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

import com.grack.nanojson.JsonArray;
import com.grack.nanojson.JsonObject;
import com.grack.nanojson.JsonParser;
import com.grack.nanojson.JsonParserException;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.Function;
import org.mozilla.javascript.ScriptableObject;
import org.schabi.newpipe.extractor.MediaFormat;
import org.schabi.newpipe.extractor.NewPipe;
import org.schabi.newpipe.extractor.StreamingService;
import org.schabi.newpipe.extractor.downloader.Downloader;
import org.schabi.newpipe.extractor.downloader.Request;
import org.schabi.newpipe.extractor.downloader.Response;
import org.schabi.newpipe.extractor.exceptions.ContentNotAvailableException;
import org.schabi.newpipe.extractor.exceptions.ExtractionException;
import org.schabi.newpipe.extractor.exceptions.ParsingException;
import org.schabi.newpipe.extractor.exceptions.ReCaptchaException;
import org.schabi.newpipe.extractor.linkhandler.LinkHandler;
import org.schabi.newpipe.extractor.localization.TimeAgoParser;
import org.schabi.newpipe.extractor.localization.DateWrapper;
import org.schabi.newpipe.extractor.services.youtube.ItagItem;
import org.schabi.newpipe.extractor.services.youtube.linkHandler.YoutubeParsingHelper;
import org.schabi.newpipe.extractor.stream.*;
import org.schabi.newpipe.extractor.utils.JsonUtils;
import org.schabi.newpipe.extractor.utils.Parser;
import org.schabi.newpipe.extractor.utils.Utils;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/*
 * Created by Christian Schabesberger on 06.08.15.
 *
 * Copyright (C) Christian Schabesberger 2019 <chris.schabesberger@mailbox.org>
 * YoutubeStreamExtractor.java is part of NewPipe.
 *
 * NewPipe is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * NewPipe is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with NewPipe.  If not, see <http://www.gnu.org/licenses/>.
 */

public class YoutubeStreamExtractor extends StreamExtractor {
    private static final String TAG = YoutubeStreamExtractor.class.getSimpleName();

    /*//////////////////////////////////////////////////////////////////////////
    // Exceptions
    //////////////////////////////////////////////////////////////////////////*/

    public class DecryptException extends ParsingException {
        DecryptException(String message, Throwable cause) {
            super(message, cause);
        }
    }

    public class SubtitlesException extends ContentNotAvailableException {
        SubtitlesException(String message, Throwable cause) {
            super(message, cause);
        }
    }

    /*//////////////////////////////////////////////////////////////////////////*/

    private Document doc;
    @Nullable
    private JsonObject playerArgs;
    @Nonnull
    private final Map<String, String> videoInfoPage = new HashMap<>();
    private JsonObject playerResponse;

    @Nonnull
    private List<SubtitlesInfo> subtitlesInfos = new ArrayList<>();

    private boolean isAgeRestricted;

    public YoutubeStreamExtractor(StreamingService service, LinkHandler linkHandler) {
        super(service, linkHandler);
    }

    /*//////////////////////////////////////////////////////////////////////////
    // Impl
    //////////////////////////////////////////////////////////////////////////*/

    @Nonnull
    @Override
    public String getName() throws ParsingException {
        assertPageFetched();
        try {
            return playerResponse.getObject("videoDetails").getString("title");

        } catch (Exception e) {
            // fallback HTML method
            String name = null;
            try {
                name = doc.select("meta[name=title]").attr(CONTENT);
            } catch (Exception ignored) {}

            if (name == null) {
                throw new ParsingException("Could not get name", e);
            }
            return name;
        }
    }

    @Override
    public String getTextualUploadDate() throws ParsingException {
        if (getStreamType().equals(StreamType.LIVE_STREAM)) {
            return null;
        }

        try {
            return playerResponse.getObject("microformat").getObject("playerMicroformatRenderer").getString("publishDate");
        } catch (Exception e) {
            String uploadDate = null;
            try {
                uploadDate = doc.select("meta[itemprop=datePublished]").attr(CONTENT);
            } catch (Exception ignored) {}

            if (uploadDate == null) {
                throw new ParsingException("Could not get upload date", e);
            }
            return uploadDate;
        }
    }

    @Override
    public DateWrapper getUploadDate() throws ParsingException {
        final String textualUploadDate = getTextualUploadDate();

        if (textualUploadDate == null) {
            return null;
        }

        return new DateWrapper(YoutubeParsingHelper.parseDateFrom(textualUploadDate));
    }

    @Nonnull
    @Override
    public String getThumbnailUrl() throws ParsingException {
        assertPageFetched();
        try {
            JsonArray thumbnails = playerResponse.getObject("videoDetails").getObject("thumbnail").getArray("thumbnails");
            // the last thumbnail is the one with the highest resolution
            return thumbnails.getObject(thumbnails.size() - 1).getString("url");

        } catch (Exception e) {
            String url = null;
            try {
                url = doc.select("link[itemprop=\"thumbnailUrl\"]").first().attr("abs:href");
            } catch (Exception ignored) {}

            if (url == null) {
                throw new ParsingException("Could not get thumbnail url", e);
            }
            return url;
        }

