%%% Copyright (C) 2009 - Will Glozer.  All rights reserved.
%%% Copyright (C) 2011 - Anton Lebedevich.  All rights reserved.

-module(pgsql_sock).

-behavior(gen_server).

-export([start_link/0,
         close/1,
         get_parameter/2,
         cancel/1]).

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

%% state callbacks
-export([auth/2, initializing/2, on_message/2]).

-include("pgsql.hrl").
-include("pgsql_binary.hrl").

-record(state, {mod,
                sock,
                data = <<>>,
                backend,
                handler,
                queue = queue:new(),
                async,
                parameters = [],
                types = [],
                columns = [],
                rows = [],
                results = [],
                sync_required,
                txstatus}).

%% -- client interface --

start_link() ->
    gen_server:start_link(?MODULE, [], []).

close(C) when is_pid(C) ->
    catch gen_server:cast(C, stop),
    ok.

get_parameter(C, Name) ->
    gen_server:call(C, {get_parameter, to_binary(Name)}, infinity).

cancel(S) ->
    gen_server:cast(S, cancel).

%% -- gen_server implementation --

init([]) ->
    {ok, #state{}}.

handle_call({get_parameter, Name}, _From, State) ->
    case lists:keysearch(Name, 1, State#state.parameters) of
        {value, {Name, Value}} -> Value;
        false                  -> Value = undefined
    end,
    {reply, {ok, Value}, State};

handle_call(Command, From, State) ->
    #state{queue = Q} = State,
    Req = {{call, From}, Command},
    command(Command, State#state{queue = queue:in(Req, Q)}).

handle_cast({{Method, From, Ref}, Command} = Req, State)
  when ((Method == cast) or (Method == incremental)),
       is_pid(From),
       is_reference(Ref)  ->
    #state{queue = Q} = State,
    command(Command, State#state{queue = queue:in(Req, Q)});

handle_cast(stop, State) ->
    {stop, normal, flush_queue(State, {error, closed})};

handle_cast(cancel, State = #state{backend = {Pid, Key}}) ->
    {ok, {Addr, Port}} = inet:peername(State#state.sock),
    SockOpts = [{active, false}, {packet, raw}, binary],
    %% TODO timeout
    {ok, Sock} = gen_tcp:connect(Addr, Port, SockOpts),
    Msg = <<16:?int32, 80877102:?int32, Pid:?int32, Key:?int32>>,
    ok = gen_tcp:send(Sock, Msg),
    gen_tcp:close(Sock),
    {noreply, State}.

handle_info({Closed, Sock}, #state{sock = Sock} = State)
  when Closed == tcp_closed; Closed == ssl_closed ->
    {stop, sock_closed, flush_queue(State, {error, sock_closed})};

handle_info({Error, Sock, Reason}, #state{sock = Sock} = State)
  when Error == tcp_error; Error == ssl_error ->
    Why = {sock_error, Reason},
    {stop, Why, flush_queue(State, {error, Why})};

handle_info({inet_reply, _, ok}, State) ->
    {noreply, State};

handle_info({inet_reply, _, Status}, State) ->
    {stop, Status, flush_queue(State, {error, Status})};

handle_info({_, Sock, Data2}, #state{data = Data, sock = Sock} = State) ->
    loop(State#state{data = <<Data/binary, Data2/binary>>}).

terminate(_Reason, _State) ->
    %% TODO send termination msg, close socket ??
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%% -- internal functions --

command(Command, State = #state{sync_required = true})
  when Command /= sync ->
    {noreply, finish(State, {error, sync_required})};

command({connect, Host, Username, Password, Opts}, State) ->
    Timeout = proplists:get_value(timeout, Opts, 5000),
    Port = proplists:get_value(port, Opts, 5432),
    SockOpts = [{active, false}, {packet, raw}, binary, {nodelay, true}],
    {ok, Sock} = gen_tcp:connect(Host, Port, SockOpts, Timeout),

