/* 

  Task scheduling in Picat.

  Port of Markus Triska's Prolog code: https://github.com/triska/clpz/blob/master/tasks.pl
  """
  Task scheduling example.
  Written May 2016 by Markus Triska (triska@metalevel.at)
  Public domain code.

  The cumulative/2 constraint is used to express non-overlapping
  tasks with a resource consumption limit. The min/1 labeling option
  is used to find schedules that minimize the total duration.
  """

  Note: Picat don't have cumulative/2 so it must be converted to Picat's cumulative/4.

  Picat> tasks(Tasks, Starts, End), labeling($[min(End)], Starts)
  Tasks = [task(0,3,3,1,1),task(0,4,4,1,2),task(4,2,6,1,3),task(3,3,6,1,4)]
  Starts = [0,0,4,3]
  End = 6 ?;
  no

  This model was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/


import v3_utils.
import cp.


main => go.


go ?=>
  tasks(Tasks, Starts, End),
  labeling($[ff,split,min(End)], Starts),
  % solve($[ff,split], Starts),  
  println(starts=Starts),
  println(end=End),
  println(tasks=Tasks),
  
  nl.

go => true.


% Aliases
label(Vs) :- solve(Vs).
labeling(Opt,Vs) :- solve(Opt,Vs).

/*
  Convert SWI-Prolog's cumulative/2 to Picat's cumulative/4.

  From SWI-Prolog's help(cumulative).
  """
  cumulative(+Tasks, +Options)
    Schedule with a limited resource. Tasks is a list of tasks, each of the form  
      task(S_i, D_i, E_i, C_i, T_i). 
    - S_i denotes the start time, 
    - D_i the positive duration, 
    - E_i the end time, 
    - C_i the non-negative resource consumption, and 
    - T_i the task identifier. 
    Each of  these arguments must be a finite domain variable with bounded domain,  or an  integer. 
    The  constraint holds iff at each time slot during the start and end of each task, 
    the total  resource consumption of all tasks running at that time does not exceed the  
    global resource  limit. 

    Options  is a list of options. Currently, the only supported option is:
    - limit(L)
        The integer L is the global resource limit. Default is 1.
   """
*/
cumulative(Tasks,LimitL) :-
  % Add the task id
  foreach(I in 1..Tasks.len)
     $task(_,_,_,_,I) = Tasks[I]
  end,
  Start    = [T[1] : T in Tasks],
  Duration = [T[2] : T in Tasks],
  % Picat's cumulative/4 don't include EndTime
  % but we have to give it a proper domain since
  % it's included in task/5.
  foreach(T in Tasks)
     T[3] #= T[1] + T[2]
  end,
  EndTime = [T[3] : T in Tasks],  
  EndTime :: 0..fd_max(Start[1])+ max(Duration),
  Resource = [T[4] : T in Tasks],
  LimitL = $[limit(Limit)],
  cumulative(Start,Duration,Resource,Limit).
  

%
% From https://github.com/triska/clpz/blob/master/tasks.pl
%

tasks(Tasks, Starts, End) :-
        Tasks = $[task(_,3,_,1,_),
                  task(_,4,_,1,_),
                  task(_,2,_,1,_),
                  task(_,3,_,1,_)],
        maplist($task_start, Tasks, Starts), % hakank
        Starts :: 0..100, % hakank
        cumulative(Tasks, $[limit(2)]), % hakank
        foldl(max_end, Tasks, 0, End).

task_start(task(Start,_,_,_,_), Start).

max_end(task(_,_,End,_,_), E0, E) :-
        E #= max(E0, End).

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   foldl/4
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

foldl(Goal_3, Ls, A0, A) :-
        foldl_(Ls, Goal_3, A0, A).

foldl_([], _, A, A).
foldl_([L|Ls], G_3, A0, A) :-
        call(G_3, L, A0, A1),
        foldl_(Ls, G_3, A1, A).

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   ?- tasks(Tasks, Starts, End), labeling([min(End)], Starts).
   %@ Tasks = [task(0, 3, 3, 1, _G32), task(0, 4, 4, 1, _G41), task(4, 2, 6, 1, _G50), task(3, 3, 6, 1, _G59)],
   %@ Starts = [0, 0, 4, 3],
   %@ End = 6 .
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */