extends CanvasLayer
## 2-slot hand + universal charge pool + card-time control.
##
## Canon mapping (CONCEPT.md § loop stack / § tag grammar): the build
## generates charges (auto-fire hits feed the pool — tightest
## build<->hand coupling), opening the hand stops or dilates time
## (flow -> freeze -> think -> release), charges are one universal
## currency.
##
## Two time modes, A/B-flippable live with M (playtest variant,
## operator-directed 2026-08-07 — canon ratification pending verdict):
##
## - METER (default): a Freeze charge that grows while the hand is
##   closed and drains while open. Its level maps to bands, best to
##   worst: FROZEN (true pause) -> THAW (slow-mo ramping back to full
##   speed as it drains) -> REALTIME (hand open, world at full speed)
##   -> UNAVAILABLE (empty: the hand will not open at all). Opening
##   with a full meter buys the whole ladder; opening early buys only
##   the lower bands. Prices freeze-scouting (anti-dominant-strategy)
##   and adds temporal triangularity to chains.
## - TOGGLE: unlimited freeze/dilation on Space, the original variant.
##   [ and ] step its dilation knob (0 = full freeze).
##
## Freeze uses SceneTree.paused, never Engine.time_scale = 0: probed
## on 4.7 headless — time_scale 0 still steps physics with delta 0,
## so delta-independent logic kept firing while nominally frozen.
##
## Greybox shortcut, deliberate: the two cards are entries in `cards`
## with a method each, not card resources — structured cards arrive
## with the belt (post-greybox, parked).

@export var meter_mode := true
@export var dilation_scale := 0.0
@export var dilation_step := 0.05
@export var dilation_max := 0.3
@export var kills_per_charge := 2
@export var max_charges := 5

@export_group("Salvage / card levels")
## Cumulative collected scrap gates card levels (canon 2026-08-07:
## same-currency rule — this is the run-timescale reading of the same
## scrap the meta will bank; it is NOT a separate XP).
@export var level2_salvage := 12
@export var level3_salvage := 30
## Per-level scaling, index = level - 1. Radius grows reach; power
## scales impulse/heat (HEAT at L3 reaches one-cast threshold).
@export var level_radius_scale: Array[float] = [1.0, 1.25, 1.5]
@export var level_power_scale: Array[float] = [1.0, 1.15, 1.5]

@export_group("Freeze meter")
## Seconds of open-hand time a full meter holds.
@export var meter_max := 3.0
## Meter seconds regained per real second while the hand is closed.
@export var regen_rate := 0.4
## Meter seconds spent per real second while the hand is open.
@export var drain_rate := 1.0
## Band boundaries as fractions of the full meter, ordered:
## >= band_thaw: FROZEN · >= band_realtime: THAW · >= band_unavailable:
## REALTIME · below: hand will not open.
@export var band_thaw := 0.45
@export var band_realtime := 0.18
@export var band_unavailable := 0.1
## Slowest thaw speed (time_scale at the top of the thaw band).
@export var thaw_min_scale := 0.05
## Closing the hand ramps time back to full speed over this many real
## seconds instead of snapping (applies in both modes; 0 = snap).
@export var release_thaw_s := 0.5
## In-band thaw acceleration: 1 = linear; higher hangs slow longer,
## then rushes to full speed.
@export var thaw_curve := 2.2
## Chemistry-proc hitstop length in real seconds (the hand owns time,
## so it owns the stop; capped so chain procs can't lock the world).
@export var hitstop_s := 0.08

@export_group("KINETIC card")
@export var kinetic_cost := 1
@export var kinetic_radius := 160.0
@export var kinetic_impulse := 480.0
@export var kinetic_damage := 0.5

@export_group("HEAT card")
@export var heat_cost := 1
@export var heat_radius := 140.0
@export var heat_amount := 2.0

const FX_RING := preload("res://scripts/fx_ring.gd")

var charges := 0
var hand_open := false
var meter := 0.0
var salvage_total := 0
var _kill_progress := 0
var _last_ms := 0
var _release_from := 1.0
var _release_t := -1.0
var _hitstop_t := 0.0

