void_install_script_v2.sh

#!/usr/bin/env bash
set -euo pipefail

### ====== EDIT ME (DISKS & BASICS) ==========================================
# Root (NVMe) disk -> ESP + LUKS1 for root btrfs
ROOT_DISK="/dev/sda"
# Data (SATA/SSD) disk -> LUKS1 for data btrfs
DATA_DISK="/dev/sdb"

# Partition sizes
ESP_SIZE="1024MiB"   # EFI System Partition size on ROOT_DISK

# Swap size (hibernation capable) - currently used as swapfile space, not a partition
SWAP_SIZE="18G"

### ====== LIVE ISO PREFLIGHT (tools needed before installation) ==============
echo "==> Ensuring required live-ISO tools are present..."

# Detect a package manager once
detect_pkg_manager() {
  for pm in xbps-install apt-get dnf yum zypper pacman; do
    if command -v "$pm" >/dev/null 2>&1; then
      echo "$pm"
      return 0
    fi
  done
  return 1
}

PKG_MANAGER="$(detect_pkg_manager || true)"

install_pkg() {
  local pkg="$1"

  if [[ -z "${PKG_MANAGER:-}" ]]; then
    echo "!! No supported package manager found (xbps-install/apt-get/dnf/yum/zypper/pacman)."
    echo "   Please install '$pkg' manually and re-run the script."
    exit 1
  fi

  case "$PKG_MANAGER" in
    xbps-install)
      xbps-install -Sy "$pkg"
      ;;
    apt-get)
      apt-get update
      apt-get install -y "$pkg"
      ;;
    dnf)
      dnf install -y "$pkg"
      ;;
    yum)
      yum install -y "$pkg"
      ;;
    zypper)
      zypper --non-interactive install --no-recommends "$pkg"
      ;;
    pacman)
      pacman -Sy --noconfirm "$pkg"
      ;;
    *)
      echo "!! Unsupported package manager: $PKG_MANAGER"
      echo "   Please install '$pkg' manually and re-run."
      exit 1
      ;;
  esac
}

need() {
  local bin="$1"
  local pkg="$2"
  if ! command -v "$bin" >/dev/null 2>&1; then
    echo "==> Installing missing tool '$bin' (package: $pkg) using $PKG_MANAGER..."
    install_pkg "$pkg"
  fi
}

# For partitioning
need sgdisk  gptfdisk
need partprobe parted

# Also make sure these exist (common across distros)
need cryptsetup cryptsetup
need mkfs.btrfs btrfs-progs
need btrfs btrfs-progs

# Helper: re-read partition table safely
reread_pt() {
  local disk="$1"
  if command -v partprobe >/dev/null 2>&1; then
    partprobe "$disk" || true
  else
    blockdev --rereadpt "$disk" || true
    command -v udevadm >/dev/null 2>&1 && udevadm settle || true
    sleep 1
  fi
}

# Calculate free-at-end reservation-aware size on a disk (MiB)
# - Finds the LAST "free;" region via parted
# - free_mib = size of that region
# - ten_percent = free_mib / 10, capped at 51205 MiB
# - returns: free_mib - ten_percent (or - cap)
calc_disk_reservation() {
  local disk="$1"

  if [[ -z "$disk" || ! -b "$disk" ]]; then
    echo "Error: '$disk' is not a valid block device" >&2
    return 1
  fi

  if ! command -v parted >/dev/null 2>&1; then
    echo "Error: 'parted' is required but not installed" >&2
    return 1
  fi

  local free_mib
  free_mib="$(
    parted -m -s "$disk" unit MiB print free 2>/dev/null \
    | awk -F: '
        # Only lines whose last field is "free;"
        $NF == "free;" {
            size = $4               # e.g. "31743MiB"
            sub(/MiB$/, "", size)   # strip unit
            last = size + 0         # overwrite: we want the last free region
        }
        END {
            if (last == "") last = 0
            printf "%.0f\n", last   # integer MiB
        }
      '
  )"

