(*  Title:      Pure/Concurrent/task_queue.ML

    Author:     Makarius

Ordered queue of grouped tasks.

*)

signature TASK_QUEUE =

sig

  type task

  val new_task: int -> task

  val pri_of_task: task -> int

  val str_of_task: task -> string

  type group

  val group_id: group -> int

  val eq_group: group * group -> bool

  val new_group: unit -> group

  val group_exns: group -> exn list

  val str_of_group: group -> string

  type queue

  val empty: queue

  val is_empty: queue -> bool

  val status: queue -> {ready: int, pending: int, running: int}

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

  val extend: task -> (bool -> bool) -> queue -> queue option

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

  val dequeue_towards: task list -> queue ->

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

  val interrupt: queue -> task -> unit

  val interrupt_external: queue -> string -> unit

  val cancel_group: group -> exn -> unit

  val cancel: queue -> group -> bool

  val cancel_all: queue -> group list

  val finish: task -> queue -> queue

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 = Graph(type key = task val ord = task_ord);

(* groups *)

datatype group = Group of serial * exn list ref;

fun group_id (Group (gid, _)) = gid;

fun eq_group (Group (gid1, _), Group (gid2, _)) = gid1 = gid2;

fun new_group () = Group (serial (), ref []);

fun group_exns (Group (_, ref exns)) = exns;

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

  if null exns then string_of_int i else enclose "(" ")" (string_of_int i);

(* jobs *)

datatype job =

  Job of (bool -> bool) list |

  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 set_job task job (jobs: jobs) = Task_Graph.map_node task (fn (group, _) => (group, job)) jobs;

fun add_job task dep (jobs: jobs) =

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

(* queue of grouped jobs *)

datatype result = Unknown | Result of task | No_Result;

datatype queue = Queue of

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

  jobs: jobs,                       (*job dependency graph*)

  cache: result};                   (*last dequeue result*)

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

val empty = make_queue Inttab.empty Task_Graph.empty No_Result;

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

(* status *)

fun status (Queue {jobs, ...}) =

  let

    val (x, y, z) =

      Task_Graph.fold (fn (task, ((_, job), (deps, _))) => fn (x, y, z) =>

          (case job of

            Job _ => if null deps then (x + 1, y, z) else (x, y + 1, z)

          | Running _ => (x, y, z + 1)))

        jobs (0, 0, 0);

  in {ready = x, pending = y, running = z} end;

(* enqueue *)

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

  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;

    val cache' =

      (case cache of

        Result last =>

          if task_ord (last, task) = LESS

          then cache else Unknown

      | _ => Unknown);

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

fun extend task job (Queue {groups, jobs, cache}) =

  (case try (get_job jobs) task of

    SOME (Job list) => SOME (make_queue groups (set_job task (Job (job :: list)) jobs) cache)

  | _ => NONE);

(* dequeue *)

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

  let

    fun ready (task, ((group, Job list), ([], _))) = SOME (task, group, rev list)

      | ready _ = NONE;

    fun deq boundary =

      (case Task_Graph.get_first boundary ready jobs of

        NONE => (NONE, make_queue groups jobs No_Result)

      | SOME (result as (task, _, _)) =>

          let

            val jobs' = set_job task (Running (Thread.self ())) jobs;

            val cache' = Result task;

          in (SOME result, make_queue groups jobs' cache') end);

  in

    (case cache of

      Unknown => deq NONE

    | Result last => deq (SOME last)

    | No_Result => (NONE, queue))

  end;

(* dequeue_towards -- adhoc dependencies *)

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

  let

    fun ready task =

      (case Task_Graph.get_node jobs task of

        (group, Job list) =>

          if null (Task_Graph.imm_preds jobs task) then SOME (task, group, rev list)

          else NONE

      | _ => NONE);

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

    fun result (res as (task, _, _)) =

      let

        val jobs' = set_job task (Running (Thread.self ())) jobs;

        val cache' = Unknown;

      in (SOME (res, tasks), make_queue groups jobs' cache') end;

  in

    (case get_first ready tasks of

      SOME res => result res

    | NONE =>

        (case get_first ready (Task_Graph.all_preds jobs tasks) of

          SOME res => result res

        | NONE => (NONE, queue)))

  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 NONE

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

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

  | NONE => ());

(* termination *)

fun cancel_group (Group (_, r)) exn = CRITICAL (fn () =>

  (case exn of

    Exn.Interrupt => if null (! r) then r := [exn] else ()

  | _ => change r (cons exn)));

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

  let

    val _ = cancel_group group Exn.Interrupt;

    val tasks = Inttab.lookup_list groups gid;

    val running = fold (get_job jobs #> (fn Running t => insert Thread.equal t | _ => I)) tasks [];

    val _ = List.app SimpleThread.interrupt running;

  in null running end;

fun cancel_all (Queue {jobs, ...}) =

  let

    fun cancel_job (group, job) (groups, running) =

      (cancel_group group Exn.Interrupt;

        (case job of Running t => (insert eq_group group groups, insert Thread.equal t running)

        | _ => (groups, running)));

    val (groups, running) = Task_Graph.fold (cancel_job o #1 o #2) jobs ([], []);

    val _ = List.app SimpleThread.interrupt running;

  in groups end;

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

  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;

    val cache' =

      if null (Task_Graph.imm_succs jobs task) then cache

      else Unknown;

  in make_queue groups' jobs' cache' end;

end;