Implement isApplicable for Approaches

Approach in writer’s input now accepts `PREREQUISITES:`. This allows us to let the player bypass things they’ve already done.

edgehead/assets/text/Knights/1_bleeds/000_bleeds_main.txt

@@ -14,10 +14,16 @@ COMMAND: Go >> outside
 DESCRIPTION: [[We]] walk out into the muddy street.
 
 // ---
-APPROACH: $bleeds_main FROM $goblin_skirmish_main
+APPROACH: $bleeds_main FROM $goblin_skirmish_sneak
 COMMAND: Go >> to The Bleeds
 DESCRIPTION: [[We]] sneak through the bushes and emerge back in The Bleeds.
 
+// ---
+APPROACH: $bleeds_main FROM $goblin_skirmish_main
+COMMAND: Go >> to The Bleeds
+DESCRIPTION: [[We]] walk back to The Bleeds.
+
+
 // ---
 ROOM: $bleeds_main
 

edgehead/assets/text/Knights/1_bleeds/010_bleeds_blind_guide.txt

@@ -33,6 +33,10 @@ _"I seek treasure."_
 
 "Ahh!" The man leans back, resting his back against the wall of his house. "A terrible idea."
 
+[[CODE]]
+$(c).learnAbout(kbBlindGuide);
+[[/CODE]]
+
 
 // ---
 ACTION: $bleeds_blind_guide_terrible_idea
@@ -43,7 +47,7 @@ FOR_LOCATION: $bleeds_main
 PREREQUISITES:
 w.actionNeverUsed(name)
 &&
-w.actionHasBeenPerformed("bleeds_blind_guide_greet")
+$(c).hasLearnedAbout(kbBlindGuide)
 
 COMPLETE_SUCCESS_PROBABILITY: 100%
 
@@ -88,6 +92,8 @@ FOR_LOCATION: $bleeds_main
 PREREQUISITES:
 w.actionNeverUsed(name)
 &&
+$(c).hasLearnedAbout(kbBlindGuide)
+&&
 $(c).hasHeardAbout(kbGoblinsNearBleeds)
 
 COMPLETE_SUCCESS_PROBABILITY: 100%

edgehead/assets/text/Knights/1_bleeds/050_bleeds_trader.txt

@@ -138,6 +138,10 @@ assert($(c).inRoomWith(leroyId));
 
 "They are to the west. It doesn't seem like there is a lot of them. We thought the Knights would get rid of them for sure."
 
+[[CODE]]
+$(c).learnAbout(kbGoblinsNearBleeds);
+[[/CODE]]
+
 "But the Knights are leaving." The trader looks at me for reaction and when he doesn't get any, he turns back to his son. "The Knights are leaving," he repeats.
 
 [[CODE]]

edgehead/assets/text/Knights/1_goblin_skirmish/000_goblin_skirmish_patrol.txt

@@ -2,6 +2,10 @@
 APPROACH: $goblin_skirmish_patrol FROM $bleeds_main
 COMMAND: Go >> to the west
 DESCRIPTION: N/A
+PREREQUISITES:
+$(c).hasLearnedAbout(kbGoblinsNearBleeds)
+&&
+!$(c).playerHasVisited("goblin_skirmish_patrol")
 
 // ---
 ROOM: $goblin_skirmish_patrol

edgehead/assets/text/Knights/1_goblin_skirmish/050_goblin_skirmish_sneak.txt

@@ -0,0 +1,20 @@
+// ---
+APPROACH: $goblin_skirmish_sneak FROM $goblin_skirmish_patrol
+COMMAND: Go >> towards the goblin outpost
+DESCRIPTION: N/A
+
+// ---
+APPROACH: $goblin_skirmish_sneak FROM $bleeds_main
+COMMAND: Go >> towards the goblin outpost
+DESCRIPTION: N/A
+PREREQUISITES:
+$(c).playerHasVisited("goblin_skirmish_sneak")
+
+// ---
+ROOM: $goblin_skirmish_sneak
+
+FIRST_DESCRIPTION:
+[[We]] sneak around. It's only 3 goblins. They are speaking loudly.
+
+DESCRIPTION:
+The goblins are still here.

