#!/bin/bash

set -euo pipefail
shopt -s lastpipe

UID_MAP="/etc/jimlab/uid.map"
SUBID_MAP="/etc/jimlab/subid.map"
DEFAULT_SUBID_SIZE=4096

if [[ ! -f "$UID_MAP" ]]; then
  echo "❌ Error: $UID_MAP not found."
  exit 1
fi

touch "$SUBID_MAP"

# Return true if two ranges [start1, end1) and [start2, end2) overlap
ranges_overlap() {
  local start1=$1
  local size1=$2
  local start2=$3
  local size2=$4

  [[ -z "$start1" || -z "$size1" || -z "$start2" || -z "$size2" ]] && return 1
  [[ ! "$start1" =~ ^[0-9]+$ || ! "$size1" =~ ^[0-9]+$ || ! "$start2" =~ ^[0-9]+$ || ! "$size2" =~ ^[0-9]+$ ]] && return 1

  local end1=$((start1 + size1))
  local end2=$((start2 + size2))

  [[ $start1 -lt $end2 && $start2 -lt $end1 ]]
}

# Get next available subid base
get_next_subid_base() {
  local max=100000
  grep -v '^\s*$' "$SUBID_MAP" | while IFS=: read -r _ base size; do
    base=$(echo "$base" | xargs)
    size=$(echo "$size" | xargs)
    [[ "$base" =~ ^[0-9]+$ && "$size" =~ ^[0-9]+$ ]] || continue
    local end=$((base + size))
    (( end > max )) && max=$end
  done
  echo "$max"
}

# Warn if overlapping any prior block
check_overlap() {
  local new_start=$1
  local new_size=$2
  grep -v '^\s*$' "$SUBID_MAP" | while IFS=: read -r user base size; do
    if ranges_overlap "$new_start" "$new_size" "$base" "$size"; then
      echo "⚠️  Warning: new block $new_start:$new_size overlaps with $user:$base:$size" >&2
    fi
  done
}

grep -v '^\s*$' "$UID_MAP" | while IFS=: read -r service uid; do
  service=$(echo "$service" | xargs)
  uid=$(echo "$uid" | xargs)
  home="/var/lib/$service"

  [[ -z "$service" || -z "$uid" || "$service" == \#* ]] && continue

  echo "▶️  Processing $service (UID=$uid, HOME=$home)"

  # Create group if missing
  if ! getent group "$service" > /dev/null; then
    echo "  ➕ Creating group $service with GID $uid"
    groupadd --system --gid "$uid" "$service"
  fi

  # Create or fix user
  if ! id "$service" &>/dev/null; then
    echo "  ➕ Creating user $service with UID $uid and home $home"
    useradd --system --uid "$uid" --gid "$uid" --home-dir "$home" --create-home --shell /sbin/nologin "$service"
  else
    current_home=$(getent passwd "$service" | cut -d: -f6)
    if [[ "$current_home" != "$home" ]]; then
      echo "  🛠  Updating home dir for $service → $home"
      usermod -d "$home" "$service"
      mkdir -p "$home"
      chown "$service:$service" "$home"
    fi
  fi

  # Enable lingering
  if ! loginctl show-user "$uid" &>/dev/null || ! loginctl show-user "$uid" | grep -q "Linger=yes"; then
    echo "  🔄 Enabling lingering for $service"
    loginctl enable-linger "$service"
  fi

  # Subuid/subgid mapping
  if ! grep -q "^$service:" "$SUBID_MAP"; then
    next_base=$(get_next_subid_base)
    check_overlap "$next_base" "$DEFAULT_SUBID_SIZE"
    echo "  📦 Assigning subid range: $service:$next_base:$DEFAULT_SUBID_SIZE"
    echo "$service:$next_base:$DEFAULT_SUBID_SIZE" >> "$SUBID_MAP"
  fi

  # Sync to /etc/subuid and /etc/subgid
  map_line=$(grep "^$service:" "$SUBID_MAP" | head -n1)
  for file in /etc/subuid /etc/subgid; do
    if ! grep -q "^$service:" "$file"; then
      echo "$map_line" | sudo tee -a "$file" >/dev/null
    elif ! grep -q "^$map_line\$" "$file"; then
      echo "⚠️  Mismatch in $file for $service. Check manually!" >&2
    fi
  done

done