-module(fabric_rpc).

-export([get_db_info/1, get_doc_count/1, get_update_seq/1]).
-export([open_doc/3, open_revs/4, get_missing_revs/2, update_docs/3]).
-export([all_docs/2, changes/3, map_view/4, reduce_view/4, group_info/2]).

-include("fabric.hrl").

-record (view_acc, {
    db,
    limit,
    include_docs,
    offset = nil,
    total_rows,
    reduce_fun = fun couch_db:enum_docs_reduce_to_count/1,
    stop_fun,
    group_level = 0
}).

%% rpc endpoints
%%  call to with_db will supply your M:F with a #db{} and then remaining args

all_docs(DbName, #view_query_args{keys=nil} = QueryArgs) ->
    {ok, Db} = couch_db:open(DbName, []),
    #view_query_args{
        start_key = StartKey,
        start_docid = StartDocId,
        limit = Limit,
        skip = Skip,
        include_docs = IncludeDocs,
        direction = Dir
    } = QueryArgs,
    StartId = if is_binary(StartKey) -> StartKey; true -> StartDocId end,
    {ok, Total} = couch_db:get_doc_count(Db),
    Acc0 = #view_acc{
        db = Db,
        include_docs = IncludeDocs,
        limit = Limit+Skip,
        total_rows = Total,
        stop_fun = all_docs_stop_fun(QueryArgs)
    },
    Options = [{start_key, StartId}, {dir, Dir}],
    {ok, _, Acc} = couch_db:enum_docs(Db, fun view_fold/3, Acc0, Options),
    final_response(Total, Acc#view_acc.offset).

changes(DbName, Args0, StartSeq) ->
    #changes_args{style=Style, dir=Dir} = Args0,
    case couch_db:open(DbName, []) of
    {ok, Db} ->
        % couch code has a MochiReq for 2nd argument, ick
        Args = Args0#changes_args{
            filter = couch_changes:make_filter_fun(Args0, nil, Db)
        },
        Enum = fun changes_enumerator/2,
        Opts = [{dir,Dir}],
        Acc0 = {Db, StartSeq, Args},
        try
            {ok, {_, LastSeq, _}} =
                couch_db:changes_since(Db, Style, StartSeq, Enum, Opts, Acc0),
            rexi:reply({complete, LastSeq})
        after
            couch_db:close(Db)
        end;
    Error ->
        rexi:reply(Error)
    end.

map_view(DbName, DDoc, ViewName, QueryArgs) ->
    {ok, Db} = couch_db:open(DbName, []),
    #view_query_args{
        start_key = StartKey,
        start_docid = StartDocId,
        limit = Limit,
        skip = Skip,
        keys = Keys,
        include_docs = IncludeDocs,
        direction = Dir,
        stale = Stale,
        view_type = ViewType
    } = QueryArgs,
    Start = {StartKey, StartDocId},
    MinSeq = if Stale == ok -> 0; true -> couch_db:get_update_seq(Db) end,
    Group0 = couch_view_group:design_doc_to_view_group(Db, DDoc),
    {ok, Pid} = gen_server:call(couch_view, {get_group_server, DbName, Group0}),
    {ok, Group} = couch_view_group:request_group(Pid, MinSeq),
    View = fabric_view:extract_view(Pid, ViewName, Group#group.views, ViewType),
    {ok, Total} = couch_view:get_row_count(View),
    Acc0 = #view_acc{
        db = Db,
        include_docs = IncludeDocs,
        limit = Limit+Skip,
        total_rows = Total,
        reduce_fun = fun couch_view:reduce_to_count/1,
        stop_fun = default_stop_fun(QueryArgs)
    },
    case Keys of
    nil ->
        Options = [{start_key, Start}, {dir, Dir}],
        {ok, _, Acc} = couch_view:fold(View, fun view_fold/3, Acc0, Options);
    _ ->
        Acc = lists:foldl(fun(Key, AccIn) ->
            KeyStart = {Key, StartDocId},
            KeyStop = default_stop_fun(QueryArgs#view_query_args{start_key=Key,
                end_key=Key}),
            Options = [{start_key, KeyStart}, {dir, Dir}],
            {_Go, _, Out} = couch_view:fold(View, fun view_fold/3,
                AccIn#view_acc{stop_fun = KeyStop}, Options),
            Out
        end, Acc0, Keys)
    end,
    final_response(Total, Acc#view_acc.offset).

