#!/usr/bin/env bash
# Bootstrap a one-shot GRUB entry for BGP.Exchange automated reinstall.
# Usage: curl -fsSL https://install.bgp.exchange/ | sudo bash
#
# Bare-metal / VM from ISO (Debian 13): https://repo.bgp.exchange/iso/bgpe-debian13-amd64-netinst.iso
# See https://repo.bgp.exchange/iso/debian13/README.md
set -euo pipefail

if [[ "${EUID:-$(id -u)}" -ne 0 ]]; then
  echo "Run as root (e.g. curl -fsSL https://install.bgp.exchange/ | sudo bash)" >&2
  exit 1
fi

if ! command -v wget >/dev/null 2>&1; then
  echo "wget is required" >&2
  exit 1
fi

detect_deb_release() {
  local id codename ver
  if [[ -r /etc/os-release ]]; then
    # shellcheck disable=SC1091
    source /etc/os-release
    case "${VERSION_ID:-}" in
      12|12.*) echo deb12; return ;;
      13|13.*) echo deb13; return ;;
    esac
    codename="${VERSION_CODENAME:-}"
  fi
  if [[ -z "${codename:-}" && -r /etc/debian_version ]]; then
    ver="$(sed 's/\/.*//' /etc/debian_version)"
    case "$ver" in
      12|12.*) echo deb12; return ;;
      13|13.*) echo deb13; return ;;
      bookworm) echo deb12; return ;;
      trixie) echo deb13; return ;;
    esac
  fi
  case "${codename:-}" in
    bookworm) echo deb12 ;;
    trixie) echo deb13 ;;
    *)
      echo "ERROR: unsupported Debian release (need 12/bookworm or 13/trixie)" >&2
      exit 1
      ;;
  esac
}

is_efi() {
  [[ -d /sys/firmware/efi ]]
}

# stdin is the script when piped from curl; read prompts from the terminal.
read_tty() {
  if [[ -r /dev/tty ]]; then
    read -r -p "$1" "$2" </dev/tty
  else
    read -r -p "$1" "$2"
  fi
}

read_tty "Enter Hostname: " hostname
read_tty "Enter IP: " ip
read_tty "Enter Subnet: " subnet
read_tty "Enter Gateway: " gateway

for var in hostname ip subnet gateway; do
  if [[ -z "${!var}" ]]; then
    echo "ERROR: ${var} is required" >&2
    exit 1
  fi
done

deb_release="$(detect_deb_release)"
repo_base="https://repo.bgp.exchange/${deb_release}"
preseed_base="https://repo.bgp.exchange/preseed"

if is_efi; then
  preseed_file="${hostname}.efi.txt"
else
  preseed_file="${hostname}.txt"
fi
preseed_url="${preseed_base}/${preseed_file}"

echo "Debian netboot: ${repo_base}/"
echo "Preseed: ${preseed_url}"

boot_dir="/boot/bgpe"
mkdir -p "$boot_dir"
cd "$boot_dir"
rm -f initrd.gz vmlinuz initrd.gz.* vmlinuz.*
wget -q --show-progress -O initrd.gz "${repo_base}/initrd.gz"
wget -q --show-progress -O vmlinuz "${repo_base}/vmlinuz"

for f in initrd.gz vmlinuz; do
  if [[ ! -s "${boot_dir}/${f}" ]]; then
    echo "ERROR: ${boot_dir}/${f} missing or empty after download" >&2
    exit 1
  fi
done

# GRUB paths are relative to the partition containing /boot. When /boot is its own
# filesystem, that partition's root is /boot — use /bgpe/..., not /boot/bgpe/...
if mountpoint -q /boot && [[ "$(stat -c '%d' /)" -ne "$(stat -c '%d' /boot)" ]]; then
  grub_kernel="/bgpe/vmlinuz"
  grub_initrd="/bgpe/initrd.gz"
else
  grub_kernel="/boot/bgpe/vmlinuz"
  grub_initrd="/boot/bgpe/initrd.gz"
fi
echo "GRUB paths: ${grub_kernel}, ${grub_initrd}"

cat > /etc/grub.d/50_bgpe <<GRUBEOF
#!/bin/sh
exec tail -n +3 \$0

menuentry "BGP.Exchange Reinstallation" {
    set background_color=black
    linux    ${grub_kernel} auto=true priority=critical vga=788 timezone=Australia/Melbourne UTC=yes netcfg/disable_autoconfig=true netcfg/get_ipaddress=${ip} netcfg/get_netmask=${subnet} netcfg/get_gateway=${gateway} netcfg/get_nameservers=8.8.8.8 netcfg/confirm_static=true preseed/url=${preseed_url}
    initrd   ${grub_initrd}
}
GRUBEOF

chmod +x /etc/grub.d/50_bgpe
update-grub
grub-reboot "BGP.Exchange Reinstallation"
reboot