use IO::Socket::INET;
use Data::Dumper;

use strict;
use warnings;

$| ++;

#@done is populated, but not really used in this version
#in the future, might retry failed ones base on done.
my (@page, @done);

open(PAGES, "<", "pages.txt");
while (<PAGES>) {
    chomp;
    my @data = split / /;
    if ($#data == 2) {
        for my $index ($data[1]..$data[2]) {
            push @page, sprintf($data[0], $index);
            push @done, 0;
        }
    } elsif ($#data == 0) {
        push @page, $data[0];
        push @done, 0;
    }
}
close(PAGES);

download(\@page, \@done);

sub download {
    my ($page, $done) = @_;
    for my $index (0..$#{@$page}) {
        $done[$index] = download_one_file($page[$index]);
    }
}

sub download_one_file {
    my ($page) = @_;
    my $host = get_host($page);
    my $file = get_file($page);

    my $percentage;
    my $header = {};
    my $return_code;
    
    print "Trying $host... ";
    my $connection = IO::Socket::INET->new(PeerAddr => $host,
                    PeerPort => 80,
                    Timeout => 30);
    if ($connection) {
        print "connected, download <$file>\n";
        binmode($connection);
        my $req = "GET $page HTTP/1.0\r\nHost: $host\r\n\r\n";
        print $connection $req;

        my $res;
        if (open(FILE, ">", $file)) {
            binmode(FILE);
            my $bytes_read = 0;
            while (1) {
                my $chunk;
                sysread($connection, $chunk, 4096);
                #stopped, just fail it
                if (!length($chunk)) {
                    print " Connection dropped";
                    $return_code = 0;
                    last;
                }
                if (!exists($header->{"status_code"})) {
                    $res .= $chunk;
                    if (got_header($res)) {
                        $res =~ m/(.*?)\r\n\r\n(.*)/s;
                        if ($2) {
                            syswrite(FILE, $2);
                            $bytes_read += length($2);
                        }
                        parse_header($1, $header);
                        if ($header->{"status_code"} eq '200') {
                            $percentage = get_percentage($header->{"Co
+ntent-Length"}, $bytes_read);
                            print "Content Length = " . $header->{"Con
+tent-Length"} . ", Received = $percentage";
                        } else {
                            print "Status Code = " . $header->{"status
+_code"};
                            $return_code = 1;
                            last;
                        }
                    }
                } else {
                    syswrite(FILE, $chunk); 
                    $bytes_read += length($chunk);
                    my $old_percentage = $percentage;
                    $percentage = get_percentage($header->{"Content-Le
+ngth"}, $bytes_read);
                    if ($percentage != $old_percentage) {
                        print $percentage;
                    }
                }
                if ($header->{"Content Length"} && ($header->{"Content
+-Length"} <= $bytes_read)) {
                    print "Read up to content length\n";
                    $return_code = 1;
                    last;
                }
                if ($res =~ m/\/html/) {
                    print "reached /html tag\n";
                    $return_code = 1;
                    last;
                }
            }
            close(FILE);
            print "\n";
        } else {
            $return_code = 0;
            print "failed to open local file\n";
        }
    } else {
        $return_code = 0;
        print "failed, skip $file\n";
    }
    return $return_code;
}

sub get_host {
    my ($page) = @_;
    $page =~ m/\/\/(.*?)\//;
    return $1;
}

sub get_file {
    my ($page) = @_;
    return (split /\//, $page)[-1];
}

sub get_percentage {
    my ($total, $rcvd) = @_;
    return int(($rcvd / $total) * 10);
}

sub got_header {
    my $res = shift;
    if ($res =~ m/\r\n\r\n/s) {
        return 1;
    } else {
        return 0;
    }
}

sub parse_header {
    my ($res, $header) = @_;
    my @lines = split(/\r\n/, $res);
    $header->{"status_code"} = (split(/ /, $lines[0]))[1];
    for my $index (1 .. $#lines) {
        my ($key, $value) = split(/: /, $lines[$index]);
        $header->{$key} = $value;
    }
}
[download]