extends Node

signal session_changed

var active_questions: Array = []
var answers: Array = []
var current_index := 0
var mode := "Tutor"
var system_name := "All Systems"
var seconds_remaining := 0.0
var session_initial_seconds := 0.0
var block_started := false
var session_kind := "block"
var core_question_pool: Array = []
var core_answer_count := 0
var core_score := 0
var core_energy := 70
var core_target_seconds := 90.0
var core_current_target_seconds := 90.0
var core_current_had_wrong_attempt := false
var current_question_started_at := 0.0
var current_question_pause_started_at := 0.0
var core_question_total_elapsed_seconds := 0.0
var core_question_total_active_since := 0.0
var core_question_total_frozen := false
var core_status_message := ""
var simulation_block_index := 0
var simulation_total_blocks := 12
var simulation_deadline_unix := 0.0
var review_first_submission_recorded := false
var core_block_size := DEFAULT_CORE_BLOCK_SIZE
var show_review_followups := true

const CORE_MIN_TARGET_SECONDS := 45.0
const CORE_MAX_TARGET_SECONDS := 150.0
const CORE_RETRY_TARGET_SECONDS := 30.0
const DEFAULT_CORE_BLOCK_SIZE := 10
const CORE_BLOCK_SIZE_MIN := 5
const CORE_BLOCK_SIZE_MAX := 40
const SETTINGS_PATH := "user://settings.cfg"
const SETTINGS_SECTION := "session"
const SETTINGS_KEY_CORE_BLOCK_SIZE := "core_block_size"
const SETTINGS_KEY_SHOW_REVIEW_FOLLOWUPS := "show_review_followups"


func _ready() -> void:
	_load_core_block_size()
	_load_show_review_followups()


func set_core_block_size(value: int) -> void:
	var clamped := clampi(value, CORE_BLOCK_SIZE_MIN, CORE_BLOCK_SIZE_MAX)
	if clamped == core_block_size:
		return
	core_block_size = clamped
	var config := ConfigFile.new()
	config.load(SETTINGS_PATH)
	config.set_value(SETTINGS_SECTION, SETTINGS_KEY_CORE_BLOCK_SIZE, core_block_size)
	if config.save(SETTINGS_PATH) != OK:
		push_warning("Unable to save core question block size preference.")


func set_show_review_followups(value: bool) -> void:
	if show_review_followups == value:
		return
	show_review_followups = value
	var config := ConfigFile.new()
	config.load(SETTINGS_PATH)
	config.set_value(SETTINGS_SECTION, SETTINGS_KEY_SHOW_REVIEW_FOLLOWUPS, show_review_followups)
	if config.save(SETTINGS_PATH) != OK:
		push_warning("Unable to save follow-up question preference.")


func _load_core_block_size() -> void:
	var config := ConfigFile.new()
	if config.load(SETTINGS_PATH) == OK:
		core_block_size = clampi(
			int(config.get_value(SETTINGS_SECTION, SETTINGS_KEY_CORE_BLOCK_SIZE, DEFAULT_CORE_BLOCK_SIZE)),
			CORE_BLOCK_SIZE_MIN, CORE_BLOCK_SIZE_MAX)


func _load_show_review_followups() -> void:
	var config := ConfigFile.new()
	if config.load(SETTINGS_PATH) == OK:
		show_review_followups = bool(config.get_value(SETTINGS_SECTION, SETTINGS_KEY_SHOW_REVIEW_FOLLOWUPS, true))


func start_dynamic_question(question: Dictionary) -> bool:
	if question.is_empty():
		return false
	system_name = str(question.get("system", "All Systems"))
	mode = "Tutor"
	session_kind = "dynamic"
	active_questions = [_prepare_question_choices(question)]
	answers = [null]
	current_index = 0
	seconds_remaining = 0.0
	session_initial_seconds = 90.0
	current_question_started_at = Time.get_ticks_msec() / 1000.0
	current_question_pause_started_at = 0.0
	block_started = true
	session_changed.emit()
	return true


func replace_dynamic_question(question: Dictionary) -> bool:
	if session_kind != "dynamic" or question.is_empty():
		return false
	active_questions = [_prepare_question_choices(question)]
	answers = [null]
	current_index = 0
	current_question_started_at = Time.get_ticks_msec() / 1000.0
	current_question_pause_started_at = 0.0
	session_changed.emit()
	return true

