#!/bin/bash
# Executes a UTS #35 rule file (e.g. collatz.txt) with ICU's stock command-line tool.
# ./uts35.sh collatz.txt aaaaaaa      # Collatz of 7, ends at Ma

[ $# -eq 2 ] || { echo "usage: $0 RULES.txt dataword" >&2; exit 1; }
RULES=$(cat "$1") || exit 1
UCONV=$(command -v uconv || echo /opt/homebrew/opt/icu4c/bin/uconv)  # Homebrew's icu4c is keg-only
[ -x "$UCONV" ] || { echo "uconv not found — apt install icu-devtools, or brew install icu4c" >&2; exit 1; }

s="M$2"
pass=0
printf '%3s - %s\n' 0 "$s"
while true; do
  t=$(printf '%s' "$s" | "$UCONV" -f utf-8 -t utf-8 -x "$RULES")
  [ "$t" = "$s" ] && break
  s="$t"
  pass=$((pass + 1))
  printf '%3s - %s\n' "$pass" "$s"
done