#!/usr/bin/env bash
# Exit on error.
set -e
# Exit on undefined variable reference.
set -u

script_dir="$(dirname "${BASH_SOURCE[0]}")"

function script_is_installed(){
  # Check if this script is run installed or locally (development setup).
  [ "${script_dir}" = '/usr/bin' ]
}

if script_is_installed; then
  lib_dir='/usr/lib/de-p1st-installer'
else
  lib_dir='./lib'
  # Print commands before they get executed.
  set -v
fi

# Source library files.
# shellcheck source=lib/validate-args.sh
source "${lib_dir}"/validate-args.sh
# shellcheck source=lib/util.sh
source "${lib_dir}"/util.sh
# shellcheck source=lib/user-input.sh
source "${lib_dir}"/user-input.sh
# shellcheck source=lib/block-device.sh
source "${lib_dir}"/block-device.sh

# Get path of configuration file.
if [ $# -eq 0 ]; then
  # No arguments given.
  if script_is_installed; then
    cfg_file=/etc/de-p1st-installer/installer.cfg
  else
    cfg_file="${script_dir}"/installer.cfg
  fi
else
  # >= 1 arguments given.
  # First argument is the configuration file!
  cfg_file="${1}"
fi

# Source the configuration file.
# shellcheck source=installer.cfg
source "${cfg_file}"

function main() {
  # @pre
  #   bash libraries imported
  # @post
  #   installation finished

  scrollback
  check_network
  system_time
  repository

  # in:  BOOT_PART_SIZE, BOOT_FIRMWARE, INITRAMFS, FS, HOSTNAME, USERNAME, USER_PWD, FDE, LUKS_PWD; (all variables are optional)
  # out: BOOT_PART_SIZE, BOOT_FIRMWARE, INITRAMFS, FS, HOSTNAME, USERNAME, USER_PWD, FDE, LUKS_PWD (if FDE='true')
  get_user_input
  # in:  CPU_VENDOR (optional)
  # out: CPU_VENDOR
  get_cpu_vendor CPU_VENDOR

  # in:  FS
  # out: FS_DEFAULT_MOUNT_OPTIONS
  get_default_mount_options
  # in:  FS
  # out: FS_ADDITIONAL_MOUNT_OPTIONS
  get_additional_mount_options

  # out: BOOT_PART, LUKS_PART
  partition \
    "${TARGET_BLOCK_DEVICE}" "${BOOT_FIRMWARE}" "${BOOT_PART_SIZE}" \
    BOOT_PART LUKS_PART
  # out: LUKS_PART_UUID (if FDE='true'), DATA_PART
  format \
    "${BOOT_PART}" "${LUKS_PART}" "${LUKS_PWD}" "${FDE}" "${FS}" \
    LUKS_PART_UUID DATA_PART

  # Join default and additional mount options by ','
  # shellcheck disable=SC2034
  FS_MOUNT_OPTIONS_ARRAY=("${FS_DEFAULT_MOUNT_OPTIONS[@]}" "${FS_ADDITIONAL_MOUNT_OPTIONS[@]}")
  join_by ',' FS_MOUNT_OPTIONS_ARRAY FS_MOUNT_OPTIONS

  mount_partitions

  # in: BOOT_FIRMWARE, INITRAMFS, PACSTRAP_INTERACTIVE (optional)
  run_pacstrap
  # in: FS
  run_genfstab

  # in: HOSTNAME, FQDN (optional), STATIC_IP (optional), IPV6_CAPABLE (optional)
  config_hostname_and_hosts
  # in: USERNAME, USER_PWD, ROOT_PWD (optional)
  user_and_pwd

