ibrowse/src/ibrowse.erl

%%%-------------------------------------------------------------------
%%% File    : ibrowse.erl
%%% Author  : Chandrashekhar Mullaparthi <chandrashekhar.mullaparthi@t-mobile.co.uk>
%%% Description : Load balancer process for HTTP client connections.
%%%
%%% Created : 11 Oct 2003 by Chandrashekhar Mullaparthi <chandrashekhar.mullaparthi@t-mobile.co.uk>
%%%-------------------------------------------------------------------
%% @author Chandrashekhar Mullaparthi <chandrashekhar dot mullaparthi at gmail dot com>
%% @copyright 2005-2014 Chandrashekhar Mullaparthi
%% @doc The ibrowse application implements an HTTP 1.1 client in erlang. This
%% module implements the API of the HTTP client. There is one named
%% process called 'ibrowse' which assists in load balancing and maintaining configuration. There is one load balancing process per unique webserver. There is
%% one process to handle one TCP connection to a webserver
%% (implemented in the module ibrowse_http_client). Multiple connections to a
%% webserver are setup based on the settings for each webserver. The
%% ibrowse process also determines which connection to pipeline a
%% certain request on.  The functions to call are send_req/3,
%% send_req/4, send_req/5, send_req/6.
%%
%% <p>Here are a few sample invocations.</p>
%%
%% <code>
%% ibrowse:send_req("http://intranet/messenger/", [], get). 
%% <br/><br/>
%% 
%% ibrowse:send_req("http://www.google.com/", [], get, [], 
%%               [{proxy_user, "XXXXX"},
%%                {proxy_password, "XXXXX"},
%%                {proxy_host, "proxy"},
%%                {proxy_port, 8080}], 1000). 
%% <br/><br/>
%%
%%ibrowse:send_req("http://www.erlang.org/download/otp_src_R10B-3.tar.gz", [], get, [],
%%               [{proxy_user, "XXXXX"},
%%                {proxy_password, "XXXXX"},
%%                {proxy_host, "proxy"},
%%                {proxy_port, 8080},
%%                {save_response_to_file, true}], 1000).
%% <br/><br/>
%%
%% ibrowse:send_req("http://www.erlang.org", [], head).
%%
%% <br/><br/>
%% ibrowse:send_req("http://www.sun.com", [], options).
%%
%% <br/><br/>
%% ibrowse:send_req("http://www.bbc.co.uk", [], trace).
%%
%% <br/><br/>
%% ibrowse:send_req("http://www.google.com", [], get, [], 
%%                   [{stream_to, self()}]).
%% </code>
%%

-module(ibrowse).
-behaviour(gen_server).
%%--------------------------------------------------------------------
%% Include files
%%--------------------------------------------------------------------

%%--------------------------------------------------------------------
%% External exports
-export([start_link/0, start/0, stop/0]).

%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
         terminate/2, code_change/3]).

%% API interface
-export([
         rescan_config/0,
         rescan_config/1,
         add_config/1,
         get_config_value/1,
         get_config_value/2,
         spawn_worker_process/1,
         spawn_worker_process/2,
         spawn_link_worker_process/1,
         spawn_link_worker_process/2,
         stop_worker_process/1,
         send_req/3,
         send_req/4,
         send_req/5,
         send_req/6,
         send_req_direct/4,
         send_req_direct/5,
         send_req_direct/6,
         send_req_direct/7,
         stream_next/1,
         stream_close/1,
         set_max_sessions/3,
         set_max_pipeline_size/3,
         set_dest/3,
         trace_on/0,
         trace_off/0,
         trace_on/2,
         trace_off/2,
         all_trace_off/0,
         show_dest_status/0,
         show_dest_status/1,
         show_dest_status/2,
         get_metrics/0,
         get_metrics/2
        ]).

-ifdef(debug).
-compile(export_all).
-endif.

-import(ibrowse_lib, [
                      parse_url/1,
                      get_value/3,
                      do_trace/2
                     ]).
                      
-record(state, {trace = false}).

-include("ibrowse.hrl").
-include_lib("stdlib/include/ms_transform.hrl").

-define(DEF_MAX_SESSIONS,10).
-define(DEF_MAX_PIPELINE_SIZE,10).

%%====================================================================
%% External functions
%%====================================================================
%%--------------------------------------------------------------------
%% Function: start_link/0
%% Description: Starts the server
%%--------------------------------------------------------------------
%% @doc Starts the ibrowse process linked to the calling process. Usually invoked by the supervisor ibrowse_sup
%% @spec start_link() -> {ok, pid()}
start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

%% @doc Starts the ibrowse process without linking. Useful when testing using the shell
start() ->
    gen_server:start({local, ?MODULE}, ?MODULE, [], [{debug, []}]).

