NewPipeExtractor/extractor/src/main/java/org/schabi/newpipe/extractor/services/peertube/extractors/PeertubeTrendingExtractor.java

package org.schabi.newpipe.extractor.services.peertube.extractors;

import com.grack.nanojson.JsonArray;
import com.grack.nanojson.JsonObject;
import com.grack.nanojson.JsonParser;
import org.jsoup.helper.StringUtil;
import org.schabi.newpipe.extractor.StreamingService;
import org.schabi.newpipe.extractor.downloader.Downloader;
import org.schabi.newpipe.extractor.downloader.Response;
import org.schabi.newpipe.extractor.exceptions.ExtractionException;
import org.schabi.newpipe.extractor.exceptions.ParsingException;
import org.schabi.newpipe.extractor.kiosk.KioskExtractor;
import org.schabi.newpipe.extractor.linkhandler.ListLinkHandler;
import org.schabi.newpipe.extractor.stream.StreamInfoItem;
import org.schabi.newpipe.extractor.stream.StreamInfoItemsCollector;
import org.schabi.newpipe.extractor.utils.JsonUtils;
import org.schabi.newpipe.extractor.utils.Parser;
import org.schabi.newpipe.extractor.utils.Parser.RegexException;

import java.io.IOException;

public class PeertubeTrendingExtractor extends KioskExtractor<StreamInfoItem> {

    private static final String START_KEY = "start";
    private static final String COUNT_KEY = "count";
    private static final int ITEMS_PER_PAGE = 12;
    private static final String START_PATTERN = "start=(\\d*)";

    private InfoItemsPage<StreamInfoItem> initPage;
    private long total;

    public PeertubeTrendingExtractor(StreamingService streamingService, ListLinkHandler linkHandler, String kioskId) {
        super(streamingService, linkHandler, kioskId);
    }

    @Override
    public String getName() throws ParsingException {
        return getId();
    }

    @Override
    public InfoItemsPage<StreamInfoItem> getInitialPage() throws IOException, ExtractionException {
        super.fetchPage();
        return initPage;
    }

    private void collectStreamsFrom(StreamInfoItemsCollector collector, JsonObject json, String pageUrl) throws ParsingException {
        JsonArray contents;
        try {
            contents = (JsonArray) JsonUtils.getValue(json, "data");
        } catch (Exception e) {
            throw new ParsingException("Unable to extract kiosk info", e);
        }

        String baseUrl = getBaseUrl();
        for (Object c : contents) {
            if (c instanceof JsonObject) {
                final JsonObject item = (JsonObject) c;
                PeertubeStreamInfoItemExtractor extractor = new PeertubeStreamInfoItemExtractor(item, baseUrl);
                collector.commit(extractor);
            }
        }

    }

    @Override
    public String getNextPageUrl() throws IOException, ExtractionException {
        super.fetchPage();
        return initPage.getNextPageUrl();
    }

    @Override
    public InfoItemsPage<StreamInfoItem> getPage(String pageUrl) throws IOException, ExtractionException {
        Response response = getDownloader().get(pageUrl);
        JsonObject json = null;
        if (null != response && !StringUtil.isBlank(response.responseBody())) {
            try {
                json = JsonParser.object().from(response.responseBody());
            } catch (Exception e) {
                throw new ParsingException("Could not parse json data for kiosk info", e);
            }
        }

        StreamInfoItemsCollector collector = new StreamInfoItemsCollector(getServiceId());
        if (json != null) {
            Number number = JsonUtils.getNumber(json, "total");
            if (number != null) this.total = number.longValue();
            collectStreamsFrom(collector, json, pageUrl);
        } else {
            throw new ExtractionException("Unable to get peertube kiosk info");
        }
        return new InfoItemsPage<>(collector, getNextPageUrl(pageUrl));
    }

    @Override
    public void onFetchPage(Downloader downloader) throws IOException, ExtractionException {
        String pageUrl = getUrl() + "&" + START_KEY + "=0&" + COUNT_KEY + "=" + ITEMS_PER_PAGE;
        this.initPage = getPage(pageUrl);
    }

    private String getNextPageUrl(String prevPageUrl) {
        String prevStart;
        try {
            prevStart = Parser.matchGroup1(START_PATTERN, prevPageUrl);
        } catch (RegexException e) {
            return "";
        }
        if (StringUtil.isBlank(prevStart)) return "";
        long nextStart = 0;
        try {
            nextStart = Long.valueOf(prevStart) + ITEMS_PER_PAGE;
        } catch (NumberFormatException e) {
            return "";
        }

        if (nextStart >= total) {
            return "";
        } else {
            return prevPageUrl.replace(START_KEY + "=" + prevStart, START_KEY + "=" + String.valueOf(nextStart));
        }
    }

}