from .common import (get, multi_get, deep_get, multi_deep_get,
    liberal_update, conservative_update, remove_redirect, normalize_url,
    extract_str, extract_formatted_text, extract_int, extract_approx_int,
    extract_date, check_missing_keys, extract_item_info, extract_items,
    extract_response)

import json
import urllib.parse
import traceback
import re

# from https://github.com/ytdl-org/youtube-dl/blob/master/youtube_dl/extractor/youtube.py
_formats = {
    '5': {'ext': 'flv', 'width': 400, 'height': 240, 'acodec': 'mp3', 'audio_bitrate': 64, 'vcodec': 'h263'},
    '6': {'ext': 'flv', 'width': 450, 'height': 270, 'acodec': 'mp3', 'audio_bitrate': 64, 'vcodec': 'h263'},
    '13': {'ext': '3gp', 'acodec': 'aac', 'vcodec': 'mp4v'},
    '17': {'ext': '3gp', 'width': 176, 'height': 144, 'acodec': 'aac', 'audio_bitrate': 24, 'vcodec': 'mp4v'},
    '18': {'ext': 'mp4', 'width': 640, 'height': 360, 'acodec': 'aac', 'audio_bitrate': 96, 'vcodec': 'h264'},
    '22': {'ext': 'mp4', 'width': 1280, 'height': 720, 'acodec': 'aac', 'audio_bitrate': 192, 'vcodec': 'h264'},
    '34': {'ext': 'flv', 'width': 640, 'height': 360, 'acodec': 'aac', 'audio_bitrate': 128, 'vcodec': 'h264'},
    '35': {'ext': 'flv', 'width': 854, 'height': 480, 'acodec': 'aac', 'audio_bitrate': 128, 'vcodec': 'h264'},
    # itag 36 videos are either 320x180 (BaW_jenozKc) or 320x240 (__2ABJjxzNo), audio_bitrate varies as well
    '36': {'ext': '3gp', 'width': 320, 'acodec': 'aac', 'vcodec': 'mp4v'},
    '37': {'ext': 'mp4', 'width': 1920, 'height': 1080, 'acodec': 'aac', 'audio_bitrate': 192, 'vcodec': 'h264'},
    '38': {'ext': 'mp4', 'width': 4096, 'height': 3072, 'acodec': 'aac', 'audio_bitrate': 192, 'vcodec': 'h264'},
    '43': {'ext': 'webm', 'width': 640, 'height': 360, 'acodec': 'vorbis', 'audio_bitrate': 128, 'vcodec': 'vp8'},
    '44': {'ext': 'webm', 'width': 854, 'height': 480, 'acodec': 'vorbis', 'audio_bitrate': 128, 'vcodec': 'vp8'},
    '45': {'ext': 'webm', 'width': 1280, 'height': 720, 'acodec': 'vorbis', 'audio_bitrate': 192, 'vcodec': 'vp8'},
    '46': {'ext': 'webm', 'width': 1920, 'height': 1080, 'acodec': 'vorbis', 'audio_bitrate': 192, 'vcodec': 'vp8'},
    '59': {'ext': 'mp4', 'width': 854, 'height': 480, 'acodec': 'aac', 'audio_bitrate': 128, 'vcodec': 'h264'},
    '78': {'ext': 'mp4', 'width': 854, 'height': 480, 'acodec': 'aac', 'audio_bitrate': 128, 'vcodec': 'h264'},


    # 3D videos
    '82': {'ext': 'mp4', 'height': 360, 'format_note': '3D', 'acodec': 'aac', 'audio_bitrate': 128, 'vcodec': 'h264'},
    '83': {'ext': 'mp4', 'height': 480, 'format_note': '3D', 'acodec': 'aac', 'audio_bitrate': 128, 'vcodec': 'h264'},
    '84': {'ext': 'mp4', 'height': 720, 'format_note': '3D', 'acodec': 'aac', 'audio_bitrate': 192, 'vcodec': 'h264'},
    '85': {'ext': 'mp4', 'height': 1080, 'format_note': '3D', 'acodec': 'aac', 'audio_bitrate': 192, 'vcodec': 'h264'},
    '100': {'ext': 'webm', 'height': 360, 'format_note': '3D', 'acodec': 'vorbis', 'audio_bitrate': 128, 'vcodec': 'vp8'},
    '101': {'ext': 'webm', 'height': 480, 'format_note': '3D', 'acodec': 'vorbis', 'audio_bitrate': 192, 'vcodec': 'vp8'},
    '102': {'ext': 'webm', 'height': 720, 'format_note': '3D', 'acodec': 'vorbis', 'audio_bitrate': 192, 'vcodec': 'vp8'},

