## ServerMain - Dedicated server root node.
## Accepts ENet connections, spawns Player nodes for each peer,
## and runs the simulation tick loop at 20 Hz.
extends Node


## Maximum number of concurrent players.
const MAX_PLAYERS := 16

## Server tick rate (Hz).
const TICK_RATE := 20

## Tick duration in seconds.
const TICK_DURATION := 1.0 / TICK_RATE

## ENet server port.
const SERVER_PORT := 7777

## Network peer used for ENet communication.
var network_peer: ENetMultiplayerPeer

## Map of peer_id -> Player node.
var players: Dictionary = {}

## Current tick counter (server-authoritative).
var tick: int = 0

## Whether the server is running.
var is_running: bool = false

## Accumulated real time for fixed timestep simulation.
var accumulator: float = 0.0

## Player scene resource (loaded once).
var _player_scene: PackedScene


func _ready() -> void:
	# Preload the player scene once.
	_player_scene = preload("res://scenes/player.tscn")

	# Create and assign the ENet server peer.
	network_peer = _create_server_peer()
	if network_peer:
		multiplayer.multiplayer_peer = network_peer
		is_running = true
		print("[Server] Started on port %d" % SERVER_PORT)
	else:
		printerr("[Server] Failed to create ENet peer.")
		get_tree().quit(1)


# ---------------------------------------------------------------------------
# Server creation
# ---------------------------------------------------------------------------

func _create_server_peer() -> ENetMultiplayerPeer:
	var peer := ENetMultiplayerPeer.new()
	var error := peer.create_server(SERVER_PORT, MAX_PLAYERS)
	if error != OK:
		printerr("[Server] create_server error: %d" % error)
		return null
	return peer


# ---------------------------------------------------------------------------
# Fixed-timestep simulation loop
# ---------------------------------------------------------------------------

func _process(delta: float) -> void:
	if not is_running:
		return

	# Fixed timestep accumulator.
	accumulator += delta
	while accumulator >= TICK_DURATION:
		accumulator -= TICK_DURATION
		_tick()


func _tick() -> void:
	"""Main server simulation tick (called at TICK_RATE)."""
	tick += 1

	# Process player inputs and update state.
	for peer_id in players:
		var player: Node3D = players[peer_id]
		if player and player.has_method("process_server_input"):
			player.process_server_input(tick)

	# Broadcast snapshot to all clients.
	_broadcast_snapshot()


func _broadcast_snapshot() -> void:
	"""Broadcast the current authoritative state to all connected clients."""
	var snapshot_data := {
		"tick": tick,
		"players": {},
	}

	for peer_id in players:
		var player: Node3D = players[peer_id]
		if player and player.has_method("get_server_state"):
			snapshot_data.players[peer_id] = player.get_server_state()

	# Send snapshot to all peers except the server itself (peer_id == 1).
	var peer_ids: Array = multiplayer.get_peers()
	for pid in peer_ids:
		if pid == 1:  # 1 is the server itself
			continue
		rpc_id(pid, "_receive_snapshot", snapshot_data)


# Remote: clients receive snapshots.
@rpc("any_peer", "call_remote", "reliable")
func _receive_snapshot(snapshot_data: Dictionary) -> void:
	pass  # Handled by client scene.


# ---------------------------------------------------------------------------
# Connection lifecycle
# ---------------------------------------------------------------------------

func _on_peer_connected(peer_id: int) -> void:
	print("[Server] Peer %d connected." % peer_id)

	if players.size() >= MAX_PLAYERS:
		print("[Server] Max players reached. Disconnecting peer %d." % peer_id)
		rpc_id(peer_id, "_kick", "Server is full.")
		return

	# Spawn a Player node for this peer.
	var player: Node3D = _player_scene.instantiate()
	player.name = "Player_%d" % peer_id
	player.peer_id = peer_id
	add_child(player)
	players[peer_id] = player

	print("[Server] Spawned player node for peer %d." % peer_id)


func _on_peer_disconnected(peer_id: int) -> void:
	print("[Server] Peer %d disconnected." % peer_id)
	if players.has(peer_id):
		var player: Node3D = players[peer_id]
		if player.is_inside_tree():
			player.queue_free()
		players.erase(peer_id)


# ---------------------------------------------------------------------------
# RPCs
# ---------------------------------------------------------------------------

@rpc("any_peer", "call_remote", "reliable")
func _kick(reason: String) -> void:
	print("[Server] Kicking caller: %s" % reason)
	rpc_id(multiplayer.get_remote_sender_id(), "_disconnect", reason)


@rpc("call_remote", "reliable")
func _disconnect(reason: String) -> void:
	print("[Server] Disconnecting: %s" % reason)
	get_tree().quit(0)


# ---------------------------------------------------------------------------
# Signal connections
# ---------------------------------------------------------------------------

func _enter_tree() -> void:
	multiplayer.peer_connected.connect(_on_peer_connected)
	multiplayer.peer_disconnected.connect(_on_peer_disconnected)