package DBIx::Custom;

use strict;
use warnings;

use base 'Object::Simple';

use Carp 'croak';
use DBI;
use DBIx::Custom::Result;
use DBIx::Custom::Query;
use DBIx::Custom::QueryBuilder;
use Encode qw/encode_utf8 decode_utf8/;

__PACKAGE__->attr('dbh');
__PACKAGE__->attr([qw/user password data_source/]);
__PACKAGE__->attr([qw/default_bind_filter default_fetch_filter/]);

__PACKAGE__->dual_attr('filters', default => sub { {} },
                                  inherit => 'hash_copy');
__PACKAGE__->register_filter(
    encode_utf8 => sub { encode_utf8($_[0]) },
    decode_utf8 => sub { decode_utf8($_[0]) }
);

__PACKAGE__->attr(result_class => 'DBIx::Custom::Result');
__PACKAGE__->attr(sql_builder  => sub {DBIx::Custom::QueryBuilder->new});

__PACKAGE__->attr(cache => 1);
__PACKAGE__->attr(cache_method => sub {
    sub {
        my $self = shift;
        
        $self->{_cached} ||= {};
        
        if (@_ > 1) {
            $self->{_cached}{$_[0]} = $_[1] 
        }
        else {
            return $self->{_cached}{$_[0]}
        }
    }
});

sub connect {
    my $proto = shift;
    
    # Create
    my $self = ref $proto ? $proto : $proto->new(@_);
    
    # Information
    my $data_source = $self->data_source;
    my $user        = $self->user;
    my $password    = $self->password;
    
    # Connect
    my $dbh = eval {DBI->connect(
        $data_source,
        $user,
        $password,
        {
            RaiseError => 1,
            PrintError => 0,
            AutoCommit => 1,
        }
    )};
    
    # Connect error
    croak $@ if $@;
    
    # Database handle
    $self->dbh($dbh);
    
    return $self;
}

sub register_filter {
    my $invocant = shift;
    
    # Register filter
    my $filters = ref $_[0] eq 'HASH' ? $_[0] : {@_};
    $invocant->filters({%{$invocant->filters}, %$filters});
    
    return $invocant;
}

our %VALID_INSERT_ARGS = map { $_ => 1 } qw/table param append filter/;

sub insert {
    my ($self, %args) = @_;

    # Check arguments
    foreach my $name (keys %args) {
        croak qq{"$name" is invalid name}
          unless $VALID_INSERT_ARGS{$name};
    }
    
    # Arguments
    my $table  = $args{table} || '';
    my $param  = $args{param} || {};
    my $append = $args{append} || '';
    my $filter = $args{filter};
    
    # Insert keys
    my @insert_keys = keys %$param;
    
    # Templte for insert
    my $source = "insert into $table {insert "
               . join(' ', @insert_keys) . '}';
    $source .= " $append" if $append;
    
    # Execute query
    my $ret_val = $self->execute($source, param  => $param, 
                                            filter => $filter);
    
    return $ret_val;
}

our %VALID_UPDATE_ARGS
  = map { $_ => 1 } qw/table param where append filter allow_update_all/;

sub update {
    my ($self, %args) = @_;
    
    # Check arguments
    foreach my $name (keys %args) {
        croak qq{"$name" is invalid name}
          unless $VALID_UPDATE_ARGS{$name};
    }
    
    # Arguments
    my $table            = $args{table} || '';
    my $param            = $args{param} || {};
    my $where            = $args{where} || {};
    my $append_statement = $args{append} || '';
    my $filter           = $args{filter};
    my $allow_update_all = $args{allow_update_all};
    
    # Update keys
    my @update_keys = keys %$param;
    
    # Where keys
    my @where_keys = keys %$where;
    
    # Not exists where keys
    croak qq{"where" must contain column-value pair}
      if !@where_keys && !$allow_update_all;
    
    # Update clause
    my $update_clause = '{update ' . join(' ', @update_keys) . '}';
    
    # Where clause
    my $where_clause = '';
    my $new_where = {};
    
    if (@where_keys) {
        $where_clause = 'where ';
        foreach my $where_key (@where_keys) {
            
