[dbsrgits/DBIx-Class-Schema-Loader.git] / lib / DBIx / Class / Schema / Loader / RelBuilder.pm

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 DBIx::Class::Schema::Loader::Utils qw/split_name slurp_file array_eq/;
use Try::Tiny;
use List::Util 'first';
use List::MoreUtils qw/apply uniq any/;
use namespace::clean;
use Lingua::EN::Inflect::Phrase ();
use Lingua::EN::Tagger ();
use String::ToIdentifier::EN ();
use String::ToIdentifier::EN::Unicode ();
use Class::Unload ();
use Class::Inspector ();

our $VERSION = '0.07034_02';

# 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

=head1 NAME

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

=head1 SYNOPSIS

See L<DBIx::Class::Schema::Loader> and L<DBIx::Class::Schema::Loader::Base>.

=head1 DESCRIPTION

This class builds relationships for L<DBIx::Class::Schema::Loader>.  This
is module is not (yet) for external use.

=head1 METHODS

=head2 new

Arguments: $loader object

=head2 generate_code

Arguments:

    [
        [ local_moniker1 (scalar), fk_info1 (arrayref), uniq_info1 (arrayref) ]
        [ local_moniker2 (scalar), fk_info2 (arrayref), uniq_info2 (arrayref) ]
        ...
    ]

This generates the code for the relationships of each table.

C<local_moniker> is the moniker name of the table which had the REFERENCES
statements.  The fk_info arrayref's contents should take the form:

    [
        {
            local_table    => 'some_table',
            local_moniker  => 'SomeTable',
            local_columns  => [ 'col2', 'col3' ],
            remote_table   => 'another_table_moniker',
            remote_moniker => 'AnotherTableMoniker',
            remote_columns => [ 'col5', 'col7' ],
        },
        {
            local_table    => 'some_other_table',
            local_moniker  => 'SomeOtherTable',
            local_columns  => [ 'col1', 'col4' ],
            remote_table   => 'yet_another_table_moniker',
            remote_moniker => 'YetAnotherTableMoniker',
            remote_columns => [ 'col1', 'col2' ],
        },
        # ...
    ],

The uniq_info arrayref's contents should take the form:

    [
        [
            uniq_constraint_name         => [ 'col1', 'col2' ],
        ],
        [
            another_uniq_constraint_name => [ 'col1', 'col2' ],
        ],
    ],

This method will return the generated relationships as a hashref keyed on the
class names.  The values are arrayrefs of hashes containing method name and
arguments, like so:

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

=cut

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

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

    # 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 = {
        loader             => $loader,
        schema             => $loader->schema,
        inflect_plural     => $loader->inflect_plural,
        inflect_singular   => $loader->inflect_singular,
        relationship_attrs => $loader->relationship_attrs,
        rel_collision_map  => $loader->rel_collision_map,
        rel_name_map       => $loader->rel_name_map,
        _temp_classes      => [],
    };

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

    bless $self => $class;

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

    return $self;
}


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

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

    my $result;
    my $mapped = 0;

    if( ref $self->inflect_plural eq 'HASH' ) {
        if (exists $self->inflect_plural->{$relname}) {
            $result = $self->inflect_plural->{$relname};
            $mapped = 1;
        }
    }
    elsif( ref $self->inflect_plural eq 'CODE' ) {
        my $inflected = $self->inflect_plural->($relname);
        if ($inflected) {
            $result = $inflected;
            $mapped = 1;
        }
    }

    return ($result, $mapped) if $mapped;

    return ($self->_to_PL($relname), 0);
}

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

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

    my $result;
    my $mapped = 0;

    if( ref $self->inflect_singular eq 'HASH' ) {
        if (exists $self->inflect_singular->{$relname}) {
            $result = $self->inflect_singular->{$relname};
            $mapped = 1;
        }
    }
    elsif( ref $self->inflect_singular eq 'CODE' ) {
        my $inflected = $self->inflect_singular->($relname);
        if ($inflected) {
            $result = $inflected;
            $mapped = 1;
        }
    }

    return ($result, $mapped) if $mapped;

    return ($self->_to_S($relname), 0);
}

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. takes
# the relationship type name and optionally any attributes from the database
# (such as FK ON DELETE/UPDATE and DEFERRABLE clauses), and returns a
# hashref or undef if nothing is set.
#
# The attributes from the database override the default attributes, which in
# turn are overridden by user supplied attributes.
sub _relationship_attrs {
    my ( $self, $reltype, $db_attrs, $params ) = @_;
    my $r = $self->relationship_attrs;

    my %composite = (
        %{ $self->_default_relationship_attrs->{$reltype} || {} },
        %{ $db_attrs || {} },
        (
            ref $r eq 'HASH' ? (
                %{ $r->{all} || {} },
                %{ $r->{$reltype} || {} },
            )
            :
            ()
        ),
    );

    if (ref $r eq 'CODE') {
        $params->{attrs} = \%composite;

        my %ret = %{ $r->(%$params) || {} };

