class_name PresentationRelevancePolicy
extends RefCounted

const DEFAULT_DETAIL_LIMIT := 40
const MAX_DETAIL_LIMIT := 40
const IMPORTANCE_SCORE_SCALE := 1_000_000
const NAMED_SCORE_BONUS := 125_000
const MAX_DISTANCE_PENALTY := 1_000_000

const PIN_FIELDS := {
	"pinned": "pin_explicit",
	"player_affecting_threat": "pin_player_affecting_threat",
	"situation_participant": "pin_situation_participant",
	"commitment_participant": "pin_commitment_participant",
	"leader": "pin_leader",
	"unique_owner": "pin_unique_owner",
}

const ALLOWED_DESCRIPTOR_FIELDS := {
	"stable_id": true,
	"context_id": true,
	"address": true,
	"importance": true,
	"named": true,
	"loaded": true,
	"pinned": true,
	"player_affecting_threat": true,
	"situation_participant": true,
	"commitment_participant": true,
	"leader": true,
	"unique_owner": true,
}


func select_detailed_visuals(
	active_context: Dictionary,
	player_address: SpatialAddress,
	candidate_descriptors: Array,
	detail_limit: int = DEFAULT_DETAIL_LIMIT
) -> Dictionary:
	var errors: Array[String] = []
	var normalized_context := _normalize_context(active_context, errors)
	_validate_player_address(player_address, normalized_context, errors)
	if detail_limit < 1 or detail_limit > MAX_DETAIL_LIMIT:
		errors.append("detail_limit must be between 1 and %d" % MAX_DETAIL_LIMIT)
	if not errors.is_empty():
		return _invalid_result(detail_limit, errors)

	var ranked: Array[Dictionary] = []
	var rejected: Array[Dictionary] = []
	var seen_ids: Dictionary = {}
	for candidate_index in candidate_descriptors.size():
		var raw_candidate: Variant = candidate_descriptors[candidate_index]
		var candidate_errors: Array[String] = []
		var normalized := _normalize_candidate(raw_candidate, candidate_index, candidate_errors)
		if not candidate_errors.is_empty():
			errors.append_array(candidate_errors)
			continue
		var stable_id: StringName = normalized["stable_id"]
		if seen_ids.has(stable_id):
			errors.append("duplicate candidate stable_id '%s'" % stable_id)
			continue
		seen_ids[stable_id] = true
		var scope_rejection := _scope_rejection(normalized, normalized_context)
		if not scope_rejection.is_empty():
			rejected.append(_rejected_scope_decision(normalized, scope_rejection))
			continue
		ranked.append(_rank_candidate(normalized, player_address))

	if not errors.is_empty():
		return _invalid_result(detail_limit, errors)

	ranked.sort_custom(_rank_before)
	var mandatory_count := 0
	for entry in ranked:
		if bool(entry["mandatory"]):
			mandatory_count += 1
	if mandatory_count > detail_limit:
		return _pin_overflow_result(detail_limit, mandatory_count, ranked, rejected)

	var selected_ids: Array[StringName] = []
	var selected_details: Array[Dictionary] = []
	for rank_index in ranked.size():
		var entry: Dictionary = ranked[rank_index]
		var decision := _decision_from_ranked_entry(entry)
		if rank_index < detail_limit:
			decision["selected"] = true
			decision["reason_trace"].append(
				(
					"selected_mandatory_pin"
					if bool(entry["mandatory"])
					else "selected_rank_%d" % rank_index
				)
			)
			selected_ids.append(entry["stable_id"])
			selected_details.append(decision)
		else:
			decision["reason_trace"].append("rejected_detail_capacity_rank_%d" % rank_index)
			rejected.append(decision)

	rejected.sort_custom(_stable_id_before)
	var decisions: Array[Dictionary] = selected_details.duplicate(true)
	decisions.append_array(rejected)
	decisions.sort_custom(_stable_id_before)
	return {
		"valid": true,
		"detail_limit": detail_limit,
		"candidate_count": candidate_descriptors.size(),
		"eligible_count": ranked.size(),
		"mandatory_count": mandatory_count,
		"selected_ids": selected_ids,
		"selected_details": selected_details,
		"rejected_ids": _decision_ids(rejected),
		"decisions": decisions,
		"errors": [] as Array[String],
	}


func get_decision(result: Dictionary, stable_id: StringName) -> Dictionary:
	for value in result.get("decisions", []):
		var decision := value as Dictionary
		if StringName(decision.get("stable_id", &"")) == stable_id:
			return decision.duplicate(true)
	return {}


