% Licensed under the Apache License, Version 2.0 (the "License"); you may not
% use this file except in compliance with the License. You may obtain a copy of
% the License at
%
% http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
% License for the specific language governing permissions and limitations under
% the License.

-module(mango_httpd).


-export([
    handle_req/2
]).


-include_lib("couch/include/couch_db.hrl").
-include("mango.hrl").
-include("mango_idx.hrl").

-record(vacc, {
    resp,
    prepend,
    kvs,
    buffer = [],
    bufsize = 0,
    threshold = 1490
}).

handle_req(#httpd{} = Req, Db0) ->
    try
        Db = set_user_ctx(Req, Db0),
        handle_req_int(Req, Db)
    catch
        throw:{mango_error, Module, Reason} ->
            %Stack = erlang:get_stacktrace(),
            {Code, ErrorStr, ReasonStr} = mango_error:info(Module, Reason),
            Resp = {[
                {<<"error">>, ErrorStr},
                {<<"reason">>, ReasonStr}
            ]},
            chttpd:send_json(Req, Code, Resp)
    end.


handle_req_int(#httpd{path_parts=[_, <<"_index">> | _]} = Req, Db) ->
    handle_index_req(Req, Db);
handle_req_int(#httpd{path_parts=[_, <<"_explain">> | _]} = Req, Db) ->
    handle_explain_req(Req, Db);
handle_req_int(#httpd{path_parts=[_, <<"_find">> | _]} = Req, Db) ->
    handle_find_req(Req, Db);
handle_req_int(_, _) ->
    throw({not_found, missing}).


handle_index_req(#httpd{method='GET', path_parts=[_, _]}=Req, Db) ->
    Params = lists:flatmap(fun({K, V}) -> parse_index_param(K, V) end,
        chttpd:qs(Req)),
    Idxs = lists:sort(mango_idx:list(Db)),
    JsonIdxs0 = lists:map(fun mango_idx:to_json/1, Idxs),
    TotalRows = length(JsonIdxs0),
    Limit = case couch_util:get_value(limit, Params, TotalRows) of
        Limit0 when Limit0 < 1 ->
            ?MANGO_ERROR(invalid_list_index_params);
        Limit0 ->
            Limit0
    end,
    Skip = case couch_util:get_value(skip, Params, 0) of
        Skip0 when Skip0 < 0 ->
            ?MANGO_ERROR(invalid_list_index_params);
        Skip0 when Skip0 > TotalRows ->
            TotalRows;
        Skip0 ->
            Skip0
    end,
    JsonIdxs = lists:sublist(JsonIdxs0, Skip+1, Limit),
	chttpd:send_json(Req, {[{total_rows, TotalRows}, {indexes, JsonIdxs}]});

handle_index_req(#httpd{method='POST', path_parts=[_, _]}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    {ok, Opts} = mango_opts:validate_idx_create(chttpd:json_body_obj(Req)),
    {ok, Idx0} = mango_idx:new(Db, Opts),
    {ok, Idx} = mango_idx:validate_new(Idx0, Db),
    {ok, DDoc} = mango_util:load_ddoc(Db, mango_idx:ddoc(Idx)),
    Id = Idx#idx.ddoc,
    Name = Idx#idx.name,
    Status = case mango_idx:add(DDoc, Idx) of
        {ok, DDoc} ->
            <<"exists">>;
        {ok, NewDDoc} ->
            CreateOpts = get_idx_w_opts(Opts),
            case mango_crud:insert(Db, NewDDoc, CreateOpts) of
                {ok, [{RespProps}]} ->
                    case lists:keyfind(error, 1, RespProps) of
                        {error, Reason} ->
                            ?MANGO_ERROR({error_saving_ddoc, Reason});
                        _ ->
                            <<"created">>
                    end;
                _ ->
                    ?MANGO_ERROR(error_saving_ddoc)
            end
    end,
	chttpd:send_json(Req, {[{result, Status}, {id, Id}, {name, Name}]});

handle_index_req(#httpd{path_parts=[_, _]}=Req, _Db) ->
    chttpd:send_method_not_allowed(Req, "GET,POST");

