#!/bin/sh
set -eu

KARLDNS_BASE_URL="${KARLDNS_BASE_URL:-https://karldns.de}"
KARLDNS_INTERVAL_MINUTES="${KARLDNS_INTERVAL_MINUTES:-5}"
KARLDNS_INSTALL_MODE="${KARLDNS_INSTALL_MODE:-auto}"
KARLDNS_UPDATE_URL="${KARLDNS_UPDATE_URL:-}"
KARLDNS_HOSTNAME="${KARLDNS_HOSTNAME:-}"
KARLDNS_MANAGEMENT_URL="${KARLDNS_MANAGEMENT_URL:-}"
KARLDNS_RAW_BASE_URL="${KARLDNS_RAW_BASE_URL:-https://raw.githubusercontent.com/StasonJatham/karldns.de/main/scripts}"
KARLDNS_IPV4="${KARLDNS_IPV4:-auto}"
KARLDNS_IPV6="${KARLDNS_IPV6:-auto}"
KARLDNS_SKIP_CRON="${KARLDNS_SKIP_CRON:-0}"
KARLDNS_SKIP_FIRST_UPDATE="${KARLDNS_SKIP_FIRST_UPDATE:-0}"

usage() {
  cat <<'EOF'
KarlDNS Linux installer

Usage:
  install-linux.sh [options]

Options:
  --base-url URL       KarlDNS server URL. Default: https://karldns.de
  --raw-base-url URL   Updater script download URL
  --every MINUTES      Update interval, 1-60. Default: 5
  --mode MODE          auto, system, or user. Default: auto
  --update-url URL     Existing private update URL
  --hostname NAME      Hostname to show after install
  --dashboard-url URL  Private dashboard URL to show after install
  --ipv4 VALUE         auto, off, or a static IPv4. Default: auto
  --ipv6 VALUE         auto, off, or a static IPv6. Default: auto
  --no-cron            Install files only, do not configure cron
  --no-run             Do not run the first update after install
  -h, --help           Show this help

Examples:
  curl -fsSL https://raw.githubusercontent.com/StasonJatham/karldns.de/main/scripts/install-linux.sh | sudo sh
  curl -fsSL https://raw.githubusercontent.com/StasonJatham/karldns.de/main/scripts/install-linux.sh | sh -s -- --mode user
EOF
}

while [ "$#" -gt 0 ]; do
  case "$1" in
    --base-url) KARLDNS_BASE_URL="${2:?missing value for --base-url}"; shift 2 ;;
    --raw-base-url) KARLDNS_RAW_BASE_URL="${2:?missing value for --raw-base-url}"; shift 2 ;;
    --every) KARLDNS_INTERVAL_MINUTES="${2:?missing value for --every}"; shift 2 ;;
    --mode) KARLDNS_INSTALL_MODE="${2:?missing value for --mode}"; shift 2 ;;
    --update-url) KARLDNS_UPDATE_URL="${2:?missing value for --update-url}"; shift 2 ;;
    --hostname) KARLDNS_HOSTNAME="${2:?missing value for --hostname}"; shift 2 ;;
    --dashboard-url|--management-url) KARLDNS_MANAGEMENT_URL="${2:?missing value for --dashboard-url}"; shift 2 ;;
    --ipv4) KARLDNS_IPV4="${2:?missing value for --ipv4}"; shift 2 ;;
    --ipv6) KARLDNS_IPV6="${2:?missing value for --ipv6}"; shift 2 ;;
    --no-cron) KARLDNS_SKIP_CRON=1; shift ;;
    --no-run) KARLDNS_SKIP_FIRST_UPDATE=1; shift ;;
    -h|--help) usage; exit 0 ;;
    *) echo "KarlDNS installer: unknown option: $1" >&2; usage >&2; exit 1 ;;
  esac
done

need() {
  if ! command -v "$1" >/dev/null 2>&1; then
    echo "KarlDNS installer: missing required command: $1" >&2
    exit 1
  fi
}