    }

    @Nonnull
    @Override
    public String getDescription() throws ParsingException {
        assertPageFetched();
        try {
            // first try to get html-formatted description
            return parseHtmlAndGetFullLinks(doc.select("p[id=\"eow-description\"]").first().html());
        } catch (Exception e) {
            try {
                // fallback to raw non-html description
                return playerResponse.getObject("videoDetails").getString("shortDescription");
            } catch (Exception ignored) {
                throw new ParsingException("Could not get the description", e);
            }
        }
    }

    // onclick="yt.www.watch.player.seekTo(0*3600+00*60+00);return false;"
    // :00 is NOT recognized as a timestamp in description or comments.
    // 0:00 is recognized in both description and comments.
    // https://www.youtube.com/watch?v=4cccfDXu1vA
    private final static Pattern DESCRIPTION_TIMESTAMP_ONCLICK_REGEX = Pattern.compile(
        "seekTo\\("
            + "(?:(\\d+)\\*3600\\+)?"  // hours?
            + "(\\d+)\\*60\\+"  // minutes
            + "(\\d+)"  // seconds
            + "\\)");

    @SafeVarargs
    private static <T> T coalesce(T... args) {
        for (T arg : args) {
            if (arg != null) return arg;
        }
        throw new IllegalArgumentException("all arguments to coalesce() were null");
    }

    private String parseHtmlAndGetFullLinks(String descriptionHtml)
            throws MalformedURLException, UnsupportedEncodingException, ParsingException {
        final Document description = Jsoup.parse(descriptionHtml, getUrl());
        for(Element a : description.select("a")) {
            final String rawUrl = a.attr("abs:href");
            final URL redirectLink = new URL(rawUrl);

            final Matcher onClickTimestamp;
            final String queryString;
            if ((onClickTimestamp = DESCRIPTION_TIMESTAMP_ONCLICK_REGEX.matcher(a.attr("onclick")))
                    .find()) {
                a.removeAttr("onclick");

                String hours = coalesce(onClickTimestamp.group(1), "0");
                String minutes = onClickTimestamp.group(2);
                String seconds = onClickTimestamp.group(3);

                int timestamp = 0;
                timestamp += Integer.parseInt(hours) * 3600;
                timestamp += Integer.parseInt(minutes) * 60;
                timestamp += Integer.parseInt(seconds);

                String setTimestamp = "&t=" + timestamp;

                // Even after clicking https://youtu.be/...?t=6,
                // getUrl() is https://www.youtube.com/watch?v=..., never youtu.be, never &t=.
                a.attr("href", getUrl() + setTimestamp);

            } else if((queryString = redirectLink.getQuery()) != null) {
                // if the query string is null we are not dealing with a redirect link,
                // so we don't need to override it.
                final String link =
                        Parser.compatParseMap(queryString).get("q");

                if(link != null) {
                    // if link is null the a tag is a hashtag.
                    // They refer to the youtube search. We do not handle them.
                    a.text(link);
                    a.attr("href", link);
                } else if(redirectLink.toString().contains("https://www.youtube.com/")) {
                    a.text(redirectLink.toString());
                    a.attr("href", redirectLink.toString());
                }
            } else if(redirectLink.toString().contains("https://www.youtube.com/")) {
                descriptionHtml = descriptionHtml.replace(rawUrl, redirectLink.toString());
                a.text(redirectLink.toString());
                a.attr("href", redirectLink.toString());
            }
        }
        return description.select("body").first().html();
    }

    @Override
    public int getAgeLimit() throws ParsingException {
        assertPageFetched();
        if (!isAgeRestricted) {
            return NO_AGE_LIMIT;
        }
        try {
            return Integer.valueOf(doc.select("meta[property=\"og:restrictions:age\"]")
                    .attr(CONTENT).replace("+", ""));
        } catch (Exception e) {
            throw new ParsingException("Could not get age restriction");
        }
    }

    @Override
    public long getLength() throws ParsingException {
        assertPageFetched();

        try {
            String duration = playerResponse
                    .getObject("videoDetails")
                    .getString("lengthSeconds");
            return Long.parseLong(duration);
        } catch (Exception e) {
            try {
                String durationMs = playerResponse
                        .getObject("streamingData")
                        .getArray("formats")
                        .getObject(0)
                        .getString("approxDurationMs");
                return Math.round(Long.parseLong(durationMs) / 1000f);
            } catch (Exception ignored) {
                throw new ParsingException("Could not get duration", e);
            }
        }
    }

    /**
     * Attempts to parse (and return) the offset to start playing the video from.
     *
     * @return the offset (in seconds), or 0 if no timestamp is found.
     */
    @Override
    public long getTimeStamp() throws ParsingException {
        return getTimestampSeconds("((#|&|\\?)t=\\d{0,3}h?\\d{0,3}m?\\d{1,3}s?)");
    }

