terraform {
  backend "http" {
  }

  required_providers {
    google = {
      source  = "hashicorp/google"
      version = "4.3.0"
    }
  }
}

provider "google" {
  credentials = file("./gcp-sa.json")
  project     = var.project_id
  region      = var.region
}

data "google_project" "project" {
  provider   = google
  project_id = var.project_id
}

### Reserve Static IP
resource "google_compute_global_address" "static_ip" {
  provider = google
  project  = var.project_id
  name     = "gke-frontend"
}

### Create Network
resource "google_compute_network" "vpc_network" {
  provider                = google
  project                 = var.project_id
  name                    = var.vpc_network_name
  auto_create_subnetworks = false
  mtu                     = 1460
  routing_mode            = "GLOBAL"
}

### Create Subnetwork
resource "google_compute_subnetwork" "vpc_subnetwork" {
  provider      = google
  project       = var.project_id
  name          = var.vpc_subnetwork_name
  ip_cidr_range = "192.168.100.0/24"
  region        = var.region
  network       = google_compute_network.vpc_network.id
  secondary_ip_range {
    range_name    = "pods"
    ip_cidr_range = "10.0.0.0/14"
  }
  secondary_ip_range {
    range_name    = "services"
    ip_cidr_range = "10.4.0.0/19"
  }
  private_ip_google_access = true

  depends_on = [
    google_compute_network.vpc_network
  ]
}

### Create VPC network peering
resource "google_compute_global_address" "vpc_private_ip_address" {
  provider      = google
  project       = var.project_id
  name          = var.vpc_private_ip_address_name
  purpose       = "VPC_PEERING"
  address_type  = "INTERNAL"
  prefix_length = 16
  network       = google_compute_network.vpc_network.id
}

resource "google_service_networking_connection" "vpc_private_vpc_connection" {
  provider = google
  network  = google_compute_network.vpc_network.id
  service  = "servicenetworking.googleapis.com"
  reserved_peering_ranges = [
    google_compute_global_address.vpc_private_ip_address.name
  ]
}

### Create firewall rules
resource "google_compute_firewall" "fw_http" {
  provider = google
  project  = var.project_id
  name     = var.fw_http_name
  network  = google_compute_network.vpc_network.name
  allow {
    protocol = "tcp"
    ports    = ["80"]
  }
  target_tags   = ["http-server"]
  source_ranges = ["0.0.0.0/0"]
  disabled      = false
}

resource "google_compute_firewall" "fw_https" {
  provider = google
  project  = var.project_id
  name     = var.fw_https_name
  network  = google_compute_network.vpc_network.name
  allow {
    protocol = "tcp"
    ports    = ["443"]
  }
  target_tags   = ["https-server"]
  source_ranges = ["0.0.0.0/0"]
  disabled      = false
}

resource "google_compute_firewall" "allow_from_iap_to_instances" {
  provider = google
  project  = var.project_id
  name     = var.fw_ssh_name
  network  = google_compute_network.vpc_network.name
  allow {
    protocol = "tcp"
    ports    = ["22"]
  }
  source_ranges = ["35.235.240.0/20"]
}

### Create Cloud NAT
resource "google_compute_router" "router" {
  provider = google
  project  = var.project_id
  name     = var.router_name
  region   = var.region
  network  = google_compute_network.vpc_network.id
  bgp {
    asn = 64514
  }
}

resource "google_compute_router_nat" "cloud_nat" {
  provider                           = google
  project                            = var.project_id
  name                               = var.cloud_nat_name
  region                             = var.region
  router                             = google_compute_router.router.name
  nat_ip_allocate_option             = "AUTO_ONLY"
  source_subnetwork_ip_ranges_to_nat = "ALL_SUBNETWORKS_ALL_IP_RANGES"

  log_config {
    enable = false
    filter = "ERRORS_ONLY"
  }

  min_ports_per_vm = 64
}

### Create Kubernetes Cluster
resource "google_container_cluster" "cluster" {
  provider                  = google
  project                   = var.project_id
  name                      = var.cluster_name
  location                  = var.region
  remove_default_node_pool  = true
  initial_node_count        = 1
  logging_service           = "logging.googleapis.com/kubernetes"
  default_max_pods_per_node = 20
  networking_mode           = "VPC_NATIVE"
  network                   = google_compute_network.vpc_network.id
  subnetwork                = google_compute_subnetwork.vpc_subnetwork.id
  enable_shielded_nodes     = true

  private_cluster_config {
    enable_private_endpoint = false
    enable_private_nodes    = true
    master_ipv4_cidr_block  = "172.16.0.0/28"
  }

  default_snat_status {
    disabled = false
  }

  ip_allocation_policy {
    cluster_secondary_range_name  = "pods"
    services_secondary_range_name = "services"
  }

  workload_identity_config {
    workload_pool = "${data.google_project.project.project_id}.svc.id.goog"
  }

  depends_on = [
    google_compute_network.vpc_network,
    google_compute_subnetwork.vpc_subnetwork
  ]
}

### Create Kubernetes Node Pool
resource "google_container_node_pool" "node_pool" {
  provider   = google
  project    = var.project_id
  name       = var.node_pool_name
  location   = var.region
  cluster    = google_container_cluster.cluster.name
  node_count = 1

  node_config {
    preemptible  = true
    machine_type = "e2-micro"
    disk_size_gb = "10"
    disk_type    = "pd-ssd"
    image_type   = "cos"
    oauth_scopes = [
      "https://www.googleapis.com/auth/cloud-platform"
    ]

    labels = {
      disktype    = "ssd"
      cputype     = "e2"
      preemptible = "true"
    }
  }
}