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-module(fabric_doc_missing_revs).
-export([go/2]).
-include("fabric.hrl").
go(DbName, AllIdsRevs) ->
Workers = lists:map(fun({#shard{name=Name, node=Node} = Shard, IdsRevs}) ->
Ref = rexi:cast(Node, {fabric_rpc, get_missing_revs, [Name, IdsRevs]}),
Shard#shard{ref=Ref}
end, group_idrevs_by_shard(DbName, AllIdsRevs)),
ResultDict = dict:from_list([{Id, {nil,Revs}} || {Id, Revs} <- AllIdsRevs]),
Acc0 = {length(Workers), ResultDict},
fabric_util:recv(Workers, #shard.ref, fun handle_message/3, Acc0).
handle_message({rexi_DOWN, _, _, _}, _Worker, Acc0) ->
skip_message(Acc0);
handle_message({rexi_EXIT, _, _, _}, _Worker, Acc0) ->
skip_message(Acc0);
handle_message({ok, Results}, _Worker, {1, D0}) ->
D = update_dict(D0, Results),
{stop, dict:fold(fun force_reply/3, [], D)};
handle_message({ok, Results}, _Worker, {WaitingCount, D0}) ->
D = update_dict(D0, Results),
case dict:fold(fun maybe_reply/3, {stop, []}, D) of
continue ->
% still haven't heard about some Ids
{ok, {WaitingCount - 1, D}};
{stop, FinalReply} ->
{stop, FinalReply}
end.
force_reply(Id, {nil,Revs}, Acc) ->
% never heard about this ID, assume it's missing
[{Id, Revs} | Acc];
force_reply(_, [], Acc) ->
Acc;
force_reply(Id, Revs, Acc) ->
[{Id, Revs} | Acc].
maybe_reply(_, _, continue) ->
continue;
maybe_reply(_, {nil, _}, _) ->
continue;
maybe_reply(_, [], {stop, Acc}) ->
{stop, Acc};
maybe_reply(Id, Revs, {stop, Acc}) ->
{stop, [{Id, Revs} | Acc]}.
group_idrevs_by_shard(DbName, IdsRevs) ->
dict:to_list(lists:foldl(fun({Id, Revs}, D0) ->
lists:foldl(fun(Shard, D1) ->
dict:append(Shard, {Id, Revs}, D1)
end, D0, partitions:for_key(DbName,Id))
end, dict:new(), IdsRevs)).
update_dict(D0, KVs) ->
lists:foldl(fun({K,V}, D1) -> dict:store(K, V, D1) end, D0, KVs).
skip_message({1, Dict}) ->
{stop, dict:fold(fun force_reply/3, [], Dict)};
skip_message({WaitingCount, Dict}) ->
{ok, {WaitingCount-1, Dict}}.
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