extends Node

class UnlockGoalRequirement extends RefCounted:
	var currency_id: StringName
	var amount: BigNumber

	func _init(req_currency_id: StringName, req_amount: BigNumber) -> void:
		currency_id = req_currency_id
		amount = req_amount

class UnlockGoal extends RefCounted:
	var id: StringName
	var target_generator_id: StringName
	var requirements: Array[UnlockGoalRequirement]

	func _init(goal_id: StringName, target_id: StringName, goal_requirements: Array[UnlockGoalRequirement]) -> void:
		id = goal_id
		target_generator_id = target_id
		requirements = goal_requirements

const GOALS_FILE_PATH: String = "res://generator-unlock-goals/generator_unlock_goals.json"
const SCHEMA_VERSION: int = 1

var _goals: Array[UnlockGoal] = []
var _known_generator_ids: Dictionary = {}
var _warned_unknown_target_ids: Dictionary = {}

func _ready() -> void:
	_collect_known_generator_ids()
	_load_goals()
	GameState.currency_changed.connect(_on_currency_changed)
	GameState.generator_state_changed.connect(_on_generator_state_changed)
	_evaluate_all_goals()
	_evaluate_all_goals.call_deferred()

func _on_currency_changed(_changed_currency_id: StringName, _new_amount: BigNumber) -> void:
	_evaluate_all_goals()

func _on_generator_state_changed(generator_id: StringName, _state: Dictionary) -> void:
	var generator_key: String = String(generator_id)
	if not generator_key.is_empty():
		_known_generator_ids[generator_key] = true
	_evaluate_all_goals()

func _evaluate_all_goals() -> void:
	if _goals.is_empty():
		return

	for goal in _goals:
		_evaluate_goal(goal)

func _evaluate_goal(goal: UnlockGoal) -> bool:
	if _is_goal_completed(goal):
		return false
	if not _can_resolve_target(goal.target_generator_id):
		return false

	for requirement in goal.requirements:
		var total_amount: BigNumber = _get_total_currency_amount(requirement.currency_id)
		if total_amount.is_less_than(requirement.amount):
			return false

	GameState.set_generator_unlocked(goal.target_generator_id, true)
	GameState.set_generator_available(goal.target_generator_id, true)
	print("[UnlockSystem] Goal completed: %s -> %s" % [String(goal.id), String(goal.target_generator_id)])
	return true

func _is_goal_completed(goal: UnlockGoal) -> bool:
	return (
		GameState.is_generator_unlocked(goal.target_generator_id)
		and GameState.is_generator_available(goal.target_generator_id)
	)

func _can_resolve_target(target_generator_id: StringName) -> bool:
	var target_key: String = String(target_generator_id)
	if target_key.is_empty():
		return false

	if _known_generator_ids.has(target_key) or GameState.generator_states.has(target_key):
		return true

	if not _warned_unknown_target_ids.has(target_key):
		_warned_unknown_target_ids[target_key] = true
		push_warning("Unlock goal target generator not found in scene/state: '%s'" % target_key)
	return false

func _load_goals() -> void:
	_goals.clear()

	if not FileAccess.file_exists(GOALS_FILE_PATH):
		push_warning("Unlock goals file not found: %s" % GOALS_FILE_PATH)
		return

	var file: FileAccess = FileAccess.open(GOALS_FILE_PATH, FileAccess.READ)
	if file == null:
		push_warning("Unable to open unlock goals file: %s" % GOALS_FILE_PATH)
		return

	var parsed: Variant = JSON.parse_string(file.get_as_text())
	if not (parsed is Dictionary):
		push_warning("Unlock goals root must be a Dictionary: %s" % GOALS_FILE_PATH)
		return

	var root: Dictionary = parsed
	var version: int = int(root.get("version", SCHEMA_VERSION))
	if version != SCHEMA_VERSION:
		push_warning("Unlock goals schema version %d is different from expected %d" % [version, SCHEMA_VERSION])

