{ config, lib, pkgs, ... }:
with lib;
let
  cfg = config.services.seafile;
  settingsFormat = pkgs.formats.ini { };

  ccnetConf = settingsFormat.generate "ccnet.conf" cfg.ccnetSettings;

  seafileConf = settingsFormat.generate "seafile.conf" cfg.seafileSettings;

  seahubSettings = pkgs.writeText "seahub_settings.py" ''
    FILE_SERVER_ROOT = '${cfg.ccnetSettings.General.SERVICE_URL}/seafhttp'
    DATABASES = {
        'default': {
            'ENGINE': 'django.db.backends.sqlite3',
            'NAME': '${seahubDir}/seahub.db',
        }
    }
    MEDIA_ROOT = '${seahubDir}/media/'
    THUMBNAIL_ROOT = '${seahubDir}/thumbnail/'

    SERVICE_URL = '${cfg.ccnetSettings.General.SERVICE_URL}'

    with open('${seafRoot}/.seahubSecret') as f:
        SECRET_KEY = f.readline().rstrip()

    ${cfg.seahubExtraConf}
  '';

  seafRoot = "/var/lib/seafile"; # hardcode it due to dynamicuser
  ccnetDir = "${seafRoot}/ccnet";
  dataDir = "${seafRoot}/data";
  seahubDir = "${seafRoot}/seahub";

in
{

  ###### Interface

  options.services.seafile = {
    enable = mkEnableOption "Seafile server";

    ccnetSettings = mkOption {
      type = types.submodule {
        freeformType = settingsFormat.type;

        options = {
          General = {
            SERVICE_URL = mkOption {
              type = types.str;
              example = "https://www.example.com";
              description = ''
                Seahub public URL.
              '';
            };
          };
        };
      };
      default = { };
      description = ''
        Configuration for ccnet, see
        <https://manual.seafile.com/config/ccnet-conf/>
        for supported values.
      '';
    };

    seafileSettings = mkOption {
      type = types.submodule {
        freeformType = settingsFormat.type;

        options = {
          fileserver = {
            port = mkOption {
              type = types.port;
              default = 8082;
              description = ''
                The tcp port used by seafile fileserver.
              '';
            };
            host = mkOption {
              type = types.str;
              default = "127.0.0.1";
              example = "0.0.0.0";
              description = ''
                The binding address used by seafile fileserver.
              '';
            };
          };
        };
      };
      default = { };
      description = ''
        Configuration for seafile-server, see
        <https://manual.seafile.com/config/seafile-conf/>
        for supported values.
      '';
    };

    workers = mkOption {
      type = types.int;
      default = 4;
      example = 10;
      description = ''
        The number of gunicorn worker processes for handling requests.
      '';
    };

    adminEmail = mkOption {
      example = "john@example.com";
      type = types.str;
      description = ''
        Seafile Seahub Admin Account Email.
      '';
    };

    initialAdminPassword = mkOption {
      example = "someStrongPass";
      type = types.str;
      description = ''
        Seafile Seahub Admin Account initial password.
        Should be change via Seahub web front-end.
      '';
    };

    seafilePackage = mkPackageOption pkgs "seafile-server" { };

    seahubExtraConf = mkOption {
      default = "";
      type = types.lines;
      description = ''
        Extra config to append to `seahub_settings.py` file.
        Refer to <https://manual.seafile.com/config/seahub_settings_py/>
        for all available options.
      '';
    };
  };

  ###### Implementation

  config = mkIf cfg.enable {

    environment.etc."seafile/ccnet.conf".source = ccnetConf;
    environment.etc."seafile/seafile.conf".source = seafileConf;
    environment.etc."seafile/seahub_settings.py".source = seahubSettings;

    systemd.targets.seafile = {
      wantedBy = [ "multi-user.target" ];
      description = "Seafile components";
    };

    systemd.services =
      let
        securityOptions = {
          ProtectHome = true;
          PrivateUsers = true;
          PrivateDevices = true;
          ProtectClock = true;
          ProtectHostname = true;
          ProtectProc = "invisible";
          ProtectKernelModules = true;
          ProtectKernelTunables = true;
          ProtectKernelLogs = true;
          ProtectControlGroups = true;
          RestrictNamespaces = true;
          LockPersonality = true;
          RestrictRealtime = true;
          RestrictSUIDSGID = true;
          MemoryDenyWriteExecute = true;
          SystemCallArchitectures = "native";
          RestrictAddressFamilies = [ "AF_UNIX" "AF_INET" ];
        };
      in
      {
        seaf-server = {
          description = "Seafile server";
          partOf = [ "seafile.target" ];
          after = [ "network.target" ];
          wantedBy = [ "seafile.target" ];
          restartTriggers = [ ccnetConf seafileConf ];
          path = [ pkgs.sqlite ];
          serviceConfig = securityOptions // {
            User = "seafile";
            Group = "seafile";
            DynamicUser = true;
            StateDirectory = "seafile";
            RuntimeDirectory = "seafile";
            LogsDirectory = "seafile";
            ConfigurationDirectory = "seafile";
            ExecStart = ''
              ${cfg.seafilePackage}/bin/seaf-server \
              --foreground \
              -F /etc/seafile \
              -c ${ccnetDir} \
              -d ${dataDir} \
              -l /var/log/seafile/server.log \
              -P /run/seafile/server.pid \
              -p /run/seafile
            '';
          };
          preStart = ''
            if [ ! -f "${seafRoot}/server-setup" ]; then
                mkdir -p ${dataDir}/library-template
                mkdir -p ${ccnetDir}/{GroupMgr,misc,OrgMgr,PeerMgr}
                sqlite3 ${ccnetDir}/GroupMgr/groupmgr.db ".read ${cfg.seafilePackage}/share/seafile/sql/sqlite/groupmgr.sql"
                sqlite3 ${ccnetDir}/misc/config.db ".read ${cfg.seafilePackage}/share/seafile/sql/sqlite/config.sql"
                sqlite3 ${ccnetDir}/OrgMgr/orgmgr.db ".read ${cfg.seafilePackage}/share/seafile/sql/sqlite/org.sql"
                sqlite3 ${ccnetDir}/PeerMgr/usermgr.db ".read ${cfg.seafilePackage}/share/seafile/sql/sqlite/user.sql"
                sqlite3 ${dataDir}/seafile.db ".read ${cfg.seafilePackage}/share/seafile/sql/sqlite/seafile.sql"
                echo "${cfg.seafilePackage.version}-sqlite" > "${seafRoot}"/server-setup
            fi
            # checking for upgrades and handling them
            installedMajor=$(cat "${seafRoot}/server-setup" | cut -d"-" -f1 | cut -d"." -f1)
            installedMinor=$(cat "${seafRoot}/server-setup" | cut -d"-" -f1 | cut -d"." -f2)
            pkgMajor=$(echo "${cfg.seafilePackage.version}" | cut -d"." -f1)
            pkgMinor=$(echo "${cfg.seafilePackage.version}" | cut -d"." -f2)

