#!/usr/bin/perl
# Copyright © 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2021 Petr Písař
# Copyright © 2022 Petr Písař
# This is free software.  You may redistribute copies of it under the terms of
# the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
# There is NO WARRANTY, to the extent permitted by law.

# Changelog:
#
# Version 32:
# - Correct parsing pages with multiple iframe players
# (https://ct24.ceskatelevize.cz/domaci/3424616-nove-motoraky-ceskych-drah-nejdou-nastartovat-vyprsela-platnost-softwaru).
# - Correct parsing series pages where first IDEC field is invalid
# (https://www.ceskatelevize.cz/porady/1126672097-otazky-vaclava-moravce/).
# - Support options --help and --version.
#
# Version 31:
# - Adapt to changes noticed from the beginning of December, 2021.
# - Correct a grammar in a few verbose messages.
#
# Version 30:
# - Adapt to changes noticed on 2021-06-25.
# - Non-HTTPS playlist generator redirects POST requests with 301 instead of
# 302 now. Handle the code likewise.
# - Correct grammar in a usage text.
#
# Version 29:
# - Adapt to changes effective since 2018-09-12.
# - Stream servers changed an X509 certificate and it sends full chain now.
# The bundled certificate was removed.
# - Non-HTTPS playlist generator redirects POST requests to HTTPS locations.
# Because libwww-perl does not yet support RFC 7231, the redirection was
# implemented here.
#
# Version 28
# - Adapt to changes effective since 2018-07-17 (a playlist generator requires
# HTTPS schema now, ivys-st10-5.o2tv.cz:443 does not send an intermediate
# certificate).
#
# Version 27
# - Do not mix bottom-level Apple play-list into stream segment's content when
# called with -s option.
# - Add debugging to retrieving bottom-level Apple play-lists and stream
# segments.
#
# Version 26
# - Adapt to changes effective since 2017-02-13.
#
# Version 25
# - Adapt to changes effective since 2016-11-22.
#
# Version 24
# - Adapt to changes effective since 2015-10-16.
# - RTMP mode removed because it's no longer provided by the servers.
# - Encode undefined value as empty string to conform latest jQuery
# (http://www.ceskatelevize.cz/porady/10316155327-horizont-ct24/215411058051016/).
# - If multi-part video is encountered, user has to select one by positional
# argument. One can use `-t' option to list the parts.
# (http://www.ceskatelevize.cz/ivysilani/11177713200-tour-de-france-2015/215471291092002/).
#
# Version 23
# - Adapt to changes effective since 2014-12-18. 
# - Please note that the RTMP streams do not work.
#
# Version 22
# - Adapt to changes in SMIL URL generator definition as needed since
# beginning of December 2014. 
# - Support ct24 portal links
# (http://www.ceskatelevize.cz/ct24/svet/295620-eichler-k-australii-horsi-nez-osamely-vlk-je-zbesily-vlk/)
#
# Version 21
# - Return iframe searcher as iframes have not yet been eradicted as I thought
# (invalid http://www.ceskatelevize.cz/msfotbal/videoarchiv/nejnovejsi/279399-sestrih-utkani-nizozemsko-kostarika/).
# - Support Apple M3U playlist URL served as a SMIL play-list.
#
# Version 20
# - Catch up to major changes on the server side. Not all features are
# available yet.
#
# Version 19
# - Send `type' element not to confuse SMIL playlist genererator as it is
# needed since 2014-05-05. 
#
# Version 18
# - Fix locating JSON. The affected RTMP variant got another argument.
#
# Version 17
# - Fix request for RTMP playlist generator by not sending undefined
#   streamQuality.
#
# Version 16
# - Recognize an error message in new format.
# - Respect *_proxy environment variables.
#
# Version 15
# - Implement short path when overloaded server returns SMIL URL directly.
#
# Version 14
# - Adapt to server changes effective since 2014-02-13. Only RTMP is supported
#   now. The Apple format is unsupported.
# - Require URI::Escape Perl module.
#
# Version 13
# - Rewrite SMIL playlist URL as performed by web interface since 2014-01-31.
#
# Version 12
# - Search SMIL playlist generator URL from web pages as the address changes
#   frequently.
#
# Version 11
# - Implement change of SMIL playlist generator URL as spotted on 2014-01-10.
#   Thanks to Jiri B.
# - Set output encoding for diganostic messages according to locale as
#   messages extracted from web pages are in Czech.
#
# Version 10
# - Implement change of SMIL playlist generator URL as spotted on 2014-01-07.
# 
# Version 9
# - Search for other error message if JSON could not be found. This usually
#   says the client is not supported (not all URLs serves all formats).
# - Improve JSON locator
#   (http://www.ceskatelevize.cz/ivysilani/1126672097-otazky-vaclava-moravce/).
#
# Version 8
# - Adapt to changes in SMIL play-list generator on the Czech Television
# servers. Effective since 2013-05-24.
# - New option `-v' has been added to report retrieved URLs.
#
# Version 7
# - Print stream data in binaru mode. This fixes premature end-of-file on
# DOS-like operating systems.
#
# Version 6
# - Accept iframe player URL with channel name in the file name
# - Send XML-RPC header needed for SMIL generator since 2012-05-09
#
# Version 5
# - Support Apple M3U and MPEG2-TS/MPEG-4 format
# - Improve HTML parser
# - Remove autoStart=false option from iframe player URL to get page with
# JSON instead of similar page with iframe again
# (http://www.ceskatelevize.cz/porady/10316155327-horizont-ct24/)
#
# Version 4
# - Support RTMP app with slashes
# - Report URI in error messages
#
# Version 3:
# - Output in rtmpdump(1) format if `-d' option is specified
# - Do not append playpath to URL if ambigous
#
# Version 2:
# - Output playpath as librtmp option if necessary
# - Perl 5.10 support
# - Find JSON via iframe first and fall back to direct JSON
# - More general example entry page URL in usage output
# - Show content provider error message if exists
#

