#!/usr/bin/env bash

set -euo pipefail
shopt -s inherit_errexit
#set -x

_git() {
	git -c safe.bareRepository=all "$@"
}

_ln() {
	rm -rf "$2" && ln -sf "$1" "$2"
}

if [[ ! -v ARCH_FLUTTER_TARGET_CPU || -z "$ARCH_FLUTTER_TARGET_CPU" ]]; then
	CARCH="${CARCH:-}"

	if [[ $CARCH == 'aarch64' ]]; then
		ARCH_FLUTTER_TARGET_CPU=arm64
	else
		ARCH_FLUTTER_TARGET_CPU=x64
	fi
fi

ARCH_FLUTTER_ENGINE_URL="${ARCH_FLUTTER_ENGINE_URL:-https://github.com/flutter/engine.git}"
ARCH_FLUTTER_DEPOT_TOOL_URL="${ARCH_FLUTTER_DEPOT_TOOL_URL:-https://chromium.googlesource.com/chromium/tools/depot_tools.git}"
readonly flutter_outdir="linux_release_$ARCH_FLUTTER_TARGET_CPU"

_setup_build_env()
{
	export \
		PATH="$(pwd)/.engine-src/depot_tools:$PATH" \
		DEPOT_TOOLS_UPDATE=0 \
		VPYTHON_BYPASS='manually managed python not supported by chrome operations'
}

setup_flutter_env()
{
	export FLUTTER_ENGINE="$(pwd)/.engine-src/engine"

	local -r engine_version="$(git -C "${FLUTTER_ENGINE}" describe --tags)"

	if [[ -n "$engine_version" && "$(vercmp "$engine_version" '3.16.0')" == -1 ]]; then
		export ARCH_FLUTTER_OPTS='--local-engine=arch_release --no-version-check --suppress-analytics'
	else
		export ARCH_FLUTTER_OPTS='--local-engine=arch_release --local-engine-host=arch_release --no-version-check --suppress-analytics'
	fi
}

_patch_flutter()
{
	#sed -i 's|"$FLUTTER_ROOT/bin/internal/update_dart_sdk.sh"|#|' "$1/bin/internal/shared.sh"
	sed -i 's|--no-enable-mirrors "$SCRIPT_PATH"|--no-enable-mirrors "$SCRIPT_PATH" $ARCH_FLUTTER_OPTS|' \
		"$1/bin/internal/shared.sh"
	sed -i 's|exec "$DART" --disable-dart-dev --packages="$FLUTTER_TOOLS_DIR/.dart_tool/package_config.json" $FLUTTER_TOOL_ARGS "$SNAPSHOT_PATH" "$@"|exec "$DART" --disable-dart-dev --packages="$FLUTTER_TOOLS_DIR/.dart_tool/package_config.json" $FLUTTER_TOOL_ARGS "$SNAPSHOT_PATH" $ARCH_FLUTTER_OPTS "$@"|' \
		"$1/bin/internal/shared.sh"

	#local -r dart_sdk="$(pwd)/.engine-src/engine/out/arch_release/dart-sdk"
	#rm -rf "$1/bin/cache/dart-sdk" || true
	#mkdir -p "$1/bin/cache"
	#_ln "$dart_sdk" "$1/bin/cache/dart-sdk"

	if false; then
	install -Dm755 '/dev/stdin' "$1/bin/dart" << EOF
#!/usr/bin/env sh

$dart_sdk/bin/dart "\$@"
EOF
	fi
}

_clone_src()
{
	local -r url="$1"
	local -r dest="$2"
	local -r ref="${3:-origin/HEAD}"
	local -r filename="$(basename "$dest")"

	# Clone repo.
	if [[ -e "$dest" ]]; then
		local remote_url="$(_git -C "$dest" config --get remote.origin.url)"
		if [[ "${url%%.git}" != "${remote_url%%.git}" ]] ; then
			>&2 echo "$dest is not a clone of $url."
			return 1
		fi