    # Apple HTTP Live Streaming
    '91': {'ext': 'mp4', 'height': 144, 'format_note': 'HLS', 'acodec': 'aac', 'audio_bitrate': 48, 'vcodec': 'h264'},
    '92': {'ext': 'mp4', 'height': 240, 'format_note': 'HLS', 'acodec': 'aac', 'audio_bitrate': 48, 'vcodec': 'h264'},
    '93': {'ext': 'mp4', 'height': 360, 'format_note': 'HLS', 'acodec': 'aac', 'audio_bitrate': 128, 'vcodec': 'h264'},
    '94': {'ext': 'mp4', 'height': 480, 'format_note': 'HLS', 'acodec': 'aac', 'audio_bitrate': 128, 'vcodec': 'h264'},
    '95': {'ext': 'mp4', 'height': 720, 'format_note': 'HLS', 'acodec': 'aac', 'audio_bitrate': 256, 'vcodec': 'h264'},
    '96': {'ext': 'mp4', 'height': 1080, 'format_note': 'HLS', 'acodec': 'aac', 'audio_bitrate': 256, 'vcodec': 'h264'},
    '132': {'ext': 'mp4', 'height': 240, 'format_note': 'HLS', 'acodec': 'aac', 'audio_bitrate': 48, 'vcodec': 'h264'},
    '151': {'ext': 'mp4', 'height': 72, 'format_note': 'HLS', 'acodec': 'aac', 'audio_bitrate': 24, 'vcodec': 'h264'},

    # DASH mp4 video
    '133': {'ext': 'mp4', 'height': 240, 'format_note': 'DASH video', 'vcodec': 'h264'},
    '134': {'ext': 'mp4', 'height': 360, 'format_note': 'DASH video', 'vcodec': 'h264'},
    '135': {'ext': 'mp4', 'height': 480, 'format_note': 'DASH video', 'vcodec': 'h264'},
    '136': {'ext': 'mp4', 'height': 720, 'format_note': 'DASH video', 'vcodec': 'h264'},
    '137': {'ext': 'mp4', 'height': 1080, 'format_note': 'DASH video', 'vcodec': 'h264'},
    '138': {'ext': 'mp4', 'format_note': 'DASH video', 'vcodec': 'h264'},  # Height can vary (https://github.com/ytdl-org/youtube-dl/issues/4559)
    '160': {'ext': 'mp4', 'height': 144, 'format_note': 'DASH video', 'vcodec': 'h264'},
    '212': {'ext': 'mp4', 'height': 480, 'format_note': 'DASH video', 'vcodec': 'h264'},
    '264': {'ext': 'mp4', 'height': 1440, 'format_note': 'DASH video', 'vcodec': 'h264'},
    '298': {'ext': 'mp4', 'height': 720, 'format_note': 'DASH video', 'vcodec': 'h264', 'fps': 60},
    '299': {'ext': 'mp4', 'height': 1080, 'format_note': 'DASH video', 'vcodec': 'h264', 'fps': 60},
    '266': {'ext': 'mp4', 'height': 2160, 'format_note': 'DASH video', 'vcodec': 'h264'},

    # Dash mp4 audio
    '139': {'ext': 'm4a', 'format_note': 'DASH audio', 'acodec': 'aac', 'audio_bitrate': 48, 'container': 'm4a_dash'},
    '140': {'ext': 'm4a', 'format_note': 'DASH audio', 'acodec': 'aac', 'audio_bitrate': 128, 'container': 'm4a_dash'},
    '141': {'ext': 'm4a', 'format_note': 'DASH audio', 'acodec': 'aac', 'audio_bitrate': 256, 'container': 'm4a_dash'},
    '256': {'ext': 'm4a', 'format_note': 'DASH audio', 'acodec': 'aac', 'container': 'm4a_dash'},
    '258': {'ext': 'm4a', 'format_note': 'DASH audio', 'acodec': 'aac', 'container': 'm4a_dash'},
    '325': {'ext': 'm4a', 'format_note': 'DASH audio', 'acodec': 'dtse', 'container': 'm4a_dash'},
    '328': {'ext': 'm4a', 'format_note': 'DASH audio', 'acodec': 'ec-3', 'container': 'm4a_dash'},