            $where_clause .= "{= $where_key} and ";
        }
        $where_clause =~ s/ and $//;
    }
    
    # Template for update
    my $source = "update $table $update_clause $where_clause";
    $source .= " $append_statement" if $append_statement;
    
    # Rearrange parameters
    foreach my $wkey (@where_keys) {
        
        if (exists $param->{$wkey}) {
            $param->{$wkey} = [$param->{$wkey}]
              unless ref $param->{$wkey} eq 'ARRAY';
            
            push @{$param->{$wkey}}, $where->{$wkey};
        }
        else {
            $param->{$wkey} = $where->{$wkey};
        }
    }
    
    # Execute query
    my $ret_val = $self->execute($source, param  => $param, 
                                            filter => $filter);
    
    return $ret_val;
}

sub update_all { shift->update(allow_update_all => 1, @_) };

our %VALID_DELETE_ARGS
  = map { $_ => 1 } qw/table where append filter allow_delete_all/;

sub delete {
    my ($self, %args) = @_;
    
    # Check arguments
    foreach my $name (keys %args) {
        croak qq{"$name" is invalid name}
          unless $VALID_DELETE_ARGS{$name};
    }
    
    # Arguments
    my $table            = $args{table} || '';
    my $where            = $args{where} || {};
    my $append_statement = $args{append};
    my $filter           = $args{filter};
    my $allow_delete_all = $args{allow_delete_all};
    
    # Where keys
    my @where_keys = keys %$where;
    
    # Not exists where keys
    croak qq{Key-value pairs for where clause must be specified to "delete" second argument}
      if !@where_keys && !$allow_delete_all;
    
    # Where clause
    my $where_clause = '';
    if (@where_keys) {
        $where_clause = 'where ';
        foreach my $wkey (@where_keys) {
            $where_clause .= "{= $wkey} and ";
        }
        $where_clause =~ s/ and $//;
    }
    
    # Template for delete
    my $source = "delete from $table $where_clause";
    $source .= " $append_statement" if $append_statement;
    
    # Execute query
    my $ret_val = $self->execute($source, param  => $where, 
                                            filter => $filter);
    
    return $ret_val;
}

sub delete_all { shift->delete(allow_delete_all => 1, @_) }

our %VALID_SELECT_ARGS
  = map { $_ => 1 } qw/table column where append relation filter param/;

sub select {
    my ($self, %args) = @_;
    
    # Check arguments
    foreach my $name (keys %args) {
        croak qq{"$name" is invalid name}
          unless $VALID_SELECT_ARGS{$name};
    }
    
    # Arguments
    my $tables = $args{table} || [];
    $tables = [$tables] unless ref $tables eq 'ARRAY';
    my $columns  = $args{column} || [];
    my $where    = $args{where};
    my $relation = $args{relation};
    my $append   = $args{append};
    my $filter   = $args{filter};
    
    # SQL template for select statement
    my $source = 'select ';
    
    # Column clause
    if (@$columns) {
        foreach my $column (@$columns) {
            $source .= "$column, ";
        }
        $source =~ s/, $/ /;
    }
    else {
        $source .= '* ';
    }
    
    # Table
    $source .= 'from ';
    foreach my $table (@$tables) {
        $source .= "$table, ";
    }
    $source =~ s/, $/ /;
    
    # Where clause
    my $param;
    if (ref $where eq 'HASH') {
        $param = $where;
        $source .= 'where (';
        foreach my $where_key (keys %$where) {
            $source .= "{= $where_key} and ";
        }
        $source =~ s/ and $//;
        $source .= ') ';
    }
    elsif (ref $where eq 'ARRAY') {
        my$where_str = $where->[0] || '';
        $param = $where->[1];
        
        $source .= "where ($where_str) ";
    }
    
    # Relation
    if ($relation) {
        $source .= $where ? "and " : "where ";
        foreach my $rkey (keys %$relation) {
            $source .= "$rkey = " . $relation->{$rkey} . " and ";
        }
    }
    $source =~ s/ and $//;
    
