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

with lib;

let

  cfg = config.programs.notmuch;

  mkIniKeyValue = key: value:
    let
      tweakVal = v:
        if isString v then
          v
        else if isList v then
          concatMapStringsSep ";" tweakVal v
        else if isBool v then
          (if v then "true" else "false")
        else
          toString v;
    in "${key}=${tweakVal value}";

  notmuchIni = recursiveUpdate {
    database = { path = config.accounts.email.maildirBasePath; };

    maildir = { synchronize_flags = cfg.maildir.synchronizeFlags; };

    new = {
      ignore = cfg.new.ignore;
      tags = cfg.new.tags;
    };

    user = let
      accounts = filter (a: a.notmuch.enable)
        (attrValues config.accounts.email.accounts);
      primary = filter (a: a.primary) accounts;
      secondaries = filter (a: !a.primary) accounts;
    in {
      name = catAttrs "realName" primary;
      primary_email = catAttrs "address" primary;
      other_email = catAttrs "aliases" primary ++ catAttrs "address" secondaries
        ++ catAttrs "aliases" secondaries;
    };

    search = { exclude_tags = cfg.search.excludeTags; };
  } cfg.extraConfig;

in {
  options = {
    programs.notmuch = {
      enable = mkEnableOption "Notmuch mail indexer";

      new = mkOption {
        type = types.submodule {
          options = {
            ignore = mkOption {
              type = types.listOf types.str;
              default = [ ];
              description = ''
                A list to specify files and directories that will not be
                searched for messages by {command}`notmuch new`.
              '';
            };

            tags = mkOption {
              type = types.listOf types.str;
              default = [ "unread" "inbox" ];
              example = [ "new" ];
              description = ''
                A list of tags that will be added to all messages
                incorporated by {command}`notmuch new`.
              '';
            };
          };
        };
        default = { };
        description = ''
          Options related to email processing performed by
          {command}`notmuch new`.
        '';
      };

      extraConfig = mkOption {
        type = types.attrsOf (types.attrsOf types.str);
        default = { };
        description = ''
          Options that should be appended to the notmuch configuration file.
        '';
      };

      hooks = {
        preNew = mkOption {
          type = types.lines;
          default = "";
          example = "mbsync --all";
          description = ''
            Bash statements run before scanning or importing new
            messages into the database.
          '';
        };

        postNew = mkOption {
          type = types.lines;
          default = "";
          example = ''
            notmuch tag +nixos -- tag:new and from:nixos1@discoursemail.com
          '';
          description = ''
            Bash statements run after new messages have been imported
            into the database and initial tags have been applied.
          '';
        };

        postInsert = mkOption {
          type = types.lines;
          default = "";
          description = ''
            Bash statements run after a message has been inserted
            into the database and initial tags have been applied.
          '';
        };
      };

      maildir = {
        synchronizeFlags = mkOption {
          type = types.bool;
          default = true;
          description = ''
            Whether to synchronize Maildir flags.
          '';
        };
      };

      search = {
        excludeTags = mkOption {
          type = types.listOf types.str;
          default = [ "deleted" "spam" ];
          example = [ "trash" "spam" ];
          description = ''
            A  list  of  tags  that  will be excluded from search results by
            default. Using an excluded tag in a  query  will  override  that
            exclusion.
          '';
        };
      };
    };

    accounts.email.accounts = mkOption {
      type = with types;
        attrsOf (submodule {
          options.notmuch.enable = mkEnableOption "notmuch indexing";
        });
    };
  };

  config = mkIf cfg.enable {
    assertions = [
      {
        assertion = notmuchIni.user.name != [ ];
        message = "notmuch: Must have a user name set.";
      }
      {
        assertion = notmuchIni.user.primary_email != [ ];
        message = "notmuch: Must have a user primary email address set.";
      }
    ];

    home.packages = [ pkgs.notmuch ];

    home.sessionVariables = {
      NOTMUCH_CONFIG = "${config.xdg.configHome}/notmuch/default/config";
      NMBGIT = "${config.xdg.dataHome}/notmuch/nmbug";
    };

    xdg.configFile = let
      hook = name: cmds: {
        "notmuch/default/hooks/${name}".source = pkgs.writeShellScript name ''
          export PATH="${pkgs.notmuch}/bin''${PATH:+:}$PATH"
          export NOTMUCH_CONFIG="${config.xdg.configHome}/notmuch/default/config"
          export NMBGIT="${config.xdg.dataHome}/notmuch/nmbug"

          ${cmds}
        '';
      };
    in {
      "notmuch/default/config".text =
        let toIni = generators.toINI { mkKeyValue = mkIniKeyValue; };
        in ''
          # Generated by Home Manager.

        '' + toIni notmuchIni;
    }
    // optionalAttrs (cfg.hooks.preNew != "") (hook "pre-new" cfg.hooks.preNew)
    // optionalAttrs (cfg.hooks.postNew != "")
    (hook "post-new" cfg.hooks.postNew)
    // optionalAttrs (cfg.hooks.postInsert != "")
    (hook "post-insert" cfg.hooks.postInsert);
  };
}