//! Versioned read-only superblock parser guest probe.

use super::*;
use os_vfs_superblock::{Error, Superblock, checksum, decode, encode_v1};

fn reseal(bytes: &mut [u8; os_vfs_superblock::SUPERBLOCK_BYTES]) {
    let digest = checksum(bytes);
    bytes[60..64].copy_from_slice(&digest.to_le_bytes());
}

pub fn run(allocator: &mut memory::FrameAllocator) -> Result<(), &'static str> {
    let frames_before = allocator.remaining_pages();
    let valid = encode_v1(2048, 7).map_err(|_| "k1605-encode")?;
    if decode(&valid, 4096) != Ok(Superblock {version: 1,
        total_blocks: 2048, root_inode: 1, generation: 7}) {
        return Err("k1605-v1");
    }
    write_line("TURKOS/OS/K1605-SB: V1=2048 GEN=7");

    let mut newer = valid;
    newer[4..6].copy_from_slice(&2u16.to_le_bytes());
    reseal(&mut newer);
    if decode(&newer, 4096) != Err(Error::UnsupportedVersion) {
        return Err("k1605-version");
    }
    write_line("TURKOS/OS/K1605-SB: VERSION2=REJECTED");

    let mut features = valid;
    features[6..8].copy_from_slice(&1u16.to_le_bytes());
    reseal(&mut features);
    if decode(&features, 4096) != Err(Error::UnsupportedFeatures) {
        return Err("k1605-features");
    }
    write_line("TURKOS/OS/K1605-SB: FEATURES=REJECTED");

    if decode(&valid, 2047) != Err(Error::BadGeometry) {
        return Err("k1605-geometry");
    }
    write_line("TURKOS/OS/K1605-SB: GEOMETRY=REJECTED");

    let mut corrupt = valid;
    corrupt[60] ^= 1;
    let mut reserved = valid;
    reserved[40] = 1;
    reseal(&mut reserved);
    if decode(&corrupt, 4096) != Err(Error::BadChecksum)
        || decode(&reserved, 4096) != Err(Error::BadReserved)
        || allocator.remaining_pages() != frames_before {
        return Err("k1605-corrupt");
    }
    write_line("TURKOS/OS/K1605-SB: CORRUPTION=REJECTED FRAMES=UNCHANGED");
    Ok(())
}