---@param instance Instance
---@return boolean
function is_q35(instance)
  return (instance.chipset == "q35" or string.find(instance.chipset, "pc-q35") == 0)
end

---@param instance Instance
---@param vm VM
---@return VM, string
function ensure_pci(instance, vm)
  if is_q35(instance) then
    local i82801b11 = vm:get_device_id("i82801b11-bridge")
    if i82801b11 == nil then
      i82801b11 = "i82801b11"
      vm:arg("-device", "i82801b11-bridge,id=" .. i82801b11 .. ",bus=" .. vm:get_next_bus("pcie"))
    end

    local pci_bridge = vm:get_device_id("pci-bridge")
    if pci_bridge == nil then
      pci_bridge = "pci-bridge"
      vm:arg("-device", "pci-bridge,chassis_nr=" .. vm:get_counter("chassis", 1) .. ",id=" .. pci_bridge .. ",bus=" .. i82801b11)
    end

    return vm, pci_bridge
  else
    error("No support for non-q35 instances")
  end
end

---@param instance Instance
---@param vm VM
---@param mem_path string
---@param size number
---@param id string
---@return VM
function add_shared_memory(instance, vm, mem_path, size, id)
  local pci
  vm, pci = ensure_pci(instance, vm)

  vm:arg("-object", "memory-backend-file,id=shmem-" .. id .. ",mem-path=" .. mem_path .. ",size=" .. size .. ",share=on")
  vm:arg("-device", "ivshmem-plain,memdev=shmem-" .. id .. ",bus=" .. pci .. ",addr=0x" .. string.format("%x", vm:get_counter("pci", 1)))

  return vm
end

vore:set_build_command(function(instance, vm)
  vm:arg("-rtc", "driftfix=slew")
  vm:arg("-no-hpet")
  vm:arg("-boot", "strict=on")

  if instance.kvm then
    vm:arg("-enable-kvm")
  end

  if instance.arch == "x86_64" or instance.arch == "i868" then
    vm:arg("-global", "kvm-pit.lost_tick_policy=discard")
  end

  --this disables the QEMU GUI
  vm:arg("-display", "none")

  vm:arg("-no-user-config")
  --vm:arg("-nodefaults")
  vm:arg("-no-shutdown")
  vm:arg("-m", tostring(instance.memory))

  local cpu = instance.cpu;
  vm:arg(
    "-smp",
    string.format(
      "%d,sockets=%d,dies=%d,cores=%d,threads=%d",
      cpu.amount,
      cpu.sockets,
      cpu.dies,
      cpu.cores,
      cpu.threads
    )
  )

  if instance.uefi.enabled and is_q35(instance) then
    -- OVMF will hang if S3 is not disabled
    -- disable S4 too, since libvirt does that 🤷
    -- https://bugs.archlinux.org/task/59465#comment172528
    vm:arg("-global", "ICH9-LPC.disable_s3=1")
    vm:arg("-global", "ICH9-LPC.disable_s4=1")
  end

  for idx, disk in ipairs(instance.disks) do
    vm = vore:add_disk(vm, instance, idx, disk)
  end

  if instance.uefi.enabled then
    vm:arg(
      "-drive", "if=pflash,format=raw,unit=0,file=" .. global.uefi.default.boot_code .. ",readonly=on",
      "-drive", "if=pflash,format=raw,unit=1,file=" .. vore:get_file("uefi/OVMF_VARS.fd", global.uefi.default.template)
    )
  end

  for _, vfio in ipairs(instance.vfio) do
    local def = "vfio-pci,host=" .. vfio.address
    if vfio.graphics then
      def = def .. ",x-vga=on"
    end

    if vfio.multifunction then
      def = def .. ",multifunction=on"
    end

    if vfio.graphics and vm:get_counter("disabled_display", 0) == 0 then
      vm:arg("-vga", "none")
    end

    vm:arg("-device", def)
  end

  if instance.looking_glass.enabled then
    vm = add_shared_memory(instance, vm, instance.looking_glass.mem_path, instance.looking_glass.buffer_size, "lg")
  end