func _normalize_context(active_context: Dictionary, errors: Array[String]) -> Dictionary:
	var result := {}
	for field in ["context_id", "world_id", "location_id"]:
		var value: Variant = active_context.get(field)
		if (value is not String and value is not StringName) or String(value).is_empty():
			errors.append("active_context.%s must be a non-empty stable ID" % field)
			continue
		result[field] = StringName(value)
	return result


func _validate_player_address(
	player_address: SpatialAddress, active_context: Dictionary, errors: Array[String]
) -> void:
	if player_address == null or not player_address.is_valid():
		errors.append("player_address must be a valid SpatialAddress")
		return
	if active_context.is_empty():
		return
	if player_address.get_world_id() != active_context.get("world_id", &""):
		errors.append("player_address belongs to another world")
	if player_address.get_location_id() != active_context.get("location_id", &""):
		errors.append("player_address belongs to another location")


func _normalize_candidate(
	raw_candidate: Variant, candidate_index: int, errors: Array[String]
) -> Dictionary:
	if raw_candidate is not Dictionary:
		errors.append("candidate %d must be a Dictionary descriptor" % candidate_index)
		return {}
	var descriptor: Dictionary = raw_candidate
	for field in descriptor:
		if not ALLOWED_DESCRIPTOR_FIELDS.has(String(field)):
			errors.append("candidate %d has unsupported field '%s'" % [candidate_index, field])

	var stable_id_value: Variant = descriptor.get("stable_id")
	var context_id_value: Variant = descriptor.get("context_id")
	var stable_id := _normalize_descriptor_id(stable_id_value, candidate_index, "stable_id", errors)
	var context_id := _normalize_descriptor_id(
		context_id_value, candidate_index, "context_id", errors
	)
	var address := descriptor.get("address") as SpatialAddress
	if address == null or not address.is_valid():
		errors.append("candidate %d address must be a valid SpatialAddress" % candidate_index)
	elif address.get_world_id().is_empty() or address.get_location_id().is_empty():
		errors.append("candidate %d address must name a world and location" % candidate_index)

	var importance_value: Variant = descriptor.get("importance")
	var importance := 0.0
	if importance_value is not int and importance_value is not float:
		errors.append("candidate %d importance must be numeric" % candidate_index)
	else:
		importance = float(importance_value)
		if not is_finite(importance) or importance < 0.0 or importance > 1.0:
			errors.append(
				"candidate %d importance must be finite and within [0, 1]" % candidate_index
			)

	var normalized := {
		"stable_id": stable_id,
		"context_id": context_id,
		"address": address.duplicate_address() if address != null else null,
		"importance": importance,
		"named": _normalize_bool(descriptor, "named", candidate_index, errors, false),
		"loaded": _normalize_bool(descriptor, "loaded", candidate_index, errors, false),
	}
	for pin_field in PIN_FIELDS:
		normalized[pin_field] = _normalize_bool(
			descriptor, String(pin_field), candidate_index, errors, false
		)
	return normalized


func _normalize_descriptor_id(
	value: Variant, candidate_index: int, field: String, errors: Array[String]
) -> StringName:
	if (value is not String and value is not StringName) or String(value).is_empty():
		errors.append("candidate %d %s must be a non-empty stable ID" % [candidate_index, field])
		return &""
	return StringName(value)


func _normalize_bool(
	descriptor: Dictionary,
	field: String,
	candidate_index: int,
	errors: Array[String],
	default_value: bool
) -> bool:
	if not descriptor.has(field):
		return default_value
	var value: Variant = descriptor[field]
	if value is not bool:
		errors.append("candidate %d %s must be bool" % [candidate_index, field])
		return default_value
	return bool(value)


func _scope_rejection(candidate: Dictionary, active_context: Dictionary) -> String:
	if candidate["context_id"] != active_context["context_id"]:
		return "rejected_inactive_context"
	var address: SpatialAddress = candidate["address"]
	if address.get_world_id() != active_context["world_id"]:
		return "rejected_different_world"
	if address.get_location_id() != active_context["location_id"]:
		return "rejected_different_location"
	return ""


func _rejected_scope_decision(candidate: Dictionary, reason: String) -> Dictionary:
	var pin_reasons := _pin_reasons(candidate)
	var trace: Array[String] = [reason]
	if not pin_reasons.is_empty():
		trace.append("pin_ignored_outside_active_scope")
		trace.append_array(pin_reasons)
	return {
		"stable_id": candidate["stable_id"],
		"selected": false,
		"mandatory": not pin_reasons.is_empty(),
		"score_units": 0,
		"distance_millimeters": -1,
		"reason_trace": trace,
	}


