extends PanelContainer

const Style := preload("res://scripts/ui/ui_style.gd")
const Brand := preload("res://scripts/ui/medmind_style.gd")
const MAX_ENTRY_LENGTH := 16

var display_label: Label
var operation_label: Label
var keypad_buttons: Array[Button] = []
var entry := "0"
var accumulator := 0.0
var pending_operator := ""
var waiting_for_operand := true
var last_operator := ""
var last_operand := 0.0
var has_last_operation := false
var error_state := false
var drag_active := false
var drag_offset := Vector2.ZERO
var has_been_positioned := false


func _ready() -> void:
	name = "CalculatorPanel"
	visible = false
	top_level = true
	mouse_filter = Control.MOUSE_FILTER_STOP
	custom_minimum_size = Vector2(310, 390)
	size = custom_minimum_size
	_build_ui()
	if not get_viewport().size_changed.is_connected(_on_viewport_size_changed):
		get_viewport().size_changed.connect(_on_viewport_size_changed)
	_on_viewport_size_changed()
	refresh_theme_controls()
	_refresh_display()


func open_panel() -> void:
	visible = true
	move_to_front()
	if not has_been_positioned:
		var viewport_size := get_viewport_rect().size
		position = Vector2(maxf(12.0, viewport_size.x - size.x - 24.0), 72.0)
		has_been_positioned = true
	_clamp_to_viewport()


func close_panel() -> void:
	visible = false
	drag_active = false


func toggle_panel() -> void:
	if visible:
		close_panel()
	else:
		open_panel()


func reset_calculation() -> void:
	entry = "0"
	accumulator = 0.0
	pending_operator = ""
	waiting_for_operand = true
	last_operator = ""
	last_operand = 0.0
	has_last_operation = false
	error_state = false
	_refresh_display()


func press_token(token: String) -> void:
	if token.length() == 1 and token.is_valid_int():
		_enter_digit(token)
		return
	match token:
		".":
			_enter_decimal()
		"+", "−", "×", "÷":
			_set_operator(token)
		"=":
			_equals()
		"%":
			_apply_unary("percent")
		"√":
			_apply_unary("sqrt")
		"±":
			_apply_unary("sign")
		"⌫":
			_backspace()
		"AC":
			reset_calculation()


func get_display_text() -> String:
	return entry


func refresh_theme_controls() -> void:
	if display_label == null:
		return
	var dark := UIThemeService.is_dark_mode()
	add_theme_stylebox_override("panel", Brand.content_card_box(dark, true, Brand.ROYAL_BLUE))
	display_label.add_theme_color_override("font_color", Brand.text_color(dark))
	operation_label.add_theme_color_override("font_color", Brand.muted_color(dark))
	for button in keypad_buttons:
		var accent := Brand.ROYAL_BLUE if str(button.get_meta("calculator_token", "")) in ["+", "−", "×", "÷", "="] else Brand.SLATE
		button.add_theme_stylebox_override("normal", Brand.badge_box(dark, accent))
		button.add_theme_stylebox_override("hover", Brand.badge_box(dark, Brand.TEAL))
		button.add_theme_stylebox_override("pressed", Brand.badge_box(dark, Brand.PURPLE))
		button.add_theme_color_override("font_color", Brand.text_color(dark))


func _build_ui() -> void:
	var margin := MarginContainer.new()
	margin.add_theme_constant_override("margin_left", 10)
	margin.add_theme_constant_override("margin_right", 10)
	margin.add_theme_constant_override("margin_top", 12)
	margin.add_theme_constant_override("margin_bottom", 14)
	add_child(margin)

	var content := VBoxContainer.new()
	content.add_theme_constant_override("separation", 10)
	margin.add_child(content)

	var title_bar := HBoxContainer.new()
	title_bar.name = "CalculatorTitleBar"
	title_bar.mouse_filter = Control.MOUSE_FILTER_STOP
	title_bar.custom_minimum_size.y = 34
	title_bar.gui_input.connect(_on_title_bar_gui_input)
	content.add_child(title_bar)

	var title := Label.new()
	title.text = "Calculator"
	title.size_flags_horizontal = Control.SIZE_EXPAND_FILL
	title.mouse_filter = Control.MOUSE_FILTER_IGNORE
	Brand.apply_font(title)
	title.add_theme_font_size_override("font_size", 18)
	title_bar.add_child(title)

