%% Copyright (c) 2011-2017, Loïc Hoguin <essen@ninenines.eu>
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

%% Handler middleware.
%%
%% Execute the handler given by the <em>handler</em> and <em>handler_opts</em>
%% environment values. The result of this execution is added to the
%% environment under the <em>result</em> value.
-module(dreki_web_handler).
-include_lib("opentelemetry_api/include/otel_tracer.hrl").
-behaviour(cowboy_middleware).

-export([execute/2]).
-export([terminate/4]).

-callback init(Req, any())
	-> {ok | module(), Req, any()}
	| {module(), Req, any(), any()}
	when Req::cowboy_req:req().

-callback terminate(any(), map(), any()) -> ok.
-optional_callbacks([terminate/3]).

-spec execute(Req, Env) -> {ok, Req, Env}
	when Req::cowboy_req:req(), Env::cowboy_middleware:env().
execute(Req, Env=#{handler := Handler}) ->
    Headers = maps:get(headers, Req),
    otel_propagator_text_map:extract(maps:to_list(Headers)),
    HandlerB = atom_to_binary(Handler),
    Method = maps:get(method, Req),
    Attributes = [
                  {'http.host', maps:get(host, Req)},
                  {'http.host.port', maps:get(port, Req)},
                  {'http.method', Method},
                  {'http.scheme', maps:get(scheme, Req)},
                  {'http.target', maps:get(path, Req)},
                  {'http.user_agent', maps:get(<<"user-agent">>, Headers, <<"">>)}
                 ],
    SpanName = iolist_to_binary([<<"HTTP ">>, Method, <<" ">>, HandlerB]),
    logger:debug("SpanName: ~p", [SpanName]),
    ?with_span(SpanName, #{}, fun(Ctx) -> execute_(Req, Env, Ctx) end).

execute_(Req0, Env=#{handler := Handler, handler_opts := HandlerOpts}, Ctx) ->
    TraceId = otel_span:hex_trace_id(otel_tracer:current_span_ctx()),
    Req = Req0#{<<"trace-id">> => TraceId},
	try Handler:init(Req, HandlerOpts) of
		{ok, Req2, State} ->
          Headers0 = maps:get(headers, Req2),
          Headers = otel_propagator_text_map:inject(Headers0,
                                                    fun(Headers, Key, Value) ->
                                                            maps:put(Key, Value, Headers)
                                                    end),
          Req3 = maps:put(headers, Headers, Req2),
          Result = terminate(normal, Req3, State, Handler),
          {ok, Req3, Env#{result => Result, trace_id => TraceId}};
		{Mod, Req2, State} ->
          ?add_event(<<"HTTP_UPGRADE">>, #{module => Mod}),
			Mod:upgrade(Req2, Env, Handler, State);
		{Mod, Req2, State, Opts} ->
          ?add_event(<<"HTTP_UPGRADE">>, #{module => Mod}),
			Mod:upgrade(Req2, Env, Handler, State, Opts)
	catch Class:Reason:Stacktrace ->
          ?set_status(error, iolist_to_binary([atom_to_binary(Class)])),
          render_error(Class, Reason, Stacktrace, Handler, Req, Env, Ctx)
  end.

render_error(Class, Reason, Stacktrace, Handler, Req, Env, Ctx) ->
		ReasonS = lists:flatten(io_lib:format("~p", [Reason])),
		Assigns = [
         {dreki_node, node()},
			   {site_title, "Dreki"},
         {class, atom_to_binary(Class)},
			   {reason, ReasonS},
			   {stacktrace, [lists:flatten(io_lib:format("~p", [Line])) || Line <- Stacktrace]},
         {trace_id, maps:get(<<"trace-id">>, Req, <<"no-trace">>)}
			],
		logger:error(#{app => dreki_web, handler => Handler, error => {Class, Reason, Stacktrace}}),
		{ok, Html} = crash_dtl:render(Assigns),
		cowboy_req:reply(500, #{<<"content-type">> => <<"text/html">>}, Html, Req).

-spec terminate(any(), Req | undefined, any(), module()) -> ok when Req::cowboy_req:req().
terminate(Reason, Req, State, Handler) ->
	case erlang:function_exported(Handler, terminate, 3) of
		true ->
			Handler:terminate(Reason, Req, State);
		false ->
			ok
	end.