json_field() {
  key="$1"
  if command -v python3 >/dev/null 2>&1; then
    python3 -c 'import json,sys; print(json.load(sys.stdin).get(sys.argv[1], ""))' "$key"
  else
    sed -n "s/.*\"$key\"[[:space:]]*:[[:space:]]*\"\\([^\"]*\\)\".*/\\1/p" | head -n 1
  fi
}

quote_sh() {
  printf "%s" "$1" | sed "s/'/'\\\\''/g; 1s/^/'/; \$s/\$/'/"
}

download_updater() {
  target_path="$1"
  tmp_path="$(mktemp)"
  if ! "$curl_bin" -fsS "$KARLDNS_RAW_BASE_URL/karldns-update.sh" -o "$tmp_path"; then
    rm -f "$tmp_path"
    exit 1
  fi
  chmod 755 "$tmp_path"
  mv "$tmp_path" "$target_path"
}

cron_schedule() {
  if [ "$KARLDNS_INTERVAL_MINUTES" = "60" ]; then
    printf '0 * * * *'
  else
    printf '*/%s * * * *' "$KARLDNS_INTERVAL_MINUTES"
  fi
}

update_crontab() {
  cron_file="$1"
  schedule="$2"
  command="$3"
  marker_start="# karldns-update start"
  marker_end="# karldns-update end"
  awk -v start="$marker_start" -v end="$marker_end" '
    $0 == start {skip = 1; next}
    $0 == end {skip = 0; next}
    skip != 1 {print}
  ' "$cron_file" 2>/dev/null
  printf '%s\n' "$marker_start"
  printf '%s %s\n' "$schedule" "$command"
  printf '%s\n' "$marker_end"
}

write_config() {
  config_file="$1"
  cache_file="$2"
  lock_file="$3"
  umask 077
  {
    printf 'KARLDNS_BASE_URL=%s\n' "$(quote_sh "$KARLDNS_BASE_URL")"
    printf 'KARLDNS_UPDATE_URL=%s\n' "$(quote_sh "$KARLDNS_UPDATE_URL")"
    printf 'KARLDNS_HOSTNAME=%s\n' "$(quote_sh "$KARLDNS_HOSTNAME")"
    printf 'KARLDNS_MANAGEMENT_URL=%s\n' "$(quote_sh "$KARLDNS_MANAGEMENT_URL")"
    printf 'KARLDNS_CACHE_FILE=%s\n' "$(quote_sh "$cache_file")"
    printf 'KARLDNS_LOCK_FILE=%s\n' "$(quote_sh "$lock_file")"
    printf 'KARLDNS_IPV4=%s\n' "$(quote_sh "$KARLDNS_IPV4")"
    printf 'KARLDNS_IPV6=%s\n' "$(quote_sh "$KARLDNS_IPV6")"
  } > "$config_file"
  chmod 600 "$config_file"
}

install_user() {
  config_dir="${XDG_CONFIG_HOME:-$HOME/.config}/karldns"
  cache_dir="${XDG_CACHE_HOME:-$HOME/.cache}/karldns"
  bin_dir="${HOME}/.local/bin"
  config_file="${config_dir}/updater.env"
  updater_path="${bin_dir}/karldns-update"
  cron_file="$(mktemp)"
  mkdir -p "$config_dir" "$cache_dir" "$bin_dir"

  download_updater "$updater_path"
  chmod 700 "$updater_path"

  write_config "$config_file" "$cache_dir/last-ip" "$cache_dir/updater.lock"

  if [ "$KARLDNS_SKIP_CRON" = "0" ]; then
    need crontab
    crontab -l > "$cron_file" 2>/dev/null || true
    update_crontab "$cron_file" "$(cron_schedule)" \
      "KARLDNS_CONFIG=$(quote_sh "$config_file") $(quote_sh "$updater_path") >/dev/null 2>&1" > "$cron_file.new"
    mv "$cron_file.new" "$cron_file"
    crontab "$cron_file"
    rm -f "$cron_file"
  fi
}

