(*  Title:      Pure/Concurrent/task_queue.ML

    Author:     Makarius

Ordered queue of grouped tasks.

*)

signature TASK_QUEUE =

sig

  type group

  val new_group: group option -> group

  val group_id: group -> int

  val eq_group: group * group -> bool

  val cancel_group: group -> exn -> unit

  val is_canceled: group -> bool

  val group_status: group -> exn list

  val str_of_group: group -> string

  val str_of_groups: group -> string

  type task

  val dummy_task: unit -> task

  val group_of_task: task -> group

  val name_of_task: task -> string

  val pri_of_task: task -> int

  val str_of_task: task -> string

  val str_of_task_groups: task -> string

  val timing_of_task: task -> Time.time * Time.time * string list

  val running: task -> (unit -> 'a) -> 'a

  val joining: task -> (unit -> 'a) -> 'a

  val waiting: task -> task list -> (unit -> 'a) -> 'a

  type queue

  val empty: queue

  val known_task: queue -> task -> bool

  val all_passive: queue -> bool

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

  val cancel: queue -> group -> bool

  val cancel_all: queue -> group list

  val finish: task -> queue -> bool * queue

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

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

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

  val dequeue_passive: Thread.thread -> task -> queue -> bool * queue

  val dequeue: Thread.thread -> queue -> (task * (bool -> bool) list) option * queue

  val dequeue_deps: Thread.thread -> task list -> queue ->

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

end;

structure Task_Queue: TASK_QUEUE =

struct

val new_id = Synchronized.counter ();

(** nested groups of tasks **)

(* groups *)

abstype group = Group of

 {parent: group option,

  id: int,

  status: exn list Synchronized.var}

with

fun make_group (parent, id, status) = Group {parent = parent, id = id, status = status};

fun new_group parent = make_group (parent, new_id (), Synchronized.var "group" []);

fun group_id (Group {id, ...}) = id;

fun eq_group (group1, group2) = group_id group1 = group_id group2;

fun fold_groups f (g as Group {parent = NONE, ...}) a = f g a

  | fold_groups f (g as Group {parent = SOME group, ...}) a = fold_groups f group (f g a);

(* group status *)

fun cancel_group (Group {status, ...}) exn =

  Synchronized.change status

    (fn exns =>

      if not (Exn.is_interrupt exn) orelse null exns then exn :: exns

      else exns);

fun is_canceled (Group {parent, status, ...}) =

  not (null (Synchronized.value status)) orelse

    (case parent of NONE => false | SOME group => is_canceled group);

fun group_status (Group {parent, status, ...}) =

  Synchronized.value status @

    (case parent of NONE => [] | SOME group => group_status group);

fun str_of_group group =

  (is_canceled group ? enclose "(" ")") (string_of_int (group_id group));

fun str_of_groups group =

  space_implode "/" (map str_of_group (rev (fold_groups cons group [])));

end;

(* tasks *)

type timing = Time.time * Time.time * string list;  (*run, wait, wait dependencies*)

fun new_timing () =

  Synchronized.var "timing" ((Time.zeroTime, Time.zeroTime, []): timing);

abstype task = Task of

 {group: group,

  name: string,

  id: int,

  pri: int option,

  timing: timing Synchronized.var}

with

fun dummy_task () =

  Task {group = new_group NONE, name = "", id = 0, pri = NONE, timing = new_timing ()};

fun new_task group name pri =

  Task {group = group, name = name, id = new_id (), pri = pri, timing = new_timing ()};

fun group_of_task (Task {group, ...}) = group;

fun name_of_task (Task {name, ...}) = name;

fun pri_of_task (Task {pri, ...}) = the_default 0 pri;

fun str_of_task (Task {name, id, ...}) =

  if name = "" then string_of_int id else string_of_int id ^ " (" ^ name ^ ")";

fun str_of_task_groups task = str_of_task task ^ " in " ^ str_of_groups (group_of_task task);

fun timing_of_task (Task {timing, ...}) = Synchronized.value timing;

fun update_timing update (Task {timing, ...}) e =

  uninterruptible (fn restore_attributes => fn () =>

    let

      val start = Time.now ();

      val result = Exn.capture (restore_attributes e) ();

      val t = Time.- (Time.now (), start);

      val _ = Synchronized.change timing (update t);

    in Exn.release result end) ();

fun task_ord (Task {id = id1, pri = pri1, ...}, Task {id = id2, pri = pri2, ...}) =

  prod_ord (rev_order o option_ord int_ord) int_ord ((pri1, id1), (pri2, id2));

end;

structure Tasks = Table(type key = task val ord = task_ord);

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

(* timing *)

fun running task =

  update_timing (fn t => fn (a, b, ds) => (Time.+ (a, t), b, ds)) task;

fun joining task =

  update_timing (fn t => fn (a, b, ds) => (Time.- (a, t), b, ds)) task;

fun waiting task deps =

  update_timing (fn t => fn (a, b, ds) =>

    (Time.- (a, t), Time.+ (b, t),

      if ! Multithreading.trace > 0

      then fold (insert (op =) o name_of_task) deps ds else ds)) task;

(** queue of jobs and groups **)

