import type { HttpContext } from '@adonisjs/core/http';
// import { RequestContract } from '@ioc:Adonis/Core/Request';
import { Request } from '@adonisjs/core/http';
import { XMLBuilder } from 'xmlbuilder2/lib/interfaces.js';
import { create } from 'xmlbuilder2';
import dayjs, { Dayjs } from 'dayjs';
import utc from 'dayjs/plugin/utc.js';
import timezone from 'dayjs/plugin/timezone.js';
import { readFileSync } from 'fs';
import { StatusCodes } from 'http-status-codes';
import SaxonJS from 'saxon-js';
// import { Xslt, xmlParse } from 'xslt-processor'
import { OaiErrorCodes, OaiModelError } from '#app/exceptions/OaiErrorCodes';
import { OaiModelException, BadOaiModelException } from '#app/exceptions/OaiModelException';
import Dataset from '#models/dataset';
import Collection from '#models/collection';
import { getDomain, preg_match } from '#app/utils/utility-functions';
import XmlModel from '#app/Library/XmlModel';
import logger from '@adonisjs/core/services/logger';
import ResumptionToken from '#app/Library/Oai/ResumptionToken';
// import Config from '@ioc:Adonis/Core/Config';
import config from '@adonisjs/core/services/config';
// import { inject } from '@adonisjs/fold';
import { inject } from '@adonisjs/core';
// import { TokenWorkerContract } from "MyApp/Models/TokenWorker";
import TokenWorkerContract from '#library/Oai/TokenWorkerContract';
import { ModelQueryBuilderContract } from '@adonisjs/lucid/types/model';

interface XslTParameter {
    [key: string]: any;
}

interface Dictionary {
    [index: string]: string;
}

interface PagingParameter {
    cursor: number;
    totalLength: number;
    start: number;
    nextDocIds: number[];
    activeWorkIds: number[];
    metadataPrefix: string;
    queryParams: Object;
}

@inject()
export default class OaiController {
    private deliveringDocumentStates = ['published', 'deleted'];
    private sampleRegEx = /^[A-Za-zäüÄÜß0-9\-_.!~]+$/;
    private xsltParameter: XslTParameter;

    private firstPublishedDataset: Dataset | null;
    /**
     * Holds xml representation of document information to be processed.
     *
     * @var xmlbuilder.XMLDocument | null  Defaults to null.
     */
    private xml: XMLBuilder;
    private proc;

    constructor(public tokenWorker: TokenWorkerContract) {
        // Load the XSLT file
        this.proc = readFileSync('public/assets2/datasetxml2oai.sef.json');
        dayjs.extend(utc);
        dayjs.extend(timezone);
    }

    public async index({ response, request }: HttpContext): Promise<void> {
        this.xml = create({ version: '1.0', encoding: 'UTF-8', standalone: true }, '<root></root>');

        // this.proc = new XSLTProcessor();
        // const stylesheet = readFileSync(__dirname + "/datasetxml2oai.sef.json");
        const xsltParameter: XslTParameter = (this.xsltParameter = {});

        let oaiRequest: Dictionary = {};
        if (request.method() === 'POST') {
            oaiRequest = request.body();
        } else if (request.method() === 'GET') {
            oaiRequest = request.qs();
        } else {
            xsltParameter['oai_error_code'] = 'unknown';
            xsltParameter['oai_error_message'] = 'Only POST and GET methods are allowed for OAI-PMH.';
        }

        let earliestDateFromDb;
        // const oaiRequest: OaiParameter = request.body;
        try {
            this.firstPublishedDataset = await Dataset.earliestPublicationDate();
            this.firstPublishedDataset != null &&
                (earliestDateFromDb = this.firstPublishedDataset.server_date_published.toFormat("yyyy-MM-dd'T'HH:mm:ss'Z'"));
            this.xsltParameter['earliestDatestamp'] = earliestDateFromDb;
            // start the request
            await this.handleRequest(oaiRequest, request);
        } catch (error) {
            if (error instanceof OaiModelException) {
                const code = error.oaiCode;
                let oaiErrorCode: string | undefined = 'Unknown oai error code ' + code;
                if (OaiModelError.has(error.oaiCode) && OaiModelError.get(code) !== undefined) {
                    oaiErrorCode = OaiModelError.get(error.oaiCode);
                }
                this.xsltParameter['oai_error_code'] = oaiErrorCode;
                this.xsltParameter['oai_error_message'] = error.message;
            } else {
                //     // return next(error); // passing to default express middleware error handler
                this.xsltParameter['oai_error_code'] = 'unknown';
                this.xsltParameter['oai_error_message'] = 'An internal error occured.';
            }
        }