# Procedure since 2015-10-16
# The hash is at <http://www.ceskatelevize.cz/ct24#live> in an in-line
# javascript:
#
# jQuery.extend(Drupal.settings, {[...]
# media_ivysilani:{hash:"HEXASTRING"},[...]});
#
# Then GET is performed to /ivysilani/embed/iFramePlayerCT24.php?[...] with
# hash=HEXASTRING appended to retrieve iframe HTML code. The URL comes from
# //span[class="media-ivysilani-placeholder"]/@data-url in the entry point as
# computed in
# <http://www.ceskatelevize.cz/ct24/sites/all/themes/custom/ct24/js/video.js>.
#
# Then XMLHttpRequest POST to /ivysilani/ajax/get-client-playlist with x-addr
# HTTP header and playlist[0][type], playlist[0][id], requestUrl, requestSource,
# and type input form is performed.
#
# The x-addr value comes from the PHP page.
# The form values comes from
# <http://imgct.ceskatelevize.cz/global/js/player/ajax-playlist-o2.js?_ts=INTEGER>
# javascript whose address is in the PHP.
#
# It returns JSON:
#
# {"url":"http:\/\/www.ceskatelevize.cz\/ivysilani\/client-playlist\/?key=HEXASTRING2"}
#
# Then GET is performed to the url value. A JSON is returned:
#
# { [...], "playlist":[
#   {"streamUrls":{"main":"http:\/\/80.188.65.18:80\/cdn\/[...]",[...]}
# ] }
# 
# The main streamUrl returns top-level segmented M3U playlist.
# 
# Other code:
# <http://www.ceskatelevize.cz/ct24/sites/all/modules/custom/media_ivysilani/js/media_ivysilani.js>
# <http://www.ceskatelevize.cz/ct24/sites/all/themes/custom/ct24/js/ct24_live.js>


use strict;
use warnings;
use utf8;
use open ':locale';
our $VERSION = 32;

use LWP::UserAgent;
use HTTP::Request::Common;
use HTTP::Response;
use XML::XPath;
use URI;
use URI::Escape;
use JSON 2.0;
use Getopt::Std;
use IO::Handle;


my $SMIL_GENERATOR_NEXT = '/ajax/getSmil.php?url=';
my $ENTRY = 'https://www.ceskatelevize.cz/zive/ct24/';

sub usage {
    return<<EOM;
Usage: ctstream [-v] -A [-t|-l|-f|-s] [--] ENTRY_PAGE [PART] [BITRATE]

Get URLs of the Czech Television video streams for a specific ENTRY_PAGE (e.g.
<$ENTRY>).

If this is the only argument and the video has only one part, output a list of
all available streams in format `BITRATE: URL' separated by a new line. If
the BITRATE is given, only output a URL of the stream with the given rate.

If the video has more parts, you have to specify the part number.

The `-A' option must be specified. HTTP/MPEG-TS/MPEG-4 video will be retrieved.
There exist four levels selected by these options:

  -t  List URLs of top-level Apple M3U playlists for each video part. The output
      are lines in `PART: URL' format. If the PART was specified, only URL of
      the given video part will be printed.

  -l  An Apple M3U play-list pointing to the unbound stream segments will be
      output. This is handy if you have a player that supports the very special
      play-list. Specification can be found at
      <http://tools.ietf.org/html/draft-pantos-http-live-streaming>.

  -f  The Apple play-list will be processed and URLs of the underlying stream
      segmented into files will be printed. Due to nature of the play-list, the
      locators are printed periodically, a new segment a few seconds, possibly
      in an endless loop. Intended workflow is pipe the URLs to an HTTP client
      which echoes the downloaded segments on a standard input of a multimedia
      player. This is the default level. The bit rate must be specified, if
      more bit rates are available.

  -s  The stream segments will be retrieved and dumped to a standard output as
      a continuous stream. You can pipe it to your player. The bit rate must be
      specified if more bit rates are available.

If a `-v' option is specified, additional debugging messages will be printed on
the standard error output.

Version: $VERSION.
Copyright © 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2021 Petr Písař
Copyright © 2022 Petr Písař
This is free software.  You may redistribute copies of it under the terms of
the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
There is NO WARRANTY, to the extent permitted by law.
EOM
}

our ($opt_A, $opt_d, $opt_t, $opt_l, $opt_f, $opt_s, $opt_v);
$Getopt::Std::STANDARD_HELP_VERSION = 1;
sub HELP_MESSAGE {
    print usage();
}
sub VERSION_MESSAGE {
    print "Version: $VERSION.\n";
}
getopts('Adtlfsv') or 
    die usage;

if ($#ARGV < 0 || $#ARGV > 2) {
    die "Bad invocation\n\n" . usage;
}
$ENTRY = shift @ARGV;

if (!($opt_l || $opt_s)) { $opt_f = 1; }


# each that operates on reference to array or hash
# Works with perl 5.10.1 too.
sub eachref {
    my $ref = shift;
            
    if (ref $ref eq 'HASH') {
        # Built-in implementation always supports HASH
        return sub {
            each %$ref;
        }
    }

    if (eval 'each @$ref' ) {
        # Built-in Perl 5.12 implementation
        eval 'return sub { 
            each @$ref;
        }'
    } else {
        # Manual implementation of each ARRAY (needed for Perl < 5.12)
        my $index = -1;
   
        return sub {
            $index++;
            if ($index <= $#$ref) {
                ($index, $$ref[$index]);
            } else {
                ();
            }
        }
    }
}


