Applied patch from Ryan to uniqify index names sanely for the mysql producer

[dbsrgits/SQL-Translator.git] / lib / SQL / Translator / Utils.pm

package SQL::Translator::Utils;

# ----------------------------------------------------------------------
# $Id: Utils.pm,v 1.12 2004-02-09 23:04:26 kycl4rk Exp $
# ----------------------------------------------------------------------
# Copyright (C) 2002-4 SQLFairy Authors
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation; version 2.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
# 02111-1307  USA
# -------------------------------------------------------------------

use strict;
use base qw(Exporter);
use vars qw($VERSION $DEFAULT_COMMENT @EXPORT_OK);

use Digest::SHA1 qw( sha1_hex );

use Exporter;

$VERSION = sprintf "%d.%02d", q$Revision: 1.12 $ =~ /(\d+)\.(\d+)/;
$DEFAULT_COMMENT = '-- ';
@EXPORT_OK = qw(
    debug normalize_name header_comment parse_list_arg truncate_id_uniquely $DEFAULT_COMMENT
);

# ----------------------------------------------------------------------
# debug(@msg)
#
# Will send debugging messages to STDERR, if the caller's $DEBUG global
# is set.
#
# This debug() function has a neat feature: Occurances of the strings
# PKG, LINE, and SUB in each message will be replaced with elements
# from caller():
#
#   debug("PKG: Bad things happened on line LINE!");
#
# Will be warned as:
#
#   [SQL::Translator: Bad things happened on line 643]
#
# If called from Translator.pm, on line 643.
# ----------------------------------------------------------------------
sub debug {
    my ($pkg, $file, $line, $sub) = caller(0);
    {
        no strict qw(refs);
        return unless ${"$pkg\::DEBUG"};
    }

    $sub =~ s/^$pkg\:://;

    while (@_) {
        my $x = shift;
        chomp $x;
        $x =~ s/\bPKG\b/$pkg/g;
        $x =~ s/\bLINE\b/$line/g;
        $x =~ s/\bSUB\b/$sub/g;
        #warn '[' . $x . "]\n";
        print STDERR '[' . $x . "]\n";
    }
}

# ----------------------------------------------------------------------
sub normalize_name {
    my $name = shift or return '';

    # The name can only begin with a-zA-Z_; if there's anything
    # else, prefix with _
    $name =~ s/^([^a-zA-Z_])/_$1/;

    # anything other than a-zA-Z0-9_ in the non-first position
    # needs to be turned into _
    $name =~ tr/[a-zA-Z0-9_]/_/c;

    # All duplicated _ need to be squashed into one.
    $name =~ tr/_/_/s;

    # Trim a trailing _
    $name =~ s/_$//;

    return $name;
}

# ----------------------------------------------------------------------
sub header_comment {
    my $producer = shift || caller;
    my $comment_char = shift;
    my $now = scalar localtime;

    $comment_char = $DEFAULT_COMMENT
        unless defined $comment_char;

    my $header_comment =<<"HEADER_COMMENT";
${comment_char}
${comment_char}Created by $producer
${comment_char}Created on $now
${comment_char}
HEADER_COMMENT

    # Any additional stuff passed in
    for my $additional_comment (@_) {
        $header_comment .= "${comment_char}${additional_comment}\n";
    }

    return $header_comment;
}

# ----------------------------------------------------------------------
# parse_list_arg
#
# Meant to accept a list, an array reference, or a string of 
# comma-separated values.  Retuns an array reference of the 
# arguments.  Modified to also handle a list of references.
# ----------------------------------------------------------------------
sub parse_list_arg {
    my $list = UNIVERSAL::isa( $_[0], 'ARRAY' ) ? shift : [ @_ ];

    #
    # This protects stringification of references.
    #
    if ( @$list && ref $list->[0] ) {
        return $list;
    }
    #
    # This processes string-like arguments.
    #
    else {
        return [ 
            map { s/^\s+|\s+$//g; $_ }
            map { split /,/ }
            grep { defined && length } @$list
        ];
    }
}

# ----------------------------------------------------------------------
# truncate_id_uniquely( $desired_name, $max_symbol_length )
#
# Truncates the name $desired_name to the $max_symbol_length by
# including part of the hash of the full name at the end of the
# truncated name, giving a high probability that the symbol will be
# unique.
# ----------------------------------------------------------------------
my $COLLISION_TAG_LENGTH = 8;
sub truncate_id_uniquely {
    my ( $desired_name, $max_symbol_length ) = @_;

    return $desired_name unless defined $desired_name && length $desired_name > $max_symbol_length;

    my $truncated_name = substr $desired_name, 0, $max_symbol_length - $COLLISION_TAG_LENGTH - 1;

