% 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(chttpd_db).
-include_lib("couch/include/couch_db.hrl").
-include_lib("couch_mrview/include/couch_mrview.hrl").

-export([handle_request/1, handle_compact_req/2, handle_design_req/2,
    db_req/2, couch_doc_open/4,handle_changes_req/2,
    update_doc_result_to_json/1, update_doc_result_to_json/2,
    handle_design_info_req/3, handle_view_cleanup_req/2,
    update_doc/4, http_code_from_status/1]).

-import(chttpd,
    [send_json/2,send_json/3,send_json/4,send_method_not_allowed/2,
    start_json_response/2,send_chunk/2,end_json_response/1,
    start_chunked_response/3, absolute_uri/2, send/2,
    start_response_length/4]).

-record(doc_query_args, {
    options = [],
    rev = nil,
    open_revs = [],
    update_type = interactive_edit,
    atts_since = nil
}).

% Accumulator for changes_callback function
-record(cacc, {
    etag,
    feed,
    mochi,
    prepend = "",
    responding = false,
    buffer = [],
    bufsize = 0,
    threshold
}).

-define(IS_ALL_DOCS(T), (
    T == <<"_all_docs">>
    orelse T == <<"_local_docs">>
    orelse T == <<"_design_docs">>)).

% Database request handlers
handle_request(#httpd{path_parts=[DbName|RestParts],method=Method}=Req)->
    case {Method, RestParts} of
    {'PUT', []} ->
        create_db_req(Req, DbName);
    {'DELETE', []} ->
         % if we get ?rev=... the user is using a faulty script where the
         % document id is empty by accident. Let them recover safely.
         case chttpd:qs_value(Req, "rev", false) of
             false -> delete_db_req(Req, DbName);
             _Rev -> throw({bad_request,
                 "You tried to DELETE a database with a ?=rev parameter. "
                 ++ "Did you mean to DELETE a document instead?"})
         end;
    {_, []} ->
        do_db_req(Req, fun db_req/2);
    {_, [SecondPart|_]} ->
        Handler = chttpd_handlers:db_handler(SecondPart, fun db_req/2),
        do_db_req(Req, Handler)
    end.

handle_changes_req(#httpd{method='POST'}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    handle_changes_req1(Req, Db);
handle_changes_req(#httpd{method='GET'}=Req, Db) ->
    handle_changes_req1(Req, Db);
handle_changes_req(#httpd{path_parts=[_,<<"_changes">>]}=Req, _Db) ->
    send_method_not_allowed(Req, "GET,POST,HEAD").

handle_changes_req1(#httpd{}=Req, Db) ->
    #changes_args{filter=Raw, style=Style} = Args0 = parse_changes_query(Req),
    ChangesArgs = Args0#changes_args{
        filter_fun = couch_changes:configure_filter(Raw, Style, Req, Db),
        db_open_options = [{user_ctx, Db#db.user_ctx}]
    },
    Max = chttpd:chunked_response_buffer_size(),
    case ChangesArgs#changes_args.feed of
    "normal" ->
        T0 = os:timestamp(),
        {ok, Info} = fabric:get_db_info(Db),
        Suffix = mem3:shard_suffix(Db),
        Etag = chttpd:make_etag({Info, Suffix}),
        DeltaT = timer:now_diff(os:timestamp(), T0) / 1000,
        couch_stats:update_histogram([couchdb, dbinfo], DeltaT),
        chttpd:etag_respond(Req, Etag, fun() ->
            Acc0 = #cacc{
                feed = normal,
                etag = Etag,
                mochi = Req,
                threshold = Max
            },
            fabric:changes(Db, fun changes_callback/2, Acc0, ChangesArgs)
        end);
    Feed when Feed =:= "continuous"; Feed =:= "longpoll"; Feed =:= "eventsource"  ->
        couch_stats:increment_counter([couchdb, httpd, clients_requesting_changes]),
        Acc0 = #cacc{
            feed = list_to_atom(Feed),
            mochi = Req,
            threshold = Max
        },
        try
            fabric:changes(Db, fun changes_callback/2, Acc0, ChangesArgs)
        after
            couch_stats:decrement_counter([couchdb, httpd, clients_requesting_changes])
        end;
    _ ->
        Msg = <<"Supported `feed` types: normal, continuous, live, longpoll, eventsource">>,
        throw({bad_request, Msg})
    end.

% callbacks for continuous feed (newline-delimited JSON Objects)
changes_callback(start, #cacc{feed = continuous} = Acc) ->
    {ok, Resp} = chttpd:start_delayed_json_response(Acc#cacc.mochi, 200),
    {ok, Acc#cacc{mochi = Resp, responding = true}};
changes_callback({change, Change}, #cacc{feed = continuous} = Acc) ->
    Data = [?JSON_ENCODE(Change) | "\n"],
    Len = iolist_size(Data),
    maybe_flush_changes_feed(Acc, Data, Len);
changes_callback({stop, EndSeq, Pending}, #cacc{feed = continuous} = Acc) ->
    #cacc{mochi = Resp, buffer = Buf} = Acc,
    Row = {[
        {<<"last_seq">>, EndSeq},
        {<<"pending">>, Pending}
    ]},
    Data = [Buf, ?JSON_ENCODE(Row) | "\n"],
    {ok, Resp1} = chttpd:send_delayed_chunk(Resp, Data),
    chttpd:end_delayed_json_response(Resp1);

% callbacks for eventsource feed (newline-delimited eventsource Objects)
changes_callback(start, #cacc{feed = eventsource} = Acc) ->
    #cacc{mochi = Req} = Acc,
    Headers = [
        {"Content-Type", "text/event-stream"},
        {"Cache-Control", "no-cache"}
    ],
    {ok, Resp} = chttpd:start_delayed_json_response(Req, 200, Headers),
    {ok, Acc#cacc{mochi = Resp, responding = true}};
changes_callback({change, {ChangeProp}=Change}, #cacc{feed = eventsource} = Acc) ->
    Seq = proplists:get_value(seq, ChangeProp),
    Chunk = [
        "data: ", ?JSON_ENCODE(Change),
        "\n", "id: ", ?JSON_ENCODE(Seq),
        "\n\n"
    ],
    Len = iolist_size(Chunk),
    maybe_flush_changes_feed(Acc, Chunk, Len);
changes_callback(timeout, #cacc{feed = eventsource} = Acc) ->
    #cacc{mochi = Resp} = Acc,
    Chunk = "event: heartbeat\ndata: \n\n",
    {ok, Resp1} = chttpd:send_delayed_chunk(Resp, Chunk),
    {ok, Acc#cacc{mochi = Resp1}};
changes_callback({stop, _EndSeq}, #cacc{feed = eventsource} = Acc) ->
    #cacc{mochi = Resp, buffer = Buf} = Acc,
    {ok, Resp1} = chttpd:send_delayed_chunk(Resp, Buf),
    chttpd:end_delayed_json_response(Resp1);

% callbacks for longpoll and normal (single JSON Object)
changes_callback(start, #cacc{feed = normal} = Acc) ->
    #cacc{etag = Etag, mochi = Req} = Acc,
    FirstChunk = "{\"results\":[\n",
    {ok, Resp} = chttpd:start_delayed_json_response(Req, 200,
        [{"ETag",Etag}], FirstChunk),
    {ok, Acc#cacc{mochi = Resp, responding = true}};
changes_callback(start, Acc) ->
    #cacc{mochi = Req} = Acc,
    FirstChunk = "{\"results\":[\n",
    {ok, Resp} = chttpd:start_delayed_json_response(Req, 200, [], FirstChunk),
    {ok, Acc#cacc{mochi = Resp, responding = true}};
changes_callback({change, Change}, Acc) ->
    Data = [Acc#cacc.prepend, ?JSON_ENCODE(Change)],
    Len = iolist_size(Data),
    maybe_flush_changes_feed(Acc, Data, Len);
changes_callback({stop, EndSeq, Pending}, Acc) ->
    #cacc{buffer = Buf, mochi = Resp, threshold = Max} = Acc,
    Terminator = [
        "\n],\n\"last_seq\":",
        ?JSON_ENCODE(EndSeq),
        ",\"pending\":",
        ?JSON_ENCODE(Pending),
        "}\n"
    ],
    {ok, Resp1} = chttpd:close_delayed_json_object(Resp, Buf, Terminator, Max),
    chttpd:end_delayed_json_response(Resp1);

changes_callback(waiting_for_updates, #cacc{buffer = []} = Acc) ->
    {ok, Acc};
changes_callback(waiting_for_updates, Acc) ->
    #cacc{buffer = Buf, mochi = Resp} = Acc,
    {ok, Resp1} = chttpd:send_delayed_chunk(Resp, Buf),
    {ok, Acc#cacc{buffer = [], bufsize = 0, mochi = Resp1}};
changes_callback(timeout, Acc) ->
    {ok, Resp1} = chttpd:send_delayed_chunk(Acc#cacc.mochi, "\n"),
    {ok, Acc#cacc{mochi = Resp1}};
changes_callback({error, Reason}, #cacc{mochi = #httpd{}} = Acc) ->
    #cacc{mochi = Req} = Acc,
    chttpd:send_error(Req, Reason);
changes_callback({error, Reason}, #cacc{feed = normal, responding = false} = Acc) ->
    #cacc{mochi = Req} = Acc,
    chttpd:send_error(Req, Reason);
changes_callback({error, Reason}, Acc) ->
    chttpd:send_delayed_error(Acc#cacc.mochi, Reason).

