package include::pqueue;

use strict;
use warnings;
use include;

# Returns a new priority queue object.
sub queueify {
  return bless [], shift;
}

# Takes a hashref with a priority value ("P") and whatever other data you want
# to store. Adds it to the right place in the queue.
sub add {
  my ($self, $node) = @_;
  push @$self, $node;
  my $i = $#{ $self };
  # Sort by P, putting the lowest values at the beginning of the queue.
  # TODO: make me efficent!
  while ($i != 0) {
    # Can we swap node number $i with the node before it?
    # TODO: the 'bubble' option? <=? newest nodes first?
    if ($self->[$i]{P} < $self->[$i - 1]{P}) {
      ($self->[$i]{P}, $self->[$i - 1]{P})
        =
      ($self->[$i - 1]{P}, $self->[$i]{P});
      $i--;
    } else {
      last;
    }
  }
  return 1;
}

# Nukes and returns the node with the lowest P value.
sub lowest {
  my $self = shift;
  return undef unless @$self;
  return shift @$self;
}

# Nukes and returns the node with the highest P value.
sub highest {
  my $self = shift;
  return undef unless @$self;
  return pop @$self;
}

42;