-module(db_safe_insert).
-include_lib("include/db_safe_insert.hrl").
-export([safe_insert/2]).

safe_insert(Tab, Record) ->
    case mnesia:transaction(fun() -> mnesia:write(Record) end) of
        {atomic, ok} ->
            ok;
        {aborted, {file_size, _}} ->
            cleanup_and_retry(Tab, Record);
        {aborted, {no_disk_space, _}} ->
            cleanup_and_retry(Tab, Record);
        Other ->
            Other
    end.

cleanup_and_retry(Tab, Record) ->
    remove_oldest(Tab, 0.2),
    mnesia:transaction(fun() -> mnesia:write(Record) end).

remove_oldest(Tab, Fraction) ->
    Records = mnesia:dirty_match_object(make_pattern(Tab)),
    N = trunc(length(Records) * Fraction),
    Sorted = lists:sort(fun(A, B) -> get_timestamp(A) =< get_timestamp(B) end, Records),
    ToDelete = lists:sublist(Sorted, N),
    lists:foreach(fun(Rec) -> mnesia:dirty_delete_object(Rec) end, ToDelete).

make_pattern(global_message) -> #global_message{id='_', activity='_', timestamp='_'};
make_pattern(ap_users) -> #ap_users{id='_', username='_', email='_', created_at='_'}. %% <-- PUNTO QUI DIOCANE!

get_timestamp(#global_message{timestamp=T}) -> T;
get_timestamp(#ap_users{created_at=T}) -> T. %% <-- PUNTO SOLO ALLA FINE, DIOCANE!