From fbb6d8e00208fa636df12e8e4414ac79f58645d7 Mon Sep 17 00:00:00 2001
From: Jakob Voss <voss@gbv.de>
Date: Mon, 28 Aug 2023 07:38:40 +0200
Subject: [PATCH] Fix parsing plain $$ (#136)

---
 Changes                  |  1 +
 lib/PICA/Parser/Plain.pm | 47 +++++++++++++---------------------------
 t/20-parser.t            |  6 +++++
 3 files changed, 22 insertions(+), 32 deletions(-)

diff --git a/Changes b/Changes
index a7b2ad0..f371f74 100644
--- a/Changes
+++ b/Changes
@@ -1,6 +1,7 @@
 Revision history for PICA::Data
 
 {{$NEXT}}
+    - Fix parsing plain $$ (#136)
 
 2.11 2023-08-18T05:19:26Z
     - Add parser method: all
diff --git a/lib/PICA/Parser/Plain.pm b/lib/PICA/Parser/Plain.pm
index 12778d5..8f1d096 100644
--- a/lib/PICA/Parser/Plain.pm
+++ b/lib/PICA/Parser/Plain.pm
@@ -49,45 +49,28 @@ sub _next_record {
             $occ  = $3;
             $data = $4;
         }
-        elsif ($self->{strict}) {
-            croak "ERROR: invalid PICA field structure \"$field\"";
-        }
-        else {
-            carp
-                "WARNING: invalid PICA field structure \"$field\". Skipped field";
-            next;
-        }
 
         if (!$self->{strict} && $data =~ /^ƒ/) {
             $data =~ s/\$/\$\$/g;
             $data =~ s/ƒ/\$/g;
         }
 
-        my @subfields = split /\$(\$+|.)/, $data;
-        shift @subfields;
-        push @subfields, '' if @subfields % 2;   # last subfield without value
-
-        if ($data =~ /\$\$/) {
-            my @tokens = (shift @subfields, shift @subfields);
-            while (@subfields) {
-                my $code  = shift @subfields;
-                my $value = shift @subfields;
-                if ($code =~ /^\$+$/) {
-                    my $length = length $code;
-                    $code =~ s/\$\$/\$/g;
-                    if ($length % 2) {
-                        $tokens[-1] .= "$code$value";
-                        next;
-                    }
-                    else {
-                        $tokens[-1] .= $code;
-                        $code  = substr $value, 0, 1;
-                        $value = substr $value, 1;
-                    }
-                }
-                push @tokens, $code, $value;
+        if ($data !~ /^(\$[^\$]([^\$]|\$\$)*)+$/) {
+            if ($self->{strict}) {
+                croak "ERROR: invalid PICA field structure \"$field\"";
+            }
+            else {
+                carp
+                    "WARNING: invalid PICA field structure \"$field\". Skipped field";
+                next;
             }
-            @subfields = @tokens;
+        }
+
+        my @subfields;
+        while ($data =~ m/\G\$([^\$])(([^\$]|\$\$)*)/g) {
+            my ($code, $value) = ($1, $2);
+            $value =~ s/\$\$/\$/g;
+            push @subfields, $code, $value;
         }
 
         push @subfields, $annotation if defined $annotation;
diff --git a/t/20-parser.t b/t/20-parser.t
index 6656586..8700aa0 100644
--- a/t/20-parser.t
+++ b/t/20-parser.t
@@ -13,6 +13,8 @@ ok $first->{record}->[0][0] eq '002@', 'tag from first field';
 is_deeply $first->{record}->[1], ['003@', '', 0 => '12345'], 'second field';
 is_deeply $first->{record}->[4], ['012X', '', 0 => '0', x => '', y => ''],
     'empty subfields';
+
+
 is $first->{record}->[6]->[7], '柳经纬主编;', 'Unicode';
 is_deeply $first->{record}->[11],
     ['145Z', '40', 'a', '$', 'b', 'test$', 'c', '...'], 'sub field with $';
@@ -116,6 +118,10 @@ note 'error handling';
     dies_ok {pica_parser(xml => '')} 'invalid handle';
     dies_ok {pica_parser(plus => [])} 'invalid handle';
     dies_ok {pica_parser(plain => bless({}, 'MyFooBar'))} 'invalid handle';
+
+    # https://github.com/gbv/PICA-Data/issues/136
+    $plain = '021A $$';
+    dies_ok {PICA::Parser::Plain->new(\$plain, strict => 1)->next} 'issue 136';
 }
 
 is pica_parser(plain => \'012A/00 $xy')->next->string,