	var raw_goals: Variant = root.get("goals", [])
	if not (raw_goals is Array):
		push_warning("Unlock goals file has invalid 'goals' field (expected Array)")
		return

	var seen_goal_ids: Dictionary = {}
	for raw_goal in raw_goals:
		var goal: UnlockGoal = _parse_goal(raw_goal)
		if goal == null:
			continue

		var goal_key: String = String(goal.id)
		if seen_goal_ids.has(goal_key):
			push_warning("Duplicate unlock goal id skipped: '%s'" % goal_key)
			continue

		seen_goal_ids[goal_key] = true
		_goals.append(goal)

	if _goals.is_empty():
		push_warning("Unlock goals loaded, but no valid entries were found.")

func _parse_goal(raw_goal: Variant) -> UnlockGoal:
	if not (raw_goal is Dictionary):
		push_warning("Skipping unlock goal: entry is not a Dictionary")
		return null

	var goal_dict: Dictionary = raw_goal
	var goal_id: String = String(goal_dict.get("id", "")).strip_edges()
	var target_id: String = String(goal_dict.get("target_generator_id", "")).strip_edges()

	if goal_id.is_empty():
		push_warning("Skipping unlock goal: missing 'id'")
		return null
	if target_id.is_empty():
		push_warning("Skipping unlock goal '%s': missing 'target_generator_id'" % goal_id)
		return null

	var raw_requirements: Variant = goal_dict.get("requirements", [])
	if not (raw_requirements is Array):
		push_warning("Skipping unlock goal '%s': 'requirements' must be an Array" % goal_id)
		return null

	var parsed_requirements: Array[UnlockGoalRequirement] = []
	for raw_requirement in raw_requirements:
		var requirement: UnlockGoalRequirement = _parse_requirement(raw_requirement, goal_id)
		if requirement != null:
			parsed_requirements.append(requirement)

	if parsed_requirements.is_empty():
		push_warning("Skipping unlock goal '%s': no valid requirements" % goal_id)
		return null

	return UnlockGoal.new(StringName(goal_id), StringName(target_id), parsed_requirements)

func _parse_requirement(raw_requirement: Variant, goal_id: String) -> UnlockGoalRequirement:
	if not (raw_requirement is Dictionary):
		push_warning("Skipping requirement in goal '%s': entry is not a Dictionary" % goal_id)
		return null

	var requirement_dict: Dictionary = raw_requirement
	var currency_id: StringName = _parse_currency(requirement_dict.get("currency", ""))
	if currency_id == &"" or not GameState.is_known_currency_id(currency_id):
		push_warning("Skipping requirement in goal '%s': unknown currency '%s'" % [goal_id, String(requirement_dict.get("currency", ""))])
		return null

	var raw_amount: Variant = requirement_dict.get("amount", {})
	if not (raw_amount is Dictionary):
		push_warning("Skipping requirement in goal '%s': 'amount' must be a Dictionary" % goal_id)
		return null

	var amount: BigNumber = BigNumber.deserialize(raw_amount)
	if amount.mantissa < 0.0:
		push_warning("Skipping requirement in goal '%s': amount must be non-negative" % goal_id)
		return null

	return UnlockGoalRequirement.new(currency_id, amount)

func _parse_currency(raw_currency: Variant) -> StringName:
	return GameState.parse_currency_id(raw_currency)

func _get_total_currency_amount(currency_id: StringName) -> BigNumber:
	return GameState.get_total_currency_acquired_by_id(currency_id)

func _collect_known_generator_ids() -> void:
	_known_generator_ids.clear()

	var scene_root: Node = get_tree().current_scene
	var search_root: Node = scene_root if scene_root != null else self
	var generator_nodes: Array[Node] = search_root.find_children("*", "CurrencyGenerator", true, false)
	for generator_node in generator_nodes:
		var generator: CurrencyGenerator = generator_node as CurrencyGenerator
		if generator == null:
			continue

		var generator_key: String = String(generator.get_generator_id())
		if generator_key.is_empty():
			continue

		_known_generator_ids[generator_key] = true