    # Append some statement
    $source .= " $append" if $append;
    
    # Execute query
    my $result = $self->execute($source, param  => $param, 
                                         filter => $filter);
    
    return $result;
}

sub create_query {
    my ($self, $source) = @_;
    
    # Cache
    my $cache = $self->cache;
    
    # Create query
    my $query;
    if ($cache) {
        
        # Get query
        my $q = $self->cache_method->($self, $source);
        
        # Create query
        $query = DBIx::Custom::Query->new($q) if $q;
    }
    
    unless ($query) {

        # Create SQL object
        my $builder = $self->sql_builder;
        
        # Create query
        $query = eval{$builder->build_query($source)};
        croak $@ if $@;
        
        # Cache query
        $self->cache_method->($self, $source,
                             {sql     => $query->sql, 
                              columns => $query->columns})
          if $cache;
    }
    
    # Prepare statement handle
    my $sth = eval {$self->dbh->prepare($query->{sql})};
    croak qq{$@ SQL: "$query->{sql}"} if $@;
    
    # Set statement handle
    $query->sth($sth);
    
    return $query;
}

our %VALID_EXECUTE_ARGS = map { $_ => 1 } qw/param filter/;

sub execute{
    my ($self, $query, %args)  = @_;
    
    # Check arguments
    foreach my $name (keys %args) {
        croak qq{"$name" is invalid name}
          unless $VALID_EXECUTE_ARGS{$name};
    }
    
    my $params = $args{param} || {};
    
    # First argument is SQL template
    $query = $self->create_query($query)
      unless ref $query;
    
    my $filter = $args{filter} || $query->filter || {};
    
    # Create bind value
    my $bind_values = $self->_build_bind_values($query, $params, $filter);
    
    # Execute
    my $sth      = $query->sth;
    my $affected = eval {$sth->execute(@$bind_values)};
    croak $@ if $@;
    
    # Return resultset if select statement is executed
    if ($sth->{NUM_OF_FIELDS}) {
        
        # Create result
        my $result = $self->result_class->new(
            sth            => $sth,
            default_filter => $self->default_fetch_filter,
            filters        => $self->filters
        );

        return $result;
    }
    return $affected;
}

sub _build_bind_values {
    my ($self, $query, $params, $filter) = @_;
    
    # binding values
    my @bind_values;
    
    # Build bind values
    my $count = {};
    foreach my $column (@{$query->columns}) {
        
        croak qq{"$column" is not exists in params}
          unless exists $params->{$column};
        
        # Value
        my $value = ref $params->{$column} eq 'ARRAY'
                  ? $params->{$column}->[$count->{$column} || 0]
                  : $params->{$column};
        
        # Filter
        $filter ||= {};
        
        # Filter name
        my $fname = $filter->{$column} || $self->default_bind_filter || '';
        
        my $filter_func;
        if ($fname) {
            
            if (ref $fname eq 'CODE') {
                $filter_func = $fname;
            }
            else {
                my $filters = $self->filters;
                croak qq{Not exists filter "$fname"}
                  unless exists $filters->{$fname};
                $filter_func = $filters->{$fname};
            }            
        }
        
        push @bind_values, $filter_func
                         ? $filter_func->($value)
                         : $value;
        
        # Count up 
        $count->{$column}++;
    }
    
    return \@bind_values;
}

=head1 NAME

DBIx::Custom - DBI interface, having hash parameter binding and filtering system

=cut

our $VERSION = '0.1608';

=head1 STABILITY

B<This module is not stable>. 
Method name and implementations will be changed for a while.

=head1 SYNOPSYS

Connect to the database.
    
    use DBIx::Custom;
    my $dbi = DBIx::Custom->connect(data_source => "dbi:mysql:database=books",
                                    user => 'ken', password => '!LFKD%$&');

Insert, update, and delete

    # Insert 
    $dbi->insert(table  => 'books',
                 param  => {title => 'perl', author => 'Ken'},
                 filter => {title => 'encode_utf8'});
    
    # Update 
    $dbi->update(table  => 'books', 
                 param  => {title => 'aaa', author => 'Ken'}, 
                 where  => {id => 5},
                 filter => {title => 'encode_utf8'});
    
