(*  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 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 is_empty: queue -> bool

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

   val cancel: queue -> group -> bool

   val cancel_all: queue -> group list

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

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

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

 (* 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);

 (* nested groups *)

 datatype group = Group of

  {parent: group option,

   id: serial,

   status: exn list ref};

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

 fun new_group parent = make_group (parent, serial (), ref []);

 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 = CRITICAL (fn () =>

   (case exn of

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

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

 fun is_canceled (Group {parent, status, ...}) = (*non-critical*)

   not (null (! status)) orelse (case parent of NONE => false | SOME group => is_canceled group);

 fun group_status (Group {parent, status, ...}) = (*non-critical*)

   ! 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));

 (* 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;

 (* 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;

 (* queue 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;

 (* 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 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;

 (* enqueue *)

 fun add_job task dep (jobs: jobs) =

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

 fun get_deps (jobs: jobs) task =

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

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

   let

     val task = new_task 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);

     val cache' =

       (case cache of

         Result last =>

           if task_ord (last, task) = LESS

           then cache else Unknown

       | _ => Unknown);

   in ((task, minimal), 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 thread (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) 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 thread 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) 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 (get_first ready o Task_Graph.imm_preds jobs) tasks of

           SOME res => result res

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

   end;

 (* finish *)

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

   let

     val group = get_group jobs task;

     val groups' = groups

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

     val jobs' = Task_Graph.del_node task jobs;

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

     val cache' = if maximal then cache else Unknown;

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

 end;