#!/usr/bin/env bash
# Fix 1: make kmyCore.dll's scanPlugin use the on-disk filesystem.
#
# kmyPlugin::PluginMgr::scanPlugin calls kmyIO::FS::newFS(0, NULL) which, in
# packaged mode, hands back the in-memory data.rbpack filesystem. The engine's
# .dlp asset loaders (FBXLoader/PNGLoader/OGGLoader/BulletPhysics/...) do NOT
# live inside data.rbpack, so the scan finds none of them and the game loads an
# empty scene (grey screen). This flips the target of that one `call` so it goes
# to the disk-FS creator at RVA 0xAAA10 (which safely handles a NULL path).
#
# The change is a single byte in the rel32 displacement of the call:
#   file offset 0xD0B54 : 0x58 -> 0xB8   (retargets 0xAA9B0 -> 0xAAA10)
# Before writing, the FULL 5-byte call instruction at 0xD0B53 is verified
# (e8 58 92 fd ff), so a different build can't pass on a coincidental byte.
#
# Reversible: a .orig backup is written next to the file the first time.
set -euo pipefail

GAME_ROOT="${1:?usage: 01-kmycore-diskfs.sh <game-root-dir>}"
DLL="$GAME_ROOT/data/kmyCore.dll"
OFF=$((0xD0B54))          # the rel32 low byte we flip
CALL_OFF=$((0xD0B53))     # start of the 5-byte call instruction
ORIG_CALL="e85892fdff"    # call -> disk/pack FS dispatcher RVA 0xAA9B0
NEW_CALL="e8b892fdff"     # call -> disk-FS creator      RVA 0xAAA10
# md5 of the known-good v1.1.0 unpatched kmyCore.dll (5,423,536 bytes)
KNOWN_ORIG_MD5="68590231c9418eeab8b9d70203e1f08d"

[ -f "$DLL" ] || { echo "!! not found: $DLL"; exit 1; }

cur=$(od -An -tx1 -j "$CALL_OFF" -N5 "$DLL" | tr -d ' \n')
if [ "$cur" = "$NEW_CALL" ]; then
  echo "== Fix 1: already applied (call @0x$(printf %x $CALL_OFF) = $NEW_CALL)"; exit 0
fi
if [ "$cur" != "$ORIG_CALL" ]; then
  echo "!! Fix 1: unexpected bytes $cur @0x$(printf %x $CALL_OFF) (expected $ORIG_CALL)."
  echo "!! This kmyCore.dll is a different build than this patch targets. Aborting."
  exit 3
fi

md5now=$(md5sum "$DLL" | cut -d' ' -f1)
[ "$md5now" = "$KNOWN_ORIG_MD5" ] || \
  echo "   (note: kmyCore.dll md5 $md5now != known $KNOWN_ORIG_MD5; byte matches, continuing)"

[ -f "$DLL.orig" ] || cp -n "$DLL" "$DLL.orig"
printf "\xb8" | dd of="$DLL" bs=1 seek="$OFF" count=1 conv=notrunc status=none
echo "== Fix 1: patched kmyCore.dll (disk-FS), backup at kmyCore.dll.orig"