day28.erl

-module(solution).
-export([main/0]).

main() ->
    printContacts(sortContacts(filterContacts(createContacts(readAll())))).

readAll() ->
    readAll([], io:get_chars("", 4096)).
readAll(In, eof) ->
    [StringN|Lines] = string:tokens(lists:flatten(lists:reverse(In)), "\n"),
    {list_to_integer(StringN), Lines};
readAll(In, Data) ->
    readAll([Data|In], io:get_chars("", 4096)).

createContacts({N, Entries}) ->
    createContacts({N, Entries}, []).
createContacts({0, _Entries}, PhoneBook) ->
    PhoneBook;
createContacts({N, [Entry|Lines]}, PhoneBook) ->
    [Key, Value] = string:tokens(Entry, " "),
    createContacts({N-1, Lines}, lists:append([{Key, Value}], PhoneBook)).

filterContacts(Contacts) ->
    filterContacts(Contacts, []).

filterContacts([], Out) ->
    Out;
filterContacts([{Firstname, Email} | In], Out) ->
    case re:run(Email, "@gmail.com$") of
        {match, _} -> filterContacts(In, [Firstname | Out]);
        nomatch -> filterContacts(In, Out)
    end.

sortContacts(Contacts) ->
    lists:sort(Contacts).

printContacts(Contacts) ->
    lists:foreach(fun(Contact) -> io:fwrite("~s~n", [Contact]) end, Contacts).