DBIx::Class::Schema::Loader::RelBuilder - Builds relationships for DBIx::Class::Schema::Loader

    [
        {
            local_columns => [ 'col2', 'col3' ],
            remote_columns => [ 'col5', 'col7' ],
            remote_moniker => 'AnotherTableMoniker',
        },
        {
            local_columns => [ 'col1', 'col4' ],
            remote_columns => [ 'col1', 'col2' ],
            remote_moniker => 'YetAnotherTableMoniker',
        },
        # ...
    ],

  {
      'Some::Source::Class' => [
          { method => 'belongs_to', arguments => [ 'col1', 'Another::Source::Class' ],
          { method => 'has_many', arguments => [ 'anothers', 'Yet::Another::Source::Class', 'col15' ],
      ],
      'Another::Source::Class' => [
          # ...
      ],
      # ...
  }

package DBIx::Class::Schema::Loader::RelBuilder;

use strict;
use warnings;
use base 'Class::Accessor::Grouped';
use mro 'c3';
use Carp::Clan qw/^DBIx::Class/;
use Scalar::Util 'weaken';
use Lingua::EN::Inflect::Phrase ();
use DBIx::Class::Schema::Loader::Utils 'split_name';
use File::Slurp 'slurp';
use Try::Tiny;
use Class::Unload ();
use Class::Inspector ();
use List::MoreUtils 'apply';
use namespace::clean;

our $VERSION = '0.07010';

# Glossary:
#
# remote_relname -- name of relationship from the local table referring to the remote table
# local_relname  -- name of relationship from the remote table referring to the local table
# remote_method  -- relationship type from remote table to local table, usually has_many

__PACKAGE__->mk_group_accessors('simple', qw/
    base
    schema
    inflect_plural
    inflect_singular
    relationship_attrs
    rel_collision_map
    _temp_classes
/);

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

    # from old POD about this constructor:
    # C<$schema_class> should be a schema class name, where the source
    # classes have already been set up and registered.  Column info,
    # primary key, and unique constraints will be drawn from this
    # schema for all of the existing source monikers.

    # Options inflect_plural and inflect_singular are optional, and
    # are better documented in L<DBIx::Class::Schema::Loader::Base>.

    my $self = {
        base               => $base,
        schema             => $base->schema,
        inflect_plural     => $base->inflect_plural,
        inflect_singular   => $base->inflect_singular,
        relationship_attrs => $base->relationship_attrs,
        rel_collision_map  => $base->rel_collision_map,
        _temp_classes      => [],
    };

    weaken $self->{base}; #< don't leak

    bless $self => $class;

    # validate the relationship_attrs arg
    if( defined $self->relationship_attrs ) {
	ref $self->relationship_attrs eq 'HASH'
	    or croak "relationship_attrs must be a hashref";
    }

    return $self;
}


# pluralize a relationship name
sub _inflect_plural {
    my ($self, $relname) = @_;

    return '' if !defined $relname || $relname eq '';

    if( ref $self->inflect_plural eq 'HASH' ) {
        return $self->inflect_plural->{$relname}
            if exists $self->inflect_plural->{$relname};
    }
    elsif( ref $self->inflect_plural eq 'CODE' ) {
        my $inflected = $self->inflect_plural->($relname);
        return $inflected if $inflected;
    }

    return $self->_to_PL($relname);
}

# Singularize a relationship name
sub _inflect_singular {
    my ($self, $relname) = @_;

    return '' if !defined $relname || $relname eq '';

    if( ref $self->inflect_singular eq 'HASH' ) {
        return $self->inflect_singular->{$relname}
            if exists $self->inflect_singular->{$relname};
    }
    elsif( ref $self->inflect_singular eq 'CODE' ) {
        my $inflected = $self->inflect_singular->($relname);
        return $inflected if $inflected;
    }

    return $self->_to_S($relname);
}

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

    $name =~ s/_/ /g;
    my $plural = Lingua::EN::Inflect::Phrase::to_PL($name);
    $plural =~ s/ /_/g;

    return $plural;
}

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

    $name =~ s/_/ /g;
    my $singular = Lingua::EN::Inflect::Phrase::to_S($name);
    $singular =~ s/ /_/g;

    return $singular;
}

sub _default_relationship_attrs { +{
    has_many => {
        cascade_delete => 0,
        cascade_copy   => 0,
    },
    might_have => {
        cascade_delete => 0,
        cascade_copy   => 0,
    },
    belongs_to => {
        on_delete => 'CASCADE',
        on_update => 'CASCADE',
        is_deferrable => 1,
    },
} }

