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    use std::ops;
    use ser::Serializable;
    use chain::IndexedTransaction;
    use network::{ConsensusParams, ConsensusFork};
    use deployments::BlockDeployments;
    use duplex_store::NoopStore;
    use sigops::transaction_sigops;
    use error::TransactionError;
    use constants::{MIN_COINBASE_SIZE, MAX_COINBASE_SIZE};

    pub struct TransactionVerifier<'a> {
    	pub empty: TransactionEmpty<'a>,
    	pub null_non_coinbase: TransactionNullNonCoinbase<'a>,
    	pub oversized_coinbase: TransactionOversizedCoinbase<'a>,
    }

    impl<'a> TransactionVerifier<'a> {
    	pub fn new(transaction: &'a IndexedTransaction) -> Self {
    		trace!(target: "verification", "Tx pre-verification {}", transaction.hash.to_reversed_str());
    		TransactionVerifier {
    			empty: TransactionEmpty::new(transaction),
    			null_non_coinbase: TransactionNullNonCoinbase::new(transaction),
    			oversized_coinbase: TransactionOversizedCoinbase::new(transaction, MIN_COINBASE_SIZE..MAX_COINBASE_SIZE),
    		}
    	}

    	pub fn check(&self) -> Result<(), TransactionError> {
    		try!(self.empty.check());
    		try!(self.null_non_coinbase.check());
    		try!(self.oversized_coinbase.check());
    		Ok(())
    	}
    }

    pub struct MemoryPoolTransactionVerifier<'a> {
    	pub empty: TransactionEmpty<'a>,
    	pub null_non_coinbase: TransactionNullNonCoinbase<'a>,
    	pub is_coinbase: TransactionMemoryPoolCoinbase<'a>,
    	pub size: TransactionSize<'a>,
    	pub premature_witness: TransactionPrematureWitness<'a>,
    	pub sigops: TransactionSigops<'a>,
    }

    impl<'a> MemoryPoolTransactionVerifier<'a> {
    	pub fn new(transaction: &'a IndexedTransaction, consensus: &'a ConsensusParams, deployments: &'a BlockDeployments<'a>) -> Self {
    		trace!(target: "verification", "Mempool-Tx pre-verification {}", transaction.hash.to_reversed_str());
    		MemoryPoolTransactionVerifier {
    			empty: TransactionEmpty::new(transaction),
    			null_non_coinbase: TransactionNullNonCoinbase::new(transaction),
    			is_coinbase: TransactionMemoryPoolCoinbase::new(transaction),
    			size: TransactionSize::new(transaction, consensus),
    			premature_witness: TransactionPrematureWitness::new(transaction, &deployments),
    			sigops: TransactionSigops::new(transaction, ConsensusFork::absolute_maximum_block_sigops()),
    		}
    	}

    	pub fn check(&self) -> Result<(), TransactionError> {
    		try!(self.empty.check());
    		try!(self.null_non_coinbase.check());
    		try!(self.is_coinbase.check());
    		try!(self.size.check());
    		try!(self.premature_witness.check());
    		try!(self.sigops.check());
    		Ok(())
    	}
    }

    pub struct TransactionEmpty<'a> {
    	transaction: &'a IndexedTransaction,
    }

    impl<'a> TransactionEmpty<'a> {
    	fn new(transaction: &'a IndexedTransaction) -> Self {
    		TransactionEmpty {
    			transaction: transaction,
    		}
    	}

    	fn check(&self) -> Result<(), TransactionError> {
    		if self.transaction.raw.is_empty() {
    			Err(TransactionError::Empty)
    		} else {
    			Ok(())
    		}
    	}
    }

    pub struct TransactionNullNonCoinbase<'a> {
    	transaction: &'a IndexedTransaction,
    }

    impl<'a> TransactionNullNonCoinbase<'a> {
    	fn new(transaction: &'a IndexedTransaction) -> Self {
    		TransactionNullNonCoinbase {
    			transaction: transaction,
    		}
    	}