func start_block(selected_system: String, block_size: int, selected_mode: String) -> void:
	system_name = selected_system
	mode = selected_mode
	session_kind = "block"
	active_questions = QuestionBankService.build_block(selected_system, block_size)
	for index in range(active_questions.size()):
		active_questions[index] = _prepare_question_choices(active_questions[index])
	answers.clear()
	answers.resize(active_questions.size())
	current_index = 0
	seconds_remaining = float(active_questions.size() * 90)
	session_initial_seconds = seconds_remaining
	block_started = true
	session_changed.emit()


func start_core_run() -> bool:
	system_name = "All Systems"
	mode = "Core"
	session_kind = "core"
	active_questions.clear()
	answers.clear()
	core_question_pool.clear()
	current_index = -1
	seconds_remaining = 0.0
	session_initial_seconds = core_current_target_seconds
	block_started = true
	core_answer_count = 0
	core_score = 0
	core_energy = 70
	core_target_seconds = 90.0
	core_current_target_seconds = core_target_seconds
	core_current_had_wrong_attempt = false
	core_question_total_elapsed_seconds = 0.0
	core_question_total_active_since = 0.0
	core_question_total_frozen = false
	core_status_message = ""
	if not advance_core_question():
		block_started = false
		core_status_message = "All available questions cleared."
		session_changed.emit()
		return false
	return true


func start_bookmark_question(question: Dictionary) -> bool:
	if question.is_empty():
		return false
	system_name = str(question.get("system", "All Systems"))
	mode = "Tutor"
	session_kind = "bookmark"
	active_questions = [_prepare_question_choices(question)]
	answers = [null]
	current_index = 0
	seconds_remaining = 0.0
	session_initial_seconds = 90.0
	current_question_started_at = Time.get_ticks_msec() / 1000.0
	current_question_pause_started_at = 0.0
	block_started = true
	session_changed.emit()
	return true


func replace_bookmark_question(question: Dictionary) -> bool:
	if session_kind != "bookmark" or question.is_empty():
		return false
	active_questions = [_prepare_question_choices(question)]
	answers = [null]
	current_index = 0
	current_question_started_at = Time.get_ticks_msec() / 1000.0
	current_question_pause_started_at = 0.0
	session_changed.emit()
	return true


func start_review_question(question: Dictionary) -> bool:
	if question.is_empty():
		return false
	system_name = str(question.get("system", "All Systems"))
	mode = "Tutor"
	session_kind = "review"
	active_questions = [_prepare_question_choices(question)]
	answers = [null]
	current_index = 0
	seconds_remaining = 0.0
	session_initial_seconds = 90.0
	current_question_started_at = Time.get_ticks_msec() / 1000.0
	current_question_pause_started_at = 0.0
	review_first_submission_recorded = false
	block_started = true
	session_changed.emit()
	return true


func replace_review_question(question: Dictionary) -> bool:
	if session_kind != "review" or question.is_empty():
		return false
	active_questions = [_prepare_question_choices(question)]
	answers = [null]
	current_index = 0
	current_question_started_at = Time.get_ticks_msec() / 1000.0
	current_question_pause_started_at = 0.0
	review_first_submission_recorded = false
	session_changed.emit()
	return true


func start_simulation_block(questions: Array, block_index: int, total_blocks: int, deadline_unix: float) -> void:
	system_name = "All Systems"
	mode = "Simulation"
	session_kind = "simulation"
	active_questions = questions.duplicate(true)
	for index in range(active_questions.size()):
		active_questions[index] = _prepare_question_choices(active_questions[index])
	answers.clear()
	answers.resize(active_questions.size())
	current_index = 0
	simulation_block_index = block_index
	simulation_total_blocks = total_blocks
	simulation_deadline_unix = deadline_unix
	seconds_remaining = maxf(0.0, deadline_unix - Time.get_unix_time_from_system())
	session_initial_seconds = maxf(seconds_remaining, float(active_questions.size() * 90))
	block_started = true
	current_question_started_at = Time.get_ticks_msec() / 1000.0
	session_changed.emit()


