import React, { useState, useEffect, useCallback } from 'react';
import { useNavigate, useParams } from 'react-router-dom';
import { DismissibleAlert } from '../../../../../components/ui/dismissible-alert';
import { Spacer } from '../../../../../components/ui/spacer';
import { useForm, FormProvider } from 'react-hook-form';
import { MedicationDispense } from 'fhir/r4';
import { Check, FileText } from 'lucide-react';
import {
    useAuthServiceContext,
    useMedicationDispenseServiceContext,
    usePatientServiceContext
} from '../../../../../services';
import { AppHeader, AppSpinner, ProfileLayoutContainer, ScrollableTab, HistoryNavigator, FhirMedicationDispense, FhirMedicationDispenseDisplay } from '../../../../../components';
import { PrintableRegion, PrintRecord } from '../../../../../components/ui/print-record';
import { useFhirMedicationDispenseTargetedBroadcast } from '../../../../../hooks';
import { useArchive } from '../../../../../hooks/useArchive';
import ArchiveConfirmModal from '../../../../../components/ArchiveConfirmModal/ArchiveConfirmModal';
import { describeWriteFailure } from '../../../../../utils/fetchFailureMessage';
import { patientCacheGuard } from '../../../../../utils/cacheOwner';

const EditMedicationDispensePage: React.FC = () => {
    const { medicationDispenseId } = useParams<{ medicationDispenseId: string }>();
    const navigate = useNavigate();
    const { userRole, USER_ROLES } = useAuthServiceContext();
    const { patientState, encounterState } = usePatientServiceContext();
    const {
        cachedForPatientId: medicationDispensesOwner,
        fetchMedicationDispense,
        transformToFhirMedicationDispense,
        transformFromFhirMedicationDispense,
        createMedicationDispense,
        updateMedicationDispense,
        archiveMedicationDispense,
        medicationDispensesList: rawMedicationDispensesList,
    } = useMedicationDispenseServiceContext();
    // The cache outlives a change of patient: read only the patient on screen.
    const medicationDispensesGuard = patientCacheGuard(medicationDispensesOwner, patientState?.id);
    const medicationDispensesList = medicationDispensesGuard.list(rawMedicationDispensesList);

    const [loading, setLoading] = useState(false);
    const [submitting, setSubmitting] = useState(false);
    const [success, setSuccess] = useState<string | undefined>();
    const [error, setError] = useState<string | undefined>();
    const [medicationDispense, setMedicationDispense] = useState<MedicationDispense | undefined>();

    const isPatient = [USER_ROLES.PATIENT, USER_ROLES.RELATED_PERSON].includes(userRole as string);
    const isNew = medicationDispenseId === 'new';
    const spacerMargin = '24px';

    const methods = useForm({
        defaultValues: {
            identifier: [],
            partOf: [],
            status: '',
            statusReasonCodeableConcept: null,
            category: null,
            medicationType: '',
            medicationCodeableConcept: null,
            medicationReference: null,
            subject: null,
            context: null,
            supportingInformation: [],
            performer: [],
            location: null,
            authorizingPrescription: [],
            type: null,
            quantity: null,
            daysSupply: null,
            whenPrepared: '',
            whenHandedOver: '',
            destination: null,
            receiver: [],
            note: [],
            dosageInstruction: [],
            substitution: null,
            detectedIssue: [],
            eventHistory: []
        }
    });

    const { handleSubmit, reset } = methods;

    const init = useCallback((medicationDispense: MedicationDispense) => {
        reset(transformFromFhirMedicationDispense(medicationDispense));
        setMedicationDispense(medicationDispense);
    }, [transformFromFhirMedicationDispense]);

    useFhirMedicationDispenseTargetedBroadcast({
        medicationDispense,
        medicationDispenseId,
        onUpdate: init,
        onDelete: () => navigate('..', { relative: 'path' })
    });

    const archive = useArchive((reason, note) => archiveMedicationDispense(medicationDispense!, reason, note));

    useEffect(() => {
        const loadMedicationDispense = async () => {
            if (isNew || medicationDispense) return;

            const foundMedicationDispense = medicationDispensesList?.find(md => md.id === medicationDispenseId);

            if (foundMedicationDispense) {
                init(foundMedicationDispense);
                return;
            }

            setLoading(true);

            try {
                const fetchedMedicationDispense = await fetchMedicationDispense(medicationDispenseId as string);
                init(fetchedMedicationDispense);
            } catch (err) {
                console.error('Error loading medication dispense:', err);
                setError('Could not load medication dispense. Try again.');
            } finally {
                setLoading(false);
            }
        };