    # Update all
    $dbi->update_all(table  => 'books',
                     param  => {title => 'aaa'},
                     filter => {title => 'encode_utf8'});
    
    # Delete
    $dbi->delete(table  => 'books',
                 where  => {author => 'Ken'},
                 filter => {title => 'encode_utf8'});
    
    # Delete all
    $dbi->delete_all(table => 'books');

Select

    # Select
    my $result = $dbi->select(table => 'books');
    
    # Select, more complex
    my $result = $dbi->select(
        table  => 'books',
        column => [qw/author title/],
        where  => {author => 'Ken'},
        append => 'order by id limit 1',
        filter => {title => 'encode_utf8'}
    );
    
    # Select, join table
    my $result = $dbi->select(
        table    => ['books', 'rental'],
        column   => ['books.name as book_name']
        relation => {'books.id' => 'rental.book_id'}
    );

Execute SQL

    # Execute SQL
    $dbi->execute("select title from books");
    
    # Execute SQL with hash binding and filtering
    $dbi->execute("select id from books where {= author} && {like title}",
                  param  => {author => 'ken', title => '%Perl%'},
                  filter => {title => 'encode_utf8'});

    # Create query and execute it
    my $query = $dbi->create_query(
        "select id from books where {= author} && {like title}"
    );
    $dbi->execute($query, param => {author => 'ken', title => '%Perl%'})

More features.

    # Default filter
    $dbi->default_bind_filter('encode_utf8');
    $dbi->default_fetch_filter('decode_utf8');

    # Get DBI object
    my $dbh = $dbi->dbh;

Fetch row.

    # Fetch
    while (my $row = $result->fetch) {
        # ...
    }
    
    # Fetch hash
    while (my $row = $result->fetch_hash) {
        
    }
    

=head1 DESCRIPTION

=head2 1. Features

L<DBIx::Custom> is one of L<DBI> interface modules,
such as L<DBIx::Class>, L<DBIx::Simple>.

This module is not O/R mapper. O/R mapper is useful,
but you must learn many syntax of the O/R mapper,
which is almost another language
Create SQL statement is offten not effcient and damage SQL performance.
so you have to execute raw SQL in the end.

L<DBIx::Custom> is middle area between L<DBI> and O/R mapper.
L<DBIx::Custom> provide flexible hash parameter binding adn filtering system,
and suger method, such as C<select()>, C<update()>, C<delete()>, C<select()>
to execute a query easily.

L<DBIx::Custom> respects SQL. SQL is not beautiful, but de-facto standard,
so all people learing database system know it.
If you know SQL statement,
you learn a little thing about L<DBIx::Custom> to do your works.

=head2 1. Connect to the database

C<connect()> method create a new L<DBIx::Custom>
object and connect to the database.

    use DBIx::Custom;
    my $dbi = DBIx::Custom->connect(data_source => "dbi:mysql:database=books",
                                    user => 'ken', password => '!LFKD%$&');

If database is SQLite, use L<DBIx::Custom::SQLite>. you connect database easy way.

    use DBIx::Custom::SQLite;
    my $dbi = DBIx::Custom->connect(database => 'books');
    
If database is  MySQL, use L<DBIx::Costm::MySQL>.

    use DBIx::Custom::MySQL;
    my $dbi = DBIx::Custom->connect(database => 'books',
                                    user => 'ken', password => '!LFKD%$&');

=head2 2. Suger methods

L<DBIx::Custom> has suger methods, such as C<insert()>, C<update()>,
C<delete()> and C<select()>. If you want to do simple works,
You don't have to create SQL statement.

=head3 insert()

    $dbi->insert(table  => 'books',
                 param  => {title => 'perl', author => 'Ken'});

The following SQL is executed.

    insert into (title, author) values (?, ?)

The values of C<title> and C<author> is embedded into placeholders.

C<append> and C<filter> argument can be specified if you need.

=head3 update()

    $dbi->update(table  => 'books', 
                 param  => {title => 'aaa', author => 'Ken'}, 
                 where  => {id => 5});

The following SQL is executed.

    update books set title = ?, author = ?;

The values of C<title> and C<author> is embedded into placeholders.