%% Essentially we just iterate through the list of ddoc ids passed in and
%% delete one by one. If an error occurs, all previous documents will be
%% deleted, but an error will be thrown for the current ddoc id.
handle_index_req(#httpd{method='POST', path_parts=[_, <<"_index">>,
        <<"_bulk_delete">>]}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    {ok, Opts} = mango_opts:validate_bulk_delete(chttpd:json_body_obj(Req)),
    Idxs = mango_idx:list(Db),
    DDocs = get_bulk_delete_ddocs(Opts),
    DelOpts = get_idx_w_opts(Opts),
    {Success, Fail} = lists:foldl(fun(DDocId0, {Success0, Fail0}) ->
        DDocId = convert_to_design_id(DDocId0),
        Filt = fun(Idx) -> mango_idx:ddoc(Idx) == DDocId end,
        Id = {<<"id">>, DDocId},
        case mango_idx:delete(Filt, Db, Idxs, DelOpts) of
            {ok, true} ->
                {[{[Id, {<<"ok">>, true}]} | Success0], Fail0};
            {error, Error} ->
                {Success0, [{[Id, {<<"error">>, Error}]} | Fail0]}
        end
    end, {[], []}, DDocs),
    chttpd:send_json(Req, {[{<<"success">>, Success}, {<<"fail">>, Fail}]});

handle_index_req(#httpd{path_parts=[_, <<"_index">>,
        <<"_bulk_delete">>]}=Req, _Db) ->
    chttpd:send_method_not_allowed(Req, "POST");

handle_index_req(#httpd{method='DELETE',
        path_parts=[A, B, <<"_design">>, DDocId0, Type, Name]}=Req, Db) ->
    PathParts = [A, B, <<"_design/", DDocId0/binary>>, Type, Name],
    handle_index_req(Req#httpd{path_parts=PathParts}, Db);

handle_index_req(#httpd{method='DELETE',
        path_parts=[_, _, DDocId0, Type, Name]}=Req, Db) ->
    Idxs = mango_idx:list(Db),
    DDocId = convert_to_design_id(DDocId0),
    DelOpts = get_idx_del_opts(Req),
    Filt = fun(Idx) ->
        IsDDoc = mango_idx:ddoc(Idx) == DDocId,
        IsType = mango_idx:type(Idx) == Type,
        IsName = mango_idx:name(Idx) == Name,
        IsDDoc andalso IsType andalso IsName
    end,
    case mango_idx:delete(Filt, Db, Idxs, DelOpts) of
        {ok, true} ->
            chttpd:send_json(Req, {[{ok, true}]});
        {error, not_found} ->
            throw({not_found, missing});
        {error, Error} ->
            ?MANGO_ERROR({error_saving_ddoc, Error})
    end;

handle_index_req(#httpd{path_parts=[_, _, _DDocId0, _Type, _Name]}=Req, _Db) ->
    chttpd:send_method_not_allowed(Req, "DELETE").


handle_explain_req(#httpd{method='POST'}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    {ok, Opts0} = mango_opts:validate_find(chttpd:json_body_obj(Req)),
    {value, {selector, Sel}, Opts} = lists:keytake(selector, 1, Opts0),
    Resp = mango_crud:explain(Db, Sel, Opts),
    chttpd:send_json(Req, Resp);

handle_explain_req(Req, _Db) ->
    chttpd:send_method_not_allowed(Req, "POST").


handle_find_req(#httpd{method='POST'}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    {ok, Opts0} = mango_opts:validate_find(chttpd:json_body_obj(Req)),
    {value, {selector, Sel}, Opts} = lists:keytake(selector, 1, Opts0),
    {ok, Resp0} = start_find_resp(Req, Db, Sel, Opts),
    {ok, AccOut} = run_find(Resp0, Db, Sel, Opts),
    end_find_resp(AccOut);

handle_find_req(Req, _Db) ->
    chttpd:send_method_not_allowed(Req, "POST").


set_user_ctx(#httpd{user_ctx=Ctx}, Db) ->
    Db#db{user_ctx=Ctx}.


