extends SceneTree
## Terrain edge check, for several seeds: in the band just inside the boundary
## wall there must be (1) no water deeper than you can wade out of, and (2) no
## water without a bank, i.e. ground that drops away outward. The inland water
## surface stops at the wall, so unbanked water hangs in the air over the drop.
## This is the bug where the player fell into floating water by the sea cliff.
## Shallow ponds at the foot of the mountains are fine: the slope holds them.
##
## Run: godot --headless --path . --script res://tests/test_terrain_edges.gd

const BAND := 10.0            # metres inside the wall to check
const MAX_EDGE_DEPTH := 1.0   # deepest allowed water near the edge (wadeable)
const BANK_CHECK := 12.0      # how far outward the bank must rise above water

## The original island plus a spread of other seeds: new worlds get random
## seeds, so the edge rule has to hold for any of them.
const SEEDS := [1337, 1, 42, 777, 4242, 9001, 31337, 123456]

func _initialize() -> void:
	_all.call_deferred()

func _all() -> void:
	var failed := 0
	for s in SEEDS:
		var terrain: Node3D = load("res://scripts/world/terrain.gd").new()
		terrain.noise_seed = s
		root.add_child(terrain)   # builds in _ready
		var bad := _check(terrain)
		print("seed %6d: %s" % [s, "ok" if bad == 0 else "%d bad samples" % bad])
		if bad > 0:
			failed += 1
		terrain.free()
	print("RESULT: %s (%d/%d seeds clean)" % ["PASS" if failed == 0 else "FAIL", SEEDS.size() - failed, SEEDS.size()])
	quit(1 if failed > 0 else 0)

func _check(terrain: Node3D) -> int:
	var bad := 0
	var worst := INF
	var worst_at := Vector2.ZERO
	var half: float = terrain.size * 0.5
	var x := -half
	while x < half:
		var z := -half
		while z < half:
			if terrain.inside_boundary(x, z, 0.0) and not terrain.inside_boundary(x, z, BAND):
				var h: float = terrain.sample_height(x, z)
				# Hazard 1: a pit too deep to wade out of near the edge.
				var too_deep: bool = h < terrain.water_level - MAX_EDGE_DEPTH
				# Hazard 2: water that isn't held in by a bank. The inland water
				# surface stops at the wall, so wet ground must rise again just
				# outward, or the water edge hangs over a drop.
				var unbanked := false
				if h < terrain.water_level:
					var out := Vector2(x, z).normalized() * BANK_CHECK
					unbanked = terrain.sample_height(x + out.x, z + out.y) < terrain.water_level
				if too_deep or unbanked:
					bad += 1
					if h < worst:
						worst = h
						worst_at = Vector2(x, z)
			z += 1.0
		x += 1.0
	if bad > 0:
		print("  lowest %.1f m at (%.0f, %.0f), sea weight %.2f" % [
			worst, worst_at.x, worst_at.y, terrain.sea_weight(worst_at.x, worst_at.y)])
	return bad