import { validateAmount } from "@/lib/validation";

interface QueryParamReader {
  get(name: string): string | null;
}

interface ConversionShareParams {
  amount?: string;
  fromCode?: string;
  toCode?: string;
}

const CODE_PATTERN = /^[A-Z0-9]{2,12}$/;

function normalizeCurrencyCode(value: string | null): string | undefined {
  if (!value) {
    return undefined;
  }

  const normalized = value.trim().toUpperCase();

  if (!CODE_PATTERN.test(normalized)) {
    return undefined;
  }

  return normalized;
}

function normalizeAmount(value: string | null): string | undefined {
  if (!value) {
    return undefined;
  }

  const trimmed = value.trim().replace(/\s+/g, "");

  if (!trimmed || trimmed.length > 64) {
    return undefined;
  }

  return validateAmount(trimmed).ok ? trimmed : undefined;
}

export function parseConversionShareParams(
  searchParams: QueryParamReader,
): ConversionShareParams {
  const amount = normalizeAmount(searchParams.get("amount"));
  const fromCode = normalizeCurrencyCode(searchParams.get("from"));
  let toCode = normalizeCurrencyCode(searchParams.get("to"));

  if (fromCode && toCode && fromCode === toCode) {
    toCode = undefined;
  }

  return {
    amount,
    fromCode,
    toCode,
  };
}

export function buildConversionShareUrl(input: {
  origin: string;
  pathname: string;
  amount: string;
  fromCode: string;
  toCode: string;
}): string {
  const url = new URL(input.pathname, input.origin);
  const amount = normalizeAmount(input.amount) ?? "1";
  const fromCode = normalizeCurrencyCode(input.fromCode);
  const toCode = normalizeCurrencyCode(input.toCode);

  url.searchParams.set("amount", amount);

  if (fromCode) {
    url.searchParams.set("from", fromCode);
  }

  if (toCode && toCode !== fromCode) {
    url.searchParams.set("to", toCode);
  }

  return url.toString();
}