  if instance.scream.enabled then
    vm = add_shared_memory(instance, vm, instance.scream.mem_path, instance.scream.buffer_size, "scream")
  end

  if instance.spice.enabled then
    vm:arg("-spice", "unix,addr=" .. instance.spice.socket_path .. ",disable-ticketing=on,seamless-migration=on")
  end

  if instance.jack.enabled then

  end

  if instance.pulse.enabled then
    vm:arg("-device", "intel-hda", "-device", "hda-duplex,audiodev=pa0")
    vm:arg("-audiodev", "pa,server=/run/user/1000/pulse/native,id=pa0")
  end

  vm:arg(
    "-machine",
    "q35,accel=kvm,usb=off,vmport=off,dump-guest-core=off,kernel_irqchip=on"
  )

  -- Pls update
  vm:arg(
    "-cpu",
    "host,hv-time,hv-relaxed,hv-vapic,hv-spinlocks=0x1fff,hv-vendor-id=whatever,kvm=off,+topoext"
  )

  return vm
end)

---
---@param type string
---@return fun(vm: VM, instance: Instance, idx: number, disk: Disk): VM
function virtio_scsi_disk_gen(type)
  -- see https://blog.christophersmart.com/2019/12/18/kvm-guests-with-emulated-ssd-and-nvme-drives/
  return function(vm, _, idx, disk)
    local scsi_pci = vm:get_device_id("virtio-scsi-pci")
    if scsi_pci == nil then
      scsi_pci = "scsi-pci"
      vm:arg("-device", "virtio-scsi-pci,id=" .. scsi_pci)
    end

    vm:arg(
      "-blockdev",
      tojson({
        ["driver"] = disk.disk_type,
        ["file"] = {
          ["driver"] = "host_device",
          ["filename"] = disk.path,
          ["aio"] = "native",
          ["discard"] = "unmap",
          ["cache"] = { ["direct"] = true, ["no-flush"] = false },
        },
        ["node-name"] = "format-" .. idx,
        ["read-only"] = false,
        ["cache"] = { ["direct"] = true, ["no-flush"] = false },
        ["discard"] = "unmap",
      })
    )

    local hd = "scsi-hd,drive=format-" .. idx .. ",bus=" .. scsi_pci .. ".0"
    if type == "ssd" then
      -- Having a rotation rate of 1 signals Windows it's an ssd
      hd = hd .. ",rotation_rate=1"
    end

    vm:arg("-device", hd)

    return vm
  end
end

---
---@param name string
---@param device_type string
---@return fun(vm: VM, instance: Instance, idx: number, disk: Disk): VM
function ide_disk_gen(name, device_type)
  return function(vm, _, _, disk)
    local drive_id = name .. vm:get_counter(name, 1)

    vm:arg("-drive", "file=" .. disk.path .. ",driver=" .. disk.disk_type .. ",if=none,id=" .. drive_id)
    vm:arg("-device", device_type .. ",drive=" .. drive_id .. ",bus=ide." .. vm:get_counter("ide", 0))

    return vm
  end
end

vore:register_disk_preset("ssd", "virtio based SSD (requires virtio drivers)", virtio_scsi_disk_gen("ssd"))
vore:register_disk_preset("hdd", "virtio based HDD (requires virtio drivers)", virtio_scsi_disk_gen("hdd"))

vore:register_disk_preset("iso", "IDE based CD", ide_disk_gen("iso", "ide-cd"))
vore:register_disk_preset("ide", "IDE based HDD  (not recommended, useful when missing virtio drivers)", ide_disk_gen("ide", "ide-hd"))

vore:register_disk_preset("nvme", "PCIe based NVMe drive", function(vm, _, _, disk)
  local nvme_id = vm:get_counter("nvme", 1)

  -- see https://blog.christophersmart.com/2019/12/18/kvm-guests-with-emulated-ssd-and-nvme-drives/
  vm:arg("-drive", "file=" .. disk.path .. ",driver=" .. disk.disk_type .. ",if=none,id=NVME" .. nvme_id)
  vm:arg("-device", "nvme,drive=NVME" .. nvme_id .. ",serial=nvme-" .. nvme_id)

  return vm
end)