    @Override
    public long getViewCount() throws ParsingException {
        assertPageFetched();
        try {
            if (getStreamType().equals(StreamType.LIVE_STREAM)) {
                return getLiveStreamWatchingCount();
            } else {
                return Long.parseLong(playerResponse.getObject("videoDetails").getString("viewCount"));
            }
        } catch (Exception e) {
            try {
                return Long.parseLong(doc.select("meta[itemprop=interactionCount]").attr(CONTENT));
            } catch (Exception ignored) {
                throw new ParsingException("Could not get view count", e);
            }
        }
    }

    private long getLiveStreamWatchingCount() throws ExtractionException, IOException, JsonParserException {
        // https://www.youtube.com/youtubei/v1/updated_metadata?alt=json&key=
        String innerTubeKey = null, clientVersion = null;
        if (playerArgs != null && !playerArgs.isEmpty()) {
            innerTubeKey = playerArgs.getString("innertube_api_key");
            clientVersion = playerArgs.getString("innertube_context_client_version");
        } else if (!videoInfoPage.isEmpty()) {
            innerTubeKey = videoInfoPage.get("innertube_api_key");
            clientVersion = videoInfoPage.get("innertube_context_client_version");
        }

        if (innerTubeKey == null || innerTubeKey.isEmpty()) {
            throw new ExtractionException("Couldn't get innerTube key");
        }

        if (clientVersion == null || clientVersion.isEmpty()) {
            throw new ExtractionException("Couldn't get innerTube client version");
        }

        final String metadataUrl = "https://www.youtube.com/youtubei/v1/updated_metadata?alt=json&key=" + innerTubeKey;
        final byte[] dataBody = ("{\"context\":{\"client\":{\"clientName\":1,\"clientVersion\":\"" + clientVersion + "\"}}" +
                ",\"videoId\":\"" + getId() + "\"}").getBytes("UTF-8");
        final Response response = getDownloader().execute(Request.newBuilder()
                .post(metadataUrl, dataBody)
                .addHeader("Content-Type", "application/json")
                .build());
        final JsonObject jsonObject = JsonParser.object().from(response.responseBody());

        for (Object actionEntry : jsonObject.getArray("actions")) {
            if (!(actionEntry instanceof JsonObject)) continue;
            final JsonObject entry = (JsonObject) actionEntry;

            final JsonObject updateViewershipAction = entry.getObject("updateViewershipAction", null);
            if (updateViewershipAction == null) continue;

            final JsonArray viewCountRuns = JsonUtils.getArray(updateViewershipAction, "viewership.videoViewCountRenderer.viewCount.runs");
            if (viewCountRuns.isEmpty()) continue;

            final JsonObject textObject = viewCountRuns.getObject(0);
            if (!textObject.has("text")) {
                throw new ExtractionException("Response don't have \"text\" element");
            }

            return Long.parseLong(Utils.removeNonDigitCharacters(textObject.getString("text")));
        }

        throw new ExtractionException("Could not find correct results in response");
    }

    @Override
    public long getLikeCount() throws ParsingException {
        assertPageFetched();
        String likesString = "";
        try {
            Element button = doc.select("button.like-button-renderer-like-button").first();
            try {
                likesString = button.select("span.yt-uix-button-content").first().text();
            } catch (NullPointerException e) {
                //if this kicks in our button has no content and therefore ratings must be disabled
                if (playerResponse.getObject("videoDetails").getBoolean("allowRatings")) {
                    throw new ParsingException("Ratings are enabled even though the like button is missing", e);
                }
                return -1;
            }
            return Integer.parseInt(Utils.removeNonDigitCharacters(likesString));
        } catch (NumberFormatException nfe) {
            throw new ParsingException("Could not parse \"" + likesString + "\" as an Integer", nfe);
        } catch (Exception e) {
            throw new ParsingException("Could not get like count", e);
        }
    }

    @Override
    public long getDislikeCount() throws ParsingException {
        assertPageFetched();
        String dislikesString = "";
        try {
            Element button = doc.select("button.like-button-renderer-dislike-button").first();
            try {
                dislikesString = button.select("span.yt-uix-button-content").first().text();
            } catch (NullPointerException e) {
                //if this kicks in our button has no content and therefore ratings must be disabled
                if (playerResponse.getObject("videoDetails").getBoolean("allowRatings")) {
                    throw new ParsingException("Ratings are enabled even though the dislike button is missing", e);
                }
                return -1;
            }
            return Integer.parseInt(Utils.removeNonDigitCharacters(dislikesString));
        } catch (NumberFormatException nfe) {
            throw new ParsingException("Could not parse \"" + dislikesString + "\" as an Integer", nfe);
        } catch (Exception e) {
            throw new ParsingException("Could not get dislike count", e);
        }
    }

    @Nonnull
    @Override
    public String getUploaderUrl() throws ParsingException {
        assertPageFetched();
        try {
            return "https://www.youtube.com/channel/" +
                    playerResponse.getObject("videoDetails").getString("channelId");
        } catch (Exception e) {
            String uploaderUrl = null;
            try {
                uploaderUrl = doc.select("div[class=\"yt-user-info\"]").first().children()
                        .select("a").first().attr("abs:href");
            } catch (Exception ignored) {}

            if (uploaderUrl == null) {
                throw new ParsingException("Could not get channel link", e);
            }
            return uploaderUrl;
        }
    }

    @Nonnull
    @Override
    public String getUploaderName() throws ParsingException {
        assertPageFetched();
        try {
            return playerResponse.getObject("videoDetails").getString("author");
        } catch (Exception e) {
            String name = null;
            try {
                name = doc.select("div.yt-user-info").first().text();
            } catch (Exception ignored) {}

            if (name == null) {
                throw new ParsingException("Could not get uploader name");
            }
            return name;
        }
    }