        const xmlString = this.xml.end({ prettyPrint: true });

        let xmlOutput; // = xmlString;
        try {
            const result = await SaxonJS.transform({
                // stylesheetFileName: `${config.TMP_BASE_DIR}/data-quality/rules/iati.sef.json`,
                stylesheetText: this.proc,
                destination: 'serialized',
                // sourceFileName: sourceFile,
                sourceText: xmlString,
                stylesheetParams: xsltParameter,
                // logLevel: 10,
            });
            xmlOutput = result.principalResult;
        } catch (error) {
            return response.status(500).json({
                message: 'An error occurred while creating the user',
                error: error.message,
            });
        }

        response
            .header('Content-Type', 'application/xml; charset=utf-8')
            .header('Access-Control-Allow-Origin', '*')
            .header('Access-Control-Allow-Methods', 'GET,POST');
        response.status(StatusCodes.OK).send(xmlOutput);
    }

    protected async handleRequest(oaiRequest: Dictionary, request: Request) {
        // Setup stylesheet
        // $this->loadStyleSheet('datasetxml2oai-pmh.xslt');

        // Set response time
        const now: Dayjs = dayjs();
        this.xsltParameter['responseDate'] = now.format('YYYY-MM-DDTHH:mm:ss[Z]');
        this.xsltParameter['unixTimestamp'] = now.unix();

        // set OAI base url
        const baseDomain = process.env.OAI_BASE_DOMAIN || 'localhost';
        this.xsltParameter['baseURL'] = baseDomain + '/oai';
        this.xsltParameter['repURL'] = request.protocol() + '://' + request.hostname();
        this.xsltParameter['downloadLink'] = request.protocol() + '://' + request.hostname() + '/file/download/';
        this.xsltParameter['doiLink'] = 'https://doi.org/';
        this.xsltParameter['doiPrefix'] = 'info:eu-repo/semantics/altIdentifier/doi/';

        if (oaiRequest['verb']) {
            const verb = oaiRequest['verb'];
            this.xsltParameter['oai_verb'] = verb;
            if (verb === 'Identify') {
                this.handleIdentify();
            } else if (verb === 'ListMetadataFormats') {
                this.handleListMetadataFormats();
            } else if (verb == 'GetRecord') {
                await this.handleGetRecord(oaiRequest);
            } else if (verb == 'ListRecords') {
                // Get browser fingerprint from the request:
                const browserFingerprint = this.getBrowserFingerprint(request);
                await this.handleListRecords(oaiRequest, browserFingerprint);
            } else if (verb == 'ListIdentifiers') {
                // Get browser fingerprint from the request:
                const browserFingerprint = this.getBrowserFingerprint(request);
                await this.handleListIdentifiers(oaiRequest, browserFingerprint);
            } else if (verb == 'ListSets') {
                await this.handleListSets();
            } else {
                this.handleIllegalVerb();
            }
        } else {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'The verb provided in the request is illegal.',
                OaiErrorCodes.BADVERB,
            );
        }
    }

    protected handleIdentify() {
        // Get configuration values from environment or a dedicated configuration service
        const email = process.env.OAI_EMAIL ?? 'repository@geosphere.at';
        const repositoryName = process.env.OAI_REPOSITORY_NAME ?? 'Tethys RDR';
        const repIdentifier = process.env.OAI_REP_IDENTIFIER ?? 'tethys.at';
        const sampleIdentifier = `oai:${repIdentifier}:1`;
        // Dataset::earliestPublicationDate()->server_date_published->format('Y-m-d\TH:i:s\Z') : null;
        // earliestDateFromDb!= null && (this.xsltParameter['earliestDatestamp'] = earliestDateFromDb?.server_date_published);

