protolens 0.2.1

use crate::packet::*;
use memchr::memchr;

pub(crate) struct PktData<T>
where
    T: Packet,
{
    pkt: T,
    read_offset: usize,
}

impl<T> PktData<T>
where
    T: Packet,
{
    pub(crate) fn new(pkt: T) -> Self {
        PktData {
            pkt,
            read_offset: 0,
        }
    }

    pub(crate) fn readline(&mut self) -> Result<(&[u8], usize), ()> {
        let payload = self.pkt.payload();
        if self.read_offset >= payload.len() {
            return Err(());
        }

        let offset = self.read_offset;
        let remaining = &payload[self.read_offset..];

        if let Some(pos) = memchr(b'\n', remaining) {
            let line = &remaining[..pos + 1];
            self.read_offset += pos + 1;
            return Ok((line, offset));
        }
        Err(())
    }

    pub(crate) fn readline_str(&mut self) -> Result<(&str, usize), ()> {
        let (bytes, offset) = self.readline()?;
        unsafe { Ok((std::str::from_utf8_unchecked(bytes), offset)) }
    }

    pub(crate) fn readn(&mut self, size: usize) -> Result<(&[u8], usize), ()> {
        let payload = self.pkt.payload();
        if self.read_offset >= payload.len() {
            return Err(());
        }

        let remaining = payload.len() - self.read_offset;
        if size > remaining {
            return Err(());
        }

        let offset = self.read_offset;
        let data = &payload[self.read_offset..self.read_offset + size];
        self.read_offset += size;

        Ok((data, offset))
    }

    pub(crate) fn remain_data(&self) -> bool {
        let payload = self.pkt.payload();
        self.read_offset < payload.len()
    }
}