extends Node

const NetCodec = preload("res://scripts/net_codec.gd")

# Headless dedicated server entry point (task 1.6). Parses CLI args, hosts
# via NetworkManager, logs structured lines, and watches for physics-tick
# overrun (§9 gotcha 9: Engine.max_physics_steps_per_frame defaults to 8;
# a tick overrunning 16.7ms backs up the accumulator and the next frame
# runs multiple ticks, spiking CPU further — worth logging, not just
# silently absorbing).
#
# Run: godot --headless --path Game res://scenes/server_boot.tscn -- --port=7777
#
# Dedicated *exports* reach this scene without the CLI argument above, via the
# `run/main_scene.dedicated_server` feature override in project.godot — the same
# project-setting mechanism the training export uses for training.tscn. That
# override is deliberately uncommented in project.godot: Godot's ConfigFile
# writer does not round-trip comments, and a `#` block directly above a setting
# can be spliced into the setting's own line on rewrite, silently commenting it
# out and sending dedicated builds to the interactive main menu instead of here.
# `tests/cases/test_project_settings.gd` fails loudly if that ever happens.
#
# Deliberately does not spawn a match yet — that's Phase 2's networked_match
# scene. This is just the process shell: listen, log, idle cheaply.

var _last_physics_frame := 0
var config: ServerConfig = null
var _watchdog_armed := false   # skip the first _process(): engine startup scheduling can batch several physics frames before the first idle frame runs, which isn't a real overrun


func _ready() -> void:
	Engine.max_fps = 60   # a server never renders; this just caps the idle-frame poll rate so it doesn't spin

	# Task 6.3. This process owns the whole command line, so it parses STRICTLY:
	# an unknown flag or an out-of-range value stops the server with a message
	# rather than starting one that silently ignores half of what it was told.
	config = ServerConfig.parse(OS.get_cmdline_user_args())
	if config.help_requested:
		print(ServerConfig.help_text())
		get_tree().quit(0)
		return
	if not config.is_valid():
		# Straight to stderr-ish plain print rather than through _log: the log
		# level itself may be one of the things that failed to parse, and an
		# operator running this by hand needs to see every problem at once, not
		# the first one.
		printerr("cosmic-clash-server: refusing to start")
		for problem in config.errors:
			printerr("  %s" % problem)
		printerr("try --help")
		get_tree().quit(1)
		return
	ServerLog.configure(String(config.get_value("log-level")))
	var port := int(config.get_value("port"))
	var max_clients := int(config.get_value("max-clients"))
	var allocated_mode := bool(config.get_value("allocated-mode"))
	var assigned_transport := String(config.get_value("transport"))
	# Hosted SDR is not wired into the Godot transport layer yet. Refuse the
	# allocated launch rather than silently opening an ENet endpoint that does
	# not match the signed assignment's transport contract.
	if allocated_mode and assigned_transport != NetworkManager.TRANSPORT_ENET:
		printerr("cosmic-clash-server: allocated transport '%s' is not supported by this build" % assigned_transport)
		get_tree().quit(1)
		return
	if allocated_mode:
		var roster_file := String(config.get_value("join-authorisations-file"))
		var roster_json := FileAccess.get_file_as_string(roster_file)
		var roster_tokens = JSON.parse_string(roster_json)
		if not roster_tokens is Array or roster_tokens.is_empty() or not MatchNet.configure_join_authorisations(roster_tokens, {
			"match_id": String(config.get_value("match-id")),
			"server_id": String(config.get_value("server-id")),
			"protocol": str(NetCodec.PROTOCOL_VERSION),
			"protocol_version": NetCodec.PROTOCOL_VERSION,
		}):
			printerr("cosmic-clash-server: refusing to start with invalid join-authorisations-file")
			get_tree().quit(1)
			return

	NetworkManager.client_connected.connect(_on_client_connected)
	NetworkManager.client_disconnected.connect(_on_client_disconnected)
	MatchNet.player_joined.connect(_on_player_joined)
	MatchNet.player_left.connect(_on_player_left)

	var err := NetworkManager.host(port, max_clients)
	if err != OK:
		ServerLog.error("server_boot_failed", {"port": port, "error": error_string(err)})
		get_tree().quit(1)
		return
	_install_match_loop()
	ServerLog.info("server_started", {
		"port": port, "max_clients": max_clients, "log_level": ServerLog.level_name(),
		"min_players": int(config.get_value("min-players")),
		"max_matches": 1 if allocated_mode else int(config.get_value("max-matches")),
		"arena_rotation": String(config.get_value("arena-rotation")),
		"allocated_mode": allocated_mode,
		"match_id": String(config.get_value("match-id")) if allocated_mode else "",
		"server_id": String(config.get_value("server-id")) if allocated_mode else "",
		"region": String(config.get_value("region")) if allocated_mode else "",
		"transport": assigned_transport if allocated_mode else NetworkManager.TRANSPORT_ENET,
	})
	_last_physics_frame = Engine.get_physics_frames()


# Task 6.5. Parented to the ROOT rather than to this node: the loop calls
# change_scene_to_file, which frees the current scene — and this boot scene IS
# the current scene, so a loop parented here would be freed by the first match
# it started. Same constraint the smoke-test hooks document.
func _install_match_loop() -> void:
	var loop := ServerMatchLoop.new()
	loop.name = "ServerMatchLoop"
	loop.min_players = int(config.get_value("min-players"))
	loop.start_countdown_seconds = float(config.get_value("start-countdown"))
	loop.max_matches = 1 if bool(config.get_value("allocated-mode")) else int(config.get_value("max-matches"))
	loop.rotation_mode = String(config.get_value("arena-rotation"))
	get_tree().root.add_child.call_deferred(loop)


func _process(_delta: float) -> void:
	NetworkManager.poll()
	var current := Engine.get_physics_frames()
	var steps := current - _last_physics_frame
	_last_physics_frame = current
	# §9 gotcha 6: with physics_jitter_fix = 0.0, frames legitimately
	# alternate between 0 and 2 ticks even on an idle, healthy server —
	# that's expected quantisation, not backlog. A real overrun is the
	# accumulator failing to drain back down, i.e. 3+ ticks in one frame.
	if steps > 2 and _watchdog_armed:
		ServerLog.warn("physics_overrun", {"steps": steps})
	_watchdog_armed = true


func _physics_process(_delta: float) -> void:
	NetworkManager.poll()


func _on_client_connected(peer_id: int) -> void:
	ServerLog.debug("peer_connected", {"peer_id": peer_id})


func _on_client_disconnected(peer_id: int) -> void:
	ServerLog.debug("peer_disconnected", {"peer_id": peer_id})


func _on_player_joined(peer_id: int, player_name: String) -> void:
	ServerLog.info("player_joined", {"peer_id": peer_id, "name": player_name, "roster": MatchNet.roster.size()})


func _on_player_left(peer_id: int) -> void:
	ServerLog.info("player_left", {"peer_id": peer_id, "roster": MatchNet.roster.size()})