% 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_show).

-export([handle_doc_show_req/3, handle_doc_update_req/3, handle_view_list_req/3]).

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

% /db/_design/foo/_show/bar/docid
% show converts a json doc to a response of any content-type.
% it looks up the doc an then passes it to the query server.
% then it sends the response from the query server to the http client.

maybe_open_doc(Db, DocId) ->
    case fabric:open_doc(Db, DocId, [conflicts]) of
    {ok, Doc} ->
        Doc;
    {not_found, _} ->
        nil
    end.

handle_doc_show_req(#httpd{
        path_parts=[_, _, _, _, ShowName, DocId]
    }=Req, Db, DDoc) ->

    % open the doc
    Doc = maybe_open_doc(Db, DocId),

    % we don't handle revs here b/c they are an internal api
    % returns 404 if there is no doc with DocId
    handle_doc_show(Req, Db, DDoc, ShowName, Doc, DocId);

handle_doc_show_req(#httpd{
        path_parts=[_, _, _, _, ShowName, DocId|Rest]
    }=Req, Db, DDoc) ->

    DocParts = [DocId|Rest],
    DocId1 = ?l2b(string:join([?b2l(P)|| P <- DocParts], "/")),

    % open the doc
    Doc = maybe_open_doc(Db, DocId1),

    % we don't handle revs here b/c they are an internal api
    % pass 404 docs to the show function
    handle_doc_show(Req, Db, DDoc, ShowName, Doc, DocId1);

handle_doc_show_req(#httpd{
        path_parts=[_, _, _, _, ShowName]
    }=Req, Db, DDoc) ->
    % with no docid the doc is nil
    handle_doc_show(Req, Db, DDoc, ShowName, nil);

handle_doc_show_req(Req, _Db, _DDoc) ->
    chttpd:send_error(Req, 404, <<"show_error">>, <<"Invalid path.">>).

handle_doc_show(Req, Db, DDoc, ShowName, Doc) ->
    handle_doc_show(Req, Db, DDoc, ShowName, Doc, null).

handle_doc_show(Req, Db, DDoc, ShowName, Doc, DocId) ->
    %% Will throw an exception if the _show handler is missing
    couch_util:get_nested_json_value(DDoc#doc.body, [<<"shows">>, ShowName]),
    % get responder for ddoc/showname
    CurrentEtag = show_etag(Req, Doc, DDoc, []),
    chttpd:etag_respond(Req, CurrentEtag, fun() ->
        JsonReq = chttpd_external:json_req_obj(Req, Db, DocId),
        JsonDoc = couch_query_servers:json_doc(Doc),
        [<<"resp">>, ExternalResp] =
            couch_query_servers:ddoc_prompt(DDoc, [<<"shows">>, ShowName],
                [JsonDoc, JsonReq]),
        JsonResp = apply_etag(ExternalResp, CurrentEtag),
        chttpd_external:send_external_response(Req, JsonResp)
    end).


show_etag(#httpd{user_ctx=UserCtx}=Req, Doc, DDoc, More) ->
    Accept = chttpd:header_value(Req, "Accept"),
    DocPart = case Doc of
        nil -> nil;
        Doc -> chttpd:doc_etag(Doc)
    end,
    couch_httpd:make_etag({couch_httpd:doc_etag(DDoc), DocPart, Accept,
        UserCtx#user_ctx.roles, More}).