%% @doc Stop the ibrowse process. Useful when testing using the shell.
stop() ->
    case catch gen_server:call(ibrowse, stop) of
        {'EXIT',{noproc,_}} ->
            ok;
        Res ->
            Res
    end.

%% @doc This is the basic function to send a HTTP request.
%% The Status return value indicates the HTTP status code returned by the webserver
%% @spec send_req(Url::string(), Headers::headerList(), Method::method()) -> response()
%% headerList() = [{header(), value()}]
%% header() = atom() | string() | binary()
%% value() = term()
%% method() = get | post | head | options | put | delete | trace | mkcol | propfind | proppatch | lock | unlock | move | copy
%% Status = string()
%% ResponseHeaders = [respHeader()]
%% respHeader() = {headerName(), headerValue()}
%% headerName() = string()
%% headerValue() = string()
%% response() = {ok, Status, ResponseHeaders, ResponseBody} | {ok, Status, ResponseHeaders, ResponseBody} | {ibrowse_req_id, req_id() } | {error, Reason}
%% req_id() = term()
%% ResponseBody = string() | {file, Filename}
%% Reason = term()
send_req(Url, Headers, Method) ->
    send_req(Url, Headers, Method, [], []).

%% @doc Same as send_req/3. 
%% If a list is specified for the body it has to be a flat list. The body can also be a fun/0 or a fun/1. <br/>
%% If fun/0, the connection handling process will repeatdely call the fun until it returns an error or eof. <pre>Fun() = {ok, Data} | eof</pre><br/>
%% If fun/1, the connection handling process will repeatedly call the fun with the supplied state until it returns an error or eof. <pre>Fun(State) = {ok, Data} | {ok, Data, NewState} | eof</pre>
%% @spec send_req(Url, Headers, Method::method(), Body::body()) -> response()
%% body() = [] | string() | binary() | fun_arity_0() | {fun_arity_1(), initial_state()}
%% initial_state() = term()
send_req(Url, Headers, Method, Body) ->
    send_req(Url, Headers, Method, Body, []).

%% @doc Same as send_req/4.

