import { useEffect } from 'react';
import { Observation } from 'fhir/r4';
import { useObservationServiceContext, usePatientServiceContext, useWebSocketServiceContext } from '../services';
import { useNoticeFence } from './useNoticeFence';

interface UseObservationWebSocketOptions {
    observation?: Observation;
    observationId?: string;
    isOpen?: boolean;
    onUpdate: (observation: Observation) => void;
    onDelete: () => void;
}

export const useFhirObservationTargetedBroadcast = ({
                                                        observation,
                                                        observationId,
                                                        isOpen = true,
                                                        onUpdate,
                                                        onDelete
                                                    }: UseObservationWebSocketOptions) => {
    const { subscribe, unsubscribe } = useWebSocketServiceContext();
    const { patientState } = usePatientServiceContext();
    const { fetchObservation } = useObservationServiceContext();
    // Closing, opening another result or another patient ends this opening: a reread begun before answers nobody.
    const fence = useNoticeFence(`${patientState?.id}|${observationId || observation?.id}|${isOpen}`);

    useEffect(() => {
        if (!patientState || !observation || !isOpen) {
            return;
        }

        const handleObservationEvent = (cloudEvent: any) => {
            const observationPayload: Observation = cloudEvent.data;
            const eventType = cloudEvent.type;

            const targetId = observationId || observation.id;

            // A notice names the result and nothing of it: the gated GET says what it is now, or that it is not shown.
            const stands = observationPayload.id === targetId ? fence.claim(targetId as string) : () => false;
            if (observationPayload.id === targetId && cloudEvent.data?.invalidated === true) {
                if (eventType === 'com.akashichealthrecords.fhir.observation.deleted') {
                    onDelete();
                    return;
                }
                if (eventType === 'com.akashichealthrecords.fhir.observation.updated') {
                    fetchObservation(targetId as string, true)
                        .then((fresh) => { if (stands()) onUpdate(fresh); })
                        .catch(() => { if (stands()) onDelete(); });
                }
                return;
            }

            if (observationPayload.id === targetId) {
                switch (eventType) {
                    case 'com.akashichealthrecords.fhir.observation.updated':
                        onUpdate(observationPayload);
                        break;
                    case 'com.akashichealthrecords.fhir.observation.deleted':
                        onDelete();
                        break;
                }
            }
        };

        subscribe('com.akashichealthrecords.fhir.observation.updated', handleObservationEvent);
        subscribe('com.akashichealthrecords.fhir.observation.deleted', handleObservationEvent);

        return () => {
            unsubscribe('com.akashichealthrecords.fhir.observation.updated', handleObservationEvent);
            unsubscribe('com.akashichealthrecords.fhir.observation.deleted', handleObservationEvent);
        };
    }, [patientState, observation, observationId, isOpen, onUpdate, onDelete, subscribe, unsubscribe, fetchObservation, fence]);
};