# accessor for options to be passed to each generated relationship
# type.  take single argument, the relationship type name, and returns
# either a hashref (if some options are set), or nothing
sub _relationship_attrs {
    my ( $self, $reltype ) = @_;
    my $r = $self->relationship_attrs;

    my %composite = (
        %{ $self->_default_relationship_attrs->{$reltype} || {} },
        %{ $r->{all} || {} }
    );

    if( my $specific = $r->{$reltype} ) {
	while( my ($k,$v) = each %$specific ) {
	    $composite{$k} = $v;
	}
    }
    return \%composite;
}

sub _array_eq {
    my ($self, $a, $b) = @_;

    return unless @$a == @$b;

    for (my $i = 0; $i < @$a; $i++) {
        return unless $a->[$i] eq $b->[$i];
    }
    return 1;
}

sub _remote_attrs {
    my ($self, $local_moniker, $local_cols) = @_;

    # get our base set of attrs from _relationship_attrs, if present
    my $attrs = $self->_relationship_attrs('belongs_to') || {};

    # If the referring column is nullable, make 'belongs_to' an
    # outer join, unless explicitly set by relationship_attrs
    my $nullable = grep { $self->schema->source($local_moniker)->column_info($_)->{is_nullable} } @$local_cols;
    $attrs->{join_type} = 'LEFT' if $nullable && !defined $attrs->{join_type};

    return $attrs;
}

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

    if (ref $name) {
        # scalar ref for weird table name (like one containing a '.')
        ($name = $$name) =~ s/\W+/_/g;
    }
    else {
        # remove 'schema.' prefix if any
        $name =~ s/^[^.]+\.//;
    }

    return $name;
}

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

    $name = $self->_sanitize_name($name);

    my @words = split_name $name;

    return join '_', map lc, @words;
}

sub _remote_relname {
    my ($self, $remote_table, $cond) = @_;

    my $remote_relname;
    # for single-column case, set the remote relname to the column
    # name, to make filter accessors work, but strip trailing _id
    if(scalar keys %{$cond} == 1) {
        my ($col) = values %{$cond};
        $col = $self->_normalize_name($col);
        $col =~ s/_id$//;
        $remote_relname = $self->_inflect_singular($col);
    }
    else {
        $remote_relname = $self->_inflect_singular($self->_normalize_name($remote_table));
    }

    return $remote_relname;
}

sub _resolve_relname_collision {
    my ($self, $moniker, $cols, $relname) = @_;

    return $relname if $relname eq 'id'; # this shouldn't happen, but just in case

    if ($self->base->_is_result_class_method($relname)) {
        if (my $map = $self->rel_collision_map) {
            for my $re (keys %$map) {
                if (my @matches = $relname =~ /$re/) {
                    return sprintf $map->{$re}, @matches;
                }
            }
        }

        my $new_relname = $relname;
        while ($self->base->_is_result_class_method($new_relname)) {
            $new_relname .= '_rel'
        }

        warn <<"EOF";
Relationship '$relname' in source '$moniker' for columns '@{[ join ',', @$cols ]}' collides with an inherited method.
Renaming to '$new_relname'.
See "RELATIONSHIP NAME COLLISIONS" in perldoc DBIx::Class::Schema::Loader::Base .
EOF

        return $new_relname;
    }

    return $relname;
}

sub generate_code {
    my ($self, $local_moniker, $rels, $uniqs) = @_;

    my $all_code = {};

    my $local_class = $self->schema->class($local_moniker);

    my %counters;
    foreach my $rel (@$rels) {
        next if !$rel->{remote_source};
        $counters{$rel->{remote_source}}++;
    }

    foreach my $rel (@$rels) {
        my $remote_moniker = $rel->{remote_source}
            or next;

        my $remote_class   = $self->schema->class($remote_moniker);
        my $remote_obj     = $self->schema->source($remote_moniker);
        my $remote_cols    = $rel->{remote_columns} || [ $remote_obj->primary_columns ];

        my $local_cols     = $rel->{local_columns};

        if($#$local_cols != $#$remote_cols) {
            croak "Column count mismatch: $local_moniker (@$local_cols) "
                . "$remote_moniker (@$remote_cols)";
        }

        my %cond;
        foreach my $i (0 .. $#$local_cols) {
            $cond{$remote_cols->[$i]} = $local_cols->[$i];
        }

        my ( $local_relname, $remote_relname, $remote_method ) =
            $self->_relnames_and_method( $local_moniker, $rel, \%cond,  $uniqs, \%counters );

