#!/usr/bin/env bash
# Boots a Das OS ISO in QEMU (KVM when available).
#
# Usage: scripts/run-qemu.sh [--bios] [--disk] [--serial] [path/to/image.iso]
#   --bios    boot with legacy BIOS instead of UEFI
#   --disk    attach out/qemu/disk.qcow2 (20 GB, created on first use) to test installing
#   --serial  no window: the serial console in this terminal (server ISO), Ctrl-A X quits
# Without a path the newest desktop ISO in out/iso is used (server ISO with --serial).
set -euo pipefail

root=$(cd "$(dirname "$0")/.." && pwd)
state=$root/out/qemu
firmware=uefi
disk=false
serial=false
iso=""

die() {
  echo "run-qemu: $*" >&2
  exit 1
}

for arg in "$@"; do
  case $arg in
    --bios) firmware=bios ;;
    --disk) disk=true ;;
    --serial) serial=true ;;
    -h | --help)
      sed -n '2,9s/^# \{0,1\}//p' "$0"
      exit 0
      ;;
    -*) die "unknown option: $arg" ;;
    *) iso=$arg ;;
  esac
done

if [[ -z $iso ]]; then
  pattern="dasos-[0-9]*.iso"
  [[ $serial == true ]] && pattern="dasos-server-*.iso"
  iso=$(ls -t "$root"/out/iso/$pattern 2>/dev/null | head -n 1) || true
fi
[[ -n $iso && -f $iso ]] || die "no ISO found, run 'make iso' first"

args=(
  -machine q35 -smp 4 -m 4096
  -device virtio-net-pci,netdev=net0 -netdev user,id=net0
  -cdrom "$iso" -boot order=d
)
if [[ $serial == true ]]; then
  # The guest's ttyS0 and the QEMU monitor share this terminal
  args+=(-nographic -serial mon:stdio)
else
  args+=(-device virtio-vga -display gtk,zoom-to-fit=on -device qemu-xhci -device usb-tablet)
fi

if [[ -w /dev/kvm ]]; then
  args+=(-accel kvm -cpu host)
else
  echo "run-qemu: /dev/kvm is not accessible, falling back to slow emulation" >&2
  args+=(-accel tcg -cpu max)
fi

mkdir -p "$state"

if [[ $firmware == uefi ]]; then
  code=""
  # Debian/Ubuntu/Mint, then Arch, then Fedora file names
  for candidate in /usr/share/OVMF/OVMF_CODE_4M.fd /usr/share/edk2/x64/OVMF_CODE.4m.fd /usr/share/edk2/ovmf/OVMF_CODE.fd; do
    [[ -f $candidate ]] && code=$candidate && break
  done
  [[ -n $code ]] || die "UEFI firmware (OVMF) not found, install the ovmf package or use --bios"
  vars_template=$(dirname "$code")/$(basename "$code" | sed 's/CODE/VARS/')
  [[ -f $state/OVMF_VARS.fd ]] || cp "$vars_template" "$state/OVMF_VARS.fd"
  args+=(
    -drive "if=pflash,format=raw,readonly=on,file=$code"
    -drive "if=pflash,format=raw,file=$state/OVMF_VARS.fd"
  )
fi

if [[ $disk == true ]]; then
  [[ -f $state/disk.qcow2 ]] || qemu-img create -f qcow2 "$state/disk.qcow2" 20G
  args+=(-drive "file=$state/disk.qcow2,if=virtio,format=qcow2")
fi

exec qemu-system-x86_64 "${args[@]}"