/*
  SchedulerActivity(Test)  -  verify activities processed in the scheduler

  Copyright (C)         Lumiera.org
    2023,               Hermann Vosseler <Ichthyostega@web.de>

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 of
  the License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

* *****************************************************/

/** @file scheduler-activity-test.cpp
 ** unit test \ref SchedulerActivity_test
 */


#include "lib/test/run.hpp"
#include "lib/test/test-helper.hpp"
#include "activity-detector.hpp"
#include "vault/gear/activity-lang.hpp"
#include "vault/real-clock.hpp"
#include "lib/time/timevalue.hpp"
#include "lib/format-cout.hpp"


using test::Test;
using lib::time::Time;
using lib::time::FSecs;


namespace vault{
namespace gear {
namespace test {
  
  
  
  /*****************************************************************//**
   * @test verify behaviour of the Scheduler _Activity Language._
   * @see SchedulerCommutator_test
   * @see SchedulerUsage_test
   */
  class SchedulerActivity_test : public Test
    {
      
      virtual void
      run (Arg)
        {
          simpleUsage();
          
          verifyActivity_Post();
          verifyActivity_Invoke();
          verifyActivity_Notify_activate();
          verifyActivity_Notify_dispatch();
          verifyActivity_Gate_pass();
          verifyActivity_Gate_dead();
          verifyActivity_Gate_block();
          verifyActivity_Gate_opened();
          
          termBuilder();
          dispatchChain();
          
          scenario_RenderJob();
          scenario_Notification();
          scenario_IOJob();
          scenario_MetaJob();
        }
      
      
      /** @test demonstrate simple Activity usage */
      void
      simpleUsage()
        {
          // Activities are »POD with constructor«
          Activity start{Activity::WORKSTART};
          CHECK (start.verb_ == Activity::WORKSTART);
          CHECK (start.next  == nullptr);
          CHECK (start.data_.timing.instant == Time::NEVER);       //////////////////////////////////////////TICKET #1317 : the purpose of this time data is not clear yet
          CHECK (start.data_.timing.quality == 0);
          
          // use the ActivityDetector for test instrumentation...
          ActivityDetector detector;
          
          // Activities can be invoked within an ExecutionContext
          Time now = RealClock::now();
          start.activate (now, detector.executionCtx);
          
          // In this case, activation causes invocation of λ-work on the context
          CHECK (detector.verifyInvocation("CTX-work").arg(now, 0));
          
//        cout << detector.showLog()<<endl; // HINT: use this for investigation...
        }
      
      
      
      /** @test behaviour of Activity::POST
       *        - invoke the λ-post to dispatch the chain through the queue
       *        - the chain to be executed is given as `next`
       *        - time window for scheduling as data field
       */
      void
      verifyActivity_Post()
        {
          Activity chain;
          Activity post{Time{0,11}, Time{0,22}, &chain};
          CHECK (chain.is (Activity::TICK));
          CHECK (post .is (Activity::POST));
          CHECK (Time(0,11) == post.data_.timeWindow.life);
          CHECK (Time(0,22) == post.data_.timeWindow.dead);
          CHECK ( & chain   == post.next);
          
          ActivityDetector detector;
          Time tt{11,11};
          post.activate (tt, detector.executionCtx);
          
          CHECK (detector.verifyInvocation("CTX-post").arg("11.011", "Act(POST", "≺test::CTX≻"));
        }
      
      
      
      /** @test behaviour of Activity::INVOKE
       *        - setup requires two FEED-Activities to be chained up as arguments
       *        - use the rigged execution context provided by ActivityDetector
       *        - can verify this way that the activation leads to JobFunctor invocation
       */
      void
      verifyActivity_Invoke()
        {
          ActivityDetector detector;
          
          uint64_t x1=rand(), x2=rand();
          Time nomTime = lib::test::randTime();
          Activity feed{x1,x2};
          Activity feed2{x1+1,x1+2};
          feed.next = &feed2;
          Activity invoke{detector.buildMockJobFunctor("job"), nomTime, feed};
          
          Time realTime = RealClock::now();
          CHECK (activity::PASS == invoke.activate (realTime, detector.executionCtx));
          
          CHECK (detector.verifyInvocation ("job").arg(nomTime, x1));
        }
      
      
      