install_system() {
  config_dir="/etc/karldns"
  cache_dir="/var/cache/karldns"
  config_file="${config_dir}/updater.env"
  updater_path="/usr/local/bin/karldns-update"
  cron_file="/etc/cron.d/karldns-updater"
  mkdir -p "$config_dir" "$cache_dir"

  download_updater "$updater_path"

  write_config "$config_file" "$cache_dir/last-ip" "/run/karldns-updater.lock"

  if [ "$KARLDNS_SKIP_CRON" = "0" ]; then
    cat > "$cron_file" <<EOF
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
$(cron_schedule) root KARLDNS_CONFIG=$(quote_sh "$config_file") $(quote_sh "$updater_path") >/dev/null 2>&1
EOF
    chmod 644 "$cron_file"
  fi
}

need curl
curl_bin="$(command -v curl)"

case "$KARLDNS_INTERVAL_MINUTES" in
  ''|*[!0-9]*) echo "KARLDNS_INTERVAL_MINUTES must be a positive integer" >&2; exit 1 ;;
esac
if [ "$KARLDNS_INTERVAL_MINUTES" -lt 1 ] || [ "$KARLDNS_INTERVAL_MINUTES" -gt 60 ]; then
  echo "KARLDNS_INTERVAL_MINUTES must be between 1 and 60" >&2
  exit 1
fi

case "$KARLDNS_INSTALL_MODE" in
  auto)
    if [ "$(id -u)" -eq 0 ]; then
      KARLDNS_INSTALL_MODE="system"
    else
      KARLDNS_INSTALL_MODE="user"
    fi
    ;;
  user|system) ;;
  *) echo "KARLDNS_INSTALL_MODE must be auto, user, or system" >&2; exit 1 ;;
esac

if [ "$KARLDNS_INSTALL_MODE" = "system" ] && [ "$(id -u)" -ne 0 ]; then
  echo "System install needs root. Re-run with sudo or use --mode user." >&2
  exit 1
fi

if [ -z "$KARLDNS_UPDATE_URL" ]; then
  echo "KarlDNS: creating a new hostname at $KARLDNS_BASE_URL ..."
  response="$("$curl_bin" -fsS --max-time 30 -H 'content-type: application/json' -d '{}' "$KARLDNS_BASE_URL/api/v1/hostnames/magic")"
  KARLDNS_UPDATE_URL="$(printf '%s' "$response" | json_field update_url)"
  KARLDNS_HOSTNAME="$(printf '%s' "$response" | json_field hostname)"
  KARLDNS_MANAGEMENT_URL="$(printf '%s' "$response" | json_field management_url)"
fi

if [ -z "$KARLDNS_UPDATE_URL" ]; then
  echo "KarlDNS installer: could not create an update URL" >&2
  exit 1
fi
case "$KARLDNS_UPDATE_URL" in
  *"<ipaddr>"*|*"<ip6addr>"*) KARLDNS_UPDATE_URL="${KARLDNS_UPDATE_URL%%\?*}" ;;
esac

if [ "$KARLDNS_INSTALL_MODE" = "system" ]; then
  install_system
else
  install_user
fi

echo "KarlDNS installed."
echo "Hostname: ${KARLDNS_HOSTNAME:-already configured}"
echo "Dashboard: ${KARLDNS_MANAGEMENT_URL:-use your existing private dashboard}"
echo "Mode: $KARLDNS_INSTALL_MODE"
if [ "$KARLDNS_SKIP_CRON" = "0" ]; then
  echo "Interval: every $KARLDNS_INTERVAL_MINUTES minutes"
else
  echo "Cron: skipped"
fi
if [ "$KARLDNS_SKIP_FIRST_UPDATE" = "0" ]; then
  echo "Running first update now..."
  if [ "$KARLDNS_INSTALL_MODE" = "system" ]; then
    KARLDNS_CONFIG=/etc/karldns/updater.env /usr/local/bin/karldns-update
  else
    KARLDNS_CONFIG="${XDG_CONFIG_HOME:-$HOME/.config}/karldns/updater.env" "$HOME/.local/bin/karldns-update"
  fi
fi