use strict;

use IO::File;
use Time::Piece;

main();

sub main {
  unless (@ARGV) {
    die "No argments : specify file name of log.";
  }
  
  my $filename = $ARGV[0];
  
  my $fp = IO::File->new($filename, 'r')
    or die "Failed to open log file : [$filename]";

# read a line.
#  print_line($fp);

# print number of lines;
#  print count_lines($fp);

# print IP address of first line.
#  my $line = $fp->getline;
#  print extract_ip_address($line);

#  print_ip_count($fp);

# print time stamp
#  my $line = $fp->getline;
#  print extract_time_stamp($line);

# print date count
  print_day_count($fp);


  $fp->close;
}

# print a line of file;
sub print_line {
  my ($fp) = @_;
# or my $fp = shift;
# or my $fp = $_[0];

  print $fp->getline;
}

# count lines
sub count_lines {
  my ($fp) = @_;
  
  my $count = 0;
  
  my $line;
  while ($line = $fp->getline) {
    $count++
  }
  
  $count;
}

# extract IP address from log line.
sub extract_ip_address {
  my ($line) = @_;
  
  my ($ip_address) = $line =~ m/^(\d+\.\d+\.\d+\.\d+)/;
  
  $ip_address;
}

# print number of lines each with IP addresses.
sub print_ip_count {
  my ($fp) = @_;
  
  my %ip_count;
  
  while (my $line = $fp->getline) {
    my $ip_address = extract_ip_address($line);
    next unless $ip_address;
    
    $ip_count{$ip_address}++;
  }
  
  # print each records.
  my @sorted_keys = sort { $ip_count{$b} <=> $ip_count{$a} } keys %ip_count;
  for my $key (@sorted_keys) {
    #print "$key      $ip_count{$key}\n";
    printf("%15s %10d\n", $key, $ip_count{$key});
  }

#  for my $key (keys %ip_count) {
#    #print "$key      $ip_count{$key}\n";
#    printf("%15s %10d\n", $key, $ip_count{$key});
#  }

  # total number of ip addresses.
  my $number_of_ip = keys %ip_count;

  print "number of IP addresses: $number_of_ip";
}

# print access count of each days.
sub print_day_count {
  my ($fp) = @_;
  
  my %day_count;

  while (my $line = $fp->getline) {
    my $timestamp = extract_time_stamp($line);
    next unless $timestamp;

    my $ts_str = $timestamp->strftime("%y/%m/%d");
    $day_count{$ts_str}++;
  }
  
  # print each records.
  my @sorted_keys = sort(keys %day_count);
  for my $key (@sorted_keys) {
    #print "$key      $ip_count{$key}\n";
    printf("%15s %10d\n", $key, $day_count{$key});
  }

}

# extract time stamp
sub extract_time_stamp {
  my ($line) = @_;
  
  my ($timestamp) = $line =~ m/\[(.+?)\]/;
  
  unless ($timestamp) {
    return undef;
  }
  # parse timestamp such as '09/Mar/2004:22:04:29 -0500'
  Time::Piece->strptime($timestamp, "%d/%b/%Y:%H:%M:%S %z");
}