import type { ReadOptions } from '../hooks/anchorView/readOptions';
import { isHeld, overlayHeldBundle, refersToPatient, writtenSince } from '../utils/writeThroughHold';
import { useState, useCallback, createContext, useContext, ReactNode, useEffect, useRef } from 'react';
import {
    Bundle,
    DeviceUseStatement,
    Patient,
    CodeableConcept,
    Practitioner,
    PractitionerRole,
    RelatedPerson
} from 'fhir/r4';
import { environment } from '../environments/environment.ts';
import { useFhirServiceContext } from './FhirService.tsx';
import { useHttpService } from './HttpService.tsx';
import { formatFhirHumanName } from '../utils/fhirHumanName.tsx';
import { usePatientServiceContext } from './PatientService.tsx';
import { formatFhirPeriod } from '../utils/fhirPeriod.tsx';
import { applyArchive, isArchived, type ArchiveReason } from '../utils/archivedResource';
import { statusLabel } from '../utils/fhirStatusVocabulary';
import { fetchAllPagesAsBundle } from '../utils/fetchAllPagesAsBundle';
import { searchPageSize } from '../utils/pageSizeOverride';
import { useCacheOwner } from '../utils/cacheOwner';

const API_URL = environment.fhirClinicalApi;

export const useDeviceUseStatementService = () => {
    const { get, post, put, delete: del } = useHttpService();
    const { patientState } = usePatientServiceContext();
    const {
        transformToCodeableConcept,
        transformFromCodeableConcept,
        createReferenceObject,
        formatDateTime,
        formatDateTimeForInput,
        formatDateTimeForDisplay,
        addFhirPeriodIfApplicable,
        unpackBundle,
        transformToFhirTiming,
        transformFromFhirTiming,
        transformToReferenceCollection,
        transformFromReferenceCollection,
        extractReferenceId
    } = useFhirServiceContext();

    const [deviceUseStatementsList, setDeviceUseStatementsList] = useState<DeviceUseStatement[]>([]);
    const [shouldReload, setShouldReload] = useState<boolean>(false);
    const [lastUpserted, setLastUpserted] = useState<string | null | undefined>(null);
    const [unsaved, setUnsaved] = useState<boolean>(false);

    const [deviceUseStatementsBundle, setDeviceUseStatementsBundle] = useState<Bundle<DeviceUseStatement> | null>(null);
    const deviceUseStatementsBundleRef = useRef<Bundle<DeviceUseStatement> | null>(null);
    const lastFetchTimeRef = useRef<number>(0);

    useEffect(() => {
        deviceUseStatementsBundleRef.current = deviceUseStatementsBundle;
    }, [deviceUseStatementsBundle]);

    // WHOSE RECORDS ARE THESE? The reset below fires only when there is NO patient, which moving
    // between two charts never is - so the previous patient's bundle survived the switch and was
    // served as a cache hit, with no request and nothing on screen to say the list was not theirs.
    const cacheOwner = useCacheOwner('DeviceUseStatement', () => {
        setLastUpserted(null);
        setDeviceUseStatementsBundle(null);
        setDeviceUseStatementsList([]);
        lastFetchTimeRef.current = 0;
    });

    useEffect(() => {
        if (!patientState) {
            setDeviceUseStatementsBundle(null);
            setDeviceUseStatementsList([]);
            lastFetchTimeRef.current = 0;
            cacheOwner.release();
        }
    }, [patientState, cacheOwner.release]);

    const fetchDeviceUseStatements = useCallback(async (patient: Patient, options?: ReadOptions): Promise<Bundle<DeviceUseStatement>> => {
        return overlayHeldBundle('DeviceUseStatement', await fetchAllPagesAsBundle<DeviceUseStatement>((pageParam) => {
            let params = new URLSearchParams();

            params.append('_count', searchPageSize('100'));
            params.append('subject', patient.id as string);
            if (pageParam) params.set('page', pageParam);

            return get<Bundle<DeviceUseStatement>>(`${API_URL}/DeviceUseStatement?${params.toString()}`, options);
        }), (resource) => refersToPatient(resource, patient.id)) as Bundle<DeviceUseStatement>;
    }, [get]);

    const fetchDeviceUseStatementsWithPolling = useCallback(async (patient: Patient, forceReload = false): Promise<Bundle<DeviceUseStatement>> => {
        const now = Date.now();
        const cacheAge = now - lastFetchTimeRef.current;
        const cacheFresh = cacheAge < 5 * 60 * 1000;