# Slot order is the hand: Q = slot 1, E = slot 2.
var cards: Array[Dictionary] = []


func _ready() -> void:
	add_to_group("hand")
	# The hand must keep processing (and receiving input) while the
	# world is paused for a full freeze.
	process_mode = Node.PROCESS_MODE_ALWAYS
	meter = meter_max
	_last_ms = Time.get_ticks_msec()
	cards = [
		{"name": "KINETIC", "hue": Color(0.75, 0.85, 0.95), "cost_of": func() -> int: return kinetic_cost, "play": _play_kinetic},
		{"name": "HEAT", "hue": Color(0.95, 0.55, 0.2), "cost_of": func() -> int: return heat_cost, "play": _play_heat},
	]


func _exit_tree() -> void:
	# Scene reload while frozen must never leave the world stopped.
	Engine.time_scale = 1.0
	get_tree().paused = false


func _process(_delta: float) -> void:
	# The meter runs on the wall clock: _delta is scaled by the very
	# time_scale this node is animating (and pause zeroes physics),
	# so scaled delta would freeze the meter along with the world.
	var now := Time.get_ticks_msec()
	var real_dt := clampf(float(now - _last_ms) / 1000.0, 0.0, 0.1)
	_last_ms = now

	if meter_mode:
		if hand_open:
			meter = maxf(meter - drain_rate * real_dt, 0.0)
			if meter <= 0.0:
				_set_open(false)
		else:
			meter = minf(meter + regen_rate * real_dt, meter_max)

	if Input.is_action_just_pressed("hand_toggle"):
		if hand_open:
			_set_open(false)
		elif can_open():
			_set_open(true)
	if hand_open:
		if Input.is_action_just_pressed("card_1"):
			try_play(0)
		if Input.is_action_just_pressed("card_2"):
			try_play(1)
		if meter_mode:
			# Bands shift as the meter drains under an open hand.
			_apply_time_state()

	# Release ramp: after the hand closes, time spools back up to full
	# speed on the wall clock instead of snapping.
	if not hand_open and _release_t >= 0.0:
		_release_t += real_dt
		var k := clampf(_release_t / release_thaw_s, 0.0, 1.0)
		Engine.time_scale = lerpf(_release_from, 1.0, k)
		if k >= 1.0:
			_release_t = -1.0

	# Hitstop rides on top of whatever time state is current (it can
	# only slow, never speed up); expiry re-derives the proper state.
	if _hitstop_t > 0.0:
		_hitstop_t -= real_dt
		if not get_tree().paused:
			Engine.time_scale = minf(Engine.time_scale, 0.05)
		if _hitstop_t <= 0.0:
			_apply_time_state()
	$HUD.queue_redraw()


func _input(event: InputEvent) -> void:
	if event is InputEventKey and event.pressed and not event.echo:
		match event.physical_keycode:
			KEY_BRACKETLEFT:
				dilation_scale = maxf(0.0, dilation_scale - dilation_step)
				_apply_time_state()
			KEY_BRACKETRIGHT:
				dilation_scale = minf(dilation_max, dilation_scale + dilation_step)
				_apply_time_state()
			KEY_M:
				meter_mode = not meter_mode
				_apply_time_state()


func on_kill() -> void:
	# Charges generate on kills — build-generated (the build does the
	# killing), and chemistry-chain kills feed the hand (canon 2026-08-07).
	_kill_progress += 1
	if _kill_progress >= kills_per_charge:
		_kill_progress = 0
		charges = mini(charges + 1, max_charges)


func add_salvage(value: int) -> void:
	salvage_total += value


func card_level() -> int:
	return 1 + int(salvage_total >= level2_salvage) + int(salvage_total >= level3_salvage)


func hitstop(dur := -1.0) -> void:
	_hitstop_t = minf(maxf(_hitstop_t, dur if dur > 0.0 else hitstop_s), 0.15)


