#!/usr/bin/env bash
set -euo pipefail

# Print usage message
usage() {
	cat <<EOF
Usage: $0 <data-file> [<data-file>...]

For each <data-file>:
 1) Look for its AppleDouble at <data-dir>/@eaDir/<basename>@SynoResource
 2) Try to read File Type + Creator from Finder Info (entry ID 9)
 3) If invalid or missing, parse Resource Fork:
    • read mapOffset at RF offset+4
    • go to RF offset + mapOffset + 16 and read 8 bytes
      (first 4 = File Type, next 4 = Creator)
 4) Print: <data-file><TAB><FileTypeASCII><TAB><CreatorASCII>
EOF
	exit 1
}

# Require at least one argument
[ $# -ge 1 ] || usage

for datafile in "$@"; do
	# derive directory and filename
	dirpath=$(dirname -- "$datafile")
	base=$(basename -- "$datafile")
	# path to the AppleDouble companion
	apple="$dirpath/@eaDir/${base}@SynoResource"

	if [ ! -f "$apple" ]; then
		printf 'Error: no AppleDouble for "%s": %s\n' \
		 "$datafile" "$apple" >&2
		continue
	fi

	# read number of entry descriptors (big‑endian uint16 at offset 24)
	num_entries=$(
		printf "%d\n" 0x$(
			xxd -ps -s 24 -l 2 -- "$apple"
		)
	)

	# initialize Finder Info and Resource Fork offsets/lengths
	off9=0; len9=0
	off2=0; len2=0
	entry_table_start=26

	# loop through each 12‑byte descriptor
	for ((i=0; i<num_entries; i++)); do
		b=$((entry_table_start + i*12))
		id=$((0x$(xxd -ps -s "$b" -l 4 -- "$apple")))      # entry ID
		off=$((0x$(xxd -ps -s $((b+4)) -l 4 -- "$apple"))) # entry offset
		ln=$((0x$(xxd -ps -s $((b+8)) -l 4 -- "$apple")))  # entry length
		[ "$id" -eq 9 ] && { off9=$off; len9=$ln; }        # Finder Info
		[ "$id" -eq 2 ] && { off2=$off; len2=$ln; }        # Resource Fork
	done

	filetype_ascii=''
	creator_ascii=''

	# 1) Try Finder Info if at least 8 bytes
	if [ "$len9" -ge 8 ]; then
		# read 8 bytes as hex
		h=$(dd if="$apple" bs=1 skip="$off9" count=8 status=none | xxd -ps)
		ft_hex=${h:0:8}; cr_hex=${h:8:8}
		# convert hex → ASCII, strip nulls, suppress warnings
		filetype_ascii=$(
			echo -n "$ft_hex" \
			| xxd -r -p 2>/dev/null \
			| tr -d '\000'
		)
		creator_ascii=$(
			echo -n "$cr_hex" \
			| xxd -r -p 2>/dev/null \
			| tr -d '\000'
		)
		# validate exactly 4 alphanumeric chars
		if ! [[ $filetype_ascii =~ ^[A-Za-z0-9]{4}$ ]]; then filetype_ascii=''; fi
		if ! [[ $creator_ascii  =~ ^[A-Za-z0-9]{4}$ ]]; then creator_ascii='';  fi
	fi

	# 2) Fallback: parse Resource Fork’s Resource Map
	if [ -z "$filetype_ascii" ] && [ "$len2" -ge 16 ]; then
		# read mapOffset (big‑endian uint32 at off2+4)
		map_hex=$(dd if="$apple" bs=1 skip=$((off2+4)) count=4 status=none | xxd -ps)
		map_off=$((0x$map_hex))
		# compute where the embedded Finder Info lives
		attr_off=$((off2 + map_off + 16))
		# read 8 bytes from that location
		h2=$(dd if="$apple" bs=1 skip="$attr_off" count=8 status=none | xxd -ps)
		ft_hex=${h2:0:8}; cr_hex=${h2:8:8}
		# convert hex → ASCII, strip nulls
		filetype_ascii=$(
			echo -n "$ft_hex" \
			| xxd -r -p 2>/dev/null \
			| tr -d '\000'
		)
		creator_ascii=$(
			echo -n "$cr_hex" \
			| xxd -r -p 2>/dev/null \
			| tr -d '\000'
		)
		# validate exactly 4 alphanumeric chars
		if ! [[ $filetype_ascii =~ ^[A-Za-z0-9]{4}$ ]]; then filetype_ascii=''; fi
		if ! [[ $creator_ascii  =~ ^[A-Za-z0-9]{4}$ ]]; then creator_ascii='';  fi
	fi

	# only print if both FileType and Creator are non‐empty
	if [[ -n "$filetype_ascii" && -n "$creator_ascii" ]]; then
		printf '%s\t%s\t%s\n' "$datafile" "$filetype_ascii" "$creator_ascii"
	fi
done