%% For a description of SSL Options, look in the <a href="http://www.erlang.org/doc/apps/ssl/index.html">ssl</a> manpage.
%% For a description of Process Options, look in the <a href="http://www.erlang.org/doc/man/gen_server.html">gen_server</a> manpage.
%% If the HTTP Version to use is not specified, the default is 1.1.
%% <br/>
%% <ul>
%% <li>The <code>host_header</code> option is useful in the case where ibrowse is
%% connecting to a component such as <a
%% href="http://www.stunnel.org">stunnel</a> which then sets up a
%% secure connection to a webserver. In this case, the URL supplied to
%% ibrowse must have the stunnel host/port details, but that won't
%% make sense to the destination webserver. This option can then be
%% used to specify what should go in the <code>Host</code> header in
%% the request.</li>
%% <li>The <code>stream_to</code> option can be used to have the HTTP
%% response streamed to a process as messages as data arrives on the
%% socket. If the calling process wishes to control the rate at which
%% data is received from the server, the option <code>{stream_to,
%% {process(), once}}</code> can be specified. The calling process
%% will have to invoke <code>ibrowse:stream_next(Request_id)</code> to
%% receive the next packet.</li>
%%
%% <li>When both the options <code>save_response_to_file</code> and <code>stream_to</code> 
%% are specified, the former takes precedence.</li>
%%
%% <li>For the <code>save_response_to_file</code> option, the response body is saved to
%% file only if the status code is in the 200-299 range. If not, the response body is returned
%% as a string.</li>
%% <li>Whenever an error occurs in the processing of a request, ibrowse will return as much
%% information as it has, such as HTTP Status Code and HTTP Headers. When this happens, the response
%% is of the form <code>{error, {Reason, {stat_code, StatusCode}, HTTP_headers}}</code></li>
%%
%% <li>The <code>inactivity_timeout</code> option is useful when
%% dealing with large response bodies and/or slow links. In these
%% cases, it might be hard to estimate how long a request will take to
%% complete. In such cases, the client might want to timeout if no
%% data has been received on the link for a certain time interval.
%% 
%% This value is also used to close connections which are not in use for 
%% the specified timeout value.
%% </li>
%%
%% <li>
%% The <code>connect_timeout</code> option is to specify how long the
%% client process should wait for connection establishment. This is
%% useful in scenarios where connections to servers are usually setup
%% very fast, but responses might take much longer compared to
%% connection setup. In such cases, it is better for the calling
%% process to timeout faster if there is a problem (DNS lookup
%% delays/failures, network routing issues, etc). The total timeout
%% value specified for the request will enforced. To illustrate using
%% an example:
%% <code>
%% ibrowse:send_req("http://www.example.com/cgi-bin/request", [], get, [], [{connect_timeout, 100}], 1000).
%% </code>
%% In the above invocation, if the connection isn't established within
%% 100 milliseconds, the request will fail with 
%% <code>{error, conn_failed}</code>.<br/>
%% If connection setup succeeds, the total time allowed for the
%% request to complete will be 1000 milliseconds minus the time taken
%% for connection setup.
%% </li>
%% 
%% <li> The <code>socket_options</code> option can be used to set
%% specific options on the socket. The <code>{active, true | false | once}</code> 
%% and <code>{packet_type, Packet_type}</code> will be filtered out by ibrowse.  </li>
%%
%% <li> The <code>headers_as_is</code> option is to enable the caller
%% to send headers exactly as specified in the request without ibrowse
%% adding some of its own. Required for some picky servers apparently.  </li>
%%
%% <li>The <code>give_raw_headers</code> option is to enable the
%% caller to get access to the raw status line and raw unparsed
%% headers. Not quite sure why someone would want this, but one of my
%% users asked for it, so here it is. </li>
%%
%% <li> The <code>preserve_chunked_encoding</code> option enables the caller
%% to receive the raw data stream when the Transfer-Encoding of the server
%% response is Chunked.
%% </li>
%% <li> The <code>return_raw_request</code> option enables the caller to get the exact request which was sent by ibrowse to the server, along with the response. When this option is used, the response for synchronous requests is a 5-tuple instead of the usual 4-tuple. For asynchronous requests, the calling process gets a message <code>{ibrowse_async_raw_req, Raw_req}</code>. 
%% </li>
%% </ul>
%%
%% @spec send_req(Url::string(), Headers::headerList(), Method::method(), Body::body(), Options::optionList()) -> response()
%% optionList() = [option()]
%% option() = {max_sessions, integer()}        |
%%          {response_format,response_format()}|
%%          {stream_chunk_size, integer()}     |
%%          {max_pipeline_size, integer()}     |
%%          {trace, boolean()}                 | 
%%          {is_ssl, boolean()}                |
%%          {ssl_options, [SSLOpt]}            |
%%          {pool_name, atom()}                |
%%          {proxy_host, string()}             |
%%          {proxy_port, integer()}            |
%%          {proxy_user, string()}             |
%%          {proxy_password, string()}         |
%%          {use_absolute_uri, boolean()}      |
%%          {basic_auth, {username(), password()}} |
%%          {cookie, string()}                 |
%%          {content_length, integer()}        |
%%          {content_type, string()}           |
%%          {save_response_to_file, srtf()}    |
%%          {stream_to, stream_to()}           |
%%          {http_vsn, {MajorVsn, MinorVsn}}   |
%%          {host_header, string()}            |
%%          {inactivity_timeout, integer()}    |
%%          {connect_timeout, integer()}       |
%%          {socket_options, Sock_opts}        |
%%          {transfer_encoding, {chunked, ChunkSize}} | 
%%          {headers_as_is, boolean()}         |
%%          {give_raw_headers, boolean()}      |
%%          {preserve_chunked_encoding,boolean()}     |
%%          {workaround, head_response_with_body}     |
%%          {worker_process_options, list()} |
%%          {return_raw_request, true}
%%
%% stream_to() = process() | {process(), once}
%% process() = pid() | atom()
%% username() = string()
%% password() = string()
%% SSLOpt = term()
%% Sock_opts = [Sock_opt]
%% Sock_opt = term()
%% ChunkSize = integer()
%% srtf() = boolean() | filename() | {append, filename()}
%% filename() = string()
%% response_format() = list | binary
send_req(Url, Headers, Method, Body, Options) ->
    send_req(Url, Headers, Method, Body, Options, 30000).

%% @doc Same as send_req/5. 
%% All timeout values are in milliseconds.
%% @spec send_req(Url, Headers::headerList(), Method::method(), Body::body(), Options::optionList(), Timeout) -> response()
%% Timeout = integer() | infinity
send_req(Url, Headers, Method, Body, Options, Timeout) ->
    case catch parse_url(Url) of
        #url{host = Host,
             port = Port,
             protocol = Protocol} = Parsed_url ->
            Lb_pid = case ets:lookup(ibrowse_lb, {Host, Port}) of
                         [] ->
                             get_lb_pid(Parsed_url);
                         [#lb_pid{pid = Lb_pid_1}] ->
                             Lb_pid_1
                     end,
            Max_sessions = get_max_sessions(Host, Port, Options),
            Max_pipeline_size = get_max_pipeline_size(Host, Port, Options),
            Options_1 = merge_options(Host, Port, Options),
            {SSLOptions, IsSSL} =
                case (Protocol == https) orelse
                    get_value(is_ssl, Options_1, false) of
                    false -> {[], false};
                    true -> {get_value(ssl_options, Options_1, []), true}
                end,
            try_routing_request(Lb_pid, Parsed_url,
                                Max_sessions, 
                                Max_pipeline_size,
                                {SSLOptions, IsSSL}, 
                                Headers, Method, Body, Options_1, Timeout, 0);
        Err ->
            {error, {url_parsing_failed, Err}}
    end.