        %composite = %ret if %ret;
    }

    return %composite ? \%composite : undef;
}

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

    $name =~ s/_?(?:id|ref|cd|code|num)\z//i;

    return $name;
}

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

    # get our set of attrs from _relationship_attrs, which uses the FK attrs if available
    my $attrs = $self->_relationship_attrs('belongs_to', $fk_attrs, $params) || {};

    # If any referring column is nullable, make 'belongs_to' an
    # outer join, unless explicitly set by relationship_attrs
    my $nullable = first { $self->schema->source($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) = @_;

    $name = $self->loader->_to_identifier('relationships', $name, '_');

    $name =~ s/\W+/_/g; # if naming >= 8 to_identifier takes care of it

    return $name;
}

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

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

    my @words = split_name $name, $self->loader->_get_naming_v('relationships');

    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 = $self->_strip_id_postfix($self->_normalize_name($col));
        ($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

    my $table = $self->loader->moniker_to_table->{$moniker};

    if ($self->loader->_is_result_class_method($relname, $table)) {
        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->loader->_is_result_class_method($new_relname, $table)) {
            $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, $tables) = @_;

    # make a copy to destroy
    my @tables = @$tables;

    my $all_code = {};

    while (my ($local_moniker, $rels, $uniqs) = @{ shift @tables || [] }) {
        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 );
            my $local_method  = 'belongs_to';

            ($remote_relname) = $self->_rel_name_map($remote_relname, $local_method, $local_class, $local_moniker, $local_cols, $remote_class, $remote_moniker, $remote_cols);
            ($local_relname)  = $self->_rel_name_map($local_relname, $remote_method, $remote_class, $remote_moniker, $remote_cols, $local_class, $local_moniker, $local_cols);

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

            my $rel_attrs_params = {
                rel_name      => $remote_relname,
                rel_type      => $local_method,
                local_source  => $self->schema->source($local_moniker),
                remote_source => $self->schema->source($remote_moniker),
                local_table   => $rel->{local_table},
                local_cols    => $local_cols,
                remote_table  => $rel->{remote_table},
                remote_cols   => $remote_cols,
            };

            push(@{$all_code->{$local_class}},
                { method => $local_method,
                  args => [ $remote_relname,
                            $remote_class,
                            \%cond,
                            $self->_remote_attrs($local_moniker, $local_cols, $rel->{attrs}, $rel_attrs_params),
                  ],
                  extra => {
                      local_class    => $local_class,
                      local_moniker  => $local_moniker,
                      remote_moniker => $remote_moniker,
                  },
                }
            );

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

            $rel_attrs_params = {
                rel_name      => $local_relname,
                rel_type      => $remote_method,
                local_source  => $self->schema->source($remote_moniker),
                remote_source => $self->schema->source($local_moniker),
                local_table   => $rel->{remote_table},
                local_cols    => $remote_cols,
                remote_table  => $rel->{local_table},
                remote_cols   => $local_cols,
            };

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

    $self->_generate_m2ms($all_code);

    # disambiguate rels with the same name
    foreach my $class (keys %$all_code) {
        my $dups = $self->_duplicates($all_code->{$class});

        $self->_disambiguate($all_code, $class, $dups) if $dups;
    }

    $self->_cleanup;

    return $all_code;
}

# Find classes with only 2 FKs which are the PK and make many_to_many bridges for them.
sub _generate_m2ms {
    my ($self, $all_code) = @_;

    while (my ($class, $rels) = each %$all_code) {
        next unless (grep $_->{method} eq 'belongs_to', @$rels) == 2;

        my $class1_local_moniker  = $rels->[0]{extra}{remote_moniker};
        my $class1_remote_moniker = $rels->[1]{extra}{remote_moniker};

        my $class2_local_moniker  = $rels->[1]{extra}{remote_moniker};
        my $class2_remote_moniker = $rels->[0]{extra}{remote_moniker};

