import type { RewardItem, RewardCategory } from '../types/payment.types';

export const REWARD_PRIORITY: RewardCategory[] = ['special', 'general'];

export const parseRewardAmount = (amount: number | string): number => {
  const value = typeof amount === 'string' ? parseFloat(amount) : amount;
  return Number.isFinite(value) ? value : 0;
};

export const getCappedRewardAmounts = (
  selected: RewardItem[],
  payableAmount?: string | number | null
): Record<RewardCategory, number> => {
  const parsedPayable =
    payableAmount != null ? parseRewardAmount(payableAmount) : NaN;
  let remaining = Number.isFinite(parsedPayable) ? parsedPayable : Infinity;

  const result: Record<RewardCategory, number> = { special: 0, general: 0 };

  REWARD_PRIORITY.forEach((type) => {
    const picked = selected.find((item) => item.type === type);
    if (!picked) return;

    const value = parseRewardAmount(picked.amount);
    if (value <= 0) return;

    const used = Math.min(value, remaining);
    remaining = Math.max(remaining - used, 0);
    result[type] = used;
  });

  return result;
};

export const getCappedRewardTotal = (
  selected: RewardItem[],
  payableAmount?: string | number | null
): number => {
  const amounts = getCappedRewardAmounts(selected, payableAmount);
  return REWARD_PRIORITY.reduce((sum, type) => sum + amounts[type], 0);
};