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

with lib;

let

  cfg = config.programs.msmtp;

  msmtpAccounts = filter (a: a.msmtp.enable)
    (attrValues config.accounts.email.accounts);

  onOff = p: if p then "on" else "off";

  accountStr = account: with account;
    concatStringsSep "\n" (
      [ "account ${name}" ]
      ++ mapAttrsToList (n: v: n + " " + v) (
        {
          host = smtp.host;
          from = address;
          auth = "on";
          user = userName;
          tls = onOff smtp.tls.enable;
          tls_starttls = onOff smtp.tls.useStartTls;
          tls_trust_file = smtp.tls.certificatesFile;
        }
        // optionalAttrs (smtp.port != null) {
          port = toString smtp.port;
        }
        // optionalAttrs (passwordCommand != null) {
          # msmtp requires the password to finish with a newline.
          passwordeval = ''${pkgs.bash}/bin/bash -c "${toString passwordCommand}; echo"'';
        }
        // msmtp.extraConfig
      )
      ++ optional primary "\naccount default : ${name}"
    );

  configFile = mailAccounts: ''
    # Generated by Home Manager.

    ${cfg.extraConfig}

    ${concatStringsSep "\n\n" (map accountStr mailAccounts)}
  '';

in

{

  options = {
    programs.msmtp = {
      enable = mkEnableOption "msmtp";

      extraConfig = mkOption {
        type = types.lines;
        default = "";
        description = ''
          Extra configuration lines to add to <filename>~/.msmtprc</filename>.
          See <link xlink:href="https://marlam.de/msmtp/msmtprc.txt"/> for examples.
        '';
      };
    };
  };

  config = mkIf cfg.enable {
    home.packages = [ pkgs.msmtp ];

    xdg.configFile."msmtp/config".text = configFile msmtpAccounts;

    home.sessionVariables =  {
      MSMTP_QUEUE = "${config.xdg.dataHome}/msmtp/queue";
      MSMTP_LOG = "${config.xdg.dataHome}/msmtp/queue.log";
    };
  };
}