   2016 - 2022   <  >

%%% 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.

%% @doc Create a subprocess and run a sequence of operations.
%%
%% The `prx_task' module provides functions for creating a new process
%% from a `prx:task/0', running a series of operations on the subprocess
%% and cleaning up on error.  The new task is returned to the caller.
-module(prx_task).

-export([
    do/3, do/4,
    with/3
]).

-type op() ::
    {atom(), list()}
    | {module(), atom(), list()}
    | {module(), atom(), list(), [option()]}.

-type option() ::
    state
    | errexit
    | {state, boolean()}
    | {errexit, boolean()}
    | {transform, fun((any()) -> ok | {ok, State :: any()} | {error, prx:posix()})}.
%% Options to modify the behavior of an operation:
%%
  * ` state ' : pass ` ok ' result as the first parameter to the next
%%    operation (default: false)
%%
%% * `errexit': abort operations on error (default: true)
%%
%% * `transform': abort operations on error (default: true)

-type config() ::
    {init, fun((prx:task()) -> {ok, prx:task()} | {error, prx:posix()})}
    | {terminate, fun((prx:task(), prx:task()) -> any())}.

-export_type([
    op/0,
    option/0,
    config/0
]).

%% @doc Fork and configure a subprocess
%%
%% Returns a new process created using `prx:fork/0' after performing
%% the list of operations on the subprocess.
%%
%% If an operation returns an error, the process is terminated using
  SIGKILL .
-spec do(prx:task(), [op() | [op()]], any()) -> {ok, prx:task()} | {error, prx:posix()}.
do(Parent, Ops, State) ->
    do(Parent, Ops, State, []).

%% @doc Fork and configure a subprocess
%%
%% Returns a new process created using the `init' function provided in the
%% `Config' argument list after the process has run the list of
%% operations.
%%
%% If an operation fails, the subprocess is terminated using the
%% `terminate' function.
%%
%% If `init' or `terminate' functions are not provided, the default
%% functions are used.
%%
%% @see with/3
-spec do(prx:task(), [op() | [op()]], any(), [config()]) -> {ok, prx:task()} | {error, prx:posix()}.
do(Parent, Ops, State, Config) ->
    Init = proplists:get_value(init, Config, fun prx:fork/1),
    Terminate = proplists:get_value(terminate, Config, fun terminate/2),
    init(Parent, Init, Terminate, Ops, State).

% terminate/2 will raise an exception if the parent/child are linked to
  different erlang processes and the callback attempts to make a call into
% the parent.
%
% Since the return value is unused, exceptions are the only way to
% communicate failure to the caller. The caller can catch exceptions
% to ignore.
terminate(Parent, Task) ->
    prx:stop(Task),
    case prx:pidof(Task) of
        noproc ->
            ok;
        OSPid ->
            catch prx:kill(Parent, OSPid, sigkill),
            ok
    end.

init(Parent, Init, Terminate, Ops, State) ->
    case Init(Parent) of
        {ok, Task} ->
            run(Parent, Task, Terminate, Ops, State);
        Error ->
            Error
    end.

run(Parent, Task, Terminate, Ops, State) ->
    case with(Task, Ops, State) of
        ok ->
            {ok, Task};
        Error ->
            Terminate(Parent, Task),
            Error
    end.