func restore_simulation_responses(saved_responses: Array) -> void:
	if session_kind != "simulation":
		return
	for response in saved_responses:
		if typeof(response) != TYPE_DICTIONARY:
			continue
		var question_id := str(response.get("questionExternalId", ""))
		for index in range(active_questions.size()):
			if str(active_questions[index].get("id", "")) == question_id:
				answers[index] = {
					"question": active_questions[index].duplicate(true),
					"selected_choice_id": str(response.get("choiceId", "")),
					"is_correct": false,
					"eliminated_choice_ids": response.get("eliminatedChoiceIds", []).duplicate(),
					"flagged": bool(response.get("flagged", false)),
					"elapsed_seconds": int(response.get("elapsedSeconds", 0)),
					"is_submitted": _simulation_response_is_submitted(response)
				}
				break


func _simulation_response_is_submitted(response: Dictionary) -> bool:
	var submitted: Variant = response.get("isSubmitted", null)
	if submitted == null:
		return not str(response.get("choiceId", "")).is_empty()
	return bool(submitted)


func get_current_question() -> Dictionary:
	if active_questions.is_empty() or current_index < 0 or current_index >= active_questions.size():
		return {}
	return active_questions[current_index]


func answer_current(choice_id: String, eliminated: Array, flagged: bool, is_submitted := false) -> Dictionary:
	var question := get_current_question()
	if question.is_empty():
		return {}

	var answer := {
		"question": question.duplicate(true),
		"selected_choice_id": choice_id,
		"is_correct": choice_id == str(question.get("correct_choice_id", "")),
		"eliminated_choice_ids": eliminated.duplicate(),
		"flagged": flagged,
		"elapsed_seconds": get_current_elapsed_seconds(),
		"target_seconds": core_target_seconds if session_kind == "core" else 0.0
	}
	answers[current_index] = answer
	if session_kind == "simulation":
		answer["is_correct"] = false
		answer["is_submitted"] = is_submitted
		answers[current_index] = answer
		session_changed.emit()
		return answer
	if session_kind == "core":
		_apply_core_answer_rewards(answer)
	session_changed.emit()
	return answer


func submit_core_attempt(choice_id: String, eliminated: Array, flagged: bool) -> Dictionary:
	var question := get_current_question()
	if question.is_empty():
		return {}

	var answer := {
		"question": question.duplicate(true),
		"selected_choice_id": choice_id,
		"is_correct": choice_id == str(question.get("correct_choice_id", "")),
		"eliminated_choice_ids": eliminated.duplicate(),
		"flagged": flagged,
		"elapsed_seconds": get_current_elapsed_seconds(),
		"target_seconds": core_current_target_seconds
	}

	if bool(answer.get("is_correct", false)):
		var mastered := not core_current_had_wrong_attempt
		answers[current_index] = answer
		_freeze_core_question_total_timer()
		_apply_core_answer_rewards(answer, mastered)
		session_changed.emit()
		return {
			"answer": answer,
			"is_correct": true,
			"final": true,
			"mastered": mastered
		}

	ProfileService.record_wrong_attempt(question)
	core_current_had_wrong_attempt = true
	_apply_core_wrong_penalty(answer)
	_start_core_retry_window()
	session_changed.emit()
	return {
		"answer": answer,
		"is_correct": false,
		"final": false,
		"mastered": false
	}


func submit_bookmark_attempt(choice_id: String, eliminated: Array, flagged: bool) -> Dictionary:
	var question := get_current_question()
	if session_kind != "bookmark" or question.is_empty():
		return {}
	var answer := {
		"question": question.duplicate(true),
		"selected_choice_id": choice_id,
		"is_correct": choice_id == str(question.get("correct_choice_id", "")),
		"eliminated_choice_ids": eliminated.duplicate(),
		"flagged": flagged,
		"elapsed_seconds": get_current_elapsed_seconds(),
		"target_seconds": 0.0
	}
	if bool(answer.is_correct):
		answers[current_index] = answer
		session_changed.emit()
	return {"answer": answer, "is_correct": bool(answer.is_correct), "final": bool(answer.is_correct)}


