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

with lib;
with import ../lib/dag.nix { inherit lib; };

let
  cfg = config.programs.offlineimap;

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

  # generates a script to fetch only a specific account
  genOfflineImapScript = {name, ...} @ account:
    pkgs.writeShellScriptBin "offlineimap-${name}" ''
      ${pkgs.offlineimap}/bin/offlineimap -a${account.name} $@
    '';

  localTypeStr = account:
    if account.flavor == "gmail" then "GmailMaildir" else "Maildir";

  remoteTypeStr = account:
    if account.flavor == "gmail" then "Gmail" else "IMAP";

  remoteHostStr = account:
    if account.imap.host != null then "remotehost = "+ account.imap.host else "";

  loginCommandStr = account:
    "remoteuser = ${account.userName}";

  passwordCommandStr = account:
  let
    arglist = concatMapStringsSep "," (x: "'" + toString x + "'") account.passwordCommand;
  in
  if account.passwordCommand != null then
  ''remotepasseval = get_pass("${account.name}", [${arglist}])''
  else "";

  postSyncHookStr = account:
    if (builtins.stringLength account.offlineimap.postSyncHookCommand > 0) then
        "postsynchook = ${account.offlineimap.postSyncHookCommand}"
    else if account.notmuch.enable then
        "postsynchook = notmuch new"
    else  "";

  sslStr = account:
  if account.imap.tls.enable then ''
    ssl = yes
    sslcacertfile = ${account.imap.tls.certificatesFile}
    ''
  else "ssl = no";

  accountStr = account: with account;
''
[Account ${name}]
localrepository = ${name}-local
remoterepository = ${name}-remote
${postSyncHookStr account}

[Repository ${name}-local]
type = ${localTypeStr account}
localfolders = ${account.maildir.absPath}

[Repository ${name}-remote]
type = ${remoteTypeStr account }
${remoteHostStr account}
${loginCommandStr account}
${if (account.imap.port or null) != null then "remoteport=${account.imap.port}" else ""}
${passwordCommandStr account}
realdelete = yes
maxconnections = 3
${sslStr account}

${account.offlineimap.extraConfig}
'';

  configFile = mailAccounts: ''
# Generated by home-manager
# see https://github.com/OfflineIMAP/offlineimap/blob/master/offlineimap.conf
# for an exhaustive list of options
[general]
accounts = gmail
maxsyncaccounts= 4
socktimeout = 10
pythonfile = $XDG_CONFIG_HOME/offlineimap/get_settings.py
metadata = $XDG_DATA_HOME/offlineimap
ui = ttyui

# user extraConfig if any
${cfg.extraConfig}

[mbnames]
enabled = yes
filename = $XDG_CONFIG_HOME/mutt/mailboxes
header = "mailboxes *\nmailboxes !\n"
peritem = mailboxes =%(accountname)s/%(foldername)s
sep = "\n"
footer = "\n"

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

in
{

  options = {
    programs.offlineimap = {
      enable = mkEnableOption "Offlineimap";

      pythonFile = mkOption {
        type = types.lines;
        default = ''
# generated by home-manager
import subprocess

def get_pass(service, cmd):
    res = subprocess.check_output(cmd, )
    return res
'';
        description = ''
          Python code that can then be used in other parts of the configuration.
        '';
      };

      extraConfig = mkOption {
        type = types.lines;
        default = ''
          # in daysA
          maxage=30
        '';
        description = ''
          Extra configuration lines added to configuration.
          You can add a [DEFAULT] section to provide defaults for all accounts.
        '';
      };
    };

    accounts.email.accounts = mkOption {
      options = [
        {
          offlineimap = {
            enable = mkEnableOption "OfflineIMAP";

            extraConfig = mkOption {
              type = types.lines;
              default = "";
              description = ''
                Extra configuration lines added on a per-account basis.
                '';
            };

            postSyncHookCommand = mkOption {
              type = types.lines;
              default = "";
              description = "command to run after fetching new mails";
            };
          };
        }
      ];
    };
  };

  config = mkIf cfg.enable {

    home.packages =  [
      pkgs.offlineimap
    ] ++ (
      map genOfflineImapScript ( accounts )
    );

    xdg.configFile."offlineimap/get_settings.py".text = cfg.pythonFile;

    xdg.configFile."offlineimap/config".text = configFile accounts;
  };
}