class_name Block
extends AnimatableBody2D
## One arc-shaped segment of a ring around the core. Its [enum Kind] decides how it looks,
## how many hits it takes and what it does to the ball.

## Emitted when a TNT segment breaks; the rings turn it into an explosion.
signal detonated(block: Block)

enum Kind { NORMAL, INDESTRUCTIBLE, WATER, ICE, TNT, RUBBER, GHOST, MOSS, MAGNET }

## What [method strike] did, so the game can pick a sound.
enum Hit { BROKE, DAMAGED, BLOCKED }

const GAP := 4.0 # px between neighbouring tiles
const CORNER := 4.0 # corner rounding radius in px
const BREAK_SECONDS := 0.15 # fade-out time, after a short flash

## Per kind: first level it can appear, hits to break (0 = unbreakable) and flat colour.
## Normal segments get a random blue-green colour instead.
const KINDS := {
	Kind.NORMAL: { unlock = 0, hp = 1, color = Params.COLOR_BLUE },
	Kind.INDESTRUCTIBLE: { unlock = 0, hp = 0, color = Params.COLOR_ORANGE },
	Kind.WATER: { unlock = 50, hp = 3, color = Color("#3a7bff") },
	Kind.ICE: { unlock = 100, hp = 2, color = Color("#d6f3ff") },
	Kind.TNT: { unlock = 150, hp = 1, color = Params.COLOR_PINK },
	Kind.RUBBER: { unlock = 200, hp = 2, color = Color("#ae81ff") },
	Kind.GHOST: { unlock = 250, hp = 1, color = Color("#c8c3d8") },
	Kind.MOSS: { unlock = 300, hp = 1, color = Params.COLOR_GREEN },
	Kind.MAGNET: { unlock = 350, hp = 2, color = Color("#9aa4ad") },
}

const WATER_STICK_SECONDS := 0.35
const WATER_SLOWDOWN := 0.85
const ICE_SPEEDUP := 1.08
const RUBBER_SPEEDUP := 1.15
const GHOST_SOLID_SECONDS := 2.0
const GHOST_PHASED_SECONDS := 1.2
const MOSS_REGROW_SECONDS := 8.0 # moss grows back once, this long after breaking
const MAGNET_RADIUS := 150.0
const MAGNET_PULL := 700.0 # px/s² at the segment, fading to 0 at MAGNET_RADIUS

var kind := Kind.NORMAL
var hp := 1
var color := Params.COLOR_BLUE
var _inner := 0.0
var _outer := 0.0
var _begin := 0.0
var _end := 0.0
var _polygon := PackedVector2Array()
var _collision := CollisionPolygon2D.new()
var _cracks := PackedVector2Array()
var _ghost_clock := 0.0
var _regrown := false
## 0 to 1: how far the tile is washed towards white while breaking.
var _flash := 0.0:
	set(value):
		_flash = value
		queue_redraw()


func _init(inner: float, outer: float, begin: float, end: float, segment_kind: Kind) -> void:
	sync_to_physics = false
	collision_layer = Params.LAYER_BLOCKS
	collision_mask = 0
	_inner = inner
	_outer = outer
	_begin = begin
	_end = end
	add_child(_collision)
	set_kind(segment_kind)
	_ghost_clock = randf() * (GHOST_SOLID_SECONDS + GHOST_PHASED_SECONDS)


func set_kind(value: Kind) -> void:
	kind = value
	hp = KINDS[kind].hp
	if kind == Kind.NORMAL:
		color = Color8(
			int(102 * (randf() / 5.0 + 0.5)),
			int(217 * (randf() / 5.0 + 0.5)),
			int(239 * (randf() / 5.0 + 0.5)))
	else:
		color = KINDS[kind].color
	_rebuild_shape()
	set_physics_process(kind == Kind.GHOST or kind == Kind.MAGNET)


func is_breakable() -> bool:
	return hp > 0


## Centre of the segment in global coordinates.
func center() -> Vector2:
	var middle := (_begin + _end) / 2.0
	return to_global(Vector2(sin(middle), cos(middle)) * (_inner + _outer) / 2.0)


