# The swarm's binary cache: an attic server in a `swarm-attic` container on the
# host that sets `deploy.attic.enable`, which `deploy.allSwarmServices` defaults
# on where the host has the cache's store identity. The swarm builder pushes
# green builds to it (docs/swarm/builder.md).
#
# Two host units run under the cache's own store leaf, the shape
# ./swarm-grafana.nix gives its admin password. One creates the key atticd signs
# tokens with, if the store holds none, and hands it to the container. The other
# creates the cache and the push and pull tokens, each only while absent
# (./lib/attic-init.nix). Neither needs a manual step.
#
# The container shares the host's network namespace, as ./swarm-victorialogs.nix
# does, and atticd listens on loopback only: the gateway's vhost is the way in,
# and attic's own tokens are the authentication. Storage is local disk under the
# container's state.
#
# The two `swarm.attic` options every host reads (./swarm-attic-options.nix) get
# their values from here, at `mkDefault`: naming them yourself wins, and with
# the switch off nothing is set.
{
  pkgs,
  lib,
  config,
  ...
}:
let
  hyperhiveCfg = config.services.hyperhive;
  cfg = hyperhiveCfg.deploy.attic;
  atticCfg = hyperhiveCfg.swarm.attic;
  baoCfg = hyperhiveCfg.swarm.bao;
  baoDeploy = hyperhiveCfg.deploy.bao;

  machine = "swarm-attic";
  unit = "swarm-attic";

  # Where the container keeps its database and the cache's files.
  stateName = "swarm-attic";
  stateDir = "/var/lib/${stateName}";

  # The host directory that carries the signing key into the container. The
  # key's file is the only thing in it.
  secretDir = "/run/swarm-attic-secrets";
  envFile = "${secretDir}/server.env";

  # Where the host units reach atticd: the shared loopback, not the gateway.
  endpoint = "http://127.0.0.1:${toString cfg.port}";

  configFile = (pkgs.formats.toml { }).generate "swarm-attic.toml" {
    listen = "127.0.0.1:${toString cfg.port}";
    # What clients are told to use for the cache's API.
    api-endpoint = "https://${atticCfg.domain}/";
    database.url = "sqlite://${stateDir}/server.db?mode=rwc";
    storage = {
      type = "local";
      path = "${stateDir}/storage";
    };
    # attic's defaults, which its config requires spelled out.
    chunking = {
      nar-size-threshold = 65536;
      min-size = 16384;
      avg-size = 65536;
      max-size = 262144;
    };
    garbage-collection = {
      interval = "12 hours";
      default-retention-period = cfg.retentionPeriod;
    };
  };

  atticInit = import ./lib/attic-init.nix { inherit lib; } {
    jwtPath = "secret/swarm/services/attic/jwt-secret";
    pullPath = "secret/swarm/services/attic/pull-token";
    pushPath = "secret/swarm/services/attic/push-token";
    cache = atticCfg.cache;
    inherit
      endpoint
      configFile
      envFile
      machine
      unit
      ;
  };

  atomicWriteSecret = import ./lib/atomic-write-secret.nix { };
  refreshConsumer = import ./lib/refresh-consumer.nix { };
  storeRetry = import ./lib/store-retry.nix { };

  haveClientIdentity = baoDeploy.atticClientCertFile != null && baoDeploy.atticClientKeyFile != null;

  # Both host units log in as the cache's principal.
  storeEnvironment = {
    BAO_ADDR = "https://${baoCfg.domain}:${toString baoCfg.port}";
    BAO_CLIENT_CERT = baoDeploy.atticClientCertFile;
    BAO_CLIENT_KEY = baoDeploy.atticClientKeyFile;
  }
  // lib.optionalAttrs (baoDeploy.serverCaFile != null) {
    BAO_CACERT = baoDeploy.serverCaFile;
  };
in
{
  options.services.hyperhive.deploy.attic = {
    package = lib.mkOption {
      type = lib.types.package;
      default = pkgs.attic-server;
      defaultText = lib.literalExpression "pkgs.attic-server";
      description = "The attic server package: `atticd`, and `atticadm` for the tokens.";
    };

    clientPackage = lib.mkOption {
      type = lib.types.package;
      default = pkgs.attic-client;
      defaultText = lib.literalExpression "pkgs.attic-client";
      description = "The attic client package, which creates the cache.";
    };

    port = lib.mkOption {
      type = lib.types.port;
      default = 8910;
      description = ''
        Loopback port atticd listens on, which the gateway proxies to.

        ⚠️ Every swarm container shares the host's network namespace, so this
        is a swarm-wide claim: two modules picking the same number collide at
        runtime with no bind error. No repo-wide check catches it.
      '';
    };

    retentionPeriod = lib.mkOption {
      type = lib.types.str;
      default = "14 days";
      example = "30 days";
      description = ''
        How long a store path stays in the cache after it was added or last
        fetched. A garbage collection every twelve hours removes what is older;
        a build the cache no longer holds is rebuilt on the next miss.
      '';
    };
  };

  config = lib.mkIf cfg.enable {
    services.hyperhive.swarm.attic = {
      domain = lib.mkDefault atticCfg.ownDomain;
      cache = lib.mkDefault "swarm";
    };

    assertions = [
      {
        assertion = haveClientIdentity;
        message = ''
          services.hyperhive.deploy.attic.enable requires the cache's
          swarm-secret-store client identity: set both

            services.hyperhive.deploy.bao.atticClientCertFile
            services.hyperhive.deploy.bao.atticClientKeyFile

          The cache creates its signing key and tokens in the store with it.