# Convert nested JSON structure expressed as native hash reference into flat
# array of key and value pairs.
# E.g. { "x" => [ "y" => "1", "z" => undef ] }
# becomes ( "x[0][y]", "1", "x[1][z] => '' ).
# XXX: Since fixing <http://bugs.jquery.com/ticket/8653>, undefined value is
# expressed as empty string instead of 'null' string.
# This is handy when sending nested JSON structure as
# application/x-www-form-urlencoded by HTTP::Request::Common.
sub flatten {
    my ($ref, $prefix) = @_;
    my @output = ();
    my $doeach = eachref($ref);
    while (my ($key, $val) = &$doeach) {
        # TODO: Escape /[[]=]/
        my $id = (defined $prefix) ? $prefix . '[' . $key . ']' : $key;
        if (ref $val eq 'HASH' || ref $val eq 'ARRAY') {
            push @output, flatten($val, $id);
        } else {
            push @output, ($id, $val // '');
        }
    }
    return @output;
}


# Format RTMP URL for librtmp
sub formaturl_librtmp {
    my ($rtmp, $app, $playpath) = @_;

    my $stream_url = $rtmp;
    if ($playpath =~ qr{/} or $app =~ qr{/}) {
        $stream_url .= ' app=' . $app . ' playpath=' . $playpath;
    } else {
        $stream_url .= $app . '/' . $playpath;
    }
}


# Format RTMP URL for librtmp
sub formaturl_rtmpdump {
    my ($rtmp, $app, $playpath) = @_;
    
    my $stream_url = '--rtmp ' . $rtmp;
    if ($playpath =~ qr{/} or $app =~ qr{/}) {
        $stream_url .= ' --app ' . $app . ' --playpath ' . $playpath;
    } else {
        $stream_url .= $app . '/' . $playpath;
    }
}


# Find first pattern match in HTML page, HTML-unescape it and return it.
# Otherwise return undef.
sub htmlgrep {
    my ($html_page, $pattern) = @_;
    my ($text) = ($html_page =~ $pattern);
    if (defined $text) {
        $text =~ s/&gt;/>/g;
        $text =~ s/&lt;/</g;
        $text =~ s/&nbsp;/\xa0/g;
        $text =~ s/&amp;/&/g;
    }
    return $text;
}


# Escape as URI and ampersands in additon
sub shellescape {
    local $_ = URI->new(shift);
    s/&/%26/g;
    return $_;
}


# Try to get JSON request data from HTML page text.
# The page is passed as a first argument. The JSON is located by javascript
# function identifier passed as a second argument.
# Return the JSON data or undef.
# Example: callSOAP({"foo);bar":1});
sub findjson {
    my ($text, $function) = @_;
    htmlgrep($text, qr{
        # Use possesive quantifiers ++, *+ for performance
        \Q$function\E
        \(
        (                                       # The JSON structure is a
            (?:                                 # sequence of quoted strings
                "(?: [^"\\]++ | \\. )*+" | [^)] # and non-quoted
            )*+                                 # non-parentheses.
        )                                       #
        \);
    }x);
}


# Try to get setRequestHeader function arguments from JS page text passed as
# argument.
# Return list (header, value) or undef.
sub findrequestheader {
    local $_ = findjson(shift, 'setRequestHeader');
    if (!defined) { return undef; }
    return (m/'([^']*)', '([^']*)'/);
}


# Return URL of the only video/@src in the SMIL playlist.
# Arguments is playlist as string, URL of the playlist, and
# playlist as XML::XPath object.
sub extract_url_from_m3u_smil {
    my ($smil, $smil_url, $parser) = @_;

    my $videos =
        $parser->find('/data/smilRoot/body/video');
    if ($videos->size <= 0) {
        die "No videos found in SMIL playlist <" . $smil_url . ">:\n" .
            $smil . "\n";
    }
    my @bitrate_url_pairs = ();
    foreach my $video ($videos->get_nodelist) {
        my $suffix = $video->getAttribute('src');
        if (! defined $suffix) {
            print STDERR q{Missing `video/@src' attribute} . "\n";
            next;
        }
        # Build stream URL. This is now an HTTP URL.
        return $suffix;
    }

    die "No video URL found.\n";
}


# Return array of { bitrate => INTEGER, url => URL } found in RTMP SMIL play
# list. Arguments is playlist as string, URL of the playlist,
# playlist as XML::XPath object and boolean signaling URL format (true for
# rtmpdump format, false for librtmp format).
sub extract_urls_from_rtmp_smil {
    my ($smil, $smil_url, $parser, $opt_d) = @_;

    my $videos =
        $parser->find('/data/smilRoot/body/switchItem/video[@enabled=true()]');
    if ($videos->size <= 0) {
        die "No videos found in SMIL playlist <" . $smil_url . ">:\n" .
            $smil . "\n";
    }
    my @bitrate_url_pairs = ();
    foreach my $video ($videos->get_nodelist) {
        my $suffix = $video->getAttribute('src');
        if (! defined $suffix) {
            print STDERR q{Missing `video/@src' attribute} . "\n";
            next;
        }
        my $prefix = $video->getParentNode->getAttribute('base');
        if (! defined $suffix) {
            print STDERR
                q{Missing `video/../@base' attribute for video } .
                "`$suffix'\n";
            next;
        }
        my $bitrate = $video->getAttribute('system-bitrate');
        if (! defined $suffix) {
            print STDERR
                q{Missing `video/@system-bitrate' attribute for video } .
                "`$suffix'\n";
            next;
        }

