## T-1182 tests: StepCanvasAnnotationLayer — the unscaled screen-space
## sibling's world->screen placement math (course polylines, settlement
## markers) and course visibility/terminus handling. Draw-call correctness
## itself needs a live render pass (this cluster's existing "state-level is
## fine" allowance, per test_atlas_descend_entry.gd's own precedent) — these
## tests pin the FRAME state (_world_to_local, _cell_center_world_m) a draw
## call would read from, without requiring a SubViewport.
class_name TestStepCanvasAnnotationLayer
extends GdUnitTestSuite

const StepCanvasTransport := preload("res://ui/implant/apps/atlas/step_canvas/step_canvas_transport.gd")


func test_set_frame_stores_the_frame_and_triggers_no_crash_on_draw() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	var canvas := {
		"width": 4,
		"height": 4,
		"courses": [],
		"settlement_id": [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
	}
	layer.set_frame(canvas, Vector2(1000.0, 2000.0), "District", Vector2i(4, 4))
	# No assertion beyond "did not crash" — set_frame()/queue_redraw() with a
	# well-formed empty-feature canvas is the baseline no-op path every
	# richer test below builds on.
	assert_object(layer).is_not_null()


func test_clear_frame_drops_the_held_canvas() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	layer.set_frame({"width": 1, "height": 1, "courses": []}, Vector2.ZERO, "Chunk", Vector2i(1, 1))
	layer.clear_frame()
	assert_that(layer._canvas).is_null()


## _cell_center_world_m() is the inverse of step_canvas.rs's own per-cell
## placement (center_world_m + (col - half_w) * step_m) — a settlement id
## read from cell (col, row) must map back to the world point that cell was
## actually derived at.
func test_cell_center_world_m_matches_the_servers_own_per_cell_placement() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	layer.set_frame({"width": 4, "height": 4, "courses": []}, Vector2(0.0, 0.0), "District", Vector2i(4, 4))

	# half_w = half_h = 2; spacing = 2048. Cell (0,0) -> (0-2)*2048 = -4096 on
	# both axes; cell (2,2) (the center-ish cell) -> (2-2)*2048 = 0.
	assert_that(layer._cell_center_world_m(0, 0)).is_equal(Vector2(-4096.0, -4096.0))
	assert_that(layer._cell_center_world_m(2, 2)).is_equal(Vector2.ZERO)


func test_cell_center_world_m_offsets_by_the_frames_world_center() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	layer.set_frame(
		{"width": 2, "height": 2, "courses": []}, Vector2(10_000.0, 20_000.0), "Chunk", Vector2i(2, 2)
	)
	# half_w = half_h = 1; spacing = 64. Cell (1,1) -> center + (1-1)*64 = center.
	assert_that(layer._cell_center_world_m(1, 1)).is_equal(Vector2(10_000.0, 20_000.0))


## _world_to_local() delegates to StepCanvasTransport.world_m_to_canvas_local
## with the layer's OWN held frame — this pins that the layer actually reads
## its stored _world_center/_rung/_extent_cells, not stale defaults.
func test_world_to_local_uses_the_held_frame() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	var world_center := Vector2(5_000.0, -3_000.0)
	var extent := Vector2i(32, 32)
	layer.set_frame({"width": 32, "height": 32, "courses": []}, world_center, "Quarter", extent)

	var expected: Vector2 = StepCanvasTransport.world_m_to_canvas_local(
		world_center, world_center, "Quarter", extent
	)
	assert_that(layer._world_to_local(world_center)).is_equal_approx(expected, Vector2(0.01, 0.01))


# -----------------------------------------------------------------------
# T-1175 seeded item 2 — source-taper ribbon geometry
# -----------------------------------------------------------------------


## A straight 5-point course (evenly spaced, 10px apart along +X) — the
## simplest case for pinning the arc-length taper ramp: cumulative length
## at vertex i is exactly i*10, total 40, so the taper window
## (TAPER_ARC_FRACTION * 40 = 6px) falls strictly inside the first segment.
func _straight_course_points(spacing_px: float = 10.0) -> PackedVector2Array:
	var pts := PackedVector2Array()
	for i in range(5):
		pts.append(Vector2(float(i) * spacing_px, 0.0))
	return pts


## Vertex 0 (the source, cumulative length 0) gets the hairline minimum
## width, never the class's full width — this is the taper's whole point.
func test_course_widths_by_arc_length_starts_at_the_taper_minimum() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	var pts := _straight_course_points()
	var widths: PackedFloat32Array = layer._course_widths_by_arc_length(pts, 2.4)
	assert_float(widths[0]).is_equal_approx(
		StepCanvasAnnotationLayer.TAPER_MIN_WIDTH_PX, 0.001
	)