		_git -C "$dest" fetch --all -p
	else
		_git clone --mirror "$url" "$dest"
	fi

	local _abs_git_dir="$(_git -C "$dest" rev-parse --absolute-git-dir)"
	mkdir -p "$_abs_git_dir/info"
	echo '* -export-subst -export-ignore' > "$_abs_git_dir/info/attributes"

	# Create working copy in current dir.
	mkdir -p '.engine-src'
	if [[ -e ".engine-src/$filename" ]]; then
		_git -C ".engine-src/$filename" fetch
	else
		_git clone --origin=origin -s "$dest" ".engine-src/$filename"
	fi

	if [[ -n "$ref" ]]; then
		_git -C ".engine-src/$filename" checkout --force --no-track -B makepkg "$ref"
	fi
}

_prepare_build()
{
	local -r outdir="$1"
	local -r version="$2"

	if [[ $(vercmp "$version" '3.14.0') == -1 ]]; then
		local -r python_exec='python3.11'
	else
		local -r python_exec='python3'
	fi

	if ! "$python_exec" --version &>/dev/null; then
		>&2 echo "Engine version $version requires $python_exec."
		return 1
	fi

	sed -i "s/exec \"python3\"/exec \"$python_exec\"/" '.engine-src/depot_tools/vpython3'

	_setup_build_env

	local -r engine_src_dir="$(pwd)/.engine-src/engine"

	mkdir -p "$outdir" && pushd "$outdir"

	cat >.gclient <<EOF
solutions = [
	{
		"name": "src/flutter",
		"url": "file://${engine_src_dir}${version+"@$version"}",
		"managed": False,
		"custom_deps": {},
		"custom_vars": {}
	}
]
EOF

	gclient.py sync -n -D -R \
		--with_branch_heads \
		--with_tags \
		--output-json='gclient-sync.json' \
		--shallow \
		--no-bootstrap \
	|| { >&2 echo '`gclient.py sync` command failed.'; return 1; }

	sed -i "s/'python3'/'$python_exec'/" 'src/flutter/DEPS'

	gclient.py runhooks \
		|| { >&2 echo '`gclient.py runhooks` command failed.'; return 1; }

	cd 'src'

	sed -i 's|prefix = rebased_clang_dir|prefix= ""|g' 'build/toolchain/linux/BUILD.gn' # use system clang
	sed -i 's|}/|}|g' 'build/toolchain/linux/BUILD.gn' # use system clang
	sed -i 's|rebase|#|g' 'build/toolchain/linux/BUILD.gn'

	if [[ -e 'third_party/angle/BUILD.gn' ]]; then
		sed -i 's|$wayland_dir|//third_party/angle/third_party/wayland|' \
			'third_party/angle/BUILD.gn' \
			'third_party/angle/src/common/vulkan/BUILD.gn' \
			'third_party/angle/src/third_party/volk/BUILD.gn'
		sed -i 's|import("//build/config/chromecast_build.gni")||' 'third_party/angle/src/tests/BUILD.gn'
	fi

	sed -i '/-Wno-deprecated-literal-operator/d' 'build/config/compiler/BUILD.gn'
	sed -i '/G_DEFINE_AUTOPTR_CLEANUP_FUNC(PangoLayout, g_object_unref)/d' 'flutter/shell/platform/linux/fl_accessible_text_field.cc'

	# Not our problem.
	sed -i 's/"-Werror",//' 'build/config/compiler/BUILD.gn'

	cat > 'third_party/dart/build/dart/prebuilt_dart_sdk.gni' <<-EOF
		import("../executable_suffix.gni")
		_dart_root = rebase_path("../..")
		#_prebuilt_dart_exe = ""
		#_prebuilt_dart_exe_trial = ""
		prebuilt_dart_exe_works = true
EOF

	#_ln "${srcdir}/emsdk" 'buildtools/emsdk'
	popd
}

_build()
{
	local -r outdir="$1"

	_setup_build_env

	pushd "$outdir"
	cd 'src'

