From f4d7191a3c0c37fe7b2ba290ba3e1afda0269863 Mon Sep 17 00:00:00 2001
From: Adam Kocoloski <adam@cloudant.com>
Date: Fri, 11 Jun 2010 16:08:05 -0400
Subject: _changes feed via fabric

---
 src/chttpd_db.erl | 102 ++++++++++++++++++++++++++++++------------------------
 1 file changed, 57 insertions(+), 45 deletions(-)

diff --git a/src/chttpd_db.erl b/src/chttpd_db.erl
index 3b35220a..10388ff5 100644
--- a/src/chttpd_db.erl
+++ b/src/chttpd_db.erl
@@ -47,56 +47,69 @@ handle_request(#httpd{path_parts=[DbName|RestParts],method=Method,
     end.
 
 handle_changes_req(#httpd{method='GET'}=Req, Db) ->
-    MakeCallback = fun(Resp) ->
-        fun({change, Change, _}, "continuous") ->
-            send_chunk(Resp, [?JSON_ENCODE(Change) | "\n"]);
-        ({change, Change, Prepend}, _) ->
-            send_chunk(Resp, [Prepend, ?JSON_ENCODE(Change)]);
-        (start, "continuous") ->
-            ok;
-        (start, _) ->
-            send_chunk(Resp, "{\"results\":[\n");
-        ({stop, EndSeq}, "continuous") ->
-            send_chunk(
-                Resp,
-                [?JSON_ENCODE({[{<<"last_seq">>, EndSeq}]}) | "\n"]
-            ),
-            end_json_response(Resp);
-        ({stop, EndSeq}, _) ->
-            send_chunk(
-                Resp,
-                io_lib:format("\n],\n\"last_seq\":~w}\n", [EndSeq])
-            ),
-            end_json_response(Resp);
-        (timeout, _) ->
-            send_chunk(Resp, "\n")
-        end
-    end,
     ChangesArgs = parse_changes_query(Req),
-    ChangesFun = couch_changes:handle_changes(ChangesArgs, Req, Db),
     case ChangesArgs#changes_args.feed of
     "normal" ->
-        {ok, Info} = couch_db:get_db_info(Db),
-        CurrentEtag = chttpd:make_etag(Info),
-        chttpd:etag_respond(
-            Req,
-            CurrentEtag,
-            fun() ->
-                {ok, Resp} = chttpd:start_json_response(
-                     Req, 200, [{"Etag", CurrentEtag}]
-                ),
-                ChangesFun(MakeCallback(Resp))
-            end
-        );
-    _ ->
+        T0 = now(),
+        {ok, Info} = fabric:get_db_info(Db),
+        Etag = chttpd:make_etag(Info),
+        DeltaT = timer:now_diff(now(), T0) / 1000,
+        couch_stats_collector:record({couchdb, dbinfo}, DeltaT),
+        chttpd:etag_respond(Req, Etag, fun() ->
+            {ok, Resp} = chttpd:start_json_response(Req, 200, [{"Etag",Etag}]),
+            fabric:changes(Db, ChangesArgs, fun changes_callback/2,
+                {"normal", Resp})
+        end);
+    Feed ->
         % "longpoll" or "continuous"
         {ok, Resp} = chttpd:start_json_response(Req, 200),
-        ChangesFun(MakeCallback(Resp))
+        fabric:changes(Db, ChangesArgs, fun changes_callback/2, {Feed, Resp})
     end;
-
 handle_changes_req(#httpd{path_parts=[_,<<"_changes">>]}=Req, _Db) ->
     send_method_not_allowed(Req, "GET,HEAD").
 
+% callbacks for continuous feed (newline-delimited JSON Objects)
+changes_callback(start, {"continuous", _} = Acc) ->
+    {ok, Acc};
+changes_callback({change, Change}, {"continuous", Resp} = Acc) ->
+    send_chunk(Resp, [?JSON_ENCODE(Change) | "\n"]),
+    {ok, Acc};
+changes_callback({stop, EndSeq0}, {"continuous", Resp}) ->
+    EndSeq = case is_old_couch(Resp) of true -> 0; false -> EndSeq0 end,
+    send_chunk(Resp, [?JSON_ENCODE({[{<<"last_seq">>, EndSeq}]}) | "\n"]),
+    end_json_response(Resp);
+
+% callbacks for longpoll and normal (single JSON Object)
+changes_callback(start, {_, Resp}) ->
+    send_chunk(Resp, "{\"results\":[\n"),
+    {ok, {"", Resp}};
+changes_callback({change, Change}, {Prepend, Resp}) ->
+    send_chunk(Resp, [Prepend, ?JSON_ENCODE(Change)]),
+    {ok, {",\r\n", Resp}};
+changes_callback({stop, EndSeq}, {_, Resp}) ->
+    case is_old_couch(Resp) of
+    true ->
+        send_chunk(Resp, "\n],\n\"last_seq\":0}\n");
+    false ->
+        send_chunk(Resp, io_lib:format("\n],\n\"last_seq\":\"~s\"}\n",[EndSeq]))
+    end,
+    end_json_response(Resp);
+
+changes_callback(timeout, {Prepend, Resp}) ->
+    send_chunk(Resp, "\n"),
+    {ok, {Prepend, Resp}};
+changes_callback({error, Reason}, Resp) ->
+    chttpd:send_chunked_error(Resp, {error, Reason}).
+
+is_old_couch(Resp) ->
+    MochiReq = Resp:get(request),
+    case MochiReq:get_header_value("user-agent") of
+    undefined ->
+        false;
+    UserAgent ->
+        string:str(UserAgent, "CouchDB/0") > 0
+    end.
+
 handle_compact_req(#httpd{method='POST',path_parts=[DbName,_,Id|_]}=Req, _Db) ->
     ok = ?COUCH:compact_view_group(DbName, Id),
     send_json(Req, 202, {[{ok, true}]});
@@ -382,7 +395,7 @@ all_docs_view(Req, Db, Keys) ->
     {ok, Info} = fabric:get_db_info(Db),
     Etag = couch_httpd:make_etag(Info),
     DeltaT = timer:now_diff(now(), T0) / 1000,
-    couch_stats_collector:record({couchdb, all_docs_etag}, DeltaT),
+    couch_stats_collector:record({couchdb, dbinfo}, DeltaT),
     QueryArgs = chttpd_view:parse_view_params(Req, Keys, map),
     chttpd:etag_respond(Req, Etag, fun() ->
         {ok, Resp} = chttpd:start_json_response(Req, 200, [{"Etag",Etag}]),
@@ -398,8 +411,7 @@ all_docs_callback({row, Row}, {Prepend, Resp}) ->
     {ok, {",\r\n", Resp}};
 all_docs_callback(complete, {_, Resp}) ->
     send_chunk(Resp, "\r\n]}"),
-    end_json_response(Resp),
-    {ok, Resp};
+    end_json_response(Resp);
 all_docs_callback({error, Reason}, Resp) ->
     chttpd:send_chunked_error(Resp, {error, Reason}).
 
@@ -780,7 +792,7 @@ parse_changes_query(Req) ->
         {"descending", "true"} ->
             Args#changes_args{dir=rev};
         {"since", _} ->
-            Args#changes_args{since=list_to_integer(Value)};
+            Args#changes_args{since=Value};
         {"limit", _} ->
             Args#changes_args{limit=list_to_integer(Value)};
         {"style", _} ->
-- 
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