  [[ -z "$free_mib" ]] && free_mib=0

  local ten_percent=$(( free_mib / 10 ))
  local cap=51205
  local reserve=$ten_percent
  if (( ten_percent > cap )); then
    reserve=$cap
  fi

  local final=$(( free_mib - reserve ))
  (( final < 0 )) && final=0

  printf '%d\n' "$final"
}

### ====== NO EDITS BELOW UNLESS YOU KNOW WHAT YOU'RE DOING ===================

echo "==> Validating disks..."
[[ -b "$ROOT_DISK" ]] || { echo "Root disk not found: $ROOT_DISK"; exit 1; }
[[ -b "$DATA_DISK" ]] || { echo "Data disk not found: $DATA_DISK"; exit 1; }

echo "==> Wiping old signatures..."
wipefs -a "$ROOT_DISK"
wipefs -a "$DATA_DISK"

echo "==> Partitioning $ROOT_DISK (GPT: ESP + root LUKS sized via reservation)..."
sgdisk --zap-all "$ROOT_DISK"
sgdisk -o "$ROOT_DISK"        # create new GPT so parted can see it

# ESP (fixed size)
sgdisk -n 1:0:+"$ESP_SIZE" -t 1:ef00 -c 1:"EFI System Partition" "$ROOT_DISK"
reread_pt "$ROOT_DISK"

# Compute root partition size: free-at-end minus 10% (capped)
ROOT_ROOT_SIZE_MIB="$(calc_disk_reservation "$ROOT_DISK")"
if [[ -z "$ROOT_ROOT_SIZE_MIB" || "$ROOT_ROOT_SIZE_MIB" -le 0 ]]; then
  echo "Error: calculated root partition size for $ROOT_DISK is invalid: '$ROOT_ROOT_SIZE_MIB' MiB" >&2
  exit 1
fi
echo "==> Root partition size on $ROOT_DISK: ${ROOT_ROOT_SIZE_MIB}MiB (reservation-adjusted)"

# root LUKS (use +<MiB>M, sgdisk interprets 'M' as MiB)
sgdisk -n 2:0:+"${ROOT_ROOT_SIZE_MIB}M" -t 2:8300 -c 2:"cryptroot" "$ROOT_DISK"
reread_pt "$ROOT_DISK"

echo "==> Partitioning $DATA_DISK (GPT: data LUKS sized via reservation)..."
sgdisk --zap-all "$DATA_DISK"
sgdisk -o "$DATA_DISK"        # new GPT label for data disk
reread_pt "$DATA_DISK"

# Compute data partition size on DATA_DISK
DATA_SIZE_MIB="$(calc_disk_reservation "$DATA_DISK")"
if [[ -z "$DATA_SIZE_MIB" || "$DATA_SIZE_MIB" -le 0 ]]; then
  echo "Error: calculated data partition size for $DATA_DISK is invalid: '$DATA_SIZE_MIB' MiB" >&2
  exit 1
fi
echo "==> Data partition size on $DATA_DISK: ${DATA_SIZE_MIB}MiB (reservation-adjusted)"

# data LUKS
sgdisk -n 1:0:+"${DATA_SIZE_MIB}M" -t 1:8300 -c 1:"crypthome" "$DATA_DISK"
reread_pt "$DATA_DISK"

ESP_PART="${ROOT_DISK}p1"
ROOT_PART="${ROOT_DISK}p2"
DATA_PART="${DATA_DISK}1"
# Handle non-NVMe naming (e.g., /dev/sda1 already ends with 1)
[[ -b "$ESP_PART" ]]  || ESP_PART="${ROOT_DISK}1"
[[ -b "$ROOT_PART" ]] || ROOT_PART="${ROOT_DISK}2"

echo "==> Creating LUKS1 containers..."
cryptsetup luksFormat --type luks1 -y "$ROOT_PART"
cryptsetup luksFormat --type luks1 -y "$DATA_PART"

