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,
    MedicationAdministration,
    Patient,
    Encounter,
    Reference,
    MedicationAdministrationDosage,
    ProcedurePerformer
} 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 { useEncounterServiceContext } from './EncounterService.tsx';
import { usePatientServiceContext } from './PatientService.tsx';
import { formatFhirCodeableConcept } from '../utils/fhirCodeableConcept.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 useMedicationAdministrationService = () => {
    const { get, post, put, delete: del } = useHttpService();
    const { patientState } = usePatientServiceContext();
    const {
        transformToCodeableConcept,
        transformFromCodeableConcept,
        createReferenceObject,
        formatDateTime,
        formatDateTimeForInput,
        formatDateTimeForDisplay,
        addFhirPeriodIfApplicable,
        addPeriodControlsIfApplicable,
        unpackBundle,
        transformToFhirQuantity,
        transformFromFhirQuantity,
        transformToReferenceCollection,
        transformFromReferenceCollection,
        extractReferenceId
    } = useFhirServiceContext();
    const { getEncounterDisplay } = useEncounterServiceContext();

    const [medicationAdministrationsList, setMedicationAdministrationsList] = useState<MedicationAdministration[]>([]);
    const [shouldReload, setShouldReload] = useState<boolean>(false);
    const [lastUpserted, setLastUpserted] = useState<string | null | undefined>(null);
    const [unsaved, setUnsaved] = useState<boolean>(false);


    const [medicationAdministrationsBundle, setMedicationAdministrationsBundle] = useState<Bundle<MedicationAdministration> | null>(null);
    const medicationAdministrationsBundleRef = useRef<Bundle<MedicationAdministration> | null>(null);
    const lastFetchTimeRef = useRef<number>(0);

    useEffect(() => {
        medicationAdministrationsBundleRef.current = medicationAdministrationsBundle;
    }, [medicationAdministrationsBundle]);

    // 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('MedicationAdministration', () => {
        setLastUpserted(null);
        setMedicationAdministrationsBundle(null);
        setMedicationAdministrationsList([]);
        lastFetchTimeRef.current = 0;
    });

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

    const fetchMedicationAdministrations = useCallback(async (patient: Patient, options?: ReadOptions): Promise<Bundle<MedicationAdministration>> => {
        return overlayHeldBundle('MedicationAdministration', await fetchAllPagesAsBundle<MedicationAdministration>((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<MedicationAdministration>>(`${API_URL}/MedicationAdministration?${params.toString()}`, options);
        }), (resource) => refersToPatient(resource, patient.id)) as Bundle<MedicationAdministration>;
    }, [get]);

    const fetchMedicationAdministrationsWithPolling = useCallback(async (patient: Patient, forceReload = false): Promise<Bundle<MedicationAdministration>> => {
        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('MedicationAdministration', lastFetchTimeRef.current) && medicationAdministrationsBundleRef.current && cacheFresh && cacheOwner.isCurrentFor(patient.id)) {
            return medicationAdministrationsBundleRef.current;
        }

        const operation = cacheOwner.begin();

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

        do {
            bundle = await fetchMedicationAdministrations(patient);
            entries = unpackBundle(bundle);
            found = lastUpserted ? entries.some(e => e.id === lastUpserted) || isHeld('MedicationAdministration', 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);
        setMedicationAdministrationsBundle(bundle);
        setMedicationAdministrationsList(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;
    }, [fetchMedicationAdministrations, unpackBundle, lastUpserted, shouldReload]);

    const fetchMedicationAdministration = useCallback(async (id: string): Promise<MedicationAdministration> => {
        const cachedAdministration = cacheOwner.isCurrent(cacheOwner.claimed) ? medicationAdministrationsList.find(administration => administration.id === id) : undefined;
        if (cachedAdministration) {
            return cachedAdministration;
        }

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

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

    const createMedicationAdministration = useCallback(async (medicationAdministration: MedicationAdministration): Promise<MedicationAdministration> => {
        let params = new URLSearchParams();

