anti_magic.dm

/// This provides different types of magic resistance on an object
/datum/component/anti_magic
	/// A bitflag with the types of magic resistance on the object
	var/antimagic_flags
	/// The amount of times the object can protect the user from magic
	/// Set to INFINITY to have, well, infinite charges.
	var/charges
	/// The inventory slot the object must be located at in order to activate
	var/inventory_flags
	/// The callback invoked when we have been drained a antimagic charge
	var/datum/callback/drain_antimagic
	/// The callback invoked when twe have been depleted of all charges
	var/datum/callback/expiration
	/// Whether we should, on equipping, alert the caster that this item can block any of their spells
	/// This changes between true and false on equip and drop, don't set it outright to something
	var/alert_caster_on_equip = TRUE

/**
 * Adds magic resistances to an object
 *
 * Magic resistance will prevent magic from affecting the user if it has the correct resistance
 * against the type of magic being used
 *
 * args:
 * * antimagic_flags (optional) A bitflag with the types of magic resistance on the object
 * * charges (optional) The amount of times the object can protect the user from magic
 * * inventory_flags (optional) The inventory slot the object must be located at in order to activate
 * * drain_antimagic (optional) The proc that is triggered when an object has been drained a antimagic charge
 * * expiration (optional) The proc that is triggered when the object is depleted of charges
 * *
 * antimagic bitflags: (see code/__DEFINES/magic.dm)
 * * MAGIC_RESISTANCE - Default magic resistance that blocks normal magic (wizard, spells, staffs)
 * * MAGIC_RESISTANCE_MIND - Tinfoil hat magic resistance that blocks mental magic (telepathy, abductors, jelly people)
 * * MAGIC_RESISTANCE_HOLY - Holy magic resistance that blocks unholy magic (revenant, cult, vampire, voice of god)
**/
/datum/component/anti_magic/Initialize(
	antimagic_flags = MAGIC_RESISTANCE,
	charges = INFINITY,
	inventory_flags = ~ITEM_SLOT_BACKPACK, // items in a backpack won't activate, anywhere else is fine
	datum/callback/drain_antimagic,
	datum/callback/expiration,
)

	if(isitem(parent))
		RegisterSignal(parent, COMSIG_ITEM_EQUIPPED, PROC_REF(on_equip))
		RegisterSignal(parent, COMSIG_ITEM_DROPPED, PROC_REF(on_drop))
	else if(ismob(parent))
		register_antimagic_signals(parent)
	else
		return COMPONENT_INCOMPATIBLE

	src.antimagic_flags = antimagic_flags
	src.charges = charges
	src.inventory_flags = inventory_flags
	src.drain_antimagic = drain_antimagic
	src.expiration = expiration

/datum/component/anti_magic/Destroy(force, silent)
	drain_antimagic = null
	expiration = null
	return ..()

/datum/component/anti_magic/proc/register_antimagic_signals(datum/on_what)
	RegisterSignal(on_what, COMSIG_MOB_RECEIVE_MAGIC, PROC_REF(block_receiving_magic), override = TRUE)
	RegisterSignal(on_what, COMSIG_MOB_RESTRICT_MAGIC, PROC_REF(restrict_casting_magic), override = TRUE)

/datum/component/anti_magic/proc/unregister_antimagic_signals(datum/on_what)
	UnregisterSignal(on_what, list(COMSIG_MOB_RECEIVE_MAGIC, COMSIG_MOB_RESTRICT_MAGIC))

/datum/component/anti_magic/proc/on_equip(atom/movable/source, mob/equipper, slot)
	SIGNAL_HANDLER

	if(!(inventory_flags & slot)) //Check that the slot is valid for antimagic
		unregister_antimagic_signals(equipper)
		return

	register_antimagic_signals(equipper)
	if(!alert_caster_on_equip)
		return

	// Check to see if we have any spells that are blocked due to antimagic
	for(var/datum/action/cooldown/spell/magic_spell in equipper.actions)
		if(!(magic_spell.spell_requirements & SPELL_REQUIRES_NO_ANTIMAGIC))
			continue

		if(!(antimagic_flags & magic_spell.antimagic_flags))
			continue

		to_chat(equipper, span_warning("[parent] is interfering with your ability to cast magic!"))
		alert_caster_on_equip = FALSE
		break

/datum/component/anti_magic/proc/on_drop(atom/movable/source, mob/user)
	SIGNAL_HANDLER

	// Reset alert
	if(source.loc != user)
		alert_caster_on_equip = TRUE
	unregister_antimagic_signals(user)

/datum/component/anti_magic/proc/block_receiving_magic(mob/living/carbon/source, casted_magic_flags, charge_cost, list/antimagic_sources)
	SIGNAL_HANDLER

	// We do not block this type of magic, good day
	if(!(casted_magic_flags & antimagic_flags))
		return NONE

	// We have already blocked this spell
	if(parent in antimagic_sources)
		return NONE

	// Block success! Add this parent to the list of antimagic sources
	antimagic_sources += parent

	if((charges != INFINITY) && charge_cost > 0)
		drain_antimagic?.Invoke(source, parent)
		charges -= charge_cost
		if(charges <= 0)
			expiration?.Invoke(source, parent)
			qdel(src) // no more antimagic

	return COMPONENT_MAGIC_BLOCKED

/// cannot cast magic with the same type of antimagic present
/datum/component/anti_magic/proc/restrict_casting_magic(mob/user, magic_flags)
	SIGNAL_HANDLER

	if(magic_flags & antimagic_flags)
		if(HAS_TRAIT(user, TRAIT_ANTIMAGIC_NO_SELFBLOCK)) // this trait bypasses magic casting restrictions
			return NONE
		return COMPONENT_MAGIC_BLOCKED

	return NONE