%% @doc Run a sequence of operations on a task
%%
%% The `with' function runs a sequence of operations on a task. Operations
%% are tuples or list of tuples:
%%
%% * module name: optional if modifier not used, defaults to `prx'
%%
%% * module function
%%
%% * function arguments
%%
%% * modifier options (see `prx_task:option/0')
%%
%% ```
%% Setuid = true,
%% [
   % equivalent to prx :  " )
     , [ " / " ] } ,
%%
   % equivalent to prx :  ( ) , error is ignored
   { prx ,  , [ ] , [ { errexit , false } ] } ,
%%
%%  % the op list can contain op lists
%%  [
       case  of
%%          true ->
%%              [
                   { setresgid , [ 65534 , 65534 , 65534 ] } ,
                     , [ 65534 , 65534 , 65534 ] }
%%              ];
%%          false ->
%%              []
%%      end
%%  ]
%% ]
%% '''
%%
  The called function must return one of :
%%
%% * `ok'
%%
%% * `{ok, any()}'
%%
%% * `{error, any()}'
%%
%% Any other value will return a `badop' exception containing the failing
%% module, function and argument list.
%%
  If the op returns an ` ok ' tuple , the second element can optionally
%% be passed as state to the next operation. The initial state can be
%% set using the `State' argument to `with/3'.
%%
%% == Examples ==
%%
%% The example demonstrates limiting the number of file descriptors by
  passing the highest opened file descriptor to ` setrlimit/3 ' .
%%
%% ```
%% -module(setlimit).
%%
  -export([insn/0 ] ) .
%% -export([close/2, setrlimit/2]).
%%
%% insn() ->
%%     [
%%         setlimit()
%%     ].
%%
%% setlimit() ->
%%     [
%%         {open, ["/", [o_rdonly]]},
%%         {?MODULE, close, [], [state]},
%%         {?MODULE, setrlimit, [], [state]}
%%     ].
%%
%% close(FD, Task) ->
      prx : close(Task , FD ) .
%%
%% setrlimit(FD, Task) ->
      prx : setrlimit(Task , rlimit_nofile , # { cur = > FD , max = > FD } ) .
%% '''
%%
%% Calling the module:
%%
%% ```
  1 > { ok , Task } = prx : fork ( ) .
%% {ok,<0.186.0>}
  2 > { ok , Task1 } = prx : task(Task , setlimit :  ( ) , [ ] ) .
%% {ok,<0.191.0>}
  3 > prx : execvp(Task1 , [ " sh " , " -c " , " ulimit -n " ] ) .
%% ok
  4 > flush ( ) .
  Shell got { stdout,<0.191.0>,<<"7\n " > > }
  Shell got { exit_status,<0.191.0>,0 }
%% ok
%% '''
-spec with(prx:task(), Ops :: [op() | [op()]], State :: any()) ->
    ok
    | {error, any()}.
with(_Task, [], _State) ->
    ok;
with(Task, [Op | Ops], State) when is_list(Op) ->
    case with(Task, Op, State) of
        ok ->
            with(Task, Ops, State);
        Error ->
            Error
    end;
with(Task, [{Fun, Arg} | Ops], State) ->
    op(Task, prx, Fun, [Task | Arg], [], Ops, State);
with(Task, [{Fun, Arg, Options} | Ops], State) when is_atom(Fun), is_list(Arg), is_list(Options) ->
    with(Task, [{prx, Fun, Arg, Options} | Ops], State);
with(Task, [{Mod, Fun, Arg} | Ops], State) when is_atom(Mod), is_atom(Fun) ->
    op(Task, Mod, Fun, [Task | Arg], [], Ops, State);
with(Task, [{Mod, Fun, Arg0, Options} | Ops], State) ->
    ArgvWithState = proplists:get_value(state, Options, false),
    Arg =
        case ArgvWithState of
            true -> [State, Task | Arg0];
            false -> [Task | Arg0]
        end,
    op(Task, Mod, Fun, Arg, Options, Ops, State).

op(Task, Mod, Fun, Arg, Options, Ops, State) ->
    Exit = proplists:get_value(errexit, Options, true),
    Transform = proplists:get_value(transform, Options, fun(N) -> N end),
    try Transform(erlang:apply(Mod, Fun, Arg)) of
        ok ->
            with(Task, Ops, State);
        {ok, NewState} ->
            with(Task, Ops, NewState);
        Branch when is_list(Branch) ->
            with(Task, Branch ++ Ops, State);
        {error, _} when Exit =:= false ->
            with(Task, Ops, State);
        {error, _} = Error ->
            Error;
        Unmatched ->
            error({badop, {Mod, Fun, Arg}, Ops, {reason, Unmatched}})
    catch
        M:N ->
            error({badop, {Mod, Fun, Arg}, Ops, {reason, M, N}})
    end.

