step3/scripts/ui/flashcards_study.gd

extends Control

const Brand := preload("res://scripts/ui/medmind_style.gd")
const Style := preload("res://scripts/ui/ui_style.gd")
const Cloze := preload("res://scripts/ui/flashcard_cloze.gd")
const CircularProgress := preload("res://scripts/ui/circular_progress.gd")

const MASTERY_STABILITY_LABEL := "Cards graduate to \"mastered\" once they've held up in review for a few weeks straight."
const PROGRESS_PIP_COUNT := 5

var main

var deck_id := ""
var current_note: Dictionary = {}
var current_card: Dictionary = {}
var rating_options: Array = []
var revealed := false
var last_client_review_id := ""
var last_card_id := ""
var study_day_start_utc := ""
var seen_card_ids: Array = []
var reveal_started_ms := 0
var loaded_started_ms := 0
var awaiting_next := false
var due_remaining := 0
var new_remaining := 0

# Session history: every card that leaves the "live" slot (graded, skipped, buried, or
# suspended) is pushed here, so Previous/Next can page back through what happened this session.
# Invariant: history_cursor == session_history.size() means "at the live card"; anything less
# means we're viewing a past entry in read-only mode.
var session_history: Array = []
var history_cursor := 0
var session_total := -1
var shuffle_enabled := false

# Shadow copy of the true in-flight card, populated only while browsing history so the live
# card is never lost and can be restored exactly via _return_to_live().
var live_note: Dictionary = {}
var live_card: Dictionary = {}
var live_rating_options: Array = []
var live_revealed := false
var live_due_remaining := 0
var live_new_remaining := 0

var progress_label: Label
var progress_pips: Array = []
var paused_banner: Label
var main_row: HBoxContainer
var card_panel: PanelContainer
var front_label: Label
var divider: ColorRect
var answer_caption: Label
var back_label: Label
var extra_caption: Label
var extra_label: Label
var card_position_label: Label
var reveal_button: Button
var grade_row: HBoxContainer
var grade_buttons: Dictionary = {}
var undo_button: Button
var previous_button: Button
var next_button: Button
var shuffle_button: Button
var options_button: Button
var options_menu: PanelContainer
var options_backdrop: Control
var options_bury_button: Button
var options_suspend_button: Button
var empty_label: Label
var compact_layout := false

var deck_panel: PanelContainer
var deck_name_label: Label
var deck_system_badge: Label
var deck_ring: Control
var deck_mastered_label: Label
var change_deck_button: Button

var stats_panel: PanelContainer
var stats_new_ring: Control
var stats_due_label: Label
var stats_learning_label: Label
var stats_review_label: Label
var streak_label: Label
var daily_goal_label: Label
var daily_goal_bar: ProgressBar

var decks: Array = []
var latest_counts: Dictionary = {}


func _ready() -> void:
	set_anchors_and_offsets_preset(Control.PRESET_FULL_RECT)
	add_theme_constant_override("separation", 14)
	_build()
	resized.connect(_update_responsive_layout)
	call_deferred("_update_responsive_layout")
	FlashcardService.next_card_loaded.connect(_on_next_card_loaded)
	FlashcardService.next_card_failed.connect(_on_next_card_failed)
	FlashcardService.review_synced.connect(_on_review_synced)
	FlashcardService.review_paused.connect(_on_review_paused)
	FlashcardService.review_resumed.connect(_on_review_resumed)
	FlashcardService.decks_changed.connect(_on_decks_changed)
	FlashcardService.counts_changed.connect(_on_counts_changed)
	UIThemeService.theme_changed.connect(func(_dark: bool): refresh_theme_controls())


func on_show(payload: Variant = null) -> void:
	deck_id = str(payload) if payload != null else ""
	seen_card_ids.clear()
	session_history.clear()
	history_cursor = 0
	session_total = -1
	study_day_start_utc = FlashcardService.current_study_day_start_utc()
	current_note = {}
	current_card = {}
	revealed = false
	last_client_review_id = ""
	last_card_id = ""
	undo_button.visible = false
	_close_options_menu()
	_render_loading()
	_update_footer_button_states()
	_load_next()
	FlashcardService.fetch_decks()
	FlashcardService.fetch_counts()


func on_hide() -> void:
	pass


func _build() -> void:
	var root := VBoxContainer.new()
	root.set_anchors_and_offsets_preset(Control.PRESET_FULL_RECT)
	root.add_theme_constant_override("separation", 16)
	add_child(root)