    # Hex isn't the most space-efficient, but it skirts around allowed
    # charset issues
    my $digest = sha1_hex($desired_name);
    my $collision_tag = substr $digest, 0, $COLLISION_TAG_LENGTH;

    return $truncated_name
         . '_'
         . $collision_tag;
}

1;

# ----------------------------------------------------------------------

=pod

=head1 NAME

SQL::Translator::Utils - SQL::Translator Utility functions

=head1 SYNOPSIS

  use SQL::Translator::Utils qw(debug);
  debug("PKG: Bad things happened");

=head1 DESCSIPTION

C<SQL::Translator::Utils> contains utility functions designed to be
used from the other modules within the C<SQL::Translator> modules.

Nothing is exported by default.

=head1 EXPORTED FUNCTIONS AND CONSTANTS

=head2 debug

C<debug> takes 0 or more messages, which will be sent to STDERR using
C<warn>.  Occurances of the strings I<PKG>, I<SUB>, and I<LINE>
will be replaced by the calling package, subroutine, and line number,
respectively, as reported by C<caller(1)>.

For example, from within C<foo> in F<SQL/Translator.pm>, at line 666:

  debug("PKG: Error reading file at SUB/LINE");

Will warn

  [SQL::Translator: Error reading file at foo/666]

The entire message is enclosed within C<[> and C<]> for visual clarity
when STDERR is intermixed with STDOUT.

=head2 normalize_name

C<normalize_name> takes a string and ensures that it is suitable for
use as an identifier.  This means: ensure that it starts with a letter
or underscore, and that the rest of the string consists of only
letters, numbers, and underscores.  A string that begins with
something other than [a-zA-Z] will be prefixer with an underscore, and
all other characters in the string will be replaced with underscores.
Finally, a trailing underscore will be removed, because that's ugly.

  normalize_name("Hello, world");

Produces:

  Hello_world

A more useful example, from the C<SQL::Translator::Parser::Excel> test
suite:

  normalize_name("silly field (with random characters)");

returns:

  silly_field_with_random_characters

=head2 header_comment

Create the header comment.  Takes 1 mandatory argument (the producer
classname), an optional comment character (defaults to $DEFAULT_COMMENT),
and 0 or more additional comments, which will be appended to the header,
prefixed with the comment character.  If additional comments are provided,
then a comment string must be provided ($DEFAULT_COMMENT is exported for
this use).  For example, this:

  package My::Producer;

  use SQL::Translator::Utils qw(header_comment $DEFAULT_COMMENT);

  print header_comment(__PACKAGE__,
                       $DEFAULT_COMMENT,
                       "Hi mom!");

produces:

  --
  -- Created by My::Prodcuer
  -- Created on Fri Apr 25 06:56:02 2003
  --
  -- Hi mom!
  --

Note the gratuitous spacing.

=head2 parse_list_arg

Takes a string, list or arrayref (all of which could contain
comma-separated values) and returns an array reference of the values.
All of the following will return equivalent values:

  parse_list_arg('id');
  parse_list_arg('id', 'name');
  parse_list_arg( 'id, name' );
  parse_list_arg( [ 'id', 'name' ] );
  parse_list_arg( qw[ id name ] );

=head2 truncate_id_uniquely

Takes a string ($desired_name) and int ($max_symbol_length). Truncates
$desired_name to $max_symbol_length by including part of the hash of
the full name at the end of the truncated name, giving a high
probability that the symbol will be unique. For example,

  truncate_id_uniquely( 'a' x 100, 64 )
  truncate_id_uniquely( 'a' x 99 . 'b', 64 );
  truncate_id_uniquely( 'a' x 99,  64 )

Will give three different results; specifically:

  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_7f900025
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_6191e39a
  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_8cd96af2

=head2 $DEFAULT_COMMENT

This is the default comment string, '-- ' by default.  Useful for
C<header_comment>.

=head1 AUTHORS

Darren Chamberlain E<lt>darren@cpan.orgE<gt>,
Ken Y. Clark E<lt>kclark@cpan.orgE<gt>.

=cut

=cut