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

handle_compact_req(#httpd{method='POST'}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    case Req#httpd.path_parts of
        [_DbName, <<"_compact">>] ->
            ok = fabric:compact(Db),
            send_json(Req, 202, {[{ok, true}]});
        [DbName, <<"_compact">>, DesignName | _] ->
            case ddoc_cache:open(DbName, <<"_design/", DesignName/binary>>) of
                {ok, _DDoc} ->
                    ok = fabric:compact(Db, DesignName),
                    send_json(Req, 202, {[{ok, true}]});
                Error ->
                    throw(Error)
            end
    end;

handle_compact_req(Req, _Db) ->
    send_method_not_allowed(Req, "POST").

handle_view_cleanup_req(Req, Db) ->
    ok = fabric:cleanup_index_files_all_nodes(Db),
    send_json(Req, 202, {[{ok, true}]}).

handle_design_req(#httpd{
        path_parts=[_DbName, _Design, Name, <<"_",_/binary>> = Action | _Rest]
    }=Req, Db) ->
    DbName = mem3:dbname(Db#db.name),
    case ddoc_cache:open(DbName, <<"_design/", Name/binary>>) of
    {ok, DDoc} ->
        Handler = chttpd_handlers:design_handler(Action, fun bad_action_req/3),
        Handler(Req, Db, DDoc);
    Error ->
        throw(Error)
    end;

handle_design_req(Req, Db) ->
    db_req(Req, Db).

bad_action_req(#httpd{path_parts=[_, _, Name|FileNameParts]}=Req, Db, _DDoc) ->
    db_attachment_req(Req, Db, <<"_design/",Name/binary>>, FileNameParts).

handle_design_info_req(#httpd{method='GET'}=Req, Db, #doc{} = DDoc) ->
    [_, _, Name, _] = Req#httpd.path_parts,
    {ok, GroupInfoList} = fabric:get_view_group_info(Db, DDoc),
    send_json(Req, 200, {[
        {name,  Name},
        {view_index, {GroupInfoList}}
    ]});

handle_design_info_req(Req, _Db, _DDoc) ->
    send_method_not_allowed(Req, "GET").

create_db_req(#httpd{}=Req, DbName) ->
    couch_httpd:verify_is_server_admin(Req),
    N = chttpd:qs_value(Req, "n", config:get("cluster", "n", "3")),
    Q = chttpd:qs_value(Req, "q", config:get("cluster", "q", "8")),
    P = chttpd:qs_value(Req, "placement", config:get("cluster", "placement")),
    DocUrl = absolute_uri(Req, "/" ++ couch_util:url_encode(DbName)),
    case fabric:create_db(DbName, [{n,N}, {q,Q}, {placement,P}]) of
    ok ->
        send_json(Req, 201, [{"Location", DocUrl}], {[{ok, true}]});
    accepted ->
        send_json(Req, 202, [{"Location", DocUrl}], {[{ok, true}]});
    {error, file_exists} ->
        chttpd:send_error(Req, file_exists);
    Error ->
        throw(Error)
    end.

delete_db_req(#httpd{}=Req, DbName) ->
    couch_httpd:verify_is_server_admin(Req),
    case fabric:delete_db(DbName, []) of
    ok ->
        send_json(Req, 200, {[{ok, true}]});
    accepted ->
        send_json(Req, 202, {[{ok, true}]});
    Error ->
        throw(Error)
    end.

do_db_req(#httpd{path_parts=[DbName|_], user_ctx=Ctx}=Req, Fun) ->
    fabric:get_security(DbName, [{user_ctx,Ctx}]), % calls check_is_reader
    Fun(Req, #db{name=DbName, user_ctx=Ctx}).

db_req(#httpd{method='GET',path_parts=[DbName]}=Req, _Db) ->
    % measure the time required to generate the etag, see if it's worth it
    T0 = os:timestamp(),
    {ok, DbInfo} = fabric:get_db_info(DbName),
    DeltaT = timer:now_diff(os:timestamp(), T0) / 1000,
    couch_stats:update_histogram([couchdb, dbinfo], DeltaT),
    send_json(Req, {DbInfo});

db_req(#httpd{method='POST', path_parts=[DbName], user_ctx=Ctx}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),

    W = chttpd:qs_value(Req, "w", integer_to_list(mem3:quorum(Db))),
    Options = [{user_ctx,Ctx}, {w,W}],

    Doc = couch_doc:from_json_obj(chttpd:json_body(Req)),
    Doc2 = case Doc#doc.id of
        <<"">> ->
            Doc#doc{id=couch_uuids:new(), revs={0, []}};
        _ ->
            Doc
    end,
    DocId = Doc2#doc.id,
    case chttpd:qs_value(Req, "batch") of
    "ok" ->
        % async_batching
        spawn(fun() ->
                case catch(fabric:update_doc(Db, Doc2, Options)) of
                {ok, _} -> ok;
                {accepted, _} -> ok;
                Error ->
                    couch_log:debug("Batch doc error (~s): ~p",[DocId, Error])
                end
            end),

        send_json(Req, 202, [], {[
            {ok, true},
            {id, DocId}
        ]});
    _Normal ->
        % normal
        DocUrl = absolute_uri(Req, [$/, couch_util:url_encode(DbName),
            $/, couch_util:url_encode(DocId)]),
        case fabric:update_doc(Db, Doc2, Options) of
        {ok, NewRev} ->
            HttpCode = 201;
        {accepted, NewRev} ->
            HttpCode = 202
        end,
        send_json(Req, HttpCode, [{"Location", DocUrl}], {[
            {ok, true},
            {id, DocId},
            {rev, couch_doc:rev_to_str(NewRev)}
        ]})
    end;

db_req(#httpd{path_parts=[_DbName]}=Req, _Db) ->
    send_method_not_allowed(Req, "DELETE,GET,HEAD,POST");

db_req(#httpd{method='POST',path_parts=[_,<<"_ensure_full_commit">>]}=Req, _Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    send_json(Req, 201, {[
        {ok, true},
        {instance_start_time, <<"0">>}
    ]});

db_req(#httpd{path_parts=[_,<<"_ensure_full_commit">>]}=Req, _Db) ->
    send_method_not_allowed(Req, "POST");

db_req(#httpd{method='POST',path_parts=[_,<<"_bulk_docs">>], user_ctx=Ctx}=Req, Db) ->
    couch_stats:increment_counter([couchdb, httpd, bulk_requests]),
    chttpd:validate_ctype(Req, "application/json"),
    {JsonProps} = chttpd:json_body_obj(Req),
    DocsArray = case couch_util:get_value(<<"docs">>, JsonProps) of
    undefined ->
        throw({bad_request, <<"POST body must include `docs` parameter.">>});
    DocsArray0 when not is_list(DocsArray0) ->
        throw({bad_request, <<"`docs` parameter must be an array.">>});
    DocsArray0 ->
        DocsArray0
    end,
    couch_stats:update_histogram([couchdb, httpd, bulk_docs], length(DocsArray)),
    W = case couch_util:get_value(<<"w">>, JsonProps) of
    Value when is_integer(Value) ->
        integer_to_list(Value);
    _ ->
        chttpd:qs_value(Req, "w", integer_to_list(mem3:quorum(Db)))
    end,
    case chttpd:header_value(Req, "X-Couch-Full-Commit") of
    "true" ->
        Options = [full_commit, {user_ctx,Ctx}, {w,W}];
    "false" ->
        Options = [delay_commit, {user_ctx,Ctx}, {w,W}];
    _ ->
        Options = [{user_ctx,Ctx}, {w,W}]
    end,
    case couch_util:get_value(<<"new_edits">>, JsonProps, true) of
    true ->
        Docs = lists:map(
            fun(JsonObj) ->
                Doc = couch_doc:from_json_obj(JsonObj),
                validate_attachment_names(Doc),
                Id = case Doc#doc.id of
                    <<>> -> couch_uuids:new();
                    Id0 -> Id0
                end,
                Doc#doc{id=Id}
            end,
            DocsArray),
        Options2 =
        case couch_util:get_value(<<"all_or_nothing">>, JsonProps) of
        true  -> [all_or_nothing|Options];
        _ -> Options
        end,
        case fabric:update_docs(Db, Docs, Options2) of
        {ok, Results} ->
            % output the results
            DocResults = lists:zipwith(fun update_doc_result_to_json/2,
                Docs, Results),
            send_json(Req, 201, DocResults);
        {accepted, Results} ->
            % output the results
            DocResults = lists:zipwith(fun update_doc_result_to_json/2,
                Docs, Results),
            send_json(Req, 202, DocResults);
        {aborted, Errors} ->
            ErrorsJson =
                lists:map(fun update_doc_result_to_json/1, Errors),
            send_json(Req, 417, ErrorsJson)
        end;
    false ->
        Docs = [couch_doc:from_json_obj(JsonObj) || JsonObj <- DocsArray],
        [validate_attachment_names(D) || D <- Docs],
        case fabric:update_docs(Db, Docs, [replicated_changes|Options]) of
        {ok, Errors} ->
            ErrorsJson = lists:map(fun update_doc_result_to_json/1, Errors),
            send_json(Req, 201, ErrorsJson);
        {accepted, Errors} ->
            ErrorsJson = lists:map(fun update_doc_result_to_json/1, Errors),
            send_json(Req, 202, ErrorsJson)
        end
    end;