          Both default to the pair glue-bao-tls.nix mints when
          services.hyperhive.deploy.bao.enable is true (the host that runs the
          store). Otherwise copy attic.pem and attic-key.pem from the store
          host's /var/lib/swarm-bao-pki/ and name them in those two options.
        '';
      }
      {
        assertion = atticCfg.domain != null && atticCfg.cache != null;
        message = ''
          services.hyperhive.deploy.attic.enable needs
          services.hyperhive.swarm.attic.domain and
          services.hyperhive.swarm.attic.cache: it serves the cache at that name
          and creates it by that name. They default when unset, so one of them
          is set to null.
        '';
      }
    ];

    services.hyperhive.gateway.localNames = [ atticCfg.domain ];

    # This host serves the vhost, and the host's own resolver finds the name.
    services.hyperhive.gateway.enable = lib.mkDefault true;
    services.hyperhive.gateway.dns.enable = lib.mkDefault true;

    # `forceSSL`: the tokens ride in a header. No `auth_request`: attic checks
    # its own tokens, and a nix client cannot follow a login redirect. A store
    # path is uploaded as one request that can run for minutes, so the body is
    # neither size-limited nor buffered.
    services.hyperhive.gateway.vhosts."${atticCfg.domain}" = {
      forceSSL = true;
      locations."/" = {
        proxyPass = "http://127.0.0.1:${toString cfg.port}";
        extraConfig = ''
          client_max_body_size 0;
          proxy_request_buffering off;
          proxy_read_timeout 1h;
          proxy_send_timeout 1h;
        '';
      };
    };

    # The key's directory is the container's read-only bind source, so it has
    # to exist before the container starts even when the store does not answer.
    # The delivery unit creates it too, which covers a switch.
    systemd.tmpfiles.rules = [ "d ${secretDir} 0700 root root -" ];

    # The signing key, created in the store if it holds none and written where
    # the container reads it. Before the container and wanted by it: a store
    # that comes up later fails this run, atticd restarts until the file is
    # there, and the retry that lands it restarts atticd.
    systemd.services.swarm-bao-attic-secret = {
      description = "create the swarm cache's signing key in the secret store if absent and hand it to the container";
      # Ordered after the store where it runs here:
      # ./glue-bao-readers-store-order.nix and ./glue-bao-readers-policy-order.nix.
      before = [ "container@${machine}.service" ];
      wantedBy = [
        "multi-user.target"
        "container@${machine}.service"
      ];
      path = [
        baoDeploy.package
        pkgs.coreutils
        pkgs.openssl
        pkgs.systemd
      ];
      inherit (storeRetry) startLimitBurst startLimitIntervalSec;
      serviceConfig = storeRetry.serviceConfig // {
        Type = "oneshot";
        RemainAfterExit = true;
        SyslogIdentifier = "swarm-bao-attic-secret";
        # Generating a 4096-bit key takes seconds.
        TimeoutStartSec = 120;
      };
      environment = storeEnvironment;
      script = ''
        set -euo pipefail

        ${atomicWriteSecret}
        ${refreshConsumer}

        install -d -m 0700 ${lib.escapeShellArg secretDir}

        ${atticInit.prelude}
        ${atticInit.ensureJwt}
      '';
    };

    # The cache and its two tokens, once atticd answers. The push token is the
    # path the swarm builder reads; the pull token is for the hives.
    systemd.services.swarm-bao-attic-tokens = {
      description = "create the swarm cache, and its push and pull tokens in the secret store, if absent";
      after = [
        "container@${machine}.service"
        "swarm-bao-attic-secret.service"
      ];
      wants = [ "container@${machine}.service" ];
      wantedBy = [ "multi-user.target" ];
      path = [
        baoDeploy.package
        cfg.package
        cfg.clientPackage
        pkgs.coreutils
        pkgs.curl
      ];
      inherit (storeRetry) startLimitBurst startLimitIntervalSec;
      serviceConfig = storeRetry.serviceConfig // {
        Type = "oneshot";
        RemainAfterExit = true;
        SyslogIdentifier = "swarm-bao-attic-tokens";
        # Up to a minute waiting for atticd.
        TimeoutStartSec = 180;
      };
      environment = storeEnvironment;
      script = ''
        set -euo pipefail

        ${atticInit.prelude}
        ${atticInit.provision}
      '';
    };

    containers.${machine} = {
      autoStart = true;
      ephemeral = false;
      privateNetwork = false;
      bindMounts.${secretDir} = {
        hostPath = secretDir;
        isReadOnly = true;
      };

      config =
        { ... }:
        {
          imports = [ ../container-modules/swarm-container.nix ];

          services.hyperhive.swarmContainer.privateNetwork = false;

          systemd.services.${unit} = {
            description = "attic binary cache server";
            wantedBy = [ "multi-user.target" ];
            serviceConfig = {
              ExecStart = "${cfg.package}/bin/atticd -f ${configFile} --mode monolithic";
              # The signing key, in an environment file the host unit writes.
              EnvironmentFile = envFile;
              StateDirectory = stateName;
              DynamicUser = true;
              Restart = "on-failure";
              RestartSec = 10;
              SyslogIdentifier = unit;
              UMask = "0077";
              CapabilityBoundingSet = [ "" ];
              NoNewPrivileges = true;
              PrivateDevices = true;
              PrivateTmp = true;
              ProtectSystem = "strict";
              ProtectHome = true;
              ProtectKernelTunables = true;
              ProtectKernelModules = true;
              ProtectControlGroups = true;
              RestrictAddressFamilies = [
                "AF_INET"
                "AF_INET6"
                "AF_UNIX"
              ];
              RestrictNamespaces = true;
              RestrictRealtime = true;
              RestrictSUIDSGID = true;
              LockPersonality = true;
              SystemCallArchitectures = "native";
            };
          };
        };
    };
  };
}