    # Dash webm
    '167': {'ext': 'webm', 'height': 360, 'width': 640, 'format_note': 'DASH video', 'container': 'webm', 'vcodec': 'vp8'},
    '168': {'ext': 'webm', 'height': 480, 'width': 854, 'format_note': 'DASH video', 'container': 'webm', 'vcodec': 'vp8'},
    '169': {'ext': 'webm', 'height': 720, 'width': 1280, 'format_note': 'DASH video', 'container': 'webm', 'vcodec': 'vp8'},
    '170': {'ext': 'webm', 'height': 1080, 'width': 1920, 'format_note': 'DASH video', 'container': 'webm', 'vcodec': 'vp8'},
    '218': {'ext': 'webm', 'height': 480, 'width': 854, 'format_note': 'DASH video', 'container': 'webm', 'vcodec': 'vp8'},
    '219': {'ext': 'webm', 'height': 480, 'width': 854, 'format_note': 'DASH video', 'container': 'webm', 'vcodec': 'vp8'},
    '278': {'ext': 'webm', 'height': 144, 'format_note': 'DASH video', 'container': 'webm', 'vcodec': 'vp9'},
    '242': {'ext': 'webm', 'height': 240, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    '243': {'ext': 'webm', 'height': 360, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    '244': {'ext': 'webm', 'height': 480, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    '245': {'ext': 'webm', 'height': 480, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    '246': {'ext': 'webm', 'height': 480, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    '247': {'ext': 'webm', 'height': 720, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    '248': {'ext': 'webm', 'height': 1080, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    '271': {'ext': 'webm', 'height': 1440, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    # itag 272 videos are either 3840x2160 (e.g. RtoitU2A-3E) or 7680x4320 (sLprVF6d7Ug)
    '272': {'ext': 'webm', 'height': 2160, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    '302': {'ext': 'webm', 'height': 720, 'format_note': 'DASH video', 'vcodec': 'vp9', 'fps': 60},
    '303': {'ext': 'webm', 'height': 1080, 'format_note': 'DASH video', 'vcodec': 'vp9', 'fps': 60},
    '308': {'ext': 'webm', 'height': 1440, 'format_note': 'DASH video', 'vcodec': 'vp9', 'fps': 60},
    '313': {'ext': 'webm', 'height': 2160, 'format_note': 'DASH video', 'vcodec': 'vp9'},
    '315': {'ext': 'webm', 'height': 2160, 'format_note': 'DASH video', 'vcodec': 'vp9', 'fps': 60},

    # Dash webm audio
    '171': {'ext': 'webm', 'acodec': 'vorbis', 'format_note': 'DASH audio', 'audio_bitrate': 128},
    '172': {'ext': 'webm', 'acodec': 'vorbis', 'format_note': 'DASH audio', 'audio_bitrate': 256},

    # Dash webm audio with opus inside
    '249': {'ext': 'webm', 'format_note': 'DASH audio', 'acodec': 'opus', 'audio_bitrate': 50},
    '250': {'ext': 'webm', 'format_note': 'DASH audio', 'acodec': 'opus', 'audio_bitrate': 70},
    '251': {'ext': 'webm', 'format_note': 'DASH audio', 'acodec': 'opus', 'audio_bitrate': 160},

    # RTMP (unnamed)
    '_rtmp': {'protocol': 'rtmp'},

    # av01 video only formats sometimes served with "unknown" codecs
    '394': {'vcodec': 'av01.0.05M.08'},
    '395': {'vcodec': 'av01.0.05M.08'},
    '396': {'vcodec': 'av01.0.05M.08'},
    '397': {'vcodec': 'av01.0.05M.08'},
}

def _extract_metadata_row_info(video_renderer_info):
    # extract category and music list
    info = {
        'category': None,
        'music_list': [],
    }

    current_song = {}
    for row in deep_get(video_renderer_info, 'metadataRowContainer', 'metadataRowContainerRenderer', 'rows', default=[]):
        row_title = extract_str(deep_get(row, 'metadataRowRenderer', 'title'), default='')
        row_content = extract_str(deep_get(row, 'metadataRowRenderer', 'contents', 0))
        if row_title == 'Category':
            info['category'] = row_content
        elif row_title in ('Song', 'Music'):
            if current_song:
                info['music_list'].append(current_song)
            current_song = {'title': row_content}
        elif row_title == 'Artist':
            current_song['artist'] = row_content
        elif row_title == 'Album':
            current_song['album'] = row_content
        elif row_title == 'Writers':
            current_song['writers'] = row_content
        elif row_title.startswith('Licensed'):
            current_song['licensor'] = row_content
    if current_song:
        info['music_list'].append(current_song)

