-module(kvs_rocks).
-include("backend.hrl").
-include("kvs.hrl").
-include("metainfo.hrl").
-include_lib("stdlib/include/qlc.hrl").
-export(?BACKEND).
-export([ref/0,cut/8,next/8,prev/8,prev2/8,next2/8,bt/1,key/2,key/1,fd/1]).
-export([seek_it/1, move_it/3]).

e(X,Y)     -> element(X,Y).
bt([])     -> [];
bt(X)      -> binary_to_term(X).
tb([])     -> [];
tb(T) when is_list(T) -> list_to_binary(T);
tb(T) when is_atom(T) -> atom_to_binary(T);
tb(T) when is_binary(T) -> T;
tb(T)      -> term_to_binary(T).

key(R)     when is_tuple(R) andalso tuple_size(R) > 1 -> key(e(1,R), e(2,R));
key(R)     -> key(R,[]).
key(Tab,R) when is_tuple(R) andalso tuple_size(R) > 1 -> key(Tab, e(2,R));
key(Tab,R) -> iolist_to_binary([lists:join(<<"/">>, lists:flatten([<<>>, tb(Tab), tb(R)]))]).

fd(Key) ->
  B = lists:reverse(binary:split(tb(Key), [<<"/">>, <<"//">>], [global, trim_all])),
  B1 = lists:reverse(case B of [] -> [];[X] -> [X];[_|T] -> T end),
  iolist_to_binary(lists:join(<<"/">>, [<<>>]++B1)).

o(<<>>,FK,_,_) -> {ok,FK,[],[]};
o(Key,FK,Dir,Fx) ->
  S = size(FK),

  Sheaf = fun (F,K,H,V,Acc) when binary_part(K,{0,S}) == FK -> {F(H,Dir),H,[V|Acc]};
                                              (_,K,H,V,Acc) -> close_it(H),
                                                               throw({ok,fd(K),bt(V),[bt(A1)||A1<-Acc]}) end,

  It = fun(F,{ok,H})            -> {F(H,{seek,Key}),H};
          (F,{{ok,K,V},H})      -> Sheaf(F,K,H,V,[]);
          (F,{{ok,K,V},H,A})    -> Sheaf(F,K,H,V,A);
          (_,{{error,_},H,Acc}) -> {{ok,[],[]},H,Acc};
          (F,{R,O})             -> F(R,O);
          (F,H)                 -> F(H) end,
  catch case lists:foldl(It, {ref(),[]}, Fx) of
    {{ok,K,Bin},_,A} when binary_part(K,{0,S}) == FK  -> {ok,fd(K),bt(Bin),[bt(A1)||A1<-A]};
    {{ok,K,Bin},_,_}                                  -> {ok,fd(K),bt(Bin),[]};
    {{ok,K,Bin},_}                                    -> {ok,fd(K),bt(Bin),[]}
  end.

start()    -> ok.
stop()     -> ok.
destroy()  -> rocksdb:destroy(application:get_env(kvs,rocks_name,"rocksdb"), []).
version()  -> {version,"KVS ROCKSDB"}.
dir()      -> [].
leave() -> case ref() of [] -> skip; X -> rocksdb:close(X), application:set_env(kvs,rocks_ref,[]), ok end.
join(_) -> application:start(rocksdb),
           leave(), {ok, Ref} = rocksdb:open(application:get_env(kvs,rocks_name,"rocksdb"), [{create_if_missing, true}]),
           initialize(),
           application:set_env(kvs,rocks_ref,Ref).
initialize() -> [ kvs:initialize(kvs_rocks,Module) || Module <- kvs:modules() ].
ref() -> application:get_env(kvs,rocks_ref,[]).
index(_,_,_) -> [].

close_it(H) -> try rocksdb:iterator_close(H) catch error:badarg -> ok end.
seek_it(K) -> o(K,K,ok,[fun rocksdb:iterator/2,fun rocksdb:iterator_move/2]).
move_it(K,FK,Dir) -> o(K,FK,Dir,[fun rocksdb:iterator/2,fun rocksdb:iterator_move/2,fun rocksdb:iterator_move/2]).