        # Build stream URL. Because RTMP URL can be ambigous, 
        # applications accept aditional arguments separated by space
        # (the space must not be URI-encoded).
        my $stream_url;
        {
            my $rtmp = URI->new($prefix);
            my $app = substr($rtmp->path_query, 1);
            $rtmp->path('/');
            $rtmp->query(undef);
            my $playpath = URI->new($suffix);
            if ($opt_d) {
                $stream_url = formaturl_rtmpdump($rtmp, $app, $playpath);
            } else {
                $stream_url = formaturl_librtmp($rtmp, $app, $playpath);
            }
        }

        ## Build stream URL. This is now an HTTP URL.
        #my $stream_url = URI->new_abs($suffix, $prefix);

        # Store URL
        push @bitrate_url_pairs, {'bitrate' => $bitrate, 'url' => $stream_url};
    }

    return @bitrate_url_pairs;
}


# Print segment URLs or their content found in bottom-level Apple M3U
# play-list. This function can never return if live stream is served by
# a server.
# Arguments are URL of the playlist, LWP::UserAgent object, and boolean
# signalling content of stream segments should be printed instead of their
# URLs.
# See <http://tools.ietf.org/html/draft-pantos-http-live-streaming>.
sub iterate_bottom_apple_m3u {
    my ($m3u_url, $ua, $stream_content) = @_;
    autoflush STDOUT 1;
    my $reload = 1;
    my $last_segment = -1;
    my $target_duration;

    while ($reload) {
        # Get bottom-level Apple MPEG play-list.
        if ($opt_v) {
            print STDERR "Getting bottom-level Apple play-list <$m3u_url>\n";
        }
        my $response = $ua->request(GET $m3u_url);
        $response->is_success or
            die "Could not get bottom-level Apple M3U play-list from <" .
                $m3u_url . ">: " . $response->status_line . "\n";
        if ($opt_v) {
            print STDERR "Retrieved bottom-level Apple play-list is:\n" . 
                "===BEGIN INPUT===\n" . $response->decoded_content .
                "\n===END INPUT===\n";
        }
        my $retrieved_at = time;
        my $duration;
        my $sequence = 0;
        for (split(/(\r)?\n/, $response->decoded_content)) {
            if (! defined) { next; }
            if (/\A#EXT-X-TARGETDURATION:(\d+)/) {
                $target_duration = $1;
                next;
            }
            if (/\A#EXT-X-MEDIA-SEQUENCE:(\d+)/) {
                $sequence = $1;
                next;
            }
            if (/\A#EXT-X-ENDLIST\b/) {
                $reload = 0;
                next;
            }
            if (/\A#EXTINF:(\d+)/) {
                $duration = $1;
                next;
            }
            if (/\A[^#]/) {
                if (! defined $duration) {
                    print STDERR
                        'Stray URL in bottom-level Apple play-list from <' .
                        $m3u_url . ">:\n" . $response->decoded_content . "\n";
                    next;
                }
                if ($sequence > $last_segment) {
                    my $segment_url = URI->new_abs($_, $m3u_url);
                    if ($stream_content) {
                        # Get segment content.
                        if ($opt_v) {
                            print STDERR "Getting segment content from <" .
                                $segment_url . ">\n";
                        }
                        binmode STDOUT;
                        $ua->set_my_handler('response_data',
                            sub { print $_[3]; 1; }, 'm_code' => 2);
                        my $response = $ua->request(GET $segment_url);
                        $ua->set_my_handler('response_data',
                            undef, 'm_code' => 2);
                        $response->is_success or
                            die "Could not get stream segment content from <" .
                                $segment_url . ">: " .
                                $response->status_line . "\n";
                        if ($opt_v) {
                            print STDERR "Segment content retrieved successfully.\n";
                        }
                    } else {
                        print $segment_url, "\n";
                    }
                    $last_segment = $sequence;
                }
                $duration = undef;
                $sequence++;
                next;
            }
        }
        if (! defined $target_duration || $last_segment == -1) {
            die 'No target duration or URL found in bottom-level Apple " .
                "play-list from <' .
                $m3u_url . ">:\n" . $response->decoded_content . "\n";
        }
        if ($reload) {
            my $sleep = $target_duration - (time - $retrieved_at);
            if ($sleep > 0) {
                if ($opt_v) {
                    print STDERR "Going to sleep for $sleep seconds.\n";
                }
                sleep $sleep;
            }
        }
    }
}


# Return array of { bitrate => INTEGER, url => URL } found in top-level
# Apple M3U play-list. Returned URLs are locators of bottom-level Apple M3U
# play-list for given bitrate. The play-list specification is on
# <http://tools.ietf.org/html/draft-pantos-http-live-streaming>.
# Arguments are URL of the playlist and LWP::UserAgent object.
sub extract_urls_from_top_apple_m3u {
    my ($m3u_url, $ua) = @_;
    my @bitrate_url_pairs = ();

    # Get top-level Apple MPEG playlist.
    my $response = $ua->request(GET $m3u_url);
    $response->is_success or
        die "Could not get top-level Apple M3U play-list from <" .
            $m3u_url . ">: " . $response->status_line . "\n";
    my $bitrate;
    for (split(/(\r)?\n/, $response->decoded_content)) {
        if (! defined) { next; }
        if (/\A#EXT-X-STREAM-INF:(?:.*,)?BANDWIDTH=(\d+)/) {
            $bitrate = $1;
            next;
        }
        if (/\A[^#]/) {
            if (! defined $bitrate) {
                print STDERR 'Stray URL in top-level Apple play-list from <' .
                    $m3u_url . ">:\n" . $response->decoded_content . "\n";
                next;
            }
            push @bitrate_url_pairs,
                {'bitrate' => $bitrate, 'url' => URI->new_abs($_, $m3u_url)};
            $bitrate = undef;
            next;
        }
    }
    if ($#bitrate_url_pairs < 0) {
        die 'No URL found in top-level Apple play-list from <' .
            $m3u_url . ">:\n" . $response->decoded_content . "\n";
    }

