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

with lib;

let

  cfg = config.services.mlmmj;
  stateDir = "/var/lib/mlmmj";
  spoolDir = "/var/spool/mlmmj";
  listDir = domain: list: "${spoolDir}/${domain}/${list}";
  listCtl = domain: list: "${listDir domain list}/control";
  transport = domain: list: "${domain}--${list}@local.list.mlmmj mlmmj:${domain}/${list}";
  virtual = domain: list: "${list}@${domain} ${domain}--${list}@local.list.mlmmj";
  alias = domain: list: "${list}: \"|${pkgs.mlmmj}/bin/mlmmj-receive -L ${listDir domain list}/\"";
  subjectPrefix = list: "[${list}]";
  listAddress = domain: list: "${list}@${domain}";
  customHeaders = domain: list: [ "List-Id: ${list}" "Reply-To: ${list}@${domain}" ];
  footer = domain: list: "To unsubscribe send a mail to ${list}+unsubscribe@${domain}";
  createList = d: l: ''
    ${pkgs.coreutils}/bin/mkdir -p ${listCtl d l}
    echo ${listAddress d l} > ${listCtl d l}/listadress
    echo "${lib.concatStringsSep "\n" (customHeaders d l)}" > ${listCtl d l}/customheaders
    echo ${footer d l} > ${listCtl d l}/footer
    echo ${subjectPrefix l} > ${listCtl d l}/prefix
  '';
in

{

  ###### interface

  options = {

    services.mlmmj = {

      enable = mkOption {
        type = types.bool;
        default = false;
        description = "Enable mlmmj";
      };

      user = mkOption {
        type = types.str;
        default = "mlmmj";
        description = "mailinglist local user";
      };

      group = mkOption {
        type = types.str;
        default = "mlmmj";
        description = "mailinglist local group";
      };

      listDomain = mkOption {
        type = types.str;
        default = "localhost";
        description = "Set the mailing list domain";
      };

      mailLists = mkOption {
        type = types.listOf types.str;
        default = [];
        description = "The collection of hosted maillists";
      };

    };

  };

  ###### implementation

  config = mkIf cfg.enable {

    users.extraUsers = singleton {
      name = cfg.user;
      description = "mlmmj user";
      home = stateDir;
      createHome = true;
      uid = config.ids.uids.mlmmj;
      group = cfg.group;
      useDefaultShell = true;
    };

    users.extraGroups = singleton {
      name = cfg.group;
      gid = config.ids.gids.mlmmj;
    };

    services.postfix = {
      enable = true;
      recipientDelimiter= "+";
      extraMasterConf = ''
        mlmmj unix - n n - - pipe flags=ORhu user=mlmmj argv=${pkgs.mlmmj}/bin/mlmmj-receive -F -L ${spoolDir}/$nexthop
      '';

      extraAliases = concatMapStrings (alias cfg.listDomain) cfg.mailLists;

      extraConfig = ''
        transport_maps = hash:${stateDir}/transports
        virtual_alias_maps = hash:${stateDir}/virtuals
        propagate_unmatched_extensions = virtual
      '';
    };

    environment.systemPackages = [ pkgs.mlmmj ];

    system.activationScripts.mlmmj = ''
          ${pkgs.coreutils}/bin/mkdir -p ${stateDir} ${spoolDir}/${cfg.listDomain}
          ${pkgs.coreutils}/bin/chown -R ${cfg.user}:${cfg.group} ${spoolDir}
          ${lib.concatMapStrings (createList cfg.listDomain) cfg.mailLists}
          echo ${lib.concatMapStrings (virtual cfg.listDomain) cfg.mailLists} > ${stateDir}/virtuals
          echo ${cfg.listDomain} mailman: > ${stateDir}/transports
          echo ${lib.concatMapStrings (transport cfg.listDomain) cfg.mailLists} >> ${stateDir}/transports
    '';

    systemd.services."mlmmj-maintd" = {
      description = "mlmmj maintenance daemon";
      wantedBy = [ "multi-user.target" ];

      serviceConfig = {
        User = cfg.user;
        Group = cfg.group;
        ExecStart = "${pkgs.mlmmj}/bin/mlmmj-maintd -F -d ${spoolDir}/${cfg.listDomain}";
      };
    };

  };

}