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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/>.

    //! General bytes-related utilities.
    //!
    //! Includes a pretty-printer for bytes, in the form of `ToPretty` and `PrettySlice`
    //! as

    use std::fmt;
    use std::cmp::min;
    use std::ops::{Deref, DerefMut};

    /// Slice pretty print helper
    pub struct PrettySlice<'a> (&'a [u8]);

    impl<'a> fmt::Debug for PrettySlice<'a> {
    	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    		for i in 0..self.0.len() {
    			match i > 0 {
    				true => { write!(f, "·{:02x}", self.0[i])?; },
    				false => { write!(f, "{:02x}", self.0[i])?; },
    			}
    		}
    		Ok(())
    	}
    }

    impl<'a> fmt::Display for PrettySlice<'a> {
    	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    		for i in 0..self.0.len() {
    			write!(f, "{:02x}", self.0[i])?;
    		}
    		Ok(())
    	}
    }

    /// Trait to allow a type to be pretty-printed in `format!`, where unoverridable
    /// defaults cannot otherwise be avoided.
    pub trait ToPretty {
    	/// Convert a type into a derivative form in order to make `format!` print it prettily.
    	fn pretty(&self) -> PrettySlice;
    	/// Express the object as a hex string.
    	fn to_hex(&self) -> String {
    		format!("{}", self.pretty())
    	}
    }

    impl<T: AsRef<[u8]>> ToPretty for T {
    	fn pretty(&self) -> PrettySlice {
    		PrettySlice(self.as_ref())
    	}
    }

    /// A byte collection reference that can either be a slice or a vector
    pub enum BytesRef<'a> {
    	/// This is a reference to a vector
    	Flexible(&'a mut Bytes),
    	/// This is a reference to a slice
    	Fixed(&'a mut [u8])
    }

    impl<'a> BytesRef<'a> {
    	/// Writes given `input` to this `BytesRef` starting at `offset`.
    	/// Returns number of bytes written to the ref.
    	/// NOTE can return number greater then `input.len()` in case flexible vector had to be extended.
    	pub fn write(&mut self, offset: usize, input: &[u8]) -> usize {
    		match *self {
    			BytesRef::Flexible(ref mut data) => {
    				let data_len = data.len();
    				let wrote = input.len() + if data_len > offset { 0 } else { offset - data_len };

    				data.resize(offset, 0);
    				data.extend_from_slice(input);
    				wrote
    			},
    			BytesRef::Fixed(ref mut data) if offset < data.len() => {
    				let max = min(data.len() - offset, input.len());
    				for i in 0..max {
    					data[offset + i] = input[i];
    				}
    				max
    			},
    			_ => 0
    		}
    	}
    }

    impl<'a> Deref for BytesRef<'a> {
    	type Target = [u8];

    	fn deref(&self) -> &[u8] {
    		match *self {
    			BytesRef::Flexible(ref bytes) => bytes,
    			BytesRef::Fixed(ref bytes) => bytes,
    		}
    	}
    }

    impl <'a> DerefMut for BytesRef<'a> {
    	fn deref_mut(&mut self) -> &mut [u8] {
    		match *self {
    			BytesRef::Flexible(ref mut bytes) => bytes,
    			BytesRef::Fixed(ref mut bytes) => bytes,
    		}
    	}
    }

    /// Vector of bytes.
    pub type Bytes = Vec<u8>;

    #[cfg(test)]
    mod tests {
    	use super::BytesRef;

    	#[test]
    	fn should_write_bytes_to_fixed_bytesref() {
    		// given
    		let mut data1 = vec![0, 0, 0];
    		let mut data2 = vec![0, 0, 0];
    		let (res1, res2) = {
    			let mut bytes1 = BytesRef::Fixed(&mut data1[..]);
    			let mut bytes2 = BytesRef::Fixed(&mut data2[1..2]);

    			// when
    			let res1 = bytes1.write(1, &[1, 1, 1]);
    			let res2 = bytes2.write(3, &[1, 1, 1]);
    			(res1, res2)
    		};

    		// then
    		assert_eq!(&data1, &[0, 1, 1]);
    		assert_eq!(res1, 2);

    		assert_eq!(&data2, &[0, 0, 0]);
    		assert_eq!(res2, 0);
    	}

    	#[test]
    	fn should_write_bytes_to_flexible_bytesref() {
    		// given
    		let mut data1 = vec![0, 0, 0];
    		let mut data2 = vec![0, 0, 0];
    		let mut data3 = vec![0, 0, 0];
    		let (res1, res2, res3) = {
    			let mut bytes1 = BytesRef::Flexible(&mut data1);
    			let mut bytes2 = BytesRef::Flexible(&mut data2);
    			let mut bytes3 = BytesRef::Flexible(&mut data3);

    			// when
    			let res1 = bytes1.write(1, &[1, 1, 1]);
    			let res2 = bytes2.write(3, &[1, 1, 1]);
    			let res3 = bytes3.write(5, &[1, 1, 1]);
    			(res1, res2, res3)
    		};

    		// then
    		assert_eq!(&data1, &[0, 1, 1, 1]);
    		assert_eq!(res1, 3);

    		assert_eq!(&data2, &[0, 0, 0, 1, 1, 1]);
    		assert_eq!(res2, 3);

    		assert_eq!(&data3, &[0, 0, 0, 0, 0, 1, 1, 1]);
    		assert_eq!(res3, 5);
    	}
    }

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