get(Tab, Key) ->
    case rocksdb:get(ref(), key(Tab,Key), []) of
         not_found -> {error,not_found};
         {ok,Bin} -> {ok,bt(Bin)} end.

put(Records) when is_list(Records) -> lists:map(fun(Record) -> put(Record) end, Records);
put(Record) -> rocksdb:put(ref(), key(Record), term_to_binary(Record), [{sync,true}]).
delete(Feed, Id) -> rocksdb:delete(ref(), key(Feed,Id), []).

count(_) -> 0.
all(R) -> {ok,I} = rocksdb:iterator(ref(), []),
           Key = key(R),
           First = rocksdb:iterator_move(I, {seek,Key}),
           lists:reverse(next(I,Key,size(Key),First,[],[],-1,0)).

next(I,Key,S,A,X,T,N,C) -> {_,L} = next2(I,Key,S,A,X,T,N,C), L.
prev(I,Key,S,A,X,T,N,C) -> {_,L} = prev2(I,Key,S,A,X,T,N,C), L.

shd([]) -> [];
shd(X) -> hd(X).

next2(_,Key,_,_,X,T,N,C) when C == N -> {shd(lists:reverse(T)),T};
next2(I,Key,S,{ok,A,X},_,T,N,C) -> next2(I,Key,S,A,X,T,N,C);
next2(_,Key,_,{error,_},X,T,_,_) -> {shd(lists:reverse(T)),T};
next2(I,Key,S,A,X,T,N,C) when size(A) > S ->
     case binary:part(A, 0, S) of Key ->
          next2(I, Key, S, rocksdb:iterator_move(I, next), [], [bt(X)|T], N, C + 1);
          _ -> {shd(lists:reverse(T)),T} end;
next2(_,Key,_,{ok,A,_},X,T,_,_) -> {bt(X),T};
next2(_,Key,_,_,X,T,_,_) -> {shd(lists:reverse(T)),T}.

prev2(_,Key,_,_,X,T,N,C) when C == N -> {bt(X),T};
prev2(I,Key,S,{ok,A,X},_,T,N,C) -> prev2(I,Key,S,A,X,T,N,C);
prev2(_,Key,_,{error,_},X,T,_,_) -> {bt(X),T};
prev2(I,Key,S,A,X,T,N,C) when size(A) > S ->
     case binary:part(A, 0, S) of Key ->
          prev2(I, Key, S, rocksdb:iterator_move(I, prev), [], [bt(X)|T], N, C + 1);
          _ -> {shd(lists:reverse(T)),T} end;
prev2(_,Key,_,{ok,A,_},X,T,_,_) -> {bt(X),T};
prev2(_,Key,_,_,X,T,_,_) -> {bt(X),T}.

cut(_,_,_,_,_,_,N,C) when C == N -> C;
cut(I,Key,S,{ok,A,X},_,T,N,C) -> prev(I,Key,S,A,X,T,N,C);
cut(_,___,_,{error,_},_,_,_,C) -> C;
cut(I,Key,S,A,_,_,N,C) when size(A) > S ->
     case binary:part(A,0,S) of Key ->
          rocksdb:delete(ref(), A, []),
          Next = rocksdb:iterator_move(I, prev),
          cut(I,Key, S, Next, [], A, N, C + 1);
                                  _ -> C end;
cut(_,_,_,_,_,_,_,C) -> C.

seq(_,_) ->
  case os:type() of
       {win32,nt} -> {Mega,Sec,Micro} = erlang:timestamp(), integer_to_list((Mega*1000000+Sec)*1000000+Micro);
                _ -> erlang:integer_to_list(element(2,hd(lists:reverse(erlang:system_info(os_monotonic_time_source)))))
  end.

create_table(_,_) -> [].
add_table_index(_, _) -> ok.
dump() -> ok.