    return @bitrate_url_pairs;
}


# Return array of { bitrate => INTEGER, url => URL } found in Apple SMIL play
# list. Arguments is playlist as string, URL of the playlist,
# playlist as XML::XPath object, and LWP::UserAgent object.
sub extract_urls_from_apple_smil {
    my ($smil, $smil_url, $parser, $ua) = @_;

    my $videos =
        $parser->find('/data/smilRoot/body/video');
    if ($videos->size <= 0) {
        die "No videos found in SMIL playlist <" . $smil_url . ">:\n" .
            $smil . "\n";
    }
    my @bitrate_url_pairs = ();
    foreach my $video ($videos->get_nodelist) {
        my $m3u_url = $video->getAttribute('src');
        if (! defined $m3u_url) {
            print STDERR q{Missing `video/@src' attribute} . "\n";
            next;
        }
        push @bitrate_url_pairs,
            extract_urls_from_top_apple_m3u($m3u_url, $ua);
    }

    return @bitrate_url_pairs;
}


# Return array of { bitrate => INTEGER, url => URL } found in
# M3U play-list. Returned URLs are media URLs, bit-rates are dummy numbers.
# Arguments are URL of the playlist and LWP::UserAgent object.
sub extract_urls_from_m3u {
    my ($m3u_url, $ua) = @_;
    my @bitrate_url_pairs = ();

    # Get the playlist.
    my $response = $ua->request(GET $m3u_url);
    $response->is_success or
        die "Could get not M3U play-list from <" .
            $m3u_url . ">: " . $response->status_line . "\n";
    my $order = -1;
    my $separated;
    for (split(/(\r)?\n/, $response->decoded_content)) {
        if (! defined) { next; }
        if (/\A#EXTINF:/) {
            $order++;
            $separated = 1;
            next;
        }
        if (/\A[^#]/) {
            if (! defined $separated) {
                print STDERR 'Stray URL in M3U play-list from <' .
                    $m3u_url . ">:\n" . $response->decoded_content . "\n";
                next;
            }
            push @bitrate_url_pairs,
                {'bitrate' => $order, 'url' => URI->new_abs($_, $m3u_url)};
            $separated = undef;
            next;
        }
    }
    if ($#bitrate_url_pairs < 0) {
        die 'No URL found in M3U play-list from <' .
            $m3u_url . ">:\n" . $response->decoded_content . "\n";
    }

    return @bitrate_url_pairs;
}


# Retrieve a hash code from a base URL with a user agent. It dies on error.
sub download_hash_code {
    my ($ua, $base_url) = @_;
    my $hash_generator_url = URI->new_abs('/v-api/iframe-hash/', $base_url);
    my $response = $ua->request(GET $hash_generator_url);
    $response->is_success or
        die "Could not get an iframe hash from ". 
            "<$hash_generator_url>: " .  $response->status_line . "\n";
    my $hash_code = $response->decoded_content;
    chomp($hash_code);
    return $hash_code;
}


if (!$opt_A) {
    warn "DASH support is being implemented\n";
}


# Get entry HTML page
my $ua = LWP::UserAgent->new;
$ua->env_proxy();
if ($opt_A) {
    # HLS with MPEG-TS
    $ua->agent('Mozilla/5.0 (iPad; CPU OS 10_15_5 (Ergänzendes Update) like Mac OS X) '
        . 'AppleWebKit/605.1.15 (KHTML, like Gecko) ' .
        'Version/12.1.1 Mobile/15E148 Safari/605.1.15'
    );
} else {
    # ct24 portal does not support default user agent
    # FLV
    #$ua->agent('Mozilla/5.0 (X11; Linux x86_64; rv:34.0) Gecko/20100101 Firefox/34.0');
    # DASH with split AVC1 and MP4A and timing
    $ua->agent('Mozilla/5.0 (X11; Linux x86_64; rv:58.0) Gecko/20100101 Firefox/58.0');
}
if ($opt_v) {
    print STDERR "Getting <$ENTRY>\n";
}
my $response = $ua->request(GET $ENTRY);
$response->is_success or
    die "Could not get entry page from <" . $ENTRY . ">: " .
        $response->status_line . "\n";
my $page = $response->decoded_content;


my $m3u_url;
my $smil_url;
my $smil_url_is_m3u;


# Try to get an iframe player
# <https://ct24.ceskatelevize.cz/> embeds the player within an iframe whose
# URL requires a separeted hash code.
# (Handled by the next block, probably obsolete:
# <http://www.ceskatelevize.cz/art/zive/> embeds the player including the hash
# code.
# <http://www.ceskatelevize.cz/ivysilani/zive/ct1/> has the player in the main
# page directly.)
# This seems to be used by channel subdomains.
# <https://ct24.ceskatelevize.cz/domaci/3424616-nove-motoraky-ceskych-drah-nejdou-nastartovat-vyprsela-platnost-softwaru>
# embeds two iframes: the first one is invalid (a generic live streaming),
# the other one contains multimediaUrl attribute (a specific stream). Prefer
# the later one.
# The web page is not well-formed XML, we cannot use XPath 
# '//span[class="media-ivysilani-placeholder"]/@data-url' or
# '//iframe/@src'.
my $iframe_url = htmlgrep($page,
    qr{(?:data-url|src)="([^"]*/embed/iFramePlayer(?:[^"]*)\.php[^"]*multimediaUrl=[^"]*)"});
if (!defined $iframe_url) {
    $iframe_url = htmlgrep($page,
        qr{(?:data-url|src)="([^"]*/embed/iFramePlayer(?:[^"]*)\.php[^"]*)"});
}
if (defined $iframe_url) {
    $iframe_url = URI->new_abs($iframe_url, $ENTRY);
    if ($opt_v) {
        print STDERR "An iframe player URL <$iframe_url> found.\n";
    }

