#!/usr/bin/env bash
# scripts/igir-strip-snes-headers.sh   (runs ON valhalla)
#
# SNES copier ROMs carry a 512-byte header (file size % 1024 == 512). igir
# detects SNES headers by content *signature*, which these copier headers lack,
# so it can't strip them and they never match headerless No-Intro DATs — even
# though their headerless checksum IS in No-Intro. This script blind-strips that
# 512-byte header (the universally-correct fix for SNES) and renames to .sfc.
#
# It is a MUTATION of the live EmuDeck tree (RomM + EmuDeck read it). Every
# touched file is tar'd to a backup first, so the change is fully reversible.
#
# Usage (default folder = snes):
#   ssh ginnoir@valhalla 'bash -s'            < scripts/igir-strip-snes-headers.sh
#   ssh ginnoir@valhalla 'bash -s -- sfc'     < scripts/igir-strip-snes-headers.sh
#   ssh ginnoir@valhalla 'bash -s -- snes 1'  < scripts/igir-strip-snes-headers.sh   # 2nd arg=1 => dry run
#
# Restore from a backup:
#   tar xzf /storage1/igir/backup/<folder>-headered-<stamp>.tar.gz \
#       -C /storage1/Emulation/roms/<folder>
set -uo pipefail

FOLDER="${1:-snes}"
DRYRUN="${2:-0}"
ROOT="/storage1/Emulation/roms/$FOLDER"
BK="/storage1/igir/backup"
STAMP="$(date +%Y-%m-%d)"

[ -d "$ROOT" ] || { echo "No such folder: $ROOT"; exit 1; }
mkdir -p "$BK"
cd "$ROOT" || exit 1
shopt -s nullglob nocaseglob

# Collect headered SNES ROMs (size % 1024 == 512).
list="$(mktemp)"; : > "$list"
for f in *.smc *.sfc *.fig *.swc; do
  [ -f "$f" ] || continue
  s=$(stat -c %s "$f")
  [ $((s % 1024)) -eq 512 ] && printf '%s\0' "$f" >> "$list"
done
n=$(grep -zc . "$list" || true)
echo "Headered files in '$FOLDER': $n"
if [ "$n" -eq 0 ]; then echo "Nothing to strip."; rm -f "$list"; exit 0; fi

if [ "$DRYRUN" = "1" ]; then
  echo "(dry run) would back up to $BK/$FOLDER-headered-$STAMP.tar.gz and strip $n files."
  rm -f "$list"; exit 0
fi

# Back up originals before mutating.
bkfile="$BK/$FOLDER-headered-$STAMP.tar.gz"
tar --null -czf "$bkfile" -T "$list"
echo "Backup: $bkfile ($(stat -c %s "$bkfile") bytes, $(tar tzf "$bkfile" | wc -l) files)"

# Strip: drop first 512 bytes, verify new size, write as .sfc, remove old.
stripped=0; errors=0
while IFS= read -r -d '' f; do
  s=$(stat -c %s "$f")
  base="${f%.*}"; target="$base.sfc"; tmp="$f.hl.tmp"
  tail -c +513 "$f" > "$tmp"
  ns=$(stat -c %s "$tmp")
  if [ "$ns" -ne $((s - 512)) ]; then
    echo "SIZE MISMATCH, skipped: $f ($s -> $ns)"; rm -f "$tmp"; errors=$((errors+1)); continue
  fi
  if [ "$target" != "$f" ] && [ -e "$target" ]; then target="$base (headerless).sfc"; fi
  mv -f "$tmp" "$target"
  [ "$target" != "$f" ] && rm -f "$f"
  stripped=$((stripped+1))
done < "$list"
rm -f "$list"

# Verify none remain.
left=0
for f in *.smc *.sfc *.fig *.swc; do
  [ -f "$f" ] || continue
  s=$(stat -c %s "$f")
  [ $((s % 1024)) -eq 512 ] && left=$((left+1))
done
echo "RESULT stripped=$stripped errors=$errors remaining_headered=$left"