        // set parameters for oai-pmh.xslt
        this.xsltParameter['email'] = email;
        this.xsltParameter['repositoryName'] = repositoryName;
        this.xsltParameter['repIdentifier'] = repIdentifier;
        this.xsltParameter['sampleIdentifier'] = sampleIdentifier;
        // $this->proc->setParameter('', 'earliestDatestamp', $earliestDateFromDb);

        this.xml.root().ele('Datasets');
    }

    protected handleListMetadataFormats() {
        this.xml.root().ele('Datasets');
    }

    protected async handleListSets() {
        const repIdentifier = 'tethys.at';
        this.xsltParameter['repIdentifier'] = repIdentifier;
        const datasetElement = this.xml.root().ele('Datasets');

        const sets: { [key: string]: string } = {
            'open_access': 'Set for open access licenses',
            'openaire_data': 'OpenAIRE',
            'doc-type:ResearchData': 'Set for document type ResearchData',
            ...(await this.getSetsForDatasetTypes()),
            ...(await this.getSetsForCollections()),
            // ... await this.getSetsForProjects(),
        } as Dictionary;

        for (const [key, value] of Object.entries(sets)) {
            const setElement = datasetElement.ele('Rdr_Sets');
            setElement.att('Type', key);
            setElement.att('TypeName', value);
        }
    }

    protected async handleGetRecord(oaiRequest: Dictionary) {
        const repIdentifier = 'tethys.at';
        this.xsltParameter['repIdentifier'] = repIdentifier;

        // Validate that required parameter exists early
        if (!('identifier' in oaiRequest)) {
            throw new BadOaiModelException('The prefix of the identifier argument is unknown.');
        }

        // Validate and extract the dataset identifier from the request
        const dataId = this.validateAndGetIdentifier(oaiRequest);

        // Retrieve dataset with associated XML cache and collection roles
        const dataset = await Dataset.query()
            .where('publish_id', dataId)
            .preload('xmlCache')
            .preload('collections', (builder) => {
                builder.preload('collectionRole');
            })
            .first();

        if (!dataset || !dataset.publish_id) {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'The value of the identifier argument is unknown or illegal in this repository.',
                OaiErrorCodes.IDDOESNOTEXIST,
            );
        }

        // Validate and set the metadata prefix parameter
        const metadataPrefix = this.validateAndGetMetadataPrefix(oaiRequest);
        this.xsltParameter['oai_metadataPrefix'] = metadataPrefix;

        // Ensure that the dataset is in an exportable state
        this.validateDatasetState(dataset);

        // Build the XML for the dataset record and add it to the root node
        const datasetNode = this.xml.root().ele('Datasets');
        await this.createXmlRecord(dataset, datasetNode);
    }

    protected async handleListIdentifiers(oaiRequest: Dictionary, browserFingerprint: string) {
        if (!this.tokenWorker.isConnected) {
            await this.tokenWorker.connect();
        }

        const maxIdentifier: number = config.get('oai.max.listidentifiers', 100);
        await this.handleLists(oaiRequest, maxIdentifier, browserFingerprint);
    }

    protected async handleListRecords(oaiRequest: Dictionary, browserFingerprint: string) {
        if (!this.tokenWorker.isConnected) {
            await this.tokenWorker.connect();
        }

        const maxRecords: number = config.get('oai.max.listrecords', 100);
        await this.handleLists(oaiRequest, maxRecords, browserFingerprint);
    }

    private async handleLists(oaiRequest: Dictionary, maxRecords: number, browserFingerprint: string) {
        const repIdentifier = 'tethys.at';
        this.xsltParameter['repIdentifier'] = repIdentifier;
        const datasetNode = this.xml.root().ele('Datasets');

