#!/usr/bin/env bash
set -euo pipefail

script_dir="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"
if [[ -n "${VM_IMAGE_HELPER:-}" ]]; then
  image_downloader="$VM_IMAGE_HELPER"
elif [[ -x "${script_dir}/vm-images/download-images.sh" ]]; then
  image_downloader="${script_dir}/vm-images/download-images.sh"
else
  image_downloader="${script_dir}/../vm-images/download-images.sh"
fi
uses_shared_base_image=false
if [[ -n "${FEDORA_VM_BASE_IMAGE:-}" ]]; then
  base_image="$FEDORA_VM_BASE_IMAGE"
else
  [[ -x "$image_downloader" ]] || { printf 'Error: shared image helper is unavailable: %s\n' "$image_downloader" >&2; exit 1; }
  base_image="$("$image_downloader" --print-path fedora44)"
  uses_shared_base_image=true
fi
state_dir="${FEDORA_VM_STATE_DIR:-${script_dir}/.vm/fedora44}"
disk_image="${FEDORA_VM_DISK_IMAGE:-${state_dir}/disk.qcow2}"
seed_image="${FEDORA_VM_SEED_IMAGE:-$(dirname -- "$disk_image")/seed.iso}"
disk_size="${FEDORA_VM_DISK_SIZE:-20G}"
memory="${FEDORA_VM_MEMORY:-8G}"
cpus="${FEDORA_VM_CPUS:-8}"
ssh_port="${FEDORA_VM_SSH_PORT:-2224}"
uefi_code="${FEDORA_VM_UEFI_CODE:-/usr/share/OVMF/OVMF_CODE_4M.fd}"
uefi_vars_template="${FEDORA_VM_UEFI_VARS:-/usr/share/OVMF/OVMF_VARS_4M.fd}"
uefi_vars="${state_dir}/OVMF_VARS_4M.fd"
pid_file="${state_dir}/qemu.pid"
log_file="${state_dir}/console.log"
daemonize=false
extra_args=()

usage() {
  cat <<EOF
Usage: $(basename "$0") [--daemon] [-- QEMU_ARGUMENT ...]

Start a Fedora 44 Cloud Base virtual machine. The launcher obtains a missing
base image through the shared image helper and creates a writable overlay
under .vm/fedora44/, leaving the base image unchanged.

Options:
  --daemon  Run in the background while keeping the graphical window
  -h, --help  Show this help

Environment variables:
  FEDORA_VM_MEMORY         Guest memory (default: 8G)
  FEDORA_VM_CPUS           Virtual CPU count (default: 8)
  FEDORA_VM_SSH_PORT       Host port forwarded to guest SSH (default: 2224)
  FEDORA_VM_BASE_IMAGE     Base qcow2 image path (default: resolved by shared image helper)
  FEDORA_VM_SEED_IMAGE     cloud-init seed ISO path (default: alongside the VM disk)
  FEDORA_VM_STATE_DIR      Runtime state directory (default: .vm/fedora44)
  FEDORA_VM_DISK_IMAGE     Writable overlay path
  FEDORA_VM_DISK_SIZE      New overlay virtual capacity (default: 20G)
  FEDORA_VM_UEFI_CODE      OVMF read-only firmware path
  FEDORA_VM_UEFI_VARS      OVMF variable-store template path
EOF
}

while (($#)); do
  case "$1" in
    --daemon) daemonize=true; shift ;;
    -h|--help) usage; exit 0 ;;
    --) shift; extra_args+=("$@"); break ;;
    *) printf 'Error: unknown option: %s\n' "$1" >&2; usage >&2; exit 2 ;;
  esac
done

for command_name in qemu-system-x86_64 qemu-img; do
  if ! command -v "$command_name" >/dev/null 2>&1; then
    printf 'Error: %s is not installed.\n' "$command_name" >&2
    exit 1
  fi
done

if [[ ! -f "$base_image" ]]; then
  if [[ "$uses_shared_base_image" == true ]]; then
    "$image_downloader" fedora44
  else
    printf 'Error: Fedora base image was not found: %s\n' "$base_image" >&2
    exit 1
  fi
fi
[[ -f "$base_image" ]] || { printf 'Error: downloader did not create: %s\n' "$base_image" >&2; exit 1; }
for firmware_file in "$uefi_code" "$uefi_vars_template"; do
  [[ -f "$firmware_file" ]] || { printf 'Error: required UEFI firmware was not found: %s\n' "$firmware_file" >&2; exit 1; }
done

if [[ ! -f "$seed_image" ]]; then
  seed_builder="${script_dir}/seediso/fedora44/build-seed.sh"
  if [[ ! -x "$seed_builder" ]]; then
    printf 'Error: seed image is missing and builder is unavailable: %s\n' "$seed_builder" >&2
    exit 1
  fi
  printf 'Seed image not found; building %s...\n' "$seed_image"
  "$seed_builder" "$seed_image"
fi

mkdir -p "$state_dir"
[[ -f "$uefi_vars" ]] || cp -- "$uefi_vars_template" "$uefi_vars"

if [[ -f "$pid_file" ]]; then
  old_pid="$(<"$pid_file")"
  if [[ "$old_pid" =~ ^[0-9]+$ ]] && kill -0 "$old_pid" 2>/dev/null; then
    printf 'Error: the Fedora virtual machine is already running (PID %s).\n' "$old_pid" >&2
    exit 1
  fi
  rm -f "$pid_file"
fi

if [[ ! -f "$disk_image" ]]; then
  qemu-img create -q -f qcow2 -F qcow2 -b "$base_image" "$disk_image" "$disk_size"
  printf 'Created writable disk overlay: %s\n' "$disk_image"
fi

qemu_args=(
  -name fedora44
  -machine q35
  -display gtk
  -m "$memory"
  -smp "$cpus"
  -drive "if=pflash,format=raw,readonly=on,file=${uefi_code}"
  -drive "if=pflash,format=raw,file=${uefi_vars}"
  -drive "file=${disk_image},if=virtio,format=qcow2"
  -drive "file=${seed_image},media=cdrom,readonly=on"
  -nic "user,model=virtio-net-pci,hostfwd=tcp::${ssh_port}-:22"
)

if [[ -r /dev/kvm && -w /dev/kvm ]]; then
  qemu_args+=(-enable-kvm -cpu host)
  accelerator=KVM
else
  qemu_args+=(-accel tcg -cpu max)
  accelerator=TCG
fi

printf 'Starting Fedora 44 with %s acceleration; SSH is forwarded to localhost:%s.\n' \
  "$accelerator" "$ssh_port"

if [[ "$daemonize" == true ]]; then
  : >"$log_file"
  qemu_args+=(
    -serial "file:${log_file}"
    -monitor none
    -daemonize
    -pidfile "$pid_file"
  )
  qemu-system-x86_64 "${qemu_args[@]}" "${extra_args[@]}"
  printf 'VM started (PID %s); console log: %s\n' "$(<"$pid_file")" "$log_file"
else
  exec qemu-system-x86_64 "${qemu_args[@]}" "${extra_args[@]}"
fi