	var close := Button.new()
	close.name = "CalculatorClose"
	close.text = "×"
	close.tooltip_text = "Close calculator"
	close.custom_minimum_size = Vector2(36, 32)
	close.focus_mode = Control.FOCUS_NONE
	close.pressed.connect(close_panel)
	title_bar.add_child(close)

	var display_panel := PanelContainer.new()
	display_panel.custom_minimum_size.y = 78
	display_panel.add_theme_stylebox_override("panel", Style.panel_box(Color("101b31"), Style.CYAN))
	content.add_child(display_panel)

	var display_margin := MarginContainer.new()
	display_margin.add_theme_constant_override("margin_left", 12)
	display_margin.add_theme_constant_override("margin_right", 12)
	display_margin.add_theme_constant_override("margin_top", 8)
	display_margin.add_theme_constant_override("margin_bottom", 8)
	display_panel.add_child(display_margin)

	var display_stack := VBoxContainer.new()
	display_margin.add_child(display_stack)
	operation_label = Label.new()
	operation_label.name = "CalculatorOperation"
	operation_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_RIGHT
	operation_label.add_theme_font_size_override("font_size", 13)
	Brand.apply_font(operation_label)
	display_stack.add_child(operation_label)
	display_label = Label.new()
	display_label.name = "CalculatorDisplay"
	display_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_RIGHT
	display_label.text_overrun_behavior = TextServer.OVERRUN_TRIM_ELLIPSIS
	display_label.add_theme_font_size_override("font_size", 28)
	Brand.apply_font(display_label)
	display_stack.add_child(display_label)

	var keypad := GridContainer.new()
	keypad.name = "CalculatorKeypad"
	keypad.columns = 4
	keypad.add_theme_constant_override("h_separation", 6)
	keypad.add_theme_constant_override("v_separation", 8)
	content.add_child(keypad)

	var tokens := [
		"AC", "⌫", "±", "√",
		"7", "8", "9", "÷",
		"4", "5", "6", "×",
		"1", "2", "3", "−",
		"%", "0", ".", "+",
		"", "", "", "="
	]
	for token in tokens:
		var button := Button.new()
		button.custom_minimum_size = Vector2(44, 45)
		button.size_flags_horizontal = Control.SIZE_EXPAND_FILL
		button.focus_mode = Control.FOCUS_NONE
		if token == "":
			button.visible = false
			keypad.add_child(button)
			continue
		button.text = token
		button.set_meta("calculator_token", token)
		button.tooltip_text = _token_tooltip(token)
		button.add_theme_font_size_override("font_size", 18)
		Brand.apply_font(button)
		UISoundService.set_button_sound(button, "toggle")
		button.pressed.connect(press_token.bind(token))
		keypad.add_child(button)
		keypad_buttons.append(button)


func _input(event: InputEvent) -> void:
	if not visible or not (event is InputEventKey):
		return
	var key_event := event as InputEventKey
	if not key_event.pressed or key_event.echo:
		return
	var token := ""
	if key_event.keycode == KEY_ESCAPE:
		close_panel()
		get_viewport().set_input_as_handled()
		return
	if key_event.keycode in [KEY_ENTER, KEY_KP_ENTER]:
		token = "="
	elif key_event.keycode == KEY_BACKSPACE:
		token = "⌫"
	elif key_event.keycode == KEY_DELETE:
		token = "AC"
	elif key_event.unicode > 0:
		var character := String.chr(key_event.unicode)
		match character:
			"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", ".", "%", "=":
				token = character
			"+": token = "+"
			"-": token = "−"
			"*", "x", "X": token = "×"
			"/": token = "÷"
			"c", "C": token = "AC"
	if token == "":
		return
	press_token(token)
	get_viewport().set_input_as_handled()


func _enter_digit(digit: String) -> void:
	if error_state:
		reset_calculation()
	if waiting_for_operand:
		entry = digit
		waiting_for_operand = false
	elif entry == "0":
		entry = digit
	elif entry.length() < MAX_ENTRY_LENGTH:
		entry += digit
	_refresh_display()


func _enter_decimal() -> void:
	if error_state:
		reset_calculation()
	if waiting_for_operand:
		entry = "0."
		waiting_for_operand = false
	elif not "." in entry and entry.length() < MAX_ENTRY_LENGTH:
		entry += "."
	_refresh_display()


func _set_operator(operator: String) -> void:
	if error_state:
		return
	var current := _entry_value()
	if pending_operator != "" and not waiting_for_operand:
		if not _perform_operation(pending_operator, current):
			return
	else:
		accumulator = current
	pending_operator = operator
	waiting_for_operand = true
	has_last_operation = false
	_refresh_display()