func can_open() -> bool:
	return not meter_mode or meter / meter_max >= band_unavailable


func frac() -> float:
	return meter / meter_max


func try_play(slot: int) -> void:
	var card := cards[slot]
	var cost: int = card.cost_of.call()
	if charges < cost:
		return
	charges -= cost
	card.play.call()


func _set_open(open: bool) -> void:
	if open:
		_release_t = -1.0
	elif release_thaw_s > 0.0:
		# Spool up from wherever time stood: near-zero out of a freeze,
		# the current slow-mo out of a thaw, x1 out of realtime (so a
		# depletion force-close never gifts free slow-mo).
		_release_from = thaw_min_scale if get_tree().paused else Engine.time_scale
		_release_t = 0.0
	hand_open = open
	_apply_time_state()


func _apply_time_state() -> void:
	var tree := get_tree()
	if not hand_open:
		tree.paused = false
		Engine.time_scale = _release_from if _release_t >= 0.0 else 1.0
		$Dim.visible = false
		return
	$Dim.visible = true
	if meter_mode:
		var f := frac()
		if f >= band_thaw:
			tree.paused = true
			Engine.time_scale = 1.0
			_set_dim(1.0)
		elif f >= band_realtime:
			tree.paused = false
			var t := pow((band_thaw - f) / (band_thaw - band_realtime), thaw_curve)
			Engine.time_scale = clampf(t, thaw_min_scale, 1.0)
			_set_dim(1.0 - t)
		else:
			tree.paused = false
			Engine.time_scale = 1.0
			_set_dim(0.0)
	else:
		if dilation_scale == 0.0:
			tree.paused = true
			Engine.time_scale = 1.0
			_set_dim(1.0)
		else:
			tree.paused = false
			Engine.time_scale = dilation_scale
			_set_dim(0.6)


func _set_dim(k: float) -> void:
	# Dim depth doubles as the time-state telegraph: dark = frozen,
	# lifting = thawing, barely-there = realtime. Wordless.
	$Dim.color = Color(0, 0, 0, lerpf(0.08, 0.35, k))


func _mech() -> Node2D:
	return get_tree().get_first_node_in_group("mech") as Node2D


func _play_kinetic() -> void:
	# Shockwave: radial shove from M03, falling off to the rim. No aim —
	# where you're standing IS the targeting (positioning <-> build bet).
	var mech := _mech()
	if mech == null:
		return
	var lvl := card_level()
	var radius: float = kinetic_radius * level_radius_scale[lvl - 1]
	var impulse: float = kinetic_impulse * level_power_scale[lvl - 1]
	for e in get_tree().get_nodes_in_group("enemies"):
		var offset: Vector2 = e.global_position - mech.global_position
		var dist := offset.length()
		if dist > radius:
			continue
		var falloff := 1.0 - dist / radius * 0.6
		e.hit(kinetic_damage, offset.normalized() * impulse * falloff)
	_ring(mech.global_position, radius, Color(0.75, 0.85, 0.95))


func _play_heat() -> void:
	# Heat wave: paints heat on everything near M03. Heat is a status —
	# it detonates at threshold (grunt-side), and next slice's
	# KINETIC+HEAT chemistry row reads the same state.
	var mech := _mech()
	if mech == null:
		return
	var lvl := card_level()
	var radius: float = heat_radius * level_radius_scale[lvl - 1]
	var amount: float = heat_amount * level_power_scale[lvl - 1]
	for e in get_tree().get_nodes_in_group("enemies"):
		if e.global_position.distance_to(mech.global_position) <= radius:
			e.add_heat(amount)
	_ring(mech.global_position, radius, Color(0.95, 0.55, 0.2))


func _ring(at: Vector2, radius: float, color: Color) -> void:
	var ring: Node2D = FX_RING.new()
	ring.position = at
	ring.max_radius = radius
	ring.color = color
	_mech().get_parent().add_child(ring)