main.tf

locals {
  hostname      = var.hostname == "" ? "default" : var.hostname
  num_instances = length(var.static_ips) == 0 ? var.num_instances : length(var.static_ips)

  # local.static_ips is the same as var.static_ips with a dummy element appended
  # at the end of the list to work around "list does not have any elements so cannot
  # determine type" error when var.static_ips is empty
  static_ips = concat(var.static_ips, ["NOT_AN_IP"])
  project_id = length(regexall("/projects/([^/]*)", var.instance_template)) > 0 ? flatten(regexall("/projects/([^/]*)", var.instance_template))[0] : null

  # When no network or subnetwork has been defined, we want to use the settings from
  # the template instead.
  network_interface = length(format("%s%s", var.network, var.subnetwork)) == 0 ? [] : [1]
}

###############
# Data Sources
###############

data "google_compute_zones" "available" {
  project = local.project_id
  region  = var.region
}

#############
# Instances
#############

resource "google_compute_instance_from_template" "compute_instance" {
  provider            = google
  count               = local.num_instances
  name                = local.hostname //var.add_hostname_suffix ? format("%s%s%s", local.hostname, var.hostname_suffix_separator, format("%03d", count.index + 1)) : local.hostname
  project             = local.project_id
  zone                = var.zone == null ? data.google_compute_zones.available.names[count.index % length(data.google_compute_zones.available.names)] : var.zone
  deletion_protection = var.deletion_protection
  resource_policies   = var.resource_policies
  labels              = var.labels
  desired_status      = var.desired_status

  params {
    resource_manager_tags = var.resource_manager_tags
  }

  dynamic "network_interface" {
    for_each = local.network_interface

    content {
      network            = var.network
      subnetwork         = var.subnetwork
      subnetwork_project = var.subnetwork_project
      network_ip         = length(var.static_ips) == 0 ? "" : element(local.static_ips, count.index)
      dynamic "access_config" {
        for_each = var.access_config
        content {
          nat_ip       = access_config.value.nat_ip
          network_tier = access_config.value.network_tier
        }
      }

      dynamic "ipv6_access_config" {
        for_each = var.ipv6_access_config
        content {
          network_tier = ipv6_access_config.value.network_tier
        }
      }

      dynamic "alias_ip_range" {
        for_each = var.alias_ip_ranges
        content {
          ip_cidr_range         = alias_ip_range.value.ip_cidr_range
          subnetwork_range_name = alias_ip_range.value.subnetwork_range_name
        }
      }
    }
  }

 source_instance_template = var.instance_template
}

#########
# Locals
#########

locals {
  source_image         = "${var.source_image}"  //!= "" //? var.source_image : "debian-11-bullseye-v20240515"
  source_image_family  = "${var.source_image_family}" //!= "" ? var.source_image_family : "debian-11"
  source_image_project = "${var.source_image_project}" //!= "" ? var.source_image_project : "debian-cloud"

  boot_disk = [
    {
      source_image = var.source_image != "" ? format("${local.source_image_project}/${local.source_image}") : format("${local.source_image_project}/${local.source_image_family}")
      disk_size_gb = var.disk_size_gb
      disk_type    = var.disk_type
      disk_labels  = var.disk_labels
      auto_delete  = var.auto_delete
      boot         = "true"
    },
  ]

  all_disks = concat(local.boot_disk, var.additional_disks)

  # NOTE: Even if all the shielded_instance_config or confidential_instance_config
  # values are false, if the config block exists and an unsupported image is chosen,
  # the apply will fail so we use a single-value array with the default value to
  # initialize the block only if it is enabled.
  shielded_vm_configs = var.enable_shielded_vm ? [true] : []

  gpu_enabled            = var.gpu != null
  alias_ip_range_enabled = var.alias_ip_range != null
  on_host_maintenance = (
    var.preemptible || var.enable_confidential_vm || local.gpu_enabled || var.spot
    ? "TERMINATE"
    : var.on_host_maintenance
  )
  automatic_restart = (
    # must be false when preemptible or spot is true
    var.preemptible || var.spot ? false : var.automatic_restart
  )
  preemptible = (
    # must be true when preemtible or spot is true
    var.preemptible || var.spot ? true : false
  )
}