      /** @test behaviour of Activity::NOTIFY when _activated_
       *        - notification is dispatched as special message to an indicated target Activity
       *        - when activated, a `NOTIFY`-Activity _posts itself_ through the Execution Context hook
       *        - this way, further processing will happen in management mode (single threaded)
       */
      void
      verifyActivity_Notify_activate()
        {
          Activity chain;
          Activity notify{&chain};
          
          ActivityDetector detector;
          Time tt{111,11};
          notify.activate (tt, detector.executionCtx);
          
          CHECK (detector.verifyInvocation("CTX-post").arg("11.111", "Act(NOTIFY", "≺test::CTX≻"));
        }
      
      
      
      /** @test behaviour of Activity::NOTIFY when activation leads to a _dispatch_
       *        - when _posting_ a `NOTIFY`, a dedicated _notification_ function is invoked on the chain
       *        - what actually happens then depends on the receiver; here we just activate a test-Tap
       */
      void
      verifyActivity_Notify_dispatch()
        {
          ActivityDetector detector;
                                   // use a diagnostic Tap as chain to detect passing of notification
          Activity notify{detector.buildActivationProbe("notifyTargetActivity")};
          
          Time tt{111,11};
          notify.dispatch (tt, detector.executionCtx);
          
          CHECK (detector.verifyInvocation("notifyTargetActivity").arg("11.111"));
        }
      
      
      
      /** @test behaviour of Activity::GATE:
       *        if conditions are met, the activation is just passed,
       *        so the executor (in the Scheduler) will just invoke the chain
       */
      void
      verifyActivity_Gate_pass()
        {
          Activity chain;
          Activity gate{0};
          gate.next = &chain;
          
          ActivityDetector detector;
          Activity& wiring = detector.buildGateWatcher (gate);
          
          Time tt{333,33};
          CHECK (activity::PASS == wiring.activate (tt, detector.executionCtx));
          CHECK (detector.verifyInvocation("tap-GATE").arg("33.333 ⧐ Act(GATE"));
        }
      
      
      
      /** @test behaviour of Activity::GATE:
       *        the rest of the chain is just skipped in case of deadline violation
       */
      void
      verifyActivity_Gate_dead()
        {
          Activity chain;
          Activity gate{0, Time{333,33}};
          gate.next = &chain;
          
          ActivityDetector detector;
          Activity& wiring = detector.buildGateWatcher (gate);
          
          Time t1{330,33};   // still before the deadline
          Time t2{333,33};   // exactly at deadline => rejected
          Time t3{335,33};   // after the deadline  => rejected
          
          CHECK (activity::PASS == wiring.activate (t1, detector.executionCtx));
          CHECK (detector.verifyInvocation("tap-GATE").arg("33.330 ⧐ Act(GATE").seq(0));
          
          detector.incrementSeq();
          CHECK (activity::SKIP == wiring.activate (t2, detector.executionCtx));
          CHECK (detector.verifyInvocation("tap-GATE").arg("33.333 ⧐ Act(GATE").seq(1));
          
          detector.incrementSeq();
          CHECK (activity::SKIP == wiring.activate (t3, detector.executionCtx));
          CHECK (detector.verifyInvocation("tap-GATE").arg("33.335 ⧐ Act(GATE").seq(2));
        }
      
      
      
      /** @test behaviour of Activity::GATE:
       *        the count-down condition determines if activation _passes_
       *        or will _spin around_ for later re-try
       */
      void
      verifyActivity_Gate_block()
        {
          Activity chain;
          Activity gate{23};
          gate.next = &chain;
          
          ActivityDetector detector;
          Activity& wiring = detector.buildGateWatcher (gate);
          
          Time tt{333,33};
          CHECK (activity::SKIP == wiring.activate (tt, detector.executionCtx));
          CHECK (23 == gate.data_.condition.rest);  //  prerequisite-count not altered
          
          Time reScheduled = tt + detector.executionCtx.getWaitDelay();
          CHECK (tt < reScheduled);
          
          CHECK (detector.verifyInvocation("tap-GATE").arg("33.333 ⧐ Act(GATE")
                         .beforeInvocation("CTX-post").arg(reScheduled, "Act(GATE", "≺test::CTX≻"));
        }
      