try_routing_request(Lb_pid, Parsed_url,
                    Max_sessions, 
                    Max_pipeline_size,
                    {SSLOptions, IsSSL}, 
                    Headers, Method, Body, Options_1, Timeout, Try_count) when Try_count < 3 ->
    ProcessOptions = get_value(worker_process_options, Options_1, []),
    case ibrowse_lb:spawn_connection(Lb_pid, Parsed_url,
                                             Max_sessions, 
                                             Max_pipeline_size,
                                             {SSLOptions, IsSSL},
                                             ProcessOptions) of
        {ok, Conn_Pid} ->
            case do_send_req(Conn_Pid, Parsed_url, Headers,
                             Method, Body, Options_1, Timeout) of
                {error, sel_conn_closed} ->
                    try_routing_request(Lb_pid, Parsed_url,
                                        Max_sessions, 
                                        Max_pipeline_size,
                                        {SSLOptions, IsSSL}, 
                                        Headers, Method, Body, Options_1, Timeout, Try_count + 1);
                Res ->
                    Res
            end;
        Err ->
            Err
    end;
try_routing_request(_, _, _, _, _, _, _, _, _, _, _) ->
    {error, retry_later}.

merge_options(Host, Port, Options) ->
    Config_options = get_config_value({options, Host, Port}, []) ++
                     get_config_value({options, global}, []),
    lists:foldl(
      fun({Key, Val}, Acc) ->
              case lists:keysearch(Key, 1, Options) of
                  false ->
                      [{Key, Val} | Acc];
                  _ ->
                      Acc
              end
      end, Options, Config_options).

get_lb_pid(Url) ->
    gen_server:call(?MODULE, {get_lb_pid, Url}).

get_max_sessions(Host, Port, Options) ->
    get_value(max_sessions, Options,
              get_config_value({max_sessions, Host, Port},
                               default_max_sessions())).

get_max_pipeline_size(Host, Port, Options) ->
    get_value(max_pipeline_size, Options,
              get_config_value({max_pipeline_size, Host, Port},
                               default_max_pipeline_size())).

default_max_sessions() ->
    safe_get_env(ibrowse, default_max_sessions, ?DEF_MAX_SESSIONS).

default_max_pipeline_size() ->
    safe_get_env(ibrowse, default_max_pipeline_size, ?DEF_MAX_PIPELINE_SIZE).

safe_get_env(App, Key, Def_val) ->
    case application:get_env(App, Key) of
        undefined ->
            Def_val;
        {ok, Val} ->
            Val
    end.

%% @doc Deprecated. Use set_max_sessions/3 and set_max_pipeline_size/3
%% for achieving the same effect.
set_dest(Host, Port, [{max_sessions, Max} | T]) ->
    set_max_sessions(Host, Port, Max),
    set_dest(Host, Port, T);
set_dest(Host, Port, [{max_pipeline_size, Max} | T]) ->
    set_max_pipeline_size(Host, Port, Max),
    set_dest(Host, Port, T);
set_dest(Host, Port, [{trace, Bool} | T]) when Bool == true; Bool == false ->
    ibrowse ! {trace, true, Host, Port},
    set_dest(Host, Port, T);
set_dest(_Host, _Port, [H | _]) ->
    exit({invalid_option, H});
set_dest(_, _, []) ->
    ok.
    
%% @doc Set the maximum number of connections allowed to a specific Host:Port.
%% @spec set_max_sessions(Host::string(), Port::integer(), Max::integer()) -> ok
set_max_sessions(Host, Port, Max) when is_integer(Max), Max > 0 ->
    gen_server:call(?MODULE, {set_config_value, {max_sessions, Host, Port}, Max}).

%% @doc Set the maximum pipeline size for each connection to a specific Host:Port.
%% @spec set_max_pipeline_size(Host::string(), Port::integer(), Max::integer()) -> ok
set_max_pipeline_size(Host, Port, Max) when is_integer(Max), Max > 0 ->
    gen_server:call(?MODULE, {set_config_value, {max_pipeline_size, Host, Port}, Max}).

do_send_req(Conn_Pid, Parsed_url, Headers, Method, Body, Options, Timeout) ->
    case catch ibrowse_http_client:send_req(Conn_Pid, Parsed_url,
                                            Headers, Method, ensure_bin(Body),
                                            Options, Timeout) of
        {'EXIT', {timeout, _}} ->
            {error, req_timedout};
        {'EXIT', {noproc, {gen_server, call, [Conn_Pid, _, _]}}} ->
            {error, sel_conn_closed};
        {'EXIT', {normal, _}} ->
            {error, sel_conn_closed};
        {'EXIT', {connection_closed, _}} ->
            {error, sel_conn_closed};
        {error, connection_closed} ->
            {error, sel_conn_closed};
        {'EXIT', Reason} ->
            {error, {'EXIT', Reason}};
        {ok, St_code, Headers, Body} = Ret when is_binary(Body) ->
            case get_value(response_format, Options, list) of
                list ->
                    {ok, St_code, Headers, binary_to_list(Body)};
                binary ->
                    Ret
            end;
        {ok, St_code, Headers, Body, Req} = Ret when is_binary(Body) ->
            case get_value(response_format, Options, list) of
                list ->
                    {ok, St_code, Headers, binary_to_list(Body), Req};
                binary ->
                    Ret
            end;
        Ret ->
            Ret
    end.

