#!/usr/bin/env bash
# CareTV mergerfs Existing-Data Adoption / Pool Rebuild
# Version: v001
#
# IMPORTANT DIFFERENCE FROM WINDOWS DRIVEPOOL:
# mergerfs does NOT require files to be moved into a hidden pool folder.
# Existing files remain exactly where they already are.
# To "adopt" a disk, add its mount point as a mergerfs branch.
#
# This script:
#   1. Reads branch mount points from /etc/caretv/mergerfs-branches.conf
#   2. Verifies every branch exists and is mounted
#   3. Creates /caretv if necessary
#   4. Mounts/re-mounts the unified mergerfs namespace at /caretv
#
# It does NOT move, copy, delete, format, or rebalance existing files.

set -euo pipefail

CONFIG="/etc/caretv/mergerfs-branches.conf"
POOL="/caretv"

if [[ $EUID -ne 0 ]]; then
  echo "Run with sudo/root."
  exit 1
fi

if ! command -v mergerfs >/dev/null 2>&1; then
  echo "mergerfs is not installed."
  echo "On Debian/Ubuntu: sudo apt install mergerfs"
  exit 1
fi

mkdir -p /etc/caretv
mkdir -p "$POOL"

if [[ ! -f "$CONFIG" ]]; then
  cat > "$CONFIG" <<'EOF'
# One existing filesystem mount point per line.
# Files remain on these disks exactly where they are.
#
# Example:
# /mnt/caretv-disk01
# /mnt/caretv-disk02
# /mnt/caretv-disk03
EOF
  echo "Created $CONFIG"
  echo "Add your disk mount points, one per line, then run this script again."
  exit 0
fi

mapfile -t BRANCHES < <(grep -vE '^[[:space:]]*(#|$)' "$CONFIG")

if [[ ${#BRANCHES[@]} -eq 0 ]]; then
  echo "No mergerfs branches are configured in $CONFIG"
  exit 1
fi

for branch in "${BRANCHES[@]}"; do
  if [[ ! -d "$branch" ]]; then
    echo "Missing branch directory: $branch"
    exit 1
  fi

  if ! mountpoint -q "$branch"; then
    echo "Branch is not mounted: $branch"
    echo "Refusing to continue so files cannot accidentally land on the root filesystem."
    exit 1
  fi
done

BRANCH_STRING="$(IFS=:; echo "${BRANCHES[*]}")"

if mountpoint -q "$POOL"; then
  umount "$POOL"
fi

# category.create=mfs = create new files on the branch with most free space.
# Existing files are visible immediately; nothing is moved.
mergerfs \
  -o defaults,allow_other,use_ino,cache.files=partial,dropcacheonclose=true,category.create=mfs \
  "$BRANCH_STRING" \
  "$POOL"

echo
echo "CareTV mergerfs pool is online at: $POOL"
echo "Existing files remain on their original physical filesystems."
echo "No copy/move/delete operation was performed."