=head1 NAME

DBIx::Class::AuditLog - Simple activity audit logging for DBIx::Class

=head1 SYNOPSIS

Enable the AuditLog schema component in your L<DBIx::Class::Schema> class file:

    package My::Schema;
    use base qw/DBIx::Class::Schema/;

    __PACKAGE__->load_components(qw/Schema::AuditLog/);

Enable the AuditLog component in your the individual L<DBIx::Class> table class files that you want to enable logging on:

    package My::Schema::Result::Table
    use base qw/DBIx::Class::Core/;
 
    __PACKAGE__->load_components(qw/AuditLog/);

In your application wrap any insert/update/delete in a transaction to have audit logging activated:

    $my_schema->txn_do(
        sub {
            $my_row->update({ ... });
        }
    );

Optionally pass an extra hashref to the txn_do method to indicate a user and/or a description for the transaction:

    $my_schema->txn_do(
        sub {
            $my_row->update({ ... });
        },
        {
            user => 'username_or_id', # optional
            description => 'description of transaction' # optional
        }
    );

=head1 DESCRIPTION

DBIx::Class::AuditLog is meant for tracking changes made to specific tables in your database.

Any insert/update/delete that requires auditing must be wrapped in a L<"txn_do"|DBIx::Class::Schema/"txn_do"> statement.

Transactions are saved as Changesets.  Each Changeset can have many Actions.  An Action can be of type insert/update/delete.  Actions can have many Changes. Changes show the data that was changed during an action.

By default all updated columns will be audited in any table where the AuditLog component is loaded.

=head1 ADDITIONAL DBIC COLUMN ATTRIBUTES

Individual columns can have additional attributes added to change the Audit Log functionality.

=head2 audit_log_column

On an individual column basis you can disable auditing by setting 'audit_log_column' to 0:

    __PACKAGE__->add_columns(
      "admin_id",
      { data_type => "integer", is_auto_increment => 1, is_nullable => 0, audit_log_column => 0 },
      "admin_name",
      { data_type => "varchar", is_nullable => 0, size => 20 },
      "admin_pasword",
      { data_type => "varchar", is_nullable => 0, size => 20 },
    );

If you are using a DBIx::Class generated schema, and don't want to modify the column defintions directly, you can add the following to the editable portion of the Result Class file:

    __PACKAGE__->add_columns(
        "+admin_id",
        { audit_log_column => 0, }
    );
    
=head2 force_audit_log_column

By default, columns are only audited if their value changed.
It is possible to force auditing on a per-column basis by setting 
'force_audit_log_column' to 1:

    __PACKAGE__->add_columns(
        "+admin_id",
        { force_audit_log_column => 1, }
    );

If auditing is forced for a column, the 'audit_log_column' attribute is ignored.
    
=head2 modify_audit_value

It is possible to modify the values stored by DBIC::AuditLog on a per-column basis
by setting the 'modify_audit_value' attibute to either a CodeRef, a method
name or any true value. The configured code will be run as an object method of
the current DBIC::Result object, and expects the original value as parameter.

If 'modify_audit_value' is set to a true value which is NOT a method in the
current objects class, AuditLog will look for a method called
'modify_audit_$colname', where $colname is the name of the corresponding column.

Note: AuditLog will simply die if it can not find the modification method while
'modify_audit_value' is true.

=head3 EXAMPLES:

The following examples have the same result:

=over

=item * passing a coderef:

    __PACKAGE__->add_columns(
        "+name",
        { modify_audit_value => sub{
	    my ($self, $value) = @_;
	    $value =~ tr/A-Z/a-z/;
	    return $value;
	}, }
    );
    
=item * passing a method name:

    __PACKAGE__->add_columns(
        "+name",
        { modify_audit_value => 'to_lowercase'}, 
    );
	
    sub to_lowercase{
        my ($self, $value) = @_;
        $value =~ tr/A-Z/a-z/;
        return $value;
    }

=item * passing a true value which is NOT a method name:

    __PACKAGE__->add_columns(
        "+name",
        { modify_audit_value => 1}, 
    );
	
    sub modify_audit_name{
        my ($self, $value) = @_;
        $value =~ tr/A-Z/a-z/;
        return $value;
    }

=back 

=head1 TABLE STRUCTURE

The AuditLog schema is a self-contained schema that keeps no relationships to your main schema.

