class_name Settings
extends RefCounted
## Player preferences: key bindings and volumes.
##
## Client-side and local. Nothing here reaches the server or the simulation --
## which key you press to fire is not something the server has an opinion about,
## and the input frame it eventually produces looks identical either way.
##
## Static rather than an autoload for the same reason [GameOpts] is: a `--script`
## tool has no main loop and cannot resolve autoload names, and the settings
## file is something a headless test may well want to read.

const DEFAULT_PATH := "user://settings.cfg"

## Where preferences are read from and written to. A variable rather than a
## constant so tests can point it at a scratch file: rebinding calls save(),
## and a suite run was otherwise rewriting the player's real settings -- which
## it did, silently, until a screenshot showed Fire bound to the right mouse
## button.
static var path: String = DEFAULT_PATH

## Actions the settings screen offers, in the order it lists them. Anything not
## here keeps whatever `tools/setup_input_map.gd` gave it and cannot be changed
## -- which is the right default for a binding nobody should be reassigning.
const REBINDABLE: Array = [
	["move_up", "Move up"],
	["move_down", "Move down"],
	["move_left", "Move left"],
	["move_right", "Move right"],
	["fire", "Fire"],
	["interact", "Interact / pick up"],
	["emergency_escape", "Emergency escape"],
	["use_slot_1", "Use slot 1"],
	["use_slot_2", "Use slot 2"],
	["use_slot_3", "Use slot 3"],
	["use_slot_4", "Use slot 4"],
	["system_menu", "Menu"],
	["debug_overlay", "Hitbox overlay"],
]

## Bus every sound effect plays on. Created at runtime rather than shipped as a
## bus layout resource, so there is one fewer file to keep in step with the code
## that reads it.
const SFX_BUS := "SFX"

static var master_volume: float = 0.8
static var sfx_volume: float = 0.8
## action -> a serialisable description of its event. See _describe().
static var bindings: Dictionary[String, Dictionary] = {}

## What the project shipped, captured before anything is overridden. Without it
## "reset to defaults" would restore whatever the last session happened to save.
static var _defaults: Dictionary[String, Dictionary] = {}
static var _defaults_captured: bool = false


# --- Lifecycle ---------------------------------------------------------------

## Read the file and apply everything. Safe to call with no file present, which
## is every first run.
static func load_and_apply() -> void:
	_capture_defaults()
	var cfg := ConfigFile.new()
	if cfg.load(path) == OK:
		master_volume = clampf(float(cfg.get_value("audio", "master", master_volume)), 0.0, 1.0)
		sfx_volume = clampf(float(cfg.get_value("audio", "sfx", sfx_volume)), 0.0, 1.0)
		bindings.clear()
		for action in REBINDABLE:
			var key := String(action[0])
			# has_section_key first: passing null as the default to get_value()
			# does NOT mean "no default", it means the key is absent AND no
			# default was given, and the engine logs an error for every missing
			# one. A settings file written before an action existed is normal.
			if not cfg.has_section_key("input", key):
				continue
			var stored: Variant = cfg.get_value("input", key)
			# A binding this build cannot make sense of is dropped, not
			# guessed at: an unusable control is worse than the default one.
			if typeof(stored) == TYPE_DICTIONARY and _event_from(stored) != null:
				bindings[key] = stored
	apply_audio()
	apply_input()


static func save() -> void:
	var cfg := ConfigFile.new()
	cfg.set_value("audio", "master", master_volume)
	cfg.set_value("audio", "sfx", sfx_volume)
	for action in bindings:
		cfg.set_value("input", action, bindings[action])
	var err := cfg.save(path)
	if err != OK:
		GameLog.warn("settings", "could not write %s (error %d)" % [path, err])


# --- Audio -------------------------------------------------------------------

## Ensure the SFX bus exists and push both volumes onto the mixer.
static func apply_audio() -> void:
	var sfx := AudioServer.get_bus_index(SFX_BUS)
	if sfx < 0:
		AudioServer.add_bus()
		sfx = AudioServer.bus_count - 1
		AudioServer.set_bus_name(sfx, SFX_BUS)
		AudioServer.set_bus_send(sfx, "Master")
	AudioServer.set_bus_volume_db(0, linear_to_db_clamped(master_volume))
	AudioServer.set_bus_mute(0, master_volume <= 0.0)
	AudioServer.set_bus_volume_db(sfx, linear_to_db_clamped(sfx_volume))
	AudioServer.set_bus_mute(sfx, sfx_volume <= 0.0)


## Godot's linear_to_db(0) is -inf, which serialises badly and reads as a bug
## when it turns up in a log. The clamp is what prevents that -- 0.0001 comes
## out at exactly -80dB, far below audible -- so a zero or a negative from a
## corrupt settings file lands there rather than at negative infinity. Actual
## silence is the bus mute flag, set alongside this.
static func linear_to_db_clamped(linear: float) -> float:
	return linear_to_db(clampf(linear, 0.0001, 1.0))


