package world

// decorationSource is a source chunk whose feature pass may inspect or write a
// target chunk. Vanilla FEATURES has a one-chunk block-state write radius.
type decorationSource struct {
	X, Z int32
}

// decorationSources returns source chunks in deterministic X-major/Z-minor
// order. Replaying all nine against one mutable 3x3 terrain region makes target
// output independent of cache request order while preserving each source's own
// decoration seed and placement origin.
func decorationSources(targetX, targetZ int32) []decorationSource {
	sources := make([]decorationSource, 0, 9)
	for sourceX := targetX - 1; sourceX <= targetX+1; sourceX++ {
		for sourceZ := targetZ - 1; sourceZ <= targetZ+1; sourceZ++ {
			sources = append(sources, decorationSource{X: sourceX, Z: sourceZ})
		}
	}
	return sources
}