      
      
      /** @test behaviour of Activity::GATE on notification
       *        - Gate configured initially such that it blocks
       *          (without violating deadline)
       *        - thus a regular activation signals to skip the chain,
       *          but also re-schedules a further check into the future
       *        - when receiving a notification, the latch is decremented
       *        - if this causes the Gate to open, the chain is immediately
       *          scheduled for activation, but the Gate also locked forever
       *        - neither a further activation, or a further notification
       *          has any effect after this point...
       */
      void
      verifyActivity_Gate_opened()
        {
          Activity chain;
          Activity gate{1};
          gate.next = &chain;
          // Conditionals in the gate block invocations
          CHECK (gate.data_.condition.isHold());
          CHECK (gate.data_.condition.rest == 1);
          CHECK (gate.data_.condition.dead == Time::NEVER);
          
          ActivityDetector detector;
          Activity& wiring = detector.buildGateWatcher (gate);
          
          Time tt{333,33};
          Time reScheduled = tt + detector.executionCtx.getWaitDelay(); // retrieve the next time to retry
          CHECK (tt < reScheduled);
          
          // an attempt to activate blocks (and re-schedules for later retry)
          CHECK (activity::SKIP == wiring.activate (tt, detector.executionCtx));
          CHECK (1 == gate.data_.condition.rest); // unchanged (and locked)...
          CHECK (detector.verifyInvocation("tap-GATE").arg("33.333 ⧐ Act(GATE")
                         .beforeInvocation("CTX-post").arg(reScheduled, "Act(GATE", "≺test::CTX≻"));
          
          detector.incrementSeq();
          // Gate receives a notification from some prerequisite Activity
          CHECK (activity::PASS == wiring.notify(tt, detector.executionCtx));
          CHECK (0 == gate.data_.condition.rest); // condition has been decremented...
          
          CHECK (detector.verifyInvocation("tap-GATE").seq(0).arg("33.333 ⧐ Act(GATE")
                         .beforeInvocation("CTX-post").seq(0).arg(reScheduled, "Act(GATE", "≺test::CTX≻")
                         .beforeInvocation("tap-GATE").seq(1).arg("33.333 --notify-↯> Act(GATE")
                         .beforeInvocation("CTX-post").seq(1).arg(tt, "after-GATE", "≺test::CTX≻"));
          CHECK (gate.data_.condition.dead == Time::MIN);
          
          detector.incrementSeq();
          Time ttt{444,44};
          // when the re-scheduled check happens later, it is blocked to prevent double activation
          CHECK (activity::SKIP == wiring.activate (ttt, detector.executionCtx));
          CHECK (detector.verifyInvocation("tap-GATE").seq(2).arg("44.444 ⧐ Act(GATE"));
          CHECK (detector.ensureNoInvocation("CTX-post").seq(2));
          CHECK (gate.data_.condition.dead == Time::MIN);
          
          detector.incrementSeq();
          // even a further notification has no effect now....
          wiring.notify(ttt, detector.executionCtx);
          // conditionals were not touched:
          CHECK (gate.data_.condition.dead == Time::MIN);
          CHECK (gate.data_.condition.rest == 0);
          // the log shows the further notification (at Seq=3) but no dispatch happens anymore
          CHECK (detector.verifySeqIncrement(3)
                         .beforeInvocation("tap-GATE").seq(3).arg("44.444 --notify-↯> Act(GATE"));
          CHECK (detector.ensureNoInvocation("CTX-post").seq(3).arg(tt, "after-GATE", "≺test::CTX≻"));
          
//        cout << detector.showLog()<<endl; // HINT: use this for investigation...
        }
      
      
      
      /** @test verify the Activity term builder
       *        - use the builder syntax to define a simple Activity chain
       *        - verify the basic outfitting and sane connectivity
       *        - verify values reported by the BlockFlow allocator
       *        - ensure the defined Job can be properly invoked
       */
      void
      termBuilder()
        {
          ActivityDetector detector;
          
          BlockFlowAlloc bFlow;
          ActivityLang activityLang{bFlow};