	var top_row := HBoxContainer.new()
	root.add_child(top_row)
	progress_label = Label.new()
	progress_label.size_flags_horizontal = Control.SIZE_EXPAND_FILL
	progress_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
	progress_label.add_theme_font_size_override("font_size", 15)
	top_row.add_child(progress_label)

	var pips_row := HBoxContainer.new()
	pips_row.alignment = BoxContainer.ALIGNMENT_CENTER
	pips_row.add_theme_constant_override("separation", 6)
	root.add_child(pips_row)
	progress_pips = []
	for i in PROGRESS_PIP_COUNT:
		var pip := PanelContainer.new()
		pip.custom_minimum_size = Vector2(48, 6)
		pips_row.add_child(pip)
		progress_pips.append(pip)

	paused_banner = Label.new()
	paused_banner.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
	paused_banner.add_theme_color_override("font_color", Style.AMBER)
	paused_banner.visible = false
	root.add_child(paused_banner)

	main_row = HBoxContainer.new()
	main_row.size_flags_vertical = Control.SIZE_EXPAND_FILL
	main_row.size_flags_horizontal = Control.SIZE_EXPAND_FILL
	main_row.add_theme_constant_override("separation", 20)
	root.add_child(main_row)

	_build_deck_panel()

	var center_column := VBoxContainer.new()
	center_column.size_flags_horizontal = Control.SIZE_EXPAND_FILL
	center_column.size_flags_vertical = Control.SIZE_EXPAND_FILL
	center_column.add_theme_constant_override("separation", 16)
	main_row.add_child(center_column)

	var center := CenterContainer.new()
	center.size_flags_vertical = Control.SIZE_EXPAND_FILL
	center.size_flags_horizontal = Control.SIZE_EXPAND_FILL
	center_column.add_child(center)

	card_panel = PanelContainer.new()
	card_panel.custom_minimum_size = Vector2(720, 420)
	card_panel.add_theme_stylebox_override("panel", Brand.content_card_box(UIThemeService.is_dark_mode(), true, Brand.ROYAL_BLUE))
	center.add_child(card_panel)
	var card_content := VBoxContainer.new()
	card_content.add_theme_constant_override("separation", 20)
	card_panel.add_child(card_content)

	empty_label = Label.new()
	empty_label.text = "Nothing due right now. Great work!"
	empty_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
	empty_label.visible = false
	card_content.add_child(empty_label)

	front_label = Label.new()
	front_label.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
	front_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
	front_label.add_theme_font_size_override("font_size", 25)
	card_content.add_child(front_label)

	divider = ColorRect.new()
	divider.custom_minimum_size = Vector2(0, 2)
	divider.visible = false
	card_content.add_child(divider)

	var answer_block := VBoxContainer.new()
	answer_block.add_theme_constant_override("separation", 4)
	card_content.add_child(answer_block)
	answer_caption = _caption_label("ANSWER")
	answer_block.add_child(answer_caption)
	back_label = Label.new()
	back_label.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
	back_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
	back_label.add_theme_font_size_override("font_size", 19)
	back_label.visible = false
	answer_block.add_child(back_label)

	var extra_block := VBoxContainer.new()
	extra_block.add_theme_constant_override("separation", 4)
	card_content.add_child(extra_block)
	extra_caption = _caption_label("KEY TAKEAWAY")
	extra_block.add_child(extra_caption)
	extra_label = Label.new()
	extra_label.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
	extra_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
	extra_label.add_theme_font_size_override("font_size", 15)
	extra_label.visible = false
	extra_block.add_child(extra_label)

	var position_row := HBoxContainer.new()
	card_content.add_child(position_row)
	var position_spacer := Control.new()
	position_spacer.size_flags_horizontal = Control.SIZE_EXPAND_FILL
	position_row.add_child(position_spacer)
	card_position_label = Label.new()
	card_position_label.add_theme_font_size_override("font_size", 12)
	card_position_label.visible = false
	position_row.add_child(card_position_label)

	reveal_button = Button.new()
	reveal_button.text = "Show Answer  (Space)"
	reveal_button.custom_minimum_size = Vector2(0, 52)
	_style_gradient_button(reveal_button)
	reveal_button.pressed.connect(_reveal)
	center_column.add_child(reveal_button)