  # in: INITRAMFS
  initramfs
  # in: TARGET_BLOCK_DEVICE, FDE, LUKS_PART_UUID
  bootloader

  unmount_partitions

  echo 'Finished installation without errors!'
}

function scrollback(){
  if ! grep --quiet '^defscrollback' /etc/screenrc; then
    printf '\n%s\n' "defscrollback 100000" | sudo tee -a /etc/screenrc
    printf '%s\n' 'Extended screen scrollback history. Pleas create a new screen session and run the installer again.'
    return 1
  fi

  if [ -z "${STY:-}" ]; then
    printf '%s\n' 'Pleas run the installer from a screen session.'
    return 1
  fi
}

function check_network() {
  echo 'Sending ping to wikipedia.de ...'
  ping -c 1 wikipedia.de >/dev/null || {
    echo 'Pleas set up network access and then run the installer again.'
    return 1
  }
}

function system_time() {
  # Use timedatectl(1) to ensure the system clock is accurate
  timedatectl set-ntp true
}

function repository(){
  # Check if the [de-p1st] repository is available.
  # If not, add it to pacman.conf

  if ! grep --quiet 'de-p1st' /etc/pacman.conf; then
    printf '%s\n' 'Enabling [de-p1st] package repository:'

    printf '\n%s\n' "[de-p1st]
SigLevel = Optional TrustAll
Server = https://arch.p1st.de" | sudo tee -a /etc/pacman.conf
  fi
}

function increase_cow_space() {
  # May be useful when running 'pacman -Syu' on the live medium.
  # Usually not necessary!

  # Make sure that we are on a live medium:
  findmnt /run/archiso/cowspace >/dev/null || {
    echo 'Not on live medium, did not increase cowspace!'
    return 1
  }

  echo 'Increasing cowspace partition of live medium ...'
  sudo mount -o remount,size=2G /run/archiso/cowspace
}

function get_user_input() {
  # @post
  #   BOOT_PART_SIZE
  #   BOOT_FIRMWARE: 'uefi' | 'bios'
  #   INITRAMFS: 'mkinitcpio' | 'dracut'
  #   FS: 'BTRFS' | 'EXT4' | 'F2FS'
  #   FS_BTRFS_SUBVOL_LAYOUT: 'root_only' | '@root@home'
  #   HOSTNAME
  #   USERNAME, USER_PWD
  #   FDE: 'true' | 'false'
  #   LUKS_PWD: only set if FDE='true'

  # out: BLOCK_DEVICE_SIZES
  get_block_devices_with_size BLOCK_DEVICE_SIZES
  single_choice_if_empty  TARGET_BLOCK_DEVICE 'Select target device for installation' BLOCK_DEVICE_SIZES

  ask_user_if_empty BOOT_PART_SIZE 'Enter boot partition size in MiB, at least 260:'

  if [ "${BOOT_FIRMWARE}" = 'autodetect' ]; then
    # Detect boot firmware type: https://askubuntu.com/a/162573

    # Check exit code; if 0 EFI, else BIOS.
    if dmesg | grep --quiet --fixed-strings 'EFI v'; then
      echo 'Detected EFI boot.'
      BOOT_FIRMWARE='uefi'
    else
      echo 'Detected BIOS boot'
      BOOT_FIRMWARE='bios'
    fi

  else  # If $BOOT_FIRMWARE is empty: Let user select BIOS type
    # shellcheck disable=SC2034
    BOOT_FIRMWARE_QUESTION=('uefi' 'Newer mainboards' \
                            'bios' 'Legacy BIOS on older mainboards')
    single_choice_if_empty  BOOT_FIRMWARE 'Select your bios type' BOOT_FIRMWARE_QUESTION
  fi

  # shellcheck disable=SC2034
  INITRAMFS_QUESTION=('mkinitcpio' 'Default for Arch Linux' \
                      'dracut'     'Testing')
  single_choice_if_empty  INITRAMFS 'Select filesystem to use' INITRAMFS_QUESTION

  # shellcheck disable=SC2034
  FS_QUESTION=('BTRFS' 'Allows snapshots and dynamic extension of the FS' \
               'EXT4'  'Default FS of many distributions' \
               'F2FS'  'Flash-Friendly-FS for SSD or NVMe')
  single_choice_if_empty  FS 'Select filesystem to use' FS_QUESTION

  if [ "${FS}" = 'BTRFS' ]; then
    # shellcheck disable=SC2034
    FS_QUESTION2=('root_only'  'Just one subvolume for "/".' \
          '@root@home' 'Two subvolumes @ and @home. This configuration allows usage of "Timeshift".')
    single_choice_if_empty  FS_BTRFS_SUBVOL_LAYOUT 'Select your preferred subvolume layout' FS_QUESTION2
  fi

  ask_user_if_empty HOSTNAME 'Enter hostname:'
  ask_user_if_empty USERNAME 'Enter username:'