          Time start{0,1};
          Time dead{0,10};
          Activity* act{nullptr};
          {
            auto term = activityLang.buildCalculationJob (detector.buildMockJob(), start,dead);
            
            act = & term.post();
          }// NOTE: generated Activity chain remains valid after term goes out of scope
          
          // Values reported for the BlockFlow allocator look sane...
          CHECK (watch(bFlow).cntElm()    == 7);               // POST, GATE, WORKSTART, INVOKE, FEED, FEED, WORKSTOP
          CHECK (watch(bFlow).cntEpochs() == 1);               // all placed into a single epoch...
          CHECK (watch(bFlow).find(*act) > dead);              // which terminates shortly after the given deadline
          CHECK (watch(bFlow).find(*act) < dead+Time(500,0));
          
          // Time window parameters have been included
          CHECK (act->is (Activity::POST));
          CHECK (start == act->data_.timeWindow.life);
          CHECK (dead  == act->data_.timeWindow.dead);
          
          // sane wiring, leading to an INVOCATE eventually
          while (not act->is (Activity::INVOKE))
            act = act->next;
          
          CHECK (act->is (Activity::INVOKE));
          CHECK (watch(bFlow).find(*act) != Time::NEVER);      // can also be found within the BlockFlow allocator
          
          // this invocation is properly defined and executable
          Time now{55,5};
          CHECK (activity::PASS == act->activate (now, detector.executionCtx));
          CHECK (detector.verifyInvocation("mockJob"));
        }
      
      
      
      /** @test verify the ability to _dispatch and perform_ a chain of activities.
       *        - use a directly wired, arbitrary chain
       *        - dispatch will activate all Activities
       *        - however, when the Gate is configured to be blocked
       *          (waiting on prerequisites), then the rest of the chain is not activated,
       *          only a re-check of the Gate is scheduled for later (1.011 -> 2.011)
       *        - the dispatch function also handles the notifications;
       *          when a notification towards the Gate is dispatched, the Gate is
       *          decremented and thereby opened; activation of the rest of the chain
       *          is then planned (but not executed synchronously in the same call)
       */
      void
      dispatchChain()
        {
          Time tt{11,1};
          Activity tick;
          Activity gate{0};
          gate.next = &tick;
          Activity post{tt, &gate};
          // so now we have POST ⟶ GATE ⟶ TICK;
          
          ActivityDetector detector;
          detector.executionCtx.getSchedTime = [&]{ return tt; };
          // insert instrumentation to trace activation
          detector.watchGate (post.next, "Gate");
          
          CHECK (activity::PASS == ActivityLang::dispatchChain (post, detector.executionCtx));          // start execution (case/seq == 0)
          CHECK (detector.verifyInvocation("Gate")      .arg("1.011 ⧐ Act(GATE")                        // ...first the Gate was activated
                         .beforeInvocation("after-Gate").arg("1.011 ⧐ Act(TICK")                        // ...then activation passed out of Gate...
                         .beforeInvocation("CTX-tick")  .arg("1.011"));                                 // ...and finally the TICK invoked the λ-tick

          detector.incrementSeq();
          gate.data_.condition.incDependencies(); // Gate is blocked
          CHECK (activity::PASS == ActivityLang::dispatchChain (post, detector.executionCtx));          // start execution (case/seq == 1)
          CHECK (detector.verifyInvocation("Gate")    .seq(1).arg("1.011 ⧐ Act(GATE")                   // ...the Gate was activated...
                         .beforeInvocation("CTX-post").seq(1).arg("2.011","Act(GATE","≺test::CTX≻"));   // ...but was found blocked and re-scheduled itself to 2.011
          CHECK (detector.ensureNoInvocation("after-Gate").seq(1)                                       // verify activation was not passed out behind Gate
                         .afterInvocation("Gate").seq(1));
          CHECK (detector.ensureNoInvocation("CTX-tick").seq(1)                                         // verify also the λ-tick was not invoked this time
                         .afterInvocation("Gate").seq(1));
          
          detector.incrementSeq();
          Activity notify{post.next}; // Notification via instrumented connection to the Gate
          