## A ball hit the segment. Applies the segment's effect on the ball and takes a hit.
func strike(ball: Ball) -> Hit:
	if not is_breakable():
		if ball.superball:
			ball.superball = false
			destroy()
			return Hit.BROKE
		return Hit.BLOCKED
	if ball.fire:
		# Fire burns straight through whatever the segment is.
		hp = 1
		return damage()
	match kind:
		Kind.ICE:
			ball.velocity *= ICE_SPEEDUP
		Kind.RUBBER:
			ball.velocity *= RUBBER_SPEEDUP
	var result := damage()
	if kind == Kind.WATER and result == Hit.DAMAGED:
		ball.stick_to(self, WATER_STICK_SECONDS, WATER_SLOWDOWN)
	return result


## Takes one hit from anything (ball, laser, explosion). Unbreakable segments ignore it.
func damage() -> Hit:
	if not is_breakable() or collision_layer == 0:
		return Hit.BLOCKED
	hp -= 1
	if hp > 0:
		_rebuild_shape()
		return Hit.DAMAGED
	destroy()
	return Hit.BROKE


## Flashes and fades out. Stops colliding right away. Moss comes back once, after a while.
func destroy() -> void:
	collision_layer = 0
	if kind == Kind.TNT:
		detonated.emit(self)
	var tween := create_tween()
	tween.tween_property(self, "_flash", 0.8, BREAK_SECONDS / 3.0)
	tween.tween_property(self, "modulate:a", 0.0, BREAK_SECONDS)
	tween.parallel().tween_property(self, "scale", Vector2.ONE * 1.04, BREAK_SECONDS)
	if kind == Kind.MOSS and not _regrown:
		tween.tween_interval(MOSS_REGROW_SECONDS)
		tween.tween_callback(_regrow)
	else:
		tween.tween_callback(queue_free)


func _regrow() -> void:
	_regrown = true
	hp = KINDS[kind].hp
	_flash = 0.0
	scale = Vector2.ONE * 0.6
	var tween := create_tween().set_parallel()
	tween.tween_property(self, "modulate:a", 1.0, 0.4)
	tween.tween_property(self, "scale", Vector2.ONE, 0.4)
	tween.chain().tween_callback(set.bind("collision_layer", Params.LAYER_BLOCKS))


func _physics_process(delta: float) -> void:
	if kind == Kind.GHOST and hp > 0:
		_ghost_clock = fmod(_ghost_clock + delta, GHOST_SOLID_SECONDS + GHOST_PHASED_SECONDS)
		var solid := _ghost_clock < GHOST_SOLID_SECONDS
		collision_layer = Params.LAYER_BLOCKS if solid else 0
		modulate.a = 1.0 if solid else 0.2
	elif kind == Kind.MAGNET and collision_layer != 0:
		var here := center()
		for ball: Ball in get_tree().get_nodes_in_group("balls"):
			var offset := here - ball.global_position
			var dist := offset.length()
			if dist > 0.0 and dist < MAGNET_RADIUS:
				ball.velocity += offset / dist * MAGNET_PULL * (1.0 - dist / MAGNET_RADIUS) * delta