	grade_row = HBoxContainer.new()
	grade_row.add_theme_constant_override("separation", 10)
	grade_row.visible = false
	center_column.add_child(grade_row)
	for spec in [["again", "Again", "1", Style.RED], ["hard", "Hard", "2", Style.AMBER], ["good", "Good", "3", Style.CYAN], ["easy", "Easy", "4", Style.LIME]]:
		var button := Button.new()
		button.custom_minimum_size = Vector2(0, 64)
		button.size_flags_horizontal = Control.SIZE_EXPAND_FILL
		Style.style_chip(button, spec[3])
		button.pressed.connect(_grade.bind(spec[0]))
		grade_row.add_child(button)
		grade_buttons[spec[0]] = button

	undo_button = Button.new()
	undo_button.text = "Undo this rating"
	undo_button.custom_minimum_size = Vector2(0, 40)
	undo_button.visible = false
	undo_button.pressed.connect(_undo)
	center_column.add_child(undo_button)

	var footer_center := CenterContainer.new()
	center_column.add_child(footer_center)
	var footer_row := HBoxContainer.new()
	footer_row.add_theme_constant_override("separation", 10)
	footer_center.add_child(footer_row)

	previous_button = Button.new()
	previous_button.text = "‹ Previous"
	previous_button.custom_minimum_size = Vector2(120, 44)
	previous_button.pressed.connect(_go_previous)
	footer_row.add_child(previous_button)

	shuffle_button = Button.new()
	shuffle_button.text = "Shuffle"
	shuffle_button.toggle_mode = true
	shuffle_button.custom_minimum_size = Vector2(110, 44)
	shuffle_button.toggled.connect(func(pressed: bool): shuffle_enabled = pressed)
	footer_row.add_child(shuffle_button)

	_build_options_menu(footer_row)

	next_button = Button.new()
	next_button.text = "Next ›"
	next_button.custom_minimum_size = Vector2(120, 44)
	next_button.pressed.connect(_go_next)
	footer_row.add_child(next_button)

	_build_stats_panel()

	refresh_theme_controls()
	_update_footer_button_states()


func _caption_label(text: String) -> Label:
	var label := Label.new()
	label.text = text
	label.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
	label.add_theme_font_size_override("font_size", 12)
	label.visible = false
	return label


func _style_gradient_button(button: Button) -> void:
	button.add_theme_stylebox_override("normal", Brand.gradient_button_box())
	button.add_theme_stylebox_override("hover", Brand.gradient_button_box())
	button.add_theme_stylebox_override("pressed", Brand.gradient_button_box())
	button.add_theme_color_override("font_color", Color.WHITE)
	button.add_theme_color_override("font_hover_color", Color.WHITE)


func _style_ghost_button(button: Button, dark: bool) -> void:
	var empty := StyleBoxEmpty.new()
	button.add_theme_stylebox_override("normal", empty)
	button.add_theme_stylebox_override("hover", empty)
	button.add_theme_stylebox_override("pressed", empty)
	button.add_theme_stylebox_override("focus", empty)
	button.add_theme_color_override("font_color", Brand.muted_color(dark))
	button.add_theme_color_override("font_hover_color", Brand.text_color(dark))


func _side_panel_box(dark: bool) -> StyleBoxFlat:
	var box := StyleBoxFlat.new()
	box.bg_color = Color("081426") if dark else Color.WHITE
	box.border_color = Color("26344f") if dark else Brand.LIGHT_BORDER
	box.set_border_width_all(1)
	box.set_corner_radius_all(10)
	box.content_margin_left = 18
	box.content_margin_right = 18
	box.content_margin_top = 18
	box.content_margin_bottom = 18
	return box


func _pip_box(filled: bool, dark: bool) -> StyleBoxFlat:
	var box := StyleBoxFlat.new()
	box.bg_color = Brand.ROYAL_BLUE if filled else (Color("26324a") if dark else Color("e2e8f0"))
	box.set_corner_radius_all(3)
	return box


func _panel_caption(text: String) -> Label:
	var label := Label.new()
	label.text = text
	label.add_theme_font_size_override("font_size", 12)
	return label


