extends "res://scripts/building/piece.gd"
## A snap-together building piece: wood floor, wall, roof, gable or door frame.
##
## Geometry lives here (not in items.json) because it has to match the meshes
## in item_meshes.gd exactly:
## - `shapes`: the colliders, also used (shrunk slightly) for overlap checks.
## - `snaps`: snap points in local space. Two pieces are connected when a snap
##   point of one coincides with a snap point of the other; build_system.gd
##   uses that for snapping and for structural support.
## - `center`: rough centre of mass, used to tell vertical from sideways
##   support.
##
## All pieces are 2 m on a side so they line up on a 2 m grid.
## Origins: floor = centre of the top surface; wall, door and gable = bottom
## centre; roof = centre of the low edge, rising 1 m over 2 m toward -Z
## (about 27 degrees), so two roofs from opposite walls of a 4 m hut meet at a
## ridge.

const BUILD_LAYER := 4                ## physics layer 3: shelter + regrowth queries
const ROOF_ANGLE := 0.4636476         ## atan(1 / 2)
const ROOF_T := 0.12                  ## roof panel thickness

static var _kinds := {}

var kind := "wall"
var support := 1.0                    ## 0..1, set by build_system.gd
var grounded := false

static func kinds() -> Dictionary:
	if _kinds.is_empty():
		_kinds = _define()
	return _kinds

static func _define() -> Dictionary:
	var k := {}
	var wall_snaps := [
		Vector3(-1, 0, 0), Vector3(0, 0, 0), Vector3(1, 0, 0),
		Vector3(-1, 2, 0), Vector3(0, 2, 0), Vector3(1, 2, 0)]
	k["floor"] = {
		"shapes": [_box(Vector3(0, -0.1, 0), Vector3(2, 0.2, 2))],
		"snaps": [Vector3(-1, 0, -1), Vector3(0, 0, -1), Vector3(1, 0, -1), Vector3(-1, 0, 0), Vector3(1, 0, 0),
			Vector3(-1, 0, 1), Vector3(0, 0, 1), Vector3(1, 0, 1)],
		"center": Vector3(0, -0.1, 0),
	}
	k["wall"] = {
		"shapes": [_box(Vector3(0, 1, 0), Vector3(2, 2, 0.2))],
		"snaps": wall_snaps,
		"center": Vector3(0, 1, 0),
	}
	# Door frame: 1.1 m x 1.9 m opening (the player is 0.8 m x 1.8 m).
	k["door"] = {
		"shapes": [_box(Vector3(-0.775, 1, 0), Vector3(0.45, 2, 0.2)), _box(Vector3(0.775, 1, 0), Vector3(0.45, 2, 0.2)),
			_box(Vector3(0, 1.95, 0), Vector3(1.1, 0.1, 0.2))],
		"snaps": wall_snaps,
		"center": Vector3(0, 1, 0),
	}
	# Gable: right triangle, 0 m tall at -X, 1 m at +X (fills the end of a
	# roof; rotate 180 degrees for the other half).
	k["gable"] = {
		"shapes": [_prism([Vector2(-1, 0), Vector2(1, 0), Vector2(1, 1)], 0.2)],
		"snaps": [Vector3(-1, 0, 0), Vector3(0, 0, 0), Vector3(1, 0, 0), Vector3(1, 1, 0)],
		"center": Vector3(0.33, 0.33, 0),
	}
	var n := Vector3(0, cos(ROOF_ANGLE), sin(ROOF_ANGLE))   # panel normal (up and out)
	# (Ends exactly at the ridge. The seam where two roofs meet is handled by
	# build_system.roofed_at sampling several rays.)
	k["roof"] = {
		"shapes": [{"type": "box", "center": Vector3(0, 0.5, -1) + n * ROOF_T * 0.5,
			"size": Vector3(2, ROOF_T, sqrt(5.0)), "basis": Basis(Vector3.RIGHT, ROOF_ANGLE)}],
		"snaps": [Vector3(-1, 0, 0), Vector3(0, 0, 0), Vector3(1, 0, 0),
			Vector3(-1, 1, -2), Vector3(0, 1, -2), Vector3(1, 1, -2)],
		"center": Vector3(0, 0.5, -1),
	}
	return k

static func _box(c: Vector3, s: Vector3) -> Dictionary:
	return {"type": "box", "center": c, "size": s, "basis": Basis()}

## A prism: a 2D outline in the XY plane, extruded `t` along Z (centred).
static func _prism(outline: Array, t: float) -> Dictionary:
	return {"type": "prism", "outline": outline, "thickness": t}

## Builds a Shape3D for one shape entry, shrunk by `margin` on every side
## (margin > 0 is for overlap tests, so touching neighbours don't count).
## Returns [shape, local transform].
static func make_shape(s: Dictionary, margin: float = 0.0) -> Array:
	if s.type == "box":
		var b := BoxShape3D.new()
		var size: Vector3 = s.size
		b.size = Vector3(maxf(size.x - margin * 2.0, 0.02), maxf(size.y - margin * 2.0, 0.02), maxf(size.z - margin * 2.0, 0.02))
		return [b, Transform3D(s.basis, s.center)]
	var outline: Array = s.outline
	var c := Vector2.ZERO
	for p in outline:
		c += p
	c /= outline.size()
	var pts := PackedVector3Array()
	var hz := maxf(float(s.thickness) * 0.5 - margin, 0.01)
	for p: Vector2 in outline:
		var q := p
		if margin > 0.0:
			q = c + (p - c) * (1.0 - margin * 2.0 / maxf((p - c).length(), 0.01))
		pts.append(Vector3(q.x, q.y, -hz))
		pts.append(Vector3(q.x, q.y, hz))
	var cv := ConvexPolygonShape3D.new()
	cv.points = pts
	return [cv, Transform3D()]

static func is_build(def: Dictionary) -> bool:
	return def.has("place") and def.place.has("kind")

func _make_collision(_mi: MeshInstance3D) -> void:
	kind = def.place.kind
	collision_layer = 1 | BUILD_LAYER
	add_to_group("build")
	for s in kinds()[kind].shapes:
		var made := make_shape(s)
		var cs := CollisionShape3D.new()
		cs.shape = made[0]
		cs.transform = made[1]
		add_child(cs)

func snap_points() -> Array:
	var out := []
	for p in kinds()[kind].snaps:
		out.append(global_transform * p)
	return out

func display_name() -> String:
	return ItemDB.item_name(item_id)

func interact_prompt(_player: Node) -> String:
	if support < 0.999:
		return "%s  (support %d%%)" % [display_name(), roundi(support * 100.0)]
	return display_name()