    State2 = case proplists:get_value(ssl, Opts) of
                 T when T == true; T == required ->
                     start_ssl(Sock, T, Opts, State);
                 _ ->
                     State#state{mod  = gen_tcp, sock = Sock}
             end,

    Opts2 = ["user", 0, Username, 0],
    case proplists:get_value(database, Opts, undefined) of
        undefined -> Opts3 = Opts2;
        Database  -> Opts3 = [Opts2 | ["database", 0, Database, 0]]
    end,
    send(State2, [<<196608:?int32>>, Opts3, 0]),
    Async   = proplists:get_value(async, Opts, undefined),
    setopts(State2, [{active, true}]),
    put(username, Username),
    put(password, Password),
    {noreply,
     State2#state{handler = auth,
                  async = Async}};

command({squery, Sql}, State) ->
    send(State, $Q, [Sql, 0]),
    {noreply, State};

%% TODO add fast_equery command that doesn't need parsed statement,
%% uses default (text) column format,
%% sends Describe after Bind to get RowDescription
command({equery, Statement, Parameters}, State) ->
    #statement{name = StatementName, columns = Columns} = Statement,
    Bin1 = pgsql_wire:encode_parameters(Parameters),
    Bin2 = pgsql_wire:encode_formats(Columns),
    send(State, $B, ["", 0, StatementName, 0, Bin1, Bin2]),
    send(State, $E, ["", 0, <<0:?int32>>]),
    send(State, $C, [$S, "", 0]),
    send(State, $S, []),
    {noreply, State};

command({parse, Name, Sql, Types}, State) ->
    Bin = pgsql_wire:encode_types(Types),
    send(State, $P, [Name, 0, Sql, 0, Bin]),
    send(State, $D, [$S, Name, 0]),
    send(State, $H, []),
    {noreply, State};

command({bind, Statement, PortalName, Parameters}, State) ->
    #statement{name = StatementName, columns = Columns, types = Types} = Statement,
    Typed_Parameters = lists:zip(Types, Parameters),
    Bin1 = pgsql_wire:encode_parameters(Typed_Parameters),
    Bin2 = pgsql_wire:encode_formats(Columns),
    send(State, $B, [PortalName, 0, StatementName, 0, Bin1, Bin2]),
    send(State, $H, []),
    {noreply, State};

command({execute, _Statement, PortalName, MaxRows}, State) ->
    send(State, $E, [PortalName, 0, <<MaxRows:?int32>>]),
    send(State, $H, []),
    {noreply, State};

command({describe_statement, Name}, State) ->
    send(State, $D, [$S, Name, 0]),
    send(State, $H, []),
    {noreply, State};

command({describe_portal, Name}, State) ->
    send(State, $D, [$P, Name, 0]),
    send(State, $H, []),
    {noreply, State};

command({close, Type, Name}, State) ->
    case Type of
        statement -> Type2 = $S;
        portal    -> Type2 = $P
    end,
    send(State, $C, [Type2, Name, 0]),
    send(State, $H, []),
    {noreply, State};

command(sync, State) ->
    send(State, $S, []),
    {noreply, State#state{sync_required = false}}.

start_ssl(S, Flag, Opts, State) ->
    ok = gen_tcp:send(S, <<8:?int32, 80877103:?int32>>),
    Timeout = proplists:get_value(timeout, Opts, 5000),
    {ok, <<Code>>} = gen_tcp:recv(S, 1, Timeout),
    case Code of
        $S  ->
            case ssl:connect(S, Opts, Timeout) of
                {ok, S2}        -> State#state{mod = ssl, sock = S2};
                {error, Reason} -> exit({ssl_negotiation_failed, Reason})
            end;
        $N ->
            case Flag of
                true     -> State;
                required -> exit(ssl_not_available)
            end
    end.

setopts(#state{mod = Mod, sock = Sock}, Opts) ->
    case Mod of
        gen_tcp -> inet:setopts(Sock, Opts);
        ssl     -> ssl:setopts(Sock, Opts)
    end.