            if [[ $installedMajor == $pkgMajor && $installedMinor == $pkgMinor ]]; then
               :
            elif [[ $installedMajor == 8 && $installedMinor == 0 && $pkgMajor == 9 && $pkgMinor == 0 ]]; then
                # Upgrade from 8.0 to 9.0
                sqlite3 ${dataDir}/seafile.db ".read ${pkgs.seahub}/scripts/upgrade/sql/9.0.0/sqlite3/seafile.sql"
                echo "${cfg.seafilePackage.version}-sqlite" > "${seafRoot}"/server-setup
            elif [[ $installedMajor == 9 && $installedMinor == 0 && $pkgMajor == 10 && $pkgMinor == 0 ]]; then
                # Upgrade from 9.0 to 10.0
                sqlite3 ${dataDir}/seafile.db ".read ${pkgs.seahub}/scripts/upgrade/sql/10.0.0/sqlite3/seafile.sql"
                echo "${cfg.seafilePackage.version}-sqlite" > "${seafRoot}"/server-setup
            else
                echo "Unsupported upgrade" >&2
                exit 1
            fi
          '';
        };

        seahub = {
          description = "Seafile Server Web Frontend";
          wantedBy = [ "seafile.target" ];
          partOf = [ "seafile.target" ];
          after = [ "network.target" "seaf-server.service" ];
          requires = [ "seaf-server.service" ];
          restartTriggers = [ seahubSettings ];
          environment = {
            PYTHONPATH = "${pkgs.seahub.pythonPath}:${pkgs.seahub}/thirdpart:${pkgs.seahub}";
            DJANGO_SETTINGS_MODULE = "seahub.settings";
            CCNET_CONF_DIR = ccnetDir;
            SEAFILE_CONF_DIR = dataDir;
            SEAFILE_CENTRAL_CONF_DIR = "/etc/seafile";
            SEAFILE_RPC_PIPE_PATH = "/run/seafile";
            SEAHUB_LOG_DIR = "/var/log/seafile";
          };
          serviceConfig = securityOptions // {
            User = "seafile";
            Group = "seafile";
            DynamicUser = true;
            RuntimeDirectory = "seahub";
            StateDirectory = "seafile";
            LogsDirectory = "seafile";
            ConfigurationDirectory = "seafile";
            ExecStart = ''
              ${pkgs.seahub.python.pkgs.gunicorn}/bin/gunicorn seahub.wsgi:application \
              --name seahub \
              --workers ${toString cfg.workers} \
              --log-level=info \
              --preload \
              --timeout=1200 \
              --limit-request-line=8190 \
              --bind unix:/run/seahub/gunicorn.sock
            '';
          };
          preStart = ''
            mkdir -p ${seahubDir}/media
            # Link all media except avatars
            for m in `find ${pkgs.seahub}/media/ -maxdepth 1 -not -name "avatars"`; do
              ln -sf $m ${seahubDir}/media/
            done
            if [ ! -e "${seafRoot}/.seahubSecret" ]; then
                ${pkgs.seahub.python}/bin/python ${pkgs.seahub}/tools/secret_key_generator.py > ${seafRoot}/.seahubSecret
                chmod 400 ${seafRoot}/.seahubSecret
            fi
            if [ ! -f "${seafRoot}/seahub-setup" ]; then
                # avatars directory should be writable
                install -D -t ${seahubDir}/media/avatars/ ${pkgs.seahub}/media/avatars/default.png
                install -D -t ${seahubDir}/media/avatars/groups ${pkgs.seahub}/media/avatars/groups/default.png
                # init database
                ${pkgs.seahub}/manage.py migrate
                # create admin account
                ${pkgs.expect}/bin/expect -c 'spawn ${pkgs.seahub}/manage.py createsuperuser --email=${cfg.adminEmail}; expect "Password: "; send "${cfg.initialAdminPassword}\r"; expect "Password (again): "; send "${cfg.initialAdminPassword}\r"; expect "Superuser created successfully."'
                echo "${pkgs.seahub.version}-sqlite" > "${seafRoot}/seahub-setup"
            fi
            if [ $(cat "${seafRoot}/seahub-setup" | cut -d"-" -f1) != "${pkgs.seahub.version}" ]; then
                # update database
                ${pkgs.seahub}/manage.py migrate
                echo "${pkgs.seahub.version}-sqlite" > "${seafRoot}/seahub-setup"
            fi
          '';
        };
      };
  };
}