    @Nonnull
    @Override
    public String getUploaderAvatarUrl() throws ParsingException {
        assertPageFetched();

        String uploaderAvatarUrl = null;
        try {
            uploaderAvatarUrl = doc.select("a[class*=\"yt-user-photo\"]").first()
                    .select("img").first()
                    .attr("abs:data-thumb");
        } catch (Exception e) {//todo: add fallback method
            throw new ParsingException("Could not get uploader avatar url", e);
        }

        if (uploaderAvatarUrl == null) {
            throw new ParsingException("Could not get uploader avatar url");
        }
        return uploaderAvatarUrl;
    }

    @Nonnull
    @Override
    public String getDashMpdUrl() throws ParsingException {
        assertPageFetched();
        try {
            String dashManifestUrl;
            if (videoInfoPage.containsKey("dashmpd")) {
                dashManifestUrl = videoInfoPage.get("dashmpd");
            } else if (playerArgs != null && playerArgs.isString("dashmpd")) {
                dashManifestUrl = playerArgs.getString("dashmpd", "");
            } else {
                return "";
            }

            if (!dashManifestUrl.contains("/signature/")) {
                String encryptedSig = Parser.matchGroup1("/s/([a-fA-F0-9\\.]+)", dashManifestUrl);
                String decryptedSig;

                decryptedSig = decryptSignature(encryptedSig, decryptionCode);
                dashManifestUrl = dashManifestUrl.replace("/s/" + encryptedSig, "/signature/" + decryptedSig);
            }

            return dashManifestUrl;
        } catch (Exception e) {
            throw new ParsingException("Could not get dash manifest url", e);
        }
    }

    @Nonnull
    @Override
    public String getHlsUrl() throws ParsingException {
        assertPageFetched();

        try {
            return playerResponse.getObject("streamingData").getString("hlsManifestUrl");
        } catch (Exception e) {
            if (playerArgs != null && playerArgs.isString("hlsvp")) {
                return playerArgs.getString("hlsvp");
            } else {
                throw new ParsingException("Could not get hls manifest url", e);
            }
        }
    }

    @Override
    public List<AudioStream> getAudioStreams() throws ExtractionException {
        assertPageFetched();
        List<AudioStream> audioStreams = new ArrayList<>();
        try {
            for (Map.Entry<String, ItagItem> entry : getItags(ADAPTIVE_FORMATS, ItagItem.ItagType.AUDIO).entrySet()) {
                ItagItem itag = entry.getValue();

                AudioStream audioStream = new AudioStream(entry.getKey(), itag.getMediaFormat(), itag.avgBitrate);
                if (!Stream.containSimilarStream(audioStream, audioStreams)) {
                    audioStreams.add(audioStream);
                }
            }
        } catch (Exception e) {
            throw new ParsingException("Could not get audio streams", e);
        }

        return audioStreams;
    }

    @Override
    public List<VideoStream> getVideoStreams() throws ExtractionException {
        assertPageFetched();
        List<VideoStream> videoStreams = new ArrayList<>();
        try {
            for (Map.Entry<String, ItagItem> entry : getItags(FORMATS, ItagItem.ItagType.VIDEO).entrySet()) {
                ItagItem itag = entry.getValue();

                VideoStream videoStream = new VideoStream(entry.getKey(), itag.getMediaFormat(), itag.resolutionString);
                if (!Stream.containSimilarStream(videoStream, videoStreams)) {
                    videoStreams.add(videoStream);
                }
            }
        } catch (Exception e) {
            throw new ParsingException("Could not get video streams", e);
        }

        return videoStreams;
    }

    @Override
    public List<VideoStream> getVideoOnlyStreams() throws ExtractionException {
        assertPageFetched();
        List<VideoStream> videoOnlyStreams = new ArrayList<>();
        try {
            for (Map.Entry<String, ItagItem> entry : getItags(ADAPTIVE_FORMATS, ItagItem.ItagType.VIDEO_ONLY).entrySet()) {
                ItagItem itag = entry.getValue();

                VideoStream videoStream = new VideoStream(entry.getKey(), itag.getMediaFormat(), itag.resolutionString, true);
                if (!Stream.containSimilarStream(videoStream, videoOnlyStreams)) {
                    videoOnlyStreams.add(videoStream);
                }
            }
        } catch (Exception e) {
            throw new ParsingException("Could not get video only streams", e);
        }

        return videoOnlyStreams;
    }

    @Override
    @Nonnull
    public List<SubtitlesStream> getSubtitlesDefault() throws IOException, ExtractionException {
        return getSubtitles(MediaFormat.TTML);
    }

    @Override
    @Nonnull
    public List<SubtitlesStream> getSubtitles(final MediaFormat format) throws IOException, ExtractionException {
        assertPageFetched();
        List<SubtitlesStream> subtitles = new ArrayList<>();
        for (final SubtitlesInfo subtitlesInfo : subtitlesInfos) {
            subtitles.add(subtitlesInfo.getSubtitle(format));
        }
        return subtitles;
    }