# ---------- Left panel: current deck ----------

func _build_deck_panel() -> void:
	deck_panel = PanelContainer.new()
	deck_panel.custom_minimum_size = Vector2(220, 0)
	deck_panel.size_flags_vertical = Control.SIZE_SHRINK_BEGIN
	main_row.add_child(deck_panel)
	var content := VBoxContainer.new()
	content.add_theme_constant_override("separation", 10)
	deck_panel.add_child(content)

	content.add_child(_panel_caption("CURRENT DECK"))
	deck_name_label = Label.new()
	deck_name_label.text = "All decks"
	deck_name_label.add_theme_font_size_override("font_size", 18)
	deck_name_label.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
	content.add_child(deck_name_label)

	deck_system_badge = Label.new()
	deck_system_badge.text = "Official Deck"
	deck_system_badge.add_theme_font_size_override("font_size", 12)
	deck_system_badge.add_theme_color_override("font_color", Brand.PURPLE)
	deck_system_badge.visible = false
	content.add_child(deck_system_badge)

	var ring_center := CenterContainer.new()
	content.add_child(ring_center)
	deck_ring = CircularProgress.new()
	deck_ring.tooltip_text = MASTERY_STABILITY_LABEL
	ring_center.add_child(deck_ring)

	deck_mastered_label = Label.new()
	deck_mastered_label.text = "-- cards mastered"
	deck_mastered_label.add_theme_font_size_override("font_size", 12)
	deck_mastered_label.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
	content.add_child(deck_mastered_label)

	change_deck_button = Button.new()
	change_deck_button.text = "Change Deck"
	change_deck_button.custom_minimum_size = Vector2(0, 44)
	change_deck_button.pressed.connect(func(): main.show_screen("flashcards_hub"))
	content.add_child(change_deck_button)


# ---------- Right panel: spaced repetition stats ----------

func _build_stats_panel() -> void:
	stats_panel = PanelContainer.new()
	stats_panel.custom_minimum_size = Vector2(220, 0)
	stats_panel.size_flags_vertical = Control.SIZE_SHRINK_BEGIN
	main_row.add_child(stats_panel)
	var content := VBoxContainer.new()
	content.add_theme_constant_override("separation", 10)
	stats_panel.add_child(content)

	content.add_child(_panel_caption("SPACED REPETITION"))

	var ring_center := CenterContainer.new()
	content.add_child(ring_center)
	stats_new_ring = CircularProgress.new()
	ring_center.add_child(stats_new_ring)

	stats_due_label = _stat_row(content, "Due")
	stats_learning_label = _stat_row(content, "Learning")
	stats_review_label = _stat_row(content, "Review")

	var streak_row := HBoxContainer.new()
	streak_row.add_theme_constant_override("separation", 10)
	content.add_child(streak_row)
	var streak_caption := VBoxContainer.new()
	streak_caption.add_theme_constant_override("separation", 0)
	streak_row.add_child(streak_caption)
	streak_caption.add_child(_panel_caption("STREAK"))
	streak_label = Label.new()
	streak_label.text = "-- days"
	streak_label.add_theme_font_size_override("font_size", 16)
	streak_caption.add_child(streak_label)

	var goal_block := VBoxContainer.new()
	goal_block.add_theme_constant_override("separation", 4)
	content.add_child(goal_block)
	goal_block.add_child(_panel_caption("DAILY GOAL"))
	daily_goal_label = Label.new()
	daily_goal_label.text = "-- / --"
	daily_goal_label.add_theme_font_size_override("font_size", 16)
	goal_block.add_child(daily_goal_label)
	daily_goal_bar = ProgressBar.new()
	daily_goal_bar.custom_minimum_size = Vector2(0, 8)
	daily_goal_bar.show_percentage = false
	daily_goal_bar.min_value = 0
	daily_goal_bar.max_value = 1
	goal_block.add_child(daily_goal_bar)


func _stat_row(parent: VBoxContainer, caption: String) -> Label:
	var row := HBoxContainer.new()
	parent.add_child(row)
	var caption_label := Label.new()
	caption_label.text = caption
	caption_label.size_flags_horizontal = Control.SIZE_EXPAND_FILL
	row.add_child(caption_label)
	var value := Label.new()
	value.text = "--"
	value.add_theme_font_size_override("font_size", 15)
	row.add_child(value)
	return value