send(#state{mod = Mod, sock = Sock}, Data) ->
    do_send(Mod, Sock, pgsql_wire:encode(Data)).

send(#state{mod = Mod, sock = Sock}, Type, Data) ->
    do_send(Mod, Sock, pgsql_wire:encode(Type, Data)).

do_send(gen_tcp, Sock, Bin) ->
    try erlang:port_command(Sock, Bin) of
        true ->
            ok
    catch
        error:_Error ->
            {error,einval}
    end;

do_send(Mod, Sock, Bin) ->
    Mod:send(Sock, Bin).

loop(#state{data = Data, handler = Handler} = State) ->
    case pgsql_wire:decode_message(Data) of
        {Message, Tail} ->
            case ?MODULE:Handler(Message, State#state{data = Tail}) of
                {noreply, State2} ->
                    loop(State2);
                R = {stop, _Reason2, _State2} ->
                    R
            end;
        _ ->
            {noreply, State}
    end.

finish(State, Result) ->
    finish(State, Result, Result).

finish(State = #state{queue = Q}, Notice, Result) ->
    case queue:get(Q) of
        {{cast, From, Ref}, _} ->
            From ! {self(), Ref, Result};
        {{incremental, From, Ref}, _} ->
            From ! {self(), Ref, Notice};
        {{call, From}, _} ->
            gen_server:reply(From, Result)
    end,
    State#state{queue = queue:drop(Q),
                types = [],
                columns = [],
                rows = [],
                results = []}.

add_result(State = #state{queue = Q, results = Results}, Notice, Result) ->
    Results2 = case queue:get(Q) of
                   {{incremental, From, Ref}, _} ->
                       From ! {self(), Ref, Notice},
                       Results;
                   _ ->
                       [Result | Results]
               end,
    State#state{types = [],
                columns = [],
                rows = [],
                results = Results2}.

add_row(State = #state{queue = Q, rows = Rows}, Data) ->
    Rows2 = case queue:get(Q) of
                {{incremental, From, Ref}, _} ->
                    From ! {self(), Ref, {data, Data}},
                    Rows;
                _ ->
                    [Data | Rows]
            end,
    State#state{rows = Rows2}.

notify(State = #state{queue = Q}, Notice) ->
    case queue:get(Q) of
        {{incremental, From, Ref}, _} ->
            From ! {self(), Ref, Notice};
        _ ->
            ignore
    end,
    State.

notify_async(State = #state{async = Pid}, Msg) ->
    case is_pid(Pid) of
        true  -> Pid ! {pgsql, self(), Msg};
        false -> false
    end,
    State.

command_tag(#state{queue = Q}) ->
    {_, Req} = queue:get(Q),
    if is_tuple(Req) ->
            element(1, Req);
       is_atom(Req) ->
            Req
    end.

get_columns(State) ->
    #state{queue = Q, columns = Columns} = State,
    case queue:get(Q) of
        {_, {equery, #statement{columns = C}, _}} ->
            C;
        {_, {execute, #statement{columns = C}, _, _}} ->
            C;
        {_, {squery, _}} ->
            Columns
    end.

make_statement(State) ->
    #state{queue = Q, types = Types, columns = Columns} = State,
    Name = case queue:get(Q) of
               {_, {parse, N, _, _}} -> N;
               {_, {describe_statement, N}} -> N
           end,
    #statement{name = Name, types = Types, columns = Columns}.

sync_required(#state{queue = Q} = State) ->
    case queue:is_empty(Q) of
        false ->
            case command_tag(State) of
                sync ->
                    State;
                _ ->
                    sync_required(finish(State, {error, sync_required}))
            end;
        true ->
            State#state{sync_required = true}
    end.

flush_queue(#state{queue = Q} = State, Error) ->
    case queue:is_empty(Q) of
        false ->
            flush_queue(finish(State, Error), Error);
        true -> State
    end.

to_binary(B) when is_binary(B) -> B;
to_binary(L) when is_list(L)   -> list_to_binary(L).

hex(Bin) ->
    HChar = fun(N) when N < 10 -> $0 + N;
               (N) when N < 16 -> $W + N
            end,
    <<<<(HChar(H)), (HChar(L))>> || <<H:4, L:4>> <= Bin>>.

