/*! Fast vint u32 encoding for rust. Uses at most 5 bytes.

# Examples
```
use vint32::encode_varint_into;
let mut output = vec![];
encode_varint_into(&mut output, 50);	
assert_eq!(output.len(), 1);

```

*/

#[cfg(feature = "common-encoding")]
pub mod common_encode;
pub mod iterator;
pub mod vint_array;
pub mod util;

use std::io;
use std::io::Read;
use std::io::Write;

/// `vint32` encode a unsigned 32-bit integer into a vec.
///
/// returns number of bytes written
///
#[inline]
pub fn encode_varint_into(output: &mut Vec<u8>, mut value: u32) -> u8 {
    let do_one = |output: &mut Vec<u8>, value: &mut u32| {
        output.push(((*value & 127) | 128) as u8);
        *value >>= 7;
    };
    let do_last = |output: &mut Vec<u8>, value: u32| {
        output.push((value & 127) as u8);
    };

    if value < 1 << 7 {
        //128
        do_last(output, value);
        1
    } else if value < 1 << 14 {
        do_one(output, &mut value);
        do_last(output, value);
        2
    } else if value < 1 << 21 {
        do_one(output, &mut value);
        do_one(output, &mut value);
        do_last(output, value);
        3
    } else if value < 1 << 28 {
        do_one(output, &mut value);
        do_one(output, &mut value);
        do_one(output, &mut value);
        do_last(output, value);
        4
    } else {
        do_one(output, &mut value);
        do_one(output, &mut value);
        do_one(output, &mut value);
        do_one(output, &mut value);
        do_last(output, value);
        5
    }
}

/// `vint32` encode a unsigned 32-bit integer into a vec.
///
/// returns number of bytes written
///ue`.
#[inline]
pub fn encode_varint_into_writer<W: Write>(mut output: W, mut value: u32) -> Result<u8, io::Error> {
    let do_one = |output: &mut W, value: &mut u32| -> Result<(), io::Error> {
        output.write_all(&[((*value & 127) | 128) as u8])?;
        *value >>= 7;
        Ok(())
    };
    let do_last = |output: &mut W, value: u32| -> Result<(), io::Error> {
        output.write_all(&[(value & 127) as u8])?;
        Ok(())
    };

    if value < 1 << 7 {
        //128
        do_last(&mut output, value)?;
        Ok(1)
    } else if value < 1 << 14 {
        do_one(&mut output, &mut value)?;
        do_last(&mut output, value)?;
        Ok(2)
    } else if value < 1 << 21 {
        do_one(&mut output, &mut value)?;
        do_one(&mut output, &mut value)?;
        do_last(&mut output, value)?;
        Ok(3)
    } else if value < 1 << 28 {
        do_one(&mut output, &mut value)?;
        do_one(&mut output, &mut value)?;
        do_one(&mut output, &mut value)?;
        do_last(&mut output, value)?;
        Ok(4)
    } else {
        do_one(&mut output, &mut value)?;
        do_one(&mut output, &mut value)?;
        do_one(&mut output, &mut value)?;
        do_one(&mut output, &mut value)?;
        do_last(&mut output, value)?;
        Ok(5)
    }
}

#[test]
fn test_varint() {
	use crate::iterator::VintArrayIterator;
    let mut sink = vec![];
    encode_varint_into(&mut sink, 5);
    encode_varint_into(&mut sink, 127);
    encode_varint_into(&mut sink, 128);
    encode_varint_into(&mut sink, 50);
    encode_varint_into(&mut sink, 500);
    encode_varint_into(&mut sink, 5000);
    encode_varint_into(&mut sink, 4_000_000_000);
    assert_eq!(sink.len(), 14);

    let mut iter = sink.iter().cloned();
    assert_eq!(decode_varint(&mut iter), Some(5));
    assert_eq!(decode_varint(&mut iter), Some(127));
    assert_eq!(decode_varint(&mut iter), Some(128));
    assert_eq!(decode_varint(&mut iter), Some(50));
    assert_eq!(decode_varint(&mut iter), Some(500));
    assert_eq!(decode_varint(&mut iter), Some(5000));
    assert_eq!(decode_varint(&mut iter), Some(4_000_000_000));

    let iter = VintArrayIterator {
        data: &sink,
        pos: 0,
    };
    let dat: Vec<_> = iter.collect();
    assert_eq!(dat, vec![5, 127, 128, 50, 500, 5000, 4_000_000_000]);

    use std::io::BufReader;
    let mut reader = BufReader::new(&sink[..]);
    assert_eq!(decode_from_reader(reader.get_mut()), Some(5));
    assert_eq!(decode_from_reader(reader.get_mut()), Some(127));
    assert_eq!(decode_from_reader(reader.get_mut()), Some(128));
    assert_eq!(decode_from_reader(reader.get_mut()), Some(50));
    assert_eq!(decode_from_reader(reader.get_mut()), Some(500));
    assert_eq!(decode_from_reader(reader.get_mut()), Some(5000));
    assert_eq!(decode_from_reader(reader.get_mut()), Some(4_000_000_000));
    assert_eq!(decode_from_reader(reader.get_mut()), None);
}

