//! Physical final-sector read with adjacent-sector isolation.

use super::*;
use os_partitions_view::{Error as ViewError, ReadError, View};

pub fn run(boot: &BootData,
    allocator: &mut memory::FrameAllocator) -> Result<(), &'static str> {
    let before = allocator.remaining_pages();
    let mut disk = virtio_ro_turkfs::RoDisk::open(
        boot, allocator, "TURKOS/OS/K1535-GET")?;
    if disk.capacity() != 2048 { return Err("k1535-disk-capacity"); }
    let mut mbr = [0u8; 512];
    disk.read(0, &mut mbr)?;
    let table = os_partitions::parse(&mbr, 2048)
        .map_err(|_| "k1535-MBR-table")?;
    let first = table.entry(0).ok_or("k1535-first-partition")?;
    let second = table.entry(2).ok_or("k1535-second-partition")?;
    if first.start_lba != 1 || first.sectors != 100 || first.end_lba != 101
        || second.start_lba != 101 || second.end_lba != 2048 {
        return Err("k1535-partition-layout");
    }
    let view = View::new(first.start_lba, first.sectors, table.disk_sectors)
        .map_err(|_| "k1535-view-construction")?;
    let baseline = view;
    let mut neighbor_before = [0u8; 512];
    let mut final_sector = [0u8; 512];
    let mut neighbor_after = [0u8; 512];
    disk.read(101, &mut neighbor_before)?;
    let mut translated_lba = 0;
    view.read(99, 1, |lba, count| {
        if count != 1 { return Err("k1535-read-span"); }
        translated_lba = lba;
        disk.read(lba, &mut final_sector)
    }).map_err(|_| "k1535-final-sector-read")?;
    let mut forbidden_calls = 0;
    let refusal = view.read(100, 1, |_lba, _count| {
        forbidden_calls += 1;
        Ok::<(), &'static str>(())
    });
    if refusal != Err(ReadError::View(ViewError::OutsidePartition))
        || forbidden_calls != 0 || view != baseline {
        return Err("k1535-outside-request-submitted");
    }
    disk.read(101, &mut neighbor_after)?;
    disk.close(allocator)?;
    if translated_lba != 100 || final_sector.iter().any(|&byte| byte != 0x5a)
        || neighbor_before.iter().any(|&byte| byte != 0xa6)
        || neighbor_after != neighbor_before
        || allocator.remaining_pages() != before {
        return Err("k1535-neighbor-or-DMA-changed");
    }
    write_line("TURKOS/OS/K1535-VIEW: PHYSICAL=READ LAST=99:100 OUTSIDE=REJECTED NEIGHBOR=UNCHANGED IO=4 FRAMES=RETURNED");
    Ok(())
}