%% -- backend message handling --

%% AuthenticationOk
auth({$R, <<0:?int32>>}, State) ->
    {noreply, State#state{handler = initializing}};

%% AuthenticationCleartextPassword
auth({$R, <<3:?int32>>}, State) ->
    send(State, $p, [get(password), 0]),
    {noreply, State};

%% AuthenticationMD5Password
auth({$R, <<5:?int32, Salt:4/binary>>}, State) ->
    Digest1 = hex(erlang:md5([get(password), get(username)])),
    Str = ["md5", hex(erlang:md5([Digest1, Salt])), 0],
    send(State, $p, Str),
    {noreply, State};

auth({$R, <<M:?int32, _/binary>>}, State) ->
    case M of
        2 -> Method = kerberosV5;
        4 -> Method = crypt;
        6 -> Method = scm;
        7 -> Method = gss;
        8 -> Method = sspi;
        _ -> Method = unknown
    end,
    State2 = finish(State, {error, {unsupported_auth_method, Method}}),
    {stop, normal, State2};

%% ErrorResponse
auth({error, E}, State) ->
    case E#error.code of
        <<"28000">> -> Why = invalid_authorization_specification;
        <<"28P01">> -> Why = invalid_password;
        Any         -> Why = Any
    end,
    {stop, normal, finish(State, {error, Why})};

auth(Other, State) ->
    on_message(Other, State).

%% BackendKeyData
initializing({$K, <<Pid:?int32, Key:?int32>>}, State) ->
    {noreply, State#state{backend = {Pid, Key}}};

%% ReadyForQuery
initializing({$Z, <<Status:8>>}, State) ->
    #state{parameters = Parameters} = State,
    erase(username),
    erase(password),
    %% TODO decode dates to now() format
    case lists:keysearch(<<"integer_datetimes">>, 1, Parameters) of
        {value, {_, <<"on">>}}  -> put(datetime_mod, pgsql_idatetime);
        {value, {_, <<"off">>}} -> put(datetime_mod, pgsql_fdatetime)
    end,
    State2 = finish(State#state{handler = on_message,
                               txstatus = Status},
                   connected),
    {noreply, State2};

initializing({error, _} = Error, State) ->
    {stop, normal, finish(State, Error)};

initializing(Other, State) ->
    on_message(Other, State).

%% ParseComplete
on_message({$1, <<>>}, State) ->
    {noreply, State};

%% ParameterDescription
on_message({$t, <<_Count:?int16, Bin/binary>>}, State) ->
    Types = [pgsql_types:oid2type(Oid) || <<Oid:?int32>> <= Bin],
    State2 = notify(State#state{types = Types}, {types, Types}),
    {noreply, State2};

%% RowDescription
on_message({$T, <<Count:?int16, Bin/binary>>}, State) ->
    Columns = pgsql_wire:decode_columns(Count, Bin),
    Columns2 =
        case command_tag(State) of
            C when C == describe_portal; C == squery ->
                Columns;
            C when C == parse; C == describe_statement ->
                [Col#column{format = pgsql_wire:format(Col#column.type)}
                 || Col <- Columns]
        end,
    State2 = State#state{columns = Columns2},
    Message = {columns, Columns2},
    State3 = case command_tag(State2) of
                 squery ->
                     notify(State2, Message);
                 T when T == parse; T == describe_statement ->
                     finish(State2, Message, {ok, make_statement(State2)});
                 describe_portal ->
                     finish(State2, Message, {ok, Columns})
             end,
    {noreply, State3};

%% NoData
on_message({$n, <<>>}, State) ->
    State2 = case command_tag(State) of
                 C when C == parse; C == describe_statement ->
                     finish(State, no_data, {ok, make_statement(State)});
                 describe_portal ->
                     finish(State, no_data, {ok, []})
             end,
    {noreply, State2};