    # Try to append a separeted hash code
    my $hash_code = htmlgrep($page, qr{\bhash"?:"([^"]+)"});
    if (defined $hash_code and $hash_code ne '') {
        if ($opt_v) {
            print STDERR "A hash code $hash_code found.\n";
        }
        $iframe_url->query_form($iframe_url->query_form, 'hash', $hash_code);
    } else {
        if ($opt_v) {
            print STDERR "No separeted hash code found, assuming it's not needed.\n";
        }
    }
}
# Or <http://www.ceskatelevize.cz/ct24> is a JavaScript mess:
#   /ct24 contains:
#       "legacyEncoder":"CT3" in //script[id="__NEXT_DATA__"]
#   /_next/static/chunks/pages/_app-7816f4755ca2278b605d.js contains:
#       src:`/ivysilani/embed/iFramePlayer.php?${$}`
#       fetch("/v-api/iframe-hash/")
#       {videoID:T.encoder.toLocaleUpperCase(),multimedia:"1",tpl:"live",skinID:"3"}
#   /v-api/iframe-hash/ returns the hash
#   <https://www.ceskatelevize.cz/ivysilani/embed/iFramePlayer.php?hash=76b3922153381d684dc8f680e1634d9ce45df0a4&origin=iVysilani&autoStart=true&width=100%25&videoID=CT3&multimedia=1&tpl=live&skinID=3>
#       is the desired iframe player URL.
# This seems to be used for a live streaming.
if (!defined $iframe_url) {
    my $videoID = htmlgrep($page, qr{"legacyEncoder":"([^"]+)"});
    if (defined $videoID) {
        $videoID = uc($videoID);
        if ($opt_v) {
            print STDERR "A JavaScript generator with videoID $videoID " .
                "for an iframe player URL found.\n";
        }

        # Build an iframe player URL
        my $hash_code = download_hash_code($ua, $ENTRY);
        $iframe_url = URI->new_abs('/ivysilani/embed/iFramePlayer.php',$ENTRY);
        # Parse query values from /_next/static/chunks/pages/_app-*.js
        $iframe_url->query_form('hash' => $hash_code, 'origin' => 'iVysilani',
            'autoStart' => 'true', 'width' => '100%', 'videoID' => $videoID,
            'multimedia' => 1, 'tpl' => 'live', 'skinID' => 3);
    }
}
# Or
# <https://www.ceskatelevize.cz/porady/1126672097-otazky-vaclava-moravce/221411030511128/>:
#   contains:
#       "idec":"221411030511128" in //script[id="__NEXT_DATA__"]
#   /_next/static/chunks/pages/_app-7816f4755ca2278b605d.js contains:
#       {IDEC:T.idec,start:`${V}`}
#   <https://www.ceskatelevize.cz/ivysilani/embed/iFramePlayer.php?hash=4226c22cd955831bdd74f5472717dbdb53201e76&origin=iVysilani&autoStart=true&width=100%25&IDEC=221411030511128&start=0>
#       is the desired iframe player URL.
# But a series page
# <https://www.ceskatelevize.cz/porady/1126672097-otazky-vaclava-moravce/> has
# first idec invalid. One needs to prefer playableIdec field.
# This seems to be used for a video on demand.
if (!defined $iframe_url) {
    my $IDEC = htmlgrep($page, qr{"playableIdec":"([^"]+)"});
    if (!defined $IDEC) {
        $IDEC = htmlgrep($page, qr{"idec":"([^"]+)"});
    }
    if (defined $IDEC) {
        if ($opt_v) {
            print STDERR "A JavaScript generator with IDEC $IDEC " .
                "for an iframe player URL found.\n";
        }

        # Build an iframe player URL
        my $hash_code = download_hash_code($ua, $ENTRY);
        chomp($hash_code);
        $iframe_url = URI->new_abs('/ivysilani/embed/iFramePlayer.php',$ENTRY);
        # Parse query values from /_next/static/chunks/pages/_app-*.js
        $iframe_url->query_form('hash' => $hash_code, 'origin' => 'iVysilani',
            'autoStart' => 'true', 'width' => '100%', 'IDEC' => $IDEC,
            'start' => 0);
    }
}

# Get an iframe player page if the player was found
if (defined $iframe_url) {
    if ($opt_v) {
        print STDERR "Getting iframe <$iframe_url>\n";
    }
    $response = $ua->request(GET $iframe_url);
    $response->is_success or
        die "Could not get iframe player from <" . $iframe_url . ">: " .
            $response->status_line . "\n";
    $page = $response->decoded_content;
} else {
    $iframe_url = $ENTRY;
    if ($opt_v) {
        print STDERR "No iframe player found, assuming an in-line player.\n";
    }
}


# Get AJAX request data
my $ajax_data = findjson($page, 'getPlaylistUrl');
unless (defined $ajax_data && $ajax_data) {
    # Overloaded server returns SMIL URL directly. Check it here before
    # printing error message.
    $smil_url = htmlgrep($page,
        qr{(?<!//)(?:\s*)\bflashvars.playlistURL\s*=\s*'([^']+)'});
    if (defined $smil_url) {
        if ($opt_v) {
            print STDERR "Server provides direct URL to the SMIL playlist.\n";
        }
        goto HAVE_SMIL_URL;
    }
}
unless (defined $ajax_data && $ajax_data) {
    # Try to get error message from stream provider
    my $message = htmlgrep($page,
        qr{<div\s+class="error-message">(?:\s*<[^/>]*>)*(.*?)(?:</)}
    );
    if (defined $message) {
        $message =~ s{<br\s*/>}{\n}g;
        if ($message) {
            die "$message\n";
        }
    }

