#!/bin/bash
# Build the SCSI VOLUME the P4 rigs read, and the blank card ROM MAME needs to
# instantiate the card.  Sourced-by-calling from tools/bench/scsi_run.sh and
# tools/bench/pace_run.sh so there is ONE copy of the layout.
#
#   tools/bench/mkvol.sh [container.dlx | container.dlxp]
#
# TWO CONTAINERS, ONE VOLUME BUILDER.  A DLX volume is tools/bench/prep_stream.py's
# disk image -- the codec's records, laid down from sector 0.  A DLXP volume
# (ROADMAP K2/K3) needs no preparation at all: the container is ALREADY a
# sector-aligned image of itself -- a 512 B header, then fixed 97-sector records
# -- so the file IS the volume and copying it is the whole build.  That is not a
# convenience, it is the format's central claim (tools/encoder/dlxp.py) arriving
# at the disc, and a builder that transformed it on the way would be hiding the
# claim rather than testing it.
#
# The two get DIFFERENT CHD NAMES.  Alternating between the packed rig and the
# codec rig would otherwise rebuild the volume on every run, and -- much worse --
# a stale CHD under the name the other rig expected would serve one container's
# bytes to the other's gate, which reads as a decode failure and is not one.
#
# ONE COPY, ON PURPOSE.  The volume is tmp/stream_disk.bin -- byte for byte the
# file the host-file ring rig reads -- laid out as 512 B sectors.  If two scripts
# each built it, a difference between the SCSI rig and the modelled-transport rig
# could be a difference in what they were reading, and the whole value of running
# both is that it cannot be.  This tree has already paid twice for a transform
# with two copies of itself (FINDINGS 49.7.5, and check.sh's dlxload note).
#
# THE BLANK BOOT ROM is the substitution session 25 argued for and it is
# unchanged: MAME refuses to instantiate the CZ-6BS1 without an 8 KB
# `scsiexrom.bin` (CRC 7be488de) that the player never executes, so a zero-filled
# placeholder goes on a SEPARATE rompath and the user's romset is untouched.
# MAME prints WRONG CHECKSUMS, as it should.  DO NOT reuse this rompath for
# anything that boots from the card or calls SCSI IOCS -- those DO execute it.
set -e
cd "$(dirname "$0")/../.."
DLX=${1:-tmp/rc_fr_singe_scsi_span.dlx}

case "$DLX" in
  *.dlxp) SRC="$DLX"
          IMG=tmp/dlxpdisk.img; CHD=tmp/dlxpdisk.chd ;;
  *)      SRC=tmp/stream_disk.bin
          IMG=tmp/dlxdisk.img;  CHD=tmp/dlxdisk.chd
          [ -f "$SRC" ] || python3 tools/bench/prep_stream.py "$DLX" > /dev/null ;;
esac

if [ ! -f "$CHD" ] || [ "$SRC" -nt "$CHD" ]; then
  SRC="$SRC" IMG="$IMG" python3 - <<'PY'
import os
src, img = os.environ["SRC"], os.environ["IMG"]
d = open(src, "rb").read()
n = (len(d) + 511) // 512
open(img, "wb").write(d + b"\0" * (n * 512 - len(d)))
print(f"  disc image: {len(d)} B of records -> {n} sectors")
PY
  rm -f "$CHD"
  # -c none IS LOAD-BEARING, and it was found by a gate rather than by taste.
  # Session 28, on the DLX5 volume: with the default (lzma/zlib/huff/flac) MAME
  # 0.277 served the CHD FILE'S OWN BYTES as sector data -- the destination
  # buffer after READ(10) at LBA 0 was byte-for-byte the first 4,096 bytes of
  # dlxdisk.chd, starting "MComprHD" -- while `chdman verify` reported both SHA1s
  # correct.  Uncompressed, the identical image reads byte-exact.  The trigger is
  # the image's CONTENT: the same 8,768-sector length that works for the DLX4
  # volume fails for the DLX5 one, a conventional 16x63 geometry fails too, and
  # `-c zlib` alone fails as well.  The MAME-side cause is NOT diagnosed; what is
  # measured is that compression decides it and uncompressed is sound.
  # Costs 4.5 MB in tmp/ against 1.6 MB.  DO NOT restore compression to save the
  # disc space: the failure is SILENT at the transport layer -- every READ(10)
  # reports success and returns the wrong bytes -- and only the byte comparison
  # in tools/bench/scsi.lua catches it.
  chdman createhd -i "$IMG" -o "$CHD" -ss 512 -c none > /dev/null 2>&1
fi

mkdir -p tmp/p4roms/x68k_cz6bs1
[ -f tmp/p4roms/x68k_cz6bs1/scsiexrom.bin ] || \
  head -c 8192 /dev/zero > tmp/p4roms/x68k_cz6bs1/scsiexrom.bin