get_idx_w_opts(Opts) ->
    case lists:keyfind(w, 1, Opts) of
        {w, N} when is_integer(N), N > 0 ->
            [{w, integer_to_list(N)}];
        _ ->
            [{w, "2"}]
    end.


get_bulk_delete_ddocs(Opts) ->
    case lists:keyfind(docids, 1, Opts) of
        {docids, DDocs} when is_list(DDocs) ->
            DDocs;
        _ ->
            []
    end.


get_idx_del_opts(Req) ->
    try
        WStr = chttpd:qs_value(Req, "w", "2"),
        _ = list_to_integer(WStr),
        [{w, WStr}]
    catch _:_ ->
        [{w, "2"}]
    end.


convert_to_design_id(DDocId) ->
    case DDocId of
        <<"_design/", _/binary>> -> DDocId;
        _ -> <<"_design/", DDocId/binary>>
    end.


start_find_resp(Req, Db, Sel, Opts) ->
    chttpd:start_delayed_json_response(Req, 200, [], maybe_add_warning(Db, Sel, Opts)).


maybe_add_warning(Db, Selector, Opts) ->
    UsableIndexes = mango_idx:get_usable_indexes(Db, Selector, Opts),
    case length(UsableIndexes) of
        0 ->
            "{\"warning\":\"no matching index found, create an index to optimize query time\",\r\n\"docs\":[";
        _ ->
            "{\"docs\":["
    end.


end_find_resp(Acc0) ->
    #vacc{resp=Resp00, buffer=Buf, kvs=KVs, threshold=Max} = Acc0,
    {ok, Resp0} = chttpd:close_delayed_json_object(Resp00, Buf, "\r\n]", Max),
    FinalAcc = lists:foldl(fun({K, V}, Acc) ->
        JK = ?JSON_ENCODE(K),
        JV = ?JSON_ENCODE(V),
        [JV, ": ", JK, ",\r\n" | Acc]
    end, [], KVs),
    Chunk = lists:reverse(FinalAcc, ["}\r\n"]),
    {ok, Resp1} = chttpd:send_delayed_chunk(Resp0, Chunk),
    chttpd:end_delayed_json_response(Resp1).


run_find(Resp, Db, Sel, Opts) ->
    Acc0 = #vacc{
        resp = Resp,
        prepend = "\r\n",
        kvs = [],
        threshold = chttpd:chunked_response_buffer_size()
    },
    mango_crud:find(Db, Sel, fun handle_doc/2, Acc0, Opts).


handle_doc({add_key, Key, Value}, Acc0) ->
    #vacc{kvs=KVs} = Acc0,
    NewKVs = lists:keystore(Key, 1, KVs, {Key, Value}),
    {ok, Acc0#vacc{kvs = NewKVs}};
handle_doc({row, Doc}, Acc0) ->
    #vacc{prepend=Prepend} = Acc0,
    Chunk = [Prepend, ?JSON_ENCODE(Doc)],
    maybe_flush_response(Acc0, Chunk, iolist_size(Chunk)).

maybe_flush_response(#vacc{bufsize=Size, threshold=Max} = Acc, Data, Len)
        when Size > 0 andalso (Size + Len) > Max ->
    #vacc{buffer = Buffer, resp = Resp} = Acc,
    {ok, R1} = chttpd:send_delayed_chunk(Resp, Buffer),
    {ok, Acc#vacc{prepend = ",\r\n", buffer = Data, bufsize = Len, resp = R1}};
maybe_flush_response(Acc0, Data, Len) ->
    #vacc{buffer = Buf, bufsize = Size} = Acc0,
    Acc = Acc0#vacc{
        prepend = ",\r\n",
        buffer = [Buf | Data],
        bufsize = Size + Len
    },
    {ok, Acc}.


parse_index_param("limit", Value) ->
    [{limit, parse_val(Value)}];
parse_index_param("skip", Value) ->
    [{skip, parse_val(Value)}];
parse_index_param(_Key, _Value) ->
     [].

parse_val(Value) ->
    case (catch list_to_integer(Value)) of
    IntVal when is_integer(IntVal) ->
        IntVal;
    _ ->
        ?MANGO_ERROR(invalid_list_index_params)
    end.