    return info

def _extract_watch_info_mobile(top_level):
    info = {}
    microformat = deep_get(top_level, 'playerResponse', 'microformat', 'playerMicroformatRenderer', default={})

    family_safe = microformat.get('isFamilySafe')
    if family_safe is None:
        info['age_restricted'] = None
    else:
        info['age_restricted'] = not family_safe
    info['allowed_countries'] = microformat.get('availableCountries', [])
    info['time_published'] = microformat.get('publishDate')

    response = top_level.get('response', {})

    # video info from metadata renderers
    items, _ = extract_items(response, item_types={'slimVideoMetadataRenderer'})
    if items:
        video_info = items[0]['slimVideoMetadataRenderer']
    else:
        print('Failed to extract video metadata')
        video_info = {}

    info.update(_extract_metadata_row_info(video_info))
    info['description'] = extract_str(video_info.get('description'), recover_urls=True)
    info['view_count'] = extract_int(extract_str(video_info.get('expandedSubtitle')))
    info['author'] = extract_str(deep_get(video_info, 'owner', 'slimOwnerRenderer', 'title'))
    info['author_id'] = deep_get(video_info, 'owner', 'slimOwnerRenderer', 'navigationEndpoint', 'browseEndpoint', 'browseId')
    info['title'] = extract_str(video_info.get('title'))
    info['live'] = 'watching' in extract_str(video_info.get('expandedSubtitle'), default='')
    info['unlisted'] = False
    for badge in video_info.get('badges', []):
        if deep_get(badge, 'metadataBadgeRenderer', 'label') == 'Unlisted':
            info['unlisted'] = True
    info['like_count'] = None
    info['dislike_count'] = None
    if not info['time_published']:
        info['time_published'] = extract_date(extract_str(video_info.get('dateText', None)))
    for button in video_info.get('buttons', ()):
        button_renderer = button.get('slimMetadataToggleButtonRenderer', {})

        # all the digits can be found in the accessibility data
        count = extract_int(deep_get(button_renderer, 'button', 'toggleButtonRenderer', 'defaultText', 'accessibility', 'accessibilityData', 'label'))

        # this count doesn't have all the digits, it's like 53K for instance
        dumb_count = extract_int(extract_str(deep_get(button_renderer, 'button', 'toggleButtonRenderer', 'defaultText')))

        # the accessibility text will be "No likes" or "No dislikes" or something like that, but dumb count will be 0
        if dumb_count == 0:
            count = 0

        if 'isLike' in button_renderer:
            info['like_count'] = count
        elif 'isDislike' in button_renderer:
            info['dislike_count'] = count

    # comment section info
    items, _ = extract_items(response, item_types={'commentSectionRenderer'})
    if items:
        comment_info = items[0]['commentSectionRenderer']
        comment_count_text = extract_str(deep_get(comment_info, 'header', 'commentSectionHeaderRenderer', 'countText'))
        if comment_count_text == 'Comments':    # just this with no number, means 0 comments
            info['comment_count'] = 0
        else:
            info['comment_count'] = extract_int(comment_count_text)
        info['comments_disabled'] = False
    else:   # no comment section present means comments are disabled
        info['comment_count'] = 0
        info['comments_disabled'] = True

    # check for limited state
    items, _ = extract_items(response, item_types={'limitedStateMessageRenderer'})
    if items:
        info['limited_state'] = True
    else:
        info['limited_state'] = False

    # related videos
    related, _ = extract_items(response)
    info['related_videos'] = [extract_item_info(renderer) for renderer in related]

    return info

def _extract_watch_info_desktop(top_level):
    info = {
        'comment_count': None,
        'comments_disabled': None,
        'allowed_countries': None,
        'limited_state': None,
    }

    video_info = {}
    for renderer in deep_get(top_level, 'response', 'contents', 'twoColumnWatchNextResults', 'results', 'results', 'contents', default=()):
        if renderer and list(renderer.keys())[0] in ('videoPrimaryInfoRenderer', 'videoSecondaryInfoRenderer'):
            video_info.update(list(renderer.values())[0])