db_req(#httpd{path_parts=[_,<<"_bulk_docs">>]}=Req, _Db) ->
    send_method_not_allowed(Req, "POST");


db_req(#httpd{method='POST', path_parts=[_, <<"_bulk_get">>]}=Req, Db) ->
    couch_stats:increment_counter([couchdb, httpd, bulk_requests]),
    couch_httpd:validate_ctype(Req, "application/json"),
    {JsonProps} = chttpd:json_body_obj(Req),
    case couch_util:get_value(<<"docs">>, JsonProps) of
        undefined ->
            throw({bad_request, <<"Missing JSON list of 'docs'.">>});
        Docs ->
            #doc_query_args{
                options = Options
            } = bulk_get_parse_doc_query(Req),

            {ok, Resp} = start_json_response(Req, 200),
            send_chunk(Resp, <<"{\"results\": [">>),

            lists:foldl(fun(Doc, Sep) ->
                {DocId, Results, Options1} = bulk_get_open_doc_revs(Db, Doc,
                                                                    Options),
                bulk_get_send_docs_json(Resp, DocId, Results, Options1, Sep),
                <<",">>
            end, <<"">>, Docs),

            send_chunk(Resp, <<"]}">>),
            end_json_response(Resp)
    end;
db_req(#httpd{path_parts=[_, <<"_bulk_get">>]}=Req, _Db) ->
    send_method_not_allowed(Req, "POST");


db_req(#httpd{method='POST',path_parts=[_,<<"_purge">>]}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    {IdsRevs} = chttpd:json_body_obj(Req),
    IdsRevs2 = [{Id, couch_doc:parse_revs(Revs)} || {Id, Revs} <- IdsRevs],
    case fabric:purge_docs(Db, IdsRevs2) of
    {ok, PurgeSeq, PurgedIdsRevs} ->
        PurgedIdsRevs2 = [{Id, couch_doc:revs_to_strs(Revs)} || {Id, Revs}
            <- PurgedIdsRevs],
        send_json(Req, 200, {[
            {<<"purge_seq">>, PurgeSeq},
            {<<"purged">>, {PurgedIdsRevs2}}
        ]});
    Error ->
        throw(Error)
    end;

db_req(#httpd{path_parts=[_,<<"_purge">>]}=Req, _Db) ->
    send_method_not_allowed(Req, "POST");

db_req(#httpd{method='GET',path_parts=[_,OP]}=Req, Db) when ?IS_ALL_DOCS(OP) ->
    case chttpd:qs_json_value(Req, "keys", nil) of
    Keys when is_list(Keys) ->
        all_docs_view(Req, Db, Keys, OP);
    nil ->
        all_docs_view(Req, Db, undefined, OP);
    _ ->
        throw({bad_request, "`keys` parameter must be an array."})
    end;

db_req(#httpd{method='POST',path_parts=[_,OP]}=Req, Db) when ?IS_ALL_DOCS(OP) ->
    chttpd:validate_ctype(Req, "application/json"),
    {Fields} = chttpd:json_body_obj(Req),
    case couch_util:get_value(<<"keys">>, Fields, nil) of
    Keys when is_list(Keys) ->
        all_docs_view(Req, Db, Keys, OP);
    nil ->
        all_docs_view(Req, Db, undefined, OP);
    _ ->
        throw({bad_request, "`keys` body member must be an array."})
    end;

db_req(#httpd{path_parts=[_,OP]}=Req, _Db) when ?IS_ALL_DOCS(OP) ->
    send_method_not_allowed(Req, "GET,HEAD,POST");

db_req(#httpd{method='POST',path_parts=[_,<<"_missing_revs">>]}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    {JsonDocIdRevs} = chttpd:json_body_obj(Req),
    case fabric:get_missing_revs(Db, JsonDocIdRevs) of
        {error, Reason} ->
            chttpd:send_error(Req, Reason);
        {ok, Results} ->
            Results2 = [{Id, couch_doc:revs_to_strs(Revs)} ||
                    {Id, Revs, _} <- Results],
            send_json(Req, {[
                {missing_revs, {Results2}}
            ]})
    end;

db_req(#httpd{path_parts=[_,<<"_missing_revs">>]}=Req, _Db) ->
    send_method_not_allowed(Req, "POST");

db_req(#httpd{method='POST',path_parts=[_,<<"_revs_diff">>]}=Req, Db) ->
    chttpd:validate_ctype(Req, "application/json"),
    {JsonDocIdRevs} = chttpd:json_body_obj(Req),
    case fabric:get_missing_revs(Db, JsonDocIdRevs) of
        {error, Reason} ->
            chttpd:send_error(Req, Reason);
        {ok, Results} ->
            Results2 =
            lists:map(fun({Id, MissingRevs, PossibleAncestors}) ->
                {Id,
                    {[{missing, couch_doc:revs_to_strs(MissingRevs)}] ++
                        if PossibleAncestors == [] ->
                            [];
                        true ->
                            [{possible_ancestors,
                                couch_doc:revs_to_strs(PossibleAncestors)}]
                        end}}
            end, Results),
            send_json(Req, {Results2})
    end;

db_req(#httpd{path_parts=[_,<<"_revs_diff">>]}=Req, _Db) ->
    send_method_not_allowed(Req, "POST");

db_req(#httpd{method='PUT',path_parts=[_,<<"_security">>],user_ctx=Ctx}=Req,
        Db) ->
    SecObj = chttpd:json_body(Req),
    case fabric:set_security(Db, SecObj, [{user_ctx, Ctx}]) of
        ok ->
            send_json(Req, {[{<<"ok">>, true}]});
        Else ->
            throw(Else)
    end;

db_req(#httpd{method='GET',path_parts=[_,<<"_security">>]}=Req, Db) ->
    send_json(Req, fabric:get_security(Db));

db_req(#httpd{path_parts=[_,<<"_security">>]}=Req, _Db) ->
    send_method_not_allowed(Req, "PUT,GET");

db_req(#httpd{method='PUT',path_parts=[_,<<"_revs_limit">>],user_ctx=Ctx}=Req,
        Db) ->
    Limit = chttpd:json_body(Req),
    ok = fabric:set_revs_limit(Db, Limit, [{user_ctx,Ctx}]),
    send_json(Req, {[{<<"ok">>, true}]});

db_req(#httpd{method='GET',path_parts=[_,<<"_revs_limit">>]}=Req, Db) ->
    send_json(Req, fabric:get_revs_limit(Db));

db_req(#httpd{path_parts=[_,<<"_revs_limit">>]}=Req, _Db) ->
    send_method_not_allowed(Req, "PUT,GET");

% Special case to enable using an unencoded slash in the URL of design docs,
% as slashes in document IDs must otherwise be URL encoded.
db_req(#httpd{method='GET', mochi_req=MochiReq, path_parts=[_DbName, <<"_design/", _/binary>> | _]}=Req, _Db) ->
    [Head | Tail] = re:split(MochiReq:get(raw_path), "_design%2F", [{return, list}, caseless]),
    chttpd:send_redirect(Req, Head ++ "_design/" ++ Tail);

db_req(#httpd{path_parts=[_DbName,<<"_design">>,Name]}=Req, Db) ->
    db_doc_req(Req, Db, <<"_design/",Name/binary>>);

db_req(#httpd{path_parts=[_DbName,<<"_design">>,Name|FileNameParts]}=Req, Db) ->
    db_attachment_req(Req, Db, <<"_design/",Name/binary>>, FileNameParts);


