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#pod
#pod This is the I<entire> mechanism.  This is quick and dirty and quite effective,
#pod but it's not highly efficient.  If you need high speed locks with multiple
#pod levels of resolution, or anything other than a quick and brutal solution,
#pod I<keep looking>.
#pod
#pod =head1 STORAGE
#pod
#pod To use this module you'll need to create the lock table, which should have five
#pod columns:
#pod
#pod =over
#pod
#pod =item * C<id> Autoincrementing ID is recommended
#pod
#pod =item * C<lockstring> varchar(128) with a unique constraint
#pod
#pod =item * C<created> datetime
#pod
#pod =item * C<expires> datetime
#pod
#pod =item * C<locked_by> text
#pod
#pod =back
#pod
#pod See the C<sql> directory included in this dist for DDL for your database.
#pod
#pod =method new
#pod
#pod   my $locker = DBIx::Locker->new(\%arg);
#pod
#pod This returns a new locker.
#pod
#pod Valid arguments are:
#pod
#pod   dbh      - a database handle to use for locking
#pod   dbi_args - an arrayref of args to pass to DBI->connect to reconnect to db
#pod   table    - the table for locks
#pod
#pod =cut

sub new {
  my ($class, $arg) = @_;

  my $guts = {
    dbh      => $arg->{dbh},
    dbi_args => ($arg->{dbi_args} || $class->default_dbi_args),
    table    => ($arg->{table}    || $class->default_table),
  };

  Carp::confess("cannot use a dbh without RaiseError")
    if $guts->{dbh} and not $guts->{dbh}{RaiseError};

  my $dbi_attr = $guts->{dbi_args}[3] ||= {};

  Carp::confess("RaiseError cannot be disabled")
    if exists $dbi_attr->{RaiseError} and not $dbi_attr->{RaiseError};

  $dbi_attr->{RaiseError} = 1;

  return bless $guts => $class;
}

#pod =method default_dbi_args
#pod
#pod =method default_table
#pod
#pod These methods may be defined in subclasses to provide defaults to be used when
#pod constructing a new locker.
#pod
#pod =cut

sub default_dbi_args {
  Carp::confess('dbi_args not given and no default defined')
}

sub default_table    {
  Carp::Confess('table not given and no default defined')
}

#pod =method dbh
#pod
#pod This method returns the locker's dbh.
#pod
#pod =cut

sub dbh {
  my ($self) = @_;
  return $self->{dbh} if $self->{dbh} and eval { $self->{dbh}->ping };

  die("couldn't connect to database: $DBI::errstr")
    unless my $dbh = DBI->connect(@{ $self->{dbi_args} });

  return $self->{dbh} = $dbh;
}

#pod =method table
#pod
#pod This method returns the name of the table in the database in which locks are
#pod stored.
#pod
#pod =cut

sub table {
  return $_[0]->{table}
}

#pod =method lock
#pod
#pod   my $lock = $locker->lock($lockstring, \%arg);
#pod
#pod This method attempts to return a new DBIx::Locker::Lock.
#pod
#pod =cut

my $JSON;
BEGIN { $JSON = JSON->new->canonical(1)->space_after(1); }

sub lock {
  my ($self, $lockstring, $arg) = @_;
  $arg ||= {};