: Transaction = "000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000".into();
    		assert_eq!(transaction_without_witness.hash(), transaction_without_witness.witness_hash());

    		let transaction_with_witness: Transaction = "0000000000010100000000000000000000000000000000000000000000000000000000000000000000000000000000000001010000000000".into();
    		assert!(transaction_with_witness.hash() != transaction_with_witness.witness_hash());
    	}
    }

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