#!/usr/bin/env bash
# ─────────────────────────────────────────────────────────────────────────────
# Arcline OS — btrfs subvolume layout initialiser
#
#   btrfs/init.sh <device>            (e.g. /dev/sda2)
#   btrfs/init.sh --list <device>
#
# Creates the Arcline subvolume layout on a fresh (or existing) btrfs device:
#
#     @            → /            system root (rolled back on failure)
#     @home        → /home        user data
#     @log         → /var/log     logs (not rolled back, survives)
#     @snapshots   → /.snapshots  where arcline-snapshot keeps snapshots
#
# This is the step the installer runs; it is safe to re-run (existing
# subvolumes are kept, missing ones are created). Requires root.
# ─────────────────────────────────────────────────────────────────────────────
set -euo pipefail

DEV="${1:?usage: btrfs/init.sh <device>}"
TOP="/run/arcline-btrfs-init"

require_root() {
  if [[ $EUID -ne 0 ]] && command -v sudo >/dev/null; then
    exec sudo -E "$0" "$@"
  elif [[ $EUID -ne 0 ]]; then
    echo "error: needs root" >&2; exit 1
  fi
}
require_root "$0" "$@"

command -v btrfs >/dev/null || { echo "error: btrfs-progs not installed" >&2; exit 1; }

# Note: `blkid -O` is --offset, not "on device". Use a TYPE tag probe.
if [[ "$(blkid -p -s TYPE -o value "$DEV" 2>/dev/null)" != "btrfs" ]]; then
  echo "error: $DEV is not a btrfs filesystem" >&2
  exit 1
fi

mkdir -p "$TOP"
mount -o subvolid=5 "$DEV" "$TOP"
trap 'umount "$TOP" 2>/dev/null || true; rmdir "$TOP" 2>/dev/null || true' EXIT

create_subvol() {
  local name="$1"
  if [[ -d "$TOP/$name" ]]; then
    echo "  keeping existing subvolume: $name"
  else
    echo "  creating subvolume:        $name"
    btrfs subvolume create "$TOP/$name" >/dev/null
  fi
}

echo "Arcline btrfs layout on $DEV:"
create_subvol "@"
create_subvol "@home"
create_subvol "@log"
create_subvol "@snapshots"

# mark @snapshots read-only friendly (snapper/arcline-snapshot manage it)
btrfs property set -ts "$TOP/@snapshots" ro false 2>/dev/null || true

echo "done. The installer mounts:"
echo "  @          → /"
echo "  @home      → /home"
echo "  @log       → /var/log"
echo "  @snapshots → /.snapshots"