echo "==> Opening LUKS containers..."
cryptsetup open "$ROOT_PART" cryptroot
cryptsetup open "$DATA_PART" cryptdata

echo "==> Creating filesystems..."
mkfs.vfat -F32 -n EFI "$ESP_PART"
mkfs.btrfs -L void_root -m single /dev/mapper/cryptroot
mkfs.btrfs -L void_data -m single /dev/mapper/cryptdata

echo "==> Creating Btrfs subvolumes..."
# Root FS: mount top-level, create subvols, unmount
mount /dev/mapper/cryptroot /mnt
btrfs subvolume create /mnt/@
btrfs subvolume create /mnt/@opt
btrfs subvolume create /mnt/@usr_local
btrfs subvolume create /mnt/@root
umount /mnt

# Data FS: mount top-level, create subvols, unmount
mount /dev/mapper/cryptdata /mnt
btrfs subvolume create /mnt/@home
btrfs subvolume create /mnt/@snapshots
btrfs subvolume create /mnt/@var_lib
btrfs subvolume create /mnt/@var_log
btrfs subvolume create /mnt/@var_cache
btrfs subvolume create /mnt/@var_tmp
btrfs subvolume create /mnt/@var_swap
umount /mnt

echo "==> Mounting subvolumes..."
BTRFS_OPTS="rw,noatime,ssd,compress=zstd,space_cache=v2"
DATA_MAPPER="/dev/mapper/cryptdata"   # <- ensure this matches your 'cryptsetup open' name

# Root (drive #1)
mount -o "$BTRFS_OPTS",subvol=@ /dev/mapper/cryptroot /mnt
mkdir -p /mnt/{opt,usr/local,root,home,snapshots}
mkdir -p /mnt/var /mnt/var/{lib,log,cache,tmp,swap}

mount -o "$BTRFS_OPTS",subvol=@opt        /dev/mapper/cryptroot /mnt/opt
mount -o "$BTRFS_OPTS",subvol=@usr_local  /dev/mapper/cryptroot /mnt/usr/local
mount -o "$BTRFS_OPTS",subvol=@root       /dev/mapper/cryptroot /mnt/root

# Data (drive #2)
mount -o "$BTRFS_OPTS",subvol=@home       "$DATA_MAPPER" /mnt/home
mount -o "$BTRFS_OPTS",subvol=@snapshots  "$DATA_MAPPER" /mnt/snapshots

# /var subtree mounts (order matters)
mount -o "$BTRFS_OPTS",subvol=@var_lib    "$DATA_MAPPER" /mnt/var/lib
mount -o "$BTRFS_OPTS",subvol=@var_log    "$DATA_MAPPER" /mnt/var/log
mount -o "$BTRFS_OPTS",subvol=@var_cache  "$DATA_MAPPER" /mnt/var/cache
mount -o "$BTRFS_OPTS",subvol=@var_tmp    "$DATA_MAPPER" /mnt/var/tmp
mount -o "$BTRFS_OPTS",subvol=@var_swap   "$DATA_MAPPER" /mnt/var/swap

# ESP
mkdir -p /mnt/boot/efi
mount -o rw,noatime "$ESP_PART" /mnt/boot/efi

echo "==> Disabling CoW where needed (var heavy dirs + swap dir)..."

# NOCOW helper: apply to the directory and any existing regular files
set_nocow_dir() {
  local d="$1"
  mkdir -p "$d"
  chattr +C "$d" 2>/dev/null || true
  find "$d" -xdev -type f -print0 2>/dev/null | xargs -0r chattr +C 2>/dev/null || true
}

set_nocow_dir /mnt/var/lib
set_nocow_dir /mnt/var/log
set_nocow_dir /mnt/var/cache
set_nocow_dir /mnt/var/tmp
set_nocow_dir /mnt/var/swap

echo "==> Done. Layout prepared."