ensure_bin(L) when is_list(L)                     -> list_to_binary(L);
ensure_bin(B) when is_binary(B)                   -> B;
ensure_bin(Fun) when is_function(Fun)             -> Fun;
ensure_bin({Fun}) when is_function(Fun)           -> Fun;
ensure_bin({Fun, _} = Body) when is_function(Fun) -> Body.

%% @doc Creates a HTTP client process to the specified Host:Port which
%% is not part of the load balancing pool. This is useful in cases
%% where some requests to a webserver might take a long time whereas
%% some might take a very short time. To avoid getting these quick
%% requests stuck in the pipeline behind time consuming requests, use
%% this function to get a handle to a connection process. <br/>
%% <b>Note:</b> Calling this function only creates a worker process. No connection
%% is setup. The connection attempt is made only when the first
%% request is sent via any of the send_req_direct/4,5,6,7 functions.<br/>
%% <b>Note:</b> It is the responsibility of the calling process to control
%% pipeline size on such connections.

%% @spec spawn_worker_process(Url::string() | {Host::string(), Port::integer()}) -> {ok, pid()}
spawn_worker_process(Args) ->
    spawn_worker_process(Args, []).

%% @doc Same as spawn_worker_process/1 except with Erlang process options.
%% @spec spawn_worker_process(Host::string(), Port::integer()) -> {ok, pid()}
spawn_worker_process(Host, Port) when is_list(Host), is_integer(Port) ->
    %% Convert old API calls to new API format.
    spawn_worker_process({Host, Port}, []);
spawn_worker_process(Args, Options) ->
    ibrowse_http_client:start(Args, Options).

%% @doc Same as spawn_worker_process/1 except the the calling process
%% is linked to the worker process which is spawned.
%% @spec spawn_link_worker_process(Url::string() | {Host::string(), Port::integer()}) -> {ok, pid()}
spawn_link_worker_process(Args) ->
    spawn_link_worker_process(Args, []).

%% @doc Same as spawn_link_worker_process/1 except with Erlang process options.
%% @spec spawn_link_worker_process(Host::string(), Port::integer()) -> {ok, pid()}
spawn_link_worker_process(Host, Port) when is_list(Host), is_integer(Port) ->
    %% Convert old API calls to new API format.
    spawn_link_worker_process({Host, Port}, []);
spawn_link_worker_process(Args, Options) ->
    ibrowse_http_client:start_link(Args, Options).

%% @doc Terminate a worker process spawned using
%% spawn_worker_process/2 or spawn_link_worker_process/2. Requests in
%% progress will get the error response <pre>{error, closing_on_request}</pre>
%% @spec stop_worker_process(Conn_pid::pid()) -> ok
stop_worker_process(Conn_pid) ->
    ibrowse_http_client:stop(Conn_pid).

%% @doc Same as send_req/3 except that the first argument is the PID
%% returned by spawn_worker_process/2 or spawn_link_worker_process/2
send_req_direct(Conn_pid, Url, Headers, Method) ->
    send_req_direct(Conn_pid, Url, Headers, Method, [], []).

%% @doc Same as send_req/4 except that the first argument is the PID
%% returned by spawn_worker_process/2 or spawn_link_worker_process/2
send_req_direct(Conn_pid, Url, Headers, Method, Body) ->
    send_req_direct(Conn_pid, Url, Headers, Method, Body, []).

%% @doc Same as send_req/5 except that the first argument is the PID
%% returned by spawn_worker_process/2 or spawn_link_worker_process/2
send_req_direct(Conn_pid, Url, Headers, Method, Body, Options) ->
    send_req_direct(Conn_pid, Url, Headers, Method, Body, Options, 30000).

%% @doc Same as send_req/6 except that the first argument is the PID
%% returned by spawn_worker_process/2 or spawn_link_worker_process/2
send_req_direct(Conn_pid, Url, Headers, Method, Body, Options, Timeout) ->
    case catch parse_url(Url) of
        #url{host = Host,
             port = Port} = Parsed_url ->
            Options_1 = merge_options(Host, Port, Options),
            case do_send_req(Conn_pid, Parsed_url, Headers, Method, Body, Options_1, Timeout) of
                {error, {'EXIT', {noproc, _}}} ->
                    {error, worker_is_dead};
                Ret ->
                    Ret
            end;
        Err ->
            {error, {url_parsing_failed, Err}}
    end.