  # If USER_PWD is  empty
  if [ -z "${USER_PWD}" ]; then
    ask_user_if_empty USER_PWD 'Enter a user password:'
    ask_user_if_empty USER_PWD2 'Please enter the password again:'
    # shellcheck disable=SC2153
    if [ "${USER_PWD}" != "${USER_PWD2}" ]; then
      echo 'Passwords did not match'
      exit 1
    fi
  fi

  # shellcheck disable=SC2034
  FDE_QUESTION=('true' 'Yes' 'false' 'No')
  single_choice_if_empty  FDE 'Shall Full-Disk-Encryption be enabled?' FDE_QUESTION

  # If FDE enabled but LUKS_PWD is  empty
  if [ "${FDE}" = 'true' ] && [ -z "${LUKS_PWD}" ]; then
    ask_user_if_empty LUKS_PWD 'Enter a disk encryption password:'
    ask_user_if_empty LUKS_PWD2 'Please enter the password again:'
    # shellcheck disable=SC2153
    if [ "${LUKS_PWD}" != "${LUKS_PWD2}" ]; then
      echo 'Passwords did not match'
      exit 1
    fi
  fi

  # ADDITIONAL_PKGS is an array, but all elements should be non-empty.
  # Thus, it is ok if we do only check the first element.
  if [ -z "${ADDITIONAL_PKGS:-}" ]; then
    ask_user_if_empty ADDITIONAL_PKGS 'Additional packages to install (separated by space):'
    space_separated_to_array ADDITIONAL_PKGS ADDITIONAL_PKGS || return $?
  fi
}

function get_default_mount_options() {
  # @pre
  #   FS
  # @post
  #   FS_DEFAULT_MOUNT_OPTIONS (array)

  FS_DEFAULT_MOUNT_OPTIONS=()

  case "${FS}" in
	BTRFS)
	  # "compress=lzo": archwiki -> Btrfs#Compression
	  # "compress=zstd:1":
	  #   -> https://btrfs.wiki.kernel.org/index.php/Compression#What_are_the_differences_between_compression_methods.3F
    #   -> https://fedoraproject.org/wiki/Changes/BtrfsTransparentCompression#Q:_Why_use_zstd:1_specifically.3F
    #
	  # "Enable compression (better performance, longer flash lifespan)"
		FS_DEFAULT_MOUNT_OPTIONS+=('compress=zstd:1')
		;;
	EXT4)
		FS_DEFAULT_MOUNT_OPTIONS+=()
		;;
  F2FS)
    # When mounting the filesystem, specify compress_algorithm=(lzo|lz4|zstd|lzo-rle).
    # Using compress_extension=txt will cause all txt files to be compressed by default.
    FS_DEFAULT_MOUNT_OPTIONS+=('compress_algorithm=lz4')
    ;;
	*)
		echo 'Filesystem '"${FS}"' not yet supported!'
		return 1
		;;
  esac
}

function get_additional_mount_options() {
  # @pre
  #   FS
  # @post
  #   FS_ADDITIONAL_MOUNT_OPTIONS (array)

  case "${FS}" in
	BTRFS)
	  # noatime, nodiratime:
	  # - `atime` impacts drive performance
	  # - `noatime` implies `nodiratime`, one does not need to specify both
	  # - `noatime` fully disables writing file access times to the drive every time you read a file.
	  #   This works well for almost all applications, except for those that need to know if a file has been
	  #   read since the last time it was modified.
	  FS_ADDITIONAL_MOUNT_OPTIONS_QUESTION=('noatime' 'Don'\''t write file/folder access times' 'on' 'ssd' 'Enable if using SSD/NVMe' 'off')
		;;
	EXT4)
	  FS_ADDITIONAL_MOUNT_OPTIONS_QUESTION=('noatime' 'Don'\''t write file/folder access times' 'on')
		;;
  F2FS)
    # shellcheck disable=SC2034
    FS_ADDITIONAL_MOUNT_OPTIONS_QUESTION=('noatime' 'Don'\''t write file/folder access times' 'on')
    ;;
	*)
		echo 'Filesystem '"${FS}"' not yet supported!'
		return 1
		;;
  esac

