//! Physical paired-GPT reads, bounded streaming validation, and mount refusal.

use super::*;
use os_partitions_gpt::{Error as PartitionError, MountState, StreamError};

pub fn run(boot: &BootData,
    allocator: &mut memory::FrameAllocator) -> Result<(), &'static str> {
    let before = allocator.remaining_pages();
    let mut primary = [0u8; 512];
    let mut backup = [0u8; 512];
    let mut disk = virtio_ro_turkfs::RoDisk::open(
        boot, allocator, "TURKOS/OS/K1530-GET")?;
    if disk.capacity() != 2048 { return Err("k1530-disk-capacity"); }
    disk.read(1, &mut primary)?;
    disk.read(2047, &mut backup)?;
    disk.close(allocator)?;
    if allocator.remaining_pages() != before {
        return Err("k1530-header-DMA-leak");
    }
    let layout = os_partitions_gpt::inspect_headers(&primary, &backup, 2048)
        .map_err(|_| "k1530-valid-GPT-headers")?;
    if layout.primary_array_lba != 2 || layout.backup_array_lba != 2015
        || layout.first_usable != 34 || layout.last_usable != 2014 {
        return Err("k1530-GPT-layout");
    }
    let mut mounts = MountState::new();
    let mut active: Option<virtio_ro_turkfs::RoDisk> = None;
    let mut batch = 0usize;
    let mut reads = 0usize;
    let result = mounts.mount_stream(&primary, &backup, 2048, |lba, destination| {
        if batch == 4 {
            active.take().ok_or("k1530-reader-missing")?.close(allocator)?;
            batch = 0;
        }
        if active.is_none() {
            active = Some(virtio_ro_turkfs::RoDisk::open(
                boot, allocator, "TURKOS/OS/K1530-GET")?);
        }
        active.as_mut().ok_or("k1530-reader-open")?.read(lba, destination)?;
        batch += 1;
        reads += 1;
        Ok::<(), &'static str>(())
    });
    if let Some(disk) = active.take() { disk.close(allocator)?; }
    let table = result.map_err(|_| "k1530-valid-GPT-arrays")?;
    if reads != 64 || table.count != 2
        || table.entries[0].map(|p| (p.first_lba, p.last_lba)) != Some((34, 100))
        || table.entries[1].map(|p| (p.first_lba, p.last_lba)) != Some((101, 2014)) {
        return Err("k1530-GPT-partitions");
    }
    if allocator.remaining_pages() != before {
        return Err("k1530-array-DMA-leak");
    }
    let healthy = mounts;
    let mut corrupt_crc = primary;
    corrupt_crc[56] ^= 1;
    let mut forbidden_reads = 0usize;
    let refused = mounts.mount_stream(&corrupt_crc, &backup, 2048,
        |_lba, _sector| { forbidden_reads += 1; Ok::<(), ()>(()) });
    if refused != Err(StreamError::Parse(PartitionError::BadHeaderCrc))
        || forbidden_reads != 0 || mounts != healthy {
        return Err("k1530-bad-CRC-mounted");
    }
    let mut oversized = primary;
    oversized[80..84].copy_from_slice(&4096u32.to_le_bytes());
    oversized[16..20].fill(0);
    let crc = os_partitions_gpt::crc32(&oversized[..92]);
    oversized[16..20].copy_from_slice(&crc.to_le_bytes());
    let refused = mounts.mount_stream(&oversized, &backup, 2048,
        |_lba, _sector| { forbidden_reads += 1; Ok::<(), ()>(()) });
    if refused != Err(StreamError::Parse(PartitionError::UnsupportedLayout))
        || forbidden_reads != 0 || mounts != healthy {
        return Err("k1530-oversized-mounted");
    }
    let mut empty = MountState::new();
    let refused = empty.mount_stream(&corrupt_crc, &backup, 2048,
        |_lba, _sector| { forbidden_reads += 1; Ok::<(), ()>(()) });
    if refused != Err(StreamError::Parse(PartitionError::BadHeaderCrc))
        || forbidden_reads != 0 || empty.table.is_some() || empty.generation != 0 {
        return Err("k1530-corrupt-disk-mounted");
    }
    write_line("TURKOS/OS/K1530-GPT: PHYSICAL=READ HEADERS=2 ARRAYS=64 ENTRIES=2 FIRST=34:100 SECOND=101:2014 CRC=REJECTED OVERSIZED=REJECTED MOUNT=UNCHANGED FRAMES=RETURNED");
    Ok(())
}