If you want to update all rows, use C<update_all()> method instead.

C<append> and C<filter> argument can be specified if you need.

=head3 delete()

    $dbi->delete(table  => 'books',
                 where  => {author => 'Ken'});

The following SQL is executed.

    delete from books where id = ?;

The value of C<id> is embedded into a placehodler.

C<append> and C<filter> argument can be specified if you need.

If you want to delete all rows, use C<delete_all()> method instead.

=head3 select()

Specify only table:

    my $result = $dbi->select(table => 'books');

The following SQL is executed.

    select * from books;

the result of C<select()> method is L<DBIx::Custom::Result> object.
use C<fetch()> method to fetch a row.

    while (my $row = $result->fetch) {
        my $title  = $row->[0];
        my $author = $row->[1];
    }

L<DBIx::Custom::Result> has various methods to fetch row.
See "3. Result of select statement".

Specify C<column> and C<where> arguments:

    my $result = $dbi->select(
        table  => 'books',
        column => [qw/author title/],
        where  => {author => 'Ken'});

The following SQL is executed.

    select author, title from books where author = ?;

the value of C<author> is embdded into placeholder.

If C<relation> argument is specifed, you can join tables.

    my $result = $dbi->select(
        table    => ['books', 'rental'],
        column   => ['books.name as book_name']
        relation => {'books.id' => 'rental.book_id'}
    );

The following SQL is executed.

    select books.name as book_name from books
    where books.id = rental.book_id;

C<append> argument add a string to the end of SQL statement.
It is useful to add "order by" or "limit" cluase.

    # Select, more complex
    my $result = $dbi->select(
        table  => 'books',
        where  => {author => 'Ken'},
        append => 'order by price limit 5',
    );

The following SQL is executed.

    select * books where author = ? order by price limit 5;

C<filter> argument can be specified if you need.

=head2 3. Result of select statement

C<select> method reurn L<DBIx::Custom::Result> object.
Using various methods, you can fetch row.

Fetch row into array.
    
    while (my $row = $result->fetch) {
        my $author = $row->[0];
        my $title  = $row->[1];
        
    }

Fetch only a first row into array.

    my $row = $result->fetch_first;

Fetch multiple rows into array of array.

    while (my $rows = $result->fetch_multi(5)) {
        my $first_author  = $rows->[0][0];
        my $first_title   = $rows->[0][1];
        my $second_author = $rows->[1][0];
        my $second_value  = $rows->[1][1];
    
    }
    
Fetch all rows into array of array.

    my $rows = $result->fetch_all;

Fetch row into hash.

    # Fetch a row into hash
    while (my $row = $result->fetch_hash) {
        my $title  = $row->{title};
        my $author = $row->{author};
        
    }

Fetch only a first row into hash

    my $row = $result->fetch_hash_first;
    
Fetch multiple rows into array of hash

    while (my $rows = $result->fetch_hash_multi(5)) {
        my $first_title   = $rows->[0]{title};
        my $first_author  = $rows->[0]{author};
        my $second_title  = $rows->[1]{title};
        my $second_author = $rows->[1]{author};
    
    }
    
Fetch all rows into array of hash

    my $rows = $result->fetch_hash_all;

If you want to access row statement handle of L<DBI>, use sth() attribute.

    my $sth = $result->sth;

=head2 4. Hash parameter binding

L<DBIx::Custom> provides hash parameter binding.

At frist, I show normal way of parameter binding.

    use DBI;
    my $dbh = DBI->connect(...);
    my $sth = $dbh->prepare(
        "select * from books where author = ? and title like ?;"
    );
    $sth->execute('Ken', '%Perl%');

This is very good way because database system enable SQL caching,
and parameter is quoted automatically.

L<DBIx::Custom>hash parameter binding system improve normal parameter binding to
specify hash parameter.

    my $result = $dbi->execute(
        "select * from books where {= author} and {like title};"
        param => {author => 'Ken', title => '%Perl%'}
    );

This is same as the normal way, execpt that the parameter is hash.
{= author} is called C<tag>. tag is expand to placeholder internally.

    select * from books where {= author} and {like title}
      -> select * from books where author = ? and title like ?;

See L<DBIx::Custom::QueryBuilder> to know all tags.

