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

with lib;
with builtins;

let

  cfg = config.programs.astroid;

  astroidAccounts =
    filterAttrs
      (n: v: v.astroid.enable)
      config.accounts.email.accounts;

  boolOpt = b: if b then "true" else "false";

  accountAttr = account: with account; {
    email = address;
    name = realName;
    sendmail = astroid.sendMailCommand;
    additional_sent_tags = "";
    default = boolOpt primary;
    save_drafts_to = "${maildir.absPath}/${folders.drafts}";
    save_sent = "true";
    save_sent_to = "${maildir.absPath}/${folders.sent}";
    select_query = "";
  }
  // optionalAttrs (signature.showSignature != "none") {
    signature_attach = boolOpt (signature.showSignature == "attach");
    signature_default_on = boolOpt (signature.showSignature != "none");
    signature_file = pkgs.writeText "signature.txt" signature.text;
    signature_file_markdown = "false";
    signature_separate = "true";  # prepends '--\n' to the signature
  }
  // optionalAttrs (gpg != null) {
    always_gpg_sign = boolOpt gpg.signByDefault;
    gpgkey = gpg.key;
  }
  // astroid.extraConfig;

  # See https://github.com/astroidmail/astroid/wiki/Configuration-Reference
  configFile = mailAccounts:
    let
      template = fromJSON (readFile ./astroid-config-template.json);
      astroidConfig = foldl' recursiveUpdate template [
        {
          astroid.notmuch_config = "${config.xdg.configHome}/notmuch/notmuchrc";
          accounts = mapAttrs (n: accountAttr) astroidAccounts;
          crypto.gpg.path = "${pkgs.gnupg}/bin/gpg";
        }
        cfg.extraConfig
        cfg.externalEditor
      ];
    in
      builtins.toJSON astroidConfig;

in

{
  options = {
    programs.astroid = {
      enable = mkEnableOption "Astroid";

      pollScript = mkOption {
        type = types.str;
        default = "";
        example = "mbsync gmail";
        description = ''
          Script to run to fetch/update mails.
        '';
      };

      externalEditor = mkOption {
        type = types.nullOr types.str;
        default = null;
        # Converts it into JSON that can be merged into the configuration.
        apply = cmd:
          optionalAttrs (cmd != null) {
            editor = {
              "external_editor" = "true";
              "cmd" = cmd;
            };
          };
        example = "nvim-qt -- -c 'set ft=mail' '+set fileencoding=utf-8' '+set ff=unix' '+set enc=utf-8' '+set fo+=w' %1";
        description = ''
          You can use <code>%1</code>, <code>%2</code>, and
          <code>%3</code> to refer respectively to:
          <orderedlist numeration="arabic">
            <listitem><para>file name</para></listitem>
            <listitem><para>server name</para></listitem>
            <listitem><para>socket ID</para></listitem>
          </orderedlist>
          See <link xlink:href='https://github.com/astroidmail/astroid/wiki/Customizing-editor' />.
        '';
      };

      extraConfig = mkOption {
        type = types.attrs;
        default = {};
        example = { poll.interval = 0; };
        description = ''
          JSON config that will override the default Astroid configuration.
        '';
      };
    };
  };

  config = mkIf cfg.enable {
    assertions = [
      {
        assertion = config.programs.notmuch.maildir.synchronizeFlags;
        message = "The astroid module requires"
          + " 'programs.notmuch.maildir.synchronizeFlags = true'.";
      }
    ];

    home.packages =  [ pkgs.astroid ];

    xdg.configFile."astroid/config".source =
      pkgs.runCommand "out.json"
        {
          json = configFile astroidAccounts;
          preferLocalBuild = true;
          allowSubstitutes = false;
        }
        ''
          echo -n "$json" | ${pkgs.jq}/bin/jq . > $out
        '';

    xdg.configFile."astroid/poll.sh" = {
      executable = true;
      text = ''
        # Generated by Home Manager

        ${cfg.pollScript}
      '';
    };
  };
}