The AuditLog schema consists of 6 tables:

    +-------------------------+
    | Tables_audit_log_schema |
    +-------------------------+
    | audit_log_action        |
    | audit_log_change        |
    | audit_log_changeset     |
    | audit_log_field         |
    | audit_log_table         |
    | audit_log_user          |
    +-------------------------+

=over 4

=item User

This table contains a unique list of users that have executed transactions.  The 'name' field is used to store the User identifier.  This could be used for a user's name or id or other unique identifier as needed.

This table does not get a relationship to any table in your main schema.

    mysql> select * from audit_log_user order by id;
    +----+---------------------+
    | id | name                |
    +----+---------------------+
    |  1 | TestAdminUser       |
    |  2 | YetAnotherAdminUser |
    |  3 | ioncache            |
    |  4 | markj               |
    +----+---------------------+
    4 rows in set (0.01 sec)
    
=item Changeset

An L<AuditLogChangeset|DBIx::Class::AuditLog::Schema::Structure::Changeset> is an identifier for a transaction.  It can have many L<Actions|DBIx::Class::AuditLog::Schema::Structure::Action>.  It can optionally be owned by a L<User|DBIx::Class::AuditLog::Schema::Structure::User>.  And optionally have a description.

    mysql> select * from audit_log_changeset order by id;
    +----+----------------------------------------------+---------------------+------+
    | id | description                                  | timestamp           | user |
    +----+----------------------------------------------+---------------------+------+
    |  1 | adding new user: JohnSample                  | 2012-06-22 17:16:25 |    1 |
    |  2 | updating username: JaneSample                | 2012-06-22 17:16:25 |    1 |
    |  3 | delete user: JohnSample                      | 2012-06-22 17:16:25 |    2 |
    |  4 | adding new user: TehPwnerer -- no admin user | 2012-06-22 17:16:25 | NULL |
    |  5 | multi-action changeset                       | 2012-06-22 17:16:25 |    3 |
    |  6 | NULL                                         | 2012-06-22 17:16:25 |    4 |
    +----+----------------------------------------------+---------------------+------+
    6 rows in set (0.00 sec)

=item Action

An L<AuditLogAction|DBIx::Class::AuditLog::Schema::Structure::Action> is an insert/update/delete belonging to a L<Changeset|DBIx::Class::AuditLog::Schema::Structure::Changeset>.  It is also owned by L<Table|DBIx::Class::AuditLog::Schema::Structure::AuditedTable>.

    mysql> select * from audit_log_action order by id;
    +----+-----------+---------------+-------------+--------+
    | id | changeset | audited_table | audited_row | type   |
    +----+-----------+---------------+-------------+--------+
    |  1 |         1 |             1 |           8 | insert |
    |  2 |         2 |             1 |           7 | update |
    |  3 |         3 |             1 |           7 | delete |
    |  4 |         4 |             1 |           9 | insert |
    |  5 |         5 |             1 |          10 | insert |
    |  6 |         5 |             1 |          11 | insert |
    |  7 |         5 |             1 |          11 | update |
    |  8 |         5 |             1 |           9 | update |
    |  9 |         6 |             1 |          13 | insert |
    | 10 |         6 |             1 |          13 | update |
    +----+-----------+---------------+-------------+--------+
    10 rows in set (0.00 sec)

=item Change

An L<AuditLogChange|DBIx::Class::AuditLog::Schema::Structure::Change> contains changed data for one AuditLogField in an AuditLogAction.  The original value is stored in the old_value field and the new value is stored in the new_value field.

