#!/usr/bin/env bash

# exit if required variables are not set
set -o nounset

# subshells and functions inherit ERR traps
set -E

# pass debug value to child scripts
DEBUG="${DEBUG:-0}"
export DEBUG

# number of threads to use
if [[ ${DEBUG} -eq 1 ]]; then
  echo "Running single thread for debugging"
  parallel_thread_count=1
else
  parallel_thread_count=8
fi

# exit if lock file exists, otherwise create it
lock_file="/run/user/$(id -ru)/optimize-pngs.lock"

if [ -f "${lock_file}" ]; then
  echo "Process already running at pid $(cat "${lock_file}")."
  exit 0
fi

echo "$$" > "${lock_file}"

# remove lock file on exit
function cleanup {
  if ! { rm "${lock_file}"; }; then
    echo "Cleanup failed. You may need to manually remove ${lock_file}."
  fi
}
trap cleanup EXIT

# create and display temporary directory
base_dir="$(mktemp -d)"
if [[ ${DEBUG} -eq 1 ]]; then
  echo "Temporary files will be written to ${base_dir}."
fi

# command list location
commands="${base_dir}/commands.txt"
if [[ ${DEBUG} -eq 1 ]]; then
  echo "Storing commands for $(pwd) in ${commands}"
fi

# generate list of commands to run
while read -r path; do
  echo "cd \"${path}\"; optimize-pngs.sh ${base_dir}; cd .." >> "${commands}"
done <<< "$(find "$(pwd -P)" -maxdepth 1 -type d)"

# run list of commands in parallel
parallel --no-notice --jobs "${parallel_thread_count}" < "${commands}"

# prompt to remove temporary directory
SHELLNOCASEMATCH=$(shopt -p nocasematch; true)
shopt -s nocasematch
read -r -p 'Delete temporary directory? [y/N]: ' remove_temp_dir
if [[ "${remove_temp_dir}" == "y" ]]; then
  rm -rf "${base_dir}"
fi
$SHELLNOCASEMATCH