# SPDX-FileCopyrightText: 2022-2023 Simon Bruder <simon@sbruder.de>
#
# SPDX-License-Identifier: AGPL-3.0-or-later

{ config, inputs, lib, pkgs, ... }:
let
  cfg = config.sbruder.qbittorrent;
in
{
  options.sbruder.qbittorrent = {
    enable = lib.mkEnableOption "the qbittorrent service";
    homeDir = lib.mkOption {
      type = lib.types.path;
      default = "/var/lib/qbittorrent";
    };
    configDir = lib.mkOption {
      type = lib.types.path;
      default = "${cfg.homeDir}/config";
    };
    downloadDir = lib.mkOption {
      type = lib.types.path;
      default = "${cfg.homeDir}/download";
    };
    webuiPort = lib.mkOption {
      type = lib.types.int;
      default = 8099;
    };
    sopsFile = lib.mkOption {
      type = lib.types.path;
      default = ../../machines/${config.networking.hostName}/secrets.yaml;
      description = ''
        The sops secret file that includes the wireguard private key (wg-qbittorrent-private-key).
      '';
    };
    wireguardConnectionDetails = lib.mkOption {
      type = lib.types.attrs;
      default = import ../../machines/${config.networking.hostName}/secrets/wireguard-qbittorrent.nix;
      example = {
        ips = [ "10.0.0.1/32" "fd00::1/128" ];

        peers = lib.singleton {
          publicKey = "MbLFO7MIFSdwVmZWQG//IUxVxwSHprRkhr/NWl2gils=";
          allowedIPs = [ "0.0.0.0/0" "::0/0" ];
          endpoint = "192.0.2.1:51820";
        };
      };
      description = "The connection details for the WireGuard tunnel.";
    };
    fqdn = lib.mkOption {
      type = lib.types.str;
      description = "The fqdn nginx should listen on. It must not be used for anything else.";
    };
  };

  config = lib.mkIf cfg.enable
    {
      users.users.qbittorrent = {
        group = "qbittorrent";
        home = cfg.homeDir;
        isSystemUser = true;
      };
      users.groups.qbittorrent = { };

      systemd.tmpfiles.rules = [
        "d '${cfg.downloadDir}' 0775 qbittorrent users - -"
        "d '${cfg.homeDir}' 0771 qbittorrent qbittorrent - -"
      ];

      sops.secrets.wg-qbittorrent-private-key.sopsFile = cfg.sopsFile;

      networking.wireguard.interfaces.wg-qbittorrent = {
        interfaceNamespace = "qbittorrent";
        preSetup = "ip netns add qbittorrent && ip -n qbittorrent link set lo up";
        postShutdown = "ip netns del qbittorrent";

        privateKeyFile = config.sops.secrets.wg-qbittorrent-private-key.path;
      } // (builtins.removeAttrs cfg.wireguardConnectionDetails [ "nameserver" ]);

      environment.etc."netns/qbittorrent/resolv.conf".text = ''
        nameserver ${cfg.wireguardConnectionDetails.nameserver}
      '';

      systemd.services.qbittorrent = {
        description = "qBittorrent Service";
        after = [ "wireguard-wg-qbittorrent.service" ];
        requires = [ "wireguard-wg-qbittorrent.service" ];
        wantedBy = [ "multi-user.target" ];

        serviceConfig = {
          PrivateNetwork = true;
          NetworkNamespacePath = "/run/netns/qbittorrent";

          Restart = "always";
          ExecStart = "${pkgs.qbittorrent-nox}/bin/qbittorrent-nox --profile=${cfg.configDir} --webui-port=${toString cfg.webuiPort}";
          User = "qbittorrent";
          Group = "qbittorrent";

          # Increase number of open file descriptors (default: 1024)
          LimitNOFILE = 65536;

          # Avoid using nscd (leaks dns)
          InaccessiblePaths = [
            "/run/nscd"
            "/etc/nsswitch.conf"
          ];
          # Make correct resolv.conf available for unit
          BindReadOnlyPaths = [
            "/etc/netns/qbittorrent/resolv.conf:/etc/resolv.conf"
          ];


          # systemd-analyze --no-pager security qbittorrent.service
          CapabilityBoundingSet = null;
          PrivateDevices = true;
          PrivateTmp = true;
          PrivateUsers = true;
          ProtectHome = true;
          RestrictNamespaces = true;
          SystemCallFilter = "@system-service";
        };
      };

      systemd.services.qbittorrent-webui-proxy = {
        wantedBy = [ "multi-user.target" ];
        after = [ "wireguard-wg-qbittorrent.service" ];
        partOf = [ "wireguard-wg-qbittorrent.service" ];

        serviceConfig = {
          PrivateNetwork = true;
          NetworkNamespacePath = "/run/netns/qbittorrent";

          Restart = "always";
          ExecStart = "${pkgs.socat}/bin/socat UNIX-LISTEN:${cfg.homeDir}/webui.sock,fork,reuseaddr,mode=660,unlink-early TCP:127.0.0.1:${toString cfg.webuiPort}";
          User = "qbittorrent";
          Group = "nginx";

          # systemd-analyze --no-pager security qbittorrent-webui-proxy.service
          CapabilityBoundingSet = null;
          PrivateDevices = true;
          PrivateTmp = true;
          PrivateUsers = true;
          ProtectHome = true;
          RestrictNamespaces = true;
          SystemCallFilter = "@system-service";
        };
      };

      systemd.services.qbittorrent_exporter = {
        wantedBy = [ "multi-user.target" ];
        after = [ "network.target" ];
        environment = {
          QBITTORRENT_API_SOCKET = "${cfg.homeDir}/webui.sock";
          QBITTORRENT_EXPORTER_LISTEN_ADDRESS = ":9561";
        };
        serviceConfig = {
          ExecStart = "${pkgs.callPackage ./exporter { }}/bin/qbittorrent_exporter";
          Restart = "always";
          User = "qbittorrent";
          Group = "qbittorrent";

          # systemd-analyze --no-pager security qbittorrent_exporter.service
          CapabilityBoundingSet = null;
          PrivateDevices = true;
          PrivateUsers = true;
          ProtectHome = true;
          RestrictAddressFamilies = [ "AF_INET" "AF_INET6" "AF_UNIX" ];
          RestrictNamespaces = true;
          SystemCallArchitectures = "native";
          SystemCallFilter = "@system-service";
        };
      };

      services.nginx.virtualHosts."${cfg.fqdn}" = {
        enableACME = lib.mkDefault true;
        forceSSL = lib.mkDefault true;

        # treated as state
        basicAuthFile = "${cfg.homeDir}/htpasswd";

        locations = {
          "/" = {
            proxyPass = "http://unix:${cfg.homeDir}/webui.sock";
            proxyWebsockets = true;
          };
          "/download/" = {
            alias = "${cfg.downloadDir}/";
            extraConfig = ''
              autoindex on;
            '';
          };
          "=/metrics" = {
            proxyPass = "http://127.0.0.1:9561/metrics";
          };
        };
      };
    };
}