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

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

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

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

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

    const transformToFhirMedicationAdministration = useCallback((item: any, patient: Patient, encounterState?: Encounter): MedicationAdministration => {
        const {
            partOf,
            status,
            statusReason,
            category,
            medicationType,
            medicationCodeableConcept,
            medicationReference,
            subject,
            context,
            effectiveType,
            effectiveDateTime,
            effectivePeriod,
            performer,
            reasonCode,
            reasonReference,
            request,
            device,
            note,
            dosage
        } = item;

        const patientReference: Reference = createReferenceObject('Patient', patient.id as string, formatFhirHumanName(patient.name));
        const transformedContext = transformToReferenceCollection(context);
        const transformedReasonReference = transformToReferenceCollection(reasonReference);
        const transformedPartOf = transformToReferenceCollection(partOf);

        const transformedPerformer: ProcedurePerformer[] = performer.map((p: any) => {
            const transformedPerformerActor: Reference[] = transformToReferenceCollection(p.actor);

            if (transformedPerformerActor.length === 0) {
                return null;
            }

            const performerItem: ProcedurePerformer = {
                actor: transformedPerformerActor[0],
                ...(p.function && { function: transformToCodeableConcept(p.function) })
            };

            if (Object.keys(performerItem).length !== 0) {
                return performerItem;
            }

            return null;
        }).filter(Boolean);

        let transformedDosage: MedicationAdministrationDosage | undefined = undefined;

        if (dosage) {
            const transformedDose = transformToFhirQuantity(dosage.dose);
            transformedDosage = {
                ...(dosage.text && { text: dosage.text }),
                ...(dosage.site && { site: transformToCodeableConcept(dosage.site) }),
                ...(dosage.route && { route: transformToCodeableConcept(dosage.route) }),
                ...(dosage.method && { method: transformToCodeableConcept(dosage.method) }),
                ...(transformedDose && { dose: transformedDose }),
                ...(dosage.rateType === 'ratio' && dosage.rateRatio && { rateRatio: dosage.rateRatio }),
                ...(dosage.rateType === 'quantity' && dosage.rateQuantity && { rateQuantity: transformToFhirQuantity(dosage.rateQuantity) })
            };
        }

        let medicationAdministration: MedicationAdministration = {
            resourceType: 'MedicationAdministration',
            status: status,
            subject: subject || patientReference,
            ...(encounterState && { context: createReferenceObject('Encounter', encounterState?.id as string, getEncounterDisplay(encounterState)) }),
            ...(transformedContext && transformedContext.length !== 0 && { context: transformedContext[0] }),
            ...(statusReason && statusReason.length > 0 && { statusReason: transformToCodeableConcept(statusReason) }),
            ...(category && { category: transformToCodeableConcept(category) }),
            ...(medicationCodeableConcept && { medicationCodeableConcept: transformToCodeableConcept(medicationCodeableConcept) }),
            ...(medicationType === 'reference' && medicationReference && { medicationReference }),
            ...(effectiveType === 'dateTime' && effectiveDateTime && { effectiveDateTime: formatDateTime(effectiveDateTime) }),
            ...(transformedPerformer && transformedPerformer.length !== 0 && { performer: transformedPerformer }),
            ...(reasonCode && reasonCode.length !== 0 && { reasonCode: transformToCodeableConcept(reasonCode) }),
            ...(transformedReasonReference && transformedReasonReference.length !== 0 && { reasonReference: transformedReasonReference }),
            ...(transformedPartOf && transformedPartOf.length !== 0 && { partOf: transformedPartOf }),
            ...(request && { request: request }),
            ...(device && device.length !== 0 && { device: device }),
            ...(note && note.length !== 0 && { note: note }),
            ...(transformedDosage && Object.keys(transformedDosage).length !== 0 && { dosage: transformedDosage })
        };

        if (effectivePeriod) {
            delete medicationAdministration.effectiveDateTime;
            return addFhirPeriodIfApplicable(medicationAdministration, item, 'effectivePeriod');
        }

        return medicationAdministration;
    }, [
        createReferenceObject,
        transformToCodeableConcept,
        formatDateTime,
        addFhirPeriodIfApplicable,
        transformToFhirQuantity,
        transformToReferenceCollection,
        getEncounterDisplay
    ]);

    const transformFromFhirMedicationAdministration = useCallback((medicationAdministration: MedicationAdministration): any => {
        const {
            partOf,
            status,
            statusReason,
            category,
            medicationCodeableConcept,
            medicationReference,
            subject,
            context,
            effectiveDateTime,
            effectivePeriod,
            performer,
            reasonCode,
            reasonReference,
            request,
            device,
            note,
            dosage
        } = medicationAdministration;