        const paginationParams: PagingParameter ={
            cursor: 0,
            totalLength: 0,
            start: maxRecords + 1,
            nextDocIds: [],
            activeWorkIds: [],
            metadataPrefix: '',
            queryParams: {},
        };

        if ('resumptionToken' in oaiRequest) {
            await this.handleResumptionToken(oaiRequest, maxRecords, paginationParams);
        } else {
            await this.handleNoResumptionToken(oaiRequest, paginationParams, maxRecords);
        }

        const nextIds: number[] = paginationParams.nextDocIds;
        const workIds: number[] = paginationParams.activeWorkIds;

        if (workIds.length === 0) {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'The combination of the given values results in an empty list.',
                OaiErrorCodes.NORECORDSMATCH,
            );
        }

        const datasets = await Dataset.query()
            .whereIn('publish_id', workIds)
            .preload('xmlCache')
            .preload('collections', (builder) => {
                builder.preload('collectionRole');
            })
            .orderBy('publish_id');
        for (const dataset of datasets) {
            await this.createXmlRecord(dataset, datasetNode);
        }
        await this.setResumptionToken(nextIds, paginationParams, browserFingerprint);
    }

    private async handleNoResumptionToken(oaiRequest: Dictionary, paginationParams: PagingParameter, maxRecords: number) {
        this.validateMetadataPrefix(oaiRequest, paginationParams);       
        const finder: ModelQueryBuilderContract<typeof Dataset, Dataset> = Dataset.query().whereIn(
            'server_state',
            this.deliveringDocumentStates,
        );
        this.applySetFilter(finder, oaiRequest);
        this.applyDateFilters(finder, oaiRequest);
        await this.fetchAndSetResults(finder, paginationParams, oaiRequest, maxRecords);
    }

    private async fetchAndSetResults(
        finder: ModelQueryBuilderContract<typeof Dataset, Dataset>,
        paginationParams: PagingParameter,
        oaiRequest: Dictionary,
        maxRecords: number
    ) {
        const totalResult = await finder
            .clone()
            .count('* as total')
            .first()
            .then((res) => res?.$extras.total);
            paginationParams.totalLength = Number(totalResult);

        const combinedRecords: Dataset[] = await finder.select('publish_id').orderBy('publish_id').offset(0).limit(maxRecords*2);

        paginationParams.activeWorkIds = combinedRecords.slice(0, 100).map((dat) => Number(dat.publish_id));
        paginationParams.nextDocIds = combinedRecords.slice(100).map((dat) => Number(dat.publish_id));

        // No resumption token was used – set queryParams from the current oaiRequest
        paginationParams.queryParams = {
            ...oaiRequest,
            deliveringStates: this.deliveringDocumentStates,
        };

        // paginationParams.totalLength = 230;
    }

    private async handleResumptionToken(oaiRequest: Dictionary, maxRecords: number, paginationParams: PagingParameter) {
        const resParam = oaiRequest['resumptionToken'];
        const token = await this.tokenWorker.get(resParam);

        if (!token) {
            throw new OaiModelException(StatusCodes.INTERNAL_SERVER_ERROR, 'cache is outdated.', OaiErrorCodes.BADRESUMPTIONTOKEN);
        }

        // this.setResumptionParameters(token, maxRecords, paginationParams);
        paginationParams.cursor = token.startPosition - 1;
        paginationParams.start = token.startPosition + maxRecords;
        paginationParams.totalLength = token.totalIds;
        paginationParams.activeWorkIds = token.documentIds;
        paginationParams.metadataPrefix = token.metadataPrefix;
        paginationParams.queryParams = token.queryParams;
        this.xsltParameter['oai_metadataPrefix'] = token.metadataPrefix;

        const finder = this.buildDatasetQueryViaToken(token);
        const nextRecords: Dataset[] = await this.fetchNextRecords(finder, token, maxRecords);
        paginationParams.nextDocIds = nextRecords.map((dat) => Number(dat.publish_id));
    }