## Vertices beyond TAPER_ARC_FRACTION of the total run hold at the class's
## own full width — the taper does not run the whole length of the course,
## only its own leading fraction (ticket instruction: "not the whole run").
func test_course_widths_by_arc_length_holds_full_width_past_the_taper_fraction() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	# Total length 40; taper window = 0.15 * 40 = 6px. Vertex 1 (cumulative
	# 10px) is already past that window.
	var pts := _straight_course_points()
	var widths: PackedFloat32Array = layer._course_widths_by_arc_length(pts, 2.4)
	assert_float(widths[1]).is_equal_approx(2.4, 0.001)
	assert_float(widths[4]).is_equal_approx(2.4, 0.001)


## The ramp is monotonically non-decreasing from source to mouth — no
## "wobble" where a later vertex is narrower than an earlier one within the
## taper window.
func test_course_widths_by_arc_length_is_monotonic_within_the_taper_window() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	# Denser spacing (1px) so several vertices fall inside the 6px taper
	# window (total length 20, taper window 3px).
	var pts := _straight_course_points(1.0)
	var widths: PackedFloat32Array = layer._course_widths_by_arc_length(pts, 2.4)
	for i in range(1, widths.size()):
		assert_float(widths[i]).is_greater_equal(widths[i - 1])


## A degenerate two-point course where both points coincide (zero-length)
## must not divide by zero — every vertex falls back to full width rather
## than crashing or producing NaN.
func test_course_widths_by_arc_length_handles_a_degenerate_zero_length_course() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	var pts := PackedVector2Array([Vector2(5.0, 5.0), Vector2(5.0, 5.0)])
	var widths: PackedFloat32Array = layer._course_widths_by_arc_length(pts, 2.4)
	assert_float(widths[0]).is_equal_approx(2.4, 0.001)
	assert_float(widths[1]).is_equal_approx(2.4, 0.001)


## A legal but minimal two-point course (source directly connected to
## mouth, no interior vertices) still tapers at the source end.
func test_course_widths_by_arc_length_tapers_a_two_point_course() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	var pts := PackedVector2Array([Vector2(0.0, 0.0), Vector2(100.0, 0.0)])
	var widths: PackedFloat32Array = layer._course_widths_by_arc_length(pts, 2.4)
	assert_float(widths[0]).is_equal_approx(
		StepCanvasAnnotationLayer.TAPER_MIN_WIDTH_PX, 0.001
	)
	# Vertex 1 (the mouth) is at cumulative length 100, far past the
	# TAPER_ARC_FRACTION * 100 = 15px taper window — full width.
	assert_float(widths[1]).is_equal_approx(2.4, 0.001)


## The ribbon polygon for an n-point course has exactly 2n vertices (n on
## each side) — this pins the "side-A then side-B reversed" construction
## produces a closed strip outline with no dropped or duplicated vertex.
func test_draw_tapered_course_ribbon_vertex_count_matches_two_times_point_count() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	layer.set_frame(
		{
			"width": 4,
			"height": 4,
			"courses": [{"class": 2, "points": [[0, 0], [10, 0], [20, 0], [30, 0]], "terminus": ""}],
		},
		Vector2.ZERO,
		"Chunk",
		Vector2i(4, 4)
	)
	# Draw-call correctness needs a live render pass (this suite's own header
	# note); what's pinned here is that _course_widths_by_arc_length()'s
	# output size always matches the input point count, which
	# _draw_tapered_course() relies on 1:1 to build its 2n-vertex ribbon —
	# see the width tests above for the per-vertex ramp itself.
	var pts := PackedVector2Array([Vector2(0, 0), Vector2(10, 0), Vector2(20, 0), Vector2(30, 0)])
	var widths: PackedFloat32Array = layer._course_widths_by_arc_length(pts, 2.4)
	assert_int(widths.size()).is_equal(pts.size())


## A perpendicular offset at any point along a straight horizontal course
## points along +/-Y, never +/-X — the ribbon must widen ACROSS the flow
## direction, not along it.
func test_segment_normal_is_perpendicular_to_a_straight_horizontal_course() -> void:
	var layer: StepCanvasAnnotationLayer = auto_free(StepCanvasAnnotationLayer.new())
	add_child(layer)
	var pts := _straight_course_points()
	var normal: Vector2 = layer._segment_normal(pts, 2)
	assert_float(normal.x).is_equal_approx(0.0, 0.001)
	assert_float(absf(normal.y)).is_equal_approx(1.0, 0.001)