          CHECK (activity::PASS == ActivityLang::dispatchChain (notify, detector.executionCtx));        // dispatch a notification (case/seq == 2)
          CHECK (detector.verifyInvocation("Gate")    .seq(2).arg("1.011 --notify-↯> Act(GATE")         // ...notification dispatched towards the Gate
                         .beforeInvocation("CTX-post").seq(2).arg("1.011","after-Gate","≺test::CTX≻")); // ...this opened the Gate and posted/requested activation of the rest of the chain
          CHECK (detector.ensureNoInvocation("after-Gate").seq(2)                                       // verify that activation was not passed out directly
                         .afterInvocation("CTX-post").seq(2));
          CHECK (detector.ensureNoInvocation("CTX-tick").seq(2)                                         // verify also the λ-tick was not invoked directly
                         .afterInvocation("CTX-post").seq(2));
        }
      
      
      
      
      /** @test usage scenario: Activity graph for a simple render job
       *        - build an activity term based on the »CalculationJob« wiring template
       *        - dispatch the generated Activity chain and verify sequence of invocations
       */
      void
      scenario_RenderJob()
        {
          Time nominal{7,7};
          
          Time start{0,1};
          Time dead{0,10};
          
          ActivityDetector detector;
          Job testJob{detector.buildMockJob("testJob", nominal, 12345)};
          
          TimeVar now = Time{5,5};
          detector.executionCtx.getSchedTime = [&]{ // increase "current" time on each access
                                                    now += FSecs(1,20);
                                                    return now;
                                                  };
          BlockFlowAlloc bFlow;
          ActivityLang activityLang{bFlow};
          
          // Build the Activity-Term for a simple calculation job...
          Activity& anchor = activityLang.buildCalculationJob (testJob, start,dead)
                                         .post(); // retrieve the entrance point to the chain
          
          // insert instrumentation to trace activation
          detector.watchGate (anchor.next, "theGate");
          
          CHECK (activity::PASS == ActivityLang::dispatchChain (anchor, detector.executionCtx));
          
          CHECK (detector.verifyInvocation("theGate").arg("5.105 ⧐ Act(GATE")
                         .beforeInvocation("after-theGate").arg("⧐ Act(WORKSTART")
                         .beforeInvocation("CTX-work").arg("5.155","")
                         .beforeInvocation("testJob") .arg("7.007",12345)
                         .beforeInvocation("CTX-done").arg("5.355",""));
        }
      
      
      
      /** @test usage scenario: Notification from prerequisite Jobs within time window
       *        - build [similar](\ref #scenario_RenderJob) »CalculationJob« wiring
       *        - configure extended dependency notification capabilities
       *        - Case-1 : a Notification decreases the latch, but blocks otherwise
       *        - Case-2 : when the primary chain is activated after the Notification,
       *          then the tail chain behind the Gate is dispatched
       */
      void
      scenario_Notification()
        {
          Time nominal{7,7};
          Time start{0,1};
          Time dead{0,10};
          
          ActivityDetector detector;
          Job testJob{detector.buildMockJob("testJob", nominal, 12345)};
          
          BlockFlowAlloc bFlow;
          ActivityLang activityLang{bFlow};
          
          // emulate a blocking prerequisite dependency
          Activity trigger{Activity::NOTIFY};
          
          // Build the Activity-Term...
          auto term = activityLang.buildCalculationJob (testJob, start,dead)
                                  .expectNotification (trigger)               // ...require notification from prerequisite
                                  .requireDirectActivation();                 // ...additionally insert inhibition to avoid activation
                                                                              //    before the primary-chain has been scheduled
          Activity& anchor = term.post();
          CHECK (anchor.is (Activity::POST));
          CHECK (anchor.next->is (Activity::NOTIFY));
          CHECK (anchor.next->next->is (Activity::GATE));
          CHECK (anchor.next->next->next->is (Activity::WORKSTART));
          CHECK (anchor.next->next->next->next->is (Activity::INVOKE));
          CHECK (anchor.next->next->next->next->next->is (Activity::FEED));
          CHECK (anchor.next->next->next->next->next->next->is (Activity::FEED));
          CHECK (anchor.next->next->next->next->next->next->next->is (Activity::WORKSTOP));
          CHECK (anchor.next->next->next->next->next->next->next->next == nullptr);
          
          // insert test-instrumentation to trace activation
          detector.watchGate (anchor.next->next, "theGate");
          detector.insertActivationTap(trigger.data_.notification.target, "trigger");
          detector.insertActivationTap(anchor.next->data_.notification.target, "deBlock");
          
