class_name ConnectionLeaseClient
extends Node

const AssignmentState = preload("res://scripts/assignment_state.gd")

signal reconciliation_failed(reason: String)

const CLAIMED := "claimed"
const UNAVAILABLE := "unavailable"
const REJECTED := "rejected"

var _base_url := ""
var _workload_token := ""
var _match_id := ""
var _server_id := ""
var _pending: Array[Dictionary] = []
var _processing := false


func configure(base_url: String, workload_token: String, match_id: String, server_id: String) -> bool:
	base_url = base_url.strip_edges().trim_suffix("/")
	workload_token = workload_token.strip_edges()
	if not valid_configuration(base_url, workload_token, match_id, server_id):
		return false
	_base_url = base_url
	_workload_token = workload_token
	_match_id = match_id
	_server_id = server_id
	return true


# Admission awaits one bounded request only. If the control plane is down, the
# same process may continue using its local generation and this exact event is
# retained ahead of every later disconnect/reconnect for ordered reconciliation.
func claim(player_id: String, expected_generation: int) -> Dictionary:
	if not AssignmentState.is_valid_opaque_id(player_id) or expected_generation < 0:
		return {"status": REJECTED}
	var event := _connect_event(player_id, expected_generation)
	if _processing or not _pending.is_empty():
		if expected_generation == 0:
			return {"status": REJECTED}
		_pending.append(event)
		_start_processing()
		return {"status": UNAVAILABLE, "generation": expected_generation + 1}
	var response := await _send(event, true)
	if String(response.get("status", "")) == UNAVAILABLE:
		if expected_generation == 0:
			return {"status": REJECTED}
		_pending.append(event)
		_start_processing()
		return {"status": UNAVAILABLE, "generation": expected_generation + 1}
	return response


func record_disconnect(player_id: String, generation: int) -> void:
	if not AssignmentState.is_valid_opaque_id(player_id) or generation < 1:
		return
	_pending.append(_disconnect_event(player_id, generation))
	_start_processing()


func _start_processing() -> void:
	if _processing or _pending.is_empty() or not is_inside_tree():
		return
	_process_pending()


func _process_pending() -> void:
	_processing = true
	while not _pending.is_empty() and is_inside_tree():
		var event := _pending[0]
		var response := await _send(event)
		var status := String(response.get("status", ""))
		if status == CLAIMED:
			_pending.pop_front()
			continue
		if status == REJECTED:
			reconciliation_failed.emit("durable connection lease conflict")
			_processing = false
			return
		await get_tree().create_timer(1.0).timeout
	_processing = false


func _send(event: Dictionary, allow_recovery := false) -> Dictionary:
	var request := HTTPRequest.new()
	request.timeout = 1.0
	add_child(request)
	var operation := String(event["operation"])
	var endpoint := "%s/v1/servers/%s/%s" % [_base_url, _server_id.uri_encode(), operation]
	var start_error := request.request(endpoint, [
		"Authorization: Bearer " + _workload_token,
		"Content-Type: application/json",
		"Idempotency-Key: " + String(event["key"]),
	], HTTPClient.METHOD_POST, JSON.stringify(event["payload"]))
	if start_error != OK:
		request.queue_free()
		return {"status": UNAVAILABLE}
	var raw: Array = await request.request_completed
	request.queue_free()
	return classify_response(operation, int(event["generation"]), int(raw[0]), int(raw[1]), raw[3], allow_recovery)


func _connect_event(player_id: String, expected_generation: int) -> Dictionary:
	return {
		"operation": "connect",
		"generation": expected_generation,
		"key": event_key(_match_id, player_id, "connect", expected_generation),
		"payload": {"player_id": player_id, "expected_generation": expected_generation},
	}


func _disconnect_event(player_id: String, generation: int) -> Dictionary:
	return {
		"operation": "disconnect",
		"generation": generation,
		"key": event_key(_match_id, player_id, "disconnect", generation),
		"payload": {"player_id": player_id, "generation": generation},
	}


static func classify_response(operation: String, generation: int, request_result: int, response_code: int, body: PackedByteArray, allow_recovery := false) -> Dictionary:
	if request_result != HTTPRequest.RESULT_SUCCESS or response_code == 0 or response_code == 429 or response_code >= 500:
		return {"status": UNAVAILABLE}
	if operation == "disconnect" and response_code == 204:
		return {"status": CLAIMED, "generation": generation}
	if operation == "connect" and response_code == 200:
		var decoded = JSON.parse_string(body.get_string_from_utf8())
		if decoded is Dictionary and _valid_generation(decoded.get("generation")):
			var claimed_generation := int(decoded["generation"])
			if claimed_generation == generation + 1 or (allow_recovery and generation == 0 and claimed_generation > 1):
				return {"status": CLAIMED, "generation": claimed_generation}
	return {"status": REJECTED}


static func _valid_generation(value: Variant) -> bool:
	if value is int:
		return int(value) >= 1
	if value is float:
		return is_finite(float(value)) and float(value) >= 1.0 and float(value) == floor(float(value)) and float(value) <= 9007199254740991.0
	return false


static func event_key(match_id: String, player_id: String, operation: String, generation: int) -> String:
	return "server-lease-" + (match_id + "\n" + player_id + "\n" + operation + "\n" + str(generation)).sha256_text()


static func valid_configuration(base_url: String, workload_token: String, match_id: String, server_id: String) -> bool:
	if not (base_url.begins_with("http://") or base_url.begins_with("https://")) or base_url.contains("\n") or base_url.contains("\r") or base_url.contains("?") or base_url.contains("#") or base_url.contains("@"):
		return false
	if workload_token.is_empty() or workload_token.contains("\n") or workload_token.contains("\r"):
		return false
	return AssignmentState.is_valid_opaque_id(match_id) and AssignmentState.is_valid_opaque_id(server_id)