=head2 5. Filtering

Usually, Perl string is kept as internal string.
If you want to save the string to database, You must encode the string.
Filtering system help you to convert a data to another data
when you save to the data and get the data form database.

If you want to register filter, use register_filter() method.

    $dbi->register_filter(
        to_upper_case => sub {
            my $value = shift;
            return uc $value;
        }
    );

C<encode_utf8> and C<decode_utf8> filter is registerd by default.

You can specify these filters to C<filter> argument of C<execute()> method.

    my $result = $dbi->execute(
        "select * from books where {= author} and {like title};"
        param => {author => 'Ken', title => '%Perl%'});
        filter => {author => 'to_upper_case, title => 'encode_utf8'}
    );

you can also specify filter in suger methods, such as select(), update(), update_all,
delete(), delete_all(), select().

    $dbi->insert(table  => 'books',
                 param  => {title => 'perl', author => 'Ken'},
                 filter => {title => 'encode_utf8'});

    my $result = $dbi->select(
        table  => 'books',
        column => [qw/author title/],
        where  => {author => 'Ken'},
        append => 'order by id limit 1',
        filter => {title => 'encode_utf8'}
    );

Filter work to each parmeter, but you prepare default filter for all parameters.
you can use C<default_bind_filter()> attribute.

    $dbi->default_bind_filter('encode_utf8');

C<filter()> argument overwrites the filter specified by C<default_bind_filter()>.
    
    $dbi->default_bind_filter('encode_utf8');
    $dbi->insert(
        table  => 'books',
        param  => {title => 'perl', author => 'Ken', price => 1000},
        filter => {author => 'to_upper_case', price => undef}
    );

This is same as the following one.

    $dbi->insert(
        table  => 'books',
        param  => {title => 'perl', author => 'Ken', price => 1000},
        filter => {title => 'encode_uft8' author => 'to_upper_case'}
    );

You can also specify filter when the row is fetching. This is reverse of bindig filter.

    my $result = $dbi->select(table => 'books');
    $result->filter({title => 'decode_utf8', author => 'to_upper_case'});

you can specify C<default_fetch_filter()>.

    $dbi->default_fetch_filter('decode_utf8');

C<DBIx::Custom::Result::filter> overwrites the filter specified
by C<default_fetch_filter()>

    $dbi->default_fetch_filter('decode_utf8');
    my $result = $dbi->select(
        table => 'books',
        columns => ['title', 'author', 'price']
    );
    $result->filter({author => 'to_upper_case', price => undef});

This is same as the following one.

    my $result = $dbi->select(
        table => 'books',
        columns => ['title', 'author', 'price']
    );
    $result->filter({title => 'decode_utf8', author => 'to_upper_case'});

=head1 ATTRIBUTES

=head2 C<user>

    my $user = $dbi->user;
    $dbi     = $dbi->user('Ken');

User name.
C<connect()> method use this value to connect the database.
    
=head2 C<password>

    my $password = $dbi->password;
    $dbi         = $dbi->password('lkj&le`@s');

Password.
C<connect()> method use this value to connect the database.

=head2 C<data_source>

    my $data_source = $dbi->data_source;
    $dbi            = $dbi->data_source("DBI:mysql:database=dbname");

Data source.
C<connect()> method use this value to connect the database.

=head2 C<dbh>

    my $dbh = $dbi->dbh;
    $dbi    = $dbi->dbh($dbh);

L<DBI> object. You can call all methods of L<DBI>.

=head2 C<filters>

    my $filters = $dbi->filters;
    $dbi        = $dbi->filters(\%filters);

Filter functions.
"encode_utf8" and "decode_utf8" is registered by default.

=head2 C<default_bind_filter>

    my $default_bind_filter = $dbi->default_bind_filter
    $dbi                    = $dbi->default_bind_filter('encode_utf8');

Default filter when parameter binding is executed.