        $remote_relname = $self->_resolve_relname_collision($local_moniker,  $local_cols,  $remote_relname);
        $local_relname  = $self->_resolve_relname_collision($remote_moniker, $remote_cols, $local_relname);

        push(@{$all_code->{$local_class}},
            { method => 'belongs_to',
              args => [ $remote_relname,
                        $remote_class,
                        \%cond,
                        $self->_remote_attrs($local_moniker, $local_cols),
              ],
            }
        );

        my %rev_cond = reverse %cond;
        for (keys %rev_cond) {
            $rev_cond{"foreign.$_"} = "self.".$rev_cond{$_};
            delete $rev_cond{$_};
        }

        push(@{$all_code->{$remote_class}},
            { method => $remote_method,
              args => [ $local_relname,
                        $local_class,
                        \%rev_cond,
			$self->_relationship_attrs($remote_method),
              ],
            }
        );
    }

    return $all_code;
}

sub _relnames_and_method {
    my ( $self, $local_moniker, $rel, $cond, $uniqs, $counters ) = @_;

    my $remote_moniker = $rel->{remote_source};
    my $remote_obj     = $self->schema->source( $remote_moniker );
    my $remote_class   = $self->schema->class(  $remote_moniker );
    my $remote_relname = $self->_remote_relname( $remote_obj->from, $cond);

    my $local_cols     = $rel->{local_columns};
    my $local_table    = $self->schema->source($local_moniker)->from;
    my $local_class    = $self->schema->class($local_moniker);
    my $local_source   = $self->schema->source($local_moniker);

    my $local_relname_uninflected = $self->_normalize_name($local_table);
    my $local_relname = $self->_inflect_plural($self->_normalize_name($local_table));

    my $remote_method = 'has_many';

    # If the local columns have a UNIQUE constraint, this is a one-to-one rel
    if ($self->_array_eq([ $local_source->primary_columns ], $local_cols) ||
            grep { $self->_array_eq($_->[1], $local_cols) } @$uniqs) {
        $remote_method = 'might_have';
        $local_relname = $self->_inflect_singular($local_relname_uninflected);
    }

    # If more than one rel between this pair of tables, use the local
    # col names to distinguish, unless the rel was created previously.
    if ($counters->{$remote_moniker} > 1) {
        my $relationship_exists = 0;

        if (-f (my $existing_remote_file = $self->base->get_dump_filename($remote_class))) {
            my $class = "${remote_class}Temporary";

            if (not Class::Inspector->loaded($class)) {
                my $code = slurp $existing_remote_file;

                $code =~ s/(?<=package $remote_class)/Temporary/g;

                $code =~ s/__PACKAGE__->meta->make_immutable[^;]*;//g;

                eval $code;
                die $@ if $@;

                push @{ $self->_temp_classes }, $class;
            }

            if ($class->has_relationship($local_relname)) {
                my $rel_cols = [ sort { $a cmp $b } apply { s/^foreign\.//i }
                    (keys %{ $class->relationship_info($local_relname)->{cond} }) ];

                $relationship_exists = 1 if $self->_array_eq([ sort @$local_cols ], $rel_cols);
            }
        }

        if (not $relationship_exists) {
            my $colnames = q{_} . $self->_normalize_name(join '_', @$local_cols);
            $remote_relname .= $colnames if keys %$cond > 1;

            $local_relname = $self->_normalize_name($local_table . $colnames);
            $local_relname =~ s/_id$//;

            $local_relname_uninflected = $local_relname;
            $local_relname = $self->_inflect_plural($local_relname);

            # if colnames were added and this is a might_have, re-inflect
            if ($remote_method eq 'might_have') {
                $local_relname = $self->_inflect_singular($local_relname_uninflected);
            }
        }
    }

    return ( $local_relname, $remote_relname, $remote_method );
}

sub cleanup {
    my $self = shift;

    for my $class (@{ $self->_temp_classes }) {
        Class::Unload->unload($class);
    }

    $self->_temp_classes([]);
}

1;
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