// Trivial tar loader.

use core::mem::transmute;
use matcha_hal::dprintf;

const EFLASH_START: u32 = 0x44000000;
const EFLASH_END: u32 = 0x45000000;

#[repr(C, packed)]
pub struct TarHeader {
    /* byte offset */
    name: [u8; 100],     /*   0 */
    mode: [u8; 8],       /* 100 */
    uid: [u8; 8],        /* 108 */
    gid: [u8; 8],        /* 116 */
    size: [u8; 12],      /* 124 */
    mtime: [u8; 12],     /* 136 */
    chksum: [u8; 8],     /* 148 */
    typeflag: u8,        /* 156 */
    linkname: [u8; 100], /* 157 */
    magic: [u8; 6],      /* 257 */
    version: [u8; 2],    /* 263 */
    uname: [u8; 32],     /* 265 */
    gname: [u8; 32],     /* 297 */
    devmajor: [u8; 8],   /* 329 */
    devminor: [u8; 8],   /* 337 */
    prefix: [u8; 155],   /* 345 */
                         /* 500 */
}

impl Default for TarHeader {
    fn default() -> Self {
        return TarHeader {
            name: [0; 100],
            mode: [0; 8],
            uid: [0; 8],
            gid: [0; 8],
            size: [0; 12],
            mtime: [0; 12],
            chksum: [0; 8],
            typeflag: 0,
            linkname: [0; 100],
            magic: [0; 6],
            version: [0; 2],
            uname: [0; 32],
            gname: [0; 32],
            devmajor: [0; 8],
            devminor: [0; 8],
            prefix: [0; 155],
        };
    }
}

fn parse_octal(text: &[u8]) -> u32 {
    let mut n: u32 = 0;
    for x in text.iter() {
        if *x == (0 as u8) {
            break;
        }
        n = (n << 3) | ((*x as u32) - ('0' as u32));
    }
    return n;
}

pub unsafe fn find_file(name: &str) -> (u32, u32) {
    let mut cursor = EFLASH_START;
    while cursor < EFLASH_END {
        let tar_header: *const TarHeader = transmute(cursor);
        cursor += 512;
        let tar_name = core::str::from_utf8(&(*tar_header).name).unwrap();
        if tar_name.contains(name) {
            let tar_size = parse_octal(&(*tar_header).size);
            return (cursor, tar_size);
        } else {
            let tar_size = parse_octal(&(*tar_header).size);
            cursor += (tar_size + 511) & !511;
        }
    }

    dprintf!("Could not find tar entry for '{}'\n", name);
    return (0, 0);
}