// Pure, React-free helpers for the patient-portal payment redirect flow (Invoicing Phase 3, Slice B -
// direct patient payments, BYO processor). Kept dependency-free so it unit-tests without dragging the
// services barrel, and so the checkout/return logic is verifiable in isolation.
import { formatMoney, parseDollarsToCents } from './money';

// Checkout result classification and the request-body shape now live in invoiceCheckoutAttempt.ts,
// which also owns the durable pending-operation store; this file keeps only the React-free helpers
// that do not depend on the typed endpoint result (URL building, session-id parsing, partial-amount UX).

// Build the same-origin portal URLs handed to the checkout endpoint as successUrl/cancelUrl.
//
// We KEEP the current route (window.location.hash) because the app is a HashRouter SPA: dropping the
// hash would return the patient to the default route instead of the invoices page where the return poll
// is mounted. We DROP any existing query string (callers pass window.location.{origin,pathname,hash}) so
// a stale session_id is never re-sent. The server appends `session_id={CHECKOUT_SESSION_ID}` itself and
// validates only the HOST against the org's configured portal host, so path + fragment are free to vary.
export const buildCheckoutUrls = (
    origin: string,
    pathname: string,
    hash: string,
): { successUrl: string; cancelUrl: string } => {
    const base = `${origin}${pathname}${hash}`;
    return { successUrl: base, cancelUrl: base };
};

// Extract Stripe's checkout session id from the returned URL. Because the app is a HashRouter SPA, the
// server-appended `session_id=` may land on the REAL query string (`?session_id=`) OR inside the fragment
// (`#/invoices?session_id=`) depending on whether the successUrl carried a hash - so we scan the whole
// href for a `session_id` query param rather than reading window.location.search alone.
export const parseReturnSessionId = (href: string): string | null => {
    const match = /[?&]session_id=([^&#]+)/.exec(href ?? '');
    return match ? decodeURIComponent(match[1]) : null;
};

// Remove the session_id (and our optional pay=cancelled marker) from a URL so a manual refresh doesn't
// re-trigger the poll, tidying any dangling separators left behind. Operates on the string form so it
// works identically whether the params sit on the query string or inside a HashRouter fragment.
export const stripPaymentReturnParams = (href: string): string => {
    let out = href ?? '';
    out = out.replace(/([?&])session_id=[^&#]*/g, '$1');
    out = out.replace(/([?&])pay=[^&#]*/g, '$1');
    out = out.replace(/([?&])&+/g, '$1'); // collapse "?&""?" and "&&""&"
    out = out.replace(/[?&]$/g, ''); // drop a now-empty trailing "?" or "&"
    return out;
};

// Client-side validation for the patient portal's "Pay a different amount" input (Task 9). This is UX
// only - a disabled button / inline hint before submit - never the real boundary; the server re-validates
// amountCents against the remaining balance and the invoice's allowPartialPay independently. Parses the
// same way the invoice line editor does (parseDollarsToCents: dollars text -> integer cents), then
// range-checks against the remaining balance (also integer cents).
export type PartialPayValidation = { ok: true; cents: number } | { ok: false; error: string };

export const parsePartialPayAmount = (input: string, remainingCents: number): PartialPayValidation => {
    const cents = parseDollarsToCents(input);
    if (cents === undefined) {
        return { ok: false, error: 'Enter an amount.' };
    }
    if (cents <= 0) {
        return { ok: false, error: 'Enter an amount greater than $0.' };
    }
    if (cents > remainingCents) {
        return { ok: false, error: `Cannot exceed ${formatMoney(remainingCents)} remaining.` };
    }
    return { ok: true, cents };
};