%% @doc Tell ibrowse to stream the next chunk of data to the
%% caller. Should be used in conjunction with the
%% <code>stream_to</code> option
%% @spec stream_next(Req_id :: req_id()) -> ok | {error, unknown_req_id}
stream_next(Req_id) ->    
    case ets:lookup(ibrowse_stream, {req_id_pid, Req_id}) of
        [] ->
            {error, unknown_req_id};
        [{_, Pid}] ->
            catch Pid ! {stream_next, Req_id},
            ok
    end.

%% @doc Tell ibrowse to close the connection associated with the
%% specified stream.  Should be used in conjunction with the
%% <code>stream_to</code> option. Note that all requests in progress on
%% the connection which is serving this Req_id will be aborted, and an
%% error returned.
%% @spec stream_close(Req_id :: req_id()) -> ok | {error, unknown_req_id}
stream_close(Req_id) ->    
    case ets:lookup(ibrowse_stream, {req_id_pid, Req_id}) of
        [] ->
            {error, unknown_req_id};
        [{_, Pid}] ->
            catch Pid ! {stream_close, Req_id},
            ok
    end.

%% @doc Turn tracing on for the ibrowse process
trace_on() ->
    ibrowse ! {trace, true}.
%% @doc Turn tracing off for the ibrowse process
trace_off() ->
    ibrowse ! {trace, false}.

%% @doc Turn tracing on for all connections to the specified HTTP
%% server. Host is whatever is specified as the domain name in the URL
%% @spec trace_on(Host, Port) -> ok
%% Host = string() 
%% Port = integer()
trace_on(Host, Port) ->
    ibrowse ! {trace, true, Host, Port},
    ok.

%% @doc Turn tracing OFF for all connections to the specified HTTP
%% server.
%% @spec trace_off(Host, Port) -> ok
trace_off(Host, Port) ->
    ibrowse ! {trace, false, Host, Port},
    ok.

%% @doc Turn Off ALL tracing
%% @spec all_trace_off() -> ok
all_trace_off() ->
    ibrowse ! all_trace_off,
    ok.

%% @doc Shows some internal information about load balancing. Info
%% about workers spawned using spawn_worker_process/2 or
%% spawn_link_worker_process/2 is not included.
show_dest_status() ->
    io:format("~-40.40s | ~-5.5s | ~-10.10s | ~s~n",
              ["Server:port", "ETS", "Num conns", "LB Pid"]),
    io:format("~80.80.=s~n", [""]),
    Metrics = get_metrics(),
    lists:foreach(
      fun({Host, Port, Lb_pid, Tid, Size}) ->
              io:format("~40.40s | ~-5.5s | ~-5.5s | ~p~n",
                        [Host ++ ":" ++ integer_to_list(Port),
                         integer_to_list(Tid),
                         integer_to_list(Size), 
                         Lb_pid])
      end, Metrics).

show_dest_status(Url) ->                                          
    #url{host = Host, port = Port} = ibrowse_lib:parse_url(Url),
    show_dest_status(Host, Port).

%% @doc Shows some internal information about load balancing to a
%% specified Host:Port. Info about workers spawned using
%% spawn_worker_process/2 or spawn_link_worker_process/2 is not
%% included.
show_dest_status(Host, Port) ->
    case get_metrics(Host, Port) of
        {Lb_pid, MsgQueueSize, Tid, Size,
         {{First_p_sz, First_speculative_sz},
          {Last_p_sz, Last_speculative_sz}}} ->
            io:format("Load Balancer Pid     : ~p~n"
                      "LB process msg q size : ~p~n"
                      "LB ETS table id       : ~p~n"
                      "Num Connections       : ~p~n"
                      "Smallest pipeline     : ~p:~p~n"
                      "Largest pipeline      : ~p:~p~n",
                      [Lb_pid, MsgQueueSize, Tid, Size, 
                       First_p_sz, First_speculative_sz,
                       Last_p_sz, Last_speculative_sz]);
        _Err ->
            io:format("Metrics not available~n", [])
    end.

get_metrics() ->
    Dests = lists:filter(fun({lb_pid, {Host, Port}, _}) when is_list(Host),
                                                             is_integer(Port) ->
                                 true;
                            (_) ->
                                 false
                         end, ets:tab2list(ibrowse_lb)),
    All_ets = ets:all(),
    lists:map(fun({lb_pid, {Host, Port}, Lb_pid}) ->
                  case lists:dropwhile(
                         fun(Tid) ->
                                 ets:info(Tid, owner) /= Lb_pid
                         end, All_ets) of
                      [] ->
                          {Host, Port, Lb_pid, unknown, 0};
                      [Tid | _] ->
                          Size = case catch (ets:info(Tid, size)) of
                                     N when is_integer(N) -> N;
                                     _ -> 0
                                 end,
                          {Host, Port, Lb_pid, Tid, Size}
                  end
              end, Dests).

