import { CSSResultGroup, CSSResult } from "lit";

export type ModalStyleSheetInput =
  | CSSResultGroup
  | CSSStyleSheet
  | Array<CSSResultGroup | CSSStyleSheet>;

const styleSheetCache = new WeakMap<CSSResult, CSSStyleSheet>();

function cssResultToStyleSheet(styleResult: CSSResult): CSSStyleSheet {
  const cachedStyleSheet = styleSheetCache.get(styleResult);
  if (cachedStyleSheet) return cachedStyleSheet;

  const styleSheet = new CSSStyleSheet();
  styleSheet.replaceSync(styleResult.cssText);
  styleSheetCache.set(styleResult, styleSheet);
  return styleSheet;
}

function isCSSResult(value: unknown): value is CSSResult {
  return value instanceof CSSResult;
}

export function normalizeStyleSheets(
  styleSheet?: ModalStyleSheetInput
): Array<CSSStyleSheet> {
  if (!styleSheet) return [];

  const styleSheets = Array.isArray(styleSheet) ? styleSheet : [styleSheet];

  return styleSheets.flatMap((sheet) => {
    if (Array.isArray(sheet)) {
      return normalizeStyleSheets(sheet);
    }

    if (sheet instanceof CSSStyleSheet) {
      return [sheet];
    }

    if (isCSSResult(sheet)) {
      return [cssResultToStyleSheet(sheet)];
    }

    return [];
  });
}