% Special case to allow for accessing local documents without %2F
% encoding the docid. Throws out requests that don't have the second
% path part or that specify an attachment name.
db_req(#httpd{path_parts=[_DbName, <<"_local">>]}, _Db) ->
    throw({bad_request, <<"Invalid _local document id.">>});

db_req(#httpd{path_parts=[_DbName, <<"_local/">>]}, _Db) ->
    throw({bad_request, <<"Invalid _local document id.">>});

db_req(#httpd{path_parts=[_DbName, <<"_local">>, Name]}=Req, Db) ->
    db_doc_req(Req, Db, <<"_local/", Name/binary>>);

db_req(#httpd{path_parts=[_DbName, <<"_local">> | _Rest]}, _Db) ->
    throw({bad_request, <<"_local documents do not accept attachments.">>});

db_req(#httpd{path_parts=[_, DocId]}=Req, Db) ->
    db_doc_req(Req, Db, DocId);

db_req(#httpd{path_parts=[_, DocId | FileNameParts]}=Req, Db) ->
    db_attachment_req(Req, Db, DocId, FileNameParts).

all_docs_view(Req, Db, Keys, OP) ->
    Args0 = couch_mrview_http:parse_params(Req, Keys),
    Args1 = Args0#mrargs{view_type=map},
    Args2 = couch_mrview_util:validate_args(Args1),
    Args3 = set_namespace(OP, Args2),
    Options = [{user_ctx, Req#httpd.user_ctx}],
    Max = chttpd:chunked_response_buffer_size(),
    VAcc = #vacc{db=Db, req=Req, threshold=Max},
    {ok, Resp} = fabric:all_docs(Db, Options, fun couch_mrview_http:view_cb/2, VAcc, Args3),
    {ok, Resp#vacc.resp}.

db_doc_req(#httpd{method='DELETE'}=Req, Db, DocId) ->
    % check for the existence of the doc to handle the 404 case.
    couch_doc_open(Db, DocId, nil, []),
    case chttpd:qs_value(Req, "rev") of
    undefined ->
        Body = {[{<<"_deleted">>,true}]};
    Rev ->
        Body = {[{<<"_rev">>, ?l2b(Rev)},{<<"_deleted">>,true}]}
    end,
    send_updated_doc(Req, Db, DocId, couch_doc_from_req(Req, DocId, Body));

db_doc_req(#httpd{method='GET', mochi_req=MochiReq}=Req, Db, DocId) ->
    #doc_query_args{
        rev = Rev,
        open_revs = Revs,
        options = Options0,
        atts_since = AttsSince
    } = parse_doc_query(Req),
    Options = [{user_ctx, Req#httpd.user_ctx} | Options0],
    case Revs of
    [] ->
        Options2 =
        if AttsSince /= nil ->
            [{atts_since, AttsSince}, attachments | Options];
        true -> Options
        end,
        Doc = couch_doc_open(Db, DocId, Rev, Options2),
        send_doc(Req, Doc, Options2);
    _ ->
        case fabric:open_revs(Db, DocId, Revs, Options) of
            {ok, []} when Revs == all ->
                chttpd:send_error(Req, {not_found, missing});
            {ok, Results} ->
                case MochiReq:accepts_content_type("multipart/mixed") of
                false ->
                    {ok, Resp} = start_json_response(Req, 200),
                    send_chunk(Resp, "["),
                    % We loop through the docs. The first time through the separator
                    % is whitespace, then a comma on subsequent iterations.
                    lists:foldl(
                        fun(Result, AccSeparator) ->
                            case Result of
                            {ok, Doc} ->
                                JsonDoc = couch_doc:to_json_obj(Doc, Options),
                                Json = ?JSON_ENCODE({[{ok, JsonDoc}]}),
                                send_chunk(Resp, AccSeparator ++ Json);
                            {{not_found, missing}, RevId} ->
                                RevStr = couch_doc:rev_to_str(RevId),
                                Json = ?JSON_ENCODE({[{<<"missing">>, RevStr}]}),
                                send_chunk(Resp, AccSeparator ++ Json)
                            end,
                            "," % AccSeparator now has a comma
                        end,
                        "", Results),
                    send_chunk(Resp, "]"),
                    end_json_response(Resp);
                true ->
                    send_docs_multipart(Req, Results, Options)
                end;
            {error, Error} ->
                chttpd:send_error(Req, Error)
        end
    end;

db_doc_req(#httpd{method='POST', user_ctx=Ctx}=Req, Db, DocId) ->
    couch_httpd:validate_referer(Req),
    couch_doc:validate_docid(DocId),
    chttpd:validate_ctype(Req, "multipart/form-data"),

    W = chttpd:qs_value(Req, "w", integer_to_list(mem3:quorum(Db))),
    Options = [{user_ctx,Ctx}, {w,W}],

    Form = couch_httpd:parse_form(Req),
    case proplists:is_defined("_doc", Form) of
    true ->
        Json = ?JSON_DECODE(couch_util:get_value("_doc", Form)),
        Doc = couch_doc_from_req(Req, DocId, Json);
    false ->
        Rev = couch_doc:parse_rev(list_to_binary(couch_util:get_value("_rev", Form))),
        Doc = case fabric:open_revs(Db, DocId, [Rev], []) of
            {ok, [{ok, Doc0}]} -> Doc0;
            {error, Error} -> throw(Error)
        end
    end,
    UpdatedAtts = [
        couch_att:new([
            {name, validate_attachment_name(Name)},
            {type, list_to_binary(ContentType)},
            {data, Content}
        ]) ||
        {Name, {ContentType, _}, Content} <-
        proplists:get_all_values("_attachments", Form)
    ],
    #doc{atts=OldAtts} = Doc,
    OldAtts2 = lists:flatmap(
        fun(Att) ->
            OldName = couch_att:fetch(name, Att),
            case [1 || A <- UpdatedAtts, couch_att:fetch(name, A) == OldName] of
            [] -> [Att]; % the attachment wasn't in the UpdatedAtts, return it
            _ -> [] % the attachment was in the UpdatedAtts, drop it
            end
        end, OldAtts),
    NewDoc = Doc#doc{
        atts = UpdatedAtts ++ OldAtts2
    },
    case fabric:update_doc(Db, NewDoc, Options) of
    {ok, NewRev} ->
        HttpCode = 201;
    {accepted, NewRev} ->
        HttpCode = 202
    end,
    send_json(Req, HttpCode, [{"ETag", "\"" ++ ?b2l(couch_doc:rev_to_str(NewRev)) ++ "\""}], {[
        {ok, true},
        {id, DocId},
        {rev, couch_doc:rev_to_str(NewRev)}
    ]});

db_doc_req(#httpd{method='PUT', user_ctx=Ctx}=Req, Db, DocId) ->
    #doc_query_args{
        update_type = UpdateType
    } = parse_doc_query(Req),
    couch_doc:validate_docid(DocId),

    W = chttpd:qs_value(Req, "w", integer_to_list(mem3:quorum(Db))),
    Options = [{user_ctx,Ctx}, {w,W}],

    Loc = absolute_uri(Req, [$/, couch_util:url_encode(Db#db.name),
        $/, couch_util:url_encode(DocId)]),
    RespHeaders = [{"Location", Loc}],
    case couch_util:to_list(couch_httpd:header_value(Req, "Content-Type")) of
    ("multipart/related;" ++ _) = ContentType ->
        couch_httpd:check_max_request_length(Req),
        couch_httpd_multipart:num_mp_writers(mem3:n(mem3:dbname(Db#db.name), DocId)),
        {ok, Doc0, WaitFun, Parser} = couch_doc:doc_from_multi_part_stream(ContentType,
                fun() -> receive_request_data(Req) end),
        Doc = couch_doc_from_req(Req, DocId, Doc0),
        try
            Result = send_updated_doc(Req, Db, DocId, Doc, RespHeaders, UpdateType),
            WaitFun(),
            Result
        catch throw:Err ->
            % Document rejected by a validate_doc_update function.
            couch_httpd_multipart:abort_multipart_stream(Parser),
            throw(Err)
        end;
    _Else ->
        case chttpd:qs_value(Req, "batch") of
        "ok" ->
            % batch
            Doc = couch_doc_from_req(Req, DocId, chttpd:json_body(Req)),

            spawn(fun() ->
                    case catch(fabric:update_doc(Db, Doc, Options)) of
                    {ok, _} -> ok;
                    {accepted, _} -> ok;
                    Error ->
                        couch_log:notice("Batch doc error (~s): ~p",[DocId, Error])
                    end
                end),
            send_json(Req, 202, [], {[
                {ok, true},
                {id, DocId}
            ]});
        _Normal ->
            % normal
            Body = chttpd:json_body(Req),
            Doc = couch_doc_from_req(Req, DocId, Body),
            send_updated_doc(Req, Db, DocId, Doc, RespHeaders, UpdateType)
        end
    end;

db_doc_req(#httpd{method='COPY', user_ctx=Ctx}=Req, Db, SourceDocId) ->
    SourceRev =
    case extract_header_rev(Req, chttpd:qs_value(Req, "rev")) of
        missing_rev -> nil;
        Rev -> Rev
    end,
    {TargetDocId, TargetRevs} = couch_httpd_db:parse_copy_destination_header(Req),
    % open old doc
    Doc = couch_doc_open(Db, SourceDocId, SourceRev, []),
    % save new doc
    case fabric:update_doc(Db,
        Doc#doc{id=TargetDocId, revs=TargetRevs}, [{user_ctx,Ctx}]) of
    {ok, NewTargetRev} ->
        HttpCode = 201;
    {accepted, NewTargetRev} ->
        HttpCode = 202
    end,
    % respond
    {PartRes} = update_doc_result_to_json(TargetDocId, {ok, NewTargetRev}),
    Loc = absolute_uri(Req, "/" ++ couch_util:url_encode(Db#db.name) ++ "/" ++ couch_util:url_encode(TargetDocId)),
    send_json(Req, HttpCode,
        [{"Location", Loc},
        {"ETag", "\"" ++ ?b2l(couch_doc:rev_to_str(NewTargetRev)) ++ "\""}],
        {[{ok, true}] ++ PartRes});

db_doc_req(Req, _Db, _DocId) ->
    send_method_not_allowed(Req, "DELETE,GET,HEAD,POST,PUT,COPY").

