package Encode::Alias;

use strict;

use warnings;

our $VERSION = do { my @r = ( q$Revision: 2.24 $ =~ /\d+/g ); sprintf "%d." . "%02d" x $#r, @r };

use constant DEBUG => !!$ENV{PERL_ENCODE_DEBUG};

use Exporter 'import';

# Public, encouraged API is exported by default

our @EXPORT =

  qw (

  define_alias

  find_alias

);

our @Alias;    # ordered matching list

our %Alias;    # cached known aliases

sub find_alias {

    my $class = shift;

    my $find  = shift;

    unless ( exists $Alias{$find} ) {

        $Alias{$find} = undef;    # Recursion guard

        for ( my $i = 0 ; $i < @Alias ; $i += 2 ) {

            my $alias = $Alias[$i];

            my $val   = $Alias[ $i + 1 ];

            my $new;

            if ( ref($alias) eq 'Regexp' && $find =~ $alias ) {

                DEBUG and warn "eval $val";

                $new = eval $val;

                DEBUG and $@ and warn "$val, $@";

            }

            elsif ( ref($alias) eq 'CODE' ) {

                DEBUG and warn "$alias", "->", "($find)";

                $new = $alias->($find);

            }

            elsif ( lc($find) eq lc($alias) ) {

                $new = $val;

            }

            if ( defined($new) ) {

                next if $new eq $find;    # avoid (direct) recursion on bugs

                DEBUG and warn "$alias, $new";

                my $enc =

                  ( ref($new) ) ? $new : Encode::find_encoding($new);

                if ($enc) {

                    $Alias{$find} = $enc;

                    last;

                }

            }

        }

        # case insensitive search when canonical is not in all lowercase

        # RT ticket #7835

        unless ( $Alias{$find} ) {

            my $lcfind = lc($find);

            for my $name ( keys %Encode::Encoding, keys %Encode::ExtModule )

            {

                $lcfind eq lc($name) or next;

                $Alias{$find} = Encode::find_encoding($name);

                DEBUG and warn "$find => $name";

            }

        }

    }

    if (DEBUG) {

        my $name;

        if ( my $e = $Alias{$find} ) {

            $name = $e->name;

        }

        else {

            $name = "";

        }

        warn "find_alias($class, $find)->name = $name";

    }

    return $Alias{$find};

}

sub define_alias {

    while (@_) {

        my $alias = shift;

        my $name = shift;

        unshift( @Alias, $alias => $name )    # newer one has precedence

            if defined $alias;

        if ( ref($alias) ) {

            # clear %Alias cache to allow overrides

            my @a = keys %Alias;

            for my $k (@a) {

                if ( ref($alias) eq 'Regexp' && $k =~ $alias ) {

                    DEBUG and warn "delete \$Alias\{$k\}";

                    delete $Alias{$k};

                }

                elsif ( ref($alias) eq 'CODE' && $alias->($k) ) {

                    DEBUG and warn "delete \$Alias\{$k\}";

                    delete $Alias{$k};

                }

            }

        }

        elsif (defined $alias) {

            DEBUG and warn "delete \$Alias\{$alias\}";

            delete $Alias{$alias};

        }

        elsif (DEBUG) {

            require Carp;

            Carp::croak("undef \$alias");

        }

    }

}

# HACK: Encode must be used after define_alias is declarated as Encode calls define_alias

use Encode ();

# Allow latin-1 style names as well

# 0  1  2  3  4  5   6   7   8   9  10

our @Latin2iso = ( 0, 1, 2, 3, 4, 9, 10, 13, 14, 15, 16 );

# Allow winlatin1 style names as well

our %Winlatin2cp = (

    'latin1'     => 1252,

    'latin2'     => 1250,

    'cyrillic'   => 1251,

    'greek'      => 1253,

    'turkish'    => 1254,

    'hebrew'     => 1255,

    'arabic'     => 1256,

    'baltic'     => 1257,

    'vietnamese' => 1258,

);

init_aliases();

sub undef_aliases {

    @Alias = ();

    %Alias = ();

}

sub init_aliases {

    undef_aliases();

    # Try all-lower-case version should all else fails

    define_alias( qr/^(.*)$/ => '"\L$1"' );

    # UTF/UCS stuff

    define_alias( qr/^(unicode-1-1-)?UTF-?7$/i     => '"UTF-7"' );

    define_alias( qr/^UCS-?2-?LE$/i => '"UCS-2LE"' );

    define_alias(

        qr/^UCS-?2-?(BE)?$/i    => '"UCS-2BE"',

        qr/^UCS-?4-?(BE|LE|)?$/i => 'uc("UTF-32$1")',

        qr/^iso-10646-1$/i      => '"UCS-2BE"'

    );

    define_alias(

        qr/^UTF-?(16|32)-?BE$/i => '"UTF-$1BE"',

        qr/^UTF-?(16|32)-?LE$/i => '"UTF-$1LE"',

        qr/^UTF-?(16|32)$/i     => '"UTF-$1"',

    );