          // rig the λ-post to forward dispatch as expected in real usage
          detector.executionCtx.post.implementedAs(
            [&](Time when, Activity& postedAct, auto& ctx)
               {
                 if (when == ctx.getSchedTime())  // only for POST to run „right now“
                   return activityLang.dispatchChain (postedAct, ctx);
                 else
                   return activity::PASS;
               });
          
          ///// Case-1 : send a notification from prerequisite, but prior to activating primary-chain
          CHECK (activity::PASS == ActivityLang::dispatchChain (trigger, detector.executionCtx));
          CHECK (detector.verifyInvocation("trigger") .seq(0).arg("5.555 --notify-↯> Act(GATE")              // notification dispatched to the Gate
                                                             .arg("<2, until 0:00:10.000"));                 // Note: the Gate-latch expects 2 notifications
          CHECK (detector.ensureNoInvocation("testJob")                                                      // ==>   the latch was decremented but no invocation yet
                         .afterInvocation("trigger"));
          
          ///// Case-2 : now activate the primary-chain
          detector.incrementSeq();
          CHECK (activity::PASS == ActivityLang::dispatchChain (anchor, detector.executionCtx));
          CHECK (detector.verifyInvocation("CTX-post").seq(1).arg("5.555","Act(NOTIFY","≺test::CTX≻")        // immediately at begin, the internal self-notification is posted
                         .beforeInvocation("deBlock") .seq(1).arg("5.555 --notify-↯> Act(GATE")              // ...and then dispatched recursively via ActivityLang::dispatchChain() towards the Gate
                                                             .arg("<1, until 0:00:10.000")                   // Note: at this point, the Gate-latch expects 1 notifications
                         .beforeInvocation("CTX-post").seq(1).arg("5.555","after-theGate","≺test::CTX≻")     // ==>   the latch was decremented and the Gate OPENS, and thus post() the tail-chain
                         .beforeInvocation("after-theGate")  .arg("5.555 ⧐ Act(WORKSTART")                   // ...causing the activation to pass behind the Gate
                         .beforeInvocation("CTX-work").seq(1).arg("5.555","")                                // ...through WORKSTART
                         .beforeInvocation("testJob") .seq(1).arg("7.007",12345)                             // ...then invoke the JobFunctor itself (with the nominal Time{7,7})
                         .beforeInvocation("CTX-done").seq(1).arg("5.555","")                                // ...and finally the WORKSTOP
                         .beforeInvocation("theGate") .seq(1).arg("5.555 ⧐ Act(GATE")                        // RETURN to the primary-chain activation (after the internal self-notification)
                                                             .arg("<0, until -85401592:56:01.825"));         // -- however, after opening the Gate, the notification has blocked it permanently
          CHECK (detector.ensureNoInvocation("testJob")                                                      // ==>  thus no further (redundant) activation of the JobFunctor
                         .afterInvocation("CTX-done").seq(1));
          
          detector.incrementSeq();
          CHECK (activity::PASS == ActivityLang::dispatchChain (trigger, detector.executionCtx));            // and any further external trigger is likewise blocked:
          CHECK (detector.verifyInvocation("trigger") .seq(2).arg("5.555 --notify-↯> Act(GATE")              // ... it reaches the Gate
                                                             .arg("<0, until -85401592:56:01.825"));         // ... but the Gate has been closed permanently (by setting the deadline to Time::MIN)
          CHECK (detector.ensureNoInvocation("testJob")                                                      // ==>  no further invocation
                         .afterInvocation("trigger").seq(2));
          
//        cout << detector.showLog()<<endl; // HINT: use this for investigation...
        }
      
      
      
      /** @test usage scenario: Activity graph for an async Job
       *        - use a simple [calculation job term](\ref #scenario_RenderJob) as follow-up receiver
       *        - build an activity Term based on the »Async Load Job« wiring and link it to the receiver
       *        - also retrieve the Activity record used as re-entrance point after completing async IO
       */
      void
      scenario_IOJob()
        {
          Time nominal{7,7};
          Time start{0,1};
          Time dead{0,10};
          
