## T-1142 (Jeroen's second/third hands-on findings): pure-function tests for
## AtlasWindowViewer's fit-and-center math (fit_window_view) and pole-wall
## pan clamp (clamp_pan_offset_to_pole_wall) — both extracted specifically so
## the "viewport + n -> zoom/offset" transform is unit-testable without a
## live Control tree.
class_name TestAtlasWindowGeometry
extends GdUnitTestSuite

const AtlasWindowGeometry := preload("res://ui/implant/apps/atlas/atlas_window_geometry.gd")
const AtlasDescendGeometry := preload("res://ui/implant/apps/atlas/atlas_descend_geometry.gd")

const MIN_ZOOM: float = 0.5
const MAX_ZOOM: float = 8.0
const CELL_PIXEL_SIZE: float = 16.0


# =============================================================================
# fit_window_view — the "postage stamp" fix (item 2)
# =============================================================================


## n=32, cell_px=16 -> native composite is 512x512. A 1920x1080 viewport's
## smaller dimension is 1080, so zoom = 0.9 * 1080 / 512 ~= 1.898 — well
## inside [MIN_ZOOM, MAX_ZOOM], so the clamp is a no-op here.
func test_fit_window_view_computes_expected_zoom_for_a_wide_viewport() -> void:
	var fit: Dictionary = AtlasWindowGeometry.fit_window_view(
		Vector2(1920.0, 1080.0), 32, CELL_PIXEL_SIZE, MIN_ZOOM, MAX_ZOOM
	)
	var expected_zoom: float = 0.9 * 1080.0 / 512.0
	assert_float(fit["zoom"]).is_equal_approx(expected_zoom, 0.001)


## The composite must be CENTERED — offset.x/.y each leave an equal margin on
## both sides of the (n*cell_px*zoom)-sized composite.
func test_fit_window_view_centers_the_composite() -> void:
	var viewport := Vector2(1920.0, 1080.0)
	var fit: Dictionary = AtlasWindowGeometry.fit_window_view(
		viewport, 32, CELL_PIXEL_SIZE, MIN_ZOOM, MAX_ZOOM
	)
	var composite_scaled: float = 32.0 * CELL_PIXEL_SIZE * float(fit["zoom"])
	var offset: Vector2 = fit["offset"]
	# The composite's right/bottom edge is offset + composite_scaled — the
	# margin on the far side must equal the margin on the near side (offset).
	var right_margin: float = viewport.x - (offset.x + composite_scaled)
	var bottom_margin: float = viewport.y - (offset.y + composite_scaled)
	assert_float(right_margin).is_equal_approx(offset.x, 0.01)
	assert_float(bottom_margin).is_equal_approx(offset.y, 0.01)


## Jeroen's exact bug: an n=32 composite (512px native) in a real ~1920px
## viewport must NOT render at zoom=1.0 (the old, unfitted "postage stamp"
## behavior) — the fit must scale it up to fill most of the smaller
## viewport dimension.
func test_fit_window_view_scales_up_a_small_composite_to_fill_the_viewport() -> void:
	var fit: Dictionary = AtlasWindowGeometry.fit_window_view(
		Vector2(1920.0, 1080.0), 32, CELL_PIXEL_SIZE, MIN_ZOOM, MAX_ZOOM
	)
	assert_float(fit["zoom"]).override_failure_message(
		"a 512px composite in a 1920x1080 viewport must be scaled UP, not left at 1.0"
	).is_greater(1.0)


## A huge n (e.g. n=64 at a tiny viewport) must clamp to MIN_ZOOM, never
## shrink the composite into illegibility below the floor.
func test_fit_window_view_clamps_to_min_zoom_for_a_tiny_viewport() -> void:
	var fit: Dictionary = AtlasWindowGeometry.fit_window_view(
		Vector2(200.0, 150.0), 64, CELL_PIXEL_SIZE, MIN_ZOOM, MAX_ZOOM
	)
	assert_float(fit["zoom"]).is_equal_approx(MIN_ZOOM, 0.001)


