# $Header: /home/jesse/DBIx-SearchBuilder/history/SearchBuilder/Record/Cachable.pm,v 1.6 2001/06/19 04:22:32 jesse Exp $
# by Matt Knopp <mhat@netlag.com>

package DBIx::SearchBuilder::Record::Cachable;

use strict;
use warnings;

use DBIx::SearchBuilder::Handle;
use Cache::Simple::TimedExpiry;

use base qw(DBIx::SearchBuilder::Record);

=head1 NAME

DBIx::SearchBuilder::Record::Cachable - Records with caching behavior

=head1 SYNOPSIS

  package MyRecord;
  use base qw/DBIx::SearchBuilder::Record::Cachable/;

=head1 DESCRIPTION

This module subclasses the main L<DBIx::SearchBuilder::Record> package
to add a caching layer.

The public interface remains the same, except that records which have
been loaded in the last few seconds may be reused by subsequent fetch
or load methods without retrieving them from the database.

=head1 METHODS

=cut


my %_CACHES = ();

sub _SetupCache {
    my ($self, $cache) = @_;
    $_CACHES{$cache} = Cache::Simple::TimedExpiry->new();
    $_CACHES{$cache}->expire_after( $self->_CacheConfig->{'cache_for_sec'} );
    return $_CACHES{$cache};
}


=head2 FlushCache

This class method flushes the _global_ DBIx::SearchBuilder::Record::Cachable 
cache. All caches are immediately expired.

=cut

sub FlushCache {
    %_CACHES = ();
}

=head2 _FlushKeyCache

Blow away this record type's key cache

=cut

sub _FlushKeyCache {
    my $self = shift;
    my $cache = ($self->{_class}||= ref($self))."-KEYS";
    return $self->_SetupCache($cache);
}

sub _KeyCache {
    my $self = shift;
    my $cache = ($self->{_class}||= ref($self))."-KEYS";
    return $_CACHES{$cache} || $self->_SetupCache($cache);
}

sub _RecordCache {
    my $self = shift;
    my $cache = ($self->{_class}||= ref($self));
    return $_CACHES{$cache} || $self->_SetupCache($cache);
}

# Function: LoadFromHash
# Type    : (overloaded) public instance
# Args    : See DBIx::SearchBuilder::Record::LoadFromHash
# Lvalue  : array(boolean, message)

sub LoadFromHash {
    my $self = shift;

    # Blow away the primary cache key since we're loading.
    $self->{'_SB_Record_Primary_RecordCache_key'} = undef;
    my ( $rvalue, $msg ) = $self->SUPER::LoadFromHash(@_);

    ## Check the return value, if its good, cache it!
    $self->_store if $rvalue;

    return ( $rvalue, $msg );
}

# Function: LoadByCols
# Type    : (overloaded) public instance
# Args    : see DBIx::SearchBuilder::Record::LoadByCols
# Lvalue  : array(boolean, message)

sub LoadByCols {
    my ( $self, %attr ) = @_;

    # Blow away the primary cache key since we're loading.
    $self->{'_SB_Record_Primary_RecordCache_key'} = undef;

    # generate the alternate cache key
    my $alt_key = $self->_gen_alternate_RecordCache_key(%attr);
    # get primary cache key
    my $cache_key = $self->_lookup_primary_RecordCache_key($alt_key);
    if ( $cache_key && $self->_fetch( $cache_key ) ) {
        return ( 1, "Fetched from cache" );
    }

    # Fetch from the DB!
    my ( $rvalue, $msg ) = $self->SUPER::LoadByCols(%attr);
    # Check the return value, if its good, cache it!
    if ($rvalue) {
        $self->_store();
        # store alt_key as alias for pk
        $self->_KeyCache->set( $alt_key, $self->_primary_RecordCache_key);
    }
    return ( $rvalue, $msg );
}

# Function: __Set
# Type    : (overloaded) public instance
# Args    : see DBIx::SearchBuilder::Record::_Set
# Lvalue  : ?

sub __Set () {
    my $self = shift;

