class_name NetworkChatService
extends Node

const BURST_COUNT: int = 3
const WINDOW_COUNT: int = 5
const WINDOW_SECONDS: float = 10.0

signal message_received(message: Dictionary)
signal send_rejected(message: String)
signal history_replaced(messages: Array[Dictionary])

var _session: NetworkSession
var _history: Array[Dictionary] = []
var _seen_messages: Dictionary[String, bool] = {}
var _request_ledgers: Dictionary[int, Dictionary] = {}
var _rate_times: Dictionary[int, Array] = {}
var _sequence: int = 0
var _peer_names: Dictionary[int, String] = {}
var _relationships: PlayerRelationshipStore


func setup(session: NetworkSession) -> void:
	_session = session
	_session.peer_authenticated.connect(_on_peer_authenticated)
	_session.peer_removed.connect(_on_peer_removed)
	_session.state_changed.connect(_on_session_state_changed)
	_session.peer_display_name_changed.connect(
		func(peer_id: int, display_name: String) -> void:
			_peer_names[peer_id] = display_name
	)


func set_relationship_store(store: PlayerRelationshipStore) -> void:
	_relationships = store


func refresh_relationship_filters() -> void:
	history_replaced.emit(get_history())


func is_sender_filtered(fingerprint: String) -> bool:
	return (
		_relationships != null
		and _relationships.is_muted(fingerprint)
	)


func send_local_message(body: String) -> bool:
	if (
		_session == null
		or not _session.is_gameplay_session_active()
		or (
			not _session.is_host()
			and not _session.supports_server_capability(
				NetworkChatProtocol.CAPABILITY
			)
		)
	):
		send_rejected.emit("Chat is unavailable.")
		return false
	var clean := NetworkChatProtocol.sanitize_body(body)
	if clean.is_empty():
		send_rejected.emit("Message is empty or too long.")
		return false
	var request := {
		"request_id": _new_id("chat_request"),
		"session_id": _session.get_session_id(),
		"body": clean,
		"sender_fingerprint": _session.get_local_identity_fingerprint(),
	}
	request["sender_signature"] = _session.sign_local_action(
		"chat_send", NetworkChatProtocol.signature_fields(request)
	)
	if _session.is_host():
		_handle_request(_session.get_local_peer_id(), request)
	else:
		submit_chat_message.rpc_id(1, request)
	return true


func get_history() -> Array[Dictionary]:
	var result: Array[Dictionary] = []
	for message: Dictionary in _history:
		if _message_is_visible(message):
			result.append(message.duplicate(true))
	return result


@rpc("any_peer", "call_remote", "reliable", NetworkChatProtocol.RELIABLE_CHANNEL)
func submit_chat_message(data: Dictionary) -> void:
	var sender_id := multiplayer.get_remote_sender_id()
	if _session.is_host() and _session.is_authenticated_peer(sender_id):
		_handle_request(sender_id, data)


func _handle_request(peer_id: int, data: Dictionary) -> void:
	if (
		not NetworkChatProtocol.validate_request(data)
		or str(data["session_id"]) != _session.get_session_id()
	):
		_send_rejection(peer_id, "Message could not be sent.")
		return
	var record := _session.get_peer_record(peer_id)
	if (
		record == null
		or record.identity_fingerprint != str(data["sender_fingerprint"])
		or not _session.verify_peer_action(
			peer_id,
			"chat_send",
			NetworkChatProtocol.signature_fields(data),
			data["sender_signature"],
		)
	):
		_send_rejection(peer_id, "Message identity could not be verified.")
		return
	var request_id: String = data["request_id"]
	var ledger: Dictionary = _request_ledgers.get(peer_id, {})
	if ledger.has(request_id):
		_send_message(peer_id, ledger[request_id])
		return
	if not _consume_rate(peer_id):
		_send_rejection(peer_id, "Slow down.")
		return
	var message := _make_message(
		NetworkChatProtocol.Kind.PLAYER,
		peer_id,
		record.display_name,
		NetworkChatProtocol.sanitize_body(data["body"])
	)
	message["request_id"] = request_id
	message["sender_fingerprint"] = data["sender_fingerprint"]
	message["sender_signature"] = data["sender_signature"]
	ledger[request_id] = message.duplicate(true)
	while ledger.size() > 64:
		ledger.erase(ledger.keys().front())
	_request_ledgers[peer_id] = ledger
	_broadcast(message)


func _make_message(
	kind: int,
	peer_id: int,
	display_name: String,
	body: String,
) -> Dictionary:
	_sequence += 1
	var message := {
		"message_id": _new_id("chat"),
		"request_id": _new_id("chat_system"),
		"session_id": _session.get_session_id(),
		"sequence": _sequence,
		"kind": kind,
		"sender_peer_id": peer_id,
		"sender_display_name": display_name.left(24),
		"body": body,
		"sender_fingerprint": _session.get_host_identity_fingerprint(),
	}
	if kind == NetworkChatProtocol.Kind.SYSTEM:
		message["sender_signature"] = _session.sign_host_action(
			"chat_system", NetworkChatProtocol.signature_fields(message)
		)
	return message


func _broadcast(message: Dictionary) -> void:
	_apply_message(message)
	receive_chat_message.rpc(message)


func _send_message(peer_id: int, message: Dictionary) -> void:
	if peer_id == _session.get_local_peer_id():
		_apply_message(message)
	else:
		receive_chat_message.rpc_id(peer_id, message)