reduce_view(DbName, Group0, ViewName, QueryArgs) ->
    {ok, Db} = couch_db:open(DbName, []),
    #view_query_args{
        start_key = StartKey,
        start_docid = StartDocId,
        end_key = EndKey,
        end_docid = EndDocId,
        group_level = GroupLevel,
        limit = Limit,
        skip = Skip,
        keys = Keys,
        direction = Dir,
        stale = Stale
    } = QueryArgs,
    GroupFun = group_rows_fun(GroupLevel),
    MinSeq = if Stale == ok -> 0; true -> couch_db:get_update_seq(Db) end,
    {ok, Pid} = gen_server:call(couch_view, {get_group_server, DbName, Group0}),
    {ok, #group{views=Views, def_lang=Lang}} = couch_view_group:request_group(
        Pid, MinSeq),
    {NthRed, View} = fabric_view:extract_view(Pid, ViewName, Views, reduce),
    ReduceView = {reduce, NthRed, Lang, View},
    Acc0 = #view_acc{group_level = GroupLevel, limit = Limit+Skip},
    Options0 = [{key_group_fun, GroupFun}, {dir, Dir}],
    case Keys of
    nil ->
        Options = [{start_key, {StartKey,StartDocId}},
            {end_key, {EndKey,EndDocId}} | Options0],
        couch_view:fold_reduce(ReduceView, fun reduce_fold/3, Acc0, Options);
    _ ->
        
        [couch_view:fold_reduce(ReduceView, fun reduce_fold/3, Acc0,
            [{start_key,{K,StartDocId}}, {end_key,{K,EndDocId}} | Options0])
            || K <- Keys]
    end,
    rexi:reply(complete).

get_db_info(DbName) ->
    with_db(DbName, [], {couch_db, get_db_info, []}).

get_doc_count(DbName) ->
    with_db(DbName, [], {couch_db, get_doc_count, []}).

get_update_seq(DbName) ->
    with_db(DbName, [], {couch_db, get_update_seq, []}).

open_doc(DbName, DocId, Options) ->
    with_db(DbName, Options, {couch_db, open_doc_int, [DocId, Options]}).

open_revs(DbName, Id, Revs, Options) ->
    with_db(DbName, Options, {couch_db, open_doc_revs, [Id, Revs, Options]}).

get_missing_revs(DbName, IdRevsList) ->
    % reimplement here so we get [] for Ids with no missing revs in response
    rexi:reply(case couch_db:open(DbName, []) of
    {ok, Db} ->
        Ids = [Id1 || {Id1, _Revs} <- IdRevsList],
        {ok, lists:zipwith(fun({Id, Revs}, FullDocInfoResult) ->
            case FullDocInfoResult of
            {ok, #full_doc_info{rev_tree=RevisionTree}} ->
                {Id, couch_key_tree:find_missing(RevisionTree, Revs)};
            not_found ->
                {Id, Revs}
            end
        end, IdRevsList, couch_btree:lookup(Db#db.id_tree, Ids))};
    Error ->
        Error
    end).

update_docs(DbName, Docs, Options) ->
    case proplists:get_value(replicated_changes, Options) of
    true ->
        X = replicated_changes;
    _ ->
        X = interactive_edit
    end,
    with_db(DbName, Options, {couch_db, update_docs, [Docs, Options, X]}).

group_info(DbName, Group0) ->
    {ok, Pid} = gen_server:call(couch_view, {get_group_server, DbName, Group0}),
    rexi:reply(couch_view_group:request_group_info(Pid)).

%%
%% internal
%%

with_db(DbName, Options, {M,F,A}) ->
    case couch_db:open(DbName, Options) of
    {ok, Db} ->
        rexi:reply(apply(M, F, [Db | A]));
    Error ->
        rexi:reply(Error)
    end.

view_fold(#full_doc_info{} = FullDocInfo, OffsetReds, Acc) ->
    % matches for _all_docs and translates #full_doc_info{} -> KV pair
    case couch_doc:to_doc_info(FullDocInfo) of
    #doc_info{revs=[#rev_info{deleted=false, rev=Rev}|_]} ->
        Id = FullDocInfo#full_doc_info.id,
        Value = {[{rev,couch_doc:rev_to_str(Rev)}]},
        view_fold({{Id,Id}, Value}, OffsetReds, Acc);
    #doc_info{revs=[#rev_info{deleted=true}|_]} ->
        {ok, Acc}
    end;
view_fold(KV, OffsetReds, #view_acc{offset=nil, total_rows=Total} = Acc) ->
    % calculates the offset for this shard
    #view_acc{reduce_fun=Reduce} = Acc,
    Offset = Reduce(OffsetReds),
    case rexi:sync_reply({total_and_offset, Total, Offset}) of
    ok ->
        view_fold(KV, OffsetReds, Acc#view_acc{offset=Offset});
    stop ->
        exit(normal)
    end;
view_fold(_KV, _Offset, #view_acc{limit=0} = Acc) ->
    % we scanned through limit+skip local rows
    {stop, Acc};
view_fold({{Key,Id}, Value}, _Offset, Acc) ->
    % the normal case
    #view_acc{
        db = Db,
        limit = Limit,
        include_docs = IncludeDocs,
        stop_fun = PassedEnd
    } = Acc,
    case PassedEnd(Key, Id) of
    true ->
        {stop, Acc};
    false ->
        Doc = if not IncludeDocs -> undefined; true ->
            case couch_db:open_doc(Db, Id, []) of
            {not_found, deleted} ->
                null;
            {not_found, missing} ->
                undefined;
            {ok, Doc0} ->
                couch_doc:to_json_obj(Doc0, [])
            end
        end,
        rexi:sync_reply(#view_row{key=Key, id=Id, value=Value, doc=Doc}),
        {ok, Acc#view_acc{limit=Limit-1}}
    end.