 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.

 WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 @doc Create a subprocess and run a sequence of operations.

 The `prx_task' module provides functions for creating a new process
 from a `prx:task/0', running a series of operations on the subprocess
 and cleaning up on error.  The new task is returned to the caller.
 Options to modify the behavior of an operation:

    operation (default: false)

 * `errexit': abort operations on error (default: true)

 * `transform': abort operations on error (default: true)
 @doc Fork and configure a subprocess

 Returns a new process created using `prx:fork/0' after performing
 the list of operations on the subprocess.

 If an operation returns an error, the process is terminated using
 @doc Fork and configure a subprocess

 Returns a new process created using the `init' function provided in the
 `Config' argument list after the process has run the list of
 operations.

 If an operation fails, the subprocess is terminated using the
 `terminate' function.

 If `init' or `terminate' functions are not provided, the default
 functions are used.

 @see with/3
 terminate/2 will raise an exception if the parent/child are linked to
 the parent.

 Since the return value is unused, exceptions are the only way to
 communicate failure to the caller. The caller can catch exceptions
 to ignore.
 @doc Run a sequence of operations on a task

 The `with' function runs a sequence of operations on a task. Operations
 are tuples or list of tuples:

 * module name: optional if modifier not used, defaults to `prx'

 * module function

 * function arguments

 * modifier options (see `prx_task:option/0')

 ```
 Setuid = true,
 [
 equivalent to prx :  " )

 equivalent to prx :  ( ) , error is ignored

  % the op list can contain op lists
  [
          true ->
              [
              ];
          false ->
              []
      end
  ]
 ]
 '''


 * `ok'

 * `{ok, any()}'

 * `{error, any()}'

 Any other value will return a `badop' exception containing the failing
 module, function and argument list.

 be passed as state to the next operation. The initial state can be
 set using the `State' argument to `with/3'.

 == Examples ==

 The example demonstrates limiting the number of file descriptors by

 ```
 -module(setlimit).

 -export([close/2, setrlimit/2]).

 insn() ->
     [
         setlimit()
     ].

 setlimit() ->
     [
         {open, ["/", [o_rdonly]]},
         {?MODULE, close, [], [state]},
         {?MODULE, setrlimit, [], [state]}
     ].

 close(FD, Task) ->

 setrlimit(FD, Task) ->
 '''