        // cacheOwner.isFor is the load-bearing clause: a fresh bundle belonging to the PREVIOUS
        // patient satisfies every other condition here and would be returned as a hit.
        if (!forceReload && !shouldReload && !writtenSince('DeviceUseStatement', lastFetchTimeRef.current) && deviceUseStatementsBundleRef.current && cacheFresh && cacheOwner.isCurrentFor(patient.id)) {
            return deviceUseStatementsBundleRef.current;
        }

        const operation = cacheOwner.begin();

        let retries = 10;
        const delay = 3000;
        let found = false;
        let bundle: Bundle<DeviceUseStatement> | null = null;
        let entries: DeviceUseStatement[];

        do {
            bundle = await fetchDeviceUseStatements(patient);
            entries = unpackBundle(bundle);
            found = lastUpserted ? entries.some(e => e.id === lastUpserted) || isHeld('DeviceUseStatement', lastUpserted) : true;

            if (!found) {
                await new Promise(resolve => setTimeout(resolve, delay));
            }
            retries--;
        } while (!found && retries > 0 && cacheOwner.publishes(operation));


        if (!cacheOwner.publishes(operation)) return cacheOwner.answerFor(operation, bundle);
        setDeviceUseStatementsBundle(bundle);
        setDeviceUseStatementsList(entries.filter((r) => !isArchived(r)));
        setLastUpserted(null);
        setShouldReload(false);
        lastFetchTimeRef.current = now;
        // Stamped WITH the data, never before it - on a throw the owner must still name the list
        // that is actually in state.
        cacheOwner.claim(patient.id, operation);

        return bundle;
    }, [fetchDeviceUseStatements, unpackBundle, lastUpserted, shouldReload]);

    const fetchDeviceUseStatement = useCallback(async (id: string): Promise<DeviceUseStatement> => {
        const cachedDeviceUseStatement = cacheOwner.isCurrent(cacheOwner.claimed) ? deviceUseStatementsList.find(deviceUseStatement => deviceUseStatement.id === id) : undefined;
        if (cachedDeviceUseStatement) {
            return cachedDeviceUseStatement;
        }

        return get<DeviceUseStatement>(`${API_URL}/DeviceUseStatement/${id}`);
    }, [get, deviceUseStatementsList]);

    const fetchDeviceUseStatementHistory = useCallback(async (id: string, options?: ReadOptions): Promise<Bundle<DeviceUseStatement>> => {
        return get<Bundle<DeviceUseStatement>>(`${API_URL}/DeviceUseStatement/${id}/_history`, options);
    }, [get]);

    const createDeviceUseStatement = useCallback(async (deviceUseStatement: DeviceUseStatement): Promise<DeviceUseStatement> => {
        let params = new URLSearchParams();

        params.append('subject', extractReferenceId(deviceUseStatement.subject) as string);

        return post<DeviceUseStatement>(`${API_URL}/DeviceUseStatement?${params.toString()}`, deviceUseStatement);
    }, [post, extractReferenceId]);

    const updateDeviceUseStatement = useCallback(async (deviceUseStatement: DeviceUseStatement): Promise<DeviceUseStatement> => {
        return put<DeviceUseStatement>(`${API_URL}/DeviceUseStatement/${deviceUseStatement.id}`, deviceUseStatement);
    }, [put]);

    const deleteDeviceUseStatement = useCallback(async (deviceUseStatement: DeviceUseStatement): Promise<DeviceUseStatement> => {
        return del<DeviceUseStatement>(`${API_URL}/DeviceUseStatement/${deviceUseStatement.id}`);
    }, [del]);

    const archiveDeviceUseStatement = useCallback(async (deviceUseStatement: DeviceUseStatement, reason: ArchiveReason, note?: string): Promise<DeviceUseStatement> => {
        return put<DeviceUseStatement>(`${API_URL}/DeviceUseStatement/${deviceUseStatement.id}`, applyArchive(deviceUseStatement, reason, note));
    }, [put]);

    const transformToFhirDeviceUseStatement = useCallback((item: any, patient?: Patient, source?: Patient | Practitioner | PractitionerRole | RelatedPerson): DeviceUseStatement => {
        const {
            status,
            device,
            bodySite,
            timingType,
            timingDateTime,
            recordedOn,
            reasonCode,
            reasonReference,
            derivedFrom,
            note
        } = item;

        const transformedReasonReference = transformToReferenceCollection(reasonReference);
        const transformedDerivedFrom = transformToReferenceCollection(derivedFrom);

        let deviceUseStatement: DeviceUseStatement = {
            resourceType: 'DeviceUseStatement',
            status: status,
            device: device,
            ...(patient && { subject: createReferenceObject('Patient', patient.id as string, formatFhirHumanName(patient.name)) }),
            ...(source && { source: createReferenceObject(source.resourceType, source.id as string, formatFhirHumanName(source.name)) }),
            ...(bodySite && { bodySite: transformToCodeableConcept(bodySite) }),
            ...(recordedOn && { recordedOn: formatDateTime(recordedOn) }),
            ...(timingType === 'dateTime' && timingDateTime && { timingDateTime: formatDateTime(timingDateTime) }),
            ...(reasonCode && reasonCode.length !== 0 && { reasonCode: transformToCodeableConcept(reasonCode) as CodeableConcept[] }),
            ...(transformedReasonReference && transformedReasonReference.length !== 0 && { reasonReference: transformedReasonReference }),
            ...(transformedDerivedFrom && transformedDerivedFrom.length !== 0 && { derivedFrom: transformedDerivedFrom }),
            ...(note && note.length !== 0 && { note: note })
        };