    # ASCII

    define_alias( qr/^(?:US-?)ascii$/i       => '"ascii"' );

    define_alias( 'C'                        => 'ascii' );

    define_alias( qr/\b(?:ISO[-_]?)?646(?:[-_]?US)?$/i => '"ascii"' );

    # Allow variants of iso-8859-1 etc.

    define_alias( qr/\biso[-_]?(\d+)[-_](\d+)$/i => '"iso-$1-$2"' );

    # At least HP-UX has these.

    define_alias( qr/\biso8859(\d+)$/i => '"iso-8859-$1"' );

    # More HP stuff.

    define_alias(

        qr/\b(?:hp-)?(arabic|greek|hebrew|kana|roman|thai|turkish)8$/i =>

          '"${1}8"' );

    # The Official name of ASCII.

    define_alias( qr/\bANSI[-_]?X3\.4[-_]?1968$/i => '"ascii"' );

    # This is a font issue, not an encoding issue.

    # (The currency symbol of the Latin 1 upper half

    #  has been redefined as the euro symbol.)

    define_alias( qr/^(.+)\@euro$/i => '"$1"' );

    define_alias( qr/\b(?:iso[-_]?)?latin[-_]?(\d+)$/i =>

'defined $Encode::Alias::Latin2iso[$1] ? "iso-8859-$Encode::Alias::Latin2iso[$1]" : undef'

    );

    define_alias(

        qr/\bwin(latin[12]|cyrillic|baltic|greek|turkish|

             hebrew|arabic|baltic|vietnamese)$/ix =>

          '"cp" . $Encode::Alias::Winlatin2cp{lc($1)}'

    );

    # Common names for non-latin preferred MIME names

    define_alias(

        'ascii'    => 'US-ascii',

        'cyrillic' => 'iso-8859-5',

        'arabic'   => 'iso-8859-6',

        'greek'    => 'iso-8859-7',

        'hebrew'   => 'iso-8859-8',

        'thai'     => 'iso-8859-11',

    );

    # RT #20781

    define_alias(qr/\btis-?620\b/i  => '"iso-8859-11"');

    # At least AIX has IBM-NNN (surprisingly...) instead of cpNNN.

    # And Microsoft has their own naming (again, surprisingly).

    # And windows-* is registered in IANA!

    define_alias(

        qr/\b(?:cp|ibm|ms|windows)[-_ ]?(\d{2,4})$/i => '"cp$1"' );

    # Sometimes seen with a leading zero.

    # define_alias( qr/\bcp037\b/i => '"cp37"');

    # Mac Mappings

    # predefined in *.ucm; unneeded

    # define_alias( qr/\bmacIcelandic$/i => '"macIceland"');

    define_alias( qr/^(?:x[_-])?mac[_-](.*)$/i => '"mac$1"' );

    # http://rt.cpan.org/Ticket/Display.html?id=36326

    define_alias( qr/^macintosh$/i => '"MacRoman"' );

    # https://rt.cpan.org/Ticket/Display.html?id=78125

    define_alias( qr/^macce$/i => '"MacCentralEurRoman"' );

    # Ououououou. gone.  They are different!

    # define_alias( qr/\bmacRomanian$/i => '"macRumanian"');

    # Standardize on the dashed versions.

    define_alias( qr/\bkoi8[\s\-_]*([ru])$/i => '"koi8-$1"' );

    unless ($Encode::ON_EBCDIC) {

        # for Encode::CN

        define_alias( qr/\beuc.*cn$/i => '"euc-cn"' );

        define_alias( qr/\bcn.*euc$/i => '"euc-cn"' );

        # define_alias( qr/\bGB[- ]?(\d+)$/i => '"euc-cn"' )

        # CP936 doesn't have vendor-addon for GBK, so they're identical.

        define_alias( qr/^gbk$/i => '"cp936"' );

        # This fixes gb2312 vs. euc-cn confusion, practically

        define_alias( qr/\bGB[-_ ]?2312(?!-?raw)/i => '"euc-cn"' );

        # for Encode::JP

        define_alias( qr/\bjis$/i         => '"7bit-jis"' );

        define_alias( qr/\beuc.*jp$/i     => '"euc-jp"' );

        define_alias( qr/\bjp.*euc$/i     => '"euc-jp"' );

        define_alias( qr/\bujis$/i        => '"euc-jp"' );

        define_alias( qr/\bshift.*jis$/i  => '"shiftjis"' );

        define_alias( qr/\bsjis$/i        => '"shiftjis"' );

        define_alias( qr/\bwindows-31j$/i => '"cp932"' );

        # for Encode::KR

        define_alias( qr/\beuc.*kr$/i => '"euc-kr"' );

        define_alias( qr/\bkr.*euc$/i => '"euc-kr"' );

