{ lib, sLib, ... }:

let
  submodule =
    { config, ... }:
    {
      options = {
        default = lib.mkOption {
          type = lib.types.nullOr lib.types.str;
          default = null;
          example = "ddg";
          description = "The default search engine used in the address bar and search bar.";
        };

        engines = lib.mkOption {
          type = lib.types.attrsOf (lib.types.submodule engineSubmodule);
          default = { };
        };
      };
    };

  engineSubmodule =
    { name, ... }:
    {
      options = {
        name = lib.mkOption {
          type = lib.types.str;
          default = name;
        };

        searchUri = {
          base = lib.mkOption {
            type = lib.types.strMatching "[a-z]+://[-A-Za-z0-9.]+(:[0-9]+)?(/[^?]*)?";
          };

          params = lib.mkOption {
            type = lib.types.listOf (
              lib.types.submodule {
                options = {
                  key = lib.mkOption { type = lib.types.str; };
                  value = lib.mkOption { type = lib.types.str; };
                };
              }
            );
            default = [ ];
          };
        };

        method = lib.mkOption {
          type = lib.types.enum [
            "GET"
            "POST"
          ];
          default = "GET";
        };

        alias = lib.mkOption {
          type = lib.types.nullOr lib.types.str;
          default = null;
        };

        icon = lib.mkOption {
          type = lib.types.nullOr (
            lib.types.oneOf [
              lib.types.package
              lib.types.str
            ]
          );
          default = null;
        };
      };
    };

  buildPolicyFromEngine =
    {
      name,
      searchUri,
      method,
      alias,
      icon,
    }:
    let
      params = sLib.compose [
        (builtins.concatStringsSep "&")
        (builtins.map (x: "${x.key}=${x.value}"))
      ] searchUri.params;
    in
    {
      Name = name;
      URLTemplate =
        if method == "POST" then
          searchUri.base
        else if params == "" then
          searchUri.base
        else
          "${searchUri.base}?${params}";
      Method = method;
      ${if method == "POST" then "PostData" else null} = params;
      ${if icon != null then "IconURL" else null} = "file://${builtins.toString icon}";
      ${if alias != null then "Alias" else null} = alias;
    };
in
{
  options = {
    search = lib.mkOption {
      type = lib.types.submodule submodule;
      default = { };
      description = "Declarative search engine configuration.";
    };
  };

  process =
    { search, ... }:
    {
      policies.SearchEngines = {
        ${if search.default == null then null else "Default"} = search.default;
        Add = lib.mapAttrsToList (_: buildPolicyFromEngine) search.engines;
      };
    };
}