  multi_choice_if_empty  FS_ADDITIONAL_MOUNT_OPTIONS 'Select mount options' FS_ADDITIONAL_MOUNT_OPTIONS_QUESTION
}

function mount_partitions() {
  # @pre
  #   FS, FS_BTRFS_SUBVOL_LAYOUT, FS_MOUNT_OPTIONS, DATA_PART, BOOT_PART

  if [ "${FS}" = 'BTRFS' ]; then
      case "${FS_BTRFS_SUBVOL_LAYOUT}" in
      'root_only')
        # Nothing special; same steps as for a regular FS
        echo 'Mounting data partition with options: '"${FS_MOUNT_OPTIONS}"
        sudo mount -o "${FS_MOUNT_OPTIONS}" "${DATA_PART}" /mnt
        ;;
      '@root@home')
        # Timeshift BTRFS subvol layout:
        # https://github.com/teejee2008/timeshift#supported-system-configurations

        # Mount top level subvolume
        sudo mount -o subvolid=5 "${DATA_PART}" /mnt
        # Create subvolumes @ and @home
        sudo btrfs subvolume create /mnt/@
        sudo btrfs subvolume create /mnt/@home
        # List the created subvolumes
        sudo btrfs subvolume list /mnt
        # Umount the top level subvolume
        sudo umount -R /mnt

        echo 'Mounting @ and @home subvolumes with options: '"${FS_MOUNT_OPTIONS}"
        sudo mount -o 'subvol=@,'"${FS_MOUNT_OPTIONS}"     "${DATA_PART}" /mnt
        sudo mkdir /mnt/home
        sudo mount -o 'subvol=@home,'"${FS_MOUNT_OPTIONS}" "${DATA_PART}" /mnt/home
        ;;
      *)
        echo 'BTRFS subvolume layout '"${FS_BTRFS_SUBVOL_LAYOUT}"' not supported!'
        return 1
        ;;
      esac
  else
    echo 'Mounting data partition with options: '"${FS_MOUNT_OPTIONS}"
    sudo mount -o "${FS_MOUNT_OPTIONS}" "${DATA_PART}" /mnt
  fi

  echo 'Mounting boot partition ...'
  sudo mkdir /mnt/boot
  sudo mount "${BOOT_PART}" /mnt/boot

  # Print information about partitions.
  lsblk --tree=PATH -o PATH,TYPE,UUID
}

function run_pacstrap() {
  # @pre
  #   BOOT_FIRMWARE
  #   PACSTRAP_INTERACTIVE: optional, 'true'

  echo 'Running pacstrap ...'
  PKGS=("${ADDITIONAL_PKGS[@]}")

  case "${BOOT_FIRMWARE}" in
  uefi)
    PKGS+=('de-p1st-base')
    ;;
  bios)
    echo 'Not yet implemented'
    return 1
    ;;
  *)
    echo 'Not yet implemented!'
    return 1
    ;;
  esac

  case "${INITRAMFS}" in
  mkinitcpio)
    PKGS+=('de-p1st-mkinitcpio')
    ;;
  dracut)
    PKGS+=('dracut')
    # PKGS+=('binutils') # for --uefi (Unified Kernel Image) option
    PKGS+=('elfutils') # reduced initramfs size
    PKGS+=('multipath-tools') # dracut module support
    ;;
  *)
    echo 'Invalid option: '"${INITRAMFS}"
    return 1
    ;;
  esac

  case "${CPU_VENDOR}" in
  amd)
    PKGS+=('de-p1st-ucode-amd')
    ;;
  intel)
    PKGS+=('de-p1st-ucode-intel')
    ;;
  none)
    PKGS+=('de-p1st-ucode-none')
    ;;
  *)
    echo 'Invalid option: '"${CPU_VENDOR}"
    return 1
    ;;
  esac

  local args=()
  if [ "${PACSTRAP_INTERACTIVE}" = 'true' ]; then
    args+=('-i')  # Run interactively
  fi

  sudo pacstrap -K "${args[@]}" /mnt "${PKGS[@]}"
}

function run_genfstab() {
  # @pre
  #   FS

  echo 'Generating fstab ...'
  local fstab
  fstab="$(genfstab -U /mnt)"

