-module(ts_entry).
-export([create_table/1, new/1, update/1, lookup/3, list/3]).

-include("ts_db_records.hrl").
-include_lib("stdlib/include/qlc.hrl").

create_table(TableOpts) ->
    mnesia:create_table(ts_entry,
        TableOpts ++ [{attributes, record_info(fields, ts_entry)},
                      {type, ordered_set}, {index, timestamp}]).

new(ER = #ts_entry()) ->
    {atmoic, NewRow) = mnesia:transaction(fun() ->
        {Username, TimelineId, _} = ER#ts_entry.ref,
        NextId = id_counter:next_counter(ts_entry_id),
        NewRow = ER#ts_entry{ref = {Username, TimelineId, NextId}},
        ok = mnesia:write(NewRow),
        NewRow end),
    {ok, NewRow}.

update(ER = #ts_entry()) ->
    
    % look for existing record
    case mnesia:dirty_read(ts_entry, ER#ts_entry.ref) of
        % record does not exist
        [] -> no_record;
        % record exists, update it
        [_Record] -> mnesia:dirty_write(ER)
    end.

lookup(Username, TimelineId, EntryId) ->
    case mnesia:dirty_read(ts_entry, {Username, TimelineId, EntryId}) of
        [] -> no_record;
        [Entry] -> Entry
    end.

list({Username, Timeline}, Start, Length)
when is_integer(Start) and is_integer(Length) ->
    ts_common:list(
        qlc:q([E || E <- mnesia:table(ts_entry),
                    E#ts_entry.ref =:= {Username, Timeline, _}]_,
            Start, Length).

list({Username, Timeline}, StartDateTime, EndDateTime) ->

    {atomic, Entries} = mnesia:transaction(fun() ->

        StartSeconds = calendar:datetime_to_gregorian_seconds(StartDateTime),
        EndSeconds = calendar:datetime_to_gregorian_seconds(EndDateTime),

        % create the query that will select these records
        Q = qlc:q([E || E <- mnesia:table(ts_entry),
                        E#ts_entry.timestamp >= StartSeconds,
                        E#ts_entry.timestamp < EndSeconds]),

        % sort by timestamp
        SortedQ = qlc:sort(Q, {order, fun(A, B) ->
            A#ts_entry.timestamp > B#ts_entry.timestamp end}),

        % return
        qlc:e(SortedQ)
    end),
    Entries.