-module(fabric_db_info).

-export([go/1]).

-include("fabric.hrl").
-include_lib("mem3/include/mem3.hrl").

go(DbName) ->
    Shards = mem3:shards(DbName),
    Workers = fabric_util:submit_jobs(Shards, get_db_info, []),
    Acc0 = {fabric_dict:init(Workers, nil), []},
    fabric_util:recv(Workers, #shard.ref, fun handle_message/3, Acc0).

handle_message({ok, Info}, #shard{dbname=Name} = Shard, {Counters, Acc}) ->
    case fabric_dict:lookup_element(Shard, Counters) of
    undefined ->
        % already heard from someone else in this range
        {ok, {Counters, Acc}};
    nil ->
        C1 = fabric_dict:store(Shard, ok, Counters),
        C2 = fabric_view:remove_overlapping_shards(Shard, C1),
        case fabric_dict:any(nil, C2) of
        true ->
            {ok, {C2, [Info|Acc]}};
        false ->
            {stop, [{db_name,Name}|merge_results(lists:flatten([Info|Acc]))]}
        end
    end;
handle_message(_, _, Acc) ->
    {ok, Acc}.

merge_results(Info) ->
    Dict = lists:foldl(fun({K,V},D0) -> orddict:append(K,V,D0) end,
        orddict:new(), Info),
    orddict:fold(fun
        (doc_count, X, Acc) ->
            [{doc_count, lists:sum(X)} | Acc];
        (doc_del_count, X, Acc) ->
            [{doc_del_count, lists:sum(X)} | Acc];
        (update_seq, X, Acc) ->
            [{update_seq, lists:sum(X)} | Acc];
        (purge_seq, X, Acc) ->
            [{purge_seq, lists:sum(X)} | Acc];
        (compact_running, X, Acc) ->
            [{compact_running, lists:member(true, X)} | Acc];
        (disk_size, X, Acc) ->
            [{disk_size, lists:sum(X)} | Acc];
        (disk_format_version, X, Acc) ->
            [{disk_format_version, lists:max(X)} | Acc];
        (_, _, Acc) ->
            Acc
    end, [{instance_start_time, <<"0">>}], Dict).