    @Override
    public StreamType getStreamType() throws ParsingException {
        assertPageFetched();
        try {
            if (!playerResponse.getObject("streamingData").has(FORMATS) ||
                    (playerArgs != null && playerArgs.has("ps") && playerArgs.get("ps").toString().equals("live"))) {
                return StreamType.LIVE_STREAM;
            }
        } catch (Exception e) {
            throw new ParsingException("Could not get stream type", e);
        }
        return StreamType.VIDEO_STREAM;
    }

    @Override
    public StreamInfoItem getNextStream() throws IOException, ExtractionException {
        assertPageFetched();
        try {
            StreamInfoItemsCollector collector = new StreamInfoItemsCollector(getServiceId());
            final TimeAgoParser timeAgoParser = getTimeAgoParser();

            Elements watch = doc.select("div[class=\"watch-sidebar-section\"]");
            if (watch.size() < 1) {
                return null;// prevent the snackbar notification "report error" on age-restricted videos
            }

            collector.commit(extractVideoPreviewInfo(watch.first().select("li").first(), timeAgoParser));
            return collector.getItems().get(0);
        } catch (Exception e) {
            throw new ParsingException("Could not get next video", e);
        }
    }

    @Override
    public StreamInfoItemsCollector getRelatedStreams() throws IOException, ExtractionException {
        assertPageFetched();
        try {
            StreamInfoItemsCollector collector = new StreamInfoItemsCollector(getServiceId());
            final TimeAgoParser timeAgoParser = getTimeAgoParser();

            Element ul = doc.select("ul[id=\"watch-related\"]").first();
            if (ul != null) {
                for (Element li : ul.children()) {
                    // first check if we have a playlist. If so leave them out
                    if (li.select("a[class*=\"content-link\"]").first() != null) {
                        collector.commit(extractVideoPreviewInfo(li, timeAgoParser));
                    }
                }
            }
            return collector;
        } catch (Exception e) {
            throw new ParsingException("Could not get related videos", e);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getErrorMessage() {
        StringBuilder errorReason;
        Element errorElement = doc.select("h1[id=\"unavailable-message\"]").first();

        if (errorElement == null) {
            errorReason = null;
        } else {
            String errorMessage = errorElement.text();
            if (errorMessage == null || errorMessage.isEmpty()) {
                errorReason = null;
            } else {
                errorReason = new StringBuilder(errorMessage);
                errorReason.append("  ");
                errorReason.append(doc.select("[id=\"unavailable-submessage\"]").first().text());
            }
        }

        return errorReason != null ? errorReason.toString() : "";
    }

    /*//////////////////////////////////////////////////////////////////////////
    // Fetch page
    //////////////////////////////////////////////////////////////////////////*/

    private static final String FORMATS = "formats";
    private static final String ADAPTIVE_FORMATS = "adaptiveFormats";
    private static final String HTTPS = "https:";
    private static final String CONTENT = "content";
    private static final String DECRYPTION_FUNC_NAME = "decrypt";

    private static final String VERIFIED_URL_PARAMS = "&has_verified=1&bpctr=9999999999";

    private final static String DECYRYPTION_SIGNATURE_FUNCTION_REGEX =
            "([\\w$]+)\\s*=\\s*function\\((\\w+)\\)\\{\\s*\\2=\\s*\\2\\.split\\(\"\"\\)\\s*;";
    private final static String DECRYPTION_AKAMAIZED_STRING_REGEX =
            "yt\\.akamaized\\.net/\\)\\s*\\|\\|\\s*.*?\\s*c\\s*&&\\s*d\\.set\\([^,]+\\s*,\\s*(:encodeURIComponent\\s*\\()([a-zA-Z0-9$]+)\\(";
    private final static String DECRYPTION_AKAMAIZED_SHORT_STRING_REGEX =
            "\\bc\\s*&&\\s*d\\.set\\([^,]+\\s*,\\s*(:encodeURIComponent\\s*\\()([a-zA-Z0-9$]+)\\(";

    private volatile String decryptionCode = "";

    private String pageHtml = null;

    @Override
    public void onFetchPage(@Nonnull Downloader downloader) throws IOException, ExtractionException {
        final String verifiedUrl = getUrl() + VERIFIED_URL_PARAMS;
        final Response response = downloader.get(verifiedUrl, getExtractorLocalization());
        pageHtml = response.responseBody();
        doc = YoutubeParsingHelper.parseAndCheckPage(verifiedUrl, response);

        final String playerUrl;
        // Check if the video is age restricted
        if (!doc.select("meta[property=\"og:restrictions:age\"]").isEmpty()) {
            final EmbeddedInfo info = getEmbeddedInfo();
            final String videoInfoUrl = getVideoInfoUrl(getId(), info.sts);
            final String infoPageResponse = downloader.get(videoInfoUrl, getExtractorLocalization()).responseBody();
            videoInfoPage.putAll(Parser.compatParseMap(infoPageResponse));
            playerUrl = info.url;
            isAgeRestricted = true;
        } else {
            final JsonObject ytPlayerConfig = getPlayerConfig();
            playerArgs = getPlayerArgs(ytPlayerConfig);
            playerUrl = getPlayerUrl(ytPlayerConfig);
            isAgeRestricted = false;
        }
        playerResponse = getPlayerResponse();

        if (decryptionCode.isEmpty()) {
            decryptionCode = loadDecryptionCode(playerUrl);
        }

