class_name EventKnowledgeSystem
extends RefCounted

const WITNESS_RADIUS := 10.0
const MAX_RECENT_FACTS_PER_NPC := 3

var known_events: Dictionary = {}


func observe_event(event: EconomicEventRecord, npcs: Array[SimNPC]) -> Array[KnownEventStateRecord]:
	var learned: Array[KnownEventStateRecord] = []
	if not is_knowable_event(event):
		return learned
	var actor := _find_npc(int(event.data["actor_id"]), npcs)
	if actor == null:
		return learned
	var event_id := int(event.data["event_id"])
	var acquired_tick := int(event.data["tick"])
	var actor_record := _remember(
		actor.id, event_id, SimulationIds.KNOWLEDGE_ACQUISITION_PERFORMED, acquired_tick
	)
	if actor_record != null:
		learned.append(actor_record)
	var witness_radius_squared := WITNESS_RADIUS * WITNESS_RADIUS
	var event_position := event.get_world_position()
	for npc in npcs:
		if npc.id == actor.id or npc.is_dead:
			continue
		if npc.position.distance_squared_to(event_position) > witness_radius_squared:
			continue
		var witness_record := _remember(
			npc.id, event_id, SimulationIds.KNOWLEDGE_ACQUISITION_WITNESSED, acquired_tick
		)
		if witness_record != null:
			learned.append(witness_record)
	learned.sort_custom(_sort_records)
	return learned


func communicate_event(
	event: EconomicEventRecord, speaker_id: int, listener_id: int, acquired_tick: int
) -> KnownEventStateRecord:
	if (
		event == null
		or speaker_id == listener_id
		or listener_id == int(event.data["actor_id"])
		or not is_knowable_event(event)
	):
		return null
	var event_id := int(event.data["event_id"])
	var speaker_record := get_record(speaker_id, event_id)
	if speaker_record == null:
		return null
	if (
		speaker_record.get_acquisition_method()
		not in [
			SimulationIds.KNOWLEDGE_ACQUISITION_PERFORMED,
			SimulationIds.KNOWLEDGE_ACQUISITION_WITNESSED,
		]
	):
		return null
	return _remember(
		listener_id,
		event_id,
		SimulationIds.KNOWLEDGE_ACQUISITION_COMMUNICATED,
		acquired_tick,
		speaker_id,
		speaker_record.get_acquisition_method()
	)


func knows_event(knower_id: int, event_id: int) -> bool:
	return known_events.has(_key(knower_id, event_id))


func get_record(knower_id: int, event_id: int) -> KnownEventStateRecord:
	return known_events.get(_key(knower_id, event_id)) as KnownEventStateRecord


func get_knowers(event_id: int) -> Array[int]:
	var knower_ids: Array[int] = []
	for record in known_events.values():
		if record.get_event_id() == event_id:
			knower_ids.append(record.get_knower_id())
	knower_ids.sort()
	return knower_ids


func get_known_event_ids(knower_id: int, max_count: int = 3) -> Array[int]:
	var records: Array[KnownEventStateRecord] = []
	for record in known_events.values():
		if record.get_knower_id() == knower_id:
			records.append(record)
	records.sort_custom(_sort_by_acquisition)
	var event_ids: Array[int] = []
	for record in records:
		event_ids.append(record.get_event_id())
	if max_count <= 0 or event_ids.size() <= max_count:
		return event_ids
	var recent_ids: Array[int] = []
	for index in range(event_ids.size() - max_count, event_ids.size()):
		recent_ids.append(event_ids[index])
	return recent_ids


func get_retained_event_ids(
	knower_id: int, lasting_event_ids: Array[int], max_count: int = 4
) -> Array[int]:
	return _get_ranked_event_ids(knower_id, lasting_event_ids, false, max_count)


func get_communicable_event_ids(
	knower_id: int, lasting_event_ids: Array[int], preferred_event_id: int = -1
) -> Array[int]:
	var event_ids := _get_ranked_event_ids(knower_id, lasting_event_ids, true, 0)
	if preferred_event_id in event_ids:
		event_ids.erase(preferred_event_id)
		event_ids.push_front(preferred_event_id)
	return event_ids


func _get_ranked_event_ids(
	knower_id: int, lasting_event_ids: Array[int], direct_only: bool, max_count: int
) -> Array[int]:
	var ranked: Array[Dictionary] = []
	for record in known_events.values():
		if record.get_knower_id() != knower_id:
			continue
		if (
			direct_only
			and (
				record.get_acquisition_method()
				not in KnownEventStateRecord.DIRECT_ACQUISITION_METHODS
			)
		):
			continue
		(
			ranked
			. append(
				{
					"event_id": record.get_event_id(),
					"acquired_tick": record.get_acquired_tick(),
					"lasting": record.get_event_id() in lasting_event_ids,
				}
			)
		)
	ranked.sort_custom(_sort_by_importance)
	var event_ids: Array[int] = []
	for item in ranked:
		event_ids.append(int(item["event_id"]))
		if max_count > 0 and event_ids.size() >= max_count:
			break
	return event_ids


