package Geo::Mirror;

use strict;
use vars qw($VERSION);

$VERSION = '1.0';

use constant PI => 3.14159265358979323846;

our (%lat, %lon, $geo_ip_pkg);

BEGIN {
  if (eval { require Geo::IP }) {
    $geo_ip_pkg = "Geo::IP";
  }
  else {
    require Geo::IP::PurePerl;
    $geo_ip_pkg = "Geo::IP::PurePerl";
  }
  $geo_ip_pkg->import('GEOIP_STANDARD');
}

while (<DATA>) {
  my ($country, $lat, $lon) = split(':');

  $lat{$country} = $lat;
  $lon{$country} = $lon;
}

sub new {
  my ($class, %h) = @_;
  my $self = \%h;
  bless $self, $class;
  $self->_init;
  return $self;
}

sub _init {
  my $self = shift;
  my $mirror_file = $self->{mirror_file};
  open MIRROR, "$mirror_file";
  while(<MIRROR>) {
    my ($url, $country, $fresh) = split(' ');
    push @{$self->{mirror}->{$country}}, $url;
    $self->{fresh}{$url} = $fresh || 0;
  }
  close MIRROR;
}

sub _random_mirror {
  my ($self, $country, $fresh) = @_;

  my @mirror = grep { $self->{fresh}{$_} >= $fresh } @{$self->{mirror}->{$country}};

  my $num = scalar @mirror or return;

  return $mirror[ rand($num) ];
}

sub find_mirror_by_country {
  my ($self, $country, $fresh) = @_;
  my $url;

  $fresh ||= 0;

  if (exists $self->{mirror}->{$country}) {
    $url = $self->_random_mirror($country, $fresh);
  }

  if (!$url) {
    my $nearby = $self->{nearby_cache}->{$country} ||= $self->_find_nearby_countries($country);
    foreach my $new_country (@$nearby) {
      $url = $self->_random_mirror($new_country, $fresh) and last;
    }
  }

  return $url;
}

sub find_mirror_by_addr {
  my ($self, $addr, $fresh) = @_;

  unless($self->{gi}) {
    if ($self->{database_file}) {
      $self->{gi} = $geo_ip_pkg->open($self->{database_file}, GEOIP_STANDARD);
    } else {
      $self->{gi} = $geo_ip_pkg->new(GEOIP_STANDARD);
    }
  }

  # default to US if country not found
  my $country = lc($self->{gi}->country_code_by_addr($addr)) || 'us';
  $country = 'us' if $country eq '--';
  return $self->find_mirror_by_country($country, $fresh);
}

sub _find_nearby_countries {
  my ($self, $country) = @_;

  my %distance = map { ($_, $self->_calculate_distance($country, $_)) } keys %{$self->{mirror}};
  delete $distance{$country};

  [ sort { $distance{$a} <=> $distance{$b} } keys %distance ];
}

sub _calculate_distance {
  my ($self, $country1, $country2) = @_;

  my $lat_1 = $lat{$country1};
  my $lat_2 = $lat{$country2};
  my $lon_1 = $lon{$country1};
  my $lon_2 = $lon{$country2};

  # Convert all the degrees to radians
  $lat_1 *= PI/180;
  $lon_1 *= PI/180;
  $lat_2 *= PI/180;
  $lon_2 *= PI/180;

  # Find the deltas
  my $delta_lat = $lat_2 - $lat_1;
  my $delta_lon = $lon_2 - $lon_1;

  # Find the Great Circle distance
  my $temp = sin($delta_lat/2.0)**2 + cos($lat_1) * cos($lat_2) * sin($delta_lon/2.0)**2;
  return atan2(sqrt($temp),sqrt(1-$temp));
}

1;

=head1 NAME

Geo::Mirror - Find closest Mirror

=head1 SYNOPSIS

  use Geo::Mirror;

  my $gm = Geo::Mirror->new(mirror_file => '/path/to/mirrors.txt');

  my $mirror = $gm->closest_mirror_by_country('us', $freshness);       # $freshness optional, see description below
  my $mirror = $gm->closest_mirror_by_addr('24.24.24.24', $freshness); # $freshness optional, see description below

=head1 DESCRIPTION

This module finds the closest mirror for an IP address.  It uses L<Geo::IP>
to identify the country that the IP address originated from.  If
the country is not represented in the mirror list, then it finds the
closest country using a latitude/longitude table.

The mirror file should be a space separate list of URL, Country, and mirror freshness.
The mirror freshness is optional and can be used by user
request a mirror with a minimum freshness.

=head1 AUTHOR

Copyright (c) 2004, MaxMind LLC, support@maxmind.com

All rights reserved.  This package is free software; you can redistribute it
and/or modify it under the same terms as Perl itself.

=cut

__DATA__
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