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 { EpisodeOfCare, Organization } from 'fhir/r4';
import { Check, FileText } from 'lucide-react';
import {
    useAuthServiceContext,
    useEpisodeOfCareServiceContext,
    usePatientServiceContext
} from '../../../../../services';
import { AppHeader, AppSpinner, HistoryNavigator, ProfileLayoutContainer, ScrollableTab, FhirEpisodeOfCare, FhirEpisodeOfCareDisplay } from '../../../../../components';
import { PrintableRegion, PrintRecord } from '../../../../../components/ui/print-record';
import { useFhirEpisodeOfCareTargetedBroadcast } from '../../../../../hooks';
import { useArchive } from '../../../../../hooks/useArchive';
import ArchiveConfirmModal from '../../../../../components/ArchiveConfirmModal/ArchiveConfirmModal';
import { describeWriteFailure } from '../../../../../utils/fetchFailureMessage';
import { patientCacheGuard } from '../../../../../utils/cacheOwner';

const EditEpisodeOfCarePage: React.FC = () => {
    const { episodeOfCareId } = useParams<{ episodeOfCareId: string }>();
    const navigate = useNavigate();
    const { userRole, USER_ROLES, wpOrganization } = useAuthServiceContext();
    const { patientState } = usePatientServiceContext();
    const {
        cachedForPatientId: episodesOfCareOwner,
        fetchEpisodeOfCare,
        transformToFhirEpisodeOfCare,
        transformFromFhirEpisodeOfCare,
        createEpisodeOfCare,
        updateEpisodeOfCare,
        archiveEpisodeOfCare,
        episodesOfCareList: rawEpisodesOfCareList
    } = useEpisodeOfCareServiceContext();
    // The cache outlives a change of patient: read only the patient on screen.
    const episodesOfCareGuard = patientCacheGuard(episodesOfCareOwner, patientState?.id);
    const episodesOfCareList = episodesOfCareGuard.list(rawEpisodesOfCareList);

    const [loading, setLoading] = useState(false);
    const [submitting, setSubmitting] = useState(false);
    const [success, setSuccess] = useState<string | undefined>();
    const [error, setError] = useState<string | undefined>();
    const [episodeOfCare, setEpisodeOfCare] = useState<EpisodeOfCare | undefined>();

    const archive = useArchive((reason, note) => archiveEpisodeOfCare(episodeOfCare!, reason, note));

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

    const methods = useForm({
        defaultValues: {
            identifier: [],
            status: '',
            statusHistory: [],
            type: [],
            diagnosis: [],
            managingOrganization: null,
            referralRequest: [],
            careManager: null,
            team: [],
            account: []
        }
    });

    const { handleSubmit, reset } = methods;

    const init = useCallback((episodeOfCare: EpisodeOfCare) => {
        reset(transformFromFhirEpisodeOfCare(episodeOfCare));
        setEpisodeOfCare(episodeOfCare);
    }, [transformFromFhirEpisodeOfCare]);

    useFhirEpisodeOfCareTargetedBroadcast({
        episodeOfCare,
        episodeOfCareId,
        onUpdate: init,
        onDelete: () => navigate('..', { relative: 'path' })
    });

    useEffect(() => {
        const loadEpisodeOfCare = async () => {
            if (isNew || episodeOfCare) return;

            const foundEpisodeOfCare = episodesOfCareList?.find(eoc => eoc.id === episodeOfCareId);

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

            setLoading(true);

            try {
                const fetchedEpisodeOfCare = await fetchEpisodeOfCare(episodeOfCareId as string);
                init(fetchedEpisodeOfCare);
            } catch (err) {
                console.error('Error loading episode of care:', err);
                setError('Could not load episode of care. Try again.');
            } finally {
                setLoading(false);
            }
        };

        loadEpisodeOfCare();
    }, [episodeOfCare, episodesOfCareList, episodeOfCareId, fetchEpisodeOfCare, 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 createEpisodeOfCare(transformToFhirEpisodeOfCare(data, patientState, wpOrganization.current as Organization));

                navigate('..', { relative: 'path' });
            } else {
                await updateEpisodeOfCare({
                    id: episodeOfCare?.id,
                    ...transformToFhirEpisodeOfCare(data)
                });
            }

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

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

    return (
        <HistoryNavigator<EpisodeOfCare> resourceType="EpisodeOfCare" resourceId={episodeOfCareId || ''}>
            {(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 && episodeOfCare && <PrintRecord/>}
                        </AppHeader>

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

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

                        {error && (
                            <>
                                <DismissibleAlert status="error" onDismiss={() => setError(undefined)}>
                                    <div style={{ whiteSpace: 'pre-line' }}>{error}</div>
                                </DismissibleAlert>

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

                        <ScrollableTab>
                            <ProfileLayoutContainer>
                                {/* THE READER GETS THE RECORD, NOT THE FORM SWITCHED OFF. `FhirEpisodeOfCareDisplay`
                                    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 && episodeOfCare ? (
                                    <PrintableRegion>
                                        <FhirEpisodeOfCareDisplay episodeOfCare={episodeOfCare}
                                                               isOpen={true}
                                                               onClose={() => undefined}/>
                                    </PrintableRegion>
                                ) : (
                                    <FhirEpisodeOfCare elevated={true}
                                                       disabled={submitting}/>
                                )}
                            </ProfileLayoutContainer>
                        </ScrollableTab>

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

export default EditEpisodeOfCarePage;