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use crate::field::codec::{ByteCodecBE, ByteCodecLE, Codec};

pub struct BitCodecLE {

    bit_size: usize,

    bit_offset: usize,

}

impl BitCodecLE {

    pub fn new(bit_offset: usize, bit_size: usize) -> Self {

        Self {

            bit_size,

            bit_offset

        }

    }

}

impl Codec for BitCodecLE {

    fn read(&self, buffer: &[u8]) -> u64 {

        let value = ByteCodecLE.read(buffer);

        let mask = (1 << self.bit_size) - 1;

        (value >> self.bit_offset) & mask

    }

    fn write(&self, buffer: &mut [u8], value: u64) {

        let mask = (1 << self.bit_size) - 1;

        let reset_mask = !(mask << self.bit_offset);

        let original = ByteCodecLE.read(buffer);

        let clean = original & reset_mask;

        let value = (value & mask) << self.bit_offset;

        let new = clean | value;

        ByteCodecLE.write(buffer, new);

    }

}

pub struct BitCodecBE {

    bit_size: usize,

    bit_offset: usize,

}

impl BitCodecBE {

    pub fn new(bit_offset: usize, bit_size: usize) -> Self {

        Self {

            bit_size,

            bit_offset

        }

    }

}

impl Codec for BitCodecBE {

    fn read(&self, buffer: &[u8]) -> u64 {

        let mask = (1 << self.bit_size) - 1;

        let value = ByteCodecBE.read(buffer);

        (value >> (8 - (self.bit_size % 8) - self.bit_offset)) & mask

    }

    fn write(&self, buffer: &mut [u8], value: u64) {

        let mask = (1 << self.bit_size) - 1;

        let reset_mask = !(mask << (8 - (self.bit_size % 8) - self.bit_offset));

        let original = ByteCodecBE.read(buffer);

        let clean = original & reset_mask;

        let value = (value & mask) << (8 - (self.bit_size % 8) - self.bit_offset);

        let new = clean | value;

        ByteCodecBE.write(buffer, new);

    }

}

#[cfg(test)]

mod tests {

    use crate::field::codec::bits::{BitCodecBE, BitCodecLE};

    use crate::field::codec::Codec;

    #[test]

    fn little_endian() {

        let buffer = [0xFF, 0xFF, 0xFF, 0xFF];

        assert_eq!(BitCodecLE::new(0, 32).read(&buffer[0..4]), 0xFFFFFFFF);

        assert_eq!(BitCodecLE::new(0, 1).read(&buffer[0..1]), 1);

        assert_eq!(BitCodecLE::new(0, 4).read(&buffer[0..1]), 0xF);

        assert_eq!(BitCodecLE::new(4, 4).read(&buffer[0..1]), 0xF);

    }

    #[test]

    fn big_endian() {

        let buffer = [0xAB, 0xF0];

        assert_eq!(BitCodecBE::new(0, 12).read(&buffer[0..2]), 0xABF);

        let mut buffer = [0x0, 0x0];

        BitCodecBE::new(0, 4).write(&mut buffer[0..1], 0xF);

        assert_eq!(BitCodecBE::new(0, 4).read(&buffer[0..1]), 0xF);

        BitCodecBE::new(0, 12).write(&mut buffer[0..2], 0xABF);

        assert_eq!(BitCodecBE::new(0, 12).read(&buffer[0..2]), 0xABF);

        BitCodecBE::new(1, 7).write(&mut buffer[1..2], 127);

        assert_eq!(BitCodecBE::new(1, 7).read(&buffer[1..2]), 127);

    }

}