extends Node2D

# The menu stacks whatever entries are actually available, rather than
# trusting the positions authored in the scene.
#
# Two of the three entries only exist when the game is run from Godot, so a
# shipped build shows one entry and an editor run shows three. There is no
# Quit: a web build has nothing to quit TO, and on Android the system back
# gesture already does it. Fixed
# offsets would leave holes where the hidden entries used to be - the same
# failure the HUD's button columns had, where a literal y meant "below the
# thing above me" and stopped being true when that thing moved. Here the
# stack is measured instead, and centred on whatever it ends up containing.

const ROW_BUTTON_HEIGHT: float = 128.0
const ROW_LABEL_OFFSET: float = 134.0
const ROW_LABEL_HEIGHT: float = 56.0
const ROW_HEIGHT: float = ROW_LABEL_OFFSET + ROW_LABEL_HEIGHT
const ROW_GAP: float = 20.0
const ROW_PITCH: float = ROW_HEIGHT + ROW_GAP
# The stack is centred on this rather than on the screen, to leave the title
# above it room to breathe.
const STACK_CENTER_Y: float = 40.0
const STATUS_GAP: float = 20.0
const STATUS_HEIGHT: float = 70.0

@onready var play_button: IconButton = $UI/PlayButton
@onready var play_label: Label = $UI/PlayLabel
@onready var editor_button: IconButton = $UI/EditorButton
@onready var editor_label: Label = $UI/EditorLabel
@onready var dev_button: IconButton = $UI/DevModeButton
@onready var dev_label: Label = $UI/DevModeLabel
@onready var status_label: Label = $UI/StatusLabel


func _ready() -> void:
	play_button.pressed.connect(_on_play_pressed)
	editor_button.pressed.connect(_on_editor_pressed)
	editor_button.enabled = true
	dev_button.pressed.connect(_on_dev_mode_pressed)
	dev_button.enabled = true

	# Dev mode and the map editor are development tools, not features of the
	# game: they are for building and play-testing it, and a player who
	# installed a build has no use for either. `editor` is the feature tag
	# Godot sets when running from the editor and clears in an export, which
	# is exactly the "started from Godot" distinction wanted here.
	var developing: bool = is_developer_build()
	editor_button.visible = developing
	editor_label.visible = developing
	dev_button.visible = developing
	dev_label.visible = developing

	_layout_stack()


# Wrapped so tests can state the rule they are checking rather than
# duplicating the feature-tag string.
func is_developer_build() -> bool:
	return OS.has_feature("editor")


func _layout_stack() -> void:
	var rows: Array = []
	for row in [[play_button, play_label], [editor_button, editor_label],
			[dev_button, dev_label]]:
		if row[0].visible:
			rows.append(row)
	if rows.is_empty():
		return

	# The last row carries no trailing gap, so the block is one pitch per row
	# minus that gap.
	var block_height: float = float(rows.size()) * ROW_PITCH - ROW_GAP
	var top: float = STACK_CENTER_Y - block_height * 0.5
	for row in rows:
		var button: Control = row[0]
		var label: Label = row[1]
		button.offset_top = top
		button.offset_bottom = top + ROW_BUTTON_HEIGHT
		label.offset_top = top + ROW_LABEL_OFFSET
		label.offset_bottom = top + ROW_LABEL_OFFSET + ROW_LABEL_HEIGHT
		top += ROW_PITCH

	# Status sits under the whole stack, where a message about any entry can
	# be read without it shifting the entries themselves.
	var status_top: float = top - ROW_GAP + STATUS_GAP
	status_label.offset_top = status_top
	status_label.offset_bottom = status_top + STATUS_HEIGHT


func _on_play_pressed() -> void:
	GameState.reset_new_game()
	_start("res://Main.tscn")


# "Nothing happens when I press Play" covers three different faults, and they
# are indistinguishable from the outside: the press never reaching this
# handler, the scene change refusing, or the scene change reporting success
# and not taking effect. Each writes a DIFFERENT line here, so one look at
# the screen says which one it is.
#
#   (nothing at all)          - the press never got here
#   "Loading Main.tscn..."    - it got here but the scene never finished
#                               loading
#   "Could not load ..."      - the load returned nothing
#   "Starting Main.tscn..."   - loaded and the change reported OK, yet the
#                               menu is somehow still up
#   "Could not start (...)"   - the change refused, with the error number
#
# The scene is also loaded HERE rather than left to change_scene_to_file(),
# which loads internally and reports a single error for both steps. Doing it
# in two makes the failure specific, and takes whatever that call does about
# background loading out of the picture - the web export is built without
# thread support, so anything expecting a loader thread is worth removing
# from the path rather than trusting.
func _start(scene_path: String) -> void:
	status_label.text = "Loading %s..." % scene_path.get_file()
	var packed: PackedScene = load(scene_path)
	if packed == null:
		status_label.text = "Could not load %s" % scene_path.get_file()
		return
	status_label.text = "Starting %s..." % scene_path.get_file()
	var result: int = get_tree().change_scene_to_packed(packed)
	if result != OK:
		status_label.text = "Could not start (%s, error %d)" % [scene_path.get_file(), result]


func _on_dev_mode_pressed() -> void:
	# Guarded as well as hidden. Visibility is presentation; this is the rule.
	if not is_developer_build():
		status_label.text = "Dev mode only runs from Godot"
		return
	GameState.start_dev_game()
	get_tree().change_scene_to_file("res://Main.tscn")


func _on_editor_pressed() -> void:
	if not is_developer_build():
		status_label.text = "Map editor only runs from Godot"
		return
	if editor_button.enabled:
		_start("res://PlanetSetupEditor.tscn")
		return
	status_label.text = "Map editor coming soon"