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

import static org.schabi.newpipe.extractor.services.youtube.YoutubeParsingHelper.DISABLE_PRETTY_PRINT_PARAMETER;
import static org.schabi.newpipe.extractor.services.youtube.YoutubeParsingHelper.YOUTUBEI_V1_URL;
import static org.schabi.newpipe.extractor.services.youtube.YoutubeParsingHelper.getJsonPostResponse;
import static org.schabi.newpipe.extractor.services.youtube.YoutubeParsingHelper.getKey;
import static org.schabi.newpipe.extractor.services.youtube.YoutubeParsingHelper.prepareDesktopJsonBuilder;
import static org.schabi.newpipe.extractor.utils.Utils.isNullOrEmpty;

import com.grack.nanojson.JsonArray;
import com.grack.nanojson.JsonObject;
import com.grack.nanojson.JsonWriter;

import org.schabi.newpipe.extractor.InfoItem;
import org.schabi.newpipe.extractor.MultiInfoItemsCollector;
import org.schabi.newpipe.extractor.Page;
import org.schabi.newpipe.extractor.StreamingService;
import org.schabi.newpipe.extractor.channel.ChannelTabExtractor;
import org.schabi.newpipe.extractor.downloader.Downloader;
import org.schabi.newpipe.extractor.exceptions.ExtractionException;
import org.schabi.newpipe.extractor.linkhandler.ListLinkHandler;
import org.schabi.newpipe.extractor.localization.TimeAgoParser;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

public class YoutubeChannelVideosTabExtractor extends ChannelTabExtractor {
    private final JsonObject tabRenderer;
    private final String channelName;
    private final String channelUrl;

    public YoutubeChannelVideosTabExtractor(final StreamingService service,
                                            final ListLinkHandler linkHandler,
                                            final JsonObject tabRenderer,
                                            final String channelName,
                                            final String channelUrl) {
        super(service, linkHandler);
        this.tabRenderer = tabRenderer;
        this.channelName = channelName;
        this.channelUrl = channelUrl;
    }

    @Override
    public void onFetchPage(@Nonnull final Downloader downloader)
            throws IOException, ExtractionException {
        // nothing to do, all data was already fetched and is stored in the link handler
    }

    @Nonnull
    @Override
    public InfoItemsPage<InfoItem> getInitialPage() throws IOException, ExtractionException {
        final MultiInfoItemsCollector collector = new MultiInfoItemsCollector(getServiceId());

        final JsonObject tabContent = tabRenderer.getObject("content");

        JsonArray items = tabContent
                .getObject("sectionListRenderer")
                .getArray("contents").getObject(0).getObject("itemSectionRenderer")
                .getArray("contents").getObject(0).getObject("gridRenderer").getArray("items");

        if (items.isEmpty()) {
            items = tabContent.getObject("richGridRenderer").getArray("contents");
        }

        final List<String> channelIds = new ArrayList<>();
        channelIds.add(channelName);
        channelIds.add(channelUrl);
        final JsonObject continuation = collectStreamsFrom(collector, items, channelIds);

        return new InfoItemsPage<>(collector, getNextPageFrom(continuation, channelIds));
    }

    @Override
    public InfoItemsPage<InfoItem> getPage(final Page page)
            throws IOException, ExtractionException {
        if (page == null || isNullOrEmpty(page.getUrl())) {
            throw new IllegalArgumentException("Page doesn't contain an URL");
        }

        final List<String> channelIds = page.getIds();

        final MultiInfoItemsCollector collector = new MultiInfoItemsCollector(getServiceId());

        final JsonObject ajaxJson = getJsonPostResponse("browse", page.getBody(),
                getExtractorLocalization());

        final JsonObject sectionListContinuation = ajaxJson.getArray("onResponseReceivedActions")
                .getObject(0)
                .getObject("appendContinuationItemsAction");

        final JsonObject continuation = collectStreamsFrom(collector, sectionListContinuation
                .getArray("continuationItems"), channelIds);

        return new InfoItemsPage<>(collector, getNextPageFrom(continuation, channelIds));
    }

    @Nullable
    private Page getNextPageFrom(final JsonObject continuations,
                                 final List<String> channelIds)
            throws IOException, ExtractionException {
        if (isNullOrEmpty(continuations)) {
            return null;
        }

        final JsonObject continuationEndpoint = continuations.getObject("continuationEndpoint");
        final String continuation = continuationEndpoint.getObject("continuationCommand")
                .getString("token");

        final byte[] body = JsonWriter.string(prepareDesktopJsonBuilder(getExtractorLocalization(),
                        getExtractorContentCountry())
                        .value("continuation", continuation)
                        .done())
                .getBytes(StandardCharsets.UTF_8);

        return new Page(YOUTUBEI_V1_URL + "browse?key=" + getKey()
                + DISABLE_PRETTY_PRINT_PARAMETER, null, channelIds, null, body);
    }

    /**
     * Collect streams from an array of items
     *
     * @param collector  the collector where videos will be committed
     * @param videos     the array to get videos from
     * @param channelIds the ids of the channel, which are its name and its URL
     * @return the continuation object
     */
    private JsonObject collectStreamsFrom(@Nonnull final MultiInfoItemsCollector collector,
                                          @Nonnull final JsonArray videos,
                                          @Nonnull final List<String> channelIds) {
        collector.reset();

        final String uploaderName = channelIds.get(0);
        final String uploaderUrl = channelIds.get(1);
        final TimeAgoParser timeAgoParser = getTimeAgoParser();

        JsonObject continuation = null;

        for (final Object object : videos) {
            final JsonObject video = (JsonObject) object;
            if (video.has("gridVideoRenderer")) {
                collector.commit(new YoutubeStreamInfoItemExtractor(
                        video.getObject("gridVideoRenderer"), timeAgoParser) {
                    @Override
                    public String getUploaderName() {
                        return uploaderName;
                    }

                    @Override
                    public String getUploaderUrl() {
                        return uploaderUrl;
                    }
                });
            } else if (video.has("richItemRenderer")) {
                collector.commit(new YoutubeStreamInfoItemExtractor(
                        video.getObject("richItemRenderer")
                                .getObject("content").getObject("videoRenderer"), timeAgoParser) {
                    @Override
                    public String getUploaderName() {
                        return uploaderName;
                    }

                    @Override
                    public String getUploaderUrl() {
                        return uploaderUrl;
                    }
                });

            } else if (video.has("continuationItemRenderer")) {
                continuation = video.getObject("continuationItemRenderer");
            }
        }

        return continuation;
    }
}