####################
# Instance Template
####################
resource "google_compute_instance_template" "tpl" {
  provider                = google-beta
  name_prefix             = "${var.name_prefix}"
  project                 = var.project_id
  machine_type            = var.machine_type
  labels                  = var.labels
  metadata                = var.metadata
  tags                    = var.tags
  can_ip_forward          = var.can_ip_forward
  metadata_startup_script = var.startup_script
  region                  = var.region
  min_cpu_platform        = var.min_cpu_platform
  resource_policies       = var.resource_policies
  dynamic "disk" {
    for_each = local.all_disks
    content {
      auto_delete     = lookup(disk.value, "auto_delete", null)
      boot            = lookup(disk.value, "boot", null)
      device_name     = lookup(disk.value, "device_name", null)
      disk_name       = lookup(disk.value, "disk_name", null)
      disk_size_gb    = lookup(disk.value, "disk_size_gb", lookup(disk.value, "disk_type", null) == "local-ssd" ? "375" : null)
      disk_type       = lookup(disk.value, "disk_type", null)
      interface       = lookup(disk.value, "interface", lookup(disk.value, "disk_type", null) == "local-ssd" ? "NVME" : null)
      mode            = lookup(disk.value, "mode", null)
      source          = lookup(disk.value, "source", null)
      source_image    = lookup(disk.value, "source_image", null)
      source_snapshot = lookup(disk.value, "source_snapshot", null)
      type            = lookup(disk.value, "disk_type", null) == "local-ssd" ? "SCRATCH" : "PERSISTENT"
      labels          = lookup(disk.value, "disk_labels", null)

      dynamic "disk_encryption_key" {
        for_each = compact([var.disk_encryption_key == null ? null : 1])
        content {
          kms_key_self_link = var.disk_encryption_key
        }
      }
    }
  }
  dynamic "service_account" {
    for_each = var.service_account == null ? [] : [var.service_account]
    content {
      email  = lookup(service_account.value, "email", null)
      scopes = lookup(service_account.value, "scopes", null)
    }
  }

  network_interface {
    network            = var.network
    subnetwork         = var.subnetwork
    subnetwork_project = var.subnetwork_project
    network_ip         = length(var.network_ip) > 0 ? var.network_ip : null
    nic_type           = var.nic_type
    stack_type         = var.stack_type
    dynamic "access_config" {
      for_each = var.access_config
      content {
        nat_ip       = access_config.value.nat_ip
        network_tier = access_config.value.network_tier
      }
    }
    dynamic "ipv6_access_config" {
      for_each = var.ipv6_access_config
      content {
        network_tier = ipv6_access_config.value.network_tier
      }
    }
    dynamic "alias_ip_range" {
      for_each = local.alias_ip_range_enabled ? [var.alias_ip_range] : []
      content {
        ip_cidr_range         = alias_ip_range.value.ip_cidr_range
        subnetwork_range_name = alias_ip_range.value.subnetwork_range_name
      }
    }
  }

  dynamic "network_interface" {
    for_each = var.additional_networks
    content {
      network            = network_interface.value.network
      subnetwork         = network_interface.value.subnetwork
      subnetwork_project = network_interface.value.subnetwork_project
      network_ip         = length(network_interface.value.network_ip) > 0 ? network_interface.value.network_ip : null
      nic_type           = network_interface.value.nic_type
      stack_type         = network_interface.value.stack_type
      queue_count        = network_interface.value.queue_count
      dynamic "access_config" {
        for_each = network_interface.value.access_config
        content {
          nat_ip       = access_config.value.nat_ip
          network_tier = access_config.value.network_tier
        }
      }
      dynamic "ipv6_access_config" {
        for_each = network_interface.value.ipv6_access_config
        content {
          network_tier = ipv6_access_config.value.network_tier
        }
      }
      dynamic "alias_ip_range" {
        for_each = network_interface.value.alias_ip_range
        content {
          ip_cidr_range         = alias_ip_range.value.ip_cidr_range
          subnetwork_range_name = alias_ip_range.value.subnetwork_range_name
        }
      }
    }
  }

  lifecycle {
    create_before_destroy = "true"
  }

  scheduling {
    automatic_restart           = local.automatic_restart
    instance_termination_action = var.spot ? var.spot_instance_termination_action : null
    maintenance_interval        = var.maintenance_interval
    on_host_maintenance         = local.on_host_maintenance
    preemptible                 = local.preemptible
    provisioning_model          = var.spot ? "SPOT" : null
  }

  advanced_machine_features {
    enable_nested_virtualization = var.enable_nested_virtualization
    threads_per_core             = var.threads_per_core
  }

  dynamic "shielded_instance_config" {
    for_each = local.shielded_vm_configs
    content {
      enable_secure_boot          = lookup(var.shielded_instance_config, "enable_secure_boot", shielded_instance_config.value)
      enable_vtpm                 = lookup(var.shielded_instance_config, "enable_vtpm", shielded_instance_config.value)
      enable_integrity_monitoring = lookup(var.shielded_instance_config, "enable_integrity_monitoring", shielded_instance_config.value)
    }
  }

  confidential_instance_config {
    enable_confidential_compute = var.enable_confidential_vm
  }

  network_performance_config {
    total_egress_bandwidth_tier = var.total_egress_bandwidth_tier
  }

  dynamic "guest_accelerator" {
    for_each = local.gpu_enabled ? [var.gpu] : []
    content {
      type  = guest_accelerator.value.type
      count = guest_accelerator.value.count
    }
  }
}