%% BindComplete
on_message({$2, <<>>}, State) ->
    State2 = case command_tag(State) of
                 equery ->
                     %% TODO send Describe as a part of equery, needs text format support
                     notify(State, {columns, get_columns(State)});
                 bind ->
                     finish(State, ok)
             end,
    {noreply, State2};

%% CloseComplete
on_message({$3, <<>>}, State) ->
    State2 = case command_tag(State) of
                 equery ->
                     State;
                 close ->
                     finish(State, ok)
             end,
    {noreply, State2};

%% DataRow
on_message({$D, <<_Count:?int16, Bin/binary>>}, State) ->
    Data = pgsql_wire:decode_data(get_columns(State), Bin),
    {noreply, add_row(State, Data)};

%% PortalSuspended
on_message({$s, <<>>}, State) ->
    State2 = finish(State,
                   suspended,
                   {partial, lists:reverse(State#state.rows)}),
    {noreply, State2};

%% CommandComplete
on_message({$C, Bin}, State) ->
    Complete = pgsql_wire:decode_complete(Bin),
    Command = command_tag(State),
    Notice = {complete, Complete},
    Rows = lists:reverse(State#state.rows),
    State2 = case {Command, Complete, Rows} of
                 {execute, {_, Count}, []} ->
                     finish(State, Notice, {ok, Count});
                 {execute, {_, Count}, _} ->
                     finish(State, Notice, {ok, Count, Rows});
                 {execute, _, _} ->
                     finish(State, Notice, {ok, Rows});
                 {C, {_, Count}, []} when C == squery; C == equery ->
                     add_result(State, Notice, {ok, Count});
                 {C, {_, Count}, _} when C == squery; C == equery ->
                     add_result(State, Notice, {ok, Count, get_columns(State), Rows});
                 {C, _, _} when C == squery; C == equery ->
                     add_result(State, Notice, {ok, get_columns(State), Rows})
             end,
    {noreply, State2};

%% EmptyQueryResponse
on_message({$I, _Bin}, State) ->
    Notice = {complete, empty},
    State2 = case command_tag(State) of
                 execute ->
                     finish(State, Notice, {ok, [], []});
                 C when C == squery; C == equery ->
                     add_result(State, Notice, {ok, [], []})
             end,
    {noreply, State2};

%% ReadyForQuery
on_message({$Z, <<Status:8>>}, State) ->
    State2 = case command_tag(State) of
                 squery ->
                     case State#state.results of
                         [Result] ->
                             finish(State, done, Result);
                         Results ->
                             finish(State, done, lists:reverse(Results))
                     end;
                 equery ->
                     case State#state.results of
                         [Result] ->
                             finish(State, done, Result);
                         [] ->
                             finish(State, done)
                     end;
                 sync ->
                     finish(State, ok)
             end,
    {noreply, State2#state{txstatus = Status}};

on_message(Error = {error, _}, State) ->
    State2 = case command_tag(State) of
                 C when C == squery; C == equery ->
                     add_result(State, Error, Error);
                 _ ->
                     sync_required(finish(State, Error))
             end,
    {noreply, State2};

%% NoticeResponse
on_message({$N, Data}, State) ->
    State2 = notify_async(State, {notice, pgsql_wire:decode_error(Data)}),
    {noreply, State2};

%% ParameterStatus
on_message({$S, Data}, State) ->
    [Name, Value] = pgsql_wire:decode_strings(Data),
    Parameters2 = lists:keystore(Name, 1, State#state.parameters,
                                 {Name, Value}),
    {noreply, State#state{parameters = Parameters2}};

%% NotificationResponse
on_message({$A, <<Pid:?int32, Strings/binary>>}, State) ->
    case pgsql_wire:decode_strings(Strings) of
        [Channel, Payload] -> ok;
        [Channel]          -> Payload = <<>>
    end,
    State2 = notify_async(State, {notification, Channel, Pid, Payload}),
    {noreply, State2}.