        if (subtitlesInfos.isEmpty()) {
            subtitlesInfos.addAll(getAvailableSubtitlesInfo());
        }
    }

    private JsonObject getPlayerConfig() throws ParsingException {
        try {
            String ytPlayerConfigRaw = Parser.matchGroup1("ytplayer.config\\s*=\\s*(\\{.*?\\});", pageHtml);
            return JsonParser.object().from(ytPlayerConfigRaw);
        } catch (Parser.RegexException e) {
            String errorReason = getErrorMessage();
            switch (errorReason) {
                case "":
                    throw new ContentNotAvailableException("Content not available: player config empty", e);
                default:
                    throw new ContentNotAvailableException("Content not available", e);
            }
        } catch (Exception e) {
            throw new ParsingException("Could not parse yt player config", e);
        }
    }

    private JsonObject getPlayerArgs(JsonObject playerConfig) throws ParsingException {
        JsonObject playerArgs;

        //attempt to load the youtube js player JSON arguments
        try {
            playerArgs = playerConfig.getObject("args");
        } catch (Exception e) {
            throw new ParsingException("Could not parse yt player config", e);
        }

        return playerArgs;
    }

    private String getPlayerUrl(JsonObject playerConfig) throws ParsingException {
        try {
            // The Youtube service needs to be initialized by downloading the
            // js-Youtube-player. This is done in order to get the algorithm
            // for decrypting cryptic signatures inside certain stream urls.
            String playerUrl;

            JsonObject ytAssets = playerConfig.getObject("assets");
            playerUrl = ytAssets.getString("js");

            if (playerUrl.startsWith("//")) {
                playerUrl = HTTPS + playerUrl;
            }
            return playerUrl;
        } catch (Exception e) {
            throw new ParsingException("Could not load decryption code for the Youtube service.", e);
        }
    }

    private JsonObject getPlayerResponse() throws ParsingException {
        try {
            String playerResponseStr;
            if(playerArgs != null) {
                playerResponseStr = playerArgs.getString("player_response");
            } else {
                playerResponseStr = videoInfoPage.get("player_response");
            }
            return JsonParser.object().from(playerResponseStr);
        } catch (Exception e) {
            throw new ParsingException("Could not parse yt player response", e);
        }
    }

    @Nonnull
    private EmbeddedInfo getEmbeddedInfo() throws ParsingException, ReCaptchaException {
        try {
            final Downloader downloader = NewPipe.getDownloader();
            final String embedUrl = "https://www.youtube.com/embed/" + getId();
            final String embedPageContent = downloader.get(embedUrl, getExtractorLocalization()).responseBody();

            // Get player url
            final String assetsPattern = "\"assets\":.+?\"js\":\\s*(\"[^\"]+\")";
            String playerUrl = Parser.matchGroup1(assetsPattern, embedPageContent)
                    .replace("\\", "").replace("\"", "");
            if (playerUrl.startsWith("//")) {
                playerUrl = HTTPS + playerUrl;
            }

            try {
                // Get embed sts
                final String stsPattern = "\"sts\"\\s*:\\s*(\\d+)";
                final String sts = Parser.matchGroup1(stsPattern, embedPageContent);
                return new EmbeddedInfo(playerUrl, sts);
            } catch (Exception i) {
                // if it failes we simply reply with no sts as then it does not seem to be necessary
                return new EmbeddedInfo(playerUrl, "");
            }

        } catch (IOException e) {
            throw new ParsingException(
                    "Could load decryption code form restricted video for the Youtube service.", e);
        }
    }

    private String loadDecryptionCode(String playerUrl) throws DecryptException {
        try {
            Downloader downloader = NewPipe.getDownloader();
            if (!playerUrl.contains("https://youtube.com")) {
                //sometimes the https://youtube.com part does not get send with
                //than we have to add it by hand
                playerUrl = "https://youtube.com" + playerUrl;
            }

            final String playerCode = downloader.get(playerUrl, getExtractorLocalization()).responseBody();
            final String decryptionFunctionName = getDecryptionFuncName(playerCode);

            final String functionPattern = "("
                    + decryptionFunctionName.replace("$", "\\$")
                    + "=function\\([a-zA-Z0-9_]+\\)\\{.+?\\})";
            final String decryptionFunction = "var " + Parser.matchGroup1(functionPattern, playerCode) + ";";

            final String helperObjectName =
                    Parser.matchGroup1(";([A-Za-z0-9_\\$]{2})\\...\\(", decryptionFunction);
            final String helperPattern =
                    "(var " + helperObjectName.replace("$", "\\$") + "=\\{.+?\\}\\};)";
            final String helperObject =
                    Parser.matchGroup1(helperPattern, playerCode.replace("\n", ""));

            final String callerFunction =
                    "function " + DECRYPTION_FUNC_NAME + "(a){return " + decryptionFunctionName + "(a);}";

            return helperObject + decryptionFunction + callerFunction;
        } catch (IOException ioe) {
            throw new DecryptException("Could not load decrypt function", ioe);
        } catch (Exception e) {
            throw new DecryptException("Could not parse decrypt function ", e);
        }
    }

