(*  Title:      Pure/Concurrent/task_queue.ML

    Author:     Makarius

Ordered queue of grouped tasks.

*)

signature TASK_QUEUE =

sig

  eqtype task

  val new_task: int -> task

  val pri_of_task: task -> int

  val str_of_task: task -> string

  eqtype group

  val new_group: unit -> group

  val invalidate_group: group -> unit

  val str_of_group: group -> string

  type queue

  val empty: queue

  val is_empty: queue -> bool

  val enqueue: group -> task list -> int -> (bool -> bool) -> queue -> task * queue

  val depend: task list -> task -> queue -> queue

  val dequeue: queue -> (task * group * (unit -> bool)) option * queue

  val dequeue_towards: task list -> queue ->

    (((task * group * (unit -> bool)) * task list) option * queue)

  val interrupt: queue -> task -> unit

  val interrupt_external: queue -> string -> unit

  val finish: task -> queue -> queue

  val cancel: queue -> group -> bool

end;

structure Task_Queue: TASK_QUEUE =

struct

(* tasks *)

datatype task = Task of int * serial;

fun new_task pri = Task (pri, serial ());

fun pri_of_task (Task (pri, _)) = pri;

fun str_of_task (Task (_, i)) = string_of_int i;

fun task_ord (Task t1, Task t2) = prod_ord (rev_order o int_ord) int_ord (t1, t2);

structure Task_Graph = GraphFun(type key = task val ord = task_ord);

(* groups *)

datatype group = Group of serial * bool ref;

fun new_group () = Group (serial (), ref true);

fun invalidate_group (Group (_, ok)) = ok := false;

fun str_of_group (Group (i, ref ok)) =

  if ok then string_of_int i else enclose "(" ")" (string_of_int i);

(* jobs *)

datatype job =

  Job of bool -> bool |

  Running of Thread.thread;

type jobs = (group * job) Task_Graph.T;

fun get_group (jobs: jobs) task = #1 (Task_Graph.get_node jobs task);

fun get_job (jobs: jobs) task = #2 (Task_Graph.get_node jobs task);

fun map_job task f (jobs: jobs) = Task_Graph.map_node task (apsnd f) jobs;

fun add_job task dep (jobs: jobs) =

  Task_Graph.add_edge (dep, task) jobs handle Task_Graph.UNDEF _ => jobs;

fun add_job_acyclic task dep (jobs: jobs) =

  Task_Graph.add_edge_acyclic (dep, task) jobs handle Task_Graph.UNDEF _ => jobs;

(* queue of grouped jobs *)

datatype queue = Queue of

 {groups: task list Inttab.table,   (*groups with presently active members*)

  jobs: jobs};                      (*job dependency graph*)

fun make_queue groups jobs = Queue {groups = groups, jobs = jobs};

val empty = make_queue Inttab.empty Task_Graph.empty;

fun is_empty (Queue {jobs, ...}) = Task_Graph.is_empty jobs;

(* enqueue *)

fun enqueue (group as Group (gid, _)) deps pri job (Queue {groups, jobs}) =

  let

    val task = new_task pri;

    val groups' = Inttab.cons_list (gid, task) groups;

    val jobs' = jobs

      |> Task_Graph.new_node (task, (group, Job job)) |> fold (add_job task) deps;

  in (task, make_queue groups' jobs') end;

fun depend deps task (Queue {groups, jobs}) =

  make_queue groups (fold (add_job_acyclic task) deps jobs);

(* dequeue *)

local

fun dequeue_result NONE queue = (NONE, queue)

  | dequeue_result (SOME (result as (task, _, _))) (Queue {groups, jobs}) =

      (SOME result, make_queue groups (map_job task (K (Running (Thread.self ()))) jobs));

in

fun dequeue (queue as Queue {jobs, ...}) =

  let

    fun ready (task, ((group as Group (_, ref ok), Job job), ([], _))) =

          SOME (task, group, (fn () => job ok))

      | ready _ = NONE;

  in dequeue_result (Task_Graph.get_first ready jobs) queue end;

fun dequeue_towards tasks (queue as Queue {jobs, ...}) =

  let

    val tasks' = filter (can (Task_Graph.get_node jobs)) tasks;

    fun ready task =

      (case Task_Graph.get_node jobs task of

        (group as Group (_, ref ok), Job job) =>

          if null (Task_Graph.imm_preds jobs task) then SOME (task, group, (fn () => job ok))

          else NONE

      | _ => NONE);

  in

    (case dequeue_result (get_first ready (Task_Graph.all_preds jobs tasks')) queue of

      (NONE, queue') => (NONE, queue')

    | (SOME work, queue') => (SOME (work, tasks'), queue'))

  end;

end;

(* sporadic interrupts *)

fun interrupt (Queue {jobs, ...}) task =

  (case try (get_job jobs) task of SOME (Running thread) => SimpleThread.interrupt thread | _ => ());

fun interrupt_external (queue as Queue {jobs, ...}) str =

  (case Int.fromString str of

    SOME i =>

      (case Task_Graph.get_first

          (fn (task as Task (_, j), _) => if i = j then SOME task else NONE) jobs

        of SOME task => interrupt queue task | NONE => ())

  | NONE => ());

(* misc operations *)

fun cancel (Queue {groups, jobs, ...}) (group as Group (gid, _)) =

  let

    val _ = invalidate_group group;

    val tasks = Inttab.lookup_list groups gid;

    val running = fold (get_job jobs #> (fn Running thread => cons thread | _ => I)) tasks [];

    val _ = List.app SimpleThread.interrupt running;

  in null running end;

fun finish task (Queue {groups, jobs}) =

  let

    val Group (gid, _) = get_group jobs task;

    val groups' = Inttab.remove_list (op =) (gid, task) groups;

    val jobs' = Task_Graph.del_node task jobs;

  in make_queue groups' jobs' end;

end;