        const formData = {
            status: status,
            statusReason: statusReason ? statusReason.map(reason => transformFromCodeableConcept(reason)) : [],
            category: transformFromCodeableConcept(category) || null,
            medicationType: medicationCodeableConcept ? 'codeableConcept' : medicationReference ? 'reference' : 'codeableConcept',
            medicationCodeableConcept: transformFromCodeableConcept(medicationCodeableConcept) || null,
            medicationReference: medicationReference || null,
            subject: subject,
            context: transformFromReferenceCollection(context ? [context] : []),
            effectiveType: effectiveDateTime ? 'dateTime' : effectivePeriod ? 'period' : '',
            effectiveDateTime: formatDateTimeForInput(effectiveDateTime),
            performer: (performer ?? []).map((p: ProcedurePerformer) => ({
                actor: transformFromReferenceCollection(p.actor ? [p.actor] : []),
                function: transformFromCodeableConcept(p.function)
            })),
            reasonCode: transformFromCodeableConcept(reasonCode ?? []),
            reasonReference: transformFromReferenceCollection(reasonReference ?? []),
            request: request,
            device: device ?? [],
            note: note ?? [],
            partOf: transformFromReferenceCollection(partOf ?? []),
            dosage: {
                text: dosage?.text ?? '',
                site: transformFromCodeableConcept(dosage?.site),
                route: transformFromCodeableConcept(dosage?.route),
                method: transformFromCodeableConcept(dosage?.method),
                dose: transformFromFhirQuantity(dosage?.dose),
                rateType: dosage?.rateRatio ? 'ratio' : dosage?.rateQuantity ? 'quantity' : '',
                rateRatio: dosage?.rateRatio,
                rateQuantity: transformFromFhirQuantity(dosage?.rateQuantity)
            }
        };

        return addPeriodControlsIfApplicable(formData, medicationAdministration, 'effectivePeriod');
    }, [
        transformFromCodeableConcept,
        addFhirPeriodIfApplicable,
        transformFromReferenceCollection,
        transformFromFhirQuantity,
        formatDateTimeForInput
    ]);

    const getMedicationAdministrationDisplay = (medicationAdministration: MedicationAdministration): string => {
        if (!medicationAdministration) {
            return 'Unknown Medication Administration';
        }

        let medicationName = 'Unknown Medication';
        if (medicationAdministration.medicationCodeableConcept) {
            medicationName = formatFhirCodeableConcept(medicationAdministration.medicationCodeableConcept);
        } else if (medicationAdministration.medicationReference) {
            medicationName = medicationAdministration.medicationReference.display || 'Medication 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(medicationAdministration.status);
        const status = statusText ? ` · ${statusText}` : '';

        let dateSuffix = '';
        if (medicationAdministration.effectiveDateTime) {
            dateSuffix = ` (${formatDateTimeForDisplay(medicationAdministration.effectiveDateTime)})`;
        } else if (medicationAdministration.effectivePeriod) {
            dateSuffix = ` (${formatFhirPeriod(medicationAdministration.effectivePeriod)})`;
        }

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

    return {
        medicationAdministrationsBundle,
        // 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,
        medicationAdministrationsList,
        setMedicationAdministrationsList,
        shouldReload,
        setShouldReload,
        lastUpserted,
        setLastUpserted,
        unsaved,
        setUnsaved,

        fetchMedicationAdministrations,
        fetchMedicationAdministrationsWithPolling,
        fetchMedicationAdministration,
        fetchMedicationAdministrationHistory,
        createMedicationAdministration,
        updateMedicationAdministration,
        deleteMedicationAdministration,
        archiveMedicationAdministration,

        transformToFhirMedicationAdministration,
        transformFromFhirMedicationAdministration,
        getMedicationAdministrationDisplay
    };
};

const MedicationAdministrationServiceContext = createContext<ReturnType<typeof useMedicationAdministrationService> | undefined>(undefined);

export const MedicationAdministrationServiceProvider: React.FC<{ children: ReactNode }> = ({ children }) => {
    const medicationAdministrationService = useMedicationAdministrationService();

    return (
        <MedicationAdministrationServiceContext.Provider value={medicationAdministrationService}>
            {children}
        </MedicationAdministrationServiceContext.Provider>
    );
};

export const useMedicationAdministrationServiceContext = () => {
    const context = useContext(MedicationAdministrationServiceContext);

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

    return context;
};