send_doc(Req, Doc, Options) ->
    case Doc#doc.meta of
    [] ->
        DiskEtag = couch_httpd:doc_etag(Doc),
        % output etag only when we have no meta
        chttpd:etag_respond(Req, DiskEtag, fun() ->
            send_doc_efficiently(Req, Doc, [{"ETag", DiskEtag}], Options)
        end);
    _ ->
        send_doc_efficiently(Req, Doc, [], Options)
    end.

send_doc_efficiently(Req, #doc{atts=[]}=Doc, Headers, Options) ->
        send_json(Req, 200, Headers, couch_doc:to_json_obj(Doc, Options));
send_doc_efficiently(#httpd{mochi_req=MochiReq}=Req, #doc{atts=Atts}=Doc, Headers, Options) ->
    case lists:member(attachments, Options) of
    true ->
        Refs = monitor_attachments(Atts),
        try
        case MochiReq:accepts_content_type("multipart/related") of
        false ->
            send_json(Req, 200, Headers, couch_doc:to_json_obj(Doc, Options));
        true ->
            Boundary = couch_uuids:random(),
            JsonBytes = ?JSON_ENCODE(couch_doc:to_json_obj(Doc,
                    [attachments, follows, att_encoding_info | Options])),
            {ContentType, Len} = couch_doc:len_doc_to_multi_part_stream(
                    Boundary,JsonBytes, Atts, true),
            CType = {"Content-Type", ContentType},
            {ok, Resp} = start_response_length(Req, 200, [CType|Headers], Len),
            couch_doc:doc_to_multi_part_stream(Boundary,JsonBytes,Atts,
                    fun(Data) -> couch_httpd:send(Resp, Data) end, true)
        end
        after
            demonitor_refs(Refs)
        end;
    false ->
        send_json(Req, 200, Headers, couch_doc:to_json_obj(Doc, Options))
    end.

send_docs_multipart(Req, Results, Options1) ->
    OuterBoundary = couch_uuids:random(),
    InnerBoundary = couch_uuids:random(),
    Options = [attachments, follows, att_encoding_info | Options1],
    CType = {"Content-Type",
        "multipart/mixed; boundary=\"" ++ ?b2l(OuterBoundary) ++ "\""},
    {ok, Resp} = start_chunked_response(Req, 200, [CType]),
    couch_httpd:send_chunk(Resp, <<"--", OuterBoundary/binary>>),
    lists:foreach(
        fun({ok, #doc{atts=Atts}=Doc}) ->
            Refs = monitor_attachments(Doc#doc.atts),
            try
            JsonBytes = ?JSON_ENCODE(couch_doc:to_json_obj(Doc, Options)),
            {ContentType, _Len} = couch_doc:len_doc_to_multi_part_stream(
                    InnerBoundary, JsonBytes, Atts, true),
            couch_httpd:send_chunk(Resp, <<"\r\nContent-Type: ",
                    ContentType/binary, "\r\n\r\n">>),
            couch_doc:doc_to_multi_part_stream(InnerBoundary, JsonBytes, Atts,
                    fun(Data) -> couch_httpd:send_chunk(Resp, Data)
                    end, true),
             couch_httpd:send_chunk(Resp, <<"\r\n--", OuterBoundary/binary>>)
            after
                demonitor_refs(Refs)
            end;
        ({{not_found, missing}, RevId}) ->
             RevStr = couch_doc:rev_to_str(RevId),
             Json = ?JSON_ENCODE({[{<<"missing">>, RevStr}]}),
             couch_httpd:send_chunk(Resp,
                [<<"\r\nContent-Type: application/json; error=\"true\"\r\n\r\n">>,
                Json,
                <<"\r\n--", OuterBoundary/binary>>])
         end, Results),
    couch_httpd:send_chunk(Resp, <<"--">>),
    couch_httpd:last_chunk(Resp).

receive_request_data(Req) ->
    receive_request_data(Req, chttpd:body_length(Req)).

receive_request_data(Req, LenLeft) when LenLeft > 0 ->
    Len = erlang:min(4096, LenLeft),
    Data = chttpd:recv(Req, Len),
    {Data, fun() -> receive_request_data(Req, LenLeft - iolist_size(Data)) end};
receive_request_data(_Req, _) ->
    throw(<<"expected more data">>).

update_doc_result_to_json({{Id, Rev}, Error}) ->
        {_Code, Err, Msg} = chttpd:error_info(Error),
        {[{id, Id}, {rev, couch_doc:rev_to_str(Rev)},
            {error, Err}, {reason, Msg}]}.

update_doc_result_to_json(#doc{id=DocId}, Result) ->
    update_doc_result_to_json(DocId, Result);
update_doc_result_to_json(DocId, {ok, NewRev}) ->
    {[{ok, true}, {id, DocId}, {rev, couch_doc:rev_to_str(NewRev)}]};
update_doc_result_to_json(DocId, {accepted, NewRev}) ->
    {[{ok, true}, {id, DocId}, {rev, couch_doc:rev_to_str(NewRev)}, {accepted, true}]};
update_doc_result_to_json(DocId, Error) ->
    {_Code, ErrorStr, Reason} = chttpd:error_info(Error),
    {[{id, DocId}, {error, ErrorStr}, {reason, Reason}]}.


send_updated_doc(Req, Db, DocId, Json) ->
    send_updated_doc(Req, Db, DocId, Json, []).

send_updated_doc(Req, Db, DocId, Doc, Headers) ->
    send_updated_doc(Req, Db, DocId, Doc, Headers, interactive_edit).

send_updated_doc(#httpd{user_ctx=Ctx} = Req, Db, DocId, #doc{deleted=Deleted}=Doc,
        Headers, UpdateType) ->
    W = chttpd:qs_value(Req, "w", integer_to_list(mem3:quorum(Db))),
    Options =
        case couch_httpd:header_value(Req, "X-Couch-Full-Commit") of
        "true" ->
            [full_commit, UpdateType, {user_ctx,Ctx}, {w,W}];
        "false" ->
            [delay_commit, UpdateType, {user_ctx,Ctx}, {w,W}];
        _ ->
            [UpdateType, {user_ctx,Ctx}, {w,W}]
        end,
    {Status, {etag, Etag}, Body} = update_doc(Db, DocId,
        #doc{deleted=Deleted}=Doc, Options),
    HttpCode = http_code_from_status(Status),
    ResponseHeaders = [{"ETag", Etag} | Headers],
    send_json(Req, HttpCode, ResponseHeaders, Body).

http_code_from_status(Status) ->
    case Status of
        accepted ->
            202;
        created ->
            201;
        ok ->
            200
    end.

update_doc(Db, DocId, #doc{deleted=Deleted, body=DocBody}=Doc, Options) ->
    {_, Ref} = spawn_monitor(fun() ->
        try fabric:update_doc(Db, Doc, Options) of
            Resp ->
                exit({exit_ok, Resp})
        catch
            throw:Reason ->
                exit({exit_throw, Reason});
            error:Reason ->
                exit({exit_error, Reason});
            exit:Reason ->
                exit({exit_exit, Reason})
        end
    end),
    Result = receive
        {'DOWN', Ref, _, _, {exit_ok, Ret}} ->
            Ret;
        {'DOWN', Ref, _, _, {exit_throw, Reason}} ->
            throw(Reason);
        {'DOWN', Ref, _, _, {exit_error, Reason}} ->
            erlang:error(Reason);
        {'DOWN', Ref, _, _, {exit_exit, Reason}} ->
            erlang:exit(Reason)
    end,

    case Result of
    {ok, NewRev} ->
        Accepted = false;
    {accepted, NewRev} ->
        Accepted = true
    end,
    Etag = couch_httpd:doc_etag(DocId, DocBody, NewRev),
    Status = case {Accepted, Deleted} of
        {true, _} ->
            accepted;
        {false, true} ->
            ok;
        {false, false} ->
            created
    end,
    NewRevStr = couch_doc:rev_to_str(NewRev),
    Body = {[{ok, true}, {id, DocId}, {rev, NewRevStr}]},
    {Status, {etag, Etag}, Body}.

