# The binary-cache facts the host's nix daemon, hive-priv (root) and hive-c0re
# use, kept where only root can change them.
#
# hive-c0re pulls an agent's closure from the swarm cache with its own
# `nix copy --from`: the client does the HTTP fetch with the pull token, and
# hands the NAR to the host's nix daemon, which stores it only if a key in its
# `trusted-public-keys` signed it. hive-priv applies a closure only if the
# swarm's key signed it. What decides that must not come from a file the
# unprivileged hive-c0re writes. So:
#
# - the cache's address is this host's configuration
#   ({option}`services.hyperhive.swarm.attic.domain` and `cache`), handed to
#   hive-c0re in its unit's environment;
# - the cache's public key and the pull token are read from the store by a root
#   oneshot, `hive-priv-cache-facts`, under this hive's own store identity. The
#   key and the token land in `/run/hyperhive-priv/attic/` (root, `0700`; files
#   `0600`). The key also lands in a nix.conf fragment,
#   `/run/hyperhive-nix/cache.conf`, as `extra-trusted-public-keys`, which the
#   host's nix.conf includes (`!include`, so a host whose unit has not run yet
#   still starts). The fragment names no substituter and no netrc, so a client
#   of the daemon that is not hive-c0re (an agent container on `nixBuilds =
#   host`) cannot fetch from the cache or send the token;
# - the token also lands in `/run/hyperhive-nix/netrc`, `root:hive-core 0640`:
#   the one place hive-core, and nothing else unprivileged, can read it.
#
# hive-c0re keeps its own copies under `/run/hyperhive/attic/` for the probe,
# which only reports.
{
  pkgs,
  lib,
  config,
  ...
}:
let
  hyperhiveCfg = config.services.hyperhive;
  hiveController = hyperhiveCfg.deploy.hive-controller;
  tls = hiveController.tls;
  baoCfg = hyperhiveCfg.swarm.bao;
  baoDeploy = hyperhiveCfg.deploy.bao;
  atticCfg = hyperhiveCfg.swarm.attic;

  # Without a cache to name, a hive name to read under or an identity to log
  # in with there is nothing to fetch, and hive-priv has no cache to download
  # from.
  enabled =
    hiveController.enable
    && atticCfg.domain != null
    && atticCfg.cache != null
    && hiveController.hiveName != null
    && tls.baoHiveIdentityCertFile != null
    && tls.baoHiveIdentityKeyFile != null;

  dir = "/run/hyperhive-priv/attic";
  confDir = "/run/hyperhive-nix";
  confFile = "${confDir}/cache.conf";
  clientNetrc = "${confDir}/netrc";

  # Where the store runs on this host, the first login waits for its container.
  # No `wants`: a pull would start the container mid-switch on the old closure.
  storeContainer = lib.optional baoDeploy.enable "container@${baoCfg.machine}.service";

  storeRetry = import ./lib/store-retry.nix { };
  storeRefreshTimer = import ./lib/store-refresh-timer.nix { };
in
{
  config = lib.mkIf enabled {
    systemd.tmpfiles.rules = [
      "d /run/hyperhive-priv 0700 root root - -"
      "d ${confDir} 0755 root root - -"
    ];

    # `!include` tolerates a fragment that does not exist yet.
    nix.extraOptions = "!include ${confFile}";

    # The address hive-c0re names to `nix copy --from`; no request chooses it.
    systemd.services.hive-c0re.environment.HIVE_C0RE_CACHE_URL =
      "https://${atticCfg.domain}/${atticCfg.cache}";

    systemd.services.hive-priv-cache-facts = {
      description = "Read the swarm cache's public key and pull token for the host's nix daemon and hive-priv";
      wantedBy = [ "multi-user.target" ];
      wants = [ "network-online.target" ];
      after = [
        "network-online.target"
        "systemd-tmpfiles-setup.service"
      ]
      ++ storeContainer;
      path = [
        baoDeploy.package
        pkgs.coreutils
        pkgs.gnugrep
        pkgs.systemd
      ];
      environment = {
        BAO_ADDR = "https://${baoCfg.domain}:${toString baoCfg.port}";
        BAO_CLIENT_CERT = tls.baoHiveIdentityCertFile;
        BAO_CLIENT_KEY = tls.baoHiveIdentityKeyFile;
      }
      // lib.optionalAttrs (baoDeploy.serverCaFile != null) {
        BAO_CACERT = baoDeploy.serverCaFile;
      };
      # ./lib/store-retry.nix: the login fails for as long as the store is
      # sealed or down.
      inherit (storeRetry) startLimitBurst startLimitIntervalSec;
      serviceConfig = storeRetry.serviceConfig // {
        Type = "oneshot";
        UMask = "0077";
        SyslogIdentifier = "hive-priv-cache-facts";
        TimeoutStartSec = "5min";
      };
      script = import ./lib/attic-root-facts.nix { inherit lib; } {
        hive = hiveController.hiveName;
        host = atticCfg.domain;
        inherit dir confFile clientNetrc;
        clientGroup = config.users.users.hive-core.group;
      };
    };

    systemd.timers.hive-priv-cache-facts = storeRefreshTimer "re-read the swarm cache's facts for hive-priv";
  };
}