{ config, pkgs, lib, tflib, ... }:
let
  cfg = config.prefab.nomadServer;
  inherit (lib)
    mapAttrsToList
    foldAttrs
    mergeAttrs
    fix
    flip
    mkOption
    types
    optionalString
    optionalAttrs
    mkMerge
  ;

  inherit ((a: builtins.break a) tflib)
    tf
    ;

  submoduleOptions = {
    datacenters = mkOption {
      description = ''
      '';
      type = with types; listOf str;
    };

    encryptionKey = mkOption {
      description = ''
        DO NOT hardcode the secret in Nix, generate it with Terraform
        and let Terraform substitute it.
      '';
      type = types.str;
    };

    paths = {
      encryptionKey = mkOption {
        description = ''
        '';
        type = types.str;
      };
      replicationToken = mkOption {
        description = ''
        '';
        type = with types; nullOr str;
        default = null;
      };
      vaultToken = mkOption {
        description = ''
        '';
        type = types.str;
      };
      consulToken = mkOption {
        description = ''
        '';
        type = types.str;
      };
    };

    vaultKvMount = mkOption {
      description = ''
      '';
      type = types.str;
    };
  };
in
{
  options.prefab.nomadServer = mkOption {
    description = ''
    '';
    type = with types; attrsOf (submodule { options = submoduleOptions; });
    default = {};
  };

  config.resource = mkMerge
    (flip mapAttrsToList cfg (hostname: value:
      fix (self: {
        "vault_policy"."${hostname}_nomad" = {
          name = "${hostname}-nomad-server-agent";

          policy = ''
          path "${value.vaultKvMount}/data/${value.paths.encryptionKey}" {
              capabilities = ["read"]
            }

            path "${value.vaultKvMount}/data/${value.paths.vaultToken}" {
              capabilities = ["read"]
            }

            path "${value.vaultKvMount}/data/${value.paths.consulToken}" {
              capabilities = ["read"]
            }

            ${optionalString (value.paths.replicationToken != null) ''
              path "${value.vaultKvMount}/data/${value.paths.replicationToken}" {
                capabilities = ["read"]
              }
            ''}
          '';
        };

        "vault_kv_secret_v2"."${hostname}_nomad_encryption_key" = {
          mount = value.vaultKvMount;
          name = value.paths.encryptionKey;
          delete_all_versions = true;
          data_json = builtins.toJSON {
            key = value.encryptionKey;
          };
        };

        "consul_acl_policy"."${hostname}_nomad_server" = {
          name        = "${hostname}_nomad_server";
          rules       = ''
            agent_prefix "" {
              policy = "read"
            }

            node_prefix "" {
              policy = "read"
            }

            service_prefix "" {
              policy = "write"
            }

            acl = "write"
          '';
        };

        "consul_acl_token"."${hostname}_nomad_server" = {
          description = "Consul token for nomad_server on ${hostname}";
          policies = [
            (tf "consul_acl_policy.${hostname}_nomad_server.name")
          ];
          local = false;
        };

        "vault_kv_secret_v2"."${hostname}_nomad_server_consul" = {
          mount = value.vaultKvMount;
          name = value.paths.consulToken;
          delete_all_versions = true;
          data_json = builtins.toJSON {
            secret = tf "data.consul_acl_token_secret_id.${hostname}_nomad_server.secret_id";
            accessor = tf "consul_acl_token.${hostname}_nomad_server.accessor_id";
          };
        };

        "vault_policy"."${hostname}_nomad_server" = {
          name = "${hostname}-nomad-server";

          policy = ''
            # Allow creating tokens under "nomad-cluster" token role. The token role name
            # should be updated if "nomad-cluster" is not used.
            path "auth/token/create/nomad-cluster" {
              capabilities = ["update"]
            }

            # Allow looking up "nomad-cluster" token role. The token role name should be
            # updated if "nomad-cluster" is not used.
            path "auth/token/roles/nomad-cluster" {
              capabilities = ["read"]
            }

            # Allow looking up the token passed to Nomad to validate the token has the
            # proper capabilities. This is provided by the "default" policy.
            path "auth/token/lookup-self" {
              capabilities = ["read"]
            }

            # Allow looking up incoming tokens to validate they have permissions to access
            # the tokens they are requesting. This is only required if
            # `allow_unauthenticated` is set to false.
            path "auth/token/lookup" {
              capabilities = ["update"]
            }

            # Allow revoking tokens that should no longer exist. This allows revoking
            # tokens for dead tasks.
            path "auth/token/revoke-accessor" {
              capabilities = ["update"]
            }

            # Allow checking the capabilities of our own token. This is used to validate the
            # token upon startup. Note this requires update permissions because the Vault API
            # is a POST
            path "sys/capabilities-self" {
              capabilities = ["update"]
            }

            # Allow our own token to be renewed.
            path "auth/token/renew-self" {
              capabilities = ["update"]
            }
          '';
        };

        "vault_token_auth_backend_role"."${hostname}_nomad_server" = {
          role_name = "${hostname}_nomad_server";
          allowed_policies = [
            (tf "vault_policy.${hostname}_nomad_server.name")
          ];
          orphan = true;
          renewable = true;
        };

        "vault_token"."${hostname}_nomad_server" = {
          policies = [
            (tf "vault_policy.${hostname}_nomad_server.name")
          ];
          renewable = true;
          ttl = "24h";
          explicit_max_ttl = 0;
          role_name = tf "vault_token_auth_backend_role.${hostname}_nomad_server.role_name";
          display_name = "${hostname}-nomad-server-Vault-token";
        };

        "vault_kv_secret_v2"."${hostname}_nomad_server_vault" = {
          mount = value.vaultKvMount;
          name = value.paths.vaultToken;
          delete_all_versions = true;
          data_json = builtins.toJSON {
            secret = tf "vault_token.${hostname}_nomad_server.client_token";
          };
        };

      })) ++
    (flip mapAttrsToList cfg (hostname: value:
      (optionalAttrs (value.paths.replicationToken != null)
        {
          "nomad_acl_token"."${hostname}_replication" = {
            name = "${hostname} replication token";
            type = "management";
          };

          "vault_kv_secret_v2"."${hostname}_nomad_replication" = {
            mount = value.vaultKvMount;
            name = value.paths.replicationToken;
            delete_all_versions = true;
            data_json = builtins.toJSON {
              secret = tf "nomad_acl_token.${hostname}_replication.secret_id";
              accessor = tf "nomad_acl_token.${hostname}_replication.id";
            };
          };
        }
      )
    )));

  config.data = mkMerge
    (flip mapAttrsToList cfg (hostname: value:
      {
        "consul_acl_token_secret_id"."${hostname}_nomad_server" = {
          accessor_id = tf "consul_acl_token.${hostname}_nomad_server.id";
        };
      }));

}