Build tree from proplist with list keys

trees.erl

-module(trees).

-export([build_tree/1]).

%% @doc Builds a (proplist-based) tree from a proplist where each key
%% is a list of keys.
build_tree(Proplist) ->
    build_tree(Proplist, []).

build_tree([], Tree) ->
    Tree;
build_tree([{Keys, Value} | Proplist], Tree) ->
    build_tree(Proplist, insert_value(Keys, Value, Tree)).

insert_value([Key], Value, Tree) ->
    [{Key, Value} | Tree];
insert_value([Key | Keys], Value, Tree) ->
    Subtree = proplists:get_value(Key, Tree, []),
    update_value(Key, insert_value(Keys, Value, Subtree), Tree).

update_value(Key, Value, Proplist) ->
    [{Key, Value} | proplists:delete(Key, Proplist)].