#!/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 -uex

ARCH=${1:-aarch64}

ARCHIVE=nix-2.2.2-$ARCH-linux.tar.bz2
BASEURL=https://nixos.org/releases/nix/nix-2.2.2
URL="$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

echo "building proot for $ARCH (this may take a lot of time...)"
nix build -f proot.nix -o proot-$ARCH --argstr arch aarch64

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

if [[ $ARCH != x86_64 && $ARCH != i686 ]]; then
	wget https://github.com/multiarch/qemu-user-static/releases/download/v4.0.0-4/qemu-$ARCH-static -O qemu-$ARCH
	chmod +x qemu-$ARCH
fi

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"

if [[ $ARCH != x86_64 && $ARCH != i686 ]]; then
	PROOT_CMD="./proot-host -q ./qemu-$ARCH -r bootstrap -w /"
else
	PROOT_CMD="./proot-host -b /dev -r bootstrap -w /"
fi

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-$ARCH/bin/proot 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/bin
mkdir -p bootstrap/root
mkdir -p bootstrap/tmp
mkdir -p bootstrap/.l2s
cat > bootstrap/bin/login <<EOF
#!/system/bin/sh
set -e

export USER=\$(/system/bin/whoami)
export PROOT_TMP_DIR=$INST/tmp
export PROOT_L2S_DIR=$INST/.l2s

if [ ! -e $INST/etc/passwd ]; then
	[ -n "$@" ] || echo "Creating /etc/passwd..."
	echo "root:x:0:0:System administrator:$INST/root:/bin/sh" > $INST/etc/passwd
	echo "nix-on-droid:x:\$(/system/bin/stat -c '%u:%g' $INST):nix-on-droid:/data/data/com.termux.nix/files/home:/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

[ "\$#" -gt 1 ] || echo "Welcome to Nix-on-Droid!"

[ "\$#" -gt 1 ] || echo "If nothing works, use the rescue shell and read $INST/bin/.login-inner"
[ "\$#" -gt 1 ] || echo "If it does not help, report bugs at https://github.com/t184256/nix-on-droid-bootstrap/issues"

export USER="\$1"
export HOME="/data/data/com.termux.nix/files/home"
shift

[ "\$#" -gt 0 ] || 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
	[ "\$#" -gt 0 ] || echo "Sourcing home-manager environment..."
	export NIX_PATH=\$HOME/.nix-defexpr/channels\${NIX_PATH:+:}\$NIX_PATH
	. "\$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh"
fi

if [ "\$#" -eq 0 ]; then
	if [ ! -e "\$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh" ]; then
		echo "Congratulations. Now you have Nix installed, but that's kinda it."
		echo "Hope you're a seasoned Nix user, because stuff is not pretty yet."
		echo "If you wonder what to do next, and want to do it the hard way, start with running"
		echo "  nix-channel --add https://nixos.org/channels/nixos-19.03 nixpkgs"
		echo "  nix-channel --update"
		echo "After that you can summon software from nixpkgs (e.g. gitMinimal):"
		echo "* by asking for a shell that has it:"
		echo "    nix run nixpkgs.bashInteractive nixpkgs.gitMinimal"
		echo "* or installing it into the user environment (not recommended):"
		echo "    nix-env -iA nixpkgs.gitMinimal"
		echo "* or, the best way, declaratively with home-manager:"
		echo "    0. nix-on-droid-install"
		echo "    1. [get an editor and edit ~/.config/nixpkgs/home.nix]"
		echo "    2. home-manager switch"
		echo "or a myriad other ways."
		echo "You should really consider installing at least: nix, cacert and coreutils."
		echo "bashInteractive and a text editor should be high on the list too."
		echo
		echo "If you want the easy way, nix-on-droid-install should get all this covered."
		echo
		echo "TL;DR: run nix-on-droid-install and things will get better."
		echo
		echo "Dropping you into an extremely limited shell (that has Nix though). Happy hacking!"
		export PATH="$TGT_NIX/bin:\$PATH"
		exec /bin/sh
	fi

	echo "Dropping you into a shell. Happy hacking!"
	exec /usr/bin/env bash
else
	exec /usr/bin/env "\$@"
fi
EOF
chmod +x bootstrap/bin/.login-inner


cat > bootstrap/bin/nix-on-droid-install <<EOF
#!/bin/sh
set -e

if [ -e \$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh ]; then
	echo "You already have home-manager installed."
fi

echo "Installing home-manager and other good stuff..."

echo "Subscribing to the stable (nixos-19.03) channel of nixpkgs..."
echo "If you want unstable instead, you probably also know what to do."
$TGT_NIX/bin/nix-channel --add https://nixos.org/channels/nixos-19.03 nixpkgs
echo "Subscribing to home-manager channel..."
$TGT_NIX/bin/nix-channel --add https://github.com/rycee/home-manager/archive/master.tar.gz home-manager
echo "Updating channels..."
$TGT_NIX/bin/nix-channel --update
echo "Whew."

export NIX_PATH=\$HOME/.nix-defexpr/channels\${NIX_PATH:+:}\$NIX_PATH

if [ ! -e \$HOME/.config/nixpkgs/home.nix ]; then
	echo "Creating an initial home-manager configuration in ~/.config/nixpkgs/home.nix ..."
	$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
fi

echo "Installing home-manager..."
$TGT_NIX/bin/nix run nixpkgs.nix -c $TGT_NIX/bin/nix-shell '<home-manager>' -A install

echo "Edit ~/.config/nixpkgs/home.nix and home-manager rebuild to control what is going on."
echo "Run bash or restart your session to enjoy a much nicer environment."
EOF
chmod +x bootstrap/bin/nix-on-droid-install


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;

  # Install and configure software declaratively
  #programs.git = {
  #  enable = true;
  #  userName = "Jane Doe";
  #  userEmail = "jane.doe@example.org";
  #};

  # Simply install just the packages
  home.packages = with pkgs; [
    # Stuff that you really really want to have
    nix cacert coreutils  # think twice before removing these

    # User-facing stuff that you really really want to have
    bashInteractive   # think twice before removing thes
    vim  # or some other editor, e.g. nano or neovim

    # Some common stuff that people expect to have
    #diffutils
    #findutils
    #utillinux
    #tzdata
    #hostname
    #man
    #gnugrep
    #gnupg
    #gnused
    #gnutar
    #bzip2
    #gzip
    #xz
    #zip
    #unzip
  ];
}
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..."
find bootstrap -type l |
while read -r LINK; do
	LNK=${LINK#bootstrap/}
	TGT=$(readlink "$LINK")
	echo "$TGT←$LNK" >> bootstrap/SYMLINKS.txt
	rm "$LINK"
done

echo "packing..."
rm -f bootstrap-$ARCH.zip
(cd bootstrap; zip -q -9 -r ../bootstrap-$ARCH ./* ./.l2s)

echo "done"