# ---------- Options menu ----------

func _build_options_menu(footer_row: HBoxContainer) -> void:
	options_backdrop = Control.new()
	options_backdrop.visible = false
	options_backdrop.top_level = true
	options_backdrop.mouse_filter = Control.MOUSE_FILTER_STOP
	options_backdrop.set_anchors_and_offsets_preset(Control.PRESET_FULL_RECT)
	options_backdrop.gui_input.connect(func(event: InputEvent):
		if event is InputEventMouseButton and event.pressed:
			_close_options_menu())
	add_child(options_backdrop)

	options_button = Button.new()
	options_button.text = "Options"
	options_button.custom_minimum_size = Vector2(0, 44)
	options_button.pressed.connect(_toggle_options_menu)
	footer_row.add_child(options_button)

	options_menu = PanelContainer.new()
	options_menu.visible = false
	options_menu.top_level = true
	add_child(options_menu)
	var list := VBoxContainer.new()
	list.add_theme_constant_override("separation", 2)
	options_menu.add_child(list)

	_options_menu_item(list, "Manage Flashcards", func(): main.show_screen("flashcards_hub"))
	options_bury_button = _options_menu_item(list, "Bury card until tomorrow", func(): _bury_current_card())
	options_suspend_button = _options_menu_item(list, "Suspend card", func(): _suspend_current_card())


func _options_menu_item(list: VBoxContainer, text: String, action: Callable) -> Button:
	var button := Button.new()
	button.text = text
	button.custom_minimum_size = Vector2(200, 40)
	button.alignment = HORIZONTAL_ALIGNMENT_LEFT
	button.pressed.connect(func():
		_close_options_menu()
		action.call())
	list.add_child(button)
	return button


func _toggle_options_menu() -> void:
	if options_menu.visible:
		_close_options_menu()
		return
	var at_live_with_card := history_cursor == session_history.size() and not current_card.is_empty()
	options_bury_button.disabled = not at_live_with_card
	options_suspend_button.disabled = not at_live_with_card
	options_menu.visible = true
	options_backdrop.visible = true
	options_menu.position = options_button.get_global_position() - Vector2(0, options_menu.size.y + 4)


func _close_options_menu() -> void:
	if options_menu != null:
		options_menu.visible = false
	if options_backdrop != null:
		options_backdrop.visible = false


func _bury_current_card() -> void:
	if history_cursor != session_history.size() or current_card.is_empty():
		return
	var card_id := str(current_card.get("id", ""))
	FlashcardService.bury_cards([card_id], _bury_until_tomorrow_utc())
	_push_history("buried", card_id)
	if not seen_card_ids.has(card_id):
		seen_card_ids.append(card_id)
	_load_next()
	_render_loading()


func _suspend_current_card() -> void:
	if history_cursor != session_history.size() or current_card.is_empty():
		return
	var card_id := str(current_card.get("id", ""))
	FlashcardService.suspend_cards([card_id], true)
	_push_history("suspended", card_id)
	if not seen_card_ids.has(card_id):
		seen_card_ids.append(card_id)
	_load_next()
	_render_loading()


func _bury_until_tomorrow_utc() -> String:
	var study_day_unix := Time.get_unix_time_from_datetime_string(study_day_start_utc.trim_suffix("Z"))
	return "%sZ" % Time.get_datetime_string_from_unix_time(study_day_unix + 86400, false)


func refresh_theme_controls() -> void:
	if card_panel == null:
		return
	var dark := UIThemeService.is_dark_mode()
	card_panel.add_theme_stylebox_override("panel", Brand.content_card_box(dark, true, Brand.ROYAL_BLUE))
	empty_label.add_theme_color_override("font_color", Brand.muted_color(dark))
	divider.color = Brand.ROYAL_BLUE if dark else Brand.PURPLE
	answer_caption.add_theme_color_override("font_color", Brand.ROYAL_BLUE if dark else Brand.PURPLE)
	extra_caption.add_theme_color_override("font_color", Brand.muted_color(dark))
	extra_label.add_theme_color_override("font_color", Brand.muted_color(dark))
	card_position_label.add_theme_color_override("font_color", Brand.muted_color(dark))
	_style_ghost_button(undo_button, dark)
	previous_button.add_theme_stylebox_override("normal", Brand.secondary_button_box(dark))
	previous_button.add_theme_stylebox_override("hover", Brand.secondary_button_box(dark, true))
	next_button.add_theme_stylebox_override("normal", Brand.secondary_button_box(dark))
	next_button.add_theme_stylebox_override("hover", Brand.secondary_button_box(dark, true))
	options_button.add_theme_stylebox_override("normal", Brand.secondary_button_box(dark))
	options_button.add_theme_stylebox_override("hover", Brand.secondary_button_box(dark, true))
	deck_panel.add_theme_stylebox_override("panel", _side_panel_box(dark))
	stats_panel.add_theme_stylebox_override("panel", _side_panel_box(dark))
	options_menu.add_theme_stylebox_override("panel", Brand.panel_box(dark))
	_update_progress_pips(history_cursor)
	_refresh_deck_panel()
	_refresh_stats_panel()