    # else die in general way
    if ($opt_v) {
        print STDERR "===BEGIN INPUT===\n$page\n===END INPUT===\n";
    }
    die "Could not find AJAX data structure\n";
}
# The JSON structure is the first argument of getPlaylistUrl() which has
# variadic number of arguments.
$ajax_data =~ s/(?<=[{\]])(,[^,]*)*\z//; 


# Build 'data' AJAX structure from AJAX script and iframe sources.
# 'requestSource' and 'type' elements are constants defined in the iframe.
# 'streamQuality' element is parsed from $ENTRY URL query segment, but it is
# not used now. Moreover it can be undefined and then jQuery will not
# transport the key with undefined value.
# 'addCommercials' element is defined only sometimes in the iframe source and
# not needed now.
# XXX: Server checks for unexpected keys or values and bails out with 500. Do
# not send undefined streamQuality or addCommercials.
my $requestUrl = URI->new($iframe_url)->path;
my $json_data = qq(
    {
        "playlist" : $ajax_data,
        "requestUrl" : "$requestUrl",
        "requestSource" : "iVysilani",
        "type" : "html"
    }
);
#"type" : "flash"


# Get XML-RPC header definition
my ($xmlrpc_header, $xmlrpc_value) = findrequestheader($page);
if (!defined $xmlrpc_header or !defined $xmlrpc_value) {
    if ($opt_v) {
        print STDERR "===BEGIN INPUT===\n$page\n===END INPUT===\n";
    }
    print STDERR "XML-RPC header definition not found.\n";
} elsif ($opt_v) {
    print STDERR "XML-RPC header found: <$xmlrpc_header>\n";
    print STDERR "XML-RPC value found: <$xmlrpc_value>\n";
}


# Decode JSON request data
my $data;
eval { $data = decode_json($json_data) } or 
    die "Could not decode JSON string: $json_data: $@\n";
my @data = flatten($data);


# Get callSOAP source URL
my $script_url = htmlgrep($page,
    qr{
        <script
        \s+
        (?:[^>]*?)
        \s+
        src="
            (
                [^"]*
                \Qajax-playlist-o2v2.js\E
                [^"]*
            )
        "
    }x);
unless (defined $script_url && $script_url) {
    if ($opt_v) {
        print STDERR "===BEGIN INPUT===\n$page\n===END INPUT===\n";
    }
    die "Could not find link to AJAX script\n";
}


# Get callSOAP source 
if ($opt_v) {
    print STDERR "Getting AJAX script source <$script_url>\n";
}
$response = $ua->request(GET $script_url);
$response->is_success or
    die "Could not get AJAX script source from <" . $script_url . ">: "
        . $response->status_line . "\n";
my $script = $response->decoded_content;


# Get playlist URL generator in the AJAX source
# 'url' element of ajax() method argument delivered relative URL of SMIL URL
# generator. Now it's computed but the result is still a constant string
# because of constant 'baseUrl' and 'wwwServerGet' JS variables. This
# expression parses:
#   A : B + 'C',
#   A : B + 'C' + (D ? 'E' : 'F'),
#   A : B + 'C' + D,
if ($script !~ qr{
            ^\s*url\s*:
            \s*baseUrl\s*\+
            \s*'([^']+)'
            (?:
                \s*\+
                (?:
                    \s*\([^?]*\?
                        \s*'([^']+)'\s*:
                        \s*'([^']+)'\s*
                    \)
                    |
                    \s*\w+
                )
            )?
            \s*,
        }smx) {
    if ($opt_v) {
        print STDERR "===BEGIN INPUT===\n$script\n===END INPUT===\n";
    }
    die "Could not find playlist generator URL in the callSOAP function\n";
}
my $generator_path = '/ivysilani' . $1 . ($2//'');
# FIXME: Parse 'data' JSON in the $script.


# Get playlist URL
my $generator_url = URI->new_abs($generator_path, $iframe_url);
$ua->default_header($xmlrpc_header => $xmlrpc_value) if defined $xmlrpc_header;
if ($opt_v) {
    print STDERR "Posting to playlist URL generator <$generator_url>\n";
    print STDERR "Posting data to playlist URL generator: ", join(',', @data), "\n";
}
$response = $ua->request(POST $generator_url, \@data);
if ($response->code == 301 || $response->code == 302) {
    # Non-HTTPS POST requests receive 301 (used to be 302) redirecting to an
    # HTTPS location and a new POST request is expected. This violates
    # RFC 2616 and libwww-perl-6.27 does not support RFC 7231 yet
    # <https://github.com/libwww-perl/libwww-perl/issues/42>.
    my $new_url = $response->header('Location');
    if (!defined $new_url) {
        die "Playlist URL generator <$generator_url> redirects " .
            "but does not specify a new location\n";
    }
    $generator_url = $new_url;
    if ($opt_v) {
        print STDERR "Playlist URL generator redirected to <$generator_url>\n";
    }
    $response = $ua->request(POST $generator_url, \@data);
}
$response->is_success or
    die "Could not get playlist URL from playlist URL generator <" .
        $generator_url . ">: " . $response->status_line . "\n" .
        "===BEGIN OUTPUT===\n" . $response->decoded_content .
        "\n===END OUTPUT===\n";
my $playlist_url_data = $response->decoded_content;
if ($opt_v) {
    print STDERR "Playlist URL generator returned: <$playlist_url_data>\n";
}


my $smil_url_json;
eval { $smil_url_json = decode_json($playlist_url_data) } or 
    die "Could not decode JSON string with playlist URL: $playlist_url_data: $@\n";
$smil_url = $$smil_url_json{url};
if (!defined $smil_url) {
    die "Could not find URL in JSON response from playlist URL generator: " .
        $playlist_url_data . "\n";
}