func _equals() -> void:
	if error_state:
		return
	if pending_operator != "":
		var operand := accumulator if waiting_for_operand else _entry_value()
		var operator := pending_operator
		if not _perform_operation(operator, operand):
			return
		last_operator = operator
		last_operand = operand
		has_last_operation = true
		pending_operator = ""
	elif has_last_operation:
		if not _perform_operation(last_operator, last_operand):
			return
	else:
		return
	waiting_for_operand = true
	_refresh_display()


func _apply_unary(operation: String) -> void:
	if error_state:
		return
	var value := _entry_value()
	match operation:
		"percent":
			value /= 100.0
		"sqrt":
			if value < 0.0:
				_set_error()
				return
			value = sqrt(value)
		"sign":
			value = -value
	entry = _format_number(value)
	if pending_operator == "":
		accumulator = value
	waiting_for_operand = false
	_refresh_display()


func _backspace() -> void:
	if error_state:
		reset_calculation()
		return
	if waiting_for_operand:
		return
	entry = entry.left(entry.length() - 1)
	if entry in ["", "-"]:
		entry = "0"
		waiting_for_operand = true
	_refresh_display()


func _perform_operation(operator: String, operand: float) -> bool:
	var result := accumulator
	match operator:
		"+": result += operand
		"−": result -= operand
		"×": result *= operand
		"÷":
			if is_zero_approx(operand):
				_set_error()
				return false
			result /= operand
	if is_nan(result) or is_inf(result):
		_set_error()
		return false
	accumulator = result
	entry = _format_number(result)
	return true


func _entry_value() -> float:
	return entry.to_float()


func _format_number(value: float) -> String:
	if is_zero_approx(value):
		return "0"
	var formatted := String.num(value, 12)
	if "." in formatted:
		while formatted.ends_with("0"):
			formatted = formatted.left(formatted.length() - 1)
		if formatted.ends_with("."):
			formatted = formatted.left(formatted.length() - 1)
	if formatted.length() > MAX_ENTRY_LENGTH:
		formatted = String.num_scientific(value).replace("e+", "e")
	return formatted


func _set_error() -> void:
	entry = "Error"
	error_state = true
	pending_operator = ""
	waiting_for_operand = true
	has_last_operation = false
	_refresh_display()


func _refresh_display() -> void:
	if display_label == null:
		return
	display_label.text = entry
	operation_label.text = ("%s %s" % [_format_number(accumulator), pending_operator]) if pending_operator != "" else ""


func _on_title_bar_gui_input(event: InputEvent) -> void:
	var touch_event := event as InputEventScreenTouch
	if touch_event != null:
		drag_active = touch_event.pressed
		if drag_active:
			drag_offset = touch_event.position
		get_viewport().set_input_as_handled()
		return
	var touch_drag := event as InputEventScreenDrag
	if touch_drag != null and drag_active:
		global_position += touch_drag.relative
		_clamp_to_viewport()
		get_viewport().set_input_as_handled()
		return
	var mouse_event := event as InputEventMouseButton
	if mouse_event != null and mouse_event.button_index == MOUSE_BUTTON_LEFT:
		drag_active = mouse_event.pressed
		if drag_active:
			drag_offset = mouse_event.global_position - global_position
		get_viewport().set_input_as_handled()
		return
	var motion := event as InputEventMouseMotion
	if motion != null and drag_active:
		global_position = motion.global_position - drag_offset
		_clamp_to_viewport()
		get_viewport().set_input_as_handled()


func _on_viewport_size_changed() -> void:
	var viewport_size := get_viewport_rect().size
	custom_minimum_size.x = minf(310.0, maxf(216.0, viewport_size.x - 24.0))
	size.x = custom_minimum_size.x
	_clamp_to_viewport()


func _clamp_to_viewport() -> void:
	if not is_inside_tree():
		return
	var viewport_size := get_viewport_rect().size
	position.x = clampf(position.x, 12.0, maxf(12.0, viewport_size.x - size.x - 12.0))
	position.y = clampf(position.y, 12.0, maxf(12.0, viewport_size.y - size.y - 12.0))


func _token_tooltip(token: String) -> String:
	return {
		"AC": "Clear calculation",
		"⌫": "Backspace",
		"±": "Change sign",
		"√": "Square root",
		"%": "Convert to percent",
		"÷": "Divide",
		"×": "Multiply",
		"−": "Subtract",
		"+": "Add",
		"=": "Equals"
	}.get(token, token)