data model: add tf deployment

deployment/data-model.nix

@@ -44,6 +44,10 @@ let
       description = "A NixOps4 NixOS deployment. For an example, see https://github.com/nixops4/nixops4-nixos/blob/main/example/deployment.nix.";
       type = nixops4Deployment;
     };
+    tf-ssh = mkOption {
+      description = "A Terraform deployment by SSH to update a single existing NixOS host";
+      type = types.attrset;
+    };
   };
 in
 {

infra/dev/main.nix

@@ -0,0 +1,38 @@
+let
+  vm_domain = "abundos.eu";
+in
+{
+  module."nixos" =
+    builtins.mapAttrs
+      (service: hostname: {
+        source = "../sync-nix";
+        inherit vm_domain hostname;
+        config_tf = {
+          terraform = {
+            inherit hostname;
+            domain = vm_domain;
+          };
+        };
+        config_nix = ''
+          {
+            imports = [
+              # shared NixOS config
+              $${path.root}/../common/shared.nix
+              # FIXME: separate template options by service
+              $${path.root}/options.nix
+              # for service `forgejo` import `forgejo.nix`
+              $${path.root}/../../machines/dev/${hostname}/${service}.nix
+              # FIXME: get VM details from TF
+              $${path.root}/../../machines/dev/${hostname}
+            ];
+          }
+        '';
+      })
+      {
+        # wiki = "vm02187" # does not resolve
+        # forgejo = "vm02116" # does not resolve
+        # TODO: move these to a separate `host` dir
+        dns = "fedi200";
+        # fedipanel = "fedi201";
+      };
+}

infra/sync-nix/main.tf

@@ -0,0 +1,91 @@
+locals {
+  system = "x86_64-linux"
+  # dependency paths pre-calculated from npins
+  pins = jsondecode(file("${path.module}/.npins.json"))
+  # nix path: expose pins, use nixpkgs in flake commands (`nix run`)
+  nix_path = "${join(":", [for name, dir in local.pins : "${name}=${dir}"])}:flake=${local.pins["nixpkgs"]}:flake"
+}
+
+# hash of our code directory, used to trigger re-deploy
+# FIXME calculate separately to reduce false positives
+data "external" "hash" {
+  program = ["sh", "-c", "echo \"{\\\"hash\\\":\\\"$(nix-hash ..)\\\"}\""]
+}
+
+# TF resource to build and deploy NixOS instances.
+resource "terraform_data" "nixos" {
+
+  # trigger rebuild/deploy if (FIXME?) any potentially used config/code changed,
+  # preventing these (20+s, build being bottleneck) when nothing changed.
+  # terraform-nixos separates these to only deploy if instantiate changed,
+  # yet building even then - which may be not as bad using deploy on remote.
+  # having build/deploy one resource reflects wanting to prevent no-op rebuilds
+  # over preventing (with less false positives) no-op deployments,
+  # as i could not find a way to do prevent no-op rebuilds without merging them:
+  # - generic resources cannot have outputs, while we want info from the instantiation (unless built on host?).
+  # - `data` always runs, which is slow for deploy and especially build.
+  triggers_replace = [
+    data.external.hash.result,
+    var.hostname,
+    var.config_nix,
+    var.config_tf,
+  ]
+
+  provisioner "local-exec" {
+    # directory to run the script from. we use the TF project root dir,
+    # here as a path relative from where TF is run from,
+    # matching calling modules' expectations on config_nix locations.
+    # note that absolute paths can cause false positives in triggers,
+    # so are generally discouraged in TF.
+    working_dir = path.root
+    environment = {
+      # nix path used on build, lets us refer to e.g. nixpkgs like `<nixpkgs>`
+      NIX_PATH = local.nix_path
+    }
+    # TODO: refactor back to command="ignoreme" interpreter=concat([]) to protect sensitive data from error logs?
+    # TODO: build on target?
+    command = <<-EOF
+      set -euo pipefail
+
+      # INSTANTIATE
+      command=(
+        nix-instantiate
+        --expr
+        'import ./nixos.nix {
+          system = "${local.system}";
+          configuration =
+            ${var.config_nix} //
+            builtins.fromJSON "${replace(jsonencode(var.config_tf), "\"", "\\\"")}" //
+            {
+              nix.nixPath = [ "${local.nix_path}" ];
+            };
+        }'
+      )
+      # instantiate the config in /nix/store
+      "$${command[@]}" -A out_path
+      # get the other info
+      json="$("$${command[@]}" --eval --strict --json)"
+
+      # DEPLOY
+      declare substituters trusted_public_keys drv_path
+      # set our variables using the json object
+      eval "export $(echo $json | jaq -r 'to_entries | map("\(.key)=\(.value)") | @sh')"
+      host="root@${var.hostname}.${var.vm_domain}" # FIXME: #24
+      buildArgs=(
+        --option extra-binary-caches https://cache.nixos.org/
+        --option substituters $substituters
+        --option trusted-public-keys $trusted_public_keys
+      )
+      sshOpts=(
+        -o BatchMode=yes
+        -o StrictHostKeyChecking=no
+      )
+      # get the realized derivation to deploy
+      outPath=$(nix-store --realize "$drv_path" "$${buildArgs[@]}")
+      # deploy the config by nix-copy-closure
+      NIX_SSHOPTS="$${sshOpts[*]}" nix-copy-closure --to "$host" "$outPath" --gzip --use-substitutes
+      # switch the remote host to the config
+      ssh "$${sshOpts[@]}" "$host" "nix-env --profile /nix/var/nix/profiles/system --set $outPath; $outPath/bin/switch-to-configuration switch"
+    EOF
+  }
+}

infra/sync-nix/nixos.nix

@@ -0,0 +1,14 @@
+{
+  configuration,
+  system ? builtins.currentSystem,
+}:
+let
+  sources = import ../../npins;
+  os = import "${sources.nixpkgs}/nixos" { inherit system configuration; };
+in
+{
+  substituters = builtins.concatStringsSep " " os.config.nix.settings.substituters;
+  trusted_public_keys = builtins.concatStringsSep " " os.config.nix.settings.trusted-public-keys;
+  drv_path = os.config.system.build.toplevel.drvPath;
+  out_path = os.config.system.build.toplevel;
+}

infra/sync-nix/variables.nix

@@ -0,0 +1,27 @@
+# TODO: generate nix module from `variables.tf`
+# - TF -> JSON schema: https://melvinkoh.me/parsing-terraform-for-forms-clr4zq4tu000309juab3r1lf7
+#   - python313Packages.python-hcl2: hcl2tojson variables.tf
+# - JSON schema -> nix
+{ lib, ... }:
+let
+  inherit (lib) mkOption types;
+  inherit (types) string attrsOf any;
+in
+{
+  options = {
+    vm_domain = mkOption {
+      type = string;
+    };
+    hostname = mkOption {
+      type = string;
+    };
+    config_nix = mkOption {
+      type = string;
+      default = { };
+    };
+    config_tf = mkOption {
+      type = attrsOf any;
+      default = { };
+    };
+  };
+}

infra/sync-nix/variables.tf

@@ -0,0 +1,17 @@
+variable "vm_domain" {
+  type = string
+}
+
+variable "hostname" {
+  type = string
+}
+
+variable "config_nix" {
+  type = string
+  default = "{}"
+}
+
+variable "config_tf" {
+  type = map(any)
+  default = {}
+}