    	fn check(&self) -> Result<(), TransactionError> {
    		if !self.transaction.raw.is_coinbase() && self.transaction.raw.is_null() {
    			Err(TransactionError::NullNonCoinbase)
    		} else {
    			Ok(())
    		}
    	}
    }

    pub struct TransactionOversizedCoinbase<'a> {
    	transaction: &'a IndexedTransaction,
    	size_range: ops::Range<usize>,
    }

    impl<'a> TransactionOversizedCoinbase<'a> {
    	fn new(transaction: &'a IndexedTransaction, size_range: ops::Range<usize>) -> Self {
    		TransactionOversizedCoinbase {
    			transaction: transaction,
    			size_range: size_range,
    		}
    	}

    	fn check(&self) -> Result<(), TransactionError> {
    		if self.transaction.raw.is_coinbase() {
    			let script_len = self.transaction.raw.inputs[0].script_sig.len();
    			if script_len < self.size_range.start || script_len > self.size_range.end {
    				return Err(TransactionError::CoinbaseSignatureLength(script_len));
    			}
    		}

    		Ok(())
    	}
    }

    pub struct TransactionMemoryPoolCoinbase<'a> {
    	transaction: &'a IndexedTransaction,
    }
    impl<'a> TransactionMemoryPoolCoinbase<'a> {
    	fn new(transaction: &'a IndexedTransaction) -> Self {
    		TransactionMemoryPoolCoinbase {
    			transaction: transaction,
    		}
    	}

    	fn check(&self) -> Result<(), TransactionError> {
    		if self.transaction.raw.is_coinbase() {
    			Err(TransactionError::MemoryPoolCoinbase)
    		} else {
    			Ok(())
    		}
    	}
    }

    pub struct TransactionSize<'a> {
    	transaction: &'a IndexedTransaction,
    	consensus: &'a ConsensusParams,
    }

    impl<'a> TransactionSize<'a> {
    	fn new(transaction: &'a IndexedTransaction, consensus: &'a ConsensusParams) -> Self {
    		TransactionSize {
    			transaction: transaction,
    			consensus: consensus,
    		}
    	}

    	fn check(&self) -> Result<(), TransactionError> {
    		let size = self.transaction.raw.serialized_size();
    		if size > self.consensus.fork.max_transaction_size() {
    			Err(TransactionError::MaxSize)
    		} else {
    			Ok(())
    		}
    	}
    }

    pub struct TransactionSigops<'a> {
    	transaction: &'a IndexedTransaction,
    	max_sigops: usize,
    }

    impl<'a> TransactionSigops<'a> {
    	fn new(transaction: &'a IndexedTransaction, max_sigops: usize) -> Self {
    		TransactionSigops {
    			transaction: transaction,
    			max_sigops: max_sigops,
    		}
    	}

    	fn check(&self) -> Result<(), TransactionError> {
    		let sigops = transaction_sigops(&self.transaction.raw, &NoopStore, false, false);
    		if sigops > self.max_sigops {
    			Err(TransactionError::MaxSigops)
    		} else {
    			Ok(())
    		}
    	}
    }

    pub struct TransactionPrematureWitness<'a> {
    	transaction: &'a IndexedTransaction,
    	segwit_active: bool,
    }

    impl<'a> TransactionPrematureWitness<'a> {
    	pub fn new(transaction: &'a IndexedTransaction, deployments: &'a BlockDeployments<'a>) -> Self {
    		let segwit_active = deployments.segwit();

    		TransactionPrematureWitness {
    			transaction: transaction,
    			segwit_active: segwit_active,
    		}
    	}

    	pub fn check(&self) -> Result<(), TransactionError> {
    		if !self.segwit_active && self.transaction.raw.has_witness() {
    			Err(TransactionError::PrematureWitness)
    		} else {
    			Ok(())
    		}
    	}
    }

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