func _rank_candidate(candidate: Dictionary, player_address: SpatialAddress) -> Dictionary:
	var address: SpatialAddress = candidate["address"]
	var distance_millimeters := roundi(
		player_address.get_position().distance_to(address.get_position()) * 1000.0
	)
	var importance_units := roundi(float(candidate["importance"]) * IMPORTANCE_SCORE_SCALE)
	var named_bonus := NAMED_SCORE_BONUS if bool(candidate["named"]) else 0
	var distance_penalty := mini(distance_millimeters, MAX_DISTANCE_PENALTY)
	var pin_reasons := _pin_reasons(candidate)
	var trace: Array[String] = [
		"eligible_active_context",
		"importance_units_%d" % importance_units,
		"distance_millimeters_%d" % distance_millimeters,
	]
	if bool(candidate["named"]):
		trace.append("named_entity_bonus_%d" % NAMED_SCORE_BONUS)
	if bool(candidate["loaded"]):
		trace.append("load_state_ignored")
	trace.append_array(pin_reasons)
	return {
		"stable_id": candidate["stable_id"],
		"mandatory": not pin_reasons.is_empty(),
		"score_units": importance_units + named_bonus - distance_penalty,
		"distance_millimeters": distance_millimeters,
		"reason_trace": trace,
	}


func _pin_reasons(candidate: Dictionary) -> Array[String]:
	var result: Array[String] = []
	for field in PIN_FIELDS:
		if bool(candidate.get(field, false)):
			result.append(String(PIN_FIELDS[field]))
	return result


func _decision_from_ranked_entry(entry: Dictionary) -> Dictionary:
	return {
		"stable_id": entry["stable_id"],
		"selected": false,
		"mandatory": entry["mandatory"],
		"score_units": entry["score_units"],
		"distance_millimeters": entry["distance_millimeters"],
		"reason_trace": (entry["reason_trace"] as Array).duplicate(),
	}


func _pin_overflow_result(
	detail_limit: int, mandatory_count: int, ranked: Array[Dictionary], rejected: Array[Dictionary]
) -> Dictionary:
	var decisions: Array[Dictionary] = rejected.duplicate(true)
	for entry in ranked:
		var decision := _decision_from_ranked_entry(entry)
		decision["reason_trace"].append("rejected_unsatisfiable_pin_overflow")
		decisions.append(decision)
	decisions.sort_custom(_stable_id_before)
	return {
		"valid": false,
		"detail_limit": detail_limit,
		"candidate_count": ranked.size() + rejected.size(),
		"eligible_count": ranked.size(),
		"mandatory_count": mandatory_count,
		"selected_ids": [] as Array[StringName],
		"selected_details": [] as Array[Dictionary],
		"rejected_ids": _decision_ids(decisions),
		"decisions": decisions,
		"errors":
		[
			(
				"mandatory_pin_overflow: %d mandatory candidates exceed detail limit %d"
				% [mandatory_count, detail_limit]
			)
		],
	}


func _invalid_result(detail_limit: int, errors: Array[String]) -> Dictionary:
	errors.sort()
	return {
		"valid": false,
		"detail_limit": detail_limit,
		"candidate_count": 0,
		"eligible_count": 0,
		"mandatory_count": 0,
		"selected_ids": [] as Array[StringName],
		"selected_details": [] as Array[Dictionary],
		"rejected_ids": [] as Array[StringName],
		"decisions": [] as Array[Dictionary],
		"errors": errors.duplicate(),
	}


func _decision_ids(decisions: Array[Dictionary]) -> Array[StringName]:
	var result: Array[StringName] = []
	for decision in decisions:
		result.append(StringName(decision["stable_id"]))
	return result


func _rank_before(first: Dictionary, second: Dictionary) -> bool:
	if bool(first["mandatory"]) != bool(second["mandatory"]):
		return bool(first["mandatory"])
	if int(first["score_units"]) != int(second["score_units"]):
		return int(first["score_units"]) > int(second["score_units"])
	if int(first["distance_millimeters"]) != int(second["distance_millimeters"]):
		return int(first["distance_millimeters"]) < int(second["distance_millimeters"])
	return String(first["stable_id"]) < String(second["stable_id"])


func _stable_id_before(first: Dictionary, second: Dictionary) -> bool:
	return String(first["stable_id"]) < String(second["stable_id"])