        my $class1 = $rels->[0]{args}[1];
        my $class2 = $rels->[1]{args}[1];

        my $class1_to_link_table_rel = first {
            $_->{method} eq 'has_many' && $_->{args}[1] eq $class
        } @{ $all_code->{$class1} };

        my $class1_to_link_table_rel_name = $class1_to_link_table_rel->{args}[0];

        my $class2_to_link_table_rel = first {
            $_->{method} eq 'has_many' && $_->{args}[1] eq $class
        } @{ $all_code->{$class2} };

        my $class2_to_link_table_rel_name = $class2_to_link_table_rel->{args}[0];

        my $class1_link_rel = $rels->[1]{args}[0];
        my $class2_link_rel = $rels->[0]{args}[0];

        my @class1_from_cols = apply { s/^self\.//i } values %{
            $class1_to_link_table_rel->{args}[2]
        };

        my @class1_link_cols = apply { s/^self\.//i } values %{ $rels->[1]{args}[2] };

        my @class1_to_cols = apply { s/^foreign\.//i } keys %{ $rels->[1]{args}[2] };

        my @class2_from_cols = apply { s/^self\.//i } values %{
            $class2_to_link_table_rel->{args}[2]
        };

        my @class2_link_cols = apply { s/^self\.//i } values %{ $rels->[0]{args}[2] };

        my @class2_to_cols = apply { s/^foreign\.//i } keys %{ $rels->[0]{args}[2] };

        my $link_moniker = $rels->[0]{extra}{local_moniker};

        my @link_table_cols =
            @{[ $self->schema->source($link_moniker)->columns ]};

        my @link_table_primary_cols =
            @{[ $self->schema->source($link_moniker)->primary_columns ]};

        next unless @class1_link_cols + @class2_link_cols == @link_table_cols
            && @link_table_cols == @link_table_primary_cols;

        my ($class1_to_class2_relname) = $self->_rel_name_map(
            ($self->_inflect_plural($class1_link_rel))[0],
            'many_to_many',
            $class1,
            $class1_local_moniker,
            \@class1_from_cols,
            $class2,
            $class1_remote_moniker,
            \@class1_to_cols,
            {
                link_class => $class,
                link_moniker => $link_moniker,
                link_rel_name => $class1_to_link_table_rel_name,
            },
        );

        $class1_to_class2_relname = $self->_resolve_relname_collision(
            $class1_local_moniker,
            \@class1_from_cols,
            $class1_to_class2_relname,
        );

        my ($class2_to_class1_relname) = $self->_rel_name_map(
            ($self->_inflect_plural($class2_link_rel))[0],
            'many_to_many',
            $class1,
            $class2_local_moniker,
            \@class2_from_cols,
            $class2,
            $class2_remote_moniker,
            \@class2_to_cols,
            {
                link_class => $class,
                link_moniker => $link_moniker,
                link_rel_name => $class2_to_link_table_rel_name,
            },
        );

        $class2_to_class1_relname = $self->_resolve_relname_collision(
            $class2_local_moniker,
            \@class2_from_cols,
            $class2_to_class1_relname,
        );

        push @{$all_code->{$class1}}, {
            method => 'many_to_many',
            args   => [
                $class1_to_class2_relname,
                $class1_to_link_table_rel_name,
                $class1_link_rel,
            ],
            extra  => {
                local_class    => $class1,
                link_class     => $class,
                local_moniker  => $class1_local_moniker,
                remote_moniker => $class1_remote_moniker,
            },
        };

        push @{$all_code->{$class2}}, {
            method => 'many_to_many',
            args   => [
                $class2_to_class1_relname,
                $class2_to_link_table_rel_name,
                $class2_link_rel,
            ],
            extra  => {
                local_class    => $class2,
                link_class     => $class,
                local_moniker  => $class2_local_moniker,
                remote_moniker => $class2_remote_moniker,
            },
        };
    }
}

sub _duplicates {
    my ($self, $rels) = @_;

    my @rels = map [ $_->{args}[0] => $_ ], @$rels;
    my %rel_names;
    $rel_names{$_}++ foreach map $_->[0], @rels;

    my @dups = grep $rel_names{$_} > 1, keys %rel_names;

    my %dups;

    foreach my $dup (@dups) {
        $dups{$dup} = [ map $_->[1], grep { $_->[0] eq $dup } @rels ];
    }

    return if not %dups;

    return \%dups;
}

sub _tagger {
    my $self = shift;

