import { useEffect } from 'react';
import { HealthcareService } from 'fhir/r4';
import {
    useHealthcareServiceServiceContext,
    useFhirServiceContext,
    useWebSocketServiceContext
} from '../services';
import { environment } from '../environments/environment.ts';
import { evidenceScope, observe, type ServiceObservation } from '../utils/booking/serviceCatalogueEvidence';

// A change seen as it happened is what the service is now, until a later whole search agrees; it never ends an attempt.
const recordEvidence = (service: HealthcareService, observation: ServiceObservation) => {
    const practice = service?.providedBy?.reference?.split('/')[1];
    if (!service?.id || !practice) return;
    try {
        observe(evidenceScope(practice, environment.fhirBaseApi), service.id, observation);
    } catch (error) {
        console.error('Service change could not be kept:', error);
    }
};

export const useFhirHealthcareServiceBroadcast = () => {
    const { subscribe, unsubscribe } = useWebSocketServiceContext();
    const { healthcareServicesList, setHealthcareServicesList } = useHealthcareServiceServiceContext();
    const { extractReferenceId } = useFhirServiceContext();

    useEffect(() => {
        const handleHealthcareServiceEvent = (cloudEvent: any) => {
            const healthcareService: HealthcareService = cloudEvent.data;
            const eventType = cloudEvent.type;
            if (eventType === 'com.akashichealthrecords.fhir.healthcareservice.deleted') recordEvidence(healthcareService, { kind: 'deleted' });
            else if (eventType === 'com.akashichealthrecords.fhir.healthcareservice.created' || eventType === 'com.akashichealthrecords.fhir.healthcareservice.updated') {
                recordEvidence(healthcareService, { kind: 'version', versionId: healthcareService?.meta?.versionId, active: healthcareService?.active !== false });
            }

            switch (eventType) {
                case 'com.akashichealthrecords.fhir.healthcareservice.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.
                    setHealthcareServicesList(prev =>
                        prev.some(p => p.id === healthcareService.id)
                            ? prev.map(p => p.id === healthcareService.id ? healthcareService : p)
                            : [...prev, healthcareService]
                    );
                    break;
                case 'com.akashichealthrecords.fhir.healthcareservice.updated':
                    setHealthcareServicesList(prev => prev.map(p => p.id === healthcareService.id ? healthcareService : p));
                    break;
                case 'com.akashichealthrecords.fhir.healthcareservice.deleted':
                    setHealthcareServicesList(prev => prev.filter(p => p.id !== healthcareService.id));
                    break;
            }
        };

        subscribe('com.akashichealthrecords.fhir.healthcareservice.created', handleHealthcareServiceEvent);
        subscribe('com.akashichealthrecords.fhir.healthcareservice.updated', handleHealthcareServiceEvent);
        subscribe('com.akashichealthrecords.fhir.healthcareservice.deleted', handleHealthcareServiceEvent);

        return () => {
            unsubscribe('com.akashichealthrecords.fhir.healthcareservice.created', handleHealthcareServiceEvent);
            unsubscribe('com.akashichealthrecords.fhir.healthcareservice.updated', handleHealthcareServiceEvent);
            unsubscribe('com.akashichealthrecords.fhir.healthcareservice.deleted', handleHealthcareServiceEvent);
        };
    }, [subscribe, unsubscribe, extractReferenceId, healthcareServicesList]);
};