Semaphore task (aka ResourceGuard)

[limbonaut]

Thoughts

• Limit concurrent access to a shared resource (use elevator, med kit station, etc.).
• Should be possible to limit number of attackers vs specific targets.
• wait_for_resource: If true, the task should wait for the resource to be released; otherwise, return FAILURE when the resource is not available.
• max_concurrency: maximum number of concurrent access allowed.
  • Alternative names: counter or count, units_available, available.
• Resource can be any Object-derived instance on the blackboard.
  • Use Object::get_instance_id() for resource identification.
  • Optional: If not specified, the decorated branch is considered to be the resource that is limited, thus only a number of agents can access the limited branch.
• Intention: StringName or String
  • Default value: &"default"
  • If the resource can be used in various ways without limit, the intention property can be used to specify how exactly it will be used.
  • Intention examples: &"engage", &"heal", &"hack".
  • Not applicable when resource object is not specified (when limiting the branch executions).
  • The purpose is to limit specific interactions with the resource: "Only 2 enemies can attack player at the same time", "Only 1 pylon can heal player at the same time" (player is the resource in these examples, and attacking and healing are intentions).
  • Q: Too convoluted? Does it complicate implementation too much?
  • Q: Should it be StringName?
• Internal counter is associated with both instance_id and intention.
• Internal counter is global, and it is not associated with the agent instance or specific BehaviorTree.