    $self->__tagger(Lingua::EN::Tagger->new) unless $self->__tagger;

    return $self->__tagger;
}

sub _adjectives {
    my ($self, @cols) = @_;

    my @adjectives;

    foreach my $col (@cols) {
        my @words = split_name $col;

        my $tagged = $self->_tagger->get_readable(join ' ', @words);

        push @adjectives, $tagged =~ m{\G(\w+)/JJ\s+}g;
    }

    return @adjectives;
}

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

    my $to_identifier = $self->loader->naming->{force_ascii} ?
        \&String::ToIdentifier::EN::to_identifier
        : \&String::ToIdentifier::EN::Unicode::to_identifier;

    return join '_', map lc, split_name $to_identifier->($name, '_');
}

sub _disambiguate {
    my ($self, $all_code, $in_class, $dups) = @_;

    DUP: foreach my $dup (keys %$dups) {
        my @rels = @{ $dups->{$dup} };

        # Check if there are rels to the same table name in different
        # schemas/databases, if so qualify them.
        my @tables = map $self->loader->moniker_to_table->{$_->{extra}{remote_moniker}},
                        @rels;

        # databases are different, prepend database
        if ($tables[0]->can('database') && (uniq map $_->database||'', @tables) > 1) {
            # If any rels are in the same database, we have to distinguish by
            # both schema and database.
            my %db_counts;
            $db_counts{$_}++ for map $_->database, @tables;
            my $use_schema = any { $_ > 1 } values %db_counts;

            foreach my $i (0..$#rels) {
                my $rel   = $rels[$i];
                my $table = $tables[$i];

                $rel->{args}[0] = $self->_name_to_identifier($table->database)
                    . ($use_schema ? ('_' . $self->name_to_identifier($table->schema)) : '')
                    . '_' . $rel->{args}[0];
            }
            next DUP;
        }
        # schemas are different, prepend schema
        elsif ((uniq map $_->schema||'', @tables) > 1) {
            foreach my $i (0..$#rels) {
                my $rel   = $rels[$i];
                my $table = $tables[$i];

                $rel->{args}[0] = $self->_name_to_identifier($table->schema)
                    . '_' . $rel->{args}[0];
            }
            next DUP;
        }

        foreach my $rel (@rels) {
            next if $rel->{method} =~ /^(?:belongs_to|many_to_many)\z/;

            my @to_cols = apply { s/^foreign\.//i }
                keys %{ $rel->{args}[2] };

            my @adjectives = $self->_adjectives(@to_cols);

            # If there are no adjectives, and there is only one might_have
            # rel to that class, we hardcode 'active'.

            my $to_class = $rel->{args}[1];

            if ((not @adjectives)
                && (grep { $_->{method} eq 'might_have'
                           && $_->{args}[1] eq $to_class } @{ $all_code->{$in_class} }) == 1) {

                @adjectives = 'active';
            }

            if (@adjectives) {
                my $rel_name = join '_', sort(@adjectives), $rel->{args}[0];

                ($rel_name) = $rel->{method} eq 'might_have' ?
                    $self->_inflect_singular($rel_name)
                    :
                    $self->_inflect_plural($rel_name);

                my ($local_class, $local_moniker, $remote_moniker)
                    = @{ $rel->{extra} }
                        {qw/local_class local_moniker remote_moniker/};

                my @from_cols = apply { s/^self\.//i }
                    values %{ $rel->{args}[2] };

                ($rel_name) = $self->_rel_name_map($rel_name, $rel->{method}, $local_class, $local_moniker, \@from_cols, $to_class, $remote_moniker, \@to_cols);

                $rel_name = $self->_resolve_relname_collision($local_moniker, \@from_cols, $rel_name);

                $rel->{args}[0] = $rel_name;
            }
        }
    }

    # Check again for duplicates, since the heuristics above may not have resolved them all.

    if ($dups = $self->_duplicates($all_code->{$in_class})) {
        foreach my $dup (keys %$dups) {
            # sort by method
            my @rels = map $_->[1], sort { $a->[0] <=> $b->[0] } map [
                {
                    belongs_to   => 3,
                    has_many     => 2,
                    might_have   => 1,
                    many_to_many => 0,
                }->{$_->{method}}, $_
            ], @{ $dups->{$dup} };

            my $rel_num = 2;

            foreach my $rel (@rels[1 .. $#rels]) {
                my $inflect_type = $rel->{method} =~ /^(?:many_to_many|has_many)\z/ ?
                    'inflect_plural'
                    :
                    'inflect_singular';

                my $inflect_method = "_$inflect_type";

                my $relname_new_uninflected = $rel->{args}[0] . "_$rel_num";

