{ config, lib, pkgs, ... }:

let
  cfg = config.bagel.services.postgres;

  dataDir = "/var/db/postgresql/16";
in {
  options.bagel.services.postgres = with lib; {
    enable = mkEnableOption "PostgreSQL server";
  };

  config = lib.mkIf cfg.enable {
    age.secrets.postgresql-tls-priv.owner = "postgres";
    age.secrets.postgresql-tls-priv.file = ../../secrets/postgres-tls-priv.age;

    systemd.tmpfiles.rules = [
      "d /var/db 0755 root root - -"
      "d /var/db/postgresql 0750 postgres postgres - -"
      "d ${dataDir} 0750 postgres postgres - -"
    ];

    services.postgresql = {
      enable = true;
      package = pkgs.postgresql_16;
      dataDir = dataDir;

      enableTCPIP = true;

      # TODO: Where to put this to properly couple things? It doesn't belong
      # here, but using it in services/hydra would require running on
      # localhost. Probably needs to be replaced with some different way of
      # ensuring the DB/user exist.
      ensureDatabases = [ "hydra" ];
      ensureUsers = [
        {
          name = "hydra";
          ensureDBOwnership = true;
        }
      ];
      identMap = ''
        hydra-users hydra hydra
        hydra-users hydra-queue-runner hydra
        hydra-users hydra-www hydra
        hydra-users root hydra
        # The postgres user is used to create the pg_trgm extension for the hydra database
        hydra-users postgres postgres
      '';
      authentication = ''
        local hydra all peer map=hydra-users

        # Allow any connection over TLS with a valid client certificate: signed
        # by our CA, and with username = cert CN.
        hostssl all all all cert clientcert=verify-full
      '';

      settings = {
        max_connections = 500;

        ssl = true;
        ssl_ca_file = "${./ca.crt}";
        ssl_cert_file = "${./server.crt}";
        ssl_key_file = config.age.secrets.postgresql-tls-priv.path;
      };
    };

    networking.firewall.allowedTCPPorts = [ config.services.postgresql.settings.port ];

    # Provisioned on the server so that CA operations can be done there.
    age.secrets.postgresql-ca-priv.owner = "postgres";
    age.secrets.postgresql-ca-priv.file = ../../secrets/postgres-ca-priv.age;

    users.users.postgres.packages = [
      (pkgs.writeShellScriptBin "postgres-mint-new-client" ''
        #! ${pkgs.runtimeShell}

        set -eo pipefail

        if [ $# -eq 0 ]; then
          echo "usage: $0 <pg-username>" >&2
          exit 1
        fi

        user=$1
        step=${pkgs.lib.getExe pkgs.step-cli}

        tmpdir=$(mktemp -d)
        trap "rm -rf $tmpdir" EXIT

        $step certificate create "$user" "$tmpdir/client.crt" "$tmpdir/client.key" \
          --profile leaf \
          --ca ${./ca.crt} \
          --ca-key ${config.age.secrets.postgresql-ca-priv.path} \
          --not-after 87660h \
          --no-password --insecure

        echo "Client certificate:"
        cat "$tmpdir/client.crt"
        echo

        echo "Client private key:"
        cat "$tmpdir/client.key"
      '')
    ];
  };
}