func submit_review_attempt(choice_id: String, eliminated: Array, flagged: bool) -> Dictionary:
	var question := get_current_question()
	if session_kind != "review" or question.is_empty():
		return {}
	var first_submission := not review_first_submission_recorded
	var answer := {
		"question": question.duplicate(true),
		"selected_choice_id": choice_id,
		"is_correct": choice_id == str(question.get("correct_choice_id", "")),
		"eliminated_choice_ids": eliminated.duplicate(),
		"flagged": flagged,
		"elapsed_seconds": get_current_elapsed_seconds(),
		"target_seconds": 0.0
	}
	review_first_submission_recorded = true
	if bool(answer.is_correct):
		answers[current_index] = answer
		session_changed.emit()
	return {
		"answer": answer,
		"is_correct": bool(answer.is_correct),
		"final": bool(answer.is_correct),
		"first_submission": first_submission
	}


func skip_bookmark_question(eliminated: Array, flagged: bool) -> Dictionary:
	var question := get_current_question()
	if session_kind != "bookmark" or question.is_empty():
		return {}
	var answer := {
		"question": question.duplicate(true),
		"selected_choice_id": "",
		"is_correct": false,
		"is_skip": true,
		"eliminated_choice_ids": eliminated.duplicate(),
		"flagged": flagged,
		"elapsed_seconds": get_current_elapsed_seconds(),
		"target_seconds": 0.0
	}
	answers[current_index] = answer
	session_changed.emit()
	return answer


func skip_core_question(eliminated: Array, flagged: bool) -> Dictionary:
	var question := get_current_question()
	if question.is_empty():
		return {}

	var answer := {
		"question": question.duplicate(true),
		"selected_choice_id": "",
		"is_correct": false,
		"is_skip": true,
		"eliminated_choice_ids": eliminated.duplicate(),
		"flagged": flagged,
		"elapsed_seconds": get_current_elapsed_seconds(),
		"target_seconds": core_current_target_seconds
	}
	answers[current_index] = answer
	ProfileService.record_wrong_attempt(question)
	_apply_core_wrong_penalty(answer)
	core_target_seconds = min(CORE_MAX_TARGET_SECONDS, core_target_seconds * 1.05)
	session_changed.emit()
	return answer


func move_previous() -> bool:
	if current_index > 0:
		current_index -= 1
		session_changed.emit()
		return true
	return false


func move_next() -> bool:
	if session_kind == "core":
		return advance_core_question()
	if current_index + 1 < active_questions.size():
		current_index += 1
		session_changed.emit()
		return true
	return false


func move_to(index: int) -> bool:
	if index >= 0 and index < active_questions.size():
		current_index = index
		session_changed.emit()
		return true
	return false


func get_progress_text() -> String:
	if session_kind == "core":
		return str(core_answer_count + 1)
	if session_kind == "simulation":
		return "Block %d/%d  |  Question %d/%d" % [simulation_block_index + 1, simulation_total_blocks, current_index + 1, active_questions.size()]
	return "%d / %d" % [min(current_index + 1, active_questions.size()), active_questions.size()]


func finish_block() -> Dictionary:
	if session_kind in ["core", "bookmark", "review"]:
		block_started = false
		session_changed.emit()
		return {}

	var final_answers: Array = []
	for index in range(active_questions.size()):
		if answers[index] == null:
			final_answers.append({
				"question": active_questions[index].duplicate(true),
				"selected_choice_id": "",
				"is_correct": false,
				"eliminated_choice_ids": [],
				"flagged": false
			})
		else:
			final_answers.append(answers[index])

	var results := ProgressionService.calculate_block_rewards(final_answers, mode, system_name)
	ProfileService.apply_block_results(results)
	block_started = false
	session_changed.emit()
	return results


func has_answered_current() -> bool:
	return get_answer_for_index(current_index) != null


func get_answer_for_index(index: int) -> Variant:
	if index < 0 or index >= answers.size():
		return null
	return answers[index]


func update_question_choice_percentages(question_id: String, percentages: Dictionary) -> void:
	for index in range(active_questions.size()):
		var question: Dictionary = active_questions[index]
		if str(question.get("id", "")) == question_id:
			question["choice_selection_percentages"] = percentages
			active_questions[index] = question
			break