couch_doc_from_req(Req, DocId, #doc{revs=Revs} = Doc) ->
    validate_attachment_names(Doc),
    Rev = case chttpd:qs_value(Req, "rev") of
    undefined ->
        undefined;
    QSRev ->
        couch_doc:parse_rev(QSRev)
    end,
    Revs2 =
    case Revs of
    {Start, [RevId|_]} ->
        if Rev /= undefined andalso Rev /= {Start, RevId} ->
            throw({bad_request, "Document rev from request body and query "
                   "string have different values"});
        true ->
            case extract_header_rev(Req, {Start, RevId}) of
            missing_rev -> {0, []};
            _ -> Revs
            end
        end;
    _ ->
        case extract_header_rev(Req, Rev) of
        missing_rev -> {0, []};
        {Pos, RevId2} -> {Pos, [RevId2]}
        end
    end,
    Doc#doc{id=DocId, revs=Revs2};
couch_doc_from_req(Req, DocId, Json) ->
    couch_doc_from_req(Req, DocId, couch_doc:from_json_obj(Json)).


% Useful for debugging
% couch_doc_open(Db, DocId) ->
%   couch_doc_open(Db, DocId, nil, []).

couch_doc_open(#db{} = Db, DocId, Rev, Options0) ->
    Options = [{user_ctx, Db#db.user_ctx} | Options0],
    case Rev of
    nil -> % open most recent rev
        case fabric:open_doc(Db, DocId, Options) of
        {ok, Doc} ->
            Doc;
         Error ->
             throw(Error)
         end;
    _ -> % open a specific rev (deletions come back as stubs)
        case fabric:open_revs(Db, DocId, [Rev], Options) of
        {ok, [{ok, Doc}]} ->
            Doc;
        {ok, [{{not_found, missing}, Rev}]} ->
            throw(not_found);
        {ok, [Else]} ->
            throw(Else);
        {error, Error} ->
            throw(Error)
      end
  end.

% Attachment request handlers

db_attachment_req(#httpd{method='GET',mochi_req=MochiReq}=Req, Db, DocId, FileNameParts) ->
    FileName = list_to_binary(mochiweb_util:join(lists:map(fun binary_to_list/1,
        FileNameParts),"/")),
    #doc_query_args{
        rev=Rev,
        options=Options
    } = parse_doc_query(Req),
    #doc{
        atts=Atts
    } = Doc = couch_doc_open(Db, DocId, Rev, Options),
    case [A || A <- Atts, couch_att:fetch(name, A) == FileName] of
    [] ->
        throw({not_found, "Document is missing attachment"});
    [Att] ->
        [Type, Enc, DiskLen, AttLen, Md5] = couch_att:fetch([type, encoding, disk_len, att_len, md5], Att),
        Refs = monitor_attachments(Att),
        try
        Etag = case Md5 of
            <<>> -> chttpd:doc_etag(Doc);
            _ -> "\"" ++ ?b2l(base64:encode(Md5)) ++ "\""
        end,
        ReqAcceptsAttEnc = lists:member(
           atom_to_list(Enc),
           couch_httpd:accepted_encodings(Req)
        ),
        Headers = [
            {"ETag", Etag},
            {"Cache-Control", "must-revalidate"},
            {"Content-Type", binary_to_list(Type)}
        ] ++ case ReqAcceptsAttEnc of
        true when Enc =/= identity ->
            % RFC 2616 says that the 'identify' encoding should not be used in
            % the Content-Encoding header
            [{"Content-Encoding", atom_to_list(Enc)}];
        _ ->
            []
        end ++ case Enc of
            identity ->
                [{"Accept-Ranges", "bytes"}];
            _ ->
                [{"Accept-Ranges", "none"}]
        end,
        Len = case {Enc, ReqAcceptsAttEnc} of
        {identity, _} ->
            % stored and served in identity form
            DiskLen;
        {_, false} when DiskLen =/= AttLen ->
            % Stored encoded, but client doesn't accept the encoding we used,
            % so we need to decode on the fly.  DiskLen is the identity length
            % of the attachment.
            DiskLen;
        {_, true} ->
            % Stored and served encoded.  AttLen is the encoded length.
            AttLen;
        _ ->
            % We received an encoded attachment and stored it as such, so we
            % don't know the identity length.  The client doesn't accept the
            % encoding, and since we cannot serve a correct Content-Length
            % header we'll fall back to a chunked response.
            undefined
        end,
        AttFun = case ReqAcceptsAttEnc of
        false ->
            fun couch_att:foldl_decode/3;
        true ->
            fun couch_att:foldl/3
        end,
        chttpd:etag_respond(
            Req,
            Etag,
            fun() ->
                case Len of
                undefined ->
                    {ok, Resp} = start_chunked_response(Req, 200, Headers),
                    AttFun(Att, fun(Seg, _) -> send_chunk(Resp, Seg) end, {ok, Resp}),
                    couch_httpd:last_chunk(Resp);
                _ ->
                    Ranges = parse_ranges(MochiReq:get(range), Len),
                    case {Enc, Ranges} of
                        {identity, [{From, To}]} ->
                            Headers1 = [{"Content-Range", make_content_range(From, To, Len)}]
                                ++ Headers,
                            {ok, Resp} = start_response_length(Req, 206, Headers1, To - From + 1),
                            couch_att:range_foldl(Att, From, To + 1,
                                fun(Seg, _) -> send(Resp, Seg) end, {ok, Resp});
                        {identity, Ranges} when is_list(Ranges) andalso length(Ranges) < 10 ->
                            send_ranges_multipart(Req, Type, Len, Att, Ranges);
                        _ ->
                            Headers1 = Headers ++
                                if Enc =:= identity orelse ReqAcceptsAttEnc =:= true ->
                                    [{"Content-MD5", base64:encode(couch_att:fetch(md5, Att))}];
                                true ->
                                    []
                            end,
                            {ok, Resp} = start_response_length(Req, 200, Headers1, Len),
                            AttFun(Att, fun(Seg, _) -> send(Resp, Seg) end, {ok, Resp})
                    end
                end
            end
        )
        after
            demonitor_refs(Refs)
        end
    end;


db_attachment_req(#httpd{method=Method, user_ctx=Ctx}=Req, Db, DocId, FileNameParts)
        when (Method == 'PUT') or (Method == 'DELETE') ->
    FileName = validate_attachment_name(
                    mochiweb_util:join(
                        lists:map(fun binary_to_list/1,
                            FileNameParts),"/")),

    NewAtt = case Method of
        'DELETE' ->
            [];
        _ ->
            MimeType = case couch_httpd:header_value(Req,"Content-Type") of
                % We could throw an error here or guess by the FileName.
                % Currently, just giving it a default.
                undefined -> <<"application/octet-stream">>;
                CType -> list_to_binary(CType)
            end,
            Data = fabric:att_receiver(Req, chttpd:body_length(Req)),
            ContentLen = case couch_httpd:header_value(Req,"Content-Length") of
                undefined -> undefined;
                Length -> list_to_integer(Length)
            end,
            ContentEnc = string:to_lower(string:strip(
                couch_httpd:header_value(Req, "Content-Encoding", "identity")
            )),
            Encoding = case ContentEnc of
                "identity" ->
                    identity;
                "gzip" ->
                    gzip;
                _ ->
                    throw({
                        bad_ctype,
                        "Only gzip and identity content-encodings are supported"
                    })
            end,
            [couch_att:new([
                {name, FileName},
                {type, MimeType},
                {data, Data},
                {att_len, ContentLen},
                {md5, get_md5_header(Req)},
                {encoding, Encoding}
            ])]
    end,

    Doc = case extract_header_rev(Req, chttpd:qs_value(Req, "rev")) of
        missing_rev -> % make the new doc
            couch_doc:validate_docid(DocId),
            #doc{id=DocId};
        Rev ->
            case fabric:open_revs(Db, DocId, [Rev], [{user_ctx,Ctx}]) of
            {ok, [{ok, Doc0}]}  -> Doc0;
            {ok, [Error]}       -> throw(Error);
            {error, Error}      -> throw(Error)
            end
    end,