# Another layer before M3U playlist URL:
$response = $ua->request(GET $smil_url);
$response->is_success or
    die "Could not get <"
        . $smil_url . ">: "
        . $response->status_line . "\n";
my $m3u_url_data = $response->decoded_content;
if ($opt_v) {
    print STDERR "Another layer before M3U URL returned:\n",
        "===BEGIN OUTPUT===\n", $m3u_url_data, "\n===END OUTPUT===\n";
}
my $m3u_url_json;
eval { $m3u_url_json = decode_json($m3u_url_data) } or 
    die "Could not decode JSON string with M3U URL: $m3u_url_data: $@\n";


# Video can have multiple parts
my $PART = 0;
if ($opt_t) {
    # Listing parts requested
    if (defined $ARGV[0]) {
        $PART = shift @ARGV;
        print $$m3u_url_json{playlist}[$PART]->{streamUrls}{main} . "\n";
    } else {
        my $id = 0;
        for (@{$$m3u_url_json{playlist}}) {
            print $id . ": " . $_->{streamUrls}{main} . "\n";
            $id++;
        }
    }
    exit;
} else {
    # If this is not the only part and user did not select it, die.
    if (@{$$m3u_url_json{playlist}} > 1) {
        if (defined $ARGV[0]) {
            $PART = shift @ARGV;
        } else {
            warn "Video has multiple parts:\n";
            my $id = 0;
            for (@{$$m3u_url_json{playlist}}) {
                print $id . ": " . $_->{streamUrls}{main} . "\n";
                $id++;
            }
            die "Select one by adding a positional argument.\n";
        }
    }
}


$m3u_url = $$m3u_url_json{playlist}->[$PART]{streamUrls}{main};
if (!defined $m3u_url) {
    die "Could not find M3U URL in JSON response from M3U URL generator: " .
        $playlist_url_data . "\n";
}


HAVE_SMIL_URL: # Overloaded server returns the SMIL URL directly.
# Rewrite SMIL playlist URL for next-stage generator
# http://code.google.com/p/dmd-xbmc/issues/detail?id=94
$smil_url = URI::Escape::uri_unescape($smil_url);


my $smil;
# The iPad requires a special suffix '&rd=1' to an URL hard-coded into the
# HTML frame. However it's easier to edit the URL here to utilize unified code
# path.
# There is a new step with Apple playlist. A short-cut to M3U exists by
# appending '&rd=1' to the generator URL. But we do not use the short-cut now.
# 
if (!defined $m3u_url) {
    $response = $ua->request(GET $smil_url);
    $response->is_success or
        die "Could not get playlist URL from second-step URL generator <"
            . $smil_url . ">: "
            . $response->status_line . "\n";
    $m3u_url = $response->decoded_content;
    if ($opt_v) {
        print STDERR "Second-step URL generator returned:\n",
            "===BEGIN OUTPUT===\n", $m3u_url, "\n===END OUTPUT===\n";
    }

    if ($m3u_url =~ /<smilRoot>/) {
        $smil = $m3u_url;
        # This is sometimes SMIL play-list with only one video URL
        # which points to Apple M3U top play-list.
        my $parser = XML::XPath->new('xml' => $smil) or
            die "Could not parse SMIL playlist from <" .
                $smil_url . ">:\n" . $smil . "\n";
        # XXX: XML::XPath is lazy in parsing. It dies when calling find() on
        # XML syntax error. 
        eval {
            $m3u_url = extract_url_from_m3u_smil($smil, $smil_url, $parser);
        };
        if ($@) {
            print STDERR "Error while finding stream URLs " .
                "in SMIL playlist from <", $smil_url, ">.\n";
            print STDERR "===BEGIN INPUT===\n$smil\n===END INPUT===\n";
            die "Reason: $@\n";
        }

    } else {
        # Or the second-step generator returns two concatened URLs in plain
        # text file.
        $m3u_url =~ s|(.)http://.*|$1|;
    }
}


# Get stream URLs
my @bitrate_url_pairs = extract_urls_from_top_apple_m3u($m3u_url, $ua);

my $BITRATE = shift @ARGV;
if ($opt_f || $opt_s) {
    # Select Apple M3U URL
    if (defined $BITRATE) {
        @bitrate_url_pairs = grep { ${$_}{'bitrate'} == $BITRATE }
            @bitrate_url_pairs;
    }
    if ($#bitrate_url_pairs < 0) {
        die "No usable video streams found in top-level Apple playlist:\n$m3u_url\n";
    }
    if ($#bitrate_url_pairs == 0 ) {
        iterate_bottom_apple_m3u(${$bitrate_url_pairs[0]}{'url'}, $ua, $opt_s);
    } else {
        die "Multiple bit-rate play-lists not implemented yet.\n";
    }
} else {
    # Output URL
    my $video_counter = 0;
    for my $pair (@bitrate_url_pairs) {
        if (defined $BITRATE) {
            if (${$pair}{'bitrate'} == $BITRATE) {
                print "${$pair}{'url'}\n";
                $video_counter++;
            }
        } else {
            print "${$pair}{'bitrate'}: ${$pair}{'url'}\n";
            $video_counter++;
        }
    }
    if ($video_counter <= 0) {
        die "No usable video streams found in playlist:\n$smil\n";
    }
}