import React, { useCallback, useState, useEffect } 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 { MedicationRequest } from 'fhir/r4';
import { Check, FileText } from 'lucide-react';
import {
    useAuthServiceContext,
    useMedicationRequestServiceContext,
    usePatientServiceContext
} from '../../../../../services';
import { AppHeader, AppSpinner, ProfileLayoutContainer, ScrollableTab, HistoryNavigator, FhirMedicationRequest, FhirMedicationRequestDisplay } from '../../../../../components';
import { PrintableRegion, PrintRecord } from '../../../../../components/ui/print-record';
import { useFhirMedicationRequestTargetedBroadcast } from '../../../../../hooks';
import { useArchive } from '../../../../../hooks/useArchive';
import ArchiveConfirmModal from '../../../../../components/ArchiveConfirmModal/ArchiveConfirmModal';
import { describeWriteFailure } from '../../../../../utils/fetchFailureMessage';
import { mayEditRecord } from '../../../../../utils/recordEditability';
import { useSeatStanding } from '../../../../../utils/seatStanding';
import { patientCacheGuard } from '../../../../../utils/cacheOwner';

const EditMedicationRequestPage: React.FC = () => {
    const { medicationRequestId } = useParams<{ medicationRequestId: string }>();
    const navigate = useNavigate();
    const { currentUser, userRole, USER_ROLES, practitionerRoles } = useAuthServiceContext();
    const seatStanding = useSeatStanding();
    const { patientState, encounterState } = usePatientServiceContext();
    const {
        cachedForPatientId: medicationRequestsOwner,
        fetchMedicationRequest,
        transformToFhirMedicationRequest,
        transformFromFhirMedicationRequest,
        createMedicationRequest,
        updateMedicationRequest,
        archiveMedicationRequest,
        medicationRequestsList: rawMedicationRequestsList
    } = useMedicationRequestServiceContext();
    // The cache outlives a change of patient: read only the patient on screen.
    const medicationRequestsGuard = patientCacheGuard(medicationRequestsOwner, patientState?.id);
    const medicationRequestsList = medicationRequestsGuard.list(rawMedicationRequestsList);

    const [loading, setLoading] = useState(false);
    const [submitting, setSubmitting] = useState(false);
    const [success, setSuccess] = useState<string | undefined>();
    const [error, setError] = useState<string | undefined>();
    const [medicationRequest, setMedicationRequest] = useState<MedicationRequest | undefined>();

    const isPatient = [USER_ROLES.PATIENT, USER_ROLES.RELATED_PERSON].includes(userRole as string);

    /*
     * MAY THIS VIEWER EDIT THIS RECORD - the question the page below is drawn from.
     *
     * It used to ask `isPatient`, which is one case of it. Writing a MedicationRequest needs a paid clinician seat,
     * resolved per request by the server's `callerMayWrite`, and an unseated practitioner passed every
     * check here: the form opened populated, with Save and Archive, and the write came back refused. A
     * refusal that arrives after the typing has already spent the work.
     *
     * THE LIST IS NOT ENOUGH ON ITS OWN. A control removed only from the list is a client gate with a
     * door beside it - this page is reachable by URL - so the same question is asked again here.
     */
    const seat = mayEditRecord({ seatStanding,
        resourceType: 'MedicationRequest',
        viewerIsStaff: !isPatient,
        practitionerRoles,
    });

    const mayWrite = !isPatient && seat.mayEdit;
    const isNew = medicationRequestId === 'new';
    const spacerMargin = '24px';

    const methods = useForm({
        defaultValues: {
            status: '',
            intent: '',
            priority: '',
            doNotPerform: false,
            reported: false,
            medicationCodeableConcept: null,
            reasonCode: [],
            note: [],
            dosageInstruction: [],
            dispenseRequest: null,
            substitution: null,
            requester: [{}]
        }
    });

    const { handleSubmit, reset } = methods;

    const init = useCallback((medicationRequest: MedicationRequest) => {
        reset(transformFromFhirMedicationRequest(medicationRequest));
        setMedicationRequest(medicationRequest);
    }, [transformFromFhirMedicationRequest]);

    useFhirMedicationRequestTargetedBroadcast({
        medicationRequest,
        medicationRequestId,
        onUpdate: init,
        onDelete: () => navigate('..', { relative: 'path' })
    });

    const archive = useArchive((reason, note) => archiveMedicationRequest(medicationRequest!, reason, note));

    useEffect(() => {
        const loadMedicationRequest = async () => {
            if (isNew || medicationRequest) return;

            const foundMedicationRequest = medicationRequestsList?.find(mr => mr.id === medicationRequestId);

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

            setLoading(true);

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

        loadMedicationRequest();
    }, [medicationRequest, medicationRequestsList, medicationRequestId, fetchMedicationRequest, 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 createMedicationRequest(transformToFhirMedicationRequest(data, patientState, encounterState, currentUser?.fhir));

                navigate('..', { relative: 'path' });
            } else {
                await updateMedicationRequest({
                    id: medicationRequest?.id,
                    ...transformToFhirMedicationRequest(data)
                });
            }

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

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

    return (
        <HistoryNavigator<MedicationRequest> resourceType="MedicationRequest" resourceId={medicationRequestId || ''}>
            {(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>
                            )}

                            {/* SAID, NOT WITHHELD. A Save that simply disappears reads as a broken screen or as a
                                permission the reader has lost, and both send them to an administrator to check permissions
                                that are already correct. A seat is nameable, and a practice can enable one in a minute. */}
                            {!isPatient && !seat.mayEdit && (
                                <p className="text-sm text-secondary max-w-[22rem]">{seat.reason}</p>
                            )}

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

                            {!isNew && mayWrite && (
                                <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. */}
                            {!mayWrite && medicationRequest && <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. `FhirMedicationRequestDisplay`
                                    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. */}
                                {!mayWrite && medicationRequest ? (
                                    <PrintableRegion>
                                        <FhirMedicationRequestDisplay medicationRequest={medicationRequest}
                                                                   isOpen={true}
                                                                   onClose={() => undefined}/>
                                    </PrintableRegion>
                                ) : (
                                    <FhirMedicationRequest elevated={true}
                                                           disabled={submitting}/>
                                )}
                            </ProfileLayoutContainer>
                        </ScrollableTab>

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

export default EditMedicationRequestPage;