//! Serialized in-memory truncation and live-reader backing protection.
use super::*;
use os_turkfs_allocation::{Bitmap, Error, TruncateFile};

pub fn run(allocator: &mut memory::FrameAllocator) -> Result<(), &'static str> {
    let frames_before = allocator.remaining_pages();
    let mut bitmap = Bitmap::validate(64, 3, 3 | (1 << 10) | (1 << 20) | (1 << 30))
        .map_err(|_| "k1640-bitmap")?;
    let mut bytes = [0x5a; 1536];
    bytes[512..1024].fill(0x6b);
    bytes[1024..].fill(0x7c);
    let file = TruncateFile::new([10, 20, 30], 1025, bytes, &bitmap)
        .map_err(|_| "k1640-file")?;
    let first = file.reader().map_err(|_| "k1640-first-reader")?;
    let second = file.reader().map_err(|_| "k1640-second-reader")?;
    let before = bitmap;
    if file.truncate(100, &mut bitmap) != Err(Error::Busy)
        || bitmap != before || file.length() != 1025 || file.block_count() != 3
        || file.active_readers() != 2 || first.byte(1024) != Some(0x7c) {
        return Err("k1640-reader-busy");
    }
    write_line("TURKOS/OS/K1640-TRUNCATE: READERS=2 BUSY=UNCHANGED");
    drop(first);
    if file.truncate(100, &mut bitmap) != Err(Error::Busy)
        || bitmap != before || file.length() != 1025
        || second.byte(1024) != Some(0x7c) {
        return Err("k1640-last-reader-busy");
    }
    drop(second);
    if file.active_readers() != 0 { return Err("k1640-reader-close"); }
    write_line("TURKOS/OS/K1640-TRUNCATE: LAST-READER=CLOSED");
    file.truncate(100, &mut bitmap).map_err(|_| "k1640-truncate")?;
    if file.length() != 100 || file.block_count() != 1
        || bitmap.allocated_bits() != 3 | (1 << 10)
        || bitmap.counts().free != before.counts().free + 2 {
        return Err("k1640-retirement");
    }
    write_line("TURKOS/OS/K1640-TRUNCATE: SIZE=100 BLOCKS=1 FREED=2");
    let reader = file.reader().map_err(|_| "k1640-short-reader")?;
    if reader.byte(99) != Some(0x5a) || reader.byte(100) != None
        || reader.byte(1024) != None || reader.byte(usize::MAX) != None
        || allocator.remaining_pages() != frames_before {
        return Err("k1640-byte-boundary");
    }
    write_line("TURKOS/OS/K1640-TRUNCATE: BYTE99=5A BYTE100=EOF FRAMES=UNCHANGED");
    Ok(())
}