    private async setResumptionToken(nextIds: number[], paginationParams: PagingParameter, browserFingerprint: string) {
        const countRestIds = nextIds.length;
        if (countRestIds > 0) {
            // const token = this.createResumptionToken(paginationParams, nextIds);
            const token = new ResumptionToken();
            token.startPosition = paginationParams.start;
            token.totalIds = paginationParams.totalLength;
            token.documentIds = nextIds;
            token.metadataPrefix = paginationParams.metadataPrefix;
            token.queryParams = paginationParams.queryParams;
            const res: string = await this.tokenWorker.set(token, browserFingerprint);
            this.setParamResumption(res, paginationParams.cursor, paginationParams.totalLength);
        }
    }

    private buildDatasetQueryViaToken(token: ResumptionToken) {
        const finder = Dataset.query();
        const originalQuery = token.queryParams || {};
        const deliveringStates = originalQuery.deliveringStates || this.deliveringDocumentStates;

        finder.whereIn('server_state', deliveringStates);
        this.applySetFilter(finder, originalQuery);
        this.applyDateFilters(finder, originalQuery);

        return finder;
    }

    private async fetchNextRecords(finder: ModelQueryBuilderContract<typeof Dataset, Dataset>, token: ResumptionToken, maxRecords: number) {
        return finder
            .select('publish_id')
            .orderBy('publish_id')
            .offset(token.startPosition - 1 + maxRecords)
            .limit(100);
    }

    private validateMetadataPrefix(oaiRequest: Dictionary, paginationParams: PagingParameter) {
        if (!('metadataPrefix' in oaiRequest)) {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'The prefix of the metadata argument is unknown.',
                OaiErrorCodes.BADARGUMENT,
            );
        }
        paginationParams.metadataPrefix = oaiRequest['metadataPrefix'];
        this.xsltParameter['oai_metadataPrefix'] = paginationParams.metadataPrefix;
    }

    private applySetFilter(finder: ModelQueryBuilderContract<typeof Dataset, Dataset>, queryParams: any) {
        if ('set' in queryParams) {
            const [setType, setValue] = queryParams['set'].split(':');

            switch (setType) {
                case 'data-type':
                    setValue && finder.where('type', setValue);
                    break;
                case 'open_access':
                    finder.andWhereHas('licenses', (query) => {
                        query.whereIn('name', ['CC-BY-4.0', 'CC-BY-SA-4.0']);
                    });
                    break;
                case 'ddc':
                    setValue &&
                        finder.andWhereHas('collections', (query) => {
                            query.where('number', setValue);
                        });
                    break;
            }
        }
    }

    private applyDateFilters(finder: ModelQueryBuilderContract<typeof Dataset, Dataset>, queryParams: any) {
        const { from, until } = queryParams;

        if (from && until) {
            this.handleFromUntilFilter(finder, from, until);
        } else if (from) {
            this.handleFromFilter(finder, from);
        } else if (until) {
            this.handleUntilFilter(finder, until);
        }
    }

    private handleFromUntilFilter(finder: ModelQueryBuilderContract<typeof Dataset, Dataset>, from: string, until: string) {
        const fromDate = this.parseDateWithValidation(from, 'From');
        const untilDate = this.parseDateWithValidation(until, 'Until');

        if (from.length !== until.length) {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'The request has different granularities for the from and until parameters.',
                OaiErrorCodes.BADARGUMENT,
            );
        }

        finder.whereBetween('server_date_published', [fromDate.format('YYYY-MM-DD HH:mm:ss'), untilDate.format('YYYY-MM-DD HH:mm:ss')]);
    }

    private handleFromFilter(finder: ModelQueryBuilderContract<typeof Dataset, Dataset>, from: string) {
        const fromDate = this.parseDateWithValidation(from, 'From');
        const now = dayjs();

        if (fromDate.isAfter(now)) {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'Given from date is greater than now. The given values results in an empty list.',
                OaiErrorCodes.NORECORDSMATCH,
            );
        }

        finder.andWhere('server_date_published', '>=', fromDate.format('YYYY-MM-DD HH:mm:ss'));
    }

    private handleUntilFilter(finder: ModelQueryBuilderContract<typeof Dataset, Dataset>, until: string) {
        const untilDate = this.parseDateWithValidation(until, 'Until');