  case "${FS}" in
	BTRFS)
	  # Remove "subvolid=..." mount option but leave "subvol=..." mount option
	  fstab=$(printf '%s' "${fstab}" | sed 's/,subvolid=[^,\s]\+//')
	  # Check if fstab does still contain subvolid mount option
    if printf '%s' "${fstab}" | grep --quiet 'subvolid='; then
	    echo 'This should not happen!'
	    return 1
    fi
		;;
	EXT4)
	  true
		;;
  F2FS)
    true
    ;;
	*)
		printf '%s\n' "Filesystem ${FS} not yet supported!"
		return 1
		;;
  esac

  echo 'Generating fstab'
  printf '%s' "${fstab}" | sudo tee /mnt/etc/fstab
}

function config_hostname_and_hosts() {
  # @pre
  #   HOSTNAME
  #   FQDN: optional, e.g. sub.domain.de
  #   STATIC_IP: optional, e.g. 93.133.433.133
  #   IPV6_CAPABLE: optional, 'true'

  echo 'Set hostname ...'
  echo "${HOSTNAME}" | sudo tee /mnt/etc/hostname >/dev/null

  echo 'Create hosts file ...'
  # If the system has a permanent IP address, it should be used instead of 127.0.1.1.
  # * https://wiki.archlinux.org/index.php/Installation_guide#Network_configuration

  # Desirable entries IPv4/IPv6:
  # * https://man.archlinux.org/man/hosts.5#EXAMPLES

  # If FQDN not given, use $HOSTNAME.localdomain instead
  FQDN="${FQDN:="${HOSTNAME}.localdomain"}"
  # If STATIC_IP not given, use 127.0.1.1 instead
  STATIC_IP="${STATIC_IP:=127.0.1.1}"

  echo '# The following lines are desirable for IPv4 capable hosts
127.0.0.1     localhost
# 127.0.1.1 is often used for the FQDN of the machine
'"${STATIC_IP}  ${FQDN}  ${HOSTNAME}" | sudo tee /mnt/etc/hosts >/dev/null

  if [ "${IPV6_CAPABLE}" = 'true' ]; then
    echo '
# The following lines are desirable for IPv6 capable hosts
::1           localhost ip6-localhost ip6-loopback
ff02::1       ip6-allnodes
ff02::2       ip6-allrouters' | sudo tee -a /mnt/etc/hosts >/dev/null
  fi
}

function user_and_pwd() {
  # @pre
  #   USERNAME
  #   USER_PWD
  #   ROOT_PWD (optional)

  echo 'Adding user and changing shell to /bin/zsh ...'
  # -m: Create home
  # -U: Create a group with the same name as the user, and add the user to this group.
  sudo arch-chroot /mnt useradd -m -s /usr/bin/zsh -g wheel "${USERNAME}"
  sudo arch-chroot /mnt chsh       -s /usr/bin/zsh

  if [ -z "${ROOT_PWD:-}" ]; then
    printf '%s\n' 'No root password given, using the user password for root'
    ROOT_PWD="${USER_PWD}"
  fi

  printf '%s:%s' "${USERNAME}" "${USER_PWD}" | sudo chpasswd --root /mnt
  printf '%s:%s' "root"        "${ROOT_PWD}" | sudo chpasswd --root /mnt
}

function initramfs(){
  # @pre
  #   INITRAMFS

  case "${INITRAMFS}" in
  mkinitcpio)
    sudo arch-chroot /mnt mkinitcpio -P
    ;;
  dracut)
    # configuration
    #   https://man.archlinux.org/man/dracut.conf.5
    #   https://man.archlinux.org/man/dracut.cmdline.7

    install -m0644 /dev/stdin /mnt/etc/dracut.conf.d/de-p1st.conf << 'EOF'
# --fstab
use_fstab=yes
# --show-modules
show_modules=yes

