import { isVisible } from "./detect";
import { extractDomain } from "../shared/domain";

function getRegistrableDomain(hostname: string): string {
  return extractDomain(hostname) ?? hostname;
}

function checkFormAction(form: HTMLFormElement | null, expectedDomain: string): boolean {
  if (!form?.action) return true;
  try {
    const actionUrl = new URL(form.action);
    const actionDomain = getRegistrableDomain(actionUrl.hostname);
    if (actionDomain !== expectedDomain) {
      return false;
    }
  } catch {}
  return true;
}

export function fillFields(
  usernameEl: HTMLInputElement | null,
  passwordEl: HTMLInputElement | null,
  username: string,
  password: string,
  form?: HTMLFormElement | null,
  expectedDomain?: string
): void {
  if (expectedDomain && form && !checkFormAction(form, expectedDomain)) {
    return;
  }
  // Fill username regardless of visibility — on SPA step-by-step login flows
  // the username input may be visually hidden but still tracked by the form.
  if (usernameEl && username) {
    setNativeValue(usernameEl, username);
  }
  if (passwordEl && isVisible(passwordEl)) {
    setNativeValue(passwordEl, password);
  }
}

// React tracks input values via a synthetic event system that does not see
// direct `.value =` assignment. We must call the native HTMLInputElement
// value setter (pulled off the prototype) and then dispatch the real input
// and change events so React re-reads the new value. Without this, the
// field reads as empty to the form's controlled-input state.
function setNativeValue(el: HTMLInputElement, value: string): void {
  const nativeInputValueSetter = Object.getOwnPropertyDescriptor(
    window.HTMLInputElement.prototype,
    "value"
  )?.set;
  nativeInputValueSetter?.call(el, value);
  el.dispatchEvent(new Event("input", { bubbles: true }));
  el.dispatchEvent(new Event("change", { bubbles: true }));
}

export interface CardFillFields {
  number: HTMLInputElement | null;
  expMonth: HTMLInputElement | null;
  expYear: HTMLInputElement | null;
  expiryCombo: HTMLInputElement | null;
  cvc: HTMLInputElement | null;
  name: HTMLInputElement | null;
}

export function fillCardForm(fields: CardFillFields, card: { cardNumber: string; expMonth: string; expYear: string; cvc: string; cardholderName: string }): void {
  const raw = card.cardNumber.replace(/\s/g, '');
  if (fields.number) setNativeValue(fields.number, formatCardNumber(raw));
  if (fields.expiryCombo) {
    setNativeValue(fields.expiryCombo, `${card.expMonth}/${card.expYear.slice(-2)}`);
  } else {
    if (fields.expMonth) setNativeValue(fields.expMonth, card.expMonth);
    if (fields.expYear) setNativeValue(fields.expYear, card.expYear);
  }
  if (fields.cvc) setNativeValue(fields.cvc, card.cvc);
  if (fields.name) setNativeValue(fields.name, card.cardholderName);
}

export function formatCardNumber(raw: string): string {
  if (/^3[47]/.test(raw)) return raw.replace(/(\d{4})(\d{6})(\d{5})/, '$1 $2 $3');
  return raw.replace(/(\d{4})(?=\d)/g, '$1 ').trim();
}

export function detectCardNetwork(number: string): import('../shared/types').CardNetwork {
  const n = number.replace(/\s/g, '');
  if (/^4/.test(n)) return 'visa';
  if (/^5[1-5]|^2[2-7]/.test(n)) return 'mastercard';
  if (/^3[47]/.test(n)) return 'amex';
  if (/^6(?:011|5)/.test(n)) return 'discover';
  return 'unknown';
}

export function passesLuhn(number: string): boolean {
  const digits = number.replace(/\s/g, '').split('').map(Number);
  let sum = 0, isEven = false;
  for (let i = digits.length - 1; i >= 0; i--) {
    let d = digits[i]!;
    if (isEven) { d *= 2; if (d > 9) d -= 9; }
    sum += d;
    isEven = !isEven;
  }
  return sum % 10 === 0;
}

export function extractLast4(number: string): string {
  return number.replace(/\s/g, '').slice(-4);
}