    private String decryptSignature(String encryptedSig, String decryptionCode) throws DecryptException {
        Context context = Context.enter();
        context.setOptimizationLevel(-1);
        Object result;
        try {
            ScriptableObject scope = context.initStandardObjects();
            context.evaluateString(scope, decryptionCode, "decryptionCode", 1, null);
            Function decryptionFunc = (Function) scope.get("decrypt", scope);
            result = decryptionFunc.call(context, scope, scope, new Object[]{encryptedSig});
        } catch (Exception e) {
            throw new DecryptException("could not get decrypt signature", e);
        } finally {
            Context.exit();
        }
        return result == null ? "" : result.toString();
    }

    private String getDecryptionFuncName(String playerCode) throws DecryptException {
        String decryptionFunctionName;
        // Cascading things in catch is ugly, but its faster than running a match before getting the actual name
        // to se if the function can actually be found with the given regex.
        // However if this cascading should propably be cleaned up somehow as it looks a bit weird.
        try {
            decryptionFunctionName = Parser.matchGroup1(DECYRYPTION_SIGNATURE_FUNCTION_REGEX, playerCode);
        } catch (Parser.RegexException re) {
            try {
                decryptionFunctionName = Parser.matchGroup1(DECRYPTION_AKAMAIZED_SHORT_STRING_REGEX, playerCode);
            } catch (Parser.RegexException re2) {
                try {
                    decryptionFunctionName = Parser.matchGroup1(DECRYPTION_AKAMAIZED_STRING_REGEX, playerCode);
                } catch (Parser.RegexException re3) {
                    throw new DecryptException("Could not find decrypt function with any of the given patterns.", re);
                }
            }
        }
        return decryptionFunctionName;
    }

    @Nonnull
    private List<SubtitlesInfo> getAvailableSubtitlesInfo() throws SubtitlesException {
        // If the video is age restricted getPlayerConfig will fail
        if(isAgeRestricted) return Collections.emptyList();

        final JsonObject captions;
        if (!playerResponse.has("captions")) {
            // Captions does not exist
            return Collections.emptyList();
        }
        captions = playerResponse.getObject("captions");

        final JsonObject renderer = captions.getObject("playerCaptionsTracklistRenderer", new JsonObject());
        final JsonArray captionsArray = renderer.getArray("captionTracks", new JsonArray());
        // todo: use this to apply auto translation to different language from a source language
        final JsonArray autoCaptionsArray = renderer.getArray("translationLanguages", new JsonArray());

        // This check is necessary since there may be cases where subtitles metadata do not contain caption track info
        // e.g. https://www.youtube.com/watch?v=-Vpwatutnko
        final int captionsSize = captionsArray.size();
        if(captionsSize == 0) return Collections.emptyList();

        List<SubtitlesInfo> result = new ArrayList<>();
        for (int i = 0; i < captionsSize; i++) {
            final String languageCode = captionsArray.getObject(i).getString("languageCode");
            final String baseUrl = captionsArray.getObject(i).getString("baseUrl");
            final String vssId = captionsArray.getObject(i).getString("vssId");

            if (languageCode != null && baseUrl != null && vssId != null) {
                final boolean isAutoGenerated = vssId.startsWith("a.");
                result.add(new SubtitlesInfo(baseUrl, languageCode, isAutoGenerated));
            }
        }

        return result;
    }
    /*//////////////////////////////////////////////////////////////////////////
    // Data Class
    //////////////////////////////////////////////////////////////////////////*/

    private class EmbeddedInfo {
        final String url;
        final String sts;

        EmbeddedInfo(final String url, final String sts) {
            this.url = url;
            this.sts = sts;
        }
    }

    private class SubtitlesInfo {
        final String cleanUrl;
        final String languageCode;
        final boolean isGenerated;

        public SubtitlesInfo(final String baseUrl, final String languageCode, final boolean isGenerated) {
            this.cleanUrl = baseUrl
                    .replaceAll("&fmt=[^&]*", "") // Remove preexisting format if exists
                    .replaceAll("&tlang=[^&]*", ""); // Remove translation language
            this.languageCode = languageCode;
            this.isGenerated = isGenerated;
        }

        public SubtitlesStream getSubtitle(final MediaFormat format) {
            return new SubtitlesStream(format, languageCode, cleanUrl + "&fmt=" + format.getSuffix(), isGenerated);
        }
    }

    /*//////////////////////////////////////////////////////////////////////////
    // Utils
    //////////////////////////////////////////////////////////////////////////*/

    @Nonnull
    private static String getVideoInfoUrl(final String id, final String sts) {
        return "https://www.youtube.com/get_video_info?" + "video_id=" + id +
                "&eurl=https://youtube.googleapis.com/v/" + id +
                "&sts=" + sts + "&ps=default&gl=US&hl=en";
    }

    private Map<String, ItagItem> getItags(String streamingDataKey, ItagItem.ItagType itagTypeWanted) throws ParsingException {
        Map<String, ItagItem> urlAndItags = new LinkedHashMap<>();
        JsonObject streamingData = playerResponse.getObject("streamingData");
        if (!streamingData.has(streamingDataKey)) {
            return urlAndItags;
        }

