import { createTheme } from '@vanilla-extract/css';
import type { Contract, MapLeafNodes } from '@vanilla-extract/private';
import { DeepPartial } from 'utility-types';

function getVarsIntersection<
  A extends Record<string, any>,
  B extends Record<string, any>,
  X extends Extract<keyof A, keyof B> = Extract<keyof A, keyof B>,
>(a: A, b: B): Record<X, A[X]> {
  const result: Record<string, any> = {};

  for (const [key, bValue] of Object.entries(b)) {
    const aValue = a[key];

    if (!aValue || !bValue) {
      continue;
    }

    if (typeof bValue === 'string' && typeof aValue === 'string') {
      result[key] = aValue;
      continue;
    }

    result[key] = getVarsIntersection(aValue, bValue);
  }

  return result as Record<X, A[X]>;
}

export function extendTheme<ThemeContract extends Contract>(
  vars: ThemeContract,
  extendedVars: NonNullable<DeepPartial<MapLeafNodes<ThemeContract, string>>>,
) {
  const requiredVars = getVarsIntersection(vars, extendedVars);

  return createTheme(
    requiredVars as ThemeContract,
    extendedVars as MapLeafNodes<ThemeContract, string>,
  );
}