    $self->_expire;

    return $self->SUPER::__Set( @_ );
}

# Function: Delete
# Type    : (overloaded) public instance
# Args    : nil
# Lvalue  : ?

sub __Delete () {
    my $self = shift;

    $self->_expire;

    return $self->SUPER::__Delete( @_ );

}

# Function: _expire
# Type    : private instance
# Args    : string(cache_key)
# Lvalue  : 1
# Desc    : Removes this object from the cache.

sub _expire (\$) {
    my $self = shift;
    my $cache_key = $self->_primary_RecordCache_key or return;
    $self->_RecordCache->set( $cache_key, undef, time-1 );
    # We should be doing something more surgical to clean out the
    # key cache. but we do need to expire it
    $self->_FlushKeyCache;
}

# Function: _fetch
# Type    : private instance
# Args    : string(cache_key)
# Lvalue  : 1
# Desc    : Get an object from the cache, and make this object that.

sub _fetch () {
    my ( $self, $cache_key ) = @_;
    my $data = $self->_RecordCache->fetch( $cache_key ) or return 0;
    @{$self}{keys %$data} = values %$data; # deserialize
    return 1;
}


# Function: _store
# Type    : private instance
# Args    : string(cache_key)
# Lvalue  : 1
# Desc    : Stores this object in the cache.

sub _store (\$) {
    my $self = shift;
    my $key = $self->_primary_RecordCache_key or return 0;
    $self->_RecordCache->set( $key, $self->_serialize );
    return 1;
}

sub _serialize {
    my $self = shift;
    return {
        values  => $self->{'values'},
        table   => $self->Table,
        fetched => $self->{'fetched'}
    };
}

# Function: _gen_alternate_RecordCache_key
# Type    : private instance
# Args    : hash (attr)
# Lvalue  : 1
# Desc    : Takes a perl hash and generates a key from it.

sub _gen_alternate_RecordCache_key {
    my ( $self, %attr ) = @_;
    my $cache_key = '';
    foreach my $key ( sort keys %attr ) {
        my $value = $attr{$key};
        unless ( defined $value ) {
            $value = '=__undef';
        }
        elsif ( ref($value) eq "HASH" ) {
            $value = ( $value->{operator} || '=' )
                . ( defined $value->{value}? $value->{value}: '__undef' );
        }
        else {
            $value = "=" . $value;
        }
        $cache_key .= $key . $value . ',';
    }
    chop($cache_key);
    return ($cache_key);
}

# Function: _primary_RecordCache_key
# Type    : private instance
# Args    : none
# Lvalue: : 1
# Desc    : generate a primary-key based variant of this object's cache key
#           primary keys is in the cache

sub _primary_RecordCache_key {
    my ($self) = @_;

    return $self->{'_SB_Record_Primary_RecordCache_key'}
        if $self->{'_SB_Record_Primary_RecordCache_key'};

    my $cache_key = '';
    my %pk = $self->PrimaryKeys;
    foreach my $key ( sort keys %pk ) {
        my $value = $pk{$key};
        return undef unless defined $value;
        $cache_key .= $key . '=' . $value .',';
    }
    chop $cache_key;
    return $self->{'_SB_Record_Primary_RecordCache_key'} = $cache_key;
}

# Function: lookup_primary_RecordCache_key
# Type    : private class
# Args    : string(alternate cache id)
# Lvalue  : string(cache id)

sub _lookup_primary_RecordCache_key {
    my ($self, $key) = @_;
    return undef unless $key;
    return $self->_KeyCache->fetch($key) || $key;
}

=head2 _CacheConfig 

You can override this method to change the duration of the caching from the default of 5 seconds. 

For example, to cache records for up to 30 seconds, add the following method to your class:

  sub _CacheConfig {
      { 'cache_for_sec' => 30 }
  }

=cut

sub _CacheConfig {
    return {
        'cache_p'       => 1,
        'cache_for_sec' => 5,
    };
}

1;

__END__


=head1 AUTHOR

Matt Knopp <mhat@netlag.com>

=head1 SEE ALSO

L<DBIx::SearchBuilder>, L<DBIx::SearchBuilder::Record>

=cut