                $rel_num++;

                my ($local_class, $local_moniker, $remote_moniker)
                    = @{ $rel->{extra} }
                        {qw/local_class local_moniker remote_moniker/};

                my (@from_cols, @to_cols, $to_class);

                if ($rel->{method} eq 'many_to_many') {
                    @from_cols = apply { s/^self\.//i } values %{
                        (first { $_->{args}[0] eq $rel->{args}[1] } @{ $all_code->{$local_class} })
                            ->{args}[2]
                    };
                    @to_cols   = apply { s/^foreign\.//i } keys %{
                        (first { $_->{args}[0] eq $rel->{args}[2] }
                            @{ $all_code->{ $rel->{extra}{link_class} } })
                                ->{args}[2]
                    };
                    $to_class  = $self->schema->source($remote_moniker)->result_class;
                }
                else {
                    @from_cols = apply { s/^self\.//i }    values %{ $rel->{args}[2] };
                    @to_cols   = apply { s/^foreign\.//i } keys   %{ $rel->{args}[2] };
                    $to_class  = $rel->{args}[1];
                }

                my ($relname_new, $inflect_mapped) =
                    $self->$inflect_method($relname_new_uninflected);

                my $rel_name_mapped;

                ($relname_new, $rel_name_mapped) = $self->_rel_name_map($relname_new, $rel->{method}, $local_class, $local_moniker, \@from_cols, $to_class, $remote_moniker, \@to_cols);

                my $mapped = $inflect_mapped || $rel_name_mapped;

                warn <<"EOF" unless $mapped;
Could not find a proper name for relationship '$relname_new' in source
'$local_moniker' for columns '@{[ join ',', @from_cols ]}'. Supply a value in
'$inflect_type' for '$relname_new_uninflected' or 'rel_name_map' for
'$relname_new' to name this relationship.
EOF

                $relname_new = $self->_resolve_relname_collision($local_moniker, \@from_cols, $relname_new);

                $rel->{args}[0] = $relname_new;
            }
        }
    }
}

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( $rel->{remote_table}, $cond);

    my $local_cols      = $rel->{local_columns};
    my $local_table     = $rel->{local_table};
    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 (array_eq([ $local_source->primary_columns ], $local_cols) ||
            first { array_eq($_->[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 = $self->loader->get_dump_filename($remote_class))) {
            my $class = "${remote_class}Temporary";

            if (not Class::Inspector->loaded($class)) {
                my $code = slurp_file $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} }) ];

                $relationship_exists = 1 if array_eq([ sort @$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 = $self->_strip_id_postfix($self->_normalize_name($local_table . $colnames));

            $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 _rel_name_map {
    my ($self, $relname, $method, $local_class, $local_moniker, $local_cols,
        $remote_class, $remote_moniker, $remote_cols, $extra) = @_;

    my $info = {
        %{$extra || {}},
        name           => $relname,
        type           => $method,
        local_class    => $local_class,
        local_moniker  => $local_moniker,
        local_columns  => $local_cols,
        remote_class   => $remote_class,
        remote_moniker => $remote_moniker,
        remote_columns => $remote_cols,
    };

    my $new_name = $relname;

    my $map = $self->rel_name_map;
    my $mapped = 0;

    if ('HASH' eq ref($map)) {
        my $name = $info->{name};
        my $moniker = $info->{local_moniker};
        if ($map->{$moniker} and 'HASH' eq ref($map->{$moniker})
            and $map->{$moniker}{$name}
        ) {
            $new_name = $map->{$moniker}{$name};
            $mapped   = 1;
        }
        elsif ($map->{$name} and not 'HASH' eq ref($map->{$name})) {
            $new_name = $map->{$name};
            $mapped   = 1;
        }
    }
    elsif ('CODE' eq ref($map)) {
        my $name = $map->($info);
        if ($name) {
            $new_name = $name;
            $mapped   = 1;
        }
    }

    return ($new_name, $mapped);
}

sub _cleanup {
    my $self = shift;

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

    $self->_temp_classes([]);
}

=head1 AUTHOR

See L<DBIx::Class::Schema::Loader/AUTHOR> and L<DBIx::Class::Schema::Loader/CONTRIBUTORS>.

=head1 LICENSE

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

=cut

1;
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