    #doc{atts=Atts} = Doc,
    DocEdited = Doc#doc{
        atts = NewAtt ++ [A || A <- Atts, couch_att:fetch(name, A) /= FileName]
    },
    W = chttpd:qs_value(Req, "w", integer_to_list(mem3:quorum(Db))),
    case fabric:update_doc(Db, DocEdited, [{user_ctx,Ctx}, {w,W}]) of
    {ok, UpdatedRev} ->
        HttpCode = 201;
    {accepted, UpdatedRev} ->
        HttpCode = 202
    end,
    erlang:put(mochiweb_request_recv, true),
    #db{name=DbName} = Db,

    {Status, Headers} = case Method of
        'DELETE' ->
            {200, []};
        _ ->
            {HttpCode, [{"Location", absolute_uri(Req, [$/, DbName, $/, couch_util:url_encode(DocId), $/,
                FileName])}]}
        end,
    send_json(Req,Status, Headers, {[
        {ok, true},
        {id, DocId},
        {rev, couch_doc:rev_to_str(UpdatedRev)}
    ]});

db_attachment_req(Req, _Db, _DocId, _FileNameParts) ->
    send_method_not_allowed(Req, "DELETE,GET,HEAD,PUT").

send_ranges_multipart(Req, ContentType, Len, Att, Ranges) ->
    Boundary = couch_uuids:random(),
    CType = {"Content-Type",
        "multipart/byteranges; boundary=\"" ++ ?b2l(Boundary) ++ "\""},
    {ok, Resp} = start_chunked_response(Req, 206, [CType]),
    couch_httpd:send_chunk(Resp, <<"--", Boundary/binary>>),
    lists:foreach(fun({From, To}) ->
        ContentRange = make_content_range(From, To, Len),
        couch_httpd:send_chunk(Resp,
            <<"\r\nContent-Type: ", ContentType/binary, "\r\n",
            "Content-Range: ", ContentRange/binary, "\r\n",
           "\r\n">>),
        couch_att:range_foldl(Att, From, To + 1,
            fun(Seg, _) -> send_chunk(Resp, Seg) end, {ok, Resp}),
        couch_httpd:send_chunk(Resp, <<"\r\n--", Boundary/binary>>)
    end, Ranges),
    couch_httpd:send_chunk(Resp, <<"--">>),
    couch_httpd:last_chunk(Resp),
    {ok, Resp}.

parse_ranges(undefined, _Len) ->
    undefined;
parse_ranges(fail, _Len) ->
    undefined;
parse_ranges(Ranges, Len) ->
    parse_ranges(Ranges, Len, []).

parse_ranges([], _Len, Acc) ->
    lists:reverse(Acc);
parse_ranges([{0, none}|_], _Len, _Acc) ->
    undefined;
parse_ranges([{From, To}|_], _Len, _Acc) when is_integer(From) andalso is_integer(To) andalso To < From ->
    throw(requested_range_not_satisfiable);
parse_ranges([{From, To}|Rest], Len, Acc)
  when is_integer(To) andalso To >= Len ->
    parse_ranges([{From, Len-1}] ++ Rest, Len, Acc);
parse_ranges([{none, To}|Rest], Len, Acc) ->
    parse_ranges([{Len - To, Len - 1}] ++ Rest, Len, Acc);
parse_ranges([{From, none}|Rest], Len, Acc) ->
    parse_ranges([{From, Len - 1}] ++ Rest, Len, Acc);
parse_ranges([{From,To}|Rest], Len, Acc) ->
    parse_ranges(Rest, Len, [{From, To}] ++ Acc).

make_content_range(From, To, Len) ->
    ?l2b(io_lib:format("bytes ~B-~B/~B", [From, To, Len])).

get_md5_header(Req) ->
    ContentMD5 = couch_httpd:header_value(Req, "Content-MD5"),
    Length = couch_httpd:body_length(Req),
    Trailer = couch_httpd:header_value(Req, "Trailer"),
    case {ContentMD5, Length, Trailer} of
        _ when is_list(ContentMD5) orelse is_binary(ContentMD5) ->
            base64:decode(ContentMD5);
        {_, chunked, undefined} ->
            <<>>;
        {_, chunked, _} ->
            case re:run(Trailer, "\\bContent-MD5\\b", [caseless]) of
                {match, _} ->
                    md5_in_footer;
                _ ->
                    <<>>
            end;
        _ ->
            <<>>
    end.

parse_doc_query(Req) ->
    lists:foldl(fun parse_doc_query/2, #doc_query_args{}, chttpd:qs(Req)).

parse_doc_query({Key, Value}, Args) ->
    case {Key, Value} of
        {"attachments", "true"} ->
            Options = [attachments | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"meta", "true"} ->
            Options = [revs_info, conflicts, deleted_conflicts | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"revs", "true"} ->
            Options = [revs | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"local_seq", "true"} ->
            Options = [local_seq | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"revs_info", "true"} ->
            Options = [revs_info | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"conflicts", "true"} ->
            Options = [conflicts | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"deleted", "true"} ->
            Options = [deleted | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"deleted_conflicts", "true"} ->
            Options = [deleted_conflicts | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"rev", Rev} ->
            Args#doc_query_args{rev=couch_doc:parse_rev(Rev)};
        {"open_revs", "all"} ->
            Args#doc_query_args{open_revs=all};
        {"open_revs", RevsJsonStr} ->
            JsonArray = ?JSON_DECODE(RevsJsonStr),
            Args#doc_query_args{open_revs=couch_doc:parse_revs(JsonArray)};
        {"latest", "true"} ->
            Options = [latest | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"atts_since", RevsJsonStr} ->
            JsonArray = ?JSON_DECODE(RevsJsonStr),
            Args#doc_query_args{atts_since = couch_doc:parse_revs(JsonArray)};
        {"new_edits", "false"} ->
            Args#doc_query_args{update_type=replicated_changes};
        {"new_edits", "true"} ->
            Args#doc_query_args{update_type=interactive_edit};
        {"att_encoding_info", "true"} ->
            Options = [att_encoding_info | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"r", R} ->
            Options = [{r,R} | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        {"w", W} ->
            Options = [{w,W} | Args#doc_query_args.options],
            Args#doc_query_args{options=Options};
        _Else -> % unknown key value pair, ignore.
            Args
    end.

parse_changes_query(Req) ->
    erlang:erase(changes_seq_interval),
    ChangesArgs = lists:foldl(fun({Key, Value}, Args) ->
        case {string:to_lower(Key), Value} of
        {"feed", "live"} ->
            %% sugar for continuous
            Args#changes_args{feed="continuous"};
        {"feed", _} ->
            Args#changes_args{feed=Value};
        {"descending", "true"} ->
            Args#changes_args{dir=rev};
        {"since", _} ->
            Args#changes_args{since=Value};
        {"last-event-id", _} ->
            Args#changes_args{since=Value};
        {"limit", _} ->
            Args#changes_args{limit=list_to_integer(Value)};
        {"style", _} ->
            Args#changes_args{style=list_to_existing_atom(Value)};
        {"heartbeat", "true"} ->
            Args#changes_args{heartbeat=true};
        {"heartbeat", _} ->
            Args#changes_args{heartbeat=list_to_integer(Value)};
        {"timeout", _} ->
            Args#changes_args{timeout=list_to_integer(Value)};
        {"include_docs", "true"} ->
            Args#changes_args{include_docs=true};
        {"conflicts", "true"} ->
            Args#changes_args{conflicts=true};
        {"attachments", "true"} ->
            Options = [attachments | Args#changes_args.doc_options],
            Args#changes_args{doc_options=Options};
        {"att_encoding_info", "true"} ->
            Options = [att_encoding_info | Args#changes_args.doc_options],
            Args#changes_args{doc_options=Options};
        {"filter", _} ->
            Args#changes_args{filter=Value};
        {"seq_interval", _} ->
            try list_to_integer(Value) of
                V when V > 0 ->
                    erlang:put(changes_seq_interval, V),
                    Args;
                _ ->
                    throw({bad_request, invalid_seq_interval})
            catch error:badarg ->
                throw({bad_request, invalid_seq_interval})
            end;
        _Else -> % unknown key value pair, ignore.
            Args
        end
    end, #changes_args{}, chttpd:qs(Req)),
    %% if it's an EventSource request with a Last-event-ID header
    %% that should override the `since` query string, since it's
    %% probably the browser reconnecting.
    case ChangesArgs#changes_args.feed of
        "eventsource" ->
            case couch_httpd:header_value(Req, "last-event-id") of
                undefined ->
                    ChangesArgs;
                Value ->
                    ChangesArgs#changes_args{since=Value}
            end;
        _ ->
            ChangesArgs
    end.

extract_header_rev(Req, ExplicitRev) when is_binary(ExplicitRev) or is_list(ExplicitRev)->
    extract_header_rev(Req, couch_doc:parse_rev(ExplicitRev));
extract_header_rev(Req, ExplicitRev) ->
    Etag = case chttpd:header_value(Req, "If-Match") of
        undefined -> undefined;
        Value -> couch_doc:parse_rev(string:strip(Value, both, $"))
    end,
    case {ExplicitRev, Etag} of
    {undefined, undefined} -> missing_rev;
    {_, undefined} -> ExplicitRev;
    {undefined, _} -> Etag;
    _ when ExplicitRev == Etag -> Etag;
    _ ->
        throw({bad_request, "Document rev and etag have different values"})
    end.


validate_attachment_names(Doc) ->
    lists:foreach(fun(Att) ->
        Name = couch_att:fetch(name, Att),
        validate_attachment_name(Name)
    end, Doc#doc.atts).

validate_attachment_name(Name) when is_list(Name) ->
    validate_attachment_name(list_to_binary(Name));
validate_attachment_name(<<"_",Rest/binary>>) ->
    throw({bad_request, <<"Attachment name '_", Rest/binary,
                          "' starts with prohibited character '_'">>});
validate_attachment_name(Name) ->
    case couch_util:validate_utf8(Name) of
        true -> Name;
        false -> throw({bad_request, <<"Attachment name is not UTF-8 encoded">>})
    end.