    mysql> select * from audit_log_change order by id;
    +----+--------+-------+--------------+--------------+
    | id | action | field | old_value    | new_value    |
    +----+--------+-------+--------------+--------------+
    |  1 |      1 |     1 | NULL         | JohnSample   |
    |  2 |      1 |     2 | NULL         | 8            |
    |  3 |      1 |     3 | NULL         | 999-888-7777 |
    |  4 |      3 |     1 | JohnSample   | NULL         |
    |  5 |      3 |     2 | 7            | NULL         |
    |  6 |      3 |     3 | 999-888-7777 | NULL         |
    |  7 |      4 |     1 | NULL         | TehPnwerer   |
    |  8 |      4 |     2 | NULL         | 9            |
    |  9 |      4 |     3 | NULL         | 999-888-7777 |
    | 10 |      5 |     1 | NULL         | Superman     |
    | 11 |      5 |     2 | NULL         | 10           |
    | 12 |      5 |     3 | NULL         | 123-456-7890 |
    | 13 |      6 |     1 | NULL         | Spiderman    |
    | 14 |      6 |     2 | NULL         | 11           |
    | 15 |      6 |     3 | NULL         | 987-654-3210 |
    | 16 |      8 |     1 | TehPnwerer   | TehPwnerer   |
    | 17 |      8 |     3 | 999-888-7777 | 416-123-4567 |
    | 18 |      9 |     1 | NULL         | Drunk Hulk   |
    | 19 |      9 |     2 | NULL         | 13           |
    | 20 |      9 |     3 | NULL         | 123-456-7890 |
    +----+--------+-------+--------------+--------------+
    20 rows in set (0.00 sec)

=item AuditedTable

An L<AuditLogAuditedTable|DBIx::Class::AuditLog::Schema::Structure::AuditedTable> contains a unique list of tables that are being tracked.  The name field contains the name of a table from your database.  AuditLogAuditedTable rows are added as needed whenever an insert/update/date occurs.

Note: at least for DB2, the table name will have the schema name added as well, eg., myschema.foo for the foo table in schema myschema.

    mysql> select * from audit_log_table order by id;
    +----+------+
    | id | name |
    +----+------+
    |  1 | user |
    +----+------+
    1 row in set (0.00 sec)

=item Field

An L<AuditLogField|DBIx::Class::AuditLog::Schema::Structure::Field> contains a unique list of fields for each table that is being audited.  The name field contains the name of a field from a specific table inyour database.  AuditLogField rows are added as needed whenever an insert/update/date occurs.

    mysql> select * from audit_log_field order by id;
    +----+---------------+-------+
    | id | audited_table | name  |
    +----+---------------+-------+
    |  1 |             1 | name  |
    |  2 |             1 | id    |
    |  3 |             1 | phone |
    +----+---------------+-------+
    3 rows in set (0.00 sec)
    
=back

=head1 DEPLOYMENT

To deploy an AuditLog schema, load your main schema, and then run the deploy command on the audit_log_schema:

    my $schema = AuditTest::Schema->connect( "DBI:mysql:database=audit_test",
        "root", "somepassword", { RaiseError => 1, PrintError => 0 } );
    
    $schema->audit_log_schema->deploy;

The db user that is deploying the schema must have the correct create table permissions.

Note: this should only be run once.

=head1 METHODS

=head2 audit_log_schema

=over 4

=item Returns: DBIC schema

=back

The Audit Log schema can be accessed from your main schema by calling the audit_log_schema method.

    my $al_schema = $schema->audit_log_schema;

=head2 get_changes

=over 4

=item Required: id, table

=item Optional: action_type, change_order, field, timestamp

=item Returns: DBIC resultset

=back

A convenience method for reading changes from the Audit Log.

    my $al_schema = $schema->audit_log_schema;
    my $changes = $al_schema->get_changes({
        id           => 1,
        table        => 'foo',
        field        => 'bar',           # optional
        action_type  => 'insert',        # optional, 1 of insert, update, delete
        timestamp    => { '>=', $time }, # optional, $time must be a DateTime object,
        change_order => 'asc',           # optional, 1 of asc, desc
    });
    
=head1 TODO

=over 4

=item * add auto-deploy of schema if it doesn't exist

=item * add more convenience method(s) for retrieving changes from the Audit Log schema

=back

=head1 SEE ALSO

=over 4

=item * L<DBIx::Class>

=item * L<DBIx::Class::Journal>

=back

=head1 ACKNOWLEDGEMENTS

Development time supported by OANDA L<www.oanda.com|http://www.oanda.com>.

Many ideas and code borrowed from L<DBIx::Class::Journal>.

=head1 AUTHOR

Mark Jubenville (L<ioncache|mailto:ioncache@gmail.com>)

=head1 COPYRIGHT AND LICENCE

This software is copyright (c) 2012 by Mark Jubenville.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

=cut