## A small n (e.g. n=2) at a huge viewport must clamp to MAX_ZOOM, never
## scale past the ceiling.
func test_fit_window_view_clamps_to_max_zoom_for_a_tiny_composite() -> void:
	var fit: Dictionary = AtlasWindowGeometry.fit_window_view(
		Vector2(3840.0, 2160.0), 2, CELL_PIXEL_SIZE, MIN_ZOOM, MAX_ZOOM
	)
	assert_float(fit["zoom"]).is_equal_approx(MAX_ZOOM, 0.001)


## Degenerate inputs (zero viewport, zero n) must not divide by zero — a safe
## fallback (zoom=1.0, offset=ZERO), never a crash or NaN.
func test_fit_window_view_degenerate_inputs_are_safe() -> void:
	var fit_zero_viewport: Dictionary = AtlasWindowGeometry.fit_window_view(
		Vector2.ZERO, 32, CELL_PIXEL_SIZE, MIN_ZOOM, MAX_ZOOM
	)
	assert_float(fit_zero_viewport["zoom"]).is_equal_approx(1.0, 0.001)
	var fit_zero_n: Dictionary = AtlasWindowGeometry.fit_window_view(
		Vector2(1920.0, 1080.0), 0, CELL_PIXEL_SIZE, MIN_ZOOM, MAX_ZOOM
	)
	assert_float(fit_zero_n["zoom"]).is_equal_approx(1.0, 0.001)


# =============================================================================
# clamp_pan_offset_to_pole_wall — item 5 (pole hard wall, row axis only)
# =============================================================================


## Deep inside the valid range (window nowhere near a pole), the clamp must
## be a no-op — offset passes through unchanged.
func test_pole_wall_clamp_is_a_noop_far_from_the_poles() -> void:
	var offset := Vector2(10.0, 20.0)
	var clamped: Vector2 = AtlasWindowGeometry.clamp_pan_offset_to_pole_wall(
		offset, Vector2(1920.0, 1080.0), Vector2i(0, 0), 32, 4785, CELL_PIXEL_SIZE, 1.0
	)
	assert_that(clamped).is_equal(offset)


## X is NEVER clamped by the pole wall (item 6: east-west is seamless) — even
## an absurdly large X offset passes through untouched.
func test_pole_wall_clamp_never_touches_x() -> void:
	var offset := Vector2(999999.0, 0.0)
	var clamped: Vector2 = AtlasWindowGeometry.clamp_pan_offset_to_pole_wall(
		offset, Vector2(1920.0, 1080.0), Vector2i(0, 0), 32, 4785, CELL_PIXEL_SIZE, 1.0
	)
	assert_float(clamped.x).is_equal_approx(999999.0, 0.001)


## The core pole-wall behavior: dragging FAR past the north pole (offset.y
## driven to an extreme) must clamp — the resulting offset must be LESS than
## the extreme requested, and a SECOND, even-more-extreme drag must produce
## the SAME clamped value (further dragging is inert once pinned at the wall).
func test_pole_wall_clamp_pins_offset_when_dragged_past_the_pole() -> void:
	var rows_half := 100
	var held_center := Vector2i(0, 90)  # near the south pole already (row 90 of 100)
	var extreme_offset := Vector2(0.0, 5000.0)  # a huge downward drag
	var clamped: Vector2 = AtlasWindowGeometry.clamp_pan_offset_to_pole_wall(
		extreme_offset, Vector2(800.0, 800.0), held_center, 32, rows_half, CELL_PIXEL_SIZE, 1.0
	)
	assert_float(clamped.y).override_failure_message(
		"an extreme drag toward the pole must be clamped, not pass through"
	).is_less(extreme_offset.y)

	var even_more_extreme := Vector2(0.0, 50000.0)
	var clamped_again: Vector2 = AtlasWindowGeometry.clamp_pan_offset_to_pole_wall(
		even_more_extreme, Vector2(800.0, 800.0), held_center, 32, rows_half, CELL_PIXEL_SIZE, 1.0
	)
	assert_float(clamped_again.y).override_failure_message(
		"further dragging past an already-pinned wall must be inert (same clamped value)"
	).is_equal_approx(clamped.y, 0.01)