          ActivityDetector detector;
          Job loadJob{detector.buildMockJob("loadJob", nominal, 12345)};
          Job calcJob{detector.buildMockJob("calcJob")};

          BlockFlowAlloc bFlow;
          ActivityLang activityLang{bFlow};
          
          auto followup = activityLang.buildCalculationJob (calcJob, start,dead);
          auto loadTerm = activityLang.buildAsyncLoadJob (loadJob, start,dead)
                                      .appendNotificationTo (followup);
          
          Activity& anchor = loadTerm.post();
          Activity& notify = loadTerm.callback();
          
          CHECK (anchor.is (Activity::POST));
          CHECK (anchor.next->is (Activity::WORKSTART));
          CHECK (anchor.next->next->is (Activity::INVOKE));
          CHECK (anchor.next->next->next->is (Activity::FEED));
          CHECK (anchor.next->next->next->next->is (Activity::FEED));
          CHECK (anchor.next->next->next->next->next == nullptr);                                            // Note: chain is severed here
          
          CHECK (notify.is (Activity::WORKSTOP));                                                            // ...WORKSTOP will be emitted from callback
          CHECK (notify.next->is (Activity::NOTIFY));                                                        // ...followed by notification of dependent job(s)
          CHECK (notify.next->next == nullptr);
          
          CHECK (notify.next->data_.notification.target == followup.post().next);                            // was wired to the GATE of the follow-up activity Term
          CHECK (followup.post().next->is (Activity::GATE));
          
          
          ///// Case-1 : trigger off the async IO job
          CHECK (activity::PASS == ActivityLang::dispatchChain (anchor, detector.executionCtx));
          CHECK (detector.verifyInvocation("CTX-work").seq(0).arg("5.555", "")                               // activation of WORKSTART
                         .beforeInvocation("loadJob") .seq(0).arg("7.007", 12345));                          // activation of JobFunctor
          CHECK (detector.ensureNoInvocation("CTX-done").seq(0)                                              // IO operation just runs, no further activity yet
                         .afterInvocation("loadJob").seq(0));
          
          
          ///// Case-2 : activate the rest of the chain after IO is done
          detector.incrementSeq();
          CHECK (activity::PASS == ActivityLang::dispatchChain (notify, detector.executionCtx));
          CHECK (detector.verifyInvocation("CTX-done").seq(1).arg("5.555", "")                               // activation of WORKSTOP via callback
                         .beforeInvocation("CTX-post").seq(1).arg("5.555", "Act(NOTIFY", "≺test::CTX≻"));    // the following NOTIFY is posted...
        }
      
      
      
      /** @test usage scenario: Activity graph for administrative job
       *        - by default, neither Gate, nor start/stop notification used
       *        - rather, the `INVOKE` and the argument-`FEED` is posted directly
       *  @remark the job itself is thus performed in »management mode«
       *        (holding the `GroomingToken`), and may modify the queue
       *        to generate new jobs.
       */
      void
      scenario_MetaJob()
        {
          Time nominal{7,7};
          Time start{0,1};
          Time dead{0,10};
          
          ActivityDetector detector;
          Job testJob{detector.buildMockJob("metaJob", nominal, 12345)};
          
          BlockFlowAlloc bFlow;
          ActivityLang activityLang{bFlow};
          
          // Build Activity-Term with a chain defining a meta-job...
          Activity& anchor = activityLang.buildMetaJob (testJob, start,dead)
                                         .post();
          
          CHECK (anchor.is (Activity::POST));
          CHECK (anchor.next->is (Activity::INVOKE));
          CHECK (anchor.next->next->is (Activity::FEED));
          CHECK (anchor.next->next->next->is (Activity::FEED));
          CHECK (anchor.next->next->next->next == nullptr);
          
          // insert test-instrumentation
          detector.insertActivationTap(anchor.next);
          
          CHECK (activity::PASS == ActivityLang::dispatchChain (anchor, detector.executionCtx));

          CHECK (detector.verifyInvocation("tap-INVOKE").arg("5.555 ⧐ Act(INVOKE")
                         .beforeInvocation("metaJob") .arg("7.007",12345));
        }
    };
  
  
  /** Register this test class... */
  LAUNCHER (SchedulerActivity_test, "unit engine");
  
  
  
}}} // namespace vault::gear::test