        loadMedicationDispense();
    }, [medicationDispense, medicationDispensesList, medicationDispenseId, fetchMedicationDispense, init]);

    const onSubmit = async (data: any) => {
        if (isPatient) return;

        if (!patientState) {
            setError('Patient information is missing. Please try again.');
            return;
        }

        setSubmitting(true);
        setSuccess(undefined);
        setError(undefined);

        try {
            if (isNew) {
                await createMedicationDispense(transformToFhirMedicationDispense(data, patientState, encounterState));

                navigate('..', { relative: 'path' });
            } else {
                await updateMedicationDispense({
                    id: medicationDispense?.id,
                    ...transformToFhirMedicationDispense(data, patientState)
                });
            }

            setSuccess(`Medication dispense ${isNew ? 'created' : 'updated'} successfully.`);
            setTimeout(() => setSuccess(undefined), 3_000);
        } catch (err: any) {
            console.error(`Error ${isNew ? 'creating' : 'updating'} medication dispense:`, err);
            setError(describeWriteFailure(err, `Failed to ${isNew ? 'create' : 'update'} medication dispense`));
        } finally {
            setSubmitting(false);
        }
    };

    if (loading) {
        return (
            <AppSpinner/>
        );
    }

    return (
        <HistoryNavigator<MedicationDispense> resourceType="MedicationDispense" resourceId={medicationDispenseId || ''}>
            {(showHistory) => (
                <FormProvider {...methods}>

                    <form onSubmit={handleSubmit(onSubmit)}>
                        <AppHeader showBackButton={true}>

                            {!isNew && (
                                <button
                                    type="button"
                                    className="btn btn-blue"
                                    disabled={submitting}
                                    onClick={showHistory}
                                >
                                    <FileText />
                                    History
                                </button>
                            )}

                            {!isPatient && (
                                <button
                                    className={`btn btn-green${submitting ? ' btn-busy' : ''}`}
                                    disabled={submitting}
                                    type="submit"
                                >
                                    <Check />
                                    Save
                                </button>
                            )}

                            {!isNew && !isPatient && (
                                <button type="button" className="btn btn-green" onClick={archive.open}>
                                    Archive
                                </button>
                            )}

                            {/* The record has to be able to leave the screen. Without this a
                                patient sending it to somebody not on Akashic photographs a scrolling
                                page or prints the browser window, navigation and all. */}
                            {isPatient && medicationDispense && <PrintRecord/>}
                        </AppHeader>

                        {success && (
                            <>
                                <DismissibleAlert status="success" onDismiss={() => setSuccess(undefined)}>
                                    {success}
                                </DismissibleAlert>

                                <Spacer margin={spacerMargin}/>
                            </>
                        )}

                        {error && (
                            <>
                                <DismissibleAlert status="error" onDismiss={() => setError(undefined)}>
                                    <div className="whitespace-pre-line">{error}</div>
                                </DismissibleAlert>

                                <Spacer margin={spacerMargin}/>
                            </>
                        )}

                        <ScrollableTab>
                            <ProfileLayoutContainer>
                                {/* THE READER GETS THE RECORD, NOT THE FORM SWITCHED OFF. `FhirMedicationDispenseDisplay`
                                    already renders this resource for the history viewer, the reference
                                    preview and the patient snapshot, so a patient was the one audience shown
                                    the edit form instead of the view written for reading it. The old shape
                                    wrapped the form in `inert`, which is worse than it looks: the fields stay
                                    in the accessibility tree, so a screen reader still reads them as inputs,
                                    and a text range over the subtree returns an EMPTY STRING - a patient
                                    could not select or copy their own record. */}
                                {isPatient && medicationDispense ? (
                                    <PrintableRegion>
                                        <FhirMedicationDispenseDisplay medicationDispense={medicationDispense}
                                                                    isOpen={true}
                                                                    onClose={() => undefined}/>
                                    </PrintableRegion>
                                ) : (
                                    <FhirMedicationDispense elevated={true}
                                                            disabled={submitting}/>
                                )}
                            </ProfileLayoutContainer>
                        </ScrollableTab>

                        <ArchiveConfirmModal
                            open={archive.isOpen}
                            onOpenChange={(o) => { if (!o) archive.close(); }}
                            resourceLabel="Medication Dispense"
                            submitting={archive.submitting}
                            error={archive.error}
                            onConfirm={async (reason, note) => {
                                if (await archive.submit(reason, note)) {
                                    navigate('..', { relative: 'path' });
                                }
                            }}
                        />
                    </form>
                </FormProvider>
            )}
        </HistoryNavigator>
    );
};

export default EditMedicationDispensePage;