=head2 C<default_fetch_filter>

    my $default_fetch_filter = $dbi->default_fetch_filter;
    $dbi                     = $dbi->default_fetch_filter('decode_utf8');

Default filter when row is fetched.

=head2 C<result_class>

    my $result_class = $dbi->result_class;
    $dbi             = $dbi->result_class('DBIx::Custom::Result');

Result class for select statement.
Default to L<DBIx::Custom::Result>.

=head2 C<sql_builder>

    my $sql_class = $dbi->sql_builder;
    $dbi          = $dbi->sql_builder(DBIx::Custom::QueryBuilder->new);

SQL builder. sql_builder must be 
the instance of L<DBIx::Custom::QueryBuilder> subclass.
Default to L<DBIx::Custom::QueryBuilder> object.

=head2 C<cache>

    my $cache = $dbi->cache;
    $dbi      = $dbi->cache(1);

Enable parsed L<DBIx::Custom::Query> object caching.
Default to 1.

=head2 C<cache_method>

    $dbi          = $dbi->cache_method(\&cache_method);
    $cache_method = $dbi->cache_method

Method to set and get caches.

B<Example:>

    $dbi->cache_method(
        sub {
            my $self = shift;
            
            $self->{_cached} ||= {};
            
            if (@_ > 1) {
                $self->{_cached}{$_[0]} = $_[1] 
            }
            else {
                return $self->{_cached}{$_[0]}
            }
        }
    );

=head1 METHODS

L<DBIx::Custom> inherits all methods from L<Object::Simple>
and implements the following new ones.

=head2 C<connect>

    my $dbi = DBIx::Custom->connect(data_source => "dbi:mysql:database=dbname",
                                    user => 'ken', password => '!LFKD%$&');

Create a new L<DBIx::Custom> object and connect to the database.
L<DBIx::Custom> is a wrapper of L<DBI>.
C<AutoCommit> and C<RaiseError> option is true, 
and C<PrintError> option is false by default. 

=head2 C<insert>

    $dbi->insert(table  => $table, 
                 param  => \%param,
                 append => $append,
                 filter => \%filter);

Execute insert statement.
C<insert> method have C<table>, C<param>, C<append>
and C<filter> arguments.
C<table> is a table name.
C<param> is column-value pairs. this must be hash reference.
C<append> is a string added at the end of the SQL statement.
C<filter> is filters when parameter binding is executed.
This is overwrites C<default_bind_filter>.
Return value of C<insert> is the count of affected rows.

B<Example:>

    $dbi->insert(table  => 'books', 
                 param  => {title => 'Perl', author => 'Taro'},
                 append => "some statement",
                 filter => {title => 'encode_utf8'})

=head2 C<update>

    $dbi->update(table  => $table, 
                 param  => \%params,
                 where  => \%where,
                 append => $append,
                 filter => \%filter)

Execute update statement.
C<update> method have C<table>, C<param>, C<where>, C<append>
and C<filter> arguments.
C<table> is a table name.
C<param> is column-value pairs. this must be hash reference.
C<where> is where clause. this must be hash reference.
C<append> is a string added at the end of the SQL statement.
C<filter> is filters when parameter binding is executed.
This is overwrites C<default_bind_filter>.
Return value of C<update> is the count of affected rows.

B<Example:>

    $dbi->update(table  => 'books',
                 param  => {title => 'Perl', author => 'Taro'},
                 where  => {id => 5},
                 append => "for update",
                 filter => {title => 'encode_utf8'});

=head2 C<update_all>

    $dbi->update_all(table  => $table, 
                     param  => \%params,
                     filter => \%filter,
                     append => $append);

Execute update statement to update all rows.
Arguments is same as C<update> method,
except that C<update_all> don't have C<where> argument.
Return value of C<update_all> is the count of affected rows.

B<Example:>

    $dbi->update_all(table  => 'books', 
                     param  => {author => 'taro'},
                     filter => {author => 'encode_utf8'});

=head2 C<delete>

    $dbi->delete(table  => $table,
                 where  => \%where,
                 append => $append,
                 filter => \%filter);

Execute delete statement.
C<delete> method have C<table>, C<where>, C<append>, and C<filter> arguments.
C<table> is a table name.
C<where> is where clause. this must be hash reference.
C<append> is a string added at the end of the SQL statement.
C<filter> is filters when parameter binding is executed.
Return value of C<delete> is the count of affected rows.

