#!/usr/bin/perl

# The first argument ($ARGV[0]) is the name of the player ratings file.
#   Format is one player record per line: username rating maxGames
# If any second argument is provided then additional info is
#   displayed.

#######################################
# Read in the input and create an array of records

open(FH, "<$ARGV[0]");
@f = <FH>;
close FH;

foreach $f (@f){
  chomp $f;
  my($p);
  ($u, $r, $m) = split(/ +/, $f);
  if ($m eq ''){ $m = 2; }
  if ($r eq ''){ next; }
  $p->{u} = $u;
  $p->{r} = $r;
  $p->{m} = $m;
  push(@r, $p);
}

#######################################
# Sort the records by rating from highest rated to lowest
#   9 8 7 6 5 4 3 2 1
@f = sort {$b->{r} <=> $a->{r}} @r;

#######################################
# Now re-order so there is no sharp difference in rating between
#   the first and last as well as any other adjacent elements
#   basically a smooth ring
#   9 7 5 3 1 2 4 6 8
$d = 1;
$i = 0;
$k = 0;
foreach $f (@f){
  $r[$i] = $f;
  if ($d == 1){
    $d = -1;
    $i = $#f - $k;
  }
  else{
    $d = 1;
    $k += 1;
    $i = $k;
  }
}


#######################################
# Show the ordering of the players if second arg given
if ($ARGV[1]){
  print "\n";
  foreach $p (@r){
    print "$p->{u} $p->{r} $p->{m}\n";
  }
}


#######################################
# Pick games between unique pairs of players
#   Go through each player in the array and if the player still
#     needs more games try to find an opponent that is as close as
#     possible and also needs more games and has not already been
#     paired against.
#   Reverse the array repeat the attempt to find pairs.
#   If no pairs were found for any players then stop.

@r = reverse(@r);
$anyMatch = 1;
while($anyMatch){
  @r = reverse(@r);
  $anyMatch = 0;
  $i = -1;
  $g += 2;
  foreach $p (@r){
    $i += 1;
    if (($p->{g} >= $g) || ($p->{g} >= $p->{m})){ next; }
  
#    for($j=$i+1; $j<=$#r; $j++){
    for($j=$i+1; $j!=$i; $j=($j>=$#r)?0:($j+1)){
      my($gr);
      $o = $r[$j];
      if (($o->{g} >= $g) || ($o->{g} >= $o->{m})){ next; }
      if ($p->{u} lt $o->{u}){
        $p1 = $p; $p2 = $o;
      }
      else{
        $p2 = $p; $p1 = $o;
      }
      if ($m{"$p1->{u} $p2->{u}"}){ next; }
      $m{"$p1->{u} $p2->{u}"} = 1;
      if ($goldr{$p1->{u}} > $goldr{$p2->{u}}){
#print "$p2->{u} $p1->{u}\n";
        $gr->{p2} = $p1->{u}; $gr->{r2} = $p1->{r};
        $gr->{p1} = $p2->{u}; $gr->{r1} = $p2->{r};
        push(@ga, $gr);
        $gold{$p2->{u}} += 1;
        $g{"$p1->{u} $p2->{u}"} = 2;
      }
      else{
#print "$p1->{u} $p2->{u}\n";
        $gr->{p1} = $p1->{u}; $gr->{r1} = $p1->{r};
        $gr->{p2} = $p2->{u}; $gr->{r2} = $p2->{r};
        push(@ga, $gr);
        $gold{$p1->{u}} += 1;
        $g{"$p1->{u} $p2->{u}"} = 1;
      }
      $games{$p1->{u}} += 1;
      $games{$p2->{u}} += 1;
      $goldr{$p1->{u}} = $gold{$p1->{u}}/$games{$p1->{u}};
      $goldr{$p2->{u}} = $gold{$p2->{u}}/$games{$p2->{u}};
  
      $p->{g} += 1;
      $o->{g} += 1;
      $anyMatch = 1;
      last;
    }
  }
}


#######################################
# Make another pass to find a second games between players
#   who still want more games.

$anyMatch = 1;
$g -= 2;
while($anyMatch){
  @r = reverse(@r);
  $anyMatch = 0;
  $i = -1;
  $g += 2;
  foreach $p (@r){
    $i += 1;
    if (($p->{g} >= $g) || ($p->{g} >= $p->{m})){ next; }
  
#    for($j=$i+1; $j<=$#r; $j++){
    for($j=$i+1; $j!=$i; $j=($j>=$#r)?0:($j+1)){
      my($gr);
      $o = $r[$j];
      if (($o->{g} >= $g) || ($o->{g} >= $o->{m})){ next; }
      if ($p->{u} lt $o->{u}){
        $p1 = $p; $p2 = $o;
      }
      else{
        $p2 = $p; $p1 = $o;
      }
      if ($sm{"$p1->{u} $p2->{u}"}){ next; }
      $m{"$p1->{u} $p2->{u}"} = 1;
      $sm{"$p1->{u} $p2->{u}"} = 1;
      if ($g{"$p1->{u} $p2->{u}"} == 1){
#print "$p2->{u} $p1->{u}\n";
        $gr->{p2} = $p1->{u}; $gr->{r2} = $p1->{r};
        $gr->{p1} = $p2->{u}; $gr->{r1} = $p2->{r};
        push(@ga, $gr);
      }
      else{
#print "$p1->{u} $p2->{u}\n";
        $gr->{p1} = $p1->{u}; $gr->{r1} = $p1->{r};
        $gr->{p2} = $p2->{u}; $gr->{r2} = $p2->{r};
        push(@ga, $gr);
      }
      $p->{g} += 1;
      $o->{g} += 1;
      $anyMatch = 1;
      last;
    }
  }
}

#######################################
# if a second arg was given the show how many games the
# players wanted and how many games they got.
if ($ARGV[1]){
  print "\n";
  print "player rating games_wanted games_paired\n";
  foreach $p (@r){
    print "$p->{u} $p->{r} $p->{m} $p->{g}\n";
  }
}

#######################################
# print out the pairing for all the games we have found
#   also compute a score for this pairing
print "\n";
foreach $g (@ga){
  print "[$g->{p1} $g->{r1} vs $g->{p2} $g->{r2}]\n";
  $sc += abs($g->{r1} - $g->{r2});
  $ng += 1;
}
$sca = $sc/$ng;

if ($ARGV[1]){
  print "\n";
  print "numGames: $ng   matchDiff: $sca\n";
}


exit;