implement applications.mastodon as a sample use-case of our data model

deployment/applications/default.nix

@@ -0,0 +1,5 @@
+{
+  imports = [
+    ./mastodon.nix
+  ];
+}

deployment/applications/mastodon.nix

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+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+{
+  applications.mastodon =
+    { ... }:
+    {
+      description = ''
+        Mastodon: Your self-hosted, globally interconnected microblogging community
+      '';
+      module =
+        # # usage:
+        # {
+        #   config.fediversity.domain = lib.mkOption {
+        #     type = lib.types.str;
+        #     default = "fediversity.tld";
+        #   };
+        # }
+        { lib, config, ... }:
+        {
+          options = import ../../../services/fediversity/sharedOptions.nix {
+            inherit config lib;
+            serviceName = "mastodon";
+            serviceDocName = "Mastodon";
+          };
+        };
+      # this is ported from `services/fediversity/mastodon/default.nix`. what of `services/vm/mastodon-vm.nix`?
+      implementation =
+        cfg:
+        # {
+        #   config,
+        #   lib,
+        #   pkgs,
+        #   ...
+        # }:
+        let
+          inherit (lib) mkIf mkMerge readFile;
+          inherit (pkgs) writeText;
+        in
+        lib.optionalAttrs cfg.enable {
+          # # not using this part as we split this out in our data model.
+          # imports = [ ./options.nix ];
+
+          config = mkMerge [
+            (mkIf
+              (config.fediversity.garage.enable && cfg.s3AccessKeyFile != null && cfg.s3SecretKeyFile != null)
+              {
+                fediversity.garage = {
+                  ensureBuckets = {
+                    mastodon = {
+                      website = true;
+                      corsRules = {
+                        enable = true;
+                        allowedHeaders = [ "*" ];
+                        allowedMethods = [ "GET" ];
+                        allowedOrigins = [ "*" ];
+                      };
+                    };
+                  };
+
+                  ensureKeys = {
+                    mastodon = {
+                      inherit (cfg) s3AccessKeyFile s3SecretKeyFile;
+                      ensureAccess = {
+                        mastodon = {
+                          read = true;
+                          write = true;
+                          owner = true;
+                        };
+                      };
+                    };
+                  };
+                };
+              }
+            )
+
+            (mkIf cfg.enable {
+
+              services.mastodon.extraConfig = rec {
+                S3_ENABLED = "true";
+                # TODO: this shouldn't be hard-coded, it should come from the garage configuration
+                S3_ENDPOINT = config.fediversity.garage.api.url;
+                S3_REGION = "garage";
+                S3_BUCKET = "mastodon";
+                # use <S3_BUCKET>.<S3_ENDPOINT>
+                S3_OVERRIDE_PATH_STLE = "true";
+                S3_PROTOCOL = "http";
+                S3_ALIAS_HOST = config.fediversity.garage.web.domainForBucket S3_BUCKET;
+                # SEE: the last section in https://docs.joinmastodon.org/admin/optional/object-storage/
+                # TODO: can we set up ACLs with garage?
+                S3_PERMISSION = "";
+              };
+
+              ## FIXME: secrets management; we should have a service that writes the
+              ## `.env` files based on all the secrets that we need to put there.
+              services.mastodon.extraEnvFiles = [
+                (writeText "s3AccessKey" ''
+                  AWS_ACCESS_KEY_ID=${readFile cfg.s3AccessKeyFile}
+                '')
+                (writeText "s3SecretKey" ''
+                  AWS_SECRET_ACCESS_KEY=${readFile cfg.s3SecretKeyFile}
+                '')
+              ];
+
+              # open up access to the mastodon web interface. 80 is necessary if only for ACME
+              networking.firewall.allowedTCPPorts = [
+                80
+                443
+              ];
+
+              services.mastodon = {
+                enable = true;
+
+                localDomain = cfg.domain;
+                configureNginx = true;
+
+                # from the documentation: recommended is the amount of your CPU cores minus
+                # one. but it also must be a positive integer
+                streamingProcesses = lib.max 1 (config.fediversity.temp.cores - 1);
+
+                # TODO: configure a mailserver so this works
+                smtp = {
+                  fromAddress = "noreply@${cfg.domain}";
+                  createLocally = false;
+                };
+              };
+
+              security.acme = {
+                acceptTerms = true;
+                preliminarySelfsigned = true;
+                # TODO: configure a mailserver so we can set up acme
+                # defaults.email = "test@example.com";
+              };
+            })
+          ];
+        };
+    };
+}