(* known group members *)

type groups = unit Tasks.table Inttab.table;

fun get_tasks (groups: groups) gid =

  the_default Tasks.empty (Inttab.lookup groups gid);

fun add_task (gid, task) groups =

  Inttab.update (gid, Tasks.update (task, ()) (get_tasks groups gid)) groups;

fun del_task (gid, task) groups =

  let val tasks = Tasks.delete_safe task (get_tasks groups gid) in

    if Tasks.is_empty tasks then Inttab.delete_safe gid groups

    else Inttab.update (gid, tasks) groups

  end;

(* job dependency graph *)

datatype job =

  Job of (bool -> bool) list |

  Running of Thread.thread |

  Passive of unit -> bool;

type jobs = job Task_Graph.T;

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

fun set_job task job (jobs: jobs) = Task_Graph.map_node task (K job) jobs;

fun add_job task dep (jobs: jobs) =

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

(* queue *)

datatype queue = Queue of {groups: groups, jobs: jobs};

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

val empty = make_queue Inttab.empty Task_Graph.empty;

fun known_task (Queue {jobs, ...}) task = can (Task_Graph.get_entry jobs) task;

(* job status *)

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

  | ready_job task (Passive abort, ([], _)) =

      if is_canceled (group_of_task task) then SOME (task, [fn _ => abort ()])

      else NONE

  | ready_job _ _ = NONE;

fun active_job (_, (Job _, _)) = SOME ()

  | active_job (_, (Running _, _)) = SOME ()

  | active_job (task, (Passive _, _)) =

      if is_canceled (group_of_task task) then SOME () else NONE;

fun all_passive (Queue {jobs, ...}) = is_none (Task_Graph.get_first active_job jobs);

(* queue status *)

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

  let

    val (x, y, z, w) =

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

          (case job of

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

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

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

        jobs (0, 0, 0, 0);

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

(** task queue operations **)

(* cancel -- peers and sub-groups *)

fun cancel (Queue {groups, jobs}) group =

  let

    val _ = cancel_group group Exn.Interrupt;

    val running =

      Tasks.fold (#1 #> get_job jobs #> (fn Running t => insert Thread.equal t | _ => I))

        (get_tasks groups (group_id group)) [];

    val _ = List.app Simple_Thread.interrupt running;

  in null running end;

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

  let

    fun cancel_job (task, (job, _)) (groups, running) =

      let

        val group = group_of_task task;

        val _ = cancel_group group Exn.Interrupt;

      in

        (case job of

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

        | _ => (groups, running))

      end;

    val (running_groups, running) = Task_Graph.fold cancel_job jobs ([], []);

    val _ = List.app Simple_Thread.interrupt running;

  in running_groups end;

(* finish *)

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

  let

    val group = group_of_task task;

    val groups' = fold_groups (fn g => del_task (group_id g, task)) group groups;

    val jobs' = Task_Graph.del_node task jobs;

    val maximal = null (Task_Graph.imm_succs jobs task);

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

(* enqueue *)

fun enqueue_passive group abort (Queue {groups, jobs}) =

  let

    val task = new_task group "passive" NONE;

    val groups' = fold_groups (fn g => add_task (group_id g, task)) group groups;

    val jobs' = jobs |> Task_Graph.new_node (task, Passive abort);

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

fun enqueue name group deps pri job (Queue {groups, jobs}) =

  let

    val task = new_task group name (SOME pri);

    val groups' = fold_groups (fn g => add_task (group_id g, task)) group groups;

    val jobs' = jobs

      |> Task_Graph.new_node (task, Job [job])

      |> fold (add_job task) deps;

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

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

  (case try (get_job jobs) task of

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

  | _ => NONE);

(* dequeue *)

fun dequeue_passive thread task (queue as Queue {groups, jobs}) =

  (case try (get_job jobs) task of

    SOME (Passive _) =>

      let val jobs' = set_job task (Running thread) jobs

      in (true, make_queue groups jobs') end

  | _ => (false, queue));

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

  (case Task_Graph.get_first (uncurry ready_job) jobs of

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

      let val jobs' = set_job task (Running thread) jobs

      in (SOME result, make_queue groups jobs') end

  | NONE => (NONE, queue));

(* dequeue wrt. dynamic dependencies *)

fun dequeue_deps thread deps (queue as Queue {groups, jobs}) =

  let

    fun ready [] rest = (NONE, rev rest)

      | ready (task :: tasks) rest =

          (case try (Task_Graph.get_entry jobs) task of

            NONE => ready tasks rest

          | SOME (_, entry) =>

              (case ready_job task entry of

                NONE => ready tasks (task :: rest)

              | some => (some, List.revAppend (rest, tasks))));

    fun ready_dep _ [] = NONE

      | ready_dep seen (task :: tasks) =

          if Tasks.defined seen task then ready_dep seen tasks

          else

            let val entry as (_, (ds, _)) = #2 (Task_Graph.get_entry jobs task) in

              (case ready_job task entry of

                NONE => ready_dep (Tasks.update (task, ()) seen) (ds @ tasks)

              | some => some)

            end;

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

      let val jobs' = set_job task (Running thread) jobs

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

  in

    (case ready deps [] of

      (SOME res, deps') => result res deps'

    | (NONE, deps') =>

        (case ready_dep Tasks.empty deps' of

          SOME res => result res deps'

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

  end;

end;