# https://wiki.archlinux.org/title/Dracut#LVM_/_software_RAID_/_LUKS
kernel_cmdline="rd.auto rd.luks=1"
EOF

    # TODO:
    #   Use a hook to do this
    #   on the running system after each
    #   kernel upgrade.

    # https://wiki.archlinux.org/title/Dracut#Generate_a_new_initramfs_on_kernel_upgrade
    #   - detect kernel version
    #   - install vmlinuz
    #   - run dracut

    for module in /mnt/lib/modules/*; do
      kernel="$(basename "${module}")"
      pkgbase="$(cat "${module}/pkgbase")"

      install -Dm644 "${module}/vmlinuz" "/mnt/boot/vmlinuz-${pkgbase}"

      echo 'Kernel command line:'
      arch-chroot /mnt dracut \
        --kver "${kernel}" \
        --print-cmdline \
        "/boot/initramfs-${pkgbase}.img"

      echo 'Creating initramfs:'
      arch-chroot /mnt dracut \
        --kver "${kernel}" \
        "/boot/initramfs-${pkgbase}.img"
    done
    ;;
  *)
    echo 'Invalid option: '"${INITRAMFS}"
    return 1
    ;;
  esac
}

function bootloader() {
  # @pre
  #   TARGET_BLOCK_DEVICE
  #   FDE: 'true' | 'false'
  #   LUKS_PART_UUID: required if FDE='true'

  echo 'Installing grub:'
  case "${BOOT_FIRMWARE}" in
  uefi)
    # Portable fallback efi name for grub:
    # * https://www.rodsbooks.com/efi-bootloaders/installation.html#alternative-naming
    # * arch-chroot /mnt cp /boot/EFI/GRUB/grubx64.efi /boot/EFI/BOOT/bootx64.efi
    sudo arch-chroot /mnt grub-install --target=x86_64-efi --bootloader-id=GRUB --efi-directory=/boot --removable
    ;;
  bios)
    sudo arch-chroot /mnt grub-install --target=i386-pc "${TARGET_BLOCK_DEVICE}"
    ;;
  *)
    echo 'Not yet implemented!'
    return 1
    ;;
  esac

  # grub.cfg adjustments
  if [ "${INITRAMFS}" = 'mkinitcpio' ] && [ "${FDE}" = "true" ]; then
    # /etc/default/grub is managed by Holo. Therefore we should not manually modify it.
    # Instead, we create a holosript which writes $LUKS_PART_UUID into GRUB_CMDLINE_LINUX of /etc/default/grub
    {
      # Use filename .../20- for the holoscript so that it gets executed after the one from de-p1st-grub
      local holoScriptDir=/mnt/usr/share/holo/files/20-de-p1st-installer/etc/default/
      # The holoscript shall contain one 'sed "..."' command
      sudo mkdir -p "${holoScriptDir}"
      sudo echo "#!/bin/sh
py-regex-replace -p '^GRUB_CMDLINE_LINUX=\"\"\$' -r 'GRUB_CMDLINE_LINUX=\"cryptdevice=/dev/disk/by-uuid/${LUKS_PART_UUID}:crypt\"'
" | sudo tee "${holoScriptDir}"/grub.holoscript
      sudo chmod 0544 "${holoScriptDir}"/grub.holoscript
    }
    # Then we apply the holoscript
    sudo arch-chroot /mnt holo apply --force file:/etc/default/grub

    # Print start of grub file containing GRUB_CMDLINE_LINUX
    head /mnt/etc/default/grub
  fi

  echo 'Generating /boot/grub/grub.cfg:'
  sudo arch-chroot /mnt grub-mkconfig -o /boot/grub/grub.cfg

  if [ "${INITRAMFS}" = 'mkinitcpio' ] && [ "${FDE}" = "true" ]; then
    printf '%s\n' 'Occurrence of "cryptdevice" in /boot/grub/grub.cfg:'
    grep 'cryptdevice' /mnt/boot/grub/grub.cfg
  fi
}

function unmount_partitions(){
  if [ "${LEAVE_MOUNTED}" = 'true' ]; then
    echo 'Leaving partitions below /mnt mounted and '"${DATA_PART}"' opened.'
  else
    echo 'unmount /mnt'
    sudo umount -R /mnt
    if [ "${FDE}" = 'true' ]; then
      echo "luksClose ${DATA_PART}"
      sudo cryptsetup luksClose "$(basename "${DATA_PART}")"
    fi
  fi
}

main "$@"