        JsonArray formats = streamingData.getArray(streamingDataKey);
        for (int i = 0; i != formats.size(); ++i) {
            JsonObject formatData = formats.getObject(i);
            int itag = formatData.getInt("itag");

            if (ItagItem.isSupported(itag)) {
                try {
                    ItagItem itagItem = ItagItem.getItag(itag);
                    if (itagItem.itagType == itagTypeWanted) {
                        String streamUrl;
                        if (formatData.has("url")) {
                            streamUrl = formatData.getString("url");
                        } else {
                            // this url has an encrypted signature
                            Map<String, String> cipher = Parser.compatParseMap(formatData.getString("cipher"));
                            streamUrl = cipher.get("url") + "&" + cipher.get("sp") + "=" + decryptSignature(cipher.get("s"), decryptionCode);
                        }

                        urlAndItags.put(streamUrl, itagItem);
                    }
                } catch (UnsupportedEncodingException ignored) {

                }
            }
        }

        return urlAndItags;
    }

    /**
     * Provides information about links to other videos on the video page, such as related videos.
     * This is encapsulated in a StreamInfoItem object, which is a subset of the fields in a full StreamInfo.
     */
    private StreamInfoItemExtractor extractVideoPreviewInfo(final Element li, final TimeAgoParser timeAgoParser) {
        return new YoutubeStreamInfoItemExtractor(li, timeAgoParser) {

            @Override
            public String getUrl() throws ParsingException {
                return li.select("a.content-link").first().attr("abs:href");
            }

            @Override
            public String getName() throws ParsingException {
                //todo: check NullPointerException causing
                return li.select("span.title").first().text();
                //this page causes the NullPointerException, after finding it by searching for "tjvg":
                //https://www.youtube.com/watch?v=Uqg0aEhLFAg
            }

            @Override
            public String getUploaderName() throws ParsingException {
                return li.select("span[class*=\"attribution\"").first()
                        .select("span").first().text();
            }

            @Override
            public String getUploaderUrl() throws ParsingException {
                return ""; // The uploader is not linked
            }

            @Override
            public String getTextualUploadDate() throws ParsingException {
                return "";
            }

            @Override
            public String getThumbnailUrl() throws ParsingException {
                Element img = li.select("img").first();
                String thumbnailUrl = img.attr("abs:src");
                // Sometimes youtube sends links to gif files which somehow seem to not exist
                // anymore. Items with such gif also offer a secondary image source. So we are going
                // to use that if we caught such an item.
                if (thumbnailUrl.contains(".gif")) {
                    thumbnailUrl = img.attr("data-thumb");
                }
                if (thumbnailUrl.startsWith("//")) {
                    thumbnailUrl = HTTPS + thumbnailUrl;
                }
                return thumbnailUrl;
            }
        };
    }

	@Nonnull
	@Override
	public List<Frameset> getFrames() throws ExtractionException {
		try {
			final String script = doc.select("#player-api").first().siblingElements().select("script").html();
			int p = script.indexOf("ytplayer.config");
			if (p == -1) {
				return Collections.emptyList();
			}
			p = script.indexOf('{', p);
			int e = script.indexOf("ytplayer.load", p);
			if (e == -1) {
				return Collections.emptyList();
			}
			JsonObject jo = JsonParser.object().from(script.substring(p, e - 1));
			final String resp = jo.getObject("args").getString("player_response");
			jo = JsonParser.object().from(resp);
			final String[] spec = jo.getObject("storyboards").getObject("playerStoryboardSpecRenderer").getString("spec").split("\\|");
			final String url = spec[0];
			final ArrayList<Frameset> result = new ArrayList<>(spec.length - 1);
			for (int i = 1; i < spec.length; ++i) {
				final String[] parts = spec[i].split("#");
				if (parts.length != 8) {
					continue;
				}
				final int frameWidth = Integer.parseInt(parts[0]);
				final int frameHeight = Integer.parseInt(parts[1]);
				final int totalCount = Integer.parseInt(parts[2]);
				final int framesPerPageX = Integer.parseInt(parts[3]);
				final int framesPerPageY = Integer.parseInt(parts[4]);
				final String baseUrl = url.replace("$L", String.valueOf(i - 1)).replace("$N", parts[6]) + "&sigh=" + parts[7];
				final List<String> urls;
				if (baseUrl.contains("$M")) {
					final int totalPages = (int) Math.ceil(totalCount / (double) (framesPerPageX * framesPerPageY));
					urls = new ArrayList<>(totalPages);
					for (int j = 0; j < totalPages; j++) {
						urls.add(baseUrl.replace("$M", String.valueOf(j)));
					}
				} else {
					urls = Collections.singletonList(baseUrl);
				}
				result.add(new Frameset(
						urls,
						frameWidth,
						frameHeight,
						totalCount,
						framesPerPageX,
						framesPerPageY
				));
			}
			result.trimToSize();
			return result;
		} catch (Exception e) {
			throw new ExtractionException(e);
		}
	}

    @Override
    public String getHost() throws ParsingException {
        return "";
    }

    @Override
    public String getPrivacy() throws ParsingException {
        return "";
    }

    @Override
    public String getCategory() throws ParsingException {
        return "";
    }

    @Override
    public String getLicence() throws ParsingException {
        return "";
    }

    @Override
    public String getStreamInfoLanguage() throws ParsingException {
        return "";
    }

    @Nonnull
    @Override
    public List<String> getTags() throws ParsingException {
        return new ArrayList<>();
    }
}