(*  Title:      Pure/Concurrent/task_queue.ML

    Author:     Makarius

Ordered queue of grouped tasks.

*)

signature TASK_QUEUE =

sig

  type task

  val dummy_task: task

  val pri_of_task: task -> int

  val str_of_task: 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 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

  type queue

  val empty: queue

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

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

    queue -> (task * bool) * queue

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

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

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

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

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

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

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

end;

structure Task_Queue: TASK_QUEUE =

struct

val new_id = Synchronized.counter ();

(* timing *)

type timing = Time.time * Time.time * string list;

fun new_timing () =

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

fun gen_timing account timing e =

  let

    val start = Time.now ();

    val result = Exn.capture e ();

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

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

  in Exn.release result end;

(* tasks *)

abstype task = Task of

 {name: string,

  id: int,

  pri: int option,

  timing: timing Synchronized.var}

with

val dummy_task = Task {name = "", id = ~1, pri = NONE, timing = new_timing ()};

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

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

fun running (Task {timing, ...}) =

  gen_timing (fn t => fn (a, b, ds) => (Time.+ (a, t), b, ds)) timing;

fun joining (Task {timing, ...}) =

  gen_timing (fn t => fn (a, b, ds) => (Time.- (a, t), b, ds)) timing;

fun waiting (Task {timing, ...}) deps =

  timing |> gen_timing (fn t => fn (a, b, ds) =>

    (Time.- (a, t), Time.+ (b, t), fold (fn Task {name, ...} => insert (op =) name) deps ds));

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));

val eq_task = is_equal o task_ord;

end;

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

(* nested 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 group_ancestry (Group {parent, id, ...}) =

  id :: (case parent of NONE => [] | SOME group => group_ancestry group);

(* 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));

end;

(* jobs *)

datatype job =

  Job of (bool -> bool) list |

  Running of Thread.thread |

  Passive of unit -> bool;

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;

fun add_dep task dep (jobs: jobs) =

  if Task_Graph.is_edge jobs (task, dep) then

    raise Fail "Cyclic dependency of future tasks"

  else add_job task dep jobs;

fun get_deps (jobs: jobs) task =

  Task_Graph.imm_preds jobs task handle Task_Graph.UNDEF _ => [];

(* 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;

(* job status *)

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

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

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

      else NONE

  | ready_job _ _ = NONE;

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

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

  | active_job (group, Passive _) = if is_canceled group then SOME () else NONE;

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

  is_none (Task_Graph.get_first (active_job o #1 o #2) 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;

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

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

  let

    val _ = cancel_group group Exn.Interrupt;

    val tasks = Inttab.lookup_list groups (group_id group);

    val running =

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

    val _ = List.app Simple_Thread.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 (running_groups, running) = Task_Graph.fold (cancel_job o #1 o #2) jobs ([], []);

    val _ = List.app Simple_Thread.interrupt running;

  in running_groups end;

(* enqueue *)

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

  let

    val task = new_task "passive" NONE;

    val groups' = groups

      |> fold (fn gid => Inttab.cons_list (gid, task)) (group_ancestry group);

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

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

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

  let

    val task = new_task name (SOME pri);

    val groups' = groups

      |> fold (fn gid => Inttab.cons_list (gid, task)) (group_ancestry group);

    val jobs' = jobs

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

      |> fold (add_job task) deps

      |> fold (fold (add_job task) o get_deps jobs) deps;

    val minimal = null (get_deps jobs' task);

  in ((task, minimal), 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_towards -- adhoc dependencies *)

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

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

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

  let

    fun ready task = ready_job task (Task_Graph.get_entry jobs task);

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

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

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

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

  in

    (case get_first ready tasks of

      SOME res => result res

    | NONE =>

        (case get_first (get_first ready o get_deps jobs) tasks of

          SOME res => result res

        | NONE => ((NONE, tasks), queue)))

  end;

(* finish *)

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

  let

    val group = get_group jobs task;

    val groups' = groups

      |> fold (fn gid => Inttab.remove_list eq_task (gid, task)) (group_ancestry group);

    val jobs' = Task_Graph.del_node task jobs;

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

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

end;