use crate::{read::ReadExt, write::write_vint};
use anyhow::Result;
use std::io::Cursor;

pub enum LacingType {
    FixedSize,
    Ebml,
    Xiph,
}

pub struct Block {
    pub track: u64,
    pub timestamp_off: i16,
    pub invisible: bool,
    pub lacing: Option<LacingType>,
    pub data: Vec<u8>,
}

impl Block {
    pub fn parse(buf: &[u8]) -> Result<Self> {
        let (track, c) = Cursor::new(buf).read_vint_len()?;
        let timestamp_off = i16::from_be_bytes(buf[c..c + 2].try_into().unwrap());
        let flags = buf[c + 2];
        let data = Vec::from(&buf[c + 3..]);

        let invisible = (flags & 0b10000) == 0b10000;
        let lacing = match flags & 0b1100 {
            0b0000 => None,
            0b0100 => Some(LacingType::Xiph),
            0b1000 => Some(LacingType::Ebml),
            0b1100 => Some(LacingType::FixedSize),
            _ => unreachable!(),
        };

        Ok(Self {
            track,
            data,
            invisible,
            lacing,
            timestamp_off,
        })
    }
    pub fn dump(&self) -> Vec<u8> {
        let mut out = vec![];
        write_vint(&mut out, self.track).unwrap();
        out.extend(self.timestamp_off.to_be_bytes().into_iter());
        out.push(
            match self.invisible {
                true => 0b10000,
                false => 0b00000,
            } | match self.lacing {
                Some(LacingType::Xiph) => 0b0100,
                Some(LacingType::Ebml) => 0b1000,
                Some(LacingType::FixedSize) => 0b1100,
                None => 0b0000,
            },
        );
        out
    }
}