#!/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>&-
}

# The package-managed Flutter SDK provides a deterministic cache layout with
# symlinks to system Dart and Engine artifacts. Treat /opt/flutter/bin/cache 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

# Preloaded pub packages for flutter_tools are preserved in .pub-cache.
# Seed the user's PUB_CACHE on first run so offline tooling commands succeed.
if [ -d "${flutter_root}/.pub-cache" ]; then
	seed_dir "${flutter_root}/.pub-cache" "${PUB_CACHE}" .gentoo-flutter-pub-seed-version
else
	mkdir -p "${PUB_CACHE}"
fi

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