main.tf

variable "nixos_version" {
  type        = string
  default     = "latest"
  description = "The NixOS version to use. Eg: 18.09"
}

variable "gcp_project_id" {
  type        = string
  default     = ""
  description = "The ID of the project in which the resource belongs. If it is not provided, the provider project is used."
}

variable "labels" {
  type        = map(string)
  default     = {}
  description = "A map of labels applied to this image."
}

variable "licenses" {
  type = list(string)

  default = [
    "https://www.googleapis.com/compute/v1/projects/vm-options/global/licenses/enable-vmx",
  ]

  description = "A list of license URIs to apply to this image. Changing this forces a new resource to be created."
}

# ---

locals {
  image_url = var.url_map[var.nixos_version]

  # Example: nixos-image-18-09-1228-a4c4cbb613c-x86-64-linux
  #
  # Remove a few things so that it matches the required regexp for image names
  #   (?:[a-z](?:[-a-z0-9]{0,61}[a-z0-9])?)
  image_name = replace(
    replace(basename(local.image_url), ".raw.tar.gz", ""),
    "/[._]+/",
    "-",
  )
}

resource "google_compute_image" "nixos" {
  name        = local.image_name
  description = "NixOS ${var.nixos_version}"
  family      = "nixos"
  project     = var.gcp_project_id
  labels      = var.labels
  licenses    = var.licenses

  raw_disk {
    source = local.image_url
  }
}

# ---

output "self_link" {
  description = "Link to the NixOS Compute Image"
  value       = google_compute_image.nixos.self_link
}