34 lines
869 B
TypeScript
34 lines
869 B
TypeScript
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export type DropPlacement = "before" | "after";
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/** Devuelve un orden nuevo o ausencia de cambio; nunca modifica la colección recibida. */
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export function reorderItems<T>(
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items: readonly T[],
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sourceIndex: number,
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targetIndex: number,
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placement: DropPlacement
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): T[] | undefined {
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if (
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!(Number.isInteger(sourceIndex) && Number.isInteger(targetIndex)) ||
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sourceIndex < 0 ||
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targetIndex < 0 ||
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sourceIndex >= items.length ||
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targetIndex >= items.length
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) {
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return undefined;
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}
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const insertionIndex = targetIndex + (placement === "after" ? 1 : 0);
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const destination = insertionIndex - (sourceIndex < insertionIndex ? 1 : 0);
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if (sourceIndex === destination) {
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return undefined;
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}
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const next = [...items];
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const removed = next.splice(sourceIndex, 1);
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next.splice(destination, 0, ...removed);
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return next;
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}
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