-spec monitor_attachments(couch_att:att() | [couch_att:att()]) -> [reference()].
monitor_attachments(Atts) when is_list(Atts) ->
    lists:foldl(fun(Att, Monitors) ->
        case couch_att:fetch(data, Att) of
            {Fd, _} ->
                [monitor(process, Fd) | Monitors];
            stub ->
                Monitors;
            Else ->
                couch_log:error("~p from couch_att:fetch(data, ~p)", [Else, Att]),
                Monitors
        end
    end, [], Atts);
monitor_attachments(Att) ->
    monitor_attachments([Att]).

demonitor_refs(Refs) when is_list(Refs) ->
    [demonitor(Ref) || Ref <- Refs].

set_namespace(<<"_all_docs">>, Args) ->
    set_namespace(undefined, Args);
set_namespace(<<"_local_docs">>, Args) ->
    set_namespace(<<"_local">>, Args);
set_namespace(<<"_design_docs">>, Args) ->
    set_namespace(<<"_design">>, Args);
set_namespace(NS, #mrargs{extra = Extra} = Args) ->
    Args#mrargs{extra = [{namespace, NS} | Extra]}.


%% /db/_bulk_get stuff

bulk_get_parse_doc_query(Req) ->
    lists:foldl(fun({Key, Value}, Args) ->
        ok = validate_query_param(Key),
        parse_doc_query({Key, Value}, Args)
    end, #doc_query_args{}, chttpd:qs(Req)).


validate_query_param("open_revs"=Key) ->
    throw_bad_query_param(Key);
validate_query_param("new_edits"=Key) ->
    throw_bad_query_param(Key);
validate_query_param("w"=Key) ->
    throw_bad_query_param(Key);
validate_query_param("rev"=Key) ->
    throw_bad_query_param(Key);
validate_query_param("atts_since"=Key) ->
    throw_bad_query_param(Key);
validate_query_param(_) ->
    ok.

throw_bad_query_param(Key) when is_list(Key) ->
    throw_bad_query_param(?l2b(Key));
throw_bad_query_param(Key) when is_binary(Key) ->
    Msg = <<"\"", Key/binary, "\" query parameter is not acceptable">>,
    throw({bad_request, Msg}).


bulk_get_open_doc_revs(Db, {Props}, Options) ->
    bulk_get_open_doc_revs1(Db, Props, Options, {}).


bulk_get_open_doc_revs1(Db, Props, Options, {}) ->
    case parse_field(<<"id">>, couch_util:get_value(<<"id">>, Props)) of
        {error, {DocId, Error, Reason}} ->
            {DocId, {error, {null, Error, Reason}}, Options};

        {ok, undefined} ->
            Error = {null, bad_request, <<"document id missed">>},
            {null, {error, Error}, Options};

        {ok, DocId} ->
            bulk_get_open_doc_revs1(Db, Props, Options, {DocId})
    end;
bulk_get_open_doc_revs1(Db, Props, Options, {DocId}) ->
    RevStr = couch_util:get_value(<<"rev">>, Props),

    case parse_field(<<"rev">>, RevStr) of
        {error, {RevStr, Error, Reason}} ->
            {DocId, {error, {RevStr, Error, Reason}}, Options};

        {ok, undefined} ->
            bulk_get_open_doc_revs1(Db, Props, Options, {DocId, all});

        {ok, Rev} ->
            bulk_get_open_doc_revs1(Db, Props, Options, {DocId, [Rev]})
    end;
bulk_get_open_doc_revs1(Db, Props, Options, {DocId, Revs}) ->
    AttsSinceStr = couch_util:get_value(<<"atts_since">>, Props),

    case parse_field(<<"atts_since">>, AttsSinceStr) of
        {error, {BadAttsSinceRev, Error, Reason}} ->
            {DocId, {error, {BadAttsSinceRev, Error, Reason}}, Options};

        {ok, []} ->
            bulk_get_open_doc_revs1(Db, Props, Options, {DocId, Revs, Options});

        {ok, RevList} ->
            Options1 = [{atts_since, RevList}, attachments | Options],
            bulk_get_open_doc_revs1(Db, Props, Options, {DocId, Revs, Options1})
    end;
bulk_get_open_doc_revs1(Db, Props, _, {DocId, Revs, Options}) ->
    case fabric:open_revs(Db, DocId, Revs, Options) of
        {ok, []} ->
            RevStr = couch_util:get_value(<<"rev">>, Props),
            Error = {RevStr, <<"not_found">>, <<"missing">>},
            {DocId, {error, Error}, Options};
        Results ->
            {DocId, Results, Options}
    end.


parse_field(<<"id">>, undefined) ->
    {ok, undefined};
parse_field(<<"id">>, Value) ->
    try
        ok = couch_doc:validate_docid(Value),
        {ok, Value}
    catch
        throw:{Error, Reason} ->
            {error, {Value, Error, Reason}}
    end;
parse_field(<<"rev">>, undefined) ->
    {ok, undefined};
parse_field(<<"rev">>, Value) ->
    try
        Rev = couch_doc:parse_rev(Value),
        {ok, Rev}
    catch
        throw:{bad_request=Error, Reason} ->
            {error, {Value, Error, Reason}}
    end;
parse_field(<<"atts_since">>, undefined) ->
    {ok, []};
parse_field(<<"atts_since">>, []) ->
    {ok, []};
parse_field(<<"atts_since">>, Value) when is_list(Value) ->
    parse_atts_since(Value, []);
parse_field(<<"atts_since">>, Value) ->
    {error, {Value, bad_request, <<"att_since value must be array of revs.">>}}.


parse_atts_since([], Acc) ->
    {ok, lists:reverse(Acc)};
parse_atts_since([RevStr | Rest], Acc) ->
    case parse_field(<<"rev">>, RevStr) of
        {ok, Rev} ->
            parse_atts_since(Rest, [Rev | Acc]);
        {error, _}=Error ->
            Error
    end.


bulk_get_send_docs_json(Resp, DocId, Results, Options, Sep) ->
    Id = ?JSON_ENCODE(DocId),
    send_chunk(Resp, [Sep, <<"{\"id\": ">>, Id, <<", \"docs\": [">>]),
    bulk_get_send_docs_json1(Resp, DocId, Results, Options),
    send_chunk(Resp, <<"]}">>).

bulk_get_send_docs_json1(Resp, DocId, {error, {Rev, Error, Reason}}, _) ->
    send_chunk(Resp, [bulk_get_json_error(DocId, Rev, Error, Reason)]);
bulk_get_send_docs_json1(_Resp, _DocId, {ok, []}, _) ->
    ok;
bulk_get_send_docs_json1(Resp, DocId, {ok, Docs}, Options) ->
    lists:foldl(fun(Result, AccSeparator) ->
        case Result of
            {ok, Doc} ->
                JsonDoc = couch_doc:to_json_obj(Doc, Options),
                Json = ?JSON_ENCODE({[{ok, JsonDoc}]}),
                send_chunk(Resp, [AccSeparator, Json]);
            {{Error, Reason}, RevId} ->
                RevStr = couch_doc:rev_to_str(RevId),
                Json = bulk_get_json_error(DocId, RevStr, Error, Reason),
                send_chunk(Resp, [AccSeparator, Json])
        end,
        <<",">>
    end, <<"">>, Docs).

bulk_get_json_error(DocId, Rev, Error, Reason) ->
    ?JSON_ENCODE({[{error, {[{<<"id">>, DocId},
                             {<<"rev">>, Rev},
                             {<<"error">>, Error},
                             {<<"reason">>, Reason}]}}]}).


-ifdef(TEST).
-include_lib("eunit/include/eunit.hrl").

monitor_attachments_test_() ->
    {"ignore stubs",
        fun () ->
            Atts = [couch_att:new([{data, stub}])],
            ?_assertEqual([], monitor_attachments(Atts))
        end
    }.

-endif.