all_docs_stop_fun(#view_query_args{direction=fwd, end_key=EndKey}) ->
    fun(ViewKey, _) ->
        couch_db_updater:less_docid(EndKey, ViewKey)
    end;
all_docs_stop_fun(#view_query_args{direction=rev, end_key=EndKey}) ->
    fun(ViewKey, _) ->
        couch_db_updater:less_docid(ViewKey, EndKey)
    end.

final_response(Total, nil) ->
    case rexi:sync_reply({total_and_offset, Total, Total}) of ok ->
        rexi:reply(complete);
    stop -> ok end;
final_response(_Total, _Offset) ->
    rexi:reply(complete).

default_stop_fun(#view_query_args{direction=fwd, inclusive_end=true} = Args) ->
    #view_query_args{end_key=EndKey, end_docid=EndDocId} = Args,
    fun(ViewKey, ViewId) ->
        couch_view:less_json([EndKey, EndDocId], [ViewKey, ViewId])
    end;
default_stop_fun(#view_query_args{direction=fwd} = Args) ->
    #view_query_args{end_key=EndKey, end_docid=EndDocId} = Args,
    fun
        (ViewKey, _ViewId) when ViewKey == EndKey ->
            true;
        (ViewKey, ViewId) ->
            couch_view:less_json([EndKey, EndDocId], [ViewKey, ViewId])
    end;
default_stop_fun(#view_query_args{direction=rev, inclusive_end=true} = Args) ->
    #view_query_args{end_key=EndKey, end_docid=EndDocId} = Args,
    fun(ViewKey, ViewId) ->
        couch_view:less_json([ViewKey, ViewId], [EndKey, EndDocId])
    end;
default_stop_fun(#view_query_args{direction=rev} = Args) ->
    #view_query_args{end_key=EndKey, end_docid=EndDocId} = Args,
    fun
        (ViewKey, _ViewId) when ViewKey == EndKey ->
            true;
        (ViewKey, ViewId) ->
            couch_view:less_json([ViewKey, ViewId], [EndKey, EndDocId])
    end.

group_rows_fun(exact) ->
    fun({Key1,_}, {Key2,_}) -> Key1 == Key2 end;
group_rows_fun(0) ->
    fun(_A, _B) -> true end;
group_rows_fun(GroupLevel) when is_integer(GroupLevel) ->
    fun({[_|_] = Key1,_}, {[_|_] = Key2,_}) ->
        lists:sublist(Key1, GroupLevel) == lists:sublist(Key2, GroupLevel);
    ({Key1,_}, {Key2,_}) ->
        Key1 == Key2
    end.

reduce_fold(_Key, _Red, #view_acc{limit=0} = Acc) ->
    {stop, Acc};
reduce_fold(_Key, Red, #view_acc{group_level=0} = Acc) ->
    send(null, Red, Acc);
reduce_fold(Key, Red, #view_acc{group_level=exact} = Acc) ->
    send(Key, Red, Acc);
reduce_fold(K, Red, #view_acc{group_level=I} = Acc) when I > 0, is_list(K) ->
    send(lists:sublist(K, I), Red, Acc).

send(Key, Value, #view_acc{limit=Limit} = Acc) ->
    case rexi:sync_reply(#view_row{key=Key, value=Value}) of
    ok ->
        {ok, Acc#view_acc{limit=Limit-1}};
    stop ->
        exit(normal)
    end.

changes_enumerator(DocInfos, {Db, _Seq, Args}) ->
    #changes_args{include_docs=IncludeDocs, filter=FilterFun} = Args,
    [#doc_info{id=Id, high_seq=Seq, revs=[#rev_info{deleted=Del,rev=Rev}|_]}|_]
        = DocInfos,
    case [Result || Result <- FilterFun(DocInfos), Result /= null] of
    [] ->
        {ok, {Db, Seq, Args}};
    Results ->
        ChangesRow = changes_row(Db, Seq, Id, Results, Rev, Del, IncludeDocs),
        Go = rexi:sync_reply(ChangesRow),
        {Go, {Db, Seq, Args}}
    end.

changes_row(_, Seq, Id, Results, _, true, true) ->
    #view_row{key=Seq, id=Id, value=Results, doc=deleted};
changes_row(_, Seq, Id, Results, _, true, false) ->
    #view_row{key=Seq, id=Id, value=Results, doc=deleted};
changes_row(Db, Seq, Id, Results, Rev, false, true) ->
    #view_row{key=Seq, id=Id, value=Results, doc=doc_member(Db, Id, Rev)};
changes_row(_, Seq, Id, Results, _, false, false) ->
    #view_row{key=Seq, id=Id, value=Results}.

doc_member(Shard, Id, Rev) ->
    case couch_db:open_doc_revs(Shard, Id, [Rev], []) of
    {ok, [{ok,Doc}]} ->
        couch_doc:to_json_obj(Doc, []);
    Error ->
        Error
    end.