import type { AnsiCode } from "./tokenize.js";
import { undoAnsiCodes } from "./undo.js";

/**
 * Returns the minimum amount of ANSI codes necessary to get from the compound style `from` to `to`.
 * Both `from` and `to` are expected to be reduced.
 */
export function diffAnsiCodes(from: AnsiCode[], to: AnsiCode[]): AnsiCode[] {
	const endCodesInTo = new Set(to.map((code) => code.endCode));
	const startCodesInFrom = new Set(from.map((code) => code.code));

	return [
		// Ignore all styles in `from` that are not overwritten or removed by `to`
		// Disable all styles in `from` that are removed in `to`
		...undoAnsiCodes(from.filter((code) => !endCodesInTo.has(code.endCode))),
		// Add all styles in `to` that don't exist in `from`
		...to.filter((code) => !startCodesInFrom.has(code.code)),
	];
}