@rpc("authority", "call_remote", "reliable", NetworkChatProtocol.RELIABLE_CHANNEL)
func receive_chat_message(data: Dictionary) -> void:
	_apply_message(data)


func _apply_message(data: Dictionary) -> void:
	if (
		not NetworkChatProtocol.validate_message(data)
		or str(data["session_id"]) != _session.get_session_id()
		or _seen_messages.has(str(data["message_id"]))
	):
		return
	var kind := int(data["kind"])
	var valid_signature := false
	if kind == NetworkChatProtocol.Kind.SYSTEM:
		valid_signature = _session.verify_host_action(
			"chat_system",
			NetworkChatProtocol.signature_fields(data),
			data["sender_signature"],
		)
	else:
		var sender_id := int(data["sender_peer_id"])
		var record := _session.get_peer_record(sender_id)
		valid_signature = (
			record != null
			and record.identity_fingerprint == str(data["sender_fingerprint"])
			and _session.verify_peer_action(
				sender_id,
				"chat_send",
				NetworkChatProtocol.signature_fields(data),
				data["sender_signature"],
			)
		)
	if not valid_signature:
		return
	_seen_messages[data["message_id"]] = true
	_history.append(data.duplicate(true))
	while _history.size() > NetworkChatProtocol.MAX_HISTORY:
		_history.pop_front()
	if _message_is_visible(data):
		message_received.emit(data.duplicate(true))


func _send_rejection(peer_id: int, message: String) -> void:
	if peer_id == _session.get_local_peer_id():
		send_rejected.emit(message)
	else:
		receive_chat_rejection.rpc_id(peer_id, message.left(80))


@rpc("authority", "call_remote", "reliable", NetworkChatProtocol.RELIABLE_CHANNEL)
func receive_chat_rejection(message: String) -> void:
	send_rejected.emit(message.left(80))


func _on_peer_authenticated(peer_id: int, display_name: String) -> void:
	if not _session.is_host():
		return
	_peer_names[peer_id] = display_name
	var start := maxi(0, _history.size() - NetworkChatProtocol.LATE_JOIN_HISTORY)
	receive_chat_history.rpc_id(peer_id, _history.slice(start))
	_broadcast(_make_message(
		NetworkChatProtocol.Kind.SYSTEM, 0, "", "%s joined." % display_name
	))


func _on_peer_removed(peer_id: int) -> void:
	_request_ledgers.erase(peer_id)
	_rate_times.erase(peer_id)
	if not _session.is_host():
		return
	var display_name: String = _peer_names.get(peer_id, "Player")
	_peer_names.erase(peer_id)
	_broadcast(_make_message(
		NetworkChatProtocol.Kind.SYSTEM, 0, "", "%s left." % display_name
	))


@rpc("authority", "call_remote", "reliable", NetworkChatProtocol.RELIABLE_CHANNEL)
func receive_chat_history(values: Array) -> void:
	if values.size() > NetworkChatProtocol.LATE_JOIN_HISTORY:
		return
	_history.clear()
	_seen_messages.clear()
	for value: Variant in values:
		if NetworkChatProtocol.validate_message(value):
			_apply_message(value)
	history_replaced.emit(get_history())


func _message_is_visible(message: Dictionary) -> bool:
	if int(message.get("kind", -1)) == NetworkChatProtocol.Kind.SYSTEM:
		return true
	if _relationships == null:
		return true
	return not _relationships.is_muted(
		str(message.get("sender_fingerprint", ""))
	)


func _consume_rate(peer_id: int) -> bool:
	var now := Time.get_ticks_msec() / 1000.0
	var times: Array = _rate_times.get(peer_id, [])
	while not times.is_empty() and now - float(times.front()) > WINDOW_SECONDS:
		times.pop_front()
	var recent_burst := 0
	for value: Variant in times:
		if now - float(value) <= 1.0:
			recent_burst += 1
	if recent_burst >= BURST_COUNT or times.size() >= WINDOW_COUNT:
		_rate_times[peer_id] = times
		return false
	times.append(now)
	_rate_times[peer_id] = times
	return true


func _on_session_state_changed(state: NetworkSession.State) -> void:
	if state in [
		NetworkSession.State.INACTIVE,
		NetworkSession.State.DISCONNECTING,
		NetworkSession.State.CONNECTION_FAILED,
		NetworkSession.State.SERVER_LOST,
	]:
		_history.clear()
		_seen_messages.clear()
		_request_ledgers.clear()
		_rate_times.clear()
		_peer_names.clear()
		_sequence = 0
		history_replaced.emit([])


func _new_id(prefix: String) -> String:
	return "%s:%s" % [
		prefix, Crypto.new().generate_random_bytes(16).hex_encode(),
	]