package DBIx::Class::Storage::Statistics;
use strict;
use warnings;

use base qw/DBIx::Class/;
use IO::File;
use namespace::clean;

__PACKAGE__->mk_group_accessors(simple => qw/callback _debugfh silence/);

=head1 NAME

DBIx::Class::Storage::Statistics - SQL Statistics

=head1 SYNOPSIS

=head1 DESCRIPTION

This class is called by DBIx::Class::Storage::DBI as a means of collecting
statistics on its actions.  Using this class alone merely prints the SQL
executed, the fact that it completes and begin/end notification for
transactions.

To really use this class you should subclass it and create your own method
for collecting the statistics as discussed in L<DBIx::Class::Manual::Cookbook>.

=head1 METHODS

=cut

=head2 new

Returns a new L<DBIx::Class::Storage::Statistics> object.

=cut
sub new {
  my $self = {};
  bless $self, (ref($_[0]) || $_[0]);

  return $self;
}

=head2 debugfh

Sets or retrieves the filehandle used for trace/debug output.  This should
be an IO::Handle compatible object (only the C<print> method is used). Initially
should be set to STDERR - although see information on the
L<DBIC_TRACE> environment variable.

As getter it will lazily open a filehandle for you if one is not already set.

=cut

sub debugfh {
  my $self = shift;

  if (@_) {
    $self->_debugfh($_[0]);
  } elsif (!defined($self->_debugfh())) {
    my $fh;
    my $debug_env = $ENV{DBIX_CLASS_STORAGE_DBI_DEBUG}
                  || $ENV{DBIC_TRACE};
    if (defined($debug_env) && ($debug_env =~ /=(.+)$/)) {
      $fh = IO::File->new($1, 'a')
        or die("Cannot open trace file $1");
    } else {
      $fh = IO::File->new('>&STDERR')
        or die('Duplication of STDERR for debug output failed (perhaps your STDERR is closed?)');
    }

    $fh->autoflush();
    $self->_debugfh($fh);
  }

  $self->_debugfh;
}

=head2 print

Prints the specified string to our debugging filehandle.  Provided to save our
methods the worry of how to display the message.

=cut
sub print {
  my ($self, $msg) = @_;

  return if $self->silence;

  $self->debugfh->print($msg);
}

=head2 silence

Turn off all output if set to true.

=head2 txn_begin

Called when a transaction begins.

=cut
sub txn_begin {
  my $self = shift;

  return if $self->callback;

  $self->print("BEGIN WORK\n");
}

=head2 txn_rollback

Called when a transaction is rolled back.

=cut
sub txn_rollback {
  my $self = shift;

  return if $self->callback;

  $self->print("ROLLBACK\n");
}

=head2 txn_commit

Called when a transaction is committed.

=cut
sub txn_commit {
  my $self = shift;

  return if $self->callback;

  $self->print("COMMIT\n");
}

=head2 svp_begin

Called when a savepoint is created.

=cut
sub svp_begin {
  my ($self, $name) = @_;

  return if $self->callback;

  $self->print("SAVEPOINT $name\n");
}

=head2 svp_release

Called when a savepoint is released.

=cut
sub svp_release {
  my ($self, $name) = @_;

  return if $self->callback;

  $self->print("RELEASE SAVEPOINT $name\n");
}

=head2 svp_rollback

Called when rolling back to a savepoint.

=cut
sub svp_rollback {
  my ($self, $name) = @_;

  return if $self->callback;

  $self->print("ROLLBACK TO SAVEPOINT $name\n");
}

=head2 query_start

Called before a query is executed.  The first argument is the SQL string being
executed and subsequent arguments are the parameters used for the query.

=cut
sub query_start {
  my ($self, $string, @bind) = @_;

  my $message = "$string: ".join(', ', @bind)."\n";

  if(defined($self->callback)) {
    $string =~ m/^(\w+)/;
    $self->callback->($1, $message);
    return;
  }

  $self->print($message);
}

=head2 query_end

Called when a query finishes executing.  Has the same arguments as query_start.

=cut
sub query_end {
  my ($self, $string) = @_;
}

1;

=head1 AUTHOR AND CONTRIBUTORS

See L<AUTHOR|DBIx::Class/AUTHOR> and L<CONTRIBUTORS|DBIx::Class/CONTRIBUTORS> in DBIx::Class

=head1 LICENSE

You may distribute this code under the same terms as Perl itself.

=cut