get_metrics(Host, Port) ->
    case ets:lookup(ibrowse_lb, {Host, Port}) of
        [] ->
            no_active_processes;
        [#lb_pid{pid = Lb_pid}] ->
            MsgQueueSize = (catch process_info(Lb_pid, message_queue_len)),
            %% {Lb_pid, MsgQueueSize,
            case lists:dropwhile(
                   fun(Tid) ->
                           ets:info(Tid, owner) /= Lb_pid
                   end, ets:all()) of
                [] ->
                    {Lb_pid, MsgQueueSize, unknown, 0, unknown};
                [Tid | _] ->
                    try
                        Size = ets:info(Tid, size),
                        case Size of
                            0 ->
                                ok;
                            _ ->
                                First = ets:first(Tid),
                                Last = ets:last(Tid),
                                [{_, First_p_sz, First_speculative_sz}] = ets:lookup(Tid, First),
                                [{_, Last_p_sz, Last_speculative_sz}] = ets:lookup(Tid, Last),
                                {Lb_pid, MsgQueueSize, Tid, Size,
                                 {{First_p_sz, First_speculative_sz}, {Last_p_sz, Last_speculative_sz}}}
                        end
                    catch _:_ ->
                            not_available
                    end
            end
    end.

%% @doc Clear current configuration for ibrowse and load from the file
%% ibrowse.conf in the IBROWSE_EBIN/../priv directory. Current
%% configuration is cleared only if the ibrowse.conf file is readable
%% using file:consult/1
rescan_config() ->
    gen_server:call(?MODULE, rescan_config).

%% Clear current configuration for ibrowse and load from the specified
%% file. Current configuration is cleared only if the specified
%% file is readable using file:consult/1
rescan_config([{_,_}|_]=Terms) ->
    gen_server:call(?MODULE, {rescan_config_terms, Terms});
rescan_config(File) when is_list(File) ->
    gen_server:call(?MODULE, {rescan_config, File}).

%% @doc Add additional configuration elements at runtime.
add_config([{_,_}|_]=Terms) ->
    gen_server:call(?MODULE, {add_config_terms, Terms}).

%%====================================================================
%% Server functions
%%====================================================================

%%--------------------------------------------------------------------
%% Function: init/1
%% Description: Initiates the server
%% Returns: {ok, State}          |
%%          {ok, State, Timeout} |
%%          ignore               |
%%          {stop, Reason}
%%--------------------------------------------------------------------
init(_) ->
    process_flag(trap_exit, true),
    State = #state{},
    put(my_trace_flag, State#state.trace),
    put(ibrowse_trace_token, "ibrowse"),
    ibrowse_lb     = ets:new(ibrowse_lb, [named_table, public, {keypos, 2}]),
    ibrowse_conf   = ets:new(ibrowse_conf, [named_table, protected, {keypos, 2}]),
    ibrowse_stream = ets:new(ibrowse_stream, [named_table, public]),
    import_config(),
    {ok, #state{}}.

import_config() ->
    case code:priv_dir(ibrowse) of
        {error, _} ->
            ok;
        PrivDir ->
            Filename = filename:join(PrivDir, "ibrowse.conf"),
            import_config(Filename)
    end.

import_config(Filename) ->
    case file:consult(Filename) of
        {ok, Terms} ->
            apply_config(Terms);
        _Err ->
            ok
    end.

apply_config(Terms) ->
    ets:delete_all_objects(ibrowse_conf),
    insert_config(Terms).

insert_config(Terms) ->
    Fun = fun({dest, Host, Port, MaxSess, MaxPipe, Options}) 
             when is_list(Host), is_integer(Port),
                  is_integer(MaxSess), MaxSess > 0,
                  is_integer(MaxPipe), MaxPipe > 0, is_list(Options) ->
                  I = [{{max_sessions, Host, Port}, MaxSess},
                       {{max_pipeline_size, Host, Port}, MaxPipe},
                       {{options, Host, Port}, Options}],
                  lists:foreach(
                    fun({X, Y}) ->
                            ets:insert(ibrowse_conf,
                                       #ibrowse_conf{key = X, 
                                                     value = Y})
                    end, I);
             ({K, V}) ->
                  ets:insert(ibrowse_conf,
                             #ibrowse_conf{key = K,
                                           value = V});
             (X) ->
                  io:format("Skipping unrecognised term: ~p~n", [X])
          end,
    lists:foreach(Fun, Terms).

%% @doc Internal export
get_config_value(Key) ->
    try
        [#ibrowse_conf{value = V}] = ets:lookup(ibrowse_conf, Key),
        V
    catch
        error:badarg ->
            throw({error, ibrowse_not_running})
    end.

