feat: flag for items NPCs will use in combat.

[KheirFerrum]

Summary

SUMMARY: Features "Adds flag for items that NPCs will activate in combat."

Purpose of change

As a follow up #1505, make power armour and similar items usable by NPCs during combat.

Describe the solution

Modifies 52259 to function for most simple iuse actions, mainly transform and set_transform. The inclusion of chainsaws and chainsaw lajatangs will need a follow up PR that converts their iuse into iuse_actors for ease of use.

Canning the port, it's not going to do what I need it to do. New plan follows:

• Make iuse_transform::can_use actually account for all pre-requisites, if it returns true, then it can be used, no ifs, no buts, no niche requirements or bullshit.
• Make NPC weapon compare code account for transformed versions of wielded/unwielded items. Exclude guns for now, since things like the compound bow get weird due to cycling and strength requirements.
• Have NPCs transform worn armour if it has a target flag (there is no function that compares the value of an armour, and I'm not going to code one for this PR, since it'll likely get complicated as we factor in encumbrance and coverage.
• Have NPCs deactivate worn armour/weapons if they consume power when combat ends.

Describe alternatives you've considered

• Set up a modular system to allow players to dynamically designate what items to use.
  Not the worst idea, but this current system suffices. In the future we will need somewhat more intelligent usage of items by NPCs so that NPC enemies will be more threatening with equipment. (Optically cloaked bandits anyone?)

Testing

• Give an NPC the extendable baton, a power armour exoskeleton and helmet. Gave the NPC a UPS. Spawned a Debug Monster. Checked that NPC activated their equipment. Let it wail on the creature for a bit, then killed the Debug Monster, checked that all items returned to inactivated form.

Additional context

Unactivated Power Armour is encumbering, very heavy, and very warm, fortunately, NPCs do not suffer from stamina issues, heat issues, and encumbrance disappears when it's activated in combat.

I will need to make 2 follow up PRs to this.

• Chainsaw iuse_actor creation. To allow for Combat Chainsaws and similar to function with this code.
• NPC Bionics Update, to allow NPCs to use Bionic UPS and Bionic Armor Interfaces.

[KheirFerrum]

I'm trying to think of further things to develop here and coming up blank. None of the things I'd like are strictly a part of this PR and would be better served with follow up PRs (like the chainsaw and Bionic UPS/Interface)

[Coolthulhu]

I'm not sure if it needs an info block like this.

[chaosvolt]

I assume info block would make more sense if that were to more clearly imply activating it.

[KheirFerrum]

That makes sense, I can change it. Due to the way the flags are this is being slowly rolled out, so marking items that NPC's will activate and will not activate is important in my view

[Coolthulhu]

I don't like how it's on both active and inactive variants. If I give a NPC an extended baton, I want them to use an extended baton. In fact, it may be hard to get the NPC to equip a collapsed one.

[KheirFerrum]

So a problem with making them check for the active variant is that the iuse can_use for transforms doesn't cover all requirements, so for some requirements like need_charges the NPC will not know it can't be used until they actually use them, and if an NPC fails it's silent because of the way the messages are printed.

[Coolthulhu]

My NPC started flipping the baton on and off during the fight when given the extended variant.

[Coolthulhu]

I know the whole block above is full of methods, but they'd be better off as separate functions.
Consider a distant future when a player can let the AI control the character. If all the functionality is in npc methods, it will be harder and more hacky, but if it's all separate functions, it could be as easy as changing the npc argument to player (or even Character) one.

[KheirFerrum]

I'm not sure what protocol is for this, would I need to move the functions or shift them around in npc.h?

[KheirFerrum]

My NPC started flipping the baton on and off during the fight when given the extended variant.

Gah, of course, I forgot it only counts active. If I want to make the baton work I'll need two flags, one to activate and one to deactivate.

[Coolthulhu]

If I want to make the baton work I'll need two flags, one to activate and one to deactivate.

Or to compare their stats rather than using flags.
Or to remove the flag from batons and only keep it on active stuff.

[KheirFerrum]

Here is the point I'm restarting it from scratch, old version just doesn't work for what I need it to do.