#!/usr/bin/env bash

# This script builds the initial bootstrap zipball for Nix on Android.
# Copyright (c) 2019 Alexander Sosedkin <monk@unboiled.info>

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

set -ue

ARCHIVE=nix-2.2.1-aarch64-linux.tar.bz2
BASEURL=https://nixos.org/releases/nix/nix-2.2.1
URL="$BASEURL/$ARCHIVE"
INST="/data/data/com.termux.nix/files/usr"

export PROOT_NO_SECCOMP=1  # see https://github.com/proot-me/PRoot/issues/106

rm -rf ./bootstrap
mkdir -p bootstrap

wget https://github.com/proot-me/proot-static-build/blob/master/static/proot-x86_64?raw=true -O proot-host
chmod +x proot-host

wget https://github.com/multiarch/qemu-user-static/releases/download/v3.1.0-2/qemu-aarch64-static -O qemu-aarch64
chmod +x qemu-aarch64

echo "downloading nix archive"
wget $URL -O $ARCHIVE

echo -n "extracting $ARCHIVE "
tar -xf "$ARCHIVE" -C bootstrap --checkpoint=200 --checkpoint-action=dot
echo " done"
mv bootstrap/nix* bootstrap/nix-installer

echo -n "copying store... "
mkdir bootstrap/nix
cp -r bootstrap/nix-installer/store bootstrap/nix/
echo "done"

mkdir -p bootstrap/bin
TGT_SHELL=$(find bootstrap/nix/store -path '*/bin/bash' | sed s/^bootstrap//)
echo "shell found at $TGT_SHELL"
ln -s "$TGT_SHELL" bootstrap/bin/sh

mkdir -p bootstrap/usr/bin
TGT_ENV=$(find bootstrap/nix/store -path '*/bin/env' | sed s/^bootstrap//)
echo "env found at $TGT_ENV"
ln -s "$TGT_ENV" bootstrap/usr/bin/env

TGT_NIX=$(find bootstrap/nix/store -path '*/bin/nix' | sed s/^bootstrap//)
TGT_NIX=${TGT_NIX%/bin/nix}
echo "nix derivation found at $TGT_NIX"

TGT_CACERT=$(find bootstrap/nix/store -path *-nss-cacert-*/ca-bundle.crt | sed s/^bootstrap//)
echo "cacert found at $TGT_CACERT"

PROOT_CMD="./proot-host -q ./qemu-aarch64 -r bootstrap -w /"

echo "initialising Nix database..."
$PROOT_CMD "$TGT_NIX/bin/nix-store" --init

echo "registering paths..."
$PROOT_CMD "$TGT_NIX/bin/nix-store" --load-db < bootstrap/nix-installer/.reginfo

echo "injecting proot..."
mkdir -p bootstrap/bin
cp proot-tgt bootstrap/bin/proot

echo "making up some resolv.conf..."
mkdir -p bootstrap/etc
echo -e "nameserver 1.1.1.1\nnameserver 8.8.8.8" > bootstrap/etc/resolv.conf

echo "disabling sandboxing..."  # we can't rely on USER_NS support
mkdir -p bootstrap/etc/nix
echo "sandbox = false " > bootstrap/etc/nix/nix.conf

echo "composing login scripts..."
mkdir -p bootstrap/tmp
mkdir -p bootstrap/bin
cat > bootstrap/bin/login <<EOF
#!/system/bin/sh
set -e
export USER=\$(/system/bin/whoami)
export PROOT_TMP_DIR=$INST/tmp

if [ ! -e $INST/etc/passwd ]; then
	echo "Creating an entry in /etc/passwd..."
	echo "nix-on-droid:x:\$(/system/bin/stat -c '%u:%g' $INST):nix-on-droid:/bin/sh" > $INST/etc/passwd
fi

exec $INST/bin/proot \
	-b $INST/nix:/nix \
	-b $INST/bin:/bin \
	-b $INST/etc:/etc \
	-b $INST/tmp:/tmp \
	-b $INST/usr:/usr \
	-b /:/android \
	--link2symlink \
	$INST/bin/sh $INST/bin/.login-inner \$USER "\$@"
EOF

chmod +x bootstrap/bin/login
cat > bootstrap/bin/.login-inner <<EOF
set -e

echo "Welcome to Nix-on-Droid!"