        const earliestPublicationDate = dayjs(this.firstPublishedDataset?.server_date_published.toISO());

        if (earliestPublicationDate.isAfter(untilDate)) {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'earliestDatestamp is greater than given until date. The given values results in an empty list.',
                OaiErrorCodes.NORECORDSMATCH,
            );
        }

        finder.andWhere('server_date_published', '<=', untilDate.format('YYYY-MM-DD HH:mm:ss'));
    }

    private parseDateWithValidation(dateStr: string, label: string) {
        let date = dayjs(dateStr);
        if (!date.isValid()) {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                `${label} date parameter is not valid.`,
                OaiErrorCodes.BADARGUMENT,
            );
        }
        date = dayjs.tz(dateStr, 'Europe/Vienna');
        return date.hour() === 0 ? (label === 'From' ? date.startOf('day') : date.endOf('day')) : date;
    }

    private setParamResumption(res: string, cursor: number, totalIds: number) {
        const tomorrow = dayjs().add(1, 'day').format('YYYY-MM-DDThh:mm:ss[Z]');
        this.xsltParameter['dateDelete'] = tomorrow;
        this.xsltParameter['res'] = res;
        this.xsltParameter['cursor'] = cursor;
        this.xsltParameter['totalIds'] = totalIds;
    }

    private validateAndGetIdentifier(oaiRequest: Dictionary): number {
        // Identifier references metadata Urn, not plain Id!
        // Currently implemented as 'oai:foo.bar.de:{docId}' or 'urn:nbn...-123'
        if (!('identifier' in oaiRequest)) {
            throw new BadOaiModelException('The prefix of the identifier argument is unknown.');
        }
        const dataId = Number(this.getDocumentIdByIdentifier(oaiRequest.identifier));
        if (isNaN(dataId)) {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'The value of the identifier argument is illegal in this repository.',
                OaiErrorCodes.BADARGUMENT,
            );
        }
        return dataId;
    }

    private validateAndGetMetadataPrefix(oaiRequest: Dictionary): string {
        let metadataPrefix = '';
        if ('metadataPrefix' in oaiRequest) {
            metadataPrefix = oaiRequest['metadataPrefix'];
        } else {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'The prefix of the metadata argument is unknown.',
                OaiErrorCodes.BADARGUMENT,
            );
        }
        return metadataPrefix;
    }

    private validateDatasetState(dataset: Dataset): void {
        if (dataset.server_state == null || !this.deliveringDocumentStates.includes(dataset.server_state)) {
            throw new OaiModelException(
                StatusCodes.INTERNAL_SERVER_ERROR,
                'Document is not available for OAI export!',
                OaiErrorCodes.NORECORDSMATCH,
            );
        }
    }

    private async createXmlRecord(dataset: Dataset, datasetNode: XMLBuilder) {
        const domNode = await this.getDatasetXmlDomNode(dataset);

        if (domNode) {
            // add frontdoor url and data-type
            dataset.publish_id && this.addLandingPageAttribute(domNode, dataset.publish_id.toString());
            this.addSpecInformation(domNode, 'data-type:' + dataset.type);

            if (dataset.collections) {
                for (const coll of dataset.collections) {
                    const collRole = coll.collectionRole;
                    this.addSpecInformation(domNode, collRole.oai_name + ':' + coll.number);
                }
            }

            datasetNode.import(domNode);
        }
    }

    private async getDatasetXmlDomNode(dataset: Dataset) {
        const xmlModel = new XmlModel(dataset);
        // xmlModel.setModel(dataset);
        xmlModel.excludeEmptyFields();
        xmlModel.caching = true;
        // const cache = dataset.xmlCache ? dataset.xmlCache : null;
        // dataset.load('xmlCache');
        if (dataset.xmlCache) {
            xmlModel.xmlCache = dataset.xmlCache;
        }