## Symmetric check on the north side: a huge UPWARD drag near the north pole
## also clamps.
func test_pole_wall_clamp_pins_offset_on_the_north_side_too() -> void:
	var rows_half := 100
	var held_center := Vector2i(0, -90)  # near the north pole
	var extreme_offset := Vector2(0.0, -5000.0)  # a huge upward drag
	var clamped: Vector2 = AtlasWindowGeometry.clamp_pan_offset_to_pole_wall(
		extreme_offset, Vector2(800.0, 800.0), held_center, 32, rows_half, CELL_PIXEL_SIZE, 1.0
	)
	assert_float(clamped.y).override_failure_message(
		"an extreme drag toward the north pole must be clamped"
	).is_greater(extreme_offset.y)


## rows_half <= 0 (a no-radius body, or a degenerate district_extent()) means
## "no wall concept" — the clamp is a no-op, matching
## canonicalize_district_center()'s own no-radius identity disposition.
func test_pole_wall_clamp_is_noop_when_rows_half_is_zero() -> void:
	var offset := Vector2(0.0, 999999.0)
	var clamped: Vector2 = AtlasWindowGeometry.clamp_pan_offset_to_pole_wall(
		offset, Vector2(800.0, 800.0), Vector2i(0, 0), 32, 0, CELL_PIXEL_SIZE, 1.0
	)
	assert_that(clamped).is_equal(offset)


## Tiny-body edge case (documented open item in atlas_window_viewer.gd's own
## _clamp_offset_to_pole_wall doc): a window TALLER than the whole planet's
## row span (n=64 window, rows_half=10 -> pole-to-pole is only 20 districts)
## must not crash or produce an inverted/degenerate clamp range — the offset
## still comes back as a finite Vector2, and repeated extreme drags still
## converge to a stable pinned value (not NaN, not unbounded).
func test_pole_wall_clamp_handles_a_window_taller_than_the_planet() -> void:
	var rows_half := 10
	var held_n := 64
	var held_center := Vector2i(0, 0)
	var clamped: Vector2 = AtlasWindowGeometry.clamp_pan_offset_to_pole_wall(
		Vector2(0.0, 999999.0), Vector2(800.0, 800.0), held_center, held_n, rows_half,
		CELL_PIXEL_SIZE, 1.0
	)
	assert_bool(is_finite(clamped.y)).override_failure_message(
		"a window taller than the planet's row span must still produce a finite clamp"
	).is_true()
	var clamped_again: Vector2 = AtlasWindowGeometry.clamp_pan_offset_to_pole_wall(
		Vector2(0.0, 9999999.0), Vector2(800.0, 800.0), held_center, held_n, rows_half,
		CELL_PIXEL_SIZE, 1.0
	)
	assert_float(clamped_again.y).is_equal_approx(clamped.y, 0.01)


# =============================================================================
# Cross-check: clamp bounds derived from district_extent() (the SAME source
# canonicalize_district_center() uses) — confirms the two T-1142 fixes (item
# 5 pole wall, item 6a wrap/clamp) agree on what "the pole" even is.
# =============================================================================


func test_pole_wall_rows_half_matches_canonicalize_rows_half() -> void:
	var radius_km := 6238.4  # GJ380c
	var extent: Dictionary = AtlasDescendGeometry.district_extent(radius_km)
	var rows_half: int = int(extent["rows_half"])
	# A center exactly at (0, rows_half) must canonicalize to itself (already
	# at the pole boundary, not past it) — pins that the SAME rows_half both
	# fixes consume describes an inclusive boundary, not an exclusive one.
	var canonical: Vector2i = AtlasDescendGeometry.canonicalize_district_center(
		Vector2i(0, rows_half), radius_km
	)
	assert_int(canonical.y).is_equal(rows_half)