import { useEffect } from 'react';
import { Invoice } from 'fhir/r4';
import {
    useInvoiceServiceContext,
    useFhirServiceContext,
    useWebSocketServiceContext
} from '../services';

// Optional patientId: when provided (a patient-scoped invoice list), only react to that patient's
// invoices. When omitted (the org-wide list), react to all - the list is already org-scoped server-side.
export const useFhirInvoiceBroadcast = (patientId?: string) => {
    const { subscribe, unsubscribe } = useWebSocketServiceContext();
    const { invoiceList, setInvoiceList } = useInvoiceServiceContext();
    const { extractReferenceId } = useFhirServiceContext();

    useEffect(() => {
        const handleInvoiceEvent = (cloudEvent: any) => {
            const invoice: Invoice = cloudEvent.data;
            const eventType = cloudEvent.type;
            const invoicePatientId = extractReferenceId(invoice.subject);

            if (patientId && patientId !== invoicePatientId) {
                return;
            }

            switch (eventType) {
                case 'com.akashichealthrecords.fhir.invoice.created':
                    // The list has two writers: this broadcast, and the service's own refetch after a write
                    // (several of which POLL until the new id appears). Refetch first and the list already holds
                    // the record, so an unconditional append put a SECOND copy of it on screen - observed on a
                    // patient's questionnaire answers, where one submission rendered as two completed forms.
                    // Keeping the broadcast's copy rather than skipping: its body is at least as fresh.
                    setInvoiceList(prev =>
                        prev.some(p => p.id === invoice.id)
                            ? prev.map(p => p.id === invoice.id ? invoice : p)
                            : [...prev, invoice]
                    );
                    break;
                case 'com.akashichealthrecords.fhir.invoice.updated':
                    // Invoices aren't archived - a voided/cancelled invoice stays visible with its new
                    // status (e.g. a "paid"/"void" badge flip), so this always replaces, never removes.
                    setInvoiceList(prev => prev.map(i => i.id === invoice.id ? invoice : i));
                    break;
                case 'com.akashichealthrecords.fhir.invoice.deleted':
                    setInvoiceList(prev => prev.filter(i => i.id !== invoice.id));
                    break;
            }
        };

        subscribe('com.akashichealthrecords.fhir.invoice.created', handleInvoiceEvent);
        subscribe('com.akashichealthrecords.fhir.invoice.updated', handleInvoiceEvent);
        subscribe('com.akashichealthrecords.fhir.invoice.deleted', handleInvoiceEvent);

        return () => {
            unsubscribe('com.akashichealthrecords.fhir.invoice.created', handleInvoiceEvent);
            unsubscribe('com.akashichealthrecords.fhir.invoice.updated', handleInvoiceEvent);
            unsubscribe('com.akashichealthrecords.fhir.invoice.deleted', handleInvoiceEvent);
        };
    }, [patientId, subscribe, unsubscribe, extractReferenceId, invoiceList, setInvoiceList]);
};