func update_question_elo(question_id: String, question_elo: int) -> void:
	for index in range(active_questions.size()):
		var question: Dictionary = active_questions[index]
		if str(question.get("id", "")) == question_id:
			question["question_elo"] = question_elo
			active_questions[index] = question
			break


func advance_core_question() -> bool:
	var question := _draw_core_question()
	if question.is_empty():
		core_status_message = "All available questions cleared."
		return false
	return append_core_question(question)


func append_core_question(question: Dictionary) -> bool:
	if question.is_empty():
		return false
	active_questions.append(_prepare_question_choices(question.duplicate(true)))
	answers.append(null)
	current_index = active_questions.size() - 1
	current_question_started_at = Time.get_ticks_msec() / 1000.0
	current_question_pause_started_at = 0.0
	core_current_target_seconds = core_target_seconds
	core_question_total_elapsed_seconds = 0.0
	core_question_total_active_since = current_question_started_at
	core_question_total_frozen = false
	core_current_had_wrong_attempt = false
	session_changed.emit()
	return true


func get_core_excluded_question_ids() -> Array:
	var excluded: Array = ProfileService.get_profile().get("correct_question_ids", []).duplicate()
	for question in active_questions:
		var question_id := str(question.get("id", ""))
		if question_id != "" and not excluded.has(question_id):
			excluded.append(question_id)
	return excluded


func get_current_elapsed_seconds() -> float:
	if current_question_started_at <= 0.0:
		return 0.0
	var now := current_question_pause_started_at if current_question_pause_started_at > 0.0 else Time.get_ticks_msec() / 1000.0
	return max(0.0, now - current_question_started_at)


func get_core_timer_ratio() -> float:
	if session_kind != "core" or core_current_target_seconds <= 0.0:
		return 1.0
	var ratio := 1.0 - (get_current_elapsed_seconds() / core_current_target_seconds)
	return clamp(ratio, 0.0, 1.0)


func get_core_question_total_elapsed_seconds() -> float:
	if session_kind != "core":
		return 0.0
	var elapsed := core_question_total_elapsed_seconds
	if core_question_total_active_since > 0.0:
		elapsed += Time.get_ticks_msec() / 1000.0 - core_question_total_active_since
	return maxf(0.0, elapsed)


func get_session_timer_ratio() -> float:
	if session_kind == "core":
		return get_core_timer_ratio()
	if session_initial_seconds <= 0.0:
		return 1.0
	return clamp(seconds_remaining / session_initial_seconds, 0.0, 1.0)


func pause_current_question_timer() -> void:
	if session_kind in ["core", "review"] and current_question_pause_started_at <= 0.0:
		var now := Time.get_ticks_msec() / 1000.0
		current_question_pause_started_at = now
		if session_kind == "core":
			_pause_core_question_total_timer(now)


func resume_current_question_timer() -> void:
	if session_kind in ["core", "review"] and current_question_pause_started_at > 0.0:
		var now := Time.get_ticks_msec() / 1000.0
		var paused_duration := now - current_question_pause_started_at
		current_question_started_at += paused_duration
		current_question_pause_started_at = 0.0
		if session_kind == "core" and not core_question_total_frozen:
			core_question_total_active_since = now


func _pause_core_question_total_timer(now: float) -> void:
	if core_question_total_active_since <= 0.0:
		return
	core_question_total_elapsed_seconds += maxf(0.0, now - core_question_total_active_since)
	core_question_total_active_since = 0.0


func _freeze_core_question_total_timer() -> void:
	_pause_core_question_total_timer(Time.get_ticks_msec() / 1000.0)
	core_question_total_frozen = true


func _draw_core_question() -> Dictionary:
	if core_question_pool.is_empty():
		core_question_pool = _build_core_question_pool()
		core_question_pool.shuffle()
	if core_question_pool.is_empty():
		return {}

	var last_id := str(get_current_question().get("id", ""))
	for index in range(core_question_pool.size()):
		var candidate: Dictionary = core_question_pool[index]
		if str(candidate.get("id", "")) != last_id or core_question_pool.size() == 1:
			core_question_pool.remove_at(index)
			return _prepare_question_choices(candidate.duplicate(true))
	return {}


