- added earliestPublicationDate for App/Models/Dataset.ts

- new classes TokenWorkerService.ts, TokenWorker.ts and ResumptionToken.ts for using REDIS with paging OAI results
- deletd public/asstes2/langCodeMap.xml: integrated it directly in datasetxml2oai-pmh.xslt
- added redis npm package
- added TokenWorkerProvider.ts for using singleton of TokenWorkerService inside OaiController.ts
- added config/oai.ts for oai related configs from .env-file
- adapted XmlModel.ts for grting domDocument from database

app/Library/Oai/ResumptionToken.ts

@@ -0,0 +1,51 @@
+export default class ResumptionToken {
+    private _documentIds: number[] = [];
+    private _metadataPrefix = '';
+    private _resumptionId = '';
+    private _startPosition = 0;
+    private _totalIds = 0;
+
+    get key(): string {
+        return this.metadataPrefix + this.startPosition + this.totalIds;
+    }
+
+    get documentIds(): number[] {
+        return this._documentIds;
+    }
+
+    set documentIds(idsToStore: number | number[]) {
+        this._documentIds = Array.isArray(idsToStore) ? idsToStore : [idsToStore];
+    }
+
+    get metadataPrefix(): string {
+        return this._metadataPrefix;
+    }
+
+    set metadataPrefix(value: string) {
+        this._metadataPrefix = value;
+    }
+
+    get resumptionId(): string {
+        return this._resumptionId;
+    }
+
+    set resumptionId(resumptionId: string) {
+        this._resumptionId = resumptionId;
+    }
+
+    get startPosition(): number {
+        return this._startPosition;
+    }
+
+    set startPosition(startPosition: number) {
+        this._startPosition = startPosition;
+    }
+
+    get totalIds(): number {
+        return this._totalIds;
+    }
+
+    set totalIds(totalIds: number) {
+        this._totalIds = totalIds;
+    }
+}

app/Library/Oai/TokenWorker.ts

@@ -0,0 +1,10 @@
+import ResumptionToken from './ResumptionToken';
+
+export default interface TokenWorkerContract {
+    ttl: number;
+    isConnected: boolean;
+    connect();
+    close();
+    get(key: string): Promise<ResumptionToken | null>;
+    set(token: ResumptionToken): Promise<string>;
+}

app/Library/Oai/TokenWorkerSerice.ts

@@ -0,0 +1,95 @@
+import ResumptionToken from './ResumptionToken';
+import { createClient, RedisClientType } from 'redis';
+import InternalServerErrorException from 'App/Exceptions/InternalServerException';
+import { sprintf } from 'sprintf-js';
+import dayjs from 'dayjs';
+import TokenWorkerContract from './TokenWorker';
+
+export default class TokenWorkerService implements TokenWorkerContract {
+    protected filePrefix = 'rs_';
+    protected fileExtension = 'txt';
+
+    private cache: RedisClientType;
+    public ttl: number;
+    private url: string;
+    private connected = false;
+
+    constructor(ttl: number) {
+        this.ttl = ttl; // time to live
+        this.url = process.env.REDIS_URL || 'redis://127.0.0.1:6379';
+    }
+
+    public async connect() {
+        this.cache = createClient({ url: this.url });
+        this.cache.on('error', (err) => {
+            this.connected = false;
+            console.log('[Redis] Redis Client Error: ', err);
+        });
+        this.cache.on('connect', () => {
+            this.connected = true;
+        });
+        await this.cache.connect();
+    }
+
+    public get isConnected(): boolean {
+        return this.connected;
+    }
+
+    public async has(key: string): Promise<boolean> {
+        const result = await this.cache.get(key);
+        return result !== undefined && result !== null;
+    }
+
+    public async set(token: ResumptionToken): Promise<string> {
+        const uniqueName = await this.generateUniqueName();
+
+        const serialToken = JSON.stringify(token);
+        await this.cache.setEx(uniqueName, this.ttl, serialToken);
+        return uniqueName;
+    }
+
+    private async generateUniqueName(): Promise<string> {
+        let fc = 0;
+        const uniqueId = dayjs().unix().toString();
+        let uniqueName: string;
+        let cacheKeyExists: boolean;
+        do {
+            // format values
+            // %s - String
+            // %d - Signed decimal number (negative, zero or positive)
+            // [0-9] (Specifies the minimum width held of to the variable value)
+            uniqueName = sprintf('%s%05d', uniqueId, fc++);
+            cacheKeyExists = await this.has(uniqueName);
+        } while (cacheKeyExists);
+        return uniqueName;
+    }
+
+    public async get(key: string): Promise<ResumptionToken | null> {
+        if (!this.cache) {
+            throw new InternalServerErrorException('Dataset is not available for OAI export!');
+        }
+
+        const result = await this.cache.get(key);
+        return result ? this.parseToken(result) : null;
+    }
+
+    private parseToken(result: string): ResumptionToken {
+        const rToken: ResumptionToken = new ResumptionToken();
+        const parsed = JSON.parse(result);
+        Object.assign(rToken, parsed);
+        return rToken;
+    }
+
+    public del(key: string) {
+        this.cache.del(key);
+    }
+
+    public flush() {
+        this.cache.flushAll();
+    }
+
+    public async close() {
+        await this.cache.disconnect();
+        this.connected = false;
+    }
+}