	"./flutter/tools/gn" --no-prebuilt-dart-sdk --verbose --out-dir="$outdir" \
		--linux \
		--linux-cpu="$ARCH_FLUTTER_TARGET_CPU" \
		--no-goma \
		--lto \
		--enable-vulkan \
		--target-sysroot='/' \
		--runtime-mode='release' \
		--no-enable-unittests \
	|| { >&2 echo '`gn gen` command failed.'; return 1; }

	sed -i 's|ldflags}|ldflags} -fuse-ld=lld|g' "$outdir/out/$flutter_outdir/toolchain.ninja" # use system linker
	ninja -v -C "$outdir/out/$flutter_outdir" \
		|| { >&2 echo 'Flutter engine build failed.'; return 1; }

	#export PATH+=":${srcdir}/src/flutter/lib/web_ui/dev"
	#felt build

	popd
}

_install()
{
	local -r outdir="$1"

	pushd "$outdir"

	find . -mindepth 1 -maxdepth 1 ! -name 'out' -exec rm -rf {} \;
	rm -rf "out/$flutter_outdir/"{gen,obj,lib.unstripped,exe.unstripped}
	ln -sf "$flutter_outdir" 'out/arch_release'
	ln -sf "$flutter_outdir" 'out/host_release'

	popd
}

_get_engine_version()
{
	local -r fvm_cache_dir="$1"

	local engine_version="$(fvm.real api project | yq -er '.project.pinnedVersion.name')"

	if [[ -z "$engine_version" || "$engine_version" == 'null' ]]; then
		engine_version="$(basename $(realpath "$fvm_cache_dir/default"))"
		if [[ -z "$engine_version" ]]; then
			>&2 echo "No version of flutter detected."
			return 1
		fi
	fi

	echo "$engine_version"
}

build_engine()
{
	local -r fvm_cache_dir="$(fvm.real api context | yq -er '.context.fvmDir')"
	local -r engine_version="$(_get_engine_version "$fvm_cache_dir")"

	if [[ -z "$engine_version" ]]; then
		>&2 echo "No version of flutter detected."
		return 1
	fi

	local -r cache_home="${XDG_CACHE_HOME:-"$HOME/.cache"}"
	local -r cached_flutter_engine_dir="$cache_home/flutter-engine/$ARCH_FLUTTER_TARGET_CPU/$engine_version"

	mkdir -p "$cached_flutter_engine_dir"
	_ln "$cached_flutter_engine_dir/out" '.engine-src/engine/out'

	#fvm.real api project

	{
		flock -s 3

		if [[ ! -L "$cached_flutter_engine_dir/out/arch_release" ]]; then
			_prepare_build "${cached_flutter_engine_dir}" "$engine_version" && \
			_build "${cached_flutter_engine_dir}" && \
			_install "${cached_flutter_engine_dir}" || \
				{ return 1; }
		fi

	} 3> "$cached_flutter_engine_dir/.lock"
}

download_and_patch()
{
	local -r fvm_cache_dir="$(fvm.real api context | yq -er '.context.fvmDir')"
	local -r fvm_version_cache="$(fvm.real api context | yq -er '.context.versionsCachePath')"
	local -r engine_version="$(_get_engine_version "$fvm_cache_dir")"
	local -r flutter_dir="$fvm_version_cache/$engine_version"

	_clone_src "$ARCH_FLUTTER_ENGINE_URL" "$fvm_cache_dir/engine" "$engine_version"
	_clone_src "$ARCH_FLUTTER_DEPOT_TOOL_URL" "$fvm_cache_dir/depot_tools"
	_patch_flutter "$flutter_dir"
}


cmd=
for (( i=1; i<=${#@}; i++ )); do
	if [[ ! "${!i}" =~ ^-.* ]]; then
		cmd="${!i}"
		break
	fi
done

case "$cmd" in
	dart|flutter)
		download_and_patch
		build_engine
		setup_flutter_env
		fvm.real "$@"
	;;
	*)
		fvm.real "$@"
	;;
esac