/// Decode a `vint32`-encoded unsigned 32-bit integer from an iterator.
/// Maximum space required are 5 bytes.
///
/// Will panic if incorrectly encoded.
#[inline]
pub fn decode_varint<I: Iterator<Item = u8>>(input: &mut I) -> Option<u32> {
    let mut ret: u32 = 0;
    if let Some(next) = input.next() {
        ret |= u32::from(next) & 127;
        if next & 128 == 0 {
            return Some(ret);
        }
        let next = input.next().unwrap();
        ret |= (u32::from(next) & 127) << 7;
        if next & 128 == 0 {
            return Some(ret);
        }
        let next = input.next().unwrap();
        ret |= (u32::from(next) & 127) << 14;
        if next & 128 == 0 {
            return Some(ret);
        }
        let next = input.next().unwrap();
        ret |= (u32::from(next) & 127) << 21;
        if next & 128 == 0 {
            return Some(ret);
        }
        let next = input.next().unwrap();
        ret |= (u32::from(next) & 127) << 28;
        Some(ret)
    } else {
        None
    }
}

/// Decode a `vint32`-encoded unsigned 32-bit integer from a bytes slice.
/// Maximum space required are 5 bytes.
/// `pos` will be used to access the pos in the slice.
/// `pos` will be incremented by the number of bytes used to dencode the u32.
///
/// Will panic if incorrectly encoded.
#[inline]
pub fn decode_varint_slice(data: &[u8], pos: &mut usize) -> Option<u32> {
    if *pos == data.len() {
        None
    } else {
        let next = data[*pos];
        *pos += 1;
        let mut ret: u32 = u32::from(next) & 127;
        if next & 128 == 0 {
            return Some(ret);
        }
        let next = data[*pos];
        *pos += 1;
        let mut shift_by = 7;
        ret |= (u32::from(next) & 127) << shift_by;
        if next & 128 == 0 {
            return Some(ret);
        }
        let next = data[*pos];
        *pos += 1;
        shift_by += 7;
        ret |= (u32::from(next) & 127) << shift_by;
        if next & 128 == 0 {
            return Some(ret);
        }
        let next = data[*pos];
        *pos += 1;
        shift_by += 7;
        ret |= (u32::from(next) & 127) << shift_by;
        if next & 128 == 0 {
            return Some(ret);
        }
        let next = data[*pos];
        *pos += 1;
        shift_by += 7;
        ret |= (u32::from(next) & 127) << shift_by;
        Some(ret)
    }
}

/// Decode a single `vint32`-encoded unsigned 32-bit integer from a `Read`.
///
/// Will panic if incorrectly encoded or `Read` returns an error.
#[inline]
pub fn decode_from_reader<R: Read>(r: &mut R) -> Option<u32> {
    let mut iter = r.bytes().map(|el| el.unwrap());
    decode_varint(&mut iter)
}

#[test]
fn test_encode_decode_vint_very_large_number() {
	use crate::vint_array::VIntArray;
    let mut vint = VIntArray::default();
    let dat = vec![4_000_000_000];
    vint.encode_vals(&dat);
    let decoded_data: Vec<u32> = vint.iter().collect();
    assert_eq!(&dat, &decoded_data);
}

#[test]
fn test_serialize() {
	use crate::iterator::VintArrayIterator;
	use crate::vint_array::VIntArray;
    let mut vint = VIntArray::default();
    let dat = vec![4_000_000_000];
    vint.encode_vals(&dat);

    let data = vint.serialize();

    let iter = VintArrayIterator::from_serialized_vint_array(&data);
    let decoded_data: Vec<u32> = iter.collect();
    assert_eq!(&dat, &decoded_data);
}

// #[cfg(test)]
// mod tests {
//     use crate::*;
//     #[test]
//     fn it_works() {
//         for i in 0..u32::MAX {
//             let mut vec = vec![];
//             encode_varint_into(&mut vec, i);
//             assert_eq!(decode_varint_slice(&vec, &mut 0).unwrap(), i);
//         }
//     }
// }