func _update_responsive_layout() -> void:
	if card_panel == null:
		return
	compact_layout = size.x < 1080.0
	deck_panel.visible = not compact_layout
	stats_panel.visible = not compact_layout
	var available := maxf((size.x - 48.0) if compact_layout else (size.x - 520.0), 240.0)
	card_panel.custom_minimum_size.x = minf(720.0, available)
	card_panel.custom_minimum_size.y = 340.0 if size.x < 720.0 else 420.0


# ---------- Deck / stats data ----------

func _on_decks_changed(loaded_decks: Array) -> void:
	decks = loaded_decks
	_refresh_deck_panel()


func _refresh_deck_panel() -> void:
	if deck_ring == null:
		return
	var dark := UIThemeService.is_dark_mode()
	var name := "All decks"
	var total := 0
	var mastered := 0
	var is_system := false
	if deck_id.is_empty():
		for summary in decks:
			total += int(summary.get("total", 0))
			mastered += int(summary.get("mastered", 0))
	else:
		for summary in decks:
			var deck: Dictionary = summary.get("deck", {})
			if str(deck.get("id", "")) == deck_id:
				name = str(deck.get("name", "Deck"))
				total = int(summary.get("total", 0))
				mastered = int(summary.get("mastered", 0))
				is_system = bool(deck.get("isSystem", false))
				break
	deck_name_label.text = name
	deck_system_badge.visible = is_system
	var fraction := float(mastered) / float(total) if total > 0 else 0.0
	deck_ring.configure(fraction, "%d%%" % roundi(fraction * 100.0), "Mastery", Brand.ROYAL_BLUE, dark)
	deck_mastered_label.text = "%d / %d cards mastered" % [mastered, total]


func _on_counts_changed(counts: Dictionary) -> void:
	latest_counts = counts
	_refresh_stats_panel()


func _refresh_stats_panel() -> void:
	if stats_new_ring == null or latest_counts.is_empty():
		return
	var dark := UIThemeService.is_dark_mode()
	var due := int(latest_counts.get("due", 0))
	var new_available := int(latest_counts.get("newAvailable", 0))
	var learning := int(latest_counts.get("learning", 0))
	var review := int(latest_counts.get("review", 0))
	var streak := int(latest_counts.get("currentStreakDays", 0))
	var reviews_today := int(latest_counts.get("reviewsToday", 0))
	var daily_goal := int(latest_counts.get("dailyGoal", 0))

	var new_fraction := float(new_available) / float(new_available + due) if (new_available + due) > 0 else 0.0
	stats_new_ring.configure(new_fraction, str(new_available), "New", Brand.ROYAL_BLUE, dark)
	stats_due_label.text = str(due)
	stats_learning_label.text = str(learning)
	stats_review_label.text = str(review)
	streak_label.text = "%d day%s" % [streak, "" if streak == 1 else "s"]
	daily_goal_label.text = "%d / %d" % [reviews_today, daily_goal]
	daily_goal_bar.max_value = maxf(1.0, float(daily_goal))
	daily_goal_bar.value = float(reviews_today)


# ---------- Session history / navigation ----------

func _push_history(action: String, card_id: String, rating: String = "", client_review_id: String = "") -> void:
	var entry := {
		"note": current_note, "card": current_card, "rating_options": rating_options,
		"action": action, "card_id": card_id
	}
	if not rating.is_empty():
		entry["rating"] = rating
		entry["client_review_id"] = client_review_id
	session_history.append(entry)
	history_cursor = session_history.size()


func _snapshot_live_before_browsing() -> void:
	live_note = current_note
	live_card = current_card
	live_rating_options = rating_options
	live_revealed = revealed
	live_due_remaining = due_remaining
	live_new_remaining = new_remaining


