//: Routines can be put in a 'waiting' state, from which it will be ready to
//: run again when a specific memory location changes its value. This is mu's
//: basic technique for orchestrating the order in which different routines
//: operate.

:(scenario wait_for_location)
recipe f1 [
  1:number <- copy 0
  start-running f2
  wait-for-location 1:number
  # now wait for f2 to run and modify location 1 before using its value
  2:number <- copy 1:number
]
recipe f2 [
  1:number <- copy 34
]
# if we got the synchronization wrong we'd be storing 0 in location 2
+mem: storing 34 in location 2

//: define the new state that all routines can be in

:(before "End routine States")
WAITING,
:(before "End routine Fields")
// only if state == WAITING
long long int waiting_on_location;
int old_value_of_waiting_location;
:(before "End routine Constructor")
waiting_on_location = old_value_of_waiting_location = 0;

//: primitive recipe to put routines in that state

:(before "End Primitive Recipe Declarations")
WAIT_FOR_LOCATION,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "wait-for-location", WAIT_FOR_LOCATION);
:(before "End Primitive Recipe Checks")
case WAIT_FOR_LOCATION: {
  break;
}
:(before "End Primitive Recipe Implementations")
case WAIT_FOR_LOCATION: {
  reagent loc = current_instruction().ingredients.at(0);
  canonize(loc);
  Current_routine->state = WAITING;
  Current_routine->waiting_on_location = loc.value;
  Current_routine->old_value_of_waiting_location = get_or_insert(Memory, loc.value);
  trace(9998, "run") << "waiting for location " << loc.value << " to change from " << no_scientific(get_or_insert(Memory, loc.value)) << end();
  break;
}

//: scheduler tweak to get routines out of that state

:(before "End Scheduler State Transitions")
for (long long int i = 0; i < SIZE(Routines); ++i) {
  if (Routines.at(i)->state != WAITING) continue;
  if (Routines.at(i)->waiting_on_location &&
      get_or_insert(Memory, Routines.at(i)->waiting_on_location) != Routines.at(i)->old_value_of_waiting_location) {
    trace(9999, "schedule") << "waking up routine\n" << end();
    Routines.at(i)->state = RUNNING;
    Routines.at(i)->waiting_on_location = Routines.at(i)->old_value_of_waiting_location = 0;
  }
}

//: also allow waiting on a routine to stop running

:(scenario wait_for_routine)
recipe f1 [
  1:number <- copy 0
  12:number/routine <- start-running f2
  wait-for-routine 12:number/routine
  # now wait for f2 to run and modify location 1 before using its value
  3:number <- copy 1:number
]
recipe f2 [
  1:number <- copy 34
]
+schedule: f1
+run: waiting for routine 2
+schedule: f2
+schedule: waking up routine 1
+schedule: f1
# if we got the synchronization wrong we'd be storing 0 in location 3
+mem: storing 34 in location 3

:(before "End routine Fields")
// only if state == WAITING
long long int waiting_on_routine;
:(before "End routine Constructor")
waiting_on_routine = 0;

:(before "End Primitive Recipe Declarations")
WAIT_FOR_ROUTINE,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "wait-for-routine", WAIT_FOR_ROUTINE);
:(before "End Primitive Recipe Checks")
case WAIT_FOR_ROUTINE: {
  if (SIZE(inst.ingredients) != 1) {
    raise_error << maybe(get(Recipe, r).name) << "'wait-for-routine' requires exactly one ingredient, but got " << inst.to_string() << '\n' << end();
    break;
  }
  if (!is_mu_number(inst.ingredients.at(0))) {
    raise_error << maybe(get(Recipe, r).name) << "first ingredient of 'wait-for-routine' should be a routine id generated by 'start-running', but got " << inst.ingredients.at(0).original_string << '\n' << end();
    break;
  }
  break;
}
:(before "End Primitive Recipe Implementations")
case WAIT_FOR_ROUTINE: {
  if (ingredients.at(0).at(0) == Current_routine->id) {
    raise_error << maybe(current_recipe_name()) << "routine can't wait for itself! " << current_instruction().to_string() << '\n' << end();
    break;
  }
  Current_routine->state = WAITING;
  Current_r<style>pre { line-height: 125%; }
td.linenos .normal { color: inherit; background-color: transparent; padding-left: 5px; padding-right: 5px; }
span.linenos { color: inherit; background-color: transparent; padding-left: 5px; padding-right: 5px; }
td.linenos .special { color: #000000; background-color: #ffffc0; padding-left: 5px; padding-right: 5px; }
span.linenos.special { color: #000000; background-color: #ffffc0; padding-left: 5px; padding-right: 5px; }
.highlight .hll { background-color: #ffffcc }
.highlight .c { color: #888888 } /* Comment */
.highlight .err { color: #a61717; background-color: #e3d2d2 } /* Error */
.highlight .k { color: #008800; font-weight: bold } /* Keyword */
.highlight .ch { color: #888888 } /* Comment.Hashbang */
.highlight .cm { color: #888888 } /* Comment.Multiline */
.highlight .cp { color: #cc0000; font-weight: bold } /* Comment.Preproc */
.highlight .cpf { color: #888888 } /* Comment.PreprocFile */
.highlight .c1 { color: #888888 } /* Comment.Single */
.highlight .cs { color: #cc0000; font-weight: bold; background-color: #fff0f0 } /* Comment.Special */
.highlight .gd { color: #000000; background-color: #ffdddd } /* Generic.Deleted */
.highlight .ge { font-style: italic } /* Generic.Emph */
.highlight .ges { font-weight: bold; font-style: italic } /* Generic.EmphStrong */
.highlight .gr { color: #aa0000 } /* Generic.Error */
.highlight .gh { color: #333333 } /* Generic.Heading */
.highlight .gi { color: #000000; background-color: #ddffdd } /* Generic.Inserted */
.highlight .go { color: #888888 } /* Generic.Output */
.highlight .gp { color: #555555 } /* Generic.Prompt */
.highlight .gs { font-weight: bold } /* Generic.Strong */
.highlight .gu { color: #666666 } /* Generic.Subheading */
.highlight .gt { color: #aa0000 } /* Generic.Traceback */