%% @doc Internal export
get_config_value(Key, DefVal) ->
    try
        case ets:lookup(ibrowse_conf, Key) of
            [] ->
                DefVal;
            [#ibrowse_conf{value = V}] ->
                V
        end
    catch
        error:badarg ->
            throw({error, ibrowse_not_running})
    end.

set_config_value(Key, Val) ->
    ets:insert(ibrowse_conf, #ibrowse_conf{key = Key, value = Val}).
%%--------------------------------------------------------------------
%% Function: handle_call/3
%% Description: Handling call messages
%% Returns: {reply, Reply, State}          |
%%          {reply, Reply, State, Timeout} |
%%          {noreply, State}               |
%%          {noreply, State, Timeout}      |
%%          {stop, Reason, Reply, State}   | (terminate/2 is called)
%%          {stop, Reason, State}            (terminate/2 is called)
%%--------------------------------------------------------------------
handle_call({get_lb_pid, #url{host = Host, port = Port} = Url}, _From, State) ->
    Pid = do_get_connection(Url, ets:lookup(ibrowse_lb, {Host, Port})),
    {reply, Pid, State};

handle_call(stop, _From, State) ->
    do_trace("IBROWSE shutting down~n", []),
    ets:foldl(fun(#lb_pid{pid = Pid}, Acc) ->
                      ibrowse_lb:stop(Pid),
                      Acc
              end, [], ibrowse_lb),
    {stop, normal, ok, State};

handle_call({set_config_value, Key, Val}, _From, State) ->
    set_config_value(Key, Val),
    {reply, ok, State};

handle_call(rescan_config, _From, State) ->
    Ret = (catch import_config()),
    {reply, Ret, State};

handle_call({rescan_config, File}, _From, State) ->
    Ret = (catch import_config(File)),
    {reply, Ret, State};

handle_call({rescan_config_terms, Terms}, _From, State) ->
    Ret = (catch apply_config(Terms)),
    {reply, Ret, State};

handle_call({add_config_terms, Terms}, _From, State) ->
    Ret = (catch insert_config(Terms)),
    {reply, Ret, State};

handle_call(Request, _From, State) ->
    Reply = {unknown_request, Request},
    {reply, Reply, State}.

%%--------------------------------------------------------------------
%% Function: handle_cast/2
%% Description: Handling cast messages
%% Returns: {noreply, State}          |
%%          {noreply, State, Timeout} |
%%          {stop, Reason, State}            (terminate/2 is called)
%%--------------------------------------------------------------------

handle_cast(_Msg, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% Function: handle_info/2
%% Description: Handling all non call/cast messages
%% Returns: {noreply, State}          |
%%          {noreply, State, Timeout} |
%%          {stop, Reason, State}            (terminate/2 is called)
%%--------------------------------------------------------------------
handle_info(all_trace_off, State) ->
    Mspec = [{{ibrowse_conf,{trace,'$1','$2'},true},[],[{{'$1','$2'}}]}],
    Trace_on_dests = ets:select(ibrowse_conf, Mspec),
    Fun = fun(#lb_pid{host_port = {H, P}, pid = Pid}, _) ->
                  case lists:member({H, P}, Trace_on_dests) of
                      false ->
                          ok;
                      true ->
                          catch Pid ! {trace, false}
                  end;
             (_, Acc) ->
                  Acc
          end,
    ets:foldl(Fun, undefined, ibrowse_lb),
    ets:select_delete(ibrowse_conf, [{{ibrowse_conf,{trace,'$1','$2'},true},[],['true']}]),
    {noreply, State};
                                  
handle_info({trace, Bool}, State) ->
    put(my_trace_flag, Bool),
    {noreply, State};

handle_info({trace, Bool, Host, Port}, State) ->
    Fun = fun(#lb_pid{host_port = {H, P}, pid = Pid}, _)
             when H == Host,
                  P == Port ->
                  catch Pid ! {trace, Bool};
             (_, Acc) ->
                  Acc
          end,
    ets:foldl(Fun, undefined, ibrowse_lb),
    ets:insert(ibrowse_conf, #ibrowse_conf{key = {trace, Host, Port},
                                           value = Bool}),
    {noreply, State};
                     
handle_info(_Info, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% Function: terminate/2
%% Description: Shutdown the server
%% Returns: any (ignored by gen_server)
%%--------------------------------------------------------------------
terminate(_Reason, _State) ->
    ok.

%%--------------------------------------------------------------------
%% Func: code_change/3
%% Purpose: Convert process state when code is changed
%% Returns: {ok, NewState}
%%--------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
do_get_connection(#url{host = Host, port = Port}, []) ->
    {ok, Pid} = ibrowse_lb:start_link([Host, Port]),
    ets:insert(ibrowse_lb, #lb_pid{host_port = {Host, Port}, pid = Pid}),
    Pid;
do_get_connection(_Url, [#lb_pid{pid = Pid}]) ->
    Pid.