// src/pages/DashboardPage/BillingPage/unbilledAppointments.ts
// Task 4 (invoicing epic, Phase B): "Option C" un-invoiced-appointment detection. There is no
// ChargeItem resource tying an Appointment to an Invoice - instead a 'timed' invoice line (Task 3)
// carries the appointmentId it was booked off of. An appointment is "billed" when some non-voided
// invoice has a line pointing at it; voiding an invoice (cancelled / entered-in-error) frees its
// appointments to be billed again, since the charge never actually stuck.
//
// PURE module - no React, no services, no I/O. Task 5's editor is responsible for fetching the
// invoices/appointments and calling these two functions.
import type { Appointment, Invoice } from 'fhir/r4';
import { readInvoiceLines } from '../../../utils/invoiceTransform';

// A voided invoice's charges never stuck - its appointments should be billable again.
const VOID_INVOICE_STATUSES: ReadonlyArray<Invoice['status']> = ['cancelled', 'entered-in-error'];

// Nothing to bill for an appointment that never happened / was struck from the record.
const UNBILLABLE_APPOINTMENT_STATUSES: ReadonlyArray<Appointment['status']> = [
    'cancelled', 'entered-in-error', 'noshow',
];

// Collect every appointmentId referenced by a line on any non-voided invoice.
export const billedAppointmentIds = (invoices: Invoice[]): Set<string> => {
    const ids = new Set<string>();
    invoices
        .filter((invoice) => !VOID_INVOICE_STATUSES.includes(invoice.status))
        .forEach((invoice) => {
            readInvoiceLines(invoice).forEach((line) => {
                if (line.appointmentId) ids.add(line.appointmentId);
            });
        });
    return ids;
};

// Appointments still available to bill: not already covered by a live invoice line, not missing an
// id (can't be tracked), and not in a status where there's nothing to charge for.
export const unbilledAppointments = (appointments: Appointment[], billedIds: Set<string>): Appointment[] =>
    appointments.filter((appointment) =>
        !!appointment.id
        && !billedIds.has(appointment.id)
        && !UNBILLABLE_APPOINTMENT_STATUSES.includes(appointment.status));