    info.update(_extract_metadata_row_info(video_info))
    info['description'] = extract_str(video_info.get('description', None), recover_urls=True)
    info['time_published'] = extract_date(extract_str(video_info.get('dateText', None)))

    likes_dislikes = deep_get(video_info, 'sentimentBar', 'sentimentBarRenderer', 'tooltip', default='').split('/')
    if len(likes_dislikes) == 2:
        info['like_count'] = extract_int(likes_dislikes[0])
        info['dislike_count'] = extract_int(likes_dislikes[1])
    else:
        info['like_count'] = None
        info['dislike_count'] = None

    info['title'] = extract_str(video_info.get('title', None))
    info['author'] = extract_str(deep_get(video_info, 'owner', 'videoOwnerRenderer', 'title'))
    info['author_id'] = deep_get(video_info, 'owner', 'videoOwnerRenderer', 'navigationEndpoint', 'browseEndpoint', 'browseId')
    info['view_count'] = extract_int(extract_str(deep_get(video_info, 'viewCount', 'videoViewCountRenderer', 'viewCount')))

    related = deep_get(top_level, 'response', 'contents', 'twoColumnWatchNextResults', 'secondaryResults', 'secondaryResults', 'results', default=[])
    info['related_videos'] = [extract_item_info(renderer) for renderer in related]

    return info

def _extract_formats(info, player_response):
    streaming_data = player_response.get('streamingData', {})
    yt_formats = streaming_data.get('formats', []) + streaming_data.get('adaptiveFormats', [])

    info['formats'] = []

    for yt_fmt in yt_formats:
        fmt = {}
        fmt['ext'] = None
        fmt['audio_bitrate'] = None
        fmt['acodec'] = None
        fmt['vcodec'] = None
        fmt['width'] = yt_fmt.get('width')
        fmt['height'] = yt_fmt.get('height')
        fmt['file_size'] = yt_fmt.get('contentLength')
        fmt['audio_sample_rate'] = yt_fmt.get('audioSampleRate')
        fmt['fps'] = yt_fmt.get('fps')
        cipher = dict(urllib.parse.parse_qsl(yt_fmt.get('cipher', '')))
        if cipher:
            fmt['url'] = cipher.get('url')
        else:
            fmt['url'] = yt_fmt.get('url')
        fmt['s'] = cipher.get('s')
        fmt['sp'] = cipher.get('sp')
        fmt.update(_formats.get(str(yt_fmt.get('itag')), {}))

        info['formats'].append(fmt)

def _extract_playability_error(info, player_response, error_prefix=''):
    if info['formats']:
        info['playability_status'] = None
        info['playability_error'] = None
        return

    playability_status = deep_get(player_response, 'playabilityStatus', 'status', default=None)
    info['playability_status'] = playability_status

    playability_reason = extract_str(multi_deep_get(player_response,
        ['playabilityStatus', 'reason'],
        ['playabilityStatus', 'errorScreen', 'playerErrorMessageRenderer', 'reason'],
        default='Could not find playability error')
    )

    if playability_status not in (None, 'OK'):
        info['playability_error'] = error_prefix + playability_reason
    else:
        info['playability_error'] = error_prefix + 'Unknown playability error'

SUBTITLE_FORMATS = ('srv1', 'srv2', 'srv3', 'ttml', 'vtt')
def extract_watch_info(polymer_json):
    info = {'playability_error': None, 'error': None}

    if isinstance(polymer_json, dict):
        top_level = polymer_json
    elif isinstance(polymer_json, (list, tuple)):
        top_level = {}
        for page_part in polymer_json:
            if not isinstance(page_part, dict):
                return {'error': 'Invalid page part'}
            top_level.update(page_part)
    else:
        return {'error': 'Invalid top level polymer data'}

    error = check_missing_keys(top_level,
        ['player', 'args'],
        ['player', 'assets', 'js'],
        ['playerResponse'],
    )
    if error:
        info['playability_error'] = error

    player_args = deep_get(top_level, 'player', 'args', default={})
    player_response = json.loads(player_args['player_response']) if 'player_response' in player_args else {}