func maintain_retention(
	current_tick: int,
	max_recent_age: int,
	lasting_records: Array[KnownEventStateRecord],
	expire_by_age: bool
) -> Array[KnownEventStateRecord]:
	var lasting_keys := {}
	for record in lasting_records:
		lasting_keys[_key(record.get_knower_id(), record.get_event_id())] = true
	var removal_keys := {}
	var recent_by_knower := {}
	for record in known_events.values():
		var key := _key(record.get_knower_id(), record.get_event_id())
		if lasting_keys.has(key):
			continue
		if expire_by_age and current_tick - record.get_acquired_tick() >= max_recent_age:
			removal_keys[key] = true
			continue
		var recent: Array = recent_by_knower.get(record.get_knower_id(), [])
		recent.append(record)
		recent_by_knower[record.get_knower_id()] = recent
	for recent in recent_by_knower.values():
		recent.sort_custom(_sort_by_acquisition)
		var excess: int = recent.size() - MAX_RECENT_FACTS_PER_NPC
		for index in range(maxi(excess, 0)):
			var record := recent[index] as KnownEventStateRecord
			removal_keys[_key(record.get_knower_id(), record.get_event_id())] = true
	var forgotten: Array[KnownEventStateRecord] = []
	for record in get_all_sorted():
		var key := _key(record.get_knower_id(), record.get_event_id())
		if not removal_keys.has(key):
			continue
		known_events.erase(key)
		forgotten.append(record)
	return forgotten


func get_all_sorted() -> Array[KnownEventStateRecord]:
	var records: Array[KnownEventStateRecord] = []
	for record in known_events.values():
		records.append(record)
	records.sort_custom(_sort_records)
	return records


func restore(records: Array[KnownEventStateRecord]) -> void:
	known_events.clear()
	for record in records:
		known_events[_key(record.get_knower_id(), record.get_event_id())] = record


func _remember(
	knower_id: int,
	event_id: int,
	acquisition_method: StringName,
	acquired_tick: int,
	source_npc_id: int = KnownEventStateRecord.NO_SOURCE_NPC_ID,
	source_acquisition_method: StringName = &""
) -> KnownEventStateRecord:
	var key := _key(knower_id, event_id)
	if known_events.has(key):
		return null
	var record := KnownEventStateRecord.create(
		knower_id,
		event_id,
		acquisition_method,
		source_npc_id,
		acquired_tick,
		source_acquisition_method
	)
	known_events[key] = record
	return record


static func is_knowable_event(event: EconomicEventRecord) -> bool:
	if event == null:
		return false
	var event_type := StringName(event.data["event_type"])
	var item_id := StringName(event.data["item_id"])
	if event_type == SimulationIds.EVENT_TASK_BLOCKED:
		return (
			int(event.data["actor_id"]) >= 0
			and StringName(event.data["source_id"]) == SimulationIds.STORAGE_VILLAGE_WOODPILE
			and item_id == SimulationIds.RESOURCE_WOOD
			and (
				StringName(event.data.get("action_id", &""))
				in [SimulationIds.ACTION_PATROL, SimulationIds.ACTION_STUDY]
			)
			and float(event.data.get("required_amount", 0.0)) > 0.0
		)
	if float(event.data["amount"]) <= 0.0:
		return false
	if event_type == SimulationIds.EVENT_STORAGE_DEPOSITED:
		return item_id == SimulationIds.RESOURCE_FOOD
	if event_type != SimulationIds.EVENT_STORAGE_WITHDRAWN:
		return false
	var actor_id := int(event.data["actor_id"])
	return (
		actor_id >= 0
		and item_id == SimulationIds.RESOURCE_FOOD
		and StringName(event.data["source_id"]) == SimulationIds.STORAGE_VILLAGE_PANTRY
		and (StringName(event.data["destination_id"]) == SimulationIds.npc_inventory_id(actor_id))
	)


static func _find_npc(npc_id: int, npcs: Array[SimNPC]) -> SimNPC:
	for npc in npcs:
		if npc.id == npc_id:
			return npc
	return null


static func _key(knower_id: int, event_id: int) -> String:
	return "%d:%d" % [knower_id, event_id]


static func _sort_records(first: KnownEventStateRecord, second: KnownEventStateRecord) -> bool:
	if first.get_knower_id() != second.get_knower_id():
		return first.get_knower_id() < second.get_knower_id()
	return first.get_event_id() < second.get_event_id()


static func _sort_by_acquisition(
	first: KnownEventStateRecord, second: KnownEventStateRecord
) -> bool:
	if first.get_acquired_tick() != second.get_acquired_tick():
		return first.get_acquired_tick() < second.get_acquired_tick()
	return first.get_event_id() < second.get_event_id()


static func _sort_by_importance(first: Dictionary, second: Dictionary) -> bool:
	if bool(first["lasting"]) != bool(second["lasting"]):
		return bool(first["lasting"])
	if int(first["acquired_tick"]) != int(second["acquired_tick"]):
		return int(first["acquired_tick"]) > int(second["acquired_tick"])
	return int(first["event_id"]) > int(second["event_id"])