% /db/_design/foo/update/bar/docid
% updates a doc based on a request
% handle_doc_update_req(#httpd{method = 'GET'}=Req, _Db, _DDoc) ->
%     % anything but GET
%     send_method_not_allowed(Req, "POST,PUT,DELETE,ETC");

handle_doc_update_req(#httpd{
        path_parts=[_, _, _, _, UpdateName, DocId]
    }=Req, Db, DDoc) ->
    Doc = maybe_open_doc(Db, DocId),
    send_doc_update_response(Req, Db, DDoc, UpdateName, Doc, DocId);

handle_doc_update_req(#httpd{
        path_parts=[_, _, _, _, UpdateName]
    }=Req, Db, DDoc) ->
    send_doc_update_response(Req, Db, DDoc, UpdateName, nil, null);

handle_doc_update_req(Req, _Db, _DDoc) ->
    chttpd:send_error(Req, 404, <<"update_error">>, <<"Invalid path.">>).

send_doc_update_response(Req, Db, DDoc, UpdateName, Doc, DocId) ->
    %% Will throw an exception if the _update handler is missing
    couch_util:get_nested_json_value(DDoc#doc.body, [<<"updates">>, UpdateName]),
    JsonReq = chttpd_external:json_req_obj(Req, Db, DocId),
    JsonDoc = couch_query_servers:json_doc(Doc),
    Cmd = [<<"updates">>, UpdateName],
    W = couch_httpd:qs_value(Req, "w", integer_to_list(mem3:quorum(Db))),
    UpdateResp = couch_query_servers:ddoc_prompt(DDoc, Cmd, [JsonDoc, JsonReq]),
    JsonResp = case UpdateResp of
        [<<"up">>, {NewJsonDoc}, {JsonResp0}] ->
            case chttpd:header_value(Req, "X-Couch-Full-Commit", "false") of
            "true" ->
                Options = [full_commit, {user_ctx, Req#httpd.user_ctx}, {w, W}];
            _ ->
                Options = [{user_ctx, Req#httpd.user_ctx}, {w, W}]
            end,
            NewDoc = couch_doc:from_json_obj({NewJsonDoc}),
            couch_doc:validate_docid(NewDoc#doc.id),
            {UpdateResult, NewRev} = fabric:update_doc(Db, NewDoc, Options),
            NewRevStr = couch_doc:rev_to_str(NewRev),
            case {UpdateResult, NewRev} of
            {ok, _} ->
                Code = 201;
            {accepted, _} ->
                Code = 202
            end,
            {[
                {<<"code">>, Code},
                {<<"headers">>, {[
                    {<<"X-Couch-Update-NewRev">>, NewRevStr},
                    {<<"X-Couch-Id">>, NewDoc#doc.id}
                ]}}
                | JsonResp0]};
        [<<"up">>, _Other, {JsonResp0}] ->
            {[{<<"code">>, 200} | JsonResp0]}
    end,
    % todo set location field
    chttpd_external:send_external_response(Req, JsonResp).


% view-list request with view and list from same design doc.
handle_view_list_req(#httpd{method='GET',
        path_parts=[_, _, DesignName, _, ListName, ViewName]}=Req, Db, DDoc) ->
    Keys = chttpd:qs_json_value(Req, "keys", undefined),
    handle_view_list(Req, Db, DDoc, ListName, {DesignName, ViewName}, Keys);

% view-list request with view and list from different design docs.
handle_view_list_req(#httpd{method='GET',
        path_parts=[_, _, _, _, ListName, DesignName, ViewName]}=Req, Db, DDoc) ->
    Keys = chttpd:qs_json_value(Req, "keys", undefined),
    handle_view_list(Req, Db, DDoc, ListName, {DesignName, ViewName}, Keys);

handle_view_list_req(#httpd{method='GET'}=Req, _Db, _DDoc) ->
    chttpd:send_error(Req, 404, <<"list_error">>, <<"Invalid path.">>);

handle_view_list_req(#httpd{method='POST',
        path_parts=[_, _, DesignName, _, ListName, ViewName]}=Req, Db, DDoc) ->
    ReqBody = chttpd:body(Req),
    {Props2} = ?JSON_DECODE(ReqBody),
    Keys = proplists:get_value(<<"keys">>, Props2, undefined),
    handle_view_list(Req#httpd{req_body=ReqBody}, Db, DDoc, ListName,
        {DesignName, ViewName}, Keys);

