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use super::*;
use byteorder::{ByteOrder, LittleEndian};

pub trait FragmentSequenceTrait: FrameTrait {
    const FRAGMENT_SEQUENCE_START: usize = 22;
    const FRAGMENT_SEQUENCE_END: usize = Self::FRAGMENT_SEQUENCE_START + 2;

    /// Fragment Number
    fn fragment_number(&self) -> u8 {
        (self.bytes()[Self::FRAGMENT_SEQUENCE_START] & 0b0000_1111) as u8
    }

    /// Sequence Number
    fn sequence_number(&self) -> u16 {
        LittleEndian::read_u16(
            &self.bytes()[Self::FRAGMENT_SEQUENCE_START..(Self::FRAGMENT_SEQUENCE_START + 2)],
        ) >> 4
    }
}

pub trait FragmentSequenceBuilderTrait: FrameBuilderTrait {
    const FRAGMENT_SEQUENCE_START: usize = 22;
    const FRAGMENT_SEQUENCE_END: usize = Self::FRAGMENT_SEQUENCE_START + 2;

    /// Fragment Number
    fn fragment_number(&mut self, fragment_number: u8) {
        self.bytes_mut()[Self::FRAGMENT_SEQUENCE_START] =
            (self.bytes()[Self::FRAGMENT_SEQUENCE_START] & !0b0000_1111)
                | (0b0000_1111 & fragment_number);
    }

    /// Sequence Number
    fn sequence_number(&mut self, sequence_number: u16) {
        let old = LittleEndian::read_u16(
            &self.bytes()[Self::FRAGMENT_SEQUENCE_START..(Self::FRAGMENT_SEQUENCE_START + 2)],
        ) & !0b1111_1111_1111_0000;

        LittleEndian::write_u16(
            &mut self.bytes_mut()
                [Self::FRAGMENT_SEQUENCE_START..(Self::FRAGMENT_SEQUENCE_START + 2)],
            old | (sequence_number << 4),
        );
    }
}