B<Example:>

    $dbi->delete(table  => 'books',
                 where  => {id => 5},
                 append => 'some statement',
                 filter => {id => 'encode_utf8'});

=head2 C<delete_all>

    $dbi->delete_all(table => $table);

Execute delete statement to delete all rows.
Arguments is same as C<delete> method,
except that C<delete_all> don't have C<where> argument.
Return value of C<delete_all> is the count of affected rows.

B<Example:>
    
    $dbi->delete_all(table => 'books');

=head2 C<select>
    
    my $result = $dbi->select(table    => $table,
                              column   => [@column],
                              where    => \%where,
                              append   => $append,
                              relation => \%relation,
                              filter   => \%filter);

Execute select statement.
C<select> method have C<table>, C<column>, C<where>, C<append>
C<relation> and C<filter> arguments.
C<table> is a table name.
C<where> is where clause. this must be hash reference
or a string containing such tags as "{= title} or {= author}".
C<append> is a string added at the end of the SQL statement.
C<filter> is filters when parameter binding is executed.

B<Example:>

    # select * from books;
    my $result = $dbi->select(table => 'books');
    
    # select * from books where title = ?;
    my $result = $dbi->select(table => 'books', where => {title => 'Perl'});
    
    # select title, author from books where id = ? for update;
    my $result = $dbi->select(
        table  => 'books',
        column => ['title', 'author'],
        where  => {id => 1},
        appned => 'for update'
    );
    
    # select books.name as book_name from books, rental 
    # where books.id = rental.book_id;
    my $result = $dbi->select(
        table    => ['books', 'rental'],
        column   => ['books.name as book_name']
        relation => {'books.id' => 'rental.book_id'}
    );

=head2 C<create_query>
    
    my $query = $dbi->create_query(
        "select * from authors where {= name} and {= age};"
    );

Create the instance of L<DBIx::Custom::Query> from SQL source.

=head2 C<execute>

    my $result = $dbi->execute($query,  param => $params, filter => \%filter);
    my $result = $dbi->execute($source, param => $params, filter => \%filter);

Execute query or SQL source. Query is L<DBIx::Csutom::Query> object.
Return value is L<DBIx::Custom::Result> in select statement,
or the count of affected rows in insert, update, delete statement.

B<Example:>

    my $result = $dbi->execute("select * from authors where {= name} and {= age}", 
                            param => {name => 'taro', age => 19});
    
    while (my $row = $result->fetch) {
        # do something
    }

=head2 C<register_filter>

    $dbi->register_filter(%filters);
    $dbi->register_filter(\%filters);
    
Register filter. Registered filters is available in the following methods
or arguments.

=over 4

=item *

C<default_bind_filter()>

=item *

C<default_fetch_filter()>

=item *

C<filter> argument of C<insert()>, C<update()>,
C<update_all()>, C<delete()>, C<delete_all()>, C<select()>,
C<execute> method.

=item *

C<DBIx::Custom::Query::default_filter()>

=item *

C<DBIx::Csutom::Query::filter()>

=item *

C<DBIx::Custom::Result::default_filter()>

=item *

C<DBIx::Custom::Result::filter()>

=back

B<Example:>

    $dbi->register_filter(
        encode_utf8 => sub {
            my $value = shift;
            
            require Encode;
            
            return Encode::encode('UTF-8', $value);
        },
        decode_utf8 => sub {
            my $value = shift;
            
            require Encode;
            
            return Encode::decode('UTF-8', $value)
        }
    );

=head1 BUGS

Please tell me bugs if found.

C<< <kimoto.yuki at gmail.com> >>

L<http://github.com/yuki-kimoto/DBIx-Custom>

=head1 AUTHOR

Yuki Kimoto, C<< <kimoto.yuki at gmail.com> >>

=head1 COPYRIGHT & LICENSE

Copyright 2009 Yuki Kimoto, all rights reserved.

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

=cut