edgehead/assets/text/Knights/1_goblin_skirmish/100_goblin_skirmish_main.txt

@@ -1,13 +1,32 @@
 // ---
-APPROACH: $goblin_skirmish_main FROM $goblin_skirmish_patrol
-COMMAND: Go >> towards the outpost
+APPROACH: $goblin_skirmish_main FROM $bleeds_main
+COMMAND: Go >> to the goblin outpost
 DESCRIPTION: N/A
+PREREQUISITES:
+$(c).hasHappened(evGoblinCampCleared)
+
+// ---
+APPROACH: $goblin_skirmish_main FROM $goblin_skirmish_sneak
+COMMAND: Go >> attack the camp
+DESCRIPTION: N/A
+PREREQUISITES:
+!$(c).hasHappened(evGoblinCampCleared)
 
 // ---
 ROOM: $goblin_skirmish_main
 
 FIRST_DESCRIPTION:
-[[We]] sneak around. It's only 3 goblins. They are speaking loudly.
+TODO -- an actual battle with the goblins.
+
+Assume you won.
+
+[[CODE]]
+w.recordCustom(evGoblinCampCleared);
+[[/CODE]]
 
 DESCRIPTION:
-The goblins are still here.
+The goblin camp is deserted.
+
+[[CODE]]
+w.recordCustom(evGoblinCampCleared);
+[[/CODE]]

edgehead/lib/edgehead_director.dart

@@ -19,9 +19,7 @@ final _leroyQuits = Rule(_id++, 2, false, (ApplicabilityContext c) {
   final leroy = c.world.getActorById(leroyId);
   if (leroy.npc.followingActorId != playerId) return false;
   assert($(c).inRoomWith(leroyId));
-  return c.world.customHistory
-      .query(name: "cleared_goblin_skirmish")
-      .hasHappened;
+  return c.world.customHistory.query(name: evGoblinCampCleared).hasHappened;
 }, (ActionContext c) {
   final WorldStateBuilder w = c.outputWorld;
   final Storyline s = c.outputStoryline;

edgehead/lib/edgehead_ids.dart

@@ -15,6 +15,8 @@ const evDirectorNoRuleApplicable = "evDirectorNoRuleApplicable";
 
 const evGoblinCampCleared = "evGoblinCampCleared";
 
+const kbBlindGuide = "kbBlindGuide";
+
 const kbGoblinSmoke = "kbGoblinSmoke";
 
 const kbGoblinsNearBleeds = "kbGoblinsNearBleeds";

edgehead/lib/fractal_stories/room_approach.dart

@@ -22,7 +22,15 @@ class Approach {
   /// supposed to see it. They will be automatically transported.
   final bool isImplicit;
 
-  const Approach(this.from, this.to, this.command, this.description)
+  /// A callback defining whether anyone can take the approach, given
+  /// the current state of the world.
+  ///
+  /// This can (and often will) be `null`. That just means the approach
+  /// is always applicable.
+  final bool Function(ApplicabilityContext) isApplicable;
+
+  const Approach(this.from, this.to, this.command, this.description,
+      {this.isApplicable})
       : isImplicit = command == '<implicit>',
         assert(from != null),
         assert(to != null),

edgehead/lib/src/room_roaming/actions/take_approach.dart

@@ -86,6 +86,11 @@ class TakeApproachAction extends ApproachAction {
       // Don't allow exit taking when monsters in this room are still alive.
       return false;
     }
+
+    if (approach.isApplicable != null) {
+      return approach.isApplicable(c);
+    }
+
     return true;
   }
 }

edgehead/lib/src/room_roaming/actions/take_implicit_approach.dart

@@ -31,6 +31,10 @@ class TakeImplicitApproachAction extends TakeApproachAction {
       return false;
     }
 
+    if (approach.isApplicable != null) {
+      return approach.isApplicable(c);
+    }
+
     return true;
   }
 }