#!/usr/bin/env bash

set -euo pipefail

readonly SCAN_PATH="${1:-.}"

case "${1:-}" in
	'-h' | '--help' | 'help')
		cat << 'EOF'
 precompress
 ===========

 Usage
 -----

 precompress [path]

 If path is omitted, it used the current working directory.

 Primarily used for Caddy's file_sever directive's precompresed option.
 It will compress every non brotli, zstandard, or gzip file.
EOF
		exit 0
		;;
esac

if [ "${SCAN_PATH}" = "." ] && [ -t 0 ] && [ -t 1 ] && [ -t 2 ]; then
	while read -r -p "About to compress all of ${PWD}, continue? [y/n] " ANSWER; do
		case "${ANSWER}" in
			'y')
				break
				;;

			'n')
				exit 1
				;;
		esac
	done
fi

readonly REQUIRED_APPS=(
	'ag'
	'brotli'
	'cat'
	'nproc'
	'pigz'
	'sha256sum'
	'tr'
	'xargs'
	'zstd'
)

for REQUIRED_APP in "${REQUIRED_APPS[@]}"; do
	if ! command -v "${REQUIRED_APP}" &> /dev/null; then
		>&2 echo "missing ${REQUIRED_APP} from PATH"
		exit 1
	fi
done

COMPRESS_SCRIPT="$(cat << 'EOF'
set -euo pipefail

readonly FILE_NAME="$0"

errTrap() {
	>&2 echo "failed to compress $FILE_NAME"
}

trap errTrap ERR

FILE_SHA256="$(sha256sum < "${FILE_NAME}")"
readonly FILE_SHA256

if ! [ -e "${FILE_NAME}.zst" ] || [ "${FILE_SHA256}" != "$(zstd -d -c "${FILE_NAME}.zst" | sha256sum)" ]; then
	echo "zstd: $FILE_NAME"
	rm -f "${FILE_NAME}.zst"
	zstd -k -T0 --ultra -20 "${FILE_NAME}" &> /dev/null &
fi

if ! [ -e "${FILE_NAME}.gz" ] || [ "${FILE_SHA256}" != "$(gzip -d -c "${FILE_NAME}.gz" | sha256sum)" ]; then
	echo "gzip: $FILE_NAME"
	rm -f "${FILE_NAME}.gz"
	pigz -k -9 "${FILE_NAME}" &> /dev/null &
fi

if ! [ -e "${FILE_NAME}.br" ] || [ "${FILE_SHA256}" != "$(brotli -d -c "${FILE_NAME}.br" | sha256sum)" ]; then
	echo "brotli: $FILE_NAME"
	rm -f "${FILE_NAME}.br"
	brotli -k -9 "${FILE_NAME}" &> /dev/null &
fi

wait
EOF
)"
readonly COMPRESS_SCRIPT

ag --nocolor --ignore '*.gz' --ignore '*.zst' --ignore '*.br' -g '' -l "${SCAN_PATH}" |
	tr '\n' '\0' |
	xargs -0 -r -n 1 -P "$(nproc)" "$(command -v bash)" -c "${COMPRESS_SCRIPT}"