    # captions
    info['automatic_caption_languages'] = []
    info['manual_caption_languages'] = []
    info['_manual_caption_language_names'] = {}     # language name written in that language, needed in some cases to create the url
    info['translation_languages'] = []
    captions_info = player_response.get('captions', {})
    info['_captions_base_url'] = normalize_url(deep_get(captions_info, 'playerCaptionsRenderer', 'baseUrl'))
    for caption_track in deep_get(captions_info, 'playerCaptionsTracklistRenderer', 'captionTracks', default=()):
        lang_code = caption_track.get('languageCode')
        if not lang_code:
            continue
        if caption_track.get('kind') == 'asr':
            info['automatic_caption_languages'].append(lang_code)
        else:
            info['manual_caption_languages'].append(lang_code)
        base_url = caption_track.get('baseUrl', '')
        lang_name = deep_get(urllib.parse.parse_qs(urllib.parse.urlparse(base_url).query), 'name', 0)
        if lang_name:
            info['_manual_caption_language_names'][lang_code] = lang_name

    for translation_lang_info in deep_get(captions_info, 'playerCaptionsTracklistRenderer', 'translationLanguages', default=()):
        lang_code = translation_lang_info.get('languageCode')
        if lang_code:
            info['translation_languages'].append(lang_code)
        if translation_lang_info.get('isTranslatable') == False:
            print('WARNING: Found non-translatable caption language')

    # formats
    _extract_formats(info, player_response)

    # playability errors
    _extract_playability_error(info, player_response)

    # check age-restriction
    info['age_restricted'] = (info['playability_status'] == 'LOGIN_REQUIRED' and info['playability_error'] and ' age' in info['playability_error'])

    # base_js (for decryption of signatures)
    info['base_js'] = deep_get(top_level, 'player', 'assets', 'js')
    if info['base_js']:
        info['base_js'] = normalize_url(info['base_js'])
        info['player_name'] = get(info['base_js'].split('/'), -2)
    else:
        info['player_name'] = None

    # extract stuff from visible parts of page
    mobile = 'singleColumnWatchNextResults' in deep_get(top_level, 'response', 'contents', default={})
    if mobile:
        info.update(_extract_watch_info_mobile(top_level))
    else:
        info.update(_extract_watch_info_desktop(top_level))

    # stuff from videoDetails. Use liberal_update to prioritize info from videoDetails over existing info
    vd = deep_get(top_level, 'playerResponse', 'videoDetails', default={})
    liberal_update(info, 'title',      extract_str(vd.get('title')))
    liberal_update(info, 'duration',   extract_int(vd.get('lengthSeconds')))
    liberal_update(info, 'view_count', extract_int(vd.get('viewCount')))
    # videos with no description have a blank string
    liberal_update(info, 'description', vd.get('shortDescription'))
    liberal_update(info, 'id',          vd.get('videoId'))
    liberal_update(info, 'author',      vd.get('author'))
    liberal_update(info, 'author_id',   vd.get('channelId'))
    liberal_update(info, 'live',        vd.get('isLiveContent'))
    conservative_update(info, 'unlisted', not vd.get('isCrawlable', True))  #isCrawlable is false on limited state videos even if they aren't unlisted
    liberal_update(info, 'tags',        vd.get('keywords', []))

    # fallback stuff from microformat
    mf = deep_get(top_level, 'playerResponse', 'microformat', 'playerMicroformatRenderer', default={})
    conservative_update(info, 'title',      extract_str(mf.get('title')))
    conservative_update(info, 'duration', extract_int(mf.get('lengthSeconds')))
    # this gives the view count for limited state videos
    conservative_update(info, 'view_count', extract_int(mf.get('viewCount')))
    conservative_update(info, 'description', extract_str(mf.get('description'), recover_urls=True))
    conservative_update(info, 'author', mf.get('ownerChannelName'))
    conservative_update(info, 'author_id', mf.get('externalChannelId'))
    liberal_update(info, 'unlisted', mf.get('isUnlisted'))
    liberal_update(info, 'category', mf.get('category'))
    liberal_update(info, 'time_published', mf.get('publishDate'))
    liberal_update(info, 'time_uploaded', mf.get('uploadDate'))