handle_view_list_req(#httpd{method='POST',
        path_parts=[_, _, _, _, ListName, DesignName, ViewName]}=Req, Db, DDoc) ->
    ReqBody = chttpd:body(Req),
    {Props2} = ?JSON_DECODE(ReqBody),
    Keys = proplists:get_value(<<"keys">>, Props2, undefined),
    handle_view_list(Req#httpd{req_body=ReqBody}, Db, DDoc, ListName,
        {DesignName, ViewName}, Keys);

handle_view_list_req(#httpd{method='POST'}=Req, _Db, _DDoc) ->
    chttpd:send_error(Req, 404, <<"list_error">>, <<"Invalid path.">>);

handle_view_list_req(Req, _Db, _DDoc) ->
    chttpd:send_method_not_allowed(Req, "GET,POST,HEAD").

handle_view_list(Req, Db, DDoc, LName, {ViewDesignName, ViewName}, Keys) ->
    %% Will throw an exception if the _list handler is missing
    couch_util:get_nested_json_value(DDoc#doc.body, [<<"lists">>, LName]),
    {ok, VDoc} = ddoc_cache:open(Db#db.name, <<"_design/", ViewDesignName/binary>>),
    CB = fun couch_mrview_show:list_cb/2,
    Etag = couch_uuids:new(),
    QueryArgs = couch_mrview_http:parse_params(Req, Keys),
    Options = [{user_ctx, Req#httpd.user_ctx}],
    chttpd:etag_respond(Req, Etag, fun() ->
        couch_query_servers:with_ddoc_proc(DDoc, fun(QServer) ->
            Acc = #lacc{
                lname = LName,
                req = Req,
                qserver = QServer,
                db = Db,
                etag = Etag
            },
            case ViewName of
                <<"_all_docs">> ->
                    fabric:all_docs(Db, Options, CB, Acc, QueryArgs);
                _ ->
                    fabric:query_view(Db, VDoc, ViewName, CB, Acc, QueryArgs)
            end
        end)
    end).

% Maybe this is in the proplists API
% todo move to couch_util
json_apply_field(H, {L}) ->
    json_apply_field(H, L, []).
json_apply_field({Key, NewValue}, [{Key, _OldVal} | Headers], Acc) ->
    % drop matching keys
    json_apply_field({Key, NewValue}, Headers, Acc);
json_apply_field({Key, NewValue}, [{OtherKey, OtherVal} | Headers], Acc) ->
    % something else is next, leave it alone.
    json_apply_field({Key, NewValue}, Headers, [{OtherKey, OtherVal} | Acc]);
json_apply_field({Key, NewValue}, [], Acc) ->
    % end of list, add ours
    {[{Key, NewValue}|Acc]}.

apply_etag({ExternalResponse}, CurrentEtag) ->
    % Here we embark on the delicate task of replacing or creating the
    % headers on the JsonResponse object. We need to control the Etag and
    % Vary headers. If the external function controls the Etag, we'd have to
    % run it to check for a match, which sort of defeats the purpose.
    case couch_util:get_value(<<"headers">>, ExternalResponse, nil) of
    nil ->
        % no JSON headers
        % add our Etag and Vary headers to the response
        {[{<<"headers">>, {[{<<"Etag">>, CurrentEtag}, {<<"Vary">>, <<"Accept">>}]}} | ExternalResponse]};
    JsonHeaders ->
        {[case Field of
        {<<"headers">>, JsonHeaders} -> % add our headers
            JsonHeadersEtagged = json_apply_field({<<"Etag">>, CurrentEtag}, JsonHeaders),
            JsonHeadersVaried = json_apply_field({<<"Vary">>, <<"Accept">>}, JsonHeadersEtagged),
            {<<"headers">>, JsonHeadersVaried};
        _ -> % skip non-header fields
            Field
        end || Field <- ExternalResponse]}
    end.