# Discrete DNS records for each controller's private IPv4 for etcd usage
resource "azurerm_dns_a_record" "etcds" {
  count               = var.controller_count
  resource_group_name = var.dns_zone_group

  # DNS Zone name where record should be created
  zone_name = var.dns_zone

  # DNS record
  name = format("%s-etcd%d", var.cluster_name, count.index)
  ttl  = 300

  # private IPv4 address for etcd
  records = [azurerm_network_interface.controllers.*.private_ip_address[count.index]]
}

locals {
  # Container Linux derivative
  # flatcar-stable -> Flatcar Linux Stable
  channel      = split("-", var.os_image)[1]
  offer_suffix = var.arch == "arm64" ? "corevm" : "free"
  urn          = var.arch == "arm64" ? local.channel : "${local.channel}-gen2"
}

# Controller availability set to spread controllers
resource "azurerm_availability_set" "controllers" {
  resource_group_name = azurerm_resource_group.cluster.name

  name                         = "${var.cluster_name}-controllers"
  location                     = var.region
  platform_fault_domain_count  = 2
  platform_update_domain_count = 4
  managed                      = true
}

# Controller instances
resource "azurerm_linux_virtual_machine" "controllers" {
  count               = var.controller_count
  resource_group_name = azurerm_resource_group.cluster.name

  name                = "${var.cluster_name}-controller-${count.index}"
  location            = var.region
  availability_set_id = azurerm_availability_set.controllers.id

  size        = var.controller_type
  custom_data = base64encode(data.ct_config.controllers.*.rendered[count.index])

  # storage
  os_disk {
    name                 = "${var.cluster_name}-controller-${count.index}"
    caching              = "None"
    disk_size_gb         = var.disk_size
    storage_account_type = "Premium_LRS"
  }

  # Flatcar Container Linux
  source_image_reference {
    publisher = "kinvolk"
    offer     = "flatcar-container-linux-${local.offer_suffix}"
    sku       = local.urn
    version   = "latest"
  }

  dynamic "plan" {
    for_each = var.arch == "arm64" ? [] : [1]
    content {
      publisher = "kinvolk"
      product   = "flatcar-container-linux-${local.offer_suffix}"
      name      = local.urn
    }
  }

  # network
  network_interface_ids = [
    azurerm_network_interface.controllers.*.id[count.index]
  ]

  # Azure requires setting admin_ssh_key, though Ignition custom_data handles it too
  admin_username = "core"
  admin_ssh_key {
    username   = "core"
    public_key = var.ssh_authorized_key
  }

  lifecycle {
    ignore_changes = [
      os_disk,
      custom_data,
    ]
  }
}

# Controller public IPv4 addresses
resource "azurerm_public_ip" "controllers" {
  count               = var.controller_count
  resource_group_name = azurerm_resource_group.cluster.name

  name              = "${var.cluster_name}-controller-${count.index}"
  location          = azurerm_resource_group.cluster.location
  sku               = "Standard"
  allocation_method = "Static"
}

# Controller NICs with public and private IPv4
resource "azurerm_network_interface" "controllers" {
  count               = var.controller_count
  resource_group_name = azurerm_resource_group.cluster.name

  name     = "${var.cluster_name}-controller-${count.index}"
  location = azurerm_resource_group.cluster.location

  ip_configuration {
    name                          = "ip0"
    subnet_id                     = azurerm_subnet.controller.id
    private_ip_address_allocation = "Dynamic"
    # instance public IPv4
    public_ip_address_id = azurerm_public_ip.controllers.*.id[count.index]
  }
}

# Associate controller network interface with controller security group
resource "azurerm_network_interface_security_group_association" "controllers" {
  count = var.controller_count

  network_interface_id      = azurerm_network_interface.controllers[count.index].id
  network_security_group_id = azurerm_network_security_group.controller.id
}

# Associate controller network interface with controller backend address pool
resource "azurerm_network_interface_backend_address_pool_association" "controllers" {
  count = var.controller_count

  network_interface_id    = azurerm_network_interface.controllers[count.index].id
  ip_configuration_name   = "ip0"
  backend_address_pool_id = azurerm_lb_backend_address_pool.controller.id
}

# Flatcar Linux controllers
data "ct_config" "controllers" {
  count = var.controller_count
  content = templatefile("${path.module}/butane/controller.yaml", {
    # Cannot use cyclic dependencies on controllers or their DNS records
    etcd_name   = "etcd${count.index}"
    etcd_domain = "${var.cluster_name}-etcd${count.index}.${var.dns_zone}"
    # etcd0=https://cluster-etcd0.example.com,etcd1=https://cluster-etcd1.example.com,...
    etcd_initial_cluster = join(",", [
      for i in range(var.controller_count) : "etcd${i}=https://${var.cluster_name}-etcd${i}.${var.dns_zone}:2380"
    ])
    kubeconfig             = indent(10, module.bootstrap.kubeconfig-kubelet)
    ssh_authorized_key     = var.ssh_authorized_key
    cluster_dns_service_ip = cidrhost(var.service_cidr, 10)
    cluster_domain_suffix  = var.cluster_domain_suffix
  })
  strict   = true
  snippets = var.controller_snippets
}