    # other stuff
    info['author_url'] = 'https://www.youtube.com/channel/' + info['author_id'] if info['author_id'] else None
    return info

def get_caption_url(info, language, format, automatic=False, translation_language=None):
    '''Gets the url for captions with the given language and format. If automatic is True, get the automatic captions for that language. If translation_language is given, translate the captions from `language` to `translation_language`. If automatic is true and translation_language is given, the automatic captions will be translated.'''
    url = info['_captions_base_url']
    url += '&lang=' + language
    url += '&fmt=' + format
    if automatic:
        url += '&kind=asr'
    elif language in info['_manual_caption_language_names']:
        url += '&name=' + urllib.parse.quote(info['_manual_caption_language_names'][language], safe='')

    if translation_language:
        url += '&tlang=' + translation_language
    return url

def update_with_age_restricted_info(info, video_info_page):
    ERROR_PREFIX = 'Error bypassing age-restriction: '

    video_info = urllib.parse.parse_qs(video_info_page)
    player_response = deep_get(video_info, 'player_response', 0)
    if player_response is None:
        info['playability_error'] = ERROR_PREFIX + 'Could not find player_response in video_info_page'
        return
    try:
        player_response = json.loads(player_response)
    except json.decoder.JSONDecodeError:
        traceback.print_exc()
        info['playability_error'] = ERROR_PREFIX + 'Failed to parse json response'
        return

    _extract_formats(info, player_response)
    _extract_playability_error(info, player_response, error_prefix=ERROR_PREFIX)

def requires_decryption(info):
    return ('formats' in info) and info['formats'] and info['formats'][0]['s']

# adapted from youtube-dl and invidious:
# https://github.com/omarroth/invidious/blob/master/src/invidious/helpers/signatures.cr
decrypt_function_re = re.compile(r'function\(a\)\{(a=a\.split\(""\)[^\}]+)\}')
op_with_arg_re = re.compile(r'[^\.]+\.([^\(]+)\(a,(\d+)\)')
def extract_decryption_function(info, base_js):
    '''Insert decryption function into info. Return error string if not successful.
    Decryption function is a list of list[2] of numbers.
    It is advisable to cache the decryption function (uniquely identified by info['player_name']) so base.js (1 MB) doesn't need to be redownloaded each time'''
    info['decryption_function'] = None
    decrypt_function_match = decrypt_function_re.search(base_js)
    if decrypt_function_match is None:
        return 'Could not find decryption function in base.js'

    function_body = decrypt_function_match.group(1).split(';')[1:-1]
    if not function_body:
        return 'Empty decryption function body'

    var_name = get(function_body[0].split('.'), 0)
    if var_name is None:
        return 'Could not find var_name'

    var_body_match = re.search(r'var ' + re.escape(var_name) + r'=\{(.*?)\};', base_js, flags=re.DOTALL)
    if var_body_match is None:
        return 'Could not find var_body'

    operations = var_body_match.group(1).replace('\n', '').split('},')
    if not operations:
        return 'Did not find any definitions in var_body'
    operations[-1] = operations[-1][:-1]    # remove the trailing '}' since we split by '},' on the others
    operation_definitions = {}
    for op in operations:
        colon_index = op.find(':')
        opening_brace_index = op.find('{')

        if colon_index == -1 or opening_brace_index == -1:
            return 'Could not parse operation'
        op_name = op[:colon_index]
        op_body = op[opening_brace_index+1:]
        if op_body == 'a.reverse()':
            operation_definitions[op_name] = 0
        elif op_body == 'a.splice(0,b)':
            operation_definitions[op_name] = 1
        elif op_body.startswith('var c=a[0]'):
            operation_definitions[op_name] = 2
        else:
            return 'Unknown op_body: ' + op_body

    decryption_function = []
    for op_with_arg in function_body:
        match = op_with_arg_re.fullmatch(op_with_arg)
        if match is None:
            return 'Could not parse operation with arg'
        op_name = match.group(1)
        if op_name not in operation_definitions:
            return 'Unknown op_name: ' + op_name
        op_argument = match.group(2)
        decryption_function.append([operation_definitions[op_name], int(op_argument)])

    info['decryption_function'] = decryption_function
    return False

def _operation_2(a, b):
    c = a[0]
    a[0] = a[b % len(a)]
    a[b % len(a)] = c

def decrypt_signatures(info):
    '''Applies info['decryption_function'] to decrypt all the signatures. Return err.'''
    if not info.get('decryption_function'):
        return 'decryption_function not in info'
    for format in info['formats']:
        if not format['s'] or not format['sp'] or not format['url']:
            print('Warning: s, sp, or url not in format')
            continue

        a = list(format['s'])
        for op, argument in info['decryption_function']:
            if op == 0:
                a.reverse()
            elif op == 1:
                a = a[argument:]
            else:
                _operation_2(a, argument)

        signature = ''.join(a)
        format['url'] += '&' + format['sp'] + '=' + signature
    return False