# --- Input -------------------------------------------------------------------

## Snapshot the project's own bindings. Called before anything overrides them,
## and only once -- a second call after an override would capture the override.
static func _capture_defaults() -> void:
	if _defaults_captured:
		return
	_defaults_captured = true
	for entry in REBINDABLE:
		var action := String(entry[0])
		if not InputMap.has_action(action):
			continue
		var events := InputMap.action_get_events(action)
		if not events.is_empty():
			_defaults[action] = _describe(events[0])


## Rewrite the InputMap from [member bindings]. Actions with no override are
## restored to what the project shipped, so clearing one binding cannot leave a
## previous session's choice behind.
static func apply_input() -> void:
	_capture_defaults()
	for entry in REBINDABLE:
		var action := String(entry[0])
		if not InputMap.has_action(action):
			continue
		var described: Dictionary = bindings.get(action, _defaults.get(action, {}))
		var event := _event_from(described)
		if event == null:
			continue
		# Replacing every event rather than the first: an action that kept its
		# alternates would still answer to the key the player just moved away
		# from, which reads as the rebind not having worked.
		InputMap.action_erase_events(action)
		InputMap.action_add_event(action, event)


## Assign [param event] to [param action]. Returns the action it collided with,
## or an empty string on success -- one key doing two things is a broken
## control scheme, so it is refused rather than silently accepted.
static func rebind(action: String, event: InputEvent) -> String:
	var described := _describe(event)
	if described.is_empty():
		return action
	for entry in REBINDABLE:
		var other := String(entry[0])
		if other == action:
			continue
		if current_binding(other) == described:
			return other
	bindings[action] = described
	apply_input()
	save()
	return ""


static func reset_bindings() -> void:
	bindings.clear()
	apply_input()
	save()


## What [param action] is bound to right now: the override if there is one,
## otherwise what the project shipped.
static func current_binding(action: String) -> Dictionary:
	_capture_defaults()
	return bindings.get(action, _defaults.get(action, {}))


static func binding_label(action: String) -> String:
	return describe_label(current_binding(action))


static func describe_label(described: Dictionary) -> String:
	match String(described.get("type", "")):
		"key":
			var code := int(described.get("code", 0))
			# 0 is not a key. _event_from refuses to build one, so a stored 0
			# never reaches the input map -- but it would render as a blank
			# button, which looks like a bound key with no name.
			if code == 0:
				return "unbound"
			return OS.get_keycode_string(_layout_keycode(code))
		"mouse":
			match int(described.get("code", 0)):
				MOUSE_BUTTON_LEFT: return "Mouse Left"
				MOUSE_BUTTON_RIGHT: return "Mouse Right"
				MOUSE_BUTTON_MIDDLE: return "Mouse Middle"
			return "Mouse %d" % int(described["code"])
	return "unbound"


## Bindings are stored as PHYSICAL keycodes, so they follow key position rather
## than layout -- the same choice tools/setup_input_map.gd makes. The label is
## translated back through the active layout so an AZERTY player reads "A" for
## the key their fingers are on, rather than the QWERTY name of that position.
##
## The translation is skipped on a display server that has no keyboard, which
## is headless: the call is not merely unsupported there, it pushes an engine
## error and hands the argument straight back, so asking is worse than not.
## There is no feature flag to test for it.
static func _layout_keycode(physical: int) -> int:
	if physical == 0 or DisplayServer.get_name() == "headless":
		return physical
	return DisplayServer.keyboard_get_keycode_from_physical(physical)


## Only keys and mouse buttons are accepted. A rebind listener that took any
## InputEvent would happily capture mouse MOTION the instant the player moved
## the mouse, which is not a binding anyone meant to make.
static func is_bindable(event: InputEvent) -> bool:
	return not _describe(event).is_empty()


static func _describe(event: InputEvent) -> Dictionary:
	if event is InputEventKey:
		var key := event as InputEventKey
		var code := key.physical_keycode if key.physical_keycode != 0 else key.keycode
		if code == 0:
			return {}
		return {"type": "key", "code": int(code)}
	if event is InputEventMouseButton:
		return {"type": "mouse", "code": int((event as InputEventMouseButton).button_index)}
	return {}


static func _event_from(described: Dictionary) -> InputEvent:
	match String(described.get("type", "")):
		"key":
			var k := InputEventKey.new()
			# device -1 is the only value that matches input from a real
			# device; a freshly constructed event defaults to 16, which
			# silently matches nothing. See tools/setup_input_map.gd.
			k.device = -1
			k.physical_keycode = int(described.get("code", 0))
			return k if k.physical_keycode != 0 else null
		"mouse":
			var m := InputEventMouseButton.new()
			m.device = -1
			m.button_index = int(described.get("code", 0))
			return m if m.button_index != 0 else null
	return null