        # This fixes ksc5601 vs. euc-kr confusion, practically

        define_alias( qr/(?:x-)?uhc$/i         => '"cp949"' );

        define_alias( qr/(?:x-)?windows-949$/i => '"cp949"' );

        define_alias( qr/\bks_c_5601-1987$/i   => '"cp949"' );

        # for Encode::TW

        define_alias( qr/\bbig-?5$/i              => '"big5-eten"' );

        define_alias( qr/\bbig5-?et(?:en)?$/i     => '"big5-eten"' );

        define_alias( qr/\btca[-_]?big5$/i        => '"big5-eten"' );

        define_alias( qr/\bbig5-?hk(?:scs)?$/i    => '"big5-hkscs"' );

        define_alias( qr/\bhk(?:scs)?[-_]?big5$/i => '"big5-hkscs"' );

    }

    # https://github.com/dankogai/p5-encode/issues/37

    define_alias(qr/cp65000/i => '"UTF-7"');

    define_alias(qr/cp65001/i => '"utf-8-strict"');

    # utf8 is blessed :)

    define_alias( qr/\bUTF-8$/i => '"utf-8-strict"' );

    # At last, Map white space and _ to '-'

    define_alias( qr/^([^\s_]+)[\s_]+([^\s_]*)$/i => '"$1-$2"' );

}

1;

__END__

# TODO: HP-UX '8' encodings arabic8 greek8 hebrew8 kana8 thai8 turkish8

# TODO: HP-UX '15' encodings japanese15 korean15 roi15

# TODO: Cyrillic encoding ISO-IR-111 (useful?)

# TODO: Armenian encoding ARMSCII-8

# TODO: Hebrew encoding ISO-8859-8-1

# TODO: Thai encoding TCVN

# TODO: Vietnamese encodings VPS

# TODO: Mac Asian+African encodings: Arabic Armenian Bengali Burmese

#       ChineseSimp ChineseTrad Devanagari Ethiopic ExtArabic

#       Farsi Georgian Gujarati Gurmukhi Hebrew Japanese

#       Kannada Khmer Korean Laotian Malayalam Mongolian

#       Oriya Sinhalese Symbol Tamil Telugu Tibetan Vietnamese

=head1 NAME

Encode::Alias - alias definitions to encodings

=head1 SYNOPSIS

  use Encode;

  use Encode::Alias;

  define_alias( "newName" => ENCODING);

  define_alias( qr/.../ => ENCODING);

  define_alias( sub { return ENCODING if ...; } );

=head1 DESCRIPTION

Allows newName to be used as an alias for ENCODING. ENCODING may be

either the name of an encoding or an encoding object (as described 

in L<Encode>).

Currently the first argument to define_alias() can be specified in the

following ways:

=over 4

=item As a simple string.

=item As a qr// compiled regular expression, e.g.:

  define_alias( qr/^iso8859-(\d+)$/i => '"iso-8859-$1"' );

In this case, if I<ENCODING> is not a reference, it is C<eval>-ed

in order to allow C<$1> etc. to be substituted.  The example is one

way to alias names as used in X11 fonts to the MIME names for the

iso-8859-* family.  Note the double quotes inside the single quotes.

(or, you don't have to do this yourself because this example is predefined)

If you are using a regex here, you have to use the quotes as shown or

it won't work.  Also note that regex handling is tricky even for the

experienced.  Use this feature with caution.

=item As a code reference, e.g.:

  define_alias( sub {shift =~ /^iso8859-(\d+)$/i ? "iso-8859-$1" : undef } );

The same effect as the example above in a different way.  The coderef

takes the alias name as an argument and returns a canonical name on

success or undef if not.  Note the second argument is ignored if provided.

Use this with even more caution than the regex version.

=back

=head3 Changes in code reference aliasing

As of Encode 1.87, the older form

  define_alias( sub { return  /^iso8859-(\d+)$/i ? "iso-8859-$1" : undef } );

no longer works. 

Encode up to 1.86 internally used "local $_" to implement this older

form.  But consider the code below;

  use Encode;

  $_ = "eeeee" ;

  while (/(e)/g) {

    my $utf = decode('aliased-encoding-name', $1);

    print "position:",pos,"\n";

  }

Prior to Encode 1.86 this fails because of "local $_".

=head2 Alias overloading

You can override predefined aliases by simply applying define_alias().

The new alias is always evaluated first, and when necessary,

define_alias() flushes the internal cache to make the new definition

available.

  # redirect SHIFT_JIS to MS/IBM Code Page 932, which is a

  # superset of SHIFT_JIS

  define_alias( qr/shift.*jis$/i  => '"cp932"' );

  define_alias( qr/sjis$/i        => '"cp932"' );

If you want to zap all predefined aliases, you can use

  Encode::Alias->undef_aliases;

to do so.  And

  Encode::Alias->init_aliases;

gets the factory settings back.

Note that define_alias() will not be able to override the canonical name

of encodings. Encodings are first looked up by canonical name before

potential aliases are tried.

=head1 SEE ALSO

L<Encode>, L<Encode::Supported>

=cut