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

with lib;

let

  cfg = config.programs.mercurial;

  iniFormat = pkgs.formats.ini { };

in {

  options = {
    programs.mercurial = {
      enable = mkEnableOption "Mercurial";

      package = mkOption {
        type = types.package;
        default = pkgs.mercurial;
        defaultText = literalExpression "pkgs.mercurial";
        description = "Mercurial package to install.";
      };

      userName = mkOption {
        type = types.str;
        description = "Default user name to use.";
      };

      userEmail = mkOption {
        type = types.str;
        description = "Default user email to use.";
      };

      aliases = mkOption {
        type = types.attrsOf types.anything;
        default = { };
        description = "Mercurial aliases to define.";
      };

      extraConfig = mkOption {
        type = types.either (types.attrsOf types.anything) types.lines;
        default = { };
        description = "Additional configuration to add.";
      };

      iniContent = mkOption {
        type = iniFormat.type;
        internal = true;
      };

      ignores = mkOption {
        type = types.listOf types.str;
        default = [ ];
        example = [ "*~" "*.swp" ];
        description = "List of globs for files to be globally ignored.";
      };

      ignoresRegexp = mkOption {
        type = types.listOf types.str;
        default = [ ];
        example = [ "^.*~$" "^.*\\.swp$" ];
        description =
          "List of regular expressions for files to be globally ignored.";
      };
    };
  };

  config = mkIf cfg.enable (mkMerge [
    {
      home.packages = [ cfg.package ];

      programs.mercurial.iniContent.ui = {
        username = cfg.userName + " <" + cfg.userEmail + ">";
      };

      xdg.configFile."hg/hgrc".source =
        iniFormat.generate "hgrc" cfg.iniContent;
    }

    (mkIf (cfg.ignores != [ ] || cfg.ignoresRegexp != [ ]) {
      programs.mercurial.iniContent.ui.ignore =
        "${config.xdg.configHome}/hg/hgignore_global";

      xdg.configFile."hg/hgignore_global".text = ''
        syntax: glob
      '' + concatStringsSep "\n" cfg.ignores + "\n" + ''
        syntax: regexp
      '' + concatStringsSep "\n" cfg.ignoresRegexp + "\n";
    })

    (mkIf (cfg.aliases != { }) {
      programs.mercurial.iniContent.alias = cfg.aliases;
    })

    (mkIf (lib.isAttrs cfg.extraConfig) {
      programs.mercurial.iniContent = cfg.extraConfig;
    })

    (mkIf (lib.isString cfg.extraConfig) {
      xdg.configFile."hg/hgrc".text = cfg.extraConfig;
    })
  ]);
}