## Recomputes the drawn and collision outline. Water drains from the outside in as it is hit;
## ice gets cracks; other multi-hit segments darken.
func _rebuild_shape() -> void:
	var outer := _outer
	var max_hp: int = KINDS[kind].hp
	if kind == Kind.WATER and hp < max_hp:
		outer = _inner + (_outer - _inner) * float(hp) / max_hp
	_polygon = _round_corners(_sector(_inner + GAP / 2.0, outer - GAP / 2.0, _begin, _end, GAP / 2.0))
	# Very short segments can leave a sliver too thin to split into convex pieces; skip its
	# collision rather than let Godot fail on it.
	var valid := not Geometry2D.decompose_polygon_in_convex(_polygon).is_empty()
	_collision.set_deferred("polygon", _polygon if valid else PackedVector2Array())
	_collision.set_deferred("disabled", not valid)
	_cracks = PackedVector2Array()
	if kind == Kind.ICE and hp < max_hp:
		_cracks = _crack_lines()
	queue_redraw()


func _crack_lines() -> PackedVector2Array:
	var lines := PackedVector2Array()
	var middle := (_begin + _end) / 2.0
	var radius := (_inner + _outer) / 2.0
	var start := Vector2(sin(middle), cos(middle)) * radius
	for i in 3:
		var angle := middle + randf_range(-0.6, 0.6) * (_end - _begin) / 2.0
		var r := lerpf(_inner + GAP, _outer - GAP, randf())
		lines.append(start)
		lines.append(Vector2(sin(angle), cos(angle)) * r)
	return lines


func _draw() -> void:
	if _polygon.size() < 3:
		return # segment too short to show at all
	var fill := color
	if hp > 0 and hp < KINDS[kind].hp and kind != Kind.WATER and kind != Kind.ICE:
		fill = fill.darkened(0.25)
	fill = fill.lerp(Color.WHITE, _flash)
	draw_colored_polygon(_polygon, fill)
	# Polygons have no antialiasing of their own; a smooth outline softens the edge.
	var outline := _polygon.duplicate()
	outline.append(_polygon[0])
	draw_polyline(outline, fill, 1.0, true)
	if not _cracks.is_empty():
		draw_multiline(_cracks, Color(0.2, 0.35, 0.45, 0.9), 1.5, true)


## Ring segment between two radii. [param gap] trims each side by that many pixels,
## so the space between neighbours has the same width at every radius. An edge too short
## to trim collapses to a point, turning the segment into a wedge.
static func _sector(inner: float, outer: float, begin: float, end: float, gap: float) -> PackedVector2Array:
	var steps := maxi(2, int((end - begin) * sqrt(outer) / 1.5))
	return _trimmed_arc(outer, begin, end, gap, steps) + _trimmed_arc(inner, end, begin, -gap, steps)


static func _trimmed_arc(radius: float, from: float, to: float, gap: float, steps: int) -> PackedVector2Array:
	var trim := gap / radius
	if (to - from - 2.0 * trim) * signf(to - from) <= 0.0:
		var middle := (from + to) / 2.0
		return PackedVector2Array([Vector2(sin(middle), cos(middle)) * radius])
	return _arc(radius, from + trim, to - trim, steps)


## Shrinks then regrows the polygon with round joins, which rounds its corners.
static func _round_corners(polygon: PackedVector2Array) -> PackedVector2Array:
	var shrunk := Geometry2D.offset_polygon(polygon, -CORNER)
	if shrunk.is_empty():
		return polygon
	var rounded := Geometry2D.offset_polygon(shrunk[0], CORNER, Geometry2D.JOIN_ROUND)
	return polygon if rounded.is_empty() else _without_duplicates(rounded[0])


## offset_polygon can emit repeated points; zero-length edges break convex decomposition.
static func _without_duplicates(polygon: PackedVector2Array) -> PackedVector2Array:
	var result := PackedVector2Array()
	for point in polygon:
		if result.is_empty() or not point.is_equal_approx(result[-1]):
			result.append(point)
	if result.size() > 1 and result[0].is_equal_approx(result[-1]):
		result.remove_at(result.size() - 1)
	return result


static func _arc(radius: float, from: float, to: float, steps: int) -> PackedVector2Array:
	var points := PackedVector2Array()
	for i in steps + 1:
		var angle := lerpf(from, to, float(i) / steps)
		points.append(Vector2(sin(angle), cos(angle)) * radius)
	return points