        // return cache.getDomDocument();
        const domDocument: XMLBuilder | null = await xmlModel.getDomDocument();
        return domDocument;
    }

    private addSpecInformation(domNode: XMLBuilder, information: string) {
        domNode.ele('SetSpec').att('Value', information);
    }

    private addLandingPageAttribute(domNode: XMLBuilder, dataid: string) {
        const baseDomain = process.env.OAI_BASE_DOMAIN || 'localhost';
        const url = 'https://' + getDomain(baseDomain) + '/dataset/' + dataid;
        // add attribute du dataset xml element
        domNode.att('landingpage', url);
    }

    private getDocumentIdByIdentifier(oaiIdentifier: string): string {
        const identifierParts: string[] = oaiIdentifier.split(':'); // explode(":", $oaiIdentifier);
        const dataId: string = identifierParts[2];
        // switch (identifierParts[0]) {
        //     case 'oai':
        //         if (isset($identifierParts[2])) {
        //             $dataId = $identifierParts[2];
        //         }
        //         break;
        //     default:
        //         throw new OaiModelException(
        //             'The prefix of the identifier argument is unknown.',
        //             OaiModelError::BADARGUMENT
        //         );
        //         break;
        // }

        // if (empty($dataId) or !preg_match('/^\d+$/', $dataId)) {
        //     throw new OaiModelException(
        //         'The value of the identifier argument is unknown or illegal in this repository.',
        //         OaiModelError::IDDOESNOTEXIST
        //     );

        return dataId;
    }

    private async getSetsForCollections(): Promise<Dictionary> {
        const sets: { [key: string]: string } = {} as Dictionary;

        const collections = await Collection.query()
            .select('name', 'number', 'role_id')
            .whereHas('collectionRole', (query) => {
                query.where('visible_oai', true);
            })
            .preload('collectionRole');

        collections.forEach((collection) => {
            // if collection has a collection role (classification like ddc):
            if (collection.number) {
                // collection.load('collectionRole');
                const setSpec = collection.collectionRole?.oai_name + ':' + collection.number;
                sets[setSpec] = `Set ${collection.number} '${collection.name}'`;
            }
        });
        return sets;
    }

    private async getSetsForDatasetTypes(): Promise<Dictionary> {
        const sets: { [key: string]: string } = {} as Dictionary;

        const datasets: Array<Dataset> = await Dataset.query().select('type').where('server_state', 'published');

        datasets.forEach((dataset) => {
            if (dataset.type && false == preg_match(this.sampleRegEx, dataset.type)) {
                const msg = `Invalid SetSpec (data-type='${dataset.type}').
                Allowed characters are [${this.sampleRegEx}].`;
                // Log::error("OAI-PMH: $msg");
                logger.error(`OAI-PMH: ${msg}`);
                return;
            }
            const setSpec = 'data-type:' + dataset.type;
            sets[setSpec] = `Set for document type '${dataset.type}'`;
        });
        return sets;
    }

    private handleIllegalVerb() {
        this.xsltParameter['oai_error_code'] = 'badVerb';
        this.xsltParameter['oai_error_message'] = 'The verb provided in the request is illegal.';
    }

    /**
     * Helper method to build a browser fingerprint by combining:
     * - User-Agent header,
     * - the IP address,
     * - Accept-Language header,
     * - current timestamp rounded to the hour.
     *
     * Every new hour, this will return a different fingerprint.
     */
    private getBrowserFingerprint(request: Request): string {
        const userAgent = request.header('user-agent') || 'unknown';
        // Check for X-Forwarded-For header to use the client IP from the proxy if available.
        const xForwardedFor = request.header('x-forwarded-for');
        let ip = request.ip();
        // console.log(ip);
        if (xForwardedFor) {
            // X-Forwarded-For may contain a comma-separated list of IPs; the first one is the client IP.
            ip = xForwardedFor.split(',')[0].trim();
            // console.log('xforwardedfor ip' + ip);
        }
        const locale = request.header('accept-language') || 'default';
        // Round the current time to the start of the hour.
        const timestampHour = dayjs().startOf('hour').format('YYYY-MM-DDTHH');
        return `${userAgent}-${ip}-${locale}-${timestampHour}`;
    }
}