#!/bin/sh
set -eu

flutter_root=/opt/flutter

if [ -z "${FLUTTER_CACHE_DIR:-}" ] || [ -z "${PUB_CACHE:-}" ]; then
	if [ -n "${XDG_CACHE_HOME:-}" ]; then
		cache_home=${XDG_CACHE_HOME}
	elif [ -n "${HOME:-}" ]; then
		cache_home=${HOME}/.cache
	else
		echo "flutter: XDG_CACHE_HOME or HOME must be set when cache paths are not explicit" >&2
		exit 1
	fi
fi

if [ -z "${FLUTTER_CACHE_DIR:-}" ]; then
	FLUTTER_CACHE_DIR="${cache_home}/flutter/@PV@/bin-cache"
	export FLUTTER_CACHE_DIR
fi

if [ -z "${PUB_CACHE:-}" ]; then
	PUB_CACHE="${cache_home}/flutter/pub-cache"
	export PUB_CACHE
fi

seed_dir() {
	source_dir=$1
	destination_dir=$2
	stamp_name=$3

	mkdir -p "${destination_dir}"

	# Multiple Flutter processes can be started together by IDEs. Serialize the
	# initial copy so none of them sees a half-populated Dart/artifact cache.
	exec 9>"${destination_dir}/.gentoo-seed.lock"
	flock 9

	if [ ! -f "${destination_dir}/${stamp_name}" ] || \
		[ "$(cat "${destination_dir}/${stamp_name}" 2>/dev/null || true)" != "@PVR@" ]; then
		cp -a --reflink=auto --no-preserve=ownership "${source_dir}/." "${destination_dir}/"
		# The package-managed seed may deliberately be read-only. cp -a preserves
		# those modes, so restore owner write access in the per-user copy.
		chmod -R u+rwX "${destination_dir}"
		printf '%s\n' '@PVR@' > "${destination_dir}/${stamp_name}"
	fi

	flock -u 9
	exec 9>&-
}

preload_pub_cache() {
	preload_dir=$1
	destination_dir=$2
	stamp_name=$3

	mkdir -p "${destination_dir}"

	# Flutter installation bundles ship pub packages as compressed preload
	# archives rather than as a ready .pub-cache. Because this wrapper sets
	# PUB_CACHE explicitly, Flutter's own automatic preload path is bypassed.
	# Populate the user's selected cache here exactly once per Flutter version.
	exec 9>"${destination_dir}/.gentoo-preload.lock"
	flock 9

	if [ ! -f "${destination_dir}/${stamp_name}" ] || \
		[ "$(cat "${destination_dir}/${stamp_name}" 2>/dev/null || true)" != "@PVR@" ]; then
		set -- "${preload_dir}"/*.tar.gz
		if [ ! -e "$1" ]; then
			echo "flutter: installation bundle contains no pub preload archives" >&2
			exit 1
		fi

		PUB_CACHE="${destination_dir}" \
			"${FLUTTER_CACHE_DIR}/dart-sdk/bin/dart" \
			pub --suppress-analytics cache preload "$@"
		printf '%s\n' '@PVR@' > "${destination_dir}/${stamp_name}"
	fi

	flock -u 9
	exec 9>&-
}

# The official Flutter archive is already populated with the Dart SDK and
# binary artifacts. Treat the package-managed copy as an immutable seed and
# give every user a writable cache of their own.
seed_dir "${flutter_root}/bin/cache" "${FLUTTER_CACHE_DIR}" .gentoo-flutter-seed-version

# Flutter 3.47 installation bundles carry pub packages in .pub-preload-cache.
# Preload those archives into the explicit per-user PUB_CACHE. This mirrors
# Flutter's first-run behavior without writing to or deleting anything in
# /opt/flutter, and allows the first project creation to work offline.
if [ -d "${flutter_root}/.pub-preload-cache" ]; then
	preload_pub_cache \
		"${flutter_root}/.pub-preload-cache" \
		"${PUB_CACHE}" \
		.gentoo-flutter-pub-preload-version
elif [ -d "${flutter_root}/.pub-cache" ]; then
	# Retain compatibility with bundles that contain an expanded pub cache.
	seed_dir "${flutter_root}/.pub-cache" "${PUB_CACHE}" .gentoo-flutter-pub-seed-version
else
	mkdir -p "${PUB_CACHE}"
fi

exec "${flutter_root}/bin/flutter" "$@"