        if (timingType === 'period') {
            deviceUseStatement = addFhirPeriodIfApplicable(deviceUseStatement, item, 'timingPeriod');
        } else if (timingType === 'timing') {
            deviceUseStatement = {
                ...deviceUseStatement,
                timingTiming: transformToFhirTiming(item.timingTiming)
            };
        }

        return deviceUseStatement;
    }, [
        createReferenceObject,
        transformToCodeableConcept,
        addFhirPeriodIfApplicable,
        formatDateTime,
        transformToFhirTiming,
        transformToReferenceCollection
    ]);

    const transformFromFhirDeviceUseStatement = useCallback((deviceUseStatement: DeviceUseStatement): any => {
        const {
            status,
            device,
            bodySite,
            recordedOn,
            timingDateTime,
            timingPeriod,
            timingTiming,
            reasonCode,
            reasonReference,
            derivedFrom,
            note
        } = deviceUseStatement;

        let timingType = '';
        if (timingDateTime) timingType = 'dateTime';
        else if (timingPeriod) timingType = 'period';
        else if (timingTiming) timingType = 'timing';

        const formData = {
            status: status,
            device: device,
            bodySite: transformFromCodeableConcept(bodySite),
            timingType: timingType,
            timingDateTime: formatDateTimeForInput(timingDateTime),
            timingTiming: transformFromFhirTiming(timingTiming),
            recordedOn: formatDateTimeForInput(recordedOn),
            reasonCode: transformFromCodeableConcept(reasonCode ?? []),
            reasonReference: transformFromReferenceCollection(reasonReference ?? []),
            derivedFrom: transformFromReferenceCollection(derivedFrom ?? []),
            note: note ?? []
        };

        let result = formData;

        if (timingPeriod) {
            result = addFhirPeriodIfApplicable(result, deviceUseStatement, 'timingPeriod');
        }

        return result;
    }, [
        transformFromCodeableConcept,
        addFhirPeriodIfApplicable,
        transformFromFhirTiming,
        transformFromReferenceCollection,
        formatDateTimeForInput
    ]);

    const getDeviceUseStatementDisplay = (deviceUseStatement: DeviceUseStatement): string => {
        if (!deviceUseStatement) {
            return 'Unknown Device Use Statement';
        }

        let deviceName = 'Unknown Device';
        if (deviceUseStatement.device) {
            deviceName = deviceUseStatement.device.display ||
                deviceUseStatement.device.reference?.split('/').pop() ||
                'Device Reference';
        }

        // - the human label, never the code. `statusLabel` returns `undefined` for a code we
        // have no words for, and this omits the status entirely in that case rather than falling back to
        // the raw value - the fallback IS the defect. `utils/fhirStatusVocabulary.ts`
        const statusText = statusLabel(deviceUseStatement.status);
        const status = statusText ? ` · ${statusText}` : '';

        let dateSuffix = '';
        if (deviceUseStatement.timingDateTime) {
            dateSuffix = ` (${formatDateTimeForDisplay(deviceUseStatement.timingDateTime)})`;
        } else if (deviceUseStatement.timingPeriod) {
            dateSuffix = ` (${formatFhirPeriod(deviceUseStatement.timingPeriod)})`;
        }

        return `${deviceName}${status}${dateSuffix}`;
    };

    return {
        deviceUseStatementsBundle,
        // WHO THE CACHED LIST IS FOR, so a consumer can ask whether it belongs to the patient on
        // screen rather than trusting an app-wide context with no patient in its name.
        cachedForPatientId: cacheOwner.ownerId,
        deviceUseStatementsList,
        setDeviceUseStatementsList,
        shouldReload,
        setShouldReload,
        lastUpserted,
        setLastUpserted,
        unsaved,
        setUnsaved,

        fetchDeviceUseStatements,
        fetchDeviceUseStatementsWithPolling,
        fetchDeviceUseStatement,
        fetchDeviceUseStatementHistory,
        createDeviceUseStatement,
        updateDeviceUseStatement,
        deleteDeviceUseStatement,
        archiveDeviceUseStatement,

        transformToFhirDeviceUseStatement,
        transformFromFhirDeviceUseStatement,
        getDeviceUseStatementDisplay
    };
};

const DeviceUseStatementServiceContext = createContext<ReturnType<typeof useDeviceUseStatementService> | undefined>(undefined);

export const DeviceUseStatementServiceProvider: React.FC<{ children: ReactNode }> = ({ children }) => {
    const deviceUseStatementService = useDeviceUseStatementService();

    return (
        <DeviceUseStatementServiceContext.Provider value={deviceUseStatementService}>
            {children}
        </DeviceUseStatementServiceContext.Provider>
    );
};

export const useDeviceUseStatementServiceContext = () => {
    const context = useContext(DeviceUseStatementServiceContext);

    if (context === undefined) {
        throw new Error('useDeviceUseStatementServiceContext must be used within a DeviceUseStatementServiceProvider');
    }

    return context;
};