 Calling the module:

 ```
 {ok,<0.186.0>}
 {ok,<0.191.0>}
 ok
 ok
 '''
   2016 - 2022   <  >

  THE SOFTWARE IS PROVIDED " AS IS " AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  ANY SPECIAL , DIRECT , INDIRECT , OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE , DATA OR PROFITS , WHETHER IN AN

-module(prx_task).

-export([
    do/3, do/4,
    with/3
]).

-type op() ::
    {atom(), list()}
    | {module(), atom(), list()}
    | {module(), atom(), list(), [option()]}.

-type option() ::
    state
    | errexit
    | {state, boolean()}
    | {errexit, boolean()}
    | {transform, fun((any()) -> ok | {ok, State :: any()} | {error, prx:posix()})}.
  * ` state ' : pass ` ok ' result as the first parameter to the next

-type config() ::
    {init, fun((prx:task()) -> {ok, prx:task()} | {error, prx:posix()})}
    | {terminate, fun((prx:task(), prx:task()) -> any())}.

-export_type([
    op/0,
    option/0,
    config/0
]).

  SIGKILL .
-spec do(prx:task(), [op() | [op()]], any()) -> {ok, prx:task()} | {error, prx:posix()}.
do(Parent, Ops, State) ->
    do(Parent, Ops, State, []).

-spec do(prx:task(), [op() | [op()]], any(), [config()]) -> {ok, prx:task()} | {error, prx:posix()}.
do(Parent, Ops, State, Config) ->
    Init = proplists:get_value(init, Config, fun prx:fork/1),
    Terminate = proplists:get_value(terminate, Config, fun terminate/2),
    init(Parent, Init, Terminate, Ops, State).

  different erlang processes and the callback attempts to make a call into
terminate(Parent, Task) ->
    prx:stop(Task),
    case prx:pidof(Task) of
        noproc ->
            ok;
        OSPid ->
            catch prx:kill(Parent, OSPid, sigkill),
            ok
    end.

init(Parent, Init, Terminate, Ops, State) ->
    case Init(Parent) of
        {ok, Task} ->
            run(Parent, Task, Terminate, Ops, State);
        Error ->
            Error
    end.

run(Parent, Task, Terminate, Ops, State) ->
    case with(Task, Ops, State) of
        ok ->
            {ok, Task};
        Error ->
            Terminate(Parent, Task),
            Error
    end.

     , [ " / " ] } ,
   { prx ,  , [ ] , [ { errexit , false } ] } ,
       case  of
                   { setresgid , [ 65534 , 65534 , 65534 ] } ,
                     , [ 65534 , 65534 , 65534 ] }
  The called function must return one of :
  If the op returns an ` ok ' tuple , the second element can optionally
  passing the highest opened file descriptor to ` setrlimit/3 ' .
  -export([insn/0 ] ) .
      prx : close(Task , FD ) .
      prx : setrlimit(Task , rlimit_nofile , # { cur = > FD , max = > FD } ) .
  1 > { ok , Task } = prx : fork ( ) .
  2 > { ok , Task1 } = prx : task(Task , setlimit :  ( ) , [ ] ) .
  3 > prx : execvp(Task1 , [ " sh " , " -c " , " ulimit -n " ] ) .
  4 > flush ( ) .
  Shell got { stdout,<0.191.0>,<<"7\n " > > }
  Shell got { exit_status,<0.191.0>,0 }
-spec with(prx:task(), Ops :: [op() | [op()]], State :: any()) ->
    ok
    | {error, any()}.
with(_Task, [], _State) ->
    ok;
with(Task, [Op | Ops], State) when is_list(Op) ->
    case with(Task, Op, State) of
        ok ->
            with(Task, Ops, State);
        Error ->
            Error
    end;
with(Task, [{Fun, Arg} | Ops], State) ->
    op(Task, prx, Fun, [Task | Arg], [], Ops, State);
with(Task, [{Fun, Arg, Options} | Ops], State) when is_atom(Fun), is_list(Arg), is_list(Options) ->
    with(Task, [{prx, Fun, Arg, Options} | Ops], State);
with(Task, [{Mod, Fun, Arg} | Ops], State) when is_atom(Mod), is_atom(Fun) ->
    op(Task, Mod, Fun, [Task | Arg], [], Ops, State);
with(Task, [{Mod, Fun, Arg0, Options} | Ops], State) ->
    ArgvWithState = proplists:get_value(state, Options, false),
    Arg =
        case ArgvWithState of
            true -> [State, Task | Arg0];
            false -> [Task | Arg0]
        end,
    op(Task, Mod, Fun, Arg, Options, Ops, State).

op(Task, Mod, Fun, Arg, Options, Ops, State) ->
    Exit = proplists:get_value(errexit, Options, true),
    Transform = proplists:get_value(transform, Options, fun(N) -> N end),
    try Transform(erlang:apply(Mod, Fun, Arg)) of
        ok ->
            with(Task, Ops, State);
        {ok, NewState} ->
            with(Task, Ops, NewState);
        Branch when is_list(Branch) ->
            with(Task, Branch ++ Ops, State);
        {error, _} when Exit =:= false ->
            with(Task, Ops, State);
        {error, _} = Error ->
            Error;
        Unmatched ->
            error({badop, {Mod, Fun, Arg}, Ops, {reason, Unmatched}})
    catch
        M:N ->
            error({badop, {Mod, Fun, Arg}, Ops, {reason, M, N}})
    end.