func _prepare_question_choices(question: Dictionary) -> Dictionary:
	var existing: Array = question.get("presented_choices", [])
	if not existing.is_empty():
		return question

	var all_choices: Array = question.get("choices", []).duplicate(true)
	var correct_id := str(question.get("correct_choice_id", ""))
	var percentages: Dictionary = question.get("choice_selection_percentages", {})
	var correct_choice: Dictionary = {}
	var distractors: Array = []
	for choice in all_choices:
		if typeof(choice) != TYPE_DICTIONARY:
			continue
		if str(choice.get("id", "")) == correct_id:
			correct_choice = choice
		else:
			distractors.append(choice)

	var presented: Array = _select_weighted_distractors(distractors, percentages, 4)
	if not correct_choice.is_empty():
		presented.append(correct_choice)
	elif not all_choices.is_empty():
		presented = all_choices.slice(0, min(5, all_choices.size()))
	presented.shuffle()
	question["presented_choices"] = presented
	return question


func _select_weighted_distractors(distractors: Array, percentages: Dictionary, count: int) -> Array:
	var remaining: Array = distractors.duplicate(true)
	var selected: Array = []
	while selected.size() < count and not remaining.is_empty():
		var total_weight := 0.0
		for choice in remaining:
			total_weight += _distractor_weight(str(choice.get("id", "")), percentages)
		var threshold := randf() * total_weight
		var cumulative := 0.0
		var selected_index := remaining.size() - 1
		for index in range(remaining.size()):
			cumulative += _distractor_weight(str(remaining[index].get("id", "")), percentages)
			if threshold < cumulative:
				selected_index = index
				break
		selected.append(remaining[selected_index])
		remaining.remove_at(selected_index)
	return selected


func _distractor_weight(choice_id: String, percentages: Dictionary) -> float:
	var selection_rate := clampf(float(percentages.get(choice_id, 0)), 0.0, 100.0)
	return 1.0 + 5.0 * selection_rate / 100.0


func _build_core_question_pool() -> Array:
	var pool: Array = []
	var profile := ProfileService.get_profile()
	var correct_ids: Array = profile.get("correct_question_ids", [])
	for question in QuestionBankService.get_all_questions():
		var question_id := str(question.get("id", ""))
		if question_id == "" or not correct_ids.has(question_id):
			pool.append(question)
	return pool


func _start_core_retry_window() -> void:
	core_current_target_seconds = CORE_RETRY_TARGET_SECONDS
	current_question_started_at = Time.get_ticks_msec() / 1000.0
	current_question_pause_started_at = 0.0


func _apply_core_wrong_penalty(_answer: Dictionary) -> void:
	core_score -= 25
	core_energy = max(0, core_energy - 14)


func _apply_core_answer_rewards(answer: Dictionary, mastered: bool = true) -> void:
	core_answer_count += 1
	var elapsed := float(answer.get("elapsed_seconds", 0.0))
	var target := core_current_target_seconds
	if target < CORE_MIN_TARGET_SECONDS:
		target = CORE_MIN_TARGET_SECONDS
	var is_correct := bool(answer.get("is_correct", false))
	var score_delta := 100 if is_correct else 0
	if elapsed > target:
		var overage_ratio := (elapsed - target) / target
		if overage_ratio > 1.0:
			overage_ratio = 1.0
		score_delta -= int(round(40.0 * overage_ratio))
	if not is_correct:
		score_delta -= 25
	core_score += score_delta

	if is_correct:
		core_energy = min(100, core_energy + 8)
	else:
		core_energy = max(0, core_energy - 14)
	if elapsed > target:
		core_energy = max(0, core_energy - 4)

	if mastered and is_correct and elapsed <= target:
		core_target_seconds = max(CORE_MIN_TARGET_SECONDS, core_target_seconds * 0.97)
	elif not mastered or not is_correct or elapsed > target * 1.25:
		core_target_seconds = min(CORE_MAX_TARGET_SECONDS, core_target_seconds * 1.05)
	else:
		core_target_seconds = max(CORE_MIN_TARGET_SECONDS, core_target_seconds * 0.99)

	var results := ProgressionService.calculate_question_rewards(answer, elapsed, target, score_delta)
	results["mastered"] = mastered
	ProfileService.apply_question_results(results)