1 files changed, 78 insertions, 0 deletions
diff --git a/src/xdg_pipe_menu_renderer.erl b/src/xdg_pipe_menu_renderer.erl
new file mode 100644
index 0000000..c94fe83
--- /dev/null
+++ b/src/xdg_pipe_menu_renderer.erl
@@ -0,0 +1,78 @@
+%%%-------------------------------------------------------------------
+%% @doc Renders parsed desktop entries as an Openbox pipe menu.
+%%
+%% Given a list of `#desktop_entry{}' records, produces the XML that
+%% Openbox expects on stdout from a pipe menu: one `<menu>' submenu
+%% per category, each containing an `<item>' per visible entry in
+%% that category (entries with `hidden = true' are dropped). An entry
+%% belonging to several categories appears in each of their submenus;
+%% an entry with no categories is placed in a catch-all `Other'
+%% submenu. Categories are sorted case-insensitively, and entries
+%% within a submenu are sorted case-insensitively by name.
+%% @end
+%%%-------------------------------------------------------------------
+
+-module(xdg_pipe_menu_renderer).
+
+-include("xdg_pipe_menu.hrl").
+
+-export([render/1]).
+
+-define(OTHER_CATEGORY, <<"Other">>).
+
+-spec render([#desktop_entry{}]) -> binary().
+render(Entries) ->
+    Visible = [E || E <- Entries, not E#desktop_entry.hidden],
+    Grouped = group_by_category(Visible),
+    Categories = lists:sort(fun category_lt/2, maps:keys(Grouped)),
+    Menu = {openbox_pipe_menu, [], submenus_content(Categories, Grouped)},
+    Xml = xmerl:export_simple(
+        [Menu],
+        xmerl_xml,
+        [{prolog, ["<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"]}]
+    ),
+    iolist_to_binary([Xml, "\n"]).
+
+group_by_category(Entries) ->
+    lists:foldl(fun add_entry_to_categories/2, #{}, Entries).
+
+add_entry_to_categories(#desktop_entry{categories = []} = E, Acc) ->
+    add_entry_to_category(?OTHER_CATEGORY, E, Acc);
+add_entry_to_categories(#desktop_entry{categories = Cats} = E, Acc) ->
+    lists:foldl(fun(Cat, Acc0) -> add_entry_to_category(Cat, E, Acc0) end, Acc, Cats).
+
+add_entry_to_category(Cat, E, Acc) ->
+    maps:update_with(Cat, fun(Es) -> [E | Es] end, [E], Acc).
+
+category_lt(A, B) -> string:lowercase(A) =< string:lowercase(B).
+
+by_name(#desktop_entry{name = A}, #desktop_entry{name = B}) ->
+    string:lowercase(A) =< string:lowercase(B).
+
+submenus_content(Categories, Grouped) ->
+    lists:foldr(
+        fun(Cat, Acc) -> ["\n  ", submenu_element(Cat, Grouped) | Acc] end, ["\n"], Categories
+    ).
+
+submenu_element(Cat, Grouped) ->
+    Entries = lists:sort(fun by_name/2, maps:get(Cat, Grouped)),
+    {menu, [{id, Cat}, {label, Cat}], items_content(Entries)}.
+
+items_content(Entries) ->
+    lists:foldr(fun(E, Acc) -> ["\n    ", item_element(E) | Acc] end, ["\n  "], Entries).
+
+item_element(#desktop_entry{name = Name, exec = Exec, icon = Icon}) ->
+    {item, item_attrs(Name, Icon), [
+        "\n      ",
+        {action, [{name, <<"Execute">>}], [
+            "\n        ",
+            {command, [], [text(Exec)]},
+            "\n      "
+        ]},
+        "\n    "
+    ]}.
+
+item_attrs(Name, undefined) -> [{label, Name}];
+item_attrs(Name, Icon) -> [{label, Name}, {icon, Icon}].
+
+text(Bin) -> unicode:characters_to_list(Bin).