func _return_to_live() -> void:
	history_cursor = session_history.size()
	current_note = live_note
	current_card = live_card
	rating_options = live_rating_options
	due_remaining = live_due_remaining
	new_remaining = live_new_remaining
	undo_button.visible = false
	revealed = false
	if current_note.is_empty() and current_card.is_empty():
		_render_empty({"dueRemaining": due_remaining, "newRemaining": new_remaining})
	else:
		_render_card()
		if live_revealed:
			_reveal()
	_update_card_position_label(history_cursor)
	_update_progress_pips(history_cursor)
	_update_footer_button_states()


func _render_history_entry(index: int) -> void:
	var entry: Dictionary = session_history[index]
	current_note = entry.get("note", {})
	current_card = entry.get("card", {})
	rating_options = entry.get("rating_options", [])
	revealed = false
	_render_card()
	_reveal()
	grade_row.visible = false
	reveal_button.visible = false
	var is_graded_entry: bool = entry.get("action", "") == "graded"
	var is_last_graded_card: bool = str(entry.get("card_id", "")) == last_card_id
	var has_undoable_review: bool = not last_client_review_id.is_empty()
	undo_button.visible = is_graded_entry and is_last_graded_card and has_undoable_review
	undo_button.disabled = false
	undo_button.text = "Undo this rating"
	_update_card_position_label(index)
	_update_progress_pips(index)
	_update_footer_button_states()


func _go_previous() -> void:
	if history_cursor <= 0:
		return
	if history_cursor == session_history.size():
		_snapshot_live_before_browsing()
	history_cursor -= 1
	_render_history_entry(history_cursor)


func _go_next() -> void:
	if history_cursor >= session_history.size():
		_skip_current_card()
		return
	history_cursor += 1
	if history_cursor >= session_history.size():
		_return_to_live()
	else:
		_render_history_entry(history_cursor)


func _skip_current_card() -> void:
	if current_card.is_empty() or awaiting_next:
		return
	var card_id := str(current_card.get("id", ""))
	_push_history("skipped", card_id)
	if not seen_card_ids.has(card_id):
		seen_card_ids.append(card_id)
	_load_next()
	_render_loading()


func _update_card_position_label(position_index: int) -> void:
	card_position_label.visible = session_total > 0
	if session_total > 0:
		card_position_label.text = "Card %d of %d" % [position_index + 1, maxi(session_total, position_index + 1)]


func _update_progress_pips(position_index: int) -> void:
	var dark := UIThemeService.is_dark_mode()
	var fraction := 0.0 if session_total <= 0 else float(position_index) / float(session_total)
	var filled := clampi(floori(fraction * progress_pips.size()), 0, progress_pips.size())
	for i in progress_pips.size():
		var pip: PanelContainer = progress_pips[i]
		pip.add_theme_stylebox_override("panel", _pip_box(i < filled, dark))


func _update_footer_button_states() -> void:
	var at_live := history_cursor == session_history.size()
	previous_button.disabled = history_cursor <= 0
	next_button.disabled = at_live and current_card.is_empty()


func _load_next() -> void:
	awaiting_next = true
	FlashcardService.request_next_card(deck_id, seen_card_ids, study_day_start_utc, shuffle_enabled)


func _on_next_card_loaded(card: Dictionary) -> void:
	awaiting_next = false
	var note: Variant = card.get("note")
	var schedule: Variant = card.get("card")
	if typeof(note) != TYPE_DICTIONARY or typeof(schedule) != TYPE_DICTIONARY:
		current_note = {}
		current_card = {}
		_render_empty(card)
		_update_footer_button_states()
		return
	current_note = note
	current_card = schedule
	rating_options = card.get("ratingOptions", [])
	due_remaining = int(card.get("dueRemaining", 0))
	new_remaining = int(card.get("newRemaining", 0))
	if session_total < 0:
		session_total = due_remaining + new_remaining
	history_cursor = session_history.size()
	revealed = false
	loaded_started_ms = Time.get_ticks_msec()
	_render_card()
	_update_card_position_label(history_cursor)
	_update_progress_pips(history_cursor)
	_update_footer_button_states()


func _on_next_card_failed(message: String) -> void:
	awaiting_next = false
	progress_label.text = message


func _render_loading() -> void:
	empty_label.visible = false
	front_label.visible = true
	front_label.text = "Loading..."
	_hide_answer()
	reveal_button.visible = false
	grade_row.visible = false


func _render_empty(card: Dictionary) -> void:
	empty_label.visible = true
	front_label.visible = false
	_hide_answer()
	reveal_button.visible = false
	grade_row.visible = false
	progress_label.text = "0 due"
	if typeof(card) == TYPE_DICTIONARY:
		progress_label.text = "%d due, %d new available" % [int(card.get("dueRemaining", 0)), int(card.get("newRemaining", 0))]


func _hide_answer() -> void:
	divider.visible = false
	answer_caption.visible = false
	back_label.visible = false
	extra_caption.visible = false
	extra_label.visible = false


func _render_card() -> void:
	empty_label.visible = false
	var note_type := str(current_note.get("type", "basic"))
	var variant := int(current_card.get("variant", 0))
	if note_type == "cloze":
		front_label.text = Cloze.render_front(str(current_note.get("prompt", "")), variant)
	else:
		front_label.text = str(current_note.get("prompt", ""))
	front_label.visible = true
	_hide_answer()
	reveal_button.visible = true
	grade_row.visible = false
	progress_label.text = "%d due, %d new available" % [due_remaining, new_remaining]


func _reveal() -> void:
	if current_note.is_empty():
		return
	revealed = true
	reveal_started_ms = Time.get_ticks_msec()
	var note_type := str(current_note.get("type", "basic"))
	if note_type == "cloze":
		back_label.text = Cloze.render_back(str(current_note.get("prompt", "")))
	else:
		back_label.text = str(current_note.get("answer", ""))
	var extra := str(current_note.get("extra", ""))
	divider.visible = true
	answer_caption.visible = true
	back_label.visible = true
	extra_caption.visible = not extra.is_empty()
	extra_label.visible = not extra.is_empty()
	extra_label.text = extra
	reveal_button.visible = false
	grade_row.visible = true
	for rating in grade_buttons:
		var button: Button = grade_buttons[rating]
		button.text = "%s\n%s" % [rating.capitalize(), _interval_label_for(rating)]


func _interval_label_for(rating: String) -> String:
	for option in rating_options:
		if str(option.get("rating", "")) == rating:
			return str(option.get("intervalLabel", ""))
	return ""


func _grade(rating: String) -> void:
	if current_card.is_empty() or history_cursor != session_history.size():
		return
	var card_id := str(current_card.get("id", ""))
	var expected_revision := int(current_card.get("revision", 0))
	var duration_seconds := int(float(Time.get_ticks_msec() - loaded_started_ms) / 1000.0)
	var client_review_id := FlashcardService.submit_review(card_id, rating, expected_revision, duration_seconds, study_day_start_utc)
	last_client_review_id = client_review_id
	last_card_id = card_id
	_push_history("graded", card_id, rating, client_review_id)
	if not seen_card_ids.has(card_id):
		seen_card_ids.append(card_id)
	_load_next()
	_render_loading()
	FlashcardService.fetch_counts()


func _on_review_synced(_card_id: String, _updated_card: Dictionary) -> void:
	pass


func _undo() -> void:
	if last_client_review_id.is_empty():
		return
	undo_button.disabled = true
	FlashcardService.undo_last_review(last_client_review_id, func(_restored: Dictionary):
		var undone_card_id := last_card_id
		last_client_review_id = ""
		last_card_id = ""
		seen_card_ids.erase(undone_card_id)
		_return_to_live()
		_load_next()
		_render_loading()
		FlashcardService.fetch_counts())


func _on_review_paused(message: String) -> void:
	paused_banner.text = message
	paused_banner.visible = true


func _on_review_resumed() -> void:
	paused_banner.visible = false
	if awaiting_next:
		_load_next()


func _input(event: InputEvent) -> void:
	if not visible or not is_visible_in_tree():
		return
	if not (event is InputEventKey) or not event.pressed or event.echo:
		return
	if history_cursor != session_history.size():
		return
	if not revealed:
		if event.keycode == KEY_SPACE:
			_reveal()
			get_viewport().set_input_as_handled()
		return
	var rating := rating_for_keycode(event.keycode)
	if not rating.is_empty():
		_grade(rating)
		get_viewport().set_input_as_handled()


static func rating_for_keycode(keycode: Key) -> String:
	match keycode:
		KEY_1: return "again"
		KEY_2: return "hard"
		KEY_3: return "good"
		KEY_4: return "easy"
		_: return ""