export USER="\$1"
shift

echo "Sourcing Nix environment..."
. $INST/$TGT_NIX/etc/profile.d/nix.sh

if [ ! -e \$HOME/.nix-profile/etc/ssl/certs/ca-bundle.crt ]; then
	if [ -e $TGT_CACERT ]; then
		export NIX_SSL_CERT_FILE=$TGT_CACERT
	fi
fi

if [ ! -e \$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh ]; then
	echo "Continuing with stage2 on-device installation..."

	export NIX_SSL_CERT_FILE=$TGT_CACERT
	echo "Subscribing to the stable (nixos-18.09) channels of nixpkgs and home-manager..."
	$TGT_NIX/bin/nix-channel --add https://nixos.org/channels/nixos-18.09 nixpkgs
	$TGT_NIX/bin/nix-channel --add https://github.com/rycee/home-manager/archive/release-18.09.tar.gz home-manager
	$TGT_NIX/bin/nix-channel --update

	echo "Creating an initial home-manager configuration in ~/.config/nixpkgs/home.nix ..."
	export NIX_PATH=\$HOME/.nix-defexpr/channels\${NIX_PATH:+:}\$NIX_PATH
	$TGT_NIX/bin/nix run nixpkgs.coreutils -c mkdir -p \$HOME/.config/nixpkgs/
	$TGT_NIX/bin/nix run nixpkgs.coreutils -c cp -n $INST/etc/home.nix.default \$HOME/.config/nixpkgs/home.nix
	echo "Installing home-manager..."
	$TGT_NIX/bin/nix run nixpkgs.nix -c $TGT_NIX/bin/nix-shell '<home-manager>' -A install
else
	export NIX_PATH=\$HOME/.nix-defexpr/channels\${NIX_PATH:+:}\$NIX_PATH
fi

echo "Sourcing home-manager environment..."
. "\$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh"

echo "Dropping you into a shell."
echo "You can summon software from nixpkgs (e.g. gitMinimal) with:"
echo "  * nix run nixpkgs.gitMinimal"
echo "  * nix-env -iA nixpkgs.gitMinimal"
echo "  * [edit ~/.config/nixpkgs/home.nix and run] home-manager switch"
echo "or a myriad other ways."
echo "Happy hacking!"
exec /usr/bin/env bash "\$@"
EOF
chmod +x bootstrap/bin/.login-inner

echo "providing a default home-manager config..."
cat > bootstrap/etc/home.nix.default <<EOF
{ pkgs, ... }:

{
  # Let Home Manager install and manage itself.
  programs.home-manager.enable = true;

  home.packages = with pkgs; [
    nix cacert tzdata coreutils
    diffutils findutils utillinux
    gnugrep gnupg gnused gnutar hostname man
    bzip2 gzip unzip xz zip
    bashInteractive less vim
  ];
}
EOF

echo "removing nix-installer..."
rm -rf bootstrap/nix-installer

echo "finding executables..."
find bootstrap -executable -type f | \
	sed s@^bootstrap/@@ \
	> bootstrap/EXECUTABLES.txt

echo "finding symlinks..."
for LINK in $(find bootstrap -type l); do
	LNK=$(echo "$LINK" | sed s@^bootstrap/@@)
	TGT=$(readlink $LINK)
	echo "$TGT←$LNK" >> bootstrap/SYMLINKS.txt
	rm "$LINK"
done

echo "packing..."
rm -f bootstrap-aarch64.zip
(cd bootstrap; zip -q